Fill door having angled movement
United States Patent 6729245
A fill door for use on the angled surfaces of furnace shells and chemical containers. The door is pivotally coupled to a door frame integral with the angled surface and includes a rim that mates with a female channel in the door. A U-shaped latch is pivotally connected to the frame and includes a threaded spindle operatively connected to crack. The surface of the door includes a female sleeve having a bore for accommodating the end of the spindle when the latch is over the door and the spindle is tightened into its closed and locked position. The door further includes a cantilevered arm having an angled bore which allows it to swivel around a substantially vertical cylindrical post connected to frame. The arm and door swing in a substantially horizontal plane around the axis of the post.
Inventors:
Clark, Kenneth D. (Santa Rosa, CA)
Application Number:
Publication Date:
05/04/2004
Filing Date:
08/14/2002
Export Citation:
CLARK KENNETH D.
Primary Class:
International Classes:
F23M7/00; F27D1/18; (IPC1-7): F23M7/00
Field of Search:
49/191, 126/175A, 126/177, 126/191, 49/381, 110/173B, 110/175R, 126/192, 220/836, 110/180, 126/176, 110/179, 126/190, 110/174, 110/173R, 110/173A, 220/845, 49/190, 220/810, 126/179, 49/385, 49/255, 110/173C, 220/818, 376/203, 110/181, 49/203, 126/197, 126/194, 126/178
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US Patent References:
5727479Mcafee et al.110/1765158043Emsbo122/4984883002Schuster110/173R4016820Johnson et al.110/173R2271411Thwaits220/371759882Bilty292/2101537093Stoop110/165R0521447N/APickles110/175R0510786N/AHarris110/175R0301155N/AHaumerson110/173R0238411N/ALowell110/181
Primary Examiner:
Rinehart, Kenneth B.
Attorney, Agent or Firm:
Johnson, Larry D.
Stainbrook, Craig M.
Johnson & Stainbrook, LLP
Parent Case Data:
This application claims the benefit of Provisional
application Ser. No. 60/183,497, filed Feb. 17, 2000.
What is claimed as invention is:
1. A fill door for attachment to industrial furnaces and chemical containment vessels, said comprising: a door (16) having a closed position (12) and a fully open position (14); a door frame (18), said frame positioned on an angled surface (20) of a vessel shell (22); a substantially vertical cylindrical pivot post (82) proximate said door, and having an upper half (86) pivotally connected to a lower half (88); and an arm (76) affixed to said door and pivotally connected to said post (82); characterized in that said door moves from its closed position to its fully open position in a horizontal plane.
2. The fill door of claim 1, wherein a bushing (90) is interposed between said upper half (86) and said lower half (88).
3. A fill door for attachment to industrial furnaces and chemical containment vessels, said door comprising: a door (16) having a closed position (12) and a fully open position (14); a door frame (18), said frame positioned on an angled surface (20) of a vessel shell (22); a substantially vertical cylindrical pivot post (82) and an arm (76) affixed to said door and pivotally connected to said post (82), wherein said arm (76) has a tongue portion (97) having an aperture (98) into which a steel housing and ball bearing linkage (100) is inserted and secured, and wherein said linkage mates with a rod (102) integral with the base portion (77) of said sleeve (68), and wherein said arm (76) is interposed between said sleeve (68) and said door (16) such that said tongue portion (97) of arm 76 has a small amount of play underneath sleeve (68), and said ball bearing linkage allows some swiveling and rotational
characterized in that said door moves from its closed position to its fully open position in a horizontal plane.
4. A fill door for attachment to industrial furnaces and chemical containment vessels, said door comprising: a door (16) having a closed position (12) and a fully open position (14); a door frame (18), said frame positioned on an angled surface (20) of a vessel shell (22); a substantially vertical cylindrical pivot post (82) and an arm (76) affixed to said door and pivotally connected to said post (82); a U-shaped bracket latch (30) having a transverse member (32) and two arms (34, 36), each arm pivotally connected to said frame (18) a rotatable threaded spindle (56) threadably inserted through a threaded sleeve (58), which is connected to said transverse member (32); and a female sleeve (68) bolted to the outer surface (70) of door 16 with a plurality of bolts (72) and having a shallow bore (74) for accommodating the end of spindle (56) when the latter is rotated down to secure said latch (30) when said door (16) is in the closed position (12); characterized in that said door moves from its closed position to its fully open position in a horizontal plane.
5. The fill door of claim 4, wherein said female sleeve (68) includes a throat portion (75) and a base portion (77), wherein said throat portion includes said shallow bore (74) and said base portion is bolted to said door (16).
6. The fill door of claim 4 wherein said latch (30) includes an aperture (46, 48) in each of said arms (34, 36), and wherein said frame (18) includes apertures (50) aligned with said apertures (46, 48) in said arms, and wherein said pivotal connection of said latch to said frame is provided by a bushing (38,40) and pin (42, 44) assembly one each inserted into the aligned apertures (46, 48, 50).
7. The fill door of claim 4, further including a crank (60) operatively connected to said spindle 56, said crank comprising a bar (62) and two handles (64, 66).
