US3426695A

US3426695A - Metering pump

Info

Publication number: US3426695A
Application number: US552482A
Authority: US
Inventors: Lee E Klaus
Original assignee: Beckman Instruments Inc
Current assignee: Beckman Coulter Inc
Priority date: 1966-05-24
Filing date: 1966-05-24
Publication date: 1969-02-11
Anticipated expiration: 1986-02-11

Description

36 I6 IO A I2 32 53 54 3638 D D Feb. 11, 1969 L. E. KLAUS. 3,426,695

METER ING PUMP Filed May 24, 1966 I Sheet or 4 r l ilj 1 1 wk 62,466

.( u w z l3 I 24 29 3| 3O wal a Milli LEE E. KLAUS I NVENTOR. /%e% ATTORNEY L. E. KLAUS METERING PUMP Feb. 1 l, 1969 FiledMay Z l 1966 LEE E. KLAUS INVENTOR.

ATTORNEY L. E- KLAUS METERING PUMP Feb. 11, 1969 Sheet Filed May 24, 1966 DEGREE OF ROTATION LEE E KLAUS 9 INVENTOR. BY f I ATTORNEY L. E. KLAUS METERING PUMP Feb. 11, 1969 Sheet 4 of 4 Filed May 24, 1966 LEE E KLAUS INVENTOR.

FIG. /5

ATTORNEY United States Patent 3,426,695 METERING PUMP Lee E. Klaus, Sunnyvale, Calif., assignor t0 Beckman Instruments, Inc., a corporation of California Filed May 24, 1966, Ser. No. 552,482 US. Cl. 103161 Int. Cl. F04b 1/10 7 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a positive displacement hydraulic metering pump and, more specifically, to such a pump which is particularly useful in the metering of solutions in liquid phase chromatographic processes.

In liquid phase chromatographic processes there is needed a positive displacement metering pump which provides a continuous and even flow of liquid at both the intake and discharge sides of the pump and in which the valve and cylinder assemblies of the pump do not leak over the pressure range and pumping rates encountered in the use of the pump. Also, the pump must be inexpensive to manufacture and, therefore, require a minimum number of parts for performnig the valving and pumping functions of the pump. In addition, in liquid phase chromatographic processes it is desired that of motion of the liquid through the pump not be impaired by the entrapment of bubbles within the working pump volume since such bubbles destroy the positive displacement characteristics of the pump and at the same time cause large pulsations, or even reversal of flow, when the pump is operated at a high delivery pressure. It is also desired that there be no disruption of the linear continuity of liquid passing through the pump.

It is, therefore, the principal object of the present invention to provide a metering pump which produces a continuous and even flow of fluid at both the intake and discharge sides of the pump.

Another object of the invention is provide an improved, inexpensive metering pump particularly suited for use in metering solutions in liquid phase chromatographic processes.

A further object of the invention is to provide a positive displacement metering pump which is so designed as to minimize entrapped bubbles in the liquid being metered by the pump.

Still a further object of the invention is to provide a pump which is so designed that there is no disruption in the linear continuity of fluid passing through the pump.

According to a principal aspect of the invention, there is provided a positive displacement hydraulic metering pump incorporating a minimum number of parts for producing a continuous and even flow of liquid at both the intake and discharge sides of the pump. The pump comprises a rotor having three equally spaced radially extending cylinders therein with pistons slidably mounted in each of the cylinders for reciprocating movement. The rotor is mounted for rotation about a valve core which incorporates the valving ports for the pump that are opened and closed upon rotation of the rotor about the core. A cam track is associated with the rotor having a cam surface so formed that the pistons reciprocated by the cam track effect a continuous and uniform movement of liquid through the pump.

According to another aspect of the invention, the inlet and outlet ports on the valve core of a pump of the general design described above are displaced along the axis of the core while inlet and outlet passages associated with each cylinder are also axially displaced and arranged to be in registry with either the inlet or outlet port of the valve core, depending upon the rotational position of the rotor. By this arrangement, the liquid moving through the metering pump flows in one direction only at all points within the pump, except for the swept volume of the cylinders in the pump, thus resulting in an arrangement wherein the liquid moving through the pump continuously sweeps entrained gas bubbles in the liquid through the internal volume of the pump.

According to an additional aspect of the invention, a portion of the outlet passages for the cylinders of a pump is provided in the pistons so that there is no disruption in the linear continuity of the fluid passing through the pump.

