US3333548A

US3333548A - Positive displacement pump

Info

Publication number: US3333548A
Application number: US465309A
Authority: US
Inventors: Norman A Lyshkow
Original assignee: Precision Scientific Co
Current assignee: Precision Scientific Co
Priority date: 1965-06-21
Filing date: 1965-06-21
Publication date: 1967-08-01
Anticipated expiration: 1984-08-01

Description

Aug l, 1957 N. A. LYSHKOW 3,333,548'

' POSITIVE DISPLACEMENT PUMP Filed June 2l, 1965 3 SheeLs-Shn-am 2 INVENz-on NoRMAN A. LYsHKow 1,3, ma, fwd, www

Aug. 1, 1967 N. A. I YsHKow v 3,333,548

POSITIVE DISPLACEMENT PUMP Filed June 2l, 1965 3 Sheets-Sheet 3 Fc fne "5 @9 @D all' 4J H ,O7 NonMAN A. LvsHkaw n 'b 1W Manni m.- 11 "ebm 'l loo im A'rw,

United States Patent O 3,333,548 POSITIVE DISPLACEMENT PUMP Norman A. LyshkoW, Chicago, Ill., assignor, by mesne assignments, to Precision Scientic Company, Chicago, Ill., a corporation of Delaware Filed `lune 21, 1965, Ser. No. 465,309 3 Claims. (Cl. 10S-154) ABSTRACT OF 'IHE DISCLOSURE A positive displacement pump in which a piston opens an entrance port to admit uid into a pump chamber, then closes the entrance port and increases the pressure on a biased flexible member so as to retract the same against the bias, and then opens an exit port so that the return movement of the biased flexible member discharges the fluid from the pump chamber through the exit port.

This invention relates generally to positive displacement pumps and, more particularly, to an improved positive displacement pump which is suitable for many diiferent laboratory and industrial applications.

It is a primary object of the present invention to provide an improved positive displacement pump which is capable of providing relatively small iluid ow rates with a high degree of accuracy. It is a more specific object to provide such a pump which is capable of delivering uid ow rates on the order of about 0.5 to milliliters per minute with a high degree of accuracy, even over extended operating periods.

It is another object of this invention to provide an 1mproved 'positive displacement pump of the -foregoing type which permits the ow rate to be varied by a single relatively simple adjustment. A related object is to provide such a pump in which the flow rate adjustment can be made simply and accurately even by an unskilled operator.

It is a further object of the present invention to provide an improved positive displacement pump of the type described above which is economical to manufacture and which has a long operating life. In this connection, it is another object to provide such a pump which can be manufactured from a minimum number of parts so that it is inexpensive to manufacture and maintain.

Still another object of this invention is to provide an improved positive displacement pump of the above type which requires only a small volume.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, 1n

which:

FIGURE 1 is an elevation view of an improved positive displacement pump embodying the present invention;

FIG. 2 is a horizontal section taken along line 2-2 1n FIG. 1;

FIGS. 3a through 3d are a series of fragmentary vertical sections of the pump of FIG. l showing the positions of the movable parts at various stages of an operating c cle;

yFIG. 4 is a vertical section of the lower portion of the pump of FIG. 1 containing the cooperating pistons;

FIG. 5 is a fragmentary elevation View of a modified pump including an alternative bellows-type expansioncompression means;

FIG. 6 is a fragmentary elevation View of another moditied pump including another alternative diaphragm-type expansion-compression means;

FIG. 7 is a fragmentary elevation view of a further modified pump including a further alternative elastic bulbtype expansion-compression means;

FIG. 8 is an elevation view of another positive displace- "ice ment pump embodying the present invention with the movable parts shown in the intake position; and

FIG. 9 is a fragmentary View of the pump of FIG. 8 with the movable parts in the discharge position.