Description:
BACKGROUND OF THE INVENTION1. Technical FieldThe present invention relates generally to furnace and chemical vessel doors, and more particularly to a fill door having an angled movement.2. Background ArtFurnace and chemical vessel fill doors are frequently set on an angled surface on a furnace or vessel shell. Positioning the door on an angled surface facilitates loading and transferring molten materials and dangerous chemicals. However, this positioning also makes manual movement of heavy doors difficult and occasionally impossible. It has been proposed to provide mechanical means, e.g., hydraulic or pneumatic, to assist in the door movement. This solution is needlessly costly and ultimately impracticable.Furnace door designs generally are generally adapted for side wall positioning and address the need for thermal and gas tight fitting, while preferring mechanical operation. Recent examples include U.S. Pat. No. 4,883,002 to Schuster, which discloses a furnace closing mechanism for industrial furnaces composed of a furnace door latched to the furnace shell and a heat-insulating door fastened to inner side of the furnace door. The door is coupled to the door frame and furnace shell with a bayonet-type joint.U.S. Pat. No. 5,727,479 to McAfee, et al., teaches an improved guillotine-style door closure system for a furnace that comprises an opening on the vertical side of a furnace, and a furnace door adapted to mate with the frame. The apparatus purportedly provides a uniform sealing forces along the entire door frame and prohibits the escape of gases between the seal and further prevents the crushing of ceramic fibers used for lining the doors.The fill door of the present invention represents a solution to the above-described problem. The present invention comprises a center floating door on an angled hinge that allows the door to be opened and closed manually with very little effort and to be sealed after closing.Many furnace designs include angled walls, and due to the advantages of this design it is desirable to fashion liquid-containing vessels similarly. However, to date doors for furnaces and vessels have developed for use on vertical and horizontal surfaces and to provide vertical and horizontal closures. When the door is heavy, because of the need for a thermal and gas tight closure, vertical and horizontal door motions (which require some measure of lifting and holding of the door) can become difficult and necessitate mechanical assistance.Accordingly, there remains a need for a fill door having an angled movement, such that the door can be positioned on an opening on an angled surface while yet providing substantially level horizontal movement of the door.DISCLOSURE OF INVENTIONThe present invention is a fill door adapted for use on the angled surfaces of furnace shells or chemical containers. The door is pivotally coupled to a door frame which is integral with the angled surface. The frame includes a rim surrounding a furnace opening and mates with a female channel in the door. A U-shaped bracket latch is pivotally connected to the frame. The latch includes a threaded spindle operatively connected to a crank. The surface of the door includes a female sleeve which has a bore for accommodating the end of the spindle when the latch is over the door and the spindle is tightened into its closed and locked position. The door further includes a cantilevered arm having an angled bore which allows it to swivel around a substantially vertical cylindrical post connected to frame. The arm and thus the door swings in a substantially horizontal plane (i.e., a plane substantially 90 degrees relative to the axis of the post).BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1A is a perspective view of the fill door having angled movement of the present invention, showing the door in its closed and lFIG. 1B is a perspective view of the present invention showing the door in its unlatchedFIG. 1C is a perspective view of the door of FIGS. 1 and 2, showing thFIG. 1D is a perspective view of the inventive door, showing the door open approximately 90 degrees rFIG. 1E is a perspective view showing tFIG. 2A is left side view in elevation view of the door of FIGS. 1a-e, showing the door in FIG. 2B is a right side view in elevation showing the door in its unlatched, andFIG. 3 is an exploded view of the inventive door showing its assembly and component parts.BEST MODE FOR CARRYING OUT THE INVENTIONReferring to FIGS. 1 through 3, wherein like reference numerals refer to like components in the various views, FIGS. 1A through 1E is a series of perspective views showing the furnace fill door 10 of the present invention in its closed configuration 12 (FIG. 1A), open configuration 14 (FIG. 1E), and further showing the movement of the door from the closed configuration to the open configuration (FIGS. 1B-D). The inventive apparatus comprises a door 16 and a door frame 18, said frame integrally formed and positioned on an angled surface 20 of a furnace shell or vessel 22 (FIGS. 2A-B) and defining an opening 24 providing access to the furnace or vessel interior. The frame 18 includes a male tongue or rim 26 preferably surrounding or substantially surrounding the furnace opening and adapted for precise mating with a female channel or slot 28 in door 16 to form a tongue-and-groove thermal and gas-tight coupling. Preferably the tongue-and-groove connection includes glass or ceramic fiber insulating material to provide a tight thermal and gas seal for furnaces or, alternatively, chemically inert deformable material to provide a seal suitable for use in chemical containment.A U-shaped bracket latch 30 having a transverse member 32 and two arms 34, 36 is pivotally connected to frame 18 with a bushing 38, 40 and pin 42, 44 assembly, said pins and bushings inserted through apertures 46, 48 in the arms of latch 30 and into respective apertures 50 in the lower side 52 and upper side 54 (aperture not shown) of frame 18. The latch further includes a threaded spindle 56 inserted through a threaded sleeve 58, which is connected to transverse member 32, preferably welded, and threadably passes through transverse member 32. Operatively connected to spindle 56 is crank 60, which comprises a bar 62 and two rigid or, preferably, bearing-mounted handles 64, 66.Door 16 includes a female sleeve 68 either integrally connected to the outer surface 70 of door 16 or bolted thereto with a plurality of bolts 72 and having a shallow bore 74 in a throat portion 75 for accommodating the end of spindle 56 when the latter is turned down into its closed position 12, and further having a base portion 77 for connection to door 16, said base portion 75 having a larger diameter than the throat portion 75.The door 16 further includes a cantilevered L-shaped arm 76, preferably, though not necessarily, connected to said door at sleeve 68. At its cantilevered end 78, arm 76 includes an angled through bore 80 which allows the arm 76 to be fitted over and swivel around a cylindrical pivot post 82 proximate the door 16. The angle 79 of the through bore 80 is dictated by the angle of the vessel wall 22, inasmuch as the plane 81 of the arm is parallel to the plane 83 of the vessel wall. The pivot post is disposed substantially vertically from frame 18 and is preferably inserted into an angled aperture 84 in the frame. The pivot post may alternatively be affixed to the vessel wall rather than the door frame, though manufacture is simpler and structural integrity increased by having the post extend from the frame. Preferably pivot post 82 is divided into an upper moving half 86 and a lower stationary half 88, said upper half inserted into said lower half and said halves having a bushing 90 interposed between them so as to allow rotational movement of upper half 86. Alternatively, the angled bore 80 of arm 76 itself permits the arm to swing or swivel about post 82 such that door 16 swings on a substantially horizontal plane 92, i.e., a plane substantially 90 degrees relative to the longitudinal axis 94 of post 82, when moved either to or from its closed position. At the other end 96 of cantilevered arm 76 there is a tongue portion 97 having an aperture 98 into which a steel housing and ball bearing linkage 100 is inserted and secured for mating with a rod 102 integral with the base portion 77 of sleeve 68, such that arm 76 is interposed between sleeve 68 and door 16 before it is secured by bolts 72 threaded into complementary apertures 104 on the door, and such that the tongue portion 97 fits into a slot 106 integrally formed in base portion 77. (The housing and ball bearing linkage is well-known in the art and may be purchased off the shelf from several manufacturers, including F. K. Bearings, Inc., of Southington, Conn., USA.) When assembled, the tongue portion 97 of arm 76 has a small amount of space or play underneath sleeve 68, and the ball bearing linkage allows some swiveling and rotational movement in the door so that perfect tolerances in the assembly need not be achieved in order to provide a tight fit at closure.As illustrated in FIGS. 1A-1E, to open the fill door of the present invention, crank 60 is turned in a counterclockwise direction until spindle 56 is entirely disengaged from sleeve 68. U-shaped bracket latch 30 is then swung over and against the furnace shell and away from the upper surface 70 of door 16. The door is now free to be opened and easily pivots around post 82. These actions are simply reversed to close the door, and complete closure is accomplished when spindle 56 is positioned over sleeve 68 and crank 60 is turned clockwise to thread spindle 56 into bore 74 to provide coupling pressure on the door. As may be readily appreciated, while the door remains angled, an operator positioned on the ground can effectively swing the door open and closed on a single level without the need to lift or hold the door at any point within its range of movement.The configuration of operative structures in the present invention provides a barrier to the migration and transfer of heat from the furnace shell to the handle mechanism. This protects the operator from injury and obviates the need for lengthy cooling periods or mechanical operation.While this invention has been described in connection with preferred embodiments thereof, it is obvious that modifications and changes therein may be made by those skilled in the art to which it pertains without departing from the spirit and scope of the invention. It will be readily appreciated that while the inventive door is particularly well adapted to industrial applications, the present disclosure teaches a closure system suitable for use in any of a number of environments, including, for example, structures requiring human ingress and egress. Thus, many of the elements that provide bulk and sturdiness to the inventive apparatus may either be eliminated altogether or replaced with lightweight counterparts while retaining the level movement accomplished by the combination of the cantilevered arm with the angled through bore and the vertically disposed pivot post. Accordingly, the scope of this invention is to be limited only by the appended claims.
