US3666382A

US3666382A - Pump

Info

Publication number: US3666382A
Application number: US22176A
Authority: US
Inventors: Robert F Rasmussen
Original assignee: Roseville Engineering Inc
Current assignee: Roseville Engineering Inc; Hypro LLC
Priority date: 1970-03-24
Filing date: 1970-03-24
Publication date: 1972-05-30
Anticipated expiration: 1989-05-30

Abstract

A HOUSING HAVING THREE IN-LINE CYLINDRICAL OPENINGS FORMED THEREIN WITH AN OUTLET AND INLET IN COMMUNICATION WITH EACH OF SAID OPENINGS, AN INSERT POSITIONES IN EACH OF SAID OPENINGS FOR FORMING OUTELT VALUE MEANS, A SECOND INSERT POSITIONED IN EACH OF SAID OPENINGS FOR FORMING INLET VALVE MEANS, PACKING POSITIONED IN EACH OF SAID OPENINGS AND COOPERATING WITH THE INSERTS TO DEFINE A CYLINDER, AND A PLUNGER MOUNTED IN EACH OF SAID CYLINDERS FOR RECIPROCATING MOVEMENTS. THE FURTHER IMPROVEMENT INCLUDING MEANS SUBJECT TO FLUID OUTLET PRESSURE OPERATING ON THE PACKING TO MAINTAIN A COMPRESSION FORCE ON SAID PACKING. SAID THREE PLUNGERS BEING RECIPROCATED SINUSOIDALLY BY MEANS OF ECCENTRIC MEMBERS ATTACHED TO A DRIVE SHAFT.

Description

y 30, 1972 R. F. RASMUSSEN 3,666,382

PUMP

Filed March 24 1970 3 Sheets-Sheet 1 mvsmoa ROBERT F. Rasmussen:

HTTORNEYS May 30, 1972 R. F. RASMUSSEN PUMP 3 Sheets-Sheet 3 Filed March 24 1970 fins. 9

its. 7

INVENTOR. ROBERT E. RHSMUSSEN ATTORNEYS United States Patent Oflice- 3,666,382 Patented May 30, 1972 3,666,382 PUMP Robert F. Rasmussen, Minneapolis, Minn., assignor to Roseville Engineering, Inc., St. Paul, Minn. Continuation-impart of application Ser. No. 810,681,

Mar. 26, 1969. This application Mar. 24, 1970, Ser. No. 22,176

Int. Cl. F16j 15/00; F04b 21/02, 39/10 US. Cl. 417-533 12 Claims ABSTRACT OF THE DISCLOSURE A housing having three in-line cylindrical openings formed therein with an outlet and inlet in communication with each of said openings, an insert positioned in each of said openings for forming outlet valve means, a second insert positioned in each of said openings for forming inlet valve means, packing positioned in each of -said openings and cooperating with the inserts to define a cylinder, and a plunger mounted in each of said cylinders for reciprocating movements. The further improvement including means subject to fluid outlet pressure operatmg on the packing to maintain a compression force on said packing. Said three plungers being reciprocated sinusoidally by means of eccentric members attached to a drive shaft.

BACKGROUND OF THE INVENTION This application is a continuation-in-part of US. application Ser. No. 810,681, filed Mar. 26, 1969, now abandoned.

Field of the invention to force it out of the cylinder during movement in the opposite direction.

Description of the prior art In general, prior art pumps of the type described are complicated and expensive to produce since many operations are required on the housing to form inlet and outlet valves and cylinders therein. In addition, these prior art pumps generally must be constructed entirely of a material compatible with the fluid being pumped so that no chemical interaction takes place therein. Because inlet and outlet ports and valves are formed in the housing, these prior art pumps are complicated and time consuming to assemble. Further, some multi-cylinder pumps, wherein the plungers move sinusoidally, have been constructed but they are complicated and unaccommodating to nonlubricating fluids. One example of such a pump is disclosed in US. Patent 3,169,488 issued to Galliger.