While the invention will be described in connection with certain preferred embodiments, it is to be understood that the invention is not intended to be limited to the disclosed embodiments but, on the contrary, it is intended to cover the various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Turning now to the drawings, the illustrative pump includes a cylindrical housing 10 forming a pump chamber 11. The fluid to be pumped is admitted to the housing 10 through an entrance port 12 and is subsequently discharged from the housing at the desired flow rate through an exit port 13. The pump housing 10 is preferably lined with a glass tube 10a because of the low tolerances than can be achieved with that material, but it will be apparent that a number of other materials could be used in place of the glass. Also, the pump housing 10 is shown as having a cylindrical lconiiguration, but the principles of this invention are equally applicable to numerous other geometric configurations.

In accordance with one important aspect of this invention, the pump includes means `for switching the external fluid connection with the pump chamber alternately back and forth between the entrance and exit ports in the pump housing, and means responsive to the fluid connection of the pump chamber with the exit port for forcing uid out of the pump chamber through the exit port. Thus, in the illustrative embodiment shown in the drawings, a primary piston 20 is mounted within the housing 10 for movement between the entrance port 12 and the exit port 13. In order to provide a fluid seal between the piston side walls and the inside walls of the housing 10, the primary piston is of cylindrical shape conforming to the interior shape of the housing 10. Consequently, the piston 20 is capable of moving axially within the pump housing while maintaining a tight iluid seal along the piston side walls which slide over the inner walls of the housing. As will be apparent from the ensuing discussion, the primary piston 20 is positioned within the pump housing so that both the entrance port 12 and the Vexit port 13 are always blocked by the solid piston side walls except when one of the ports is in fluid communication with the passageways formed within the piston, as described in more detail below.

For the purpose of admittinguid from the entrance port 12 into the pump chamber 11, the primary piston 20 is provided with an interior passageway including a transverse leg 21 adapted to communicate with the entrance port 12 when the piston 20 is in a retracted or intake position, as illustrated in FIGURE 3a for example. From the transverse leg 21 the fluid is passed through a longitudinal leg 22 of the interior passageway opening into the pump chamber 11. Thus, as long as the transverse leg 21 of the uid passageway is in communication with the entrance port 12, fluid will flow through the primary piston 20 into the pump chamber 11 until the pump chamber becomes filled.

In order to connect the pump chamber 11 with the exit port 13, it is necessary to move the primary piston 20 longitudinally toward the pump chamber until a second transverse leg 23 of the lluid passageway communicates with the exit port 13, as illustrated in FIGURE 3c for example. When the piston 20 is in this position, the transverse leg 21 is moved completely out of register with the entrance port 12 so that fluid can flow only between the pump chamber and the exit port. Conversely, when the transverse leg 21 is in communication with the entrance port of the pump, the transverse leg 23 is completely out of register with the exit port 13 so that uid ow can occur only between the entrance port and the pump cham- 3 ber. Consequently, it can be seen that the tiuid connection with the pump chamber can be switched alternately back and forth between the entrance and the exit ports by simply moving the primary piston 20 back and forth in the longitudinal direction.

In order to drive the primary piston 20 back and forth lcore 28 secured to the end of the piston extension 25 so as to move the piston to the intake position shown in FIGURE 3a. The piston 20 remains in this position until the solenoid coil 27 is de-energized, at which time Ythe compressed coil spring 26 drives the piston 20 to the discharge position shown in FIGURE 3c. Thus, by simply varying the frequency of energizing pulses supplied to the solenoid drive, the primary piston 20 can be moved back and fox-th between the intake and discharge positions at any desired frequency.

As the primary piston 20 is advanced between the intake position shown in FIGURE 3a and the discharge position of FIGURE 3c, a secondary piston 30 is retracted by pressure of the fluid within the pump chamber 11 against the end 30a of the secondary piston. The secondary piston 30 is biased toward the primary piston 20 by meanskof a coil spring 31 disposed around the secondary piston rod 32 and bearing against the outer end 33 of the secondary piston. As long as the primary piston 20 is somewhere between the entrance and exits ports, the uid pressure is sufficient to overcome the biasing force of the spring 31 and, as a result, the secondary piston 30 is gradually retracted to the position shown in FIGURE 3b. Thus, FIGURE 3b shows the position of the secondary piston 30 and the other pump elements just before the transverse passageway 23 comes into register with the exit port 13. As soon as the transverse leg 23 of the liuid passageway in the primary piston 20 comes into communication with the exit port 13, the fluid pressure within the pump chamber 11 is decreased so that the compressed spring 31 advances the secondary piston 30 to force uid out of the pump chamber through the exit port 13. The force of the secondary pistonr30 continues to discharge ui-d from the pump chamber 11 as long as the passageway 23 remains in communication with the exit port 13, as illustrated in FIGU-RE 3c.