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阿里巴巴中国站和淘宝网会员帐号体系、《阿里巴巴服务条款》升级，完成登录后两边同时登录成功。Axial cam driven valve arrangement for an axial cam driven parallel piston pump system
United States Patent 5733105
A reciprocating piston pump provides pulseless delivery of liquid. It is suitable for use in compact environments or for the delivery of small amounts of liquid, as in chromatographic analysis devices. The pump includes two pistons with pumping chambers that are alternately connected to inflow and outflow lines through a control valve. The control valve moves between a first position in which inflow is directed to the first piston chamber and outflow to the second piston chamber, and a second position in which outflow is directed to the first piston chamber and inflow is directed to the second piston chamber. Each outflow pulse from the piston is sustained longer than each inflow pulse, and the outflow pulses are staggered and partially superimposed to provide substantially pulseless delivery of liquid from the pump. A rotating cam moves the pistons of the pumps and the control valve between their operating positions described above. The cam rotates at a constant speed around an axis that is parallel to the axis of movement of the piston pumps. A control surface is carried by and rotated by the cam in one embodiment. Grooves inscribed in the control surface establish and break fluid connections as the cam rotates.
Inventors:
Beckett, Carl D. (Vancouver, WA)
O'hara, Kevin D. (Washougal, WA)
Olsen, Daniel B. (Fort Collins, CO)
Soar, Steven E. (Vancouver, WA)
Siemer, Glenn E. (Vancouver, WA)
Application Number:
Publication Date:
03/31/1998
Filing Date:
03/19/1996
Export Citation:
Micropump, Inc. (Vancouver, WA)
Primary Class:
Other Classes:
137/625.21,
137/625.69,
International Classes:
F04B1/12; (IPC1-7): F04B1/12
Field of Search:
417/269, 417/515, 417/516, 417/517, 417/518, 417/519, 137/625.21, 137/625.69, 91/499, 91/503
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US Patent References:
5230610Reichenmiller4687426Yoshimura4556371Post4436230Hofmann4432310Waller417/2694359312Funke et al.4233002Birenbaum4028018Audsley3823557N/AVan Wagenen et al.91/4993816029Bowen et al.3702143N/AVan Wagenen et al.3272079Bent91/4993016837Olugos2745350Capsek417/5162600099Detrez2458294Parker2397594Buchanan91/5032225788Mc Intyre417/2692010377Sassen1723874Lunge0646024N/AGoodhart91/499
Foreign References:
EP0172780Fluid operated pump.DE658937C91/499SU91/503GB768330A91/499
Primary Examiner:
Thorpe, Timothy
Assistant Examiner:
Tyler, Cheryl J.
Attorney, Agent or Firm:
Klarquist Sparkman Campbell Leigh Whinston LLP
Parent Case Data:
CROSS REFERENCE TO RELATED
CASESThis is a Continuation-in-Part of U.S.
patent application Ser. No. 08/406,399 filed Mar. 20, 1995
now abandoned, and U.S. patent application Ser. No.
08/407,405 also filed Mar. 20, 1995 now allowed.
1. A pump for delivery of a fluid, comprising:
first and second reciprocating pistons, wherein the first piston communicates with a first pumping chamber, and the second piston communicates with a se
a rotary cam that reciprocates the piston
an inlet flow path that communicates with the first pumping chamber when the first piston is reciprocating in a direction that draws fluid into the first pumping chamber, and with the second pumping chamber when the second piston is reciprocating in a direction that draws fluid into the se
an outlet flow path that communicates with the first pumping chamber when the first piston is reciprocating in a direction that expels fluid out of the first pumping chamber, and with the second pumping chamber when the second piston is reciprocating in a direction that expels fluid out of the se
a control surface carried by the cam, wherein the control surface alternately moves between a first position and a second position, and flow channels are inscribed in the control surface, wherein when the control surface is in the first position the inlet flow path to the first pumping chamber is continuous through the flow channels and the outlet flow path from the first pumping chamber is interrupted, and the inlet flow path to the second pumping chamber is interrupted and the outlet flow path from the second pumping chamber is continuous through the flow channels, and when the control surface is in the second position the inlet flow path to the second pumping chamber is continuous through the flow channels and the outlet flow path from the second pumping chamber is interrupted, and the inlet flow path to the first pumping chamber is interrupted and the outlet flow path from the first pumping chamber is continuous through the flow channels.
2. The pump of claim 1 wherein the cam moves the first and second pistons such that the first piston expels fluid when the second piston is drawing fluid in, and the first piston draws in fluid while the second piston expels fluid, and the cam further moves the control valve between the first and second positions, with the control valve in the first position when the first piston draws in fluid and the second piston expels fluid, and the control valve in the second position when the first piston expels fluid and the second piston draws in fluid.
3. The pump of claim 1 wherein the cam rotates around an axis that is substantially parallel to the first and second pistons.
4. The pump of claim 1 wherein the cam control surface has a variable shape that reciprocates the pistons.
5. The pump of claim 1 wherein the control surface impinges against and reciprocates the pistons, which are spring biased against the cam surface, and the control surface also moves the control valve between the first position and the second position of the control valve.