SUMMARY OF THE INVENTION The present invention pertains to an improved pump having a housing which defines an elongated opening in communication with inlet and outlet ports and insert means positioned in the opening for defining inlet and outlet valve means in communication with the inlet and outlet ports and further defining a cylinder with a plunger positioned therein for reciprocating movements.

It is an object of the present invention to provide an improved pump produced by forming a cylindrical opening in a housing and positioning valve means in the cylindrical opening to define inlet and outlet valves and a cylinder for receiving a plunger therein.

It is a further object of the present invention to provide a pump in which the housing is produced with a head formed of material chemically compatible with a fluid being pumped and the base is formed of a relatively inexpensive material.

It is a further object of the present invention to provide an improved pump wherein packing means encircle the plunger to prevent leakage of fluid into the base of the housing and the packing is maintained in a compressed position by use of compression springs or means subject to the fluid pressure in the outlet port of the pump.

It is a further object of the present invention to provide an improved pump having at least three in-line cylinders with plungers that reciprocate sinusoidally, to provide a net output pressure that is relatively constant.

It is a further object of the present invention to provide an improved pump which is relatively inexpensive and simple to produce and assemble.

These and other objects of this invention will become apparent to those skilled in the art upon consideration of the accompanying specification, claims and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view in side elevation of an embodiment of the improved pump;

FIG. 2 is a sectional view as in FIG. 1;

FIG. 3 is an enlarged view in side elevation, portions thereof broken away and shown in section;

FIG. 4 is an enlarged sectional view as seen generally from the line 44 in FIG. 3, portions thereof broken away;

'FIG. 5 is an enlarged sectional view similar to FIG. 4 illustrating another embodiment, portions thereof broken away;

FIG. 6 is an enlarged exploded view in perspective of a portion of the apparatus illustrated in FIG. 5;

FIG. 7 is a graphic representation of the output flow rate of the three cylinders, the dotted lines indicating individual cylinder flow rates and the full line indicating the total flow rate of the improved pump;

FIG. 8 is a graphic representation of the total flow rate of the improved pump, in dotted line, compared to the total fiow rate of a pump utilizing short connecting rods to drive the plungers;

FIG. 9 is an enlarged sectional view similar to FIG. 4 of another embodiment of the improved pump, portions thereof removed; and

FIG. 10 is a view similar to FIG. 7 illustrating a different position of the mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIGS. l-4 the numeral housing having a head 11 and embodiment the housing seen from the line 22 their associated parts, but it should be understood that any desired number of cylinders might be utilized in the present pump. The head 11 and base 12 are fixedly attached together by means of a plurality of bolts 13 inserted through openings in projecting portions of the head 11 and threadedly engaged into the base 12. In the following description of the figures, the terms upper and lower are utilized to describe the various parts illustrated, although it should be understood that in some instances these are not limiting and the pump might be used in orientations other than that shown.

The head 11 has formed in the upper wall thereof an inlet port 15 which is adapted to have conduit threadedly engaged therein for conveying fluid to be pumped. An outlet port 16 is formed at one end of the head 11 and adapted to have conduit threadedly engaged therein for conveying the fluid away from the pump. Three cylindrical openings generally designated 17 are formed in the head 11 in parallel, longitudinally spaced apart relationship so as to extend generally transverse to the longitudinal dimension of the head 11 and open axially outwardly (or downwardly in the figures) at the junction of the head 11 and the base 12. This particular orienta tion of the cylindrical openings is referred to as an in-line configuration hereinafter. A first elongated cavity 18 formed adjacent the upper wall of the head 11 communicates with the inner end of each of the cylindrical openings 17 and with the inlet port 15. A second elongated cavity 19 extending generally parallel with the cavity 18 and spaced axially outwardly (or downwardly in the figures) therefrom communicates with each of the cylindrical openings 17 and with the outlet port 16. While the head 11 might be formed in a variety of ways the presently disclosed embodiment is formed by casting and by machining the cylindrical openings 17 to fit the various components to be described presently.

