CA2020472A1 - Pulseless piston pump - Google Patents

Pulseless piston pump

Info

Publication number
CA2020472A1
CA2020472A1 CA 2020472 CA2020472A CA2020472A1 CA 2020472 A1 CA2020472 A1 CA 2020472A1 CA 2020472 CA2020472 CA 2020472 CA 2020472 A CA2020472 A CA 2020472A CA 2020472 A1 CA2020472 A1 CA 2020472A1
Authority
CA
Canada
Prior art keywords
piston
pump
cam means
pumping
cylinder
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
CA 2020472
Other languages
French (fr)
Inventor
Kenneth E. Lehrke
Bruce A. Mcfadden
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Graco Inc
Original Assignee
Graco Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Graco Inc filed Critical Graco Inc
Priority to CA 2020472 priority Critical patent/CA2020472A1/en
Publication of CA2020472A1 publication Critical patent/CA2020472A1/en
Abandoned legal-status Critical Current

Links

Landscapes

  • Reciprocating Pumps (AREA)

Abstract

ABSTRACT

A multiple piston cylinder reciprocating pump is provided with a cam drive such that the sum of the velocities during the pumping strokes of all of the cylinders is generally constant. The leak free design is provided by utilizing a diaphragm attached to the piston between the main seal assembly and the cam. A flow through intake design is provided which flows incoming material around the piston between the diaphragm and the main seal to prevent the build-up and hardening of material on the piston and in the seal area. The intake and exhaust passages are arranged such that air pockets cannot be formed and any air bubbles which find their way into the pump will rise upwardly out of the pump without restriction.

Description

~2~2 PULSELESS PIST~N PU~P

BA~K(~OI JND OF T~ D~V13~11ON

A myriad cf different types of pumps are known for use in pumping various materials. When it is desired to pump difficult 5 materials, i.e., those that are highly viscous and/or abrasive, the number of choices of pumps suitable for such applications drops substantially, particularly when it is desired to pump such materials at relatively elevated pressures and/or at predetermined flow ra~es.
While reciprocating piston pumps have been widely used in such 10 applications, such pumps suffer from having pulses in the pressure output of the pumps during piston reversal. Such pumps also suffer to a certain extent from leakage and seepage of pumped material past t~2e seals which is particularly critical when the materîal is air-sensitive such as isocyana~es. This leakage is in both directions and 15 can cause environmental contamination, pumped fluid contamination and regenerative abrasive wear damage to the pump. The reduction and/or elin~ination of pulses in the output is particularly impor~ant for circulating systems, fine spray applicat;ons and proportional metering to produce eonstant output.
2 0 Centrifugal pumps are capable of pumping abrasive materials without pressure pulses but suffer from the problems of not being positive displacement type (flow rate is not directl~y related to speed), inefficiency, shaft seal leakage and impose a high degree of shear on materials which may be shear-sensitive.

Gear pumps are commonly used for metering and proportioning apparatus due their ease in synchronizing with other pumps. Such products, however, are ill-suited for purnping of abrasive materials which cause unacceptable wear.

It is therefore an object of this invention to provide a pump capable of handling such ma~erials while providing substantially pulseless operation. It is further an object of this invention to provide such a pump which is ~asily manufactured and which is capable of being operated at varying speeds, flow rates and pressures in an efficient manner. It is yet a further object of this invention to provide such a pump which has lealc-proof operation to avoid contamination of the environment in which the pump is located or contamination of the pumped lluid by the environment.

1 5 SUMMARY OF T~ INVENTION

A multi-piston/cylinder pump is driven by a cam. The use of pistons in conjunction with diaphragms allows a much higher pressure output capability that a simple diaphragm pump and a more positive displacemen$ action than diaphragm pumps. The cam 2 0 is powered by a DC moto`r or other type of conventional variable speed rotary driving mechanism ~electric, hydraulic or the like).
When used with these drives, the pump can be stalled against pressure just like a typical air-operated reciprocating piston pump.
This mode allows adjustable constant flow. A constant speed motor ~2~

driving the pump would use a pressure switch to turn the motor on and off. Because ~he motion input to the pump is rotary, it can be easily synchronized with another pump(s) to provide a plural component material proportioning system or with a conveyor to 5 more fully automate production.