6. The pump of claim 4 wherein the variable shape of the surface is provided by a raceway in the surface of the cam.
7. The pump of claim 4 wherein the variable shape of the control surface is a slanted surface.
8. The pump of claim 6 wherein the raceway has a surface that reciprocates the first piston faster in the direction that draws fluid into the first pumping chamber than in the direction that expels fluid out of the first pumping chamber, and the surface of the raceway reciprocates the second piston faster in the direction that draws fluid into the second pumping chamber than in the direction that expels fluid out of the second pumping chamber.
9. The pump of claim 1 wherein the control surface is a variable shaped surface that reciprocates the first and second pistons as the cam rotates, and the control surface is rotated by the cam, wherein the control surface has a plurality of grooves inscribed therein that establish passageways through which the control valve directs the flow of the fluid to establish the continuous and interrupted flow paths when the control valve is in the first and second positions.
10. The pump of claim 9 wherein the plurality of grooves comprise:
a first annular groove in communication with one of the inlet or outlet flow path throughout
a second groove that is coincident with an inner circle circumscribed
an indentation on the axis of rotation of the cam that, throughout rotation of the cam, is in communication with the inlet or outlet flow path that is not in communication with the
wherein the second groove comprises a first groove portion and a second groove portion that are discontinuous with each other, and the first and second groove portions alternately communicate with the first and second pumping chambers as the con
a first connecting groove that connects the first groove portion of the second groove with the indentation on
a second connecting groove that connects the second groove portion of the second groove with the first annular groove.
11. The pump of claim 10 wherein the control surface apposes a control plate that cooperatively with the grooves forms the passageways, and the control plate includes a plurality of openings therethrough that establish communication between the passageways and the inlet and outlet flow pathways, and between the passageways and the first and second pumping chambers.
12. A pump for continuous delivery of a fluid, comprising:
an inlet flow path through which fluid is d
an outlet flow path through which fluid is del
a plurality of reciprocating pistons, wherein each piston communicates with a pumping chamber to draw fluid from the inlet flow path into the pumping chamber as the piston moves in a first direction, and to force fluid out of the pumping chamber through the outlet flow path as the piston moves i
a rotary cam that rotates around an axis of rotation and reciprocates the piston
a control surface carried by the cam and intersected by the axis of rotation, wherein flow control channels are inscribed in the control surface, and the flow control channels comprise:
a continuous a
a discontinuous annular inner channel circumscribed by the outer continuous annular channel and forming a first arc shaped inner channel portion and a second arc shaped i
a localized indentation at the center of
a first communicating channel between the localized indentation and the first arc shaped i
a second communicating channel between the outer channel and the second arc shaped i
separate pumping chamber flow paths communicating between the continuous outer annular channel and each of
a stationary control plate that fits against the control surface to form closed passageways between the control plate and the channels in the control surface, wherein the control plate has
a first opening through the control plate positioned to communicate with the continuous annular outer channel and one of the inlet flow path or outlet flow path throughout rotation of
a second opening through the control plate positioned to communicate, throughout rotation of the control surface, with the localized indentation and the one of the inlet flow path or outlet flow path that does not communicate with the a and
a plurality of pumping chamber openings positioned to communicate between the pumping chamber flow paths and the inner channel on the control surface.
13. The pump of claim 12 wherein the rotary cam has a raceway with a patterned surface over which the pistons ride to reciprocate as the cam rotates.
14. The pump of claim 12 wherein the rotary cam has a slanted surface that impinges against a bearing end of the pistons to reciprocate the pistons as the cam rotates.
15. The pump of claim 12 wherein the plurality of reciprocating pistons comprises an odd number of reciprocating pistons.
16. The pump of claim 15 wherein the odd number of reciprocating pistons is three reciprocating pistons.
17. A pump for substantially pulseless delivery of a fluid, comprising:
a housing containing first and second spring biased piston assemblies, the first piston assembly comprising a first piston bore with a first reciprocating piston disposed in the first piston bore, and a first pumping chamber in the first piston bore, the second piston assembly comprising a second piston bore with a second reciprocating piston disposed in the second piston bore, and a second pumping chamber in th
a rotary cam that reciprocates the piston
an inlet flow path through the housing and that communicates with the first pumping chamber when the first piston is reciprocating in a direction that draws fluid into the first pumping chamber, and with the second pumping chamber when the second piston is reciprocating in a direction that draws fluid into the se
an outlet flow path through the housing that communicates with the first pumping chamber when the first piston is reciprocating in a direction that expels fluid out of the first pumping chamber, and with the second pumping chamber when the second piston is reciprocating in a direction that expels fluid out of the se
a control surface carried by the cam, wherein the control surface alternately moves between a first position and a second position, and flow channels are inscribed in the control surface wherein when the control surface is in the first position the inlet flow path to the first pumping chamber is continuous through the flow channels and the outlet flow path from the first pumping chamber is interrupted, and the inlet flow path to the second pumping chamber is interrupted and the outlet flow path from the second pumping chamber is continuous through the flow channels, and when the control surface is in the second position the inlet flow path to the second pumping chamber is continuous through the flow channels, and the outlet flow path from the second pumping chamber is interrupted, and the inlet flow path to the first pumping chamber is interrupted and the outlet flow path from the first pumping chamber is continuous throu and
wherein a bore axis for each piston bore is substantially parallel, and each reciprocating piston is reciprocated by the cam as the cam rotates around an axis parallel to the bore axis for each piston, and the cam moves the first and second pistons such that the first piston expels fluid when the second piston is drawing fluid in, and the first piston draws in fluid while the second piston expels fluid, and the cam further moves the control surface between the first and second positions, with the control surface in the first position when the first piston draws in fluid and the second piston expels fluid, and the control surface in the second position when the first piston expels fluid and the second piston draws in fluid.
18. The pump of claim 17 wherein the cam has an impingement surface shaped to impinge the pistons, and the impingement surface is shaped to reciprocate the pistons such that the fluid delivery of the pump is substantially constant.
19. The pump of claim 18 wherein the impingement surface is shaped to displace each piston in a positive displacement direction away from a neutral position to expel fluid from the pumping chamber, followed by a reversal of piston direction to a negative displacement direction that draws fluid into the pumping chamber, and the period of time during which negative displacement of each piston occurs is less than the period of time during which positive displacement of each piston occurs, and the positive displacements of the first and second pistons are in staggered phases, such that the output flow of the first and second pistons superimpose to provide a substantially continuous fluid flow from the pump.