Each of the cylindrical openings 17 has a radially in wardly extending flange 20 adjacent the axially inner extremity (or upper end) thereof and defined by the lower wall of the cavity 18. A generally cup-shaded insert 21 is provided with a plurality of openings 22 therethrough and a flexible valve member 23 aflixed to the insert 21 by a centrally located bolt 24. The valve member 23 has a diameter such that it overlies the openings 22 and a spring 25, fixed in position by the bolt 24, biases the valve member 23 against the insert 21 to maintain the openings 22 normally closed. The assembly including the insert 21 is fitted into the axially inner end of the cylindrical opening 17 in abutting engagement with the flange 20. In this position the openings 22 are in communication with the cavity 18.

A second generally tubular insert 30 is formed with a first portion having an outer diameter approximately equal to the outer diameter of the insert 21 and adapted to mate therewith. An O-ring 31 is positioned between the mat'mg portions of the insert 21 and the insert 30 to prevent leakage therebetween. Adjacent the axially outer end of the portion of insert 30 just described is a radially inwardly directed portion having a plurality of openings 32 extending therethrough in a direction approximately parallel with the direction of the cylindrical opening 17. A third portion of the insert 30 extends generally coaxial with the cylindrical opening 17 from the inner edges of the radially inwardly direction portion of the insert 30. The openings 32 in the insert 30 communicate with the cavity 19 and with the cavity formed within the

inserts

30 and 21. A flexible ring or valve member 33, having an inner diameter slightly larger than the outer diameter of the lower portion of insert 30 for easy axially sliding movements thereon and an outer diameter sufficiently large to overlie the openings 32, is slidably engaged over the insert 30 to operate as a valve in conjunction with the openings 32.

A generally tubular insert or packing cartridge 40 is positioned in the cylindrical opening 17 in parallel juxtaposition with the inner walls thereof and with an axially inner edge butting against a radially inwardly directed shoulder 41 in the inner wall of the cylindrical opening 17. The shoulder 41 positions the packing cartridge 40 within the cylindrical opening 17 so that the various springs and valves can operate properly. The insert 40 has a radially inwardly directed flange thereon which engages the axially outer end of the insert 30 to maintain the insert 30 in the correct position. O-rings 42 and 43 are positioned between the insert 30 and the packing cartridge 40 and between the packing cartridge 40 and the head 11 to prevent leakage axially along the sides thereof. A spring 34, positioned between the axially inner end of the insert 40 and the valve member 33, biases the valve member 33 against the insert 30 to normally maintain the openings 132 closed.

Sealing means, which in this embodiment is pump packing 45, is positioned coaxially within the packing cartridge 40 axially outwardly from the insert 30. A metal ring-shaped packing follower 46 engages the upper surface of the packing 45 and a spring 47 positioned between the packing follower 46 and the flange of the packing cartridge 40 biases the packing follower 46 against the packing 45 to maintain compression thereon. A ring-shaped packing seat 48 engages the lower surface of the packing 45 and is held fixedly in position by means of an insert 49.

Insert 49 has a generally tubular configuration with the inner diameter thereof approximately equal to the inner diameter of the packing 45 and the insert 30. An O-ring 50 is positioned between the upper edge of the insert 49 and the lower edge of the packing seat 43 to prevent leakage therebetween. The insert 49 forms an upper bearing for a plunger 55, which is positioned in the cylinder formed by packing 45 and insert 30.

It will be appreciated that the components numbered 2125, 30-34 and 40-50 together define a unitary, removable assembly (best seen in FIG. 3) which, by simple insertion into the receptacle defined in head 11 provides an inlet check valve communicating with the inlet chamber or cavity 18 through its associated opening 17, an outlet check valve communicating with the outlet chamber 19, and a cylindrical pumping chamber in which plunger 55 may reciprocate. It will also be appreciated that, by reason of the several shoulder abutment surfaces between the insert assembly and its receptacle, the head 11 and base 12 cooperate to rigidly retain the insert assembly in operating position; and that removal of the assembly is quickly and easily effected by removal of the bolts 13 and lifting head 11 from base 12. Since the fluid pumped is always isolated from the base 12 and plunger reciprocating mechanism by the improved structure, it is possible. to adapt a given pump to a given fluid simply by changing the insert assemblies and/or head 11.