" As the primary piston 20 begins the next intake stroke back toward the Vinlet port 12, the volume of the pump cavity 11 is suddenly increased. Since both the entrance and

exit ports

12 and 13 are closed by the side walls of the piston, 'iiuid cannot enter the increased volume and consequently, there is a brief reduction in pressure within the pump chamber 11 and the piston passageways until the passageway 21 cornes into communication with the entrance port 12. During this interval of reduced pressure, the secondary piston '30 is drawn upwardly a short distance, indicated as distance a in FIGURE 3d, toward Vthe retracting primary piston. This slight overtravel of the secondary piston 30 serves to limit the degree of pressure reduction within the pump chamber and thereby reduces the possibility of air or other uid leaking into the pump chamber during the intervals of reduced pressure. This feature lis believed to be advantageous in extending the operating life and reliability of the inventive pump.

It will be appreciated that the fluid ow rate provided by the illustrative pump can be readily adj-usted by simply varying the frequency Vof the energizing pulses supplied to the solenoid drive 24 so as to vary the frequency of the reciprocating primary piston 20. The capacity of the pump can be varied by changing the dimensions of the pump chamber and/ or the length of the-piston stroke.

4 In FIGURES 5-7, there are illustrated various alternative expansion-compression means which can be substituted for the secondary piston 30 and spring 31 for discharging uid from the pump chamber during the discharge stage of each pumping cycle. Thus, in FIGURE Y.

5 an expansion-compression chamber is provided directly below a pump chamber 11 and primary piston 20 by means of a bellows 40. As the primary piston 20 is advanced from the intake position of FIGURE 3a to the discharge position of FIGURE 3c, the increased fluid pressure within the pump chamber 11 expands the bellows 40, and the bellows then subsequently contracts when the transverse leg 23 of the piston passageway comes into uid communication with the exit port 13 so as to provide the desired .discharge action.

In FIGURE 6, the desired expansion-compression chamber is provided by a diaphragm 50 and a spring 51 anchored to a rigid end plate 52. Thus, as the fluid pressure within the pump chamber 11ris increased due to the downward movement of the piston 20, the spring 51 is compressed so as to draw the flexible diaphragm 50 down into the recess deined by the end plate 52. Then as the piston passageway comes into communication with the exit port 13 to reduce the duid pressure, the spring 51 expands to drive the flexible diaphragm 50 upwardly toward the pump chamber 11, thereby forcing fluid out of the pump chamber through the piston passageway and the main exit port.

In the alternative embodiment of FIGURE 7, an elastic bulb forms the desired expansion-compression chamber. The bulb 60 is expanded by the increased fluid pressure during the discharge stroke of the primary piston 20, and then compresses to drive the fluid out of the pump when the uid pressure is eventually reduced by the liuid communication between the piston passageway and the exit port.

A further alternative embodiment of the present invention is illustrated by the positive displacement pump shown in FIGURES 8 and 9. In this embodiment, the main portion of the pump chamber is formed by a longitudinal passa-geway extending through the entire length of the pump piston 101, and a chamber 102 formed by the pump housing 103 adjacent the lower end of the piston 101 and in fluid communication with the longitudinal passageway 100. 'I'he lower end of the pump chamber 102 is completely sealed against liuid leakage by means of a rigid end plate 103 and a sealing gasket 104 fastened to the bottom of the housing 103 by screws 105. The upper end of the piston passageway 100 opens into a resilient diaphragm or nipple 106 mounted on a sealing disc 107 with the internal cavity 108 formed by the nipple 106 also forming a part of the pump chamber.