20. The pump of claim 19 wherein the cam moves at a constant rotational speed and is shaped to displace the first piston in the positive displacement direction in which fluid is forced out of the first pumping chamber, then hold the positive displacement of the first piston at a constant maximum displacement position, then displace the first piston in the negative displacement direction until a maximum negative displacement
the cam is further shaped to displace the second piston in the positive displacement direction in which fluid is forced out of the second pumping chamber, then hold the positive displacement at a constant maximum positive displacement position, then displace the second piston in the negative displacement direction until the maximum negative dis
displacement of the first piston in the positive displacement direction begins when the second piston first reaches its maximum positive displacement, and displacement of the first piston in the positive displacement direction continues during the entire period during which the second piston is displaced in the negative displacement direction and reaches the maximum negative displacement position of the second piston, the maximum positive displacement position of the first piston is reached as the maximum negative displacement of the second piston ends and displacement of the second piston in the posit
displacement of the first piston in the negative displacement direction begins during displacement of the second piston in the positive displacement direction, and the first piston reaches it maximum negative displacement position during the displacement of the second piston in the positive displacement direction.
21. The pump of claim 19 wherein the control surface comprises a valve member having a control surface with the flow channels inscribed therein, and a cover over the flow channels such that the flow channels and cover form closed fluid passageways therebetween, and in the first position of the control valve, the fluid passageways of the control valve establish fluid communication between the inlet and the first pumping chamber and the outlet and the second pumping chamber, and in the second position the valve member establishes fluid communication between the inlet and the second pumping chamber, and the outlet and the first pumping chamber.
22. The pump of claim 21 wherein the control surface rotates relative to the cover, and the cover has openings therethrough that communicate with the fluid passageways.
23. The pump of claim 19 wherein the control surface is part of a control valve comprising a control disc and the control surface is flat, and a cover with a flat inside face bears against the control surface, wherein the disc rotates relative to the cover about an axis of rotation, and flow channels in the control surface form, in cooperation with the overlying cover, an inlet passageway and an outlet passageway that do not communi
first, second, third and fourth bores extending through the cover, wherein the first bore is an inlet bore that communicates with the inlet line, the second bore is an outlet bore that communicates with the outlet line, the third bore communicates with a flow path to the first pumping chamber, and the fourth bore communicates with a flow path to the se
wherein the inlet passageway comprises an annular inlet passageway circumscribing an arcuate inlet passageway, and the annular and arcuate inlet passageways both have the same center and radius of curvature, and a communicating passageway extends radially on the control surface between the annular and arcuate passageways, and the outlet passageway comprises an arcuate outlet passageway with a center of curvature at the axis, and a communicating arm that extends from the arcuate outlet passageway to the center of curvature of the arcuate outlet passageway, and the distance from the axis of the arcuate inlet and outlet pas and
wherein the second bore extends through the cover at the axis to communicate with the arm of the outlet passageway, the distance between the axis and first bore is the same as the distance from the axis to the annular inlet passageway, and the distance between the axis and the third and fourth bores is the same as the radius from the axis to the arcuate inlet and outlet passageways.
24. The pump of claim 19 wherein the control valve comprises a spool valve disposed for axial movement in a spool valve bore in the housing with the spool valve bore axis substantially parallel to the bore axes of the pistons, and the spool valve has first and second necked down portions, with fluid communication between the inlet and the first pumping chamber being established through the first necked down portion when the spool valve is in the first position, fluid communication between the outlet and the second pumping chamber being established through the second necked down portion when the spool valve is in the first position, fluid communication between the inlet and the second pumping chamber being established through the second necked down portion when the spool valve is in the second position, and fluid communication between the outlet and the first pumping chamber being established through the first necked down portion when the spool valve is in the second position.
25. A pump for substantially pulseless delivery of a fluid, comprising:
a housing containing first and second piston pump assemblies, the first piston pump assembly comprising a first spring biased reciprocating piston in a first piston bore, and a first pumping chamber formed in the first piston bore, the second piston pump assembly comprising a second spring biased reciprocating piston in a second piston bore, and a second pumping chamber formed in the second piston bore, the first and second piston bores having axes that are su
a control valve in the housing that moves between a first and a second position, wherein the control valve has a first passageway connecting portion and a second passagewa
an inlet line into the housing that communicates wi
an outlet line from the control valv
a first pumping chamber passageway from the first pumping chamber
a second pumping chamber passageway from the second pumping chamber
a cam that moves at a constant rotational speed and impinges against the first and second pistons to move the first piston against its spring bias to force fluid out of the first pumping chamber, and subsequently allows the first piston to move with its spring bias to draw fluid into the first pumping chamber, and the cam further moves the second piston against its spring bias to force fluid out of the second pumping chamber, and subsequently allows the second piston to move with its spring bias to draw fluid into the se
where the cam has an axis of rotation that is substantially parallel to the axes of the first and second piston bores, and movement of the cam further moves the control valve between
(a) a first position in which fluid communication is established between the inlet line and the first pumping chamber passageway through the first passageway connecting portion, as well as between the second pumping chamber passageway and the outlet line through the second passageway connecting portion, while blocking fluid communication between the outlet line and the first pumping chamber passageway, and the inlet line and the second pumpin and
(b) a second position of the control valve in which fluid communication is established between the inlet line and the second pumping chamber passageway through the second passageway connecting portion, as well as between the outlet line and the first pumping chamber passageway, while blocking fluid communication between the outlet line and the second pumping chamber passageway, and the inlet line and the first pumpin
wherein the cam is shaped to displace the first piston in a positive displacement direction in which fluid is forced out of the first pumping chamber, then hold the positive displacement of the first piston at a constant maximum displacement position, then displace the first piston in a negative displacement direction until a maximum negative displacement position is reached, and during the negative displacement of the first piston fluid is drawn into the f
the cam is further shaped to displace the second piston in a positive displacement direction in which fluid is forced out of the second pumping chamber, then hold the positive displacement at a constant maximum positive displacement position, then displace the second piston in a negative displacement direction until the maximum negative displacement is reached, and during the negative displacement of the second piston fluid is drawn into the se
displacement of the first piston in the positive displacement direction begins when the second piston first reaches its maximum positive displacement, and displacement of the first piston in the positive displacement direction continues during the entire period during which the second piston is displaced in the negative displacement direction and reaches the maximum negative displacement position of the second piston, the maximum positive displacement position of the first piston is reached as the maximum negative displacement of the second piston ends and displacement of the second piston in the posit
displacement of the first piston in the negative displacement direction begins during displacement of the second piston in the positive displacement direction, and the first piston reaches it maximum negative displacement position during the displacement of the second piston in the positive di and
wherein the control valve is a member that rotates with the cam about a common axis, and the member has a generally epsilon-shaped passageway with an arcuate back and a straight cross portion that extends toward and terminates in a terminus at the axis of rotation of the member, and the epsilon-shaped passageway is circumscribed by an annular passageway with a side-arm passageway extending from the annular passageway towards the epsilon-shaped passageway, and the side-arm passageway terminates in an arcuate passageway that is on a common circle with the arcuate back of the epsilon-shaped passageway, further wherein the annular passageway is always in fluid communication with the inlet line, and the outlet line is always in fluid communication with the arcuate back of the terminus of the cross portion of the epsilon shaped passageway, and when the control valve is in the first position the first pumping chamber passageway is in fluid communication with arcuate passageway and the second pumping chamber passageway is in fluid communication with the arcuate back of the epsilon shaped passageway, and when the control valve is in the second position the first pumping chamber passageway is in fluid communication with the arcuate back of the epsilon shaped passageway, and the second pumping chamber passageway is in fluid communication with the arcuate passageway.