The plunger 55 has a snap-ring 56 positioned in a groove spaced axially from the lower edge of the insert 49 and a ring-shaped spring seat 57 is coaxially positioned over the plunger 55 in abutting engagement with the snap-ring 5'6. A compression spring 58 is positioned between a radially outwardly directed flange of the insert 49 and the spring seat 57 to bias the plunger 55 axially outwardly in the cylindrical opening 17.

The base 12 of the housing 10 is generally hollow except for a wall 68 adjacent the upper extremity thereof and extending generally transverse to the cylindrical openings 17 in the head 11 (with the head 11 and base 12 fixedly attached), and a second wall 61 parallel with the first wall 60 and spaced therefrom into the base 12. Pairs of

openings

62 and 63 are formed in the

walls

60 and 61 generally coaxial with each of the cylindrical openings 17 in the head 11. The lower opening 63 has an insert 64 therein with an inner wall that slidably engages the outer wall of the plunger 55 and serves as a lower bearing therefor. The upper wall 60 engages the axially outer or lower edge of the upper bearing 49 and holds it fixedly in place in abutting engagement with the packing seat 48 and the packing cartridge 40. Thus, all of the various components in the cylindrical openings 17 of the head 11 are maintained in their correct orientation.

In the event the packing 45 and/or some of the other components in the head 11 become worn after extended use, some leakage of the fluid being pumped may occur before the wear is noticed by an operator. To prevent this leaking fluid from entering the base 12 vents 69 are provided adjacent the juncture of the head 11 and base 12. The vents 69 consist of at least one external opening for each cylindrical opening 17, adjacent the juncture and at least one radially inwardly extending groove formed between the axially outer edges of the packing cartridge 40 and the packing follower 48 and the mating edge of the insert 49. The O-ring 50 prevents leaking fluid from continuing axially along the plunger 55 and directs externally through the vents 69.

A cavity 70 is formed in the base 12 between the wall 61 and the lower wall thereof. The base 12 has a large opening 71 at one end thereof in communication with the cavity 70 for the assembly of the pump and a smaller opening 72 at the other end thereof, generally coaxial with the opening 71. Opening 72 has an axially inwardly directed flange 73 therearound formed integral with the base 12. A generally disc-shaped cover 74 is provided to sealingly fit within the opening 71 and, in conjunction with an O-ring 75, prevent leakage of oil therethrough. The cover 74 has a coaxial opening therethrough with axially inwardly and outwardly directed flanges 76 therearound forming a generally tubular element coaxial with the opening through the flange 73 at the opposite side of the base 12.

A shaft 80 is mounted in the openings formed by the

flanges

73 and 76 by means of

bearings

81 and 82. Bearings 81, which are press fit into the flange 76, have an oil seal 83 fixedly positioned at the outer edge thereof between the shaft 80 and the flange 76 to prevent leakage of oil therethrough. Bearings 82 are the closed type incorporating a cover 84 which is press fit into the opening 72 in the flange 73 to prevent leakage of oil therethrough. In the present embodiment the shaft 80 has three

eccentrics

85, 86 and 87 spaced axially apart therealong and formed as an integral part thereof. The eccentric 85 is positioned adjacent the inner edges of the flange 76 and the eccentric 87 is positioned adjacent the inner edges of the flange 73. Hardened steel disc-shaped

wear plates

90 and 91 are positioned coaxial with the shaft 80 between the eccentric 85 and flange 76 and between the eccentric 87 and flange 73, respectively. The

wear plates

90 and 91 prevent axial movement of the shaft 80 and further prevent wearing of the base 12, which may be constructed of a relatively soft material such as aluminum and the like. The innermost ends of the

flanges

73 and 76 have vertically oriented grooves 92 and 93, respectively, extending diametrically thereacross to provide for a flow of lubricating oil into and out of the

bearings

81 and 82.