Other objects, aspects and advantages will become apparent from the following description taken in connection with the accompanying drawings wherein:

FIG. 1 is a longitudinal sectional view of one embodiment of the pump of the present invention;

FIG. 2 is a transverse section view taken substantially along line AA of FIG. 1 showing the three pistons in the rotor of the pump;

FIG. 2a is a sectional View along line BB of FIG. 2;

FIG. 3 is a transverse sectional view taken substantially along line CC of FIG. 1;

FIG. 4 is a schematic diagram showing the configuration of the cam track embodied in the pump illustrated in FIG. 1;

FIG. 5 is a displacement diagram showing the individual operation of each piston during one revolution of the rotor in FIG. 1 and also showing the volume of fluid delivered during such revolution;

FIG. 6 is a sectional view taken along line DD in FIG. 1 showing the outlet port on the outer surface of the valve core;

FIG. 7 is a sectional view taken along line BE in FIG. 1 showing the inlet port on the outer surface of the valve core;

FIG. 8 is a fragmentary view of FIG. 1 showing the relative position of the rotor and valve core during the suction stroke of one piston of the pump;

FIG. 9 is a fragmentary view of FIG. 1 showing the relative position of the rotor and valve core during the exhaust stroke of one piston of the pump;

FIG. 10 is a fragmentary sectional view of a modified rotor and valve core assembly incorporating an improved sealing means for operation at high pressure;

FIG. 11 is an elevation view of the valve core shown in FIG. 10 with the sealing means removed from the core;

FIG. 12 is a perspective view of the outer part of the sealing means;

FIG. 13 is a perspective view of the inner part of the sealing means;

FIG. 14 is a detailed showing of the sealing means mounted in the valve core, in cross-section; and

FIG. 15 is a longitudinal sectional view through a modified form of the pump of the invention.

Referring now to the drawings in detail, wherein like reference characters designate like or corresponding parts throughout the views, there is shown in FIG. 1 a preferred embodiment of the pump of the present invention, generally designated by numeral 10. The pump includes a rotor 12 which is mounted for rotation on a base member 13 via an annular bearing assembly 14 fixed to the base. The rotor has a central bore 15 receiving a valve core 16 about which the rotor is adapted to rotate. The valve core 16 is restrained from rotation about its vertical axis by being connected to the base member 13 by two pins, only one pin 20 being shown which has its upper end loosely positioned in a passage 22 in the valve core and its lower end fixedly mounted in a passage 24 in the base member.

As seen in FIG. 1, the outer surface of the valve core 16 and the central bore of the rotor have mating conical surfaces. A spring 29 has its upper end bearing against the lower portion of the valve core 16 and its lower end bearing against a plate 30 fixed to the base 13 by a plurality of screws 31, only one being shown. The spring 29 urges the valve core 16 upwardly thereby urging the outer surface of the core 16 into sealing relationship with the central bore 15 of the rotor. Since the pin connected to the base member 13 is loosely mounted in the passage 22 in the valve core, not only is the core movable in the axial direction under the force of spring 29, but also the core may shift slightly in the radial direction to ensure a complete mating and sealing of the conical surfaces of the rotor and valve core. Thus, by this arrangement the core is self-aligning in the center of the rotor, thus lowering manufacturing tolerances and, hence, the cost of the pump.

As seen in FIG. 2, the rotor 12 includes three radial cylinders 32 each receiving a piston 34 mounted for reciprocating movement in the cylinders. The cylinders 32 include a reduced diameter portion 36 receiving a reduced diameter forward portion 38 of the piston, the cylinder section 36 closed by the forward piston portion 38 forming the working volume of the pump. Suitable seals, not shown, are provided at the forward portion 38 of each piston. A pin 39 passes laterally through the outer portion of each piston 34 and is slideable in the radial direction in a slot 40 formed in the rotor. The slot terminates in two parallel

cylindrical passages

41, 42, which are on opposite sides of the cylinder 32 and parallel thereto.

Spring guides

43, 44 connected to opposite ends of the pin 39 are slideable in the

passages

41, 42. Coil springs 45, 46 are positioned in the

passages

41, 42, respectively, to urge the spring guides 43, 44 and therefore the piston 34 radially outward. This pin 39 and spring guides 43, 44 serve to resist a twisting torque on the piston 34 which is caused by the cam follower 50, described later, being off axis from the piston.