26. The pump of claim 25 wherein the control valve is a member that rotates with the cam about a common axis, and the member has a generally epsilon-shaped passageway with an arcuate back and a straight cross portion that extends toward and terminates in a terminus at the axis of rotation of the member, and the epsilon-shaped passageway is circumscribed by an annular passageway with a side-arm passageway extending from the annular passageway towards the epsilon-shaped passageway, and the side-arm passageway terminates in an arcuate passageway that is on a common circle with the arcuate back of the epsilon-shaped passageway, further wherein the annular passageway is always in fluid communication with the inlet line, and the outlet line is always in fluid communication with the arcuate back of the terminus of the cross portion of the epsilon shaped passageway, and when the control valve is in the first position the first pumping chamber passageway is in fluid communication with arcuate passageway and the second pumping chamber passageway is in fluid communication with the arcuate back of the epsilon shaped passageway, and when the control valve is in the second position the first pumping chamber passageway is in fluid communication with the arcuate back of the epsilon shaped passageway, and the second pumping chamber passageway is in fluid communication with the arcuate passageway.
27. The pump of claim 26, further comprising a fluid leak return chamber formed in one of the first or second piston bores, and a fluid leak return line communicating with the fluid leak return chamber, wherein the fluid leak return chamber collects fluid that seeps out of the first or second pumping chambers, and returns the fluid to one of the first or second pumping chamber passageways.
28. A pump for delivery of a fluid, comprising:
first and second reciprocating pistons, wherein the first piston communicates with a first pumping chamber, and the second piston communicates with a se
an inlet flow path that communicates with the first pumping chamber when the first piston is reciprocating in a direction that draws fluid into the first pumping chamber, and with the second pumping chamber when the second piston is reciprocating in a direction that draws fluid into the se
an outlet flow path that communicates with the first pumping chamber when the first piston is reciprocating in a direction that expels fluid out of the first pumping chamber, and with the second pumping chamber when the second piston is reciprocating in a direction that expels fluid out of the se
a control valve that alternately moves between a first position and a second position, wherein when the control valve is in the first position the inlet flow path to the first pumping chamber is continuous and the outlet flow path from the first pumping chamber is interrupted, and the inlet flow path to the second pumping chamber is interrupted and the outlet flow path from the second pumping chamber is continuous, and when the control valve is in the second position the inlet flow path to the second pumping chamber is continuous and the outlet flow path from the second pumping chamber is interrupted, and the inlet flow path to the first pumping chamber is interrupted and the outlet flow path from the first pumping c and
wherein each reciprocating piston is reciprocated by a cam having a bearing face, the cam moves the control valve between the first and second positions of the control valve, and the cam has a variable shaped surface that reciprocates the first and second pistons as the cam rotates, and the control valve comprises a control surface rotated by the cam, wherein the control surface has a plurality of grooves inscribed therein that establish passageways through which the control valve directs the flow of the fluid to establish the continuous and interrupted flow paths when the control valve is in the first
and wherein the plurality of grooves comprise:
a first annular groove in communication with one of the inlet or outlet flow path throughout
a second groove that is coincident with an inner circle circumscribed
an indentation on the axis of rotation of the cam that, throughout rotation of the cam, is in communication with the inlet or outlet flow path that is not in communication with the
wherein the second groove comprises a first groove portion and a second groove portion that are discontinuous with each other, and the first and second groove portions alternately communicate with the first and second pumping chambers as the con
a first connecting groove that connects the first groove portion of the second groove with the indentation on
a second connecting groove that connects the second groove portion of the second groove with the first annular groove.