Each of the

eccentrics

85, 86 and 87 have

bearings

95, 96 and 97 engaged coaxially thereover with

rollers

98, 99 and 100 engaged coaxially over the

bearings

95, 96 and 97, respectively. Each of the

rollers

98, 99 and 100 have a radially outwardly extending flange aproximately axially centered thereon, which flange engages a groove in the lower end of the plunger 55 associated with the

rollers

98, 99 or 100. The three

eccentrics

85, 86 and 87 are positioned on the shaft 80 so that the maximum eccentricity thereof is located at approximately 120 intervals.

In the operation of the pump a driving force is attached to the shaft 80 to produce rotation thereof. As the shaft 80 rotates, the

eccentrics

85, 86 and 87 cause the three plungers 55 to move radially outwardly and, as the maximum eccentricity passes the lower portion of the plunger 55 assocaited therewith, the plunger 55 is forced radially inwardly in the cylindrical opening 17 by the biasing spring 58. Thus, reciprocating movement is produced in each of the plungers 55 when the shaft is rotated. This reciprocating movement is sinusoidal in nature with the output pressure portion or flow rate of each stroke being illustrated in FIG. 7. Referring specifically to the plunger 55 illustrated in FIG. 4, as the plunger 55 moves radially inwardly in the cylindrical opening 17 fluid is drawn through the openings 22 from the cavity 18, to fill the portion of the cylindrical opening 17 above the plunger 55. During this inward movement of the plunger 55 the flexible ring 33 is held tightly over the openings 32 by a combination of the suction in the cylindrical opening 17 and the springs 34. When the plunger 55 begins to move radially outwardly the fluid in the cylindrical opening 17 is under pressure and the valve member 23 closes the openings 22 to prevent the fluid from flowing back into the cavity 18. The pressurized fluid is thus forced through the openings 32 and moves the flexible ring 53 radially inwardly so that fluid is free to flow into the cavity 19 and through the outlet port 16.

Since each of the three plungers 55 is moving sinusoidally within the cylindrical openings 17 under the impetus of the shaft 80 and attached

eccentrics

85, 86 and 87 and since the pressure output, or flow rate, varies sinusoidally for each cylindrical opening 17 and associated plunger 55 (as illustrated in FIG. 7), the total pressure, or flow rate, at the outlet port 16 follows a curve substantially as illustrated in the solid line of FIG. 7. Also, the reciprocations of the plungers are equiangularly displaced (wtih 3 cylinders the angular spacing is It should be noted from FIG. 7 that the point at which adjacent pressure waves cross, for example is 30 from the end of the first pressure wave and 30 beyond the start of the second pressure wave. Because the sine of 30 is one-half, the sum of the pressure (the total pressure at the outlet port 16) at these crossover points is equal to one, or the peak pressure of any of the pressure waves. Thus, the total pressure at the outlet port 16 is a nearly constant pressure having a slight ripple or variation with a frequency twice that of the three combined pressure waves illustrated in FIG. 7. In a similar fashion the suction at the inlet port 15 is nearly constant.

Referring to FIG. 9, a graphic comparison of the output flow rate of the improved pump (dotted line) to the output flow rate of a pump having plungers driven by short connecting rods (full lines) is illustrated. The short, or low L/R ratios (where L equals the length of the connecting rod and R equals the crank radius), connecting rods have a tendency to produce flow rates in individual cylinders which more closely approximate sawtooth waves, rather than sine waves. The combination of these waves produce a total flow rate having the distorted wave illustrated in FIG. 9 and the relatively widely varying output pressure. As the length of the connecting rod increases (L/R ratio increases) the variations of the total flow rate decrease until the length approaches infinity, the individual flow rates become sinusoidal, and the flow rate curve of the improved pump is reached. The total flow rate curve illustrated by the full line in FIG. 9 is produced by a three cylinder pump having connecting rods with an L/R=2 /2.

It should be noted that the fluid being pumped comes in contact only with the head 11 and portions therein and, thus, only the head 11 and portions therein contacting the fluid need to be chemically compatible therewith. Also, because of the in-line configuration the coring and casting is all done in one plane and, therefore, greatly simplified. Thus, the overall construction of the pump facilitates the manufacture of a line of pumps wherein the heads are altered for various end results, such as for pumping different types of fluids, various pressures and amounts of flow, etc., while the base 12 remains substantially uniform.