The cam profile is designed so that the reciprocating pistons (which alternate between pumping and intake strokes) have a net velocity sum of their pumping strokes which is generally constant.
By doing so, one essentially can eliminate pressure losses that create 10 pulses which result from the piston reversal of a conventional piston pump. In the preferred embodiment, two pistons are used although it can be appreciated that more pistons may be used if desired.

As shown in this application9 intake flow is controlled by check valves which typically take a discreet amount of time to seat. Fluid 15 can flow backwards during this time causing small pump output pressure variations during the valve seating but such can be compensated for by shaping the cam profile to provide a nearly totally pulseless operation.

Each piston is sealed in its respective cylinder by a relatively 2 0 conventional type seal rnechanism. Attached to the piston OII ~he low pressure intake side of th`e seal is a diaphragm which serves to isolate the fluid from the environment and assure a leak proof device. As used in this application, the term "diaphragm" is understood to include membranes, b~llows or other such structures 2 ~ performing a similar function. An intalce passage provides flow 2 ~ 2 directly over ~he piston between the main seal and the diaphragm to prevent the build-up and hardening of material in the intake section and on the piston. The intake flow then passes through the in take check and into ~he pumping chamber and then exits through an S outlet passage which also has a check valve. This flow path minimizes stagnant areas of non-flowing fluid where fluids may settle out and/or harden. The passage is oriented to minimize air entrapment and continually replenish the fluid in the intake area.

The cam can either be of a push-pull type, that is, where the 10 roller rides in a track or can be a conventional outer profile cam wherein the piston assembly roller is spring loaded against the cam to maintain it in position.

These and other objects and advantages of the invention will appear more fully from the following description made in 15 conjunction ~ith the accompanying drawings wherein like reference characters refer to the same or similar parts throughout the several views.

A BRIEF DESCRIPI~ON QF 1~ DRAWINGS

Figure 1 is a general cross section of the purnp of the instant invention.

Figure 2 is a cross section talcen along 2-2 of Figure 1 showing 5 the cam of the instant invention.

Figure 3 is an alternate embodiment of the cam of Figure 2.

Figure 3a is a chart showing the velocities and outputs of a two piston pump.

DESCRIP~ION OF THE PREFERRE EMBODIMENT

The pump of the instant inYention, generally designated 10, is comprised of a main housing 12 in which runs a shaft 14 having a gear 16 rnounted thereon. A motor (not shown) which may be a DC
brushless type motor7 drives gear 16 and shaft 14 to turn cam 18 15 mounted on the end thereof. A cam follower assembly 20 rides on cam 18 and is comprised of a follower housing 22 having a follower 24 mounted thereto via shaft 26. Follower housing 22 h~s guide rollers 28 mounted on the outside thereof which run in slots 30 in housing 12. Follower assembly 20 is spring loaded against cam 18 2 0 by means of a spring 32.

Follower assembly 20 is attached to a piston 34 and located in between follower 22 and piston 34 is a diaphragm 36. Those three ~2~72 parts are fastened together by a bolt 38 which passes consecutively therethrough. An initial inlet passage 40 leads iIltO a flushing chamber 42 located about piston 34 between diaphragm 36 and main pressure se~l 44 in cylinder 46. Flushing chamber 42 runs 5 circurnferentially around piston 34 thus inlet flow therethrough serves to flush material through which might potentially harden off the surface of piston 34. Inlet flow thence passes through passage 48 in to main inlet passage 50 which has located in series therein a check valve 52 of a conventional nature.

Pumping chamber 54 is loca~ed in the end of cylinder 46 over piston 34 and also has connected thereto outlet passage 56 having an outlet check 5~ of conventional design therein. When the device is positioned as oriented in Figure 1, that is with the inlet and outlet ports 40 and 56 respectively facing upwardly, the product is 15 designed so as to prevent the accumulation of air or other gas within pockets of the pump, that is, all such bubbles and gas may freely flow upwardly and out of the pump thereby reducing problems of priming and assuring full volumetric flow without air entrapment. It can be seen as piston 34 moves upwardly into pumping chamber 34, 2 0 diaphragm 36 flexes upwardly to the point of nearly touching the upper surface 42a of flushing chamber 42 thereby continually assuring a fresh flow of material through the pump and th~
prevention of stagnant flow zones therein.