Description:
BACKGROUND OF THE INVENTION1. Field of the Invention This invention concerns a reciprocating piston pump that provides substantially pulseless delivery of a liquid. This pump is particularly suited for supplying liquids used in chromatographic analysis devices, where pulseless flow at low flow rates (0.2-1 ml/min) is required to achieve high instrument sensitivity. 2. General Description of the Background Constant volume, pulseless reciprocating pumps have been disclosed in U.S. Pat. Nos. 3,816,029; 4,028,018; 4,687,426 and 4,556,371. A piston pump using a spool valve to control liquid outlet from the pistons is similarly shown in European Patent No. A20 172 780. Pulseless delivery of a liquid is described in detail in U.S. Pat. No. 4,359,312, which discloses a reciprocating piston pump with two pistons connected in parallel on the discharge side. One of the pistons draws in fluid while the other is delivering fluid. The pistons are controlled by a cam, which is in turn operated by a computer program to compensate for the compressibility of liquid in the pump. The rotational speed of the cam is varied to compensate for the compressibility of liquid in the pump and achieve a constant pump output. U.S. Pat. No. 2,010,377 describes a dual piston pump that achieves non-pulsating fluid output by overlapping the power strokes of each piston in the pump, and controlling the volumetric displacement of the pump per cycle. The combined delivery of the two pistons, per unit time, is substantially constant or non-fluctuating. Each of the pumps shown in the patents described above is relatively large and not well adapted for pumping and delivering very small amounts of liquid at a constant flow rate, as required in chromatographic analyzers. The prior pumps are particularly unsuitable for placement in a compact pumping assembly. Some of these previous pumps also suffer from the disadvantage of requiring complicated computer programs and automated control mechanisms to achieve constant pump output. It is accordingly an object of the present invention to provide a multiple piston pump that is compact and suitable for delivery of very small amounts of liquid. It is yet another object of this invention to provide such a pump that is compact. Finally, it is an object of the invention to provide a piston pump that is simpler in operation than some previous pumps, and particularly is free of the necessity for complex mechanical or computer-assisted operation to provide pulseless delivery of liquid (although such mechanical or computer-assisted operation can be used with the present invention). SUMMARY OF THE INVENTION The foregoing objects are achieved in one embodiment of the present invention by providing a pump having at least a first and second piston, wherein the first piston communicates with a first pumping chamber and the second piston communicates with a second pumping chamber. An inlet flow path communicates with the first pumping chamber when the first piston is reciprocating in a direction that draws fluid into the first pumping chamber, and with the second pumping chamber when the second piston is reciprocating in a direction that draws fluid into the second pumping chamber. An outlet flow path communicates with the first pumping chamber when the first piston is reciprocating in a direction that expels fluid out of the first pumping chamber, and with the second pumping chamber when the second piston is reciprocating in a direction that expels fluid out of the second pumping chamber. A control valve alternately moves between a first position and a second position, such that when the control valve is in the first position the inlet flow path to the first pumping chamber is continuous and the outlet flow path from the first pumping chamber is interrupted, and the inlet flow path to the second pumping chamber is interrupted and the outlet flow path form the second pumping chamber is continuous. When the control valve is in the second position, the inlet flow path to the second pumping chamber is continuous and the outlet flow path from the second pumping chamber is interrupted, and the inlet flow path to the first pumping chamber is interrupted and the outlet flow path from the first pumping chamber is continuous. The control valve preferably includes grooves inscribed in the control surface that establish and break fluid connections as the cam rotates. Each reciprocating piston is reciprocated by a cam having a bearing surface that rotates around an axis that is substantially parallel to the pistons. The bearing surface has a variable shape that reciprocates the pistons, which are spring biased against the bearing surface. The variable shape of the bearing surface may be provided by a raceway in the cam, or a slanted surface with a constant slope. In particularly preferred embodiments, the bearing surface surrounds the control surface, and both are rotated at the same rotational velocity by the cam. In another particular embodiment, the pump includes a plurality of reciprocating pistons, wherein each piston communicates with a pumping chamber to draw fluid into the pumping chamber as the piston moves in a first direction, and to force fluid out of the pumping chamber as the piston moves in a second direction. An inlet flow path delivers fluid to the pump, and an outlet flow path delivers fluid from the pump. A rotary cam rotates around an axis of rotation and reciprocates the pistons as the cam rotates. A control surface carried by the cam has flow channels inscribed therein. One of the flow control channels is a continuous annular outer channel. Another channel is a discontinuous annular inner channel circumscribed by the outer continuous annular channel. The inner channel has a first arc shaped portion and a second arc shaped portion that do not communicate with each other. A localized indentation is provided at the center of rotation of the cam. A first communicating channel extends between the localized indentation and the first arc shaped inner channel portion. A second communicating channel extends between the outer channel and the second arc shaped inner channel portion. A stationary control plate fits against the control surface to form closed passageways between the control plate and the channels in the control surface. The control plate has a first opening through the control plate positioned in alignment with the continuous annular outer channel as that channel rotates on the cam. The first opening establishes fluid communication between the annular outer channel and the inlet flow pathway. A second opening through the control plate is positioned in alignment over the local surface indentation at the axis of rotation of the control surface. The second opening establishes fluid communication with the outlet flow pathway. A plurality of pumping chamber openings through the control plate are positioned on a common circle to establish fluid communication between the pumping chamber flow paths and the discontinuous annular inner channel on the control surface. In yet another embodiment, a multiple piston pump has a housing containing at least first and second spring-biased pump piston assemblies. The first pump piston assembly includes a first elongated piston bore with a reciprocating piston disposed therein, and an enlarged volume area in the first piston bore that forms a first pumping chamber. The second pump piston assembly similarly includes a second elongated piston bore with a second reciprocating piston disposed in the second piston bore, and an enlarged volume area in the second piston bore that forms a second pumping chamber. The enlarged volume area in each piston bore is provided, in one embodiment, by a step or diameter transition, and volumetric displacement is proportional to the differential piston area at the step. An inlet flow path is provided through the housing that communicates with the first pumping chamber when the first piston is reciprocating in a direction that draws fluid into the first pumping chamber. The inlet flow path alternately communicates with the second pumping chamber when the second piston is reciprocating in a direction that draws fluid into the second pumping chamber. An outlet flow path is also provided through the housing to communicate with the first pumping chamber when the first piston is reciprocating in a direction that expels fluid out of the first pumping chamber. The outlet flow path alternately communicates with the second pumping chamber when the second piston is reciprocating in a direction that expels fluid out of the second pumping chamber. The bore axes for the two piston bores are substantially parallel, and each reciprocating piston is reciprocated by a cam that rotates about an axis parallel to the bore axes. The cam moves the first and second pistons in such a manner that the first piston expels fluid while the second piston draws fluid in, and the first piston draws in fluid while the second piston expels fluid. Hence, the pistons are 180 degrees out of phase. The cam further moves the control valve between the first and second positions, with the control valve in the first position during the period in which the first piston draws in fluid and the second piston expels fluid. The control valve is moved to assume the second position when the first piston expels fluid and the second piston draws in fluid. It is a particular advantage of some embodiments of the present invention that the cam has an impingement surface that impinges the pistons, and reciprocates them in such a manner that fluid delivery from the pump is substantially constant. Such constant fluid delivery is achieved by providing an impingement surface on the cam that alternately displaces each piston in a positive displacement direction away from a neutral position to create a positive pressure that expels fluid from the pumping chamber. Such positive displacement of each piston is followed by a reversal of piston direction to a negative displacement direction, which creates a negative pressure that draws fluid into each pumping chamber. The period of time during which negative displacement of each piston occurs is less than the period of time during which positive displacement of each piston occurs. Moreover, the positive displacements of the first and second pistons are in staggered phases, such that the output flows of the first and second piston pumps are superimposed to provide a substantially continuous fluid flow from the pump.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a graph showing piston speed versus time for the first piston (piston A) and second piston (piston B) of one embodiment of the dual piston pump, with the respective inputs and outputs of the two pistons shown within the curves of the graphs. FIG. 2 is a graph similar to FIG. 1, but showing the superimposed inputs and outputs of pistons A and B in FIG. 1, and the corresponding position of the valve. FIG. 3 is a cross-sectional view through a first embodiment of the piston pump of the present invention. FIG. 4 is a view of the cam and control valve for the piston pump, taken along lines 4--4 of FIG. 3, with the position of control valve passageways shown on the cam. FIG. 5 is a view of the control valve portion of FIG. 4, showing the position of the control valve passageways after the control valve has rotated through a 180 degree rotation from the position shown in FIG. 4. FIG. 6A is an enlarged, cross-sectional view through one of the piston bores illustrating the differential piston area that is proportional to volumetric displacement. FIG. 6B is an alternative pumping chamber embodiment. FIG. 7 is a schematic view of a continuous cross-section through a cam raceway of the operating cam of FIGS. 3-5, illustrating a groove configuration that controls the power stroke of each piston and permits precise, constant volumetric displacement of a small volume of liquid. FIG. 8 is a schematic cross-sectional view of a second embodiment of a pump, in which the control valve is a spool valve in a first position. FIG. 9 is a view of the piston pump of FIG. 8, but in which the control valve has been moved to a second position. FIG. 10 is a graph showing the piston and valve positions of one embodiment of the pump, as the operating cam rotates through a 360 degree cycle. FIG. 11 is a cross-sectional view of another embodiment of the pump, in which the bearing surface of the cam is a slanted, annular wobble plate. FIG. 12 is a view of the control surface carried by the cam, in which grooves have been inscribed to form fluid passageways in cooperation with an overlying control plate. FIG. 13 is a cross-sectional view, taken along view line 13--13 in FIG. 11, but with the cam rotated counterclockwise from the position shown in FIG. 12. FIG. 14 is a view, similar to FIG. 13, of a three piston embodiment of the pump.