In FIGS. 5 and 6 a different embodiment of the pump is illustrated wherein the spring 47, which provides a compression on the packing 45, is eliminated for reasons which will be apparent presently. In this embodiment modified or new components are indicated with a similar or new number and a prime added to indicate a different embodiment. A packing cartridge 40, similar in shape to packing cartridge 40, has a plurality (in this embodiment, four) of openings therethrough extending generally parallel with the axis of the cylindrical opening 17 and substantially centered over the packing follower 46. A plurality of small pistons 51 are slidably engaged in the openings for axial sliding reciprocating movements. Flexible rings or seals 52' encircle each of the pistons 51 to prevent fluid from passing axially therealong. The lower ends of the pistons 51' rest against the packing follower 48 while the upper ends are in communication with the cavity 19 and have outlet fluid pressure thereon.

The packing 45 is most susceptible to movement relative to the plunger 55 when the plunger 55 is moving axial- 1y into the cylindrical opening 17. At this time fluid in the cylindrical opening 17 is under pressure and is being forced out of the cylindrical opening 17 through the openings 32 and into the cavity 19. In the embodiment illustrated in FIG. 5 the fluid under pressure in the cavity 19 is in communication with the axially inner ends of the pistons 51' and produces an axially outward force thereon, which is transmitted through the pistons 51 to the packing follower 48. The packing follower 48 in turn maintains the packing 45 under compression so that leaking does not occur between the packing 45 and the plunger 55. It shouldbe understood that'the pistons 51 are simply one embodiment for utilizing the output fluid pressure to maintain a compressive force on the packing 45 and many other embodiments might be devised by those skilled in the art. One example of such an embodiment is to provide direct communication between the cavity 19 and the packing follower 48 so that fluid passing through the cavity 19 and under outlet pressure will provide a pressure directly on the packing follower 48.

In FIGS. 9 and 10 another different embodiment of the pump is illustrated wherein modified or new components are indicated with a similar or new number and a double prime to indicate a different embodiment. Each of the plungers 55' is formed with a downwardly opening cavity 65' in the lower end thereof, rather than the groove described in the first embodiment. The shaft 80 has three

eccentrics

85, 86 and 87 spaced axially apart therealong and formed as an integral part thereof. Each of the

eccentrics

85, 86 and 87 has an arcuately shaped bearing shoe 66' slidably engaged thereon with a radially outwardly extending tooth 67 formed as an integral part thereof. The shoe 66 is constructed so that an inner arcuate surface having a diameter equal to the diameter of the associated eccentrics 85 86 and 87 is concentric With an outer arcuate surface thereof. The rotation of the eccentries 85 86 and 87 produces a relatively rolling movement between each of the shoes 66' and the associated plungers 55, as illustrated in FIG. 10, thereby, greatly reducing friction and wear. Further, the motion produced by the combined rotary movement of each of the

eccentrics

85, 86 or 87 and the associated shoes 66' urge the plungers 55 in sinusoidally reciprocating movements,

Thus, an improved pump is disclosed which is relatively simple and inexpensive to manufacture since the entire housing can be cast and the cylindrical openings 17 can then be formed with a single tool operation. The present pump is relatively simple and quick to assemble since the various parts are all fitted within the cylindrical opening 17 and the shaft 80 is simply placed in the base 12 so as to contact the lower ends of the plungers 55 Because the cylinders are all in-line the overall construction of the pump is greatly simplified and the reliability and life is greatly increased. In addition, the means for mounting the shaft 80 in the base 12 provides for wear-resistant mounting of the shaft 80 while allowing the base 12 to be constructed of a relatively inexpensive and softmaterial. Further, the use of three cylinders and sinusoidally moving plungers therein produces a relatively constant outlet pressure, or flow rate, and inlet suction. It should be understood that more than three cylinders might be utilized and 8 additional reductions of outlet pressure variations can'b'e realized, for example While four cylinders produce larger variations five or more will produce a smoother outlet pressure if properly timed. Many other advantages and modifications may become apparent to those skilled in the art upon further consideration thereof.