While the embodiment shown in the drawing figures utilizes a 2 5 spring loaded follower and cam~ it can also be appreciated that the cam drive may be of a different type wherein no such spring is 2~2~ ~2 necessary. Such a type of cam is often referred to as a desmodromic type cam, and an example of such a cam is shown in Figure 3 wherein the roller is guided in a track 60 and is driven in both its pumping and inta~e strokes. It can also be appreciated ~hat seal 44 S may be of any conventional type which is capable of performing a proper sealing function, however, it carl be appreciated that because diaphragm 36 is subjected to relatively low pressures, its service life will be dramatically increased to maintain the pump in a substantially leak-free state. It can also be seen that if seal 44 10 should leak, its leakage is from the high pressure side back into ~he inlet rather than into the çnvironment.

Up to this point, the description has been of a theoretically perfect pump. In reality, check valve physics (closing time, etc.), fluid compressibility and viscosity preclude perfect pulseless output.
15 Satisfactory pulseless output may be obtained by modifying the cam profile to compensate for the above factors. By increasing the velocity of the opposite piston during check valve closing time by putting a "blip" in the cam to change the veloeity profile, the pumping action can be slightly increased near the point of chec~
2 0 valve seating to compensate for the decreased output during the seating time. The required net velocity profile for pulseless output may be different for any material which is pumped. Using a representative fluid such as oil for the purposes of optimizing the velocity profile of the pump results in a solueion which is satisfactory 2 5 for most other fluids.

Additional]y, it can :,e appreciated that such a pump is easily adaptable to power operated valving, that is, valving which could be operated electrica]ly and/or through a mechanical linkage not unli}~e an automotive engine such that the valve opening and closing time S can be selected as desired.

It is conternplated that various changes and modifications may be made tO the pump without departing from the spiriè and scope of the invention as defined by the following claims.

Claims (15)

1. A fluid pump for providing substantially pulseless output comprising;

a plurality of piston-cylinder combinations;
cam means for driving each said piston in each said cylinder, said cam means driving each said piston in each said cylinder in a reciprocating motion alternating between intake strokes and pumping strokes, said cam means driving said pistons such that at least one said piston is in said pumping stroke at all times and the sum of the velocities of said pistons in said pumping strokes is substantially constant at any given speed of said cam means; and inlet check valves, said cam means increasing said velocity sum slightly as said piston switches from said intake stroke to said pumping stroke so as to compensate for the nonlinearity of pump output during seating of said check valves.
2. A fluid pump for providing substantially pulseless output comprising;
a plurality of piston-cylinder combinations;

cam means for driving each said piston in each said cylinder, said cam means driving each said piston in each said cylinder in a reciprocating motion alternating between intake strokes and pumping strokes, said cam means driving said pistons such that at least one said piston is in said pumping stroke at all times and the sum of the velocities of said pistons in said pumping strokes is substantially constant at any given speed of said cam means;

a housing;

a high-pressure seal between said piston and said cylinder for scaling material to be pumped; and a sealing diaphragm attached to said housing and said piston intermediate said high pressure seal and said cam means and to contain any material that might leak past said high pressure seal and as a barrier between the material to be pumped and the environment.
3. The pump of claim 2 further comprising inlet check valves, said cam means increasing said velocity sum slightly as said piston switches from said intake stroke to said pumping stroke so as to compensate for the nonlinearity of pump output during seating of said check valves.
4. The pump of claim 2 further comprising a flushing inlet passage leading from a source of material to be pumped around said piston intermediate said diaphragm and said high pressure seal to minimize stagnation and prevent buildup or solidification of pumped material on said piston.
5. The pump of claim 4 wherein said cylinder, said piston and said high pressure seal form a pumping chamber and said pump further comprises a main inlet passage connecting said flushing inlet passage and said pumping chamber.
6. The pump of claim 5 wherein said main inlet passage comprises an inlet check valve.
7. The pump of claim 6 wherein said inlet passage is located so as to run in a generally vertical direction and configured so as to prevent the trapping of gasses in said chamber and in said passage whereby any gasses will rise through said passage out of said pump.
8. The pump of claim 6 further comprising an outlet passage leading from said pumping chamber, said inlet and outlet passages being located so as to run in a generally vertical direction and configured so as to prevent the trapping of gasses in said chamber and said passages whereby any gasses will rise through said passages out of said pump.
9. The pump of claim 1 wherein said cam means is driven by a variable speed motor.
10. The pump of claim 1 further comprising power operated valving.
11. A fluid pump for providing substantially pulseless output comprising;