DETAILED DESCRIPTION OF SEVERAL PREFERRED EMBODIMENTS A dual piston pump 10, shown in FIG. 3, is capable of substantially pulseless delivery of a fluid, such as liquid water. The pump includes a housing 12 that contains first pump piston assembly 14 and second pump piston assembly 16. First assembly 14 includes a reciprocating first piston 18 in a first piston bore 20 that extends from an upper surface of housing 12. Piston 18 has a large diameter portion 22 that fits Within a correspondingly enlarged diameter portion of bore 20. The piston has a rounded bearing tip 23 that extends into a cam chamber 24 to engage a cam bearing surface. Piston 18 also includes a reduced diameter portion 25 with an upper spring seat surface 26, that fits within a reduced diameter portion of bore 20. Piston 18 is capable of reciprocating in bore 20 against the bias of a helical spring 28 with an upper end that seats against an internal shoulder 30 of bore 20, and spring 28 extends through bore 20 to sit on a flat upper face 26 of portion 25 of piston 18. A pair of parallel, spaced, annular seals 32, 34 are placed around piston 18 with seal 32 circumscribing portion 22, and seal 34 circumscribing portion 25 slightly above an annular face 35 between portions 22, 25 of piston 18. A first pumping chamber 36 is formed in the bore 20 by the necked down portion of piston 18, and extends from seal 34 to the annular face 35. Chamber 36 is shown in a compressed condition in FIG. 3, but the chamber expands as piston 18 is forced downwardly by spring 30, and the expanding chamber creates a suction pressure that draws liquid into the chamber in a manner described below. Second assembly 16 is similar to assembly 14 described above. Second assembly 16 includes a reciprocating piston 48 in second piston bore 50 that extends from an upper surface of housing 12 through to cam chamber 24, where it abuts a cam raceway described below. Piston 48 has a large diameter portion 52 that fits within a correspondingly enlarged diameter portion of bore 50. The piston has a rounded bearing tip 53 that extends into cam chamber 24. Piston 48 also has a reduced diameter portion 55. Piston 48 is capable of reciprocating in bore 50 against the bias of a helical spring 58 that seats on an internal shoulder 60 of bore 50 and extends through bore 50 to also seat on a flat upper face 59 that forms the top surface of portion 55 of piston 48. A pair of parallel, spaced, seals 62, 64 are placed around piston 48 with seal 62 circumscribing portion 52, and seal 64 circumscribing portion 55 slightly above an annular face 65 between portions 52, 55 of piston 48. A pumping chamber 66 is formed in the bore 50 by the necked down portion of piston 48. Chamber 66 extends from seal 64 to annular face 65. Chamber 66 is shown in a fully expanded condition in FIG. 3, with piston 48 displaced completely downward by the expansion of spring 58 and the changing surface of the cam described below. The volume of chamber 66 will diminish as piston 48 is subsequently moved upwardly, which will create a positive pressure in chamber 66 as its volume is reduced. Large diameter portions 22, 52 of pistons 18, 48 extend into cam chamber 24 to contact a raceway 84 of cam 80. The cam moves at a constant rotational speed and has a surface that impinges against the pistons 18, 48 to reciprocate them against the bias of their respective springs 28, 58. Cam 80 includes a cylindrical cam collar 81 having a flat upper bearing surface 82 (FIGS. 3 and 4) with a continuous annular cam raceway 84 having a center of curvature at the axis of rotation of the cam. The bearing tips 23, 53 of pistons 18, 48 abut against and ride within the groove 84, and are maintained in contact therewith by the bias of springs 28, 58. Raceway 84 has a varying depth, described further below, which moves pistons 18, 48 against the bias of springs 28, 58 to stagger the pulsatile outflow from each of piston assemblies 14, 16 and achieve substantially continuous liquid outflow from pump 10. Cam 80 further includes a downwardly extending annular bearing collar 86 through which a drive shaft 88 extends. Shaft 88 is fixed to collar 86 to rotate cam 80 as shaft 88 rotates. Shaft 88 extends along the axis of rotation 90 of collars 81, 86, and the axis 90 is substantially parallel to the longitudinal axes of bores 20, 50. An interior spring chamber 92 of cam 80 contains a helical spring 94 that is seated on annular surface 96 around shaft 88. Spring 94 extends upwardly around a portion of shaft 88 and toward a flat bearing face 98 of a control valve 100 (FIGS. 3-5), to support the control valve. Control valve 100 is carried by cam 80 and rotates with collar 81. A wear plate 104 is fixed to housing 12, does not rotate with cam 80, and has an internal bearing surface 106 (FIG. 3) that bears against opposing bearing surface 82 (FIGS. 4-5). Bearing surface 108, on the upper surface of control valve 100, acts as a control surface that has a series