What is claimed is:

1. An improved pump, comprising:

(a) a housing having joinable base 'and head portions;

(b) the head portion including a wall member defining elongated first and second chambers, the first and second chambers being disposed in parallel alignment with the first chamber overlying the second chamber;

(c) a fluid inlet communicating with the first chamber and a fluid outlet communicating with the second chamber;

(d) a plurality of openings alignably formed in the wall member to establish fluid communication between the first and second chambers;

(e) removable insert means for each of said openings disposed entirely within said second chamber and in transverse relation to the first and second chambers, each removable insert means comprising: I

(I) tubular sealing means defining a pumping chamber; a

(2) inlet check valve means abutting the wall member and cooperable with the associated opening and tubular sealing means for admitting fluid from the first chamber to the pumping chamber;

(3) outlet check valve means cooperable with the tubular sealing means for permitting fluid to flow from the pumping chamber to the second chamber;

(4) the tubular sealing means and inlet and outlet check valve means being constructed and arranged for joint assembly;

(f) the head and base portions being constructed and arranged to .cooperably retain the respective insert means when joined;

(g) a plunger reciprocally disposed in each pumping chamber;

(h) and means disposed in the base portion for reciprocating the plungers.

2. The pump defined by claim 1, wherein each tubular sealing means further comprises packing encircling the associated plunger for substantially preventing fluid flow axially therealong.

3. The pump defined by claim 2, wherein each tubular sealing means further comprises biasing means for maintaining a compression force on the packing during reciprocating of the associated plunger. Y

4. The pump defined by claim 3, wherein the biasing means includes means mounted in communication with the second chamber for receiving fluid pressure therefrom during compression strokes of the associated plungenw.

. 5. The pump defined by claim. 1, wherein the plunger reciprocating means comprises a drive shaft rotatably mounted in the base portion and eccentric means rotatably aflixed to the shaft and engageable with each plunger.

6. The pump defined by claim 5, wherein the eccentric means includes a member having a generally circular outer periphery eccentrically attached to theshaft and a'bearing mounted, generally annular. roller coaxially aflixed in overlying relation to the periphery of said member;

7. The pump defined by claims, wherein the eccentric means includes a member having a generally circular outer periphery eccentrically attached to the shaft and a bearing shoe slidably engaged on the outer periphery of said member with a radially outwardly extending tooth engaged in a downwardly opening cavity inthe lower end of the plunger. v I

8; The pump defined by claim 5, including springbia s ing means mounted in the housing and 'urging'the plunger into engagement with'the eccentric means.

9. The pump defined by claim 5, wherein that portion of the base portion in which the shaft is mounted is constructed of a relatively soft material and relatively hard annular wear elements are coaxially positioned with respect to the shaft between radially outwardly extending portions of the shaft adjacent both ends thereof and the base portion.

10. The pump defined by claim 9, wherein bearings mounting the shaft in the base portion are positioned coaxial with the shaft axially outwardly from each wear element and grooves are formed in the base portion adjacent each wear element for the circulation of lubricant into said bearings.

11. The pump defined by claim 5, wherein the eccentric means and plunger are mounted in relative rolling engagement and cooperating groove and flange portions are formed therebetween to substantially prevent relative transverse movements.

12. The pump defined by claim 11, having three openings in the wall member, the plunger engaging means constructed and arranged to effect equiangularly displaced reciprocations of the plunger.

References Cited UNITED STATES PATENTS 3,260,217 7/1966 Thresher 4l7567 2,218,928 10/ 1940 Towler et a1. 74-55 2,523,847 9/1950 lRussey 308-163 3,109,378 11/1963 Baines 417-539 3,330,217 7/1967 Baur et al 417-454 3,371,936 3/1968 Beaudette 277-117 1,070,706 8/1913 Luitwieler 4l7539 2,059,758 11/1936 Stearns 4l7454 FOREIGN PATENTS 993,887 6/1965 Great Britain 417-569 CARLTON R. CROYLE, Primary Examiner J. J. VRABLIK, Assistant Examiner US. Cl. X.R.