When the piston 101 is in the intake position illustrated in FIGURE 8, fluid is admitted into the pumpfchamber through an intake port 109 extending through the pump housing 103. Fluid from the intake port 109 flows around a peripheral intake groove 110 formed in the surface of the piston 101, and then through a radial passageway 111 into the main` longitudinal passageway 100 which Vdirects the uid downwardly into the chamber 102 and upwardly into the cavity formed by the nipple 106. Since the upper end of the piston 101 bears against the inner surface of the upper end of the nipple 106 a pair of Igrooves 112 extend from the end of the passageway 100 down into the nipple cavity 108 so that the passageway 100 is always in uid communication with the cavity 108. For the purpose of `driving the pump piston 101 back and forth between the intake and discharge positions, a

Vmechanical driving arrangement is associated with the upper end of the pis-ton, and the piston is biased up- -wardly thereagainst by a return spring 113 disposed with- 1n the pump chamber 102 and bearin-g against the lower end of the piston.- Consequently, the piston is continuously urged upwardly against a rigid cap 114 which is 75 designed to fit over the narrow upperV end of the nipple 106 in bearing engagement with a cam 115 eccentrically mounted on a main drive shaft 116. As the drive shaft 116 rotates the eccentric cam 115, the cam drives the cap 114 and the piston 101 downwardly against the bias of the return spring 113. This reduces the volume of the chamber 102 and forces Huid from the chamber 102 upwardly -through the passageway 100 into the nipple cavity 108 at increased fluid pressure, thereby liexing the side walls of the nipple 106 outwardly as illustrated in FIG- URE 9.

In order to discharge iluid from the pump chamber, the piston 101 is provided with a second peripheral groove 117 communicating with a radial passageway 118 leading into the main longitudinal piston passageway 100. As soon as the peripheral groove 117 comes into communication with an exit port 119 formed in the pump housing, the iiuid pressure within the pump chamber is decreased so that the flexed diaphragm or nipple 106 tends to resume its natural shape and thereby forces fluid out of the pump chamber through the exit port 119. As the eccentric cam 11S continues to rotate, the spring 113, which was compressed during the down stroke, expands to urge the piston 101 and the nipple cap 114 upwardly until the piston is return to its intake position shown in FIGURE 8. This completes one pumping cycle, and the frequency of these cycles can be adjusted by simply varying the angular velocity of the drive shaft 116.

In accordance with one aspect of this particular embodiment of the invention, an improved sealing means is provided between the pump entrance and exit ports and the side walls of the reciprocating pump piston. Thus, a small sleeve 120, which may be made of Teon for eX.- ample, is fitted into the exit port 119 and biased inwardly against the side walls of the piston 101 by means of a small spring 121. The spring 121 is compressed between a pair of end washers 122 when the external connecting member 123 is threaded into the pump housing. As the piston 101 is reciprocated back and forth between the intake and discharge positions, the outside wall of the piston simply slides over the abutting end of the sleeve 120 so as to maintain a tiuid seal between the piston side wall and the exit port 119. The inner end of the sleeve 120 has a diameter larger than the longitudinal width of the discharge groove 117 formed in the piston so that the sleeve 120 does not slip into the groove 117 when the piston is in its discharge position with the sleeve 120 and groove 117 aligned with each other. A similar sealing arrangement is provided at the entrance port 109.

Since the piston of the pump shown in FIGS. 8 and 9 opens at both ends into uid chambers which are sealed to the atmosphere and in continuous fluid communication with each other, the only seal required along the piston side walls is in the regions of the entrance and exit ports. The two

fluid chambers

102 and 108 at opposite ends of the piston are in continuous fluid communication with each other through the longitudinal piston passageway 100, so any fluid leakage along the adjacent side walls of the piston 101 and the housing 103 simply supplements the main fluid ow through the passageway 100. Thus, this construction eliminates the necessity for maintaining an effective iiuid seal along the entire length of the reciprocating piston except at the entrance and exit ports, where sealing is effected by the relatively simple and inexpensive arrangement provided by the sleeve 120 and spring 121.