a plurality of piston-cylinder combinations;

cam means for driving each said piston in each said cylinder, said cam means driving each said piston in each said cylinder in a reciprocating motion alternating between intake strokes and pumping strokes, said cam means driving said pistons such that at least one said piston is in said pumping stroke at all times and the sum of the velocities of said pistons in said pumping strokes is substantially constant at any given speed of said cam means;

a housing;

a high-pressure seal between said piston and said cylinder for sealing material to be pumped; and a sealing diaphragm attached to said housing and said piston intermediate said high pressure seal and said cam means and to contain any material that might leak past said high pressure seal and as a barrier between the material to be pumped and the environment a flushing inlet passage leading from a source of material to be pumped around said piston intermediate said diaphragm and said high pressure seal to minimize stagnation and prevent buildup or solidification of pumped material on said piston wherein said cylinder, said piston and said high pressure seal form a pumping chamber and said pump further comprises a main inlet passage connecting said flushing inlet passage and said pumping chamber.
12. The pump of claim 11 wherein said inlet passage is located so as to run in a generally vertical direction and configured so as to prevent the trapping of gasses in said chamber and in said passage whereby any gasses will rise through said passage out of said pump.
13. The pump of claim 12 further comprising an outlet passage leading from said pumping chamber, said inlet and outlet passages being located so as to run in a generally vertical direction and configured so as to prevent the trapping of gasses in said chamber and said passages whereby any gasses will rise through said passages out of said pump.
14. The pump of claim 11 wherein said cam means is driven by a variable speed motor.
15. The pump of claim 11 further comprising power operated valving .
CA 2020472 1989-08-08 1990-07-05 Pulseless piston pump Abandoned CA2020472A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CA 2020472 CA2020472A1 (en) 1989-08-08 1990-07-05 Pulseless piston pump

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US391,097 1989-08-08
CA 2020472 CA2020472A1 (en) 1989-08-08 1990-07-05 Pulseless piston pump

Publications (1)

Publication Number Publication Date
CA2020472A1 true CA2020472A1 (en) 1991-02-09

Family

ID=4145410

Family Applications (1)

Application Number Title Priority Date Filing Date
CA 2020472 Abandoned CA2020472A1 (en) 1989-08-08 1990-07-05 Pulseless piston pump

Country Status (1)

Country Link
CA (1) CA2020472A1 (en)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4130471A1 (en) 2021-08-03 2023-02-08 Idromeccanica Bertolini S.p.A. Reciprocation pump

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP4130471A1 (en) 2021-08-03 2023-02-08 Idromeccanica Bertolini S.p.A. Reciprocation pump
WO2023012688A1 (en) * 2021-08-03 2023-02-09 Idromeccanica Bertolini S.P.A. Reciprocating pump

Similar Documents

Publication Publication Date Title
US5145339A (en) Pulseless piston pump
US6296460B1 (en) Rotary cavity pump
EP1740828B1 (en) High pressure slurry piston pump
US5277555A (en) Fluid activated double diaphragm pump
US6079313A (en) Pulseless, reversible precision piston-array pump
US4035109A (en) Pump for fluent, and especially heavy and abrasive materials
US4556371A (en) Constant flow positive displacement pump
CN102207066B (en) Double-acting plunger pump
EP0486556B1 (en) Pulseless piston pump
CA2754997A1 (en) High pressure variable displacement piston pump
EP1398504A1 (en) Double diaphragm pump
US3637330A (en) Multichamber tubular diaphragm pump
CA1122479A (en) Double-acting differential piston supply pump
US4580954A (en) Oscillating-deflector pump
US3954048A (en) High pressure actuator
CA2020472A1 (en) Pulseless piston pump
JPS5818576A (en) Conveyor for liquid or gas
US3368458A (en) Hydraulic motor
US20060159574A1 (en) Piston pump
CN114992077B (en) Reciprocating pump
SU1724924A1 (en) Hydraulically driven reciprocate pump
US5556267A (en) Double acting pump
US571702A (en) stumpp
WO1988002070A1 (en) A fluid-displacement machine
GB1569094A (en) Pumps

Legal Events

Date Code Title Description
FZDE Dead