While the present invention has been described above with particular reference to specific preferred embodiments, numerous modifications and variations of the same will be apparent to those skilled in ther art. For example, tbe primary piston of the pump of FIGS. l-4 could be driven by means other than the solenoid and spring arrangement described above, such as the mechanical cam arrangement used in the embodiment of FIGURES 8 and 9. Moreover, means other than the exemplary diaphragm or nipple 106 could be used to provide the desired discharge action in the pump of FIGS. 8 and 9.

As can be seen from the foregoing detailed description, this invention provides an improved positive displacement pump which is capable of providing relatively small uid ow rates with a high degree of accuracy. Indeed, it has been found that the pump of this invention is capable of delivering iiuid ow rates on the order of about 0.5 to 5 milliliters per minutes with a high degree of accuracy, even over extended operating periods. Moreover, the inventive pump permits the flow rate to be varied by simply adjusting the frequency of the primary piston drive, so that the flow rate adjustment can be made simply and accurately even by an unskilled operator. Furthermore, the improved pump provided by this invention can be manufactured from a very small number of parts so that it is inexpensive to manufacture and maintain. The aforedescribed pump also has a relatively long operating life and occupies an extremely small volume.

I claim as my invention:

1. An improved positive displacement pump for pumping liuids, said pump comprising the combination of a housing including an entrance port for receiving the uid to be pumped and an exit port for discharging the fluid, a piston mounted within said housing for movement between said entrance and exit ports and including a longitudinal passageway extending between opposite ends of the piston, said piston also including a first peripheral groove and cooperating first radial passageway for providing uid communication between said entrance port and said longitudinal passageway when the piston is in a first position, and a second peripheral groove and cooperating second radial passageway for providing uid -communication between said longitudinal passageway and said exit port when the piston is in a second position, said pump housing forming a pump chamber adjacent one end of said piston in uid communication with said longitudinal passageway, a diaphragm member forming a fluid chamber adjacent the other end of said piston and in fluid communication with said longitudinal passageway, driving means for periodically driving said piston from said first position to said second position so as to reduce the volume of said pump chamber and thereby increase the liuid pressure in the chamber formed by said diaphragm so that the diaphragm discharges fluid through said passageway and said exit ports when the piston is in said second position, and means for returning the piston from said second position to said first position between the successive uid discharges effected by said diaphragm member.

2. An improved positive displacement pump for pumping uids, said pump comprising the combination of a housing including an entrance port for receiving the iiuid to be pumped and an exit port for discharging the fluid, a piston mounted within said housing for movement between said entrance and exit ports and including a iirst radial passageway adapted to communicate with said entrance port when the piston is in a lirst position, a second radial passageway adapted to communicate with said exit port when the piston is in a second position, and a longitudinal passageway providing fluid communication between saidlirst and second radial passageways and extending to one end of said piston, said housing means forming a pump chamber adjacent said one end of said piston in Huid communication with said longitudinal passageway, a diaphragm member mounted in said pump chamber so as to form a flexible wall in said chamber, biasing means operatively associated with said diaphragm member for urging said diaphragm member toward said piston, driving means for periodically advancing said piston from said first position to said second position so as to increase the fluid pressure in said pump chamber to force said diaphragm away from the advancing piston against said bias, whereby the subsequent return movement of said diaphragm by said biasing means discharges uid from said chamber through said longitudinal pas- 7 sageway and said second radial passageway when the piston is in said second position, and means for returning the piston from said second position to said first position between the successive uid discharges effected by said diaphragm.

3. An improved positive displacement pump for pumping uids, said pump comprising the combination of a housing including an entrance port for receiving the uid to be pumped and an exit port for discharging the uid, a piston mounted within said housing for movement between said entrance and exit ports and including a rst radial passageway adapted to communicate with said entrance yport when the piston is in a rst position, a second radial passageway adapted to communicate with said exit port when the piston is in a second position, and a longitudinal passageway providing Huid communication between said irst and second radial passageways and eX- tending to one end of said piston, Vsaid housing means forming a pump chamber adjacent said one end of said piston in fluid communication with said longitudinal passageway, a Ydiaphragm member mounted in said pump chamber so as `to form a exible wall in said chamber,

biasing means operatively associated with said diaphragm member for urging said diaphragm member toward said piston, driving means for periodically advancing said piston from said rst position to said second position so as to increase the fluid pressure in said pump chamber to force said diaphragm away from the advancing piston against said bias, whereby the subsequent return movement of said diaphragm by said biasing means discharges uid from said chamber through said longitudinal passageway and said second radial passageway when the piston is in said second position, means for returning the piston from said second position to said first position between the successive fluid discharges effected by said diaphragm, and sealing means associated with each of said entrance and exit ports, said sealing means comprising a sealing sleeve slidably mounted within the port and biased inwardly against the outside walls of said piston to prevent Huid from leaking from the ports along the piston walls.

References Cited UNITED STATES PATENTS 862,867 8/1907 Eggleston 230-160 1,400,578 12/ 1921 Sweet 103-148 1,425,191 8/ 1922 Garbarini 103--148 1,564,215 12/1925 Dillig 103-171 1,737,389 11/1929 Redmond 103-150 1,944,919 1/1934 Bischof 11B-166.5 2,775,435 12/ 1956 Kommer 103-150 2,881,749 4/ 1959 Pringham 103--53 2,705,458 4/1955 Suden 103-153 2,978,987 4/ 1961 Bessiere 103-154 FOREIGN PATENTS 210,886 2/ 1924 Great Britain.

DONLEY I. STOCKING, Primmy Examiner.

HENRY F. RADUAZO, Examiner.

Claims

1. AN IMPROVED POSITIVE DISPLACEMENT PUMP FOR PUMPING FLUIDS, SAID PUMP COMPRISING THE COMBINATION OF A HOUSING INCLUDING AN ENTRANCE PORT FOR RECEIVING THE FLUID TO BE PUMPED AND AN EXIT PORT FOR DISCHARGING THE FLUID, A PISTON MOUNTED WITHIN SAID HOUSING FOR MOVEMENT BETWEEN SAID ENTRANCE AND EXIT PORTS AND INCLUDING A LONGITUDINAL PASSAGEWAY EXTENDING BETWEEN OPPOSITE ENDS OF THE PISTON, SAID PISTON ALSO INCLUDING A FIRST PERIPHERAL GROOVE AND COOPERATING FIRST RADIAL PASSAGEWAY FOR PROVIDING FLUID COMMUNICATION BETWEEN SAID ENTRANCE PORT AND SAID LONGITUDINAL PASSAGEWAY WHEN THE PISTON IS IN A FIRST POSITION, AND A SECOND PERIPHERAL GROOVE AND COOPERATING SECOND RADIAL PASSAGEWAY FOR PROVIDING FLUID COMMUNICATION BETWEEN SAID LONGITUDINAL PASSAGEWAY AND SAID EXIT PORT WHEN THE PISTON IS IN A SECOND POSITION, SAID PUMP HOUSING FORMING A PUMP CHAMBER ADJACENT ONE END OF SAID PISTON IN FLUID COMMUNICATION WITH SAID LONGITUDINAL PASSAGEWAY, A DIAPHRAGM MEMBER FORMING A FLUID CHAMBER ADJACENT THE OTHER END OF SAID PISTON AND IN FLUID COMMUNICATION WITH SAID LONGITUDINAL PASSAGEWAY, DRIVING MEANS FOR PERIODICALLY DRIVING SAID PISTON FROM SAID FIRST POSITION TO SAID SECOND POSITION SO AS TO REDUCE THE VOLUME OF SAID PUMP CHAMBER AND THEREBY INCREASE THE FLUID PRESSURE IN THE CHAMBER FORMED BY SAID DIAPHRAGM SO THAT THE DIAPHRAGM DISCHARGES FLUID THROUGH SAID PASSAGEWAY AND SAID EXIT PORTS WHEN THE PISTON IS IN SAID SECOND POSITION, AND MEANS FOR RETURNING THE PISTON FROM SAID SECOND POSITION TO SAID FIRST POSITION BETWEEN THE SUCCESSIVE FLUID DISCHARGES EFFECTED BY SAID DIAPHRAGM MEMBER.