Referring now to FIGS. 1 and 3, there is associated with each piston a cam follower 50 which engages an internal cam track 52 fixedly mounted to the base 13 of the pump by any suitable means, not shown. The cam follower 50 comprises a low friction bearing member rotatably mounted on a pin 53 which is threaded into an opening 54 in each piston and extends through a radial slot 56 in the face of the rotor adjacent the cam track 52. As can be appreciated, the

springs

45, 46 associated with the pistons urge the cam followers 50 into engagement with the internal surface of the cam track 52.

The annular bearing assembly 14 is positioned between the outer surface 62 of the cam track 52 and the inner surface 64 of an annular shoulder 66 on the lower outer portion of the rotor 12. Gear teeth 67 are formed on the outer surface of the annular shoulder 66 of the rotor 12 which are adapted to be engaged by a driving gear or belt, not shown, which rotates the rotor about its axis.

One of the important features of the invention is the configuration of the internal cam track 52 which, together with the three piston-cylinder assemblies and a valving arrangement which will be described later, provide a metering pump which produces continuous and even flow of liquid at both the intake and discharge sides of the pump. The configuration of the cam track is best seen in FIG. 4 wherein the surface of the cam track is schematically shown. The cam track surface includes two circular arcs of different radii, the larger circular are 68 forming the high dwell section for the cam surface and the smaller circular are 70 forming the low dwell section of the cam surface, each of said sections extending over an arc of 60,

as shown. Adjoining the high and

low dwell sections

68 and 70, respectively, of the cam surface is an exhaust section 72 and a suction section 74 each extending over an arc of 120. The exhaust and suction sections are noncircular and, therefore, effect the reciprocation of each piston in its respective cylinder. These noncircular portions of the cam track are portions of an Archimedian spiral of common focii, the equation for such a spiral being r=a0. The shape of the spirals are governed by the difference between the radii forming the

circular arcs

68 and 70. The ends of the

curved sections

72 and 74 are blended to the

circular arcs

68 and 70 over an arc of about 8 at their points of intersection in order to provide an overall smooth surface for the cam track.

Reference is now made to FIGS. 1 and 6 to 9 showing the valving arrangement for the metering pump of the invention. The valving for the purpose is provided by passages provided in the valve core 16. In the lower portion of the core 16 there is provided an inlet bore 76 which is adapted to be connected to the source of liquid which is desired to be metered by the pump. The inlet bore 76 is connected by a passage 78 to an inlet port 80 extending about 125 about the surface of the core 16 as best seen in FIG. 6. At the upper end of the valve core 16 there is provided an outlet bore 82 connected by a passage 84 to an outlet port 86 which is diametrically opposed from the inlet port 80 and also extends about 125 about the outer surface of the core 16 as best seen in FIG. 7. As will appear later, it is an important feature of the invention that the inlet port 80 and the outlet port 86 in the valve core be displaced along the axis of the valve core 16. An inlet passage 88 and outlet passage 90 displaced along the axis of the pump the same distance as the inlet and

outlet ports

80 and 86 interconnect each cylinder section 36 and the central bore 15 of the rotor as seen in FIGS. 8 and 9.

In operation of the metering pump of the invention, when the rotor 12 rotates about the valve core 16 and the cam follower 50 of a piston 34 engages the suction section 74 of the cam track, the rotor is in the position with respect to the core as shown in FIG. 8. In such position, the inlet port 80 of the valve core is in communication with the inlet passage 88 in the rotor providing flow communication between the inlet bore 76 of the core and the working portion of the cylinder 36 thus permitting liquid to be drawn within the cylinder upon outward movement of the piston. After the cam follower of the piston contacts the high dwell section 68 of the cam track, the outer surface of the valve core 16 closes both of the

passages

88 and 90 in the rotor during 55 of dwell time. Upon further rotation of the rotor relative to the stator, the cam track causing inward movement of the piston over of rotation, resulting in the rotor and valve core being in the position as generally shown in FIG. 9. In such position, the inlet passage 88 in the rotor is now closed by the outer surface of the valve core and the outlet passage 90 is in communication with the outlet bore 82 through the outlet port 86 on the outer surface of the core so that liquid may be expelled from the cylinder 36 through the passage 90 and the outlet bore 82. Further rotation of the rotor brings the cam follower into engagement with the high dwell section 70 of the cam track thereby closing the inlet and

outlet ports

88 and 90 in the valve core over 55 of dwell time and completing the cycle for one revolution of the rotor. It can be appreciated from the above description and the drawings, therefore, that liquid is caused to flow in one direction only within the pump, namely, through the inlet bore 76, inlet port 80, inlet passage 88, into the cylinder 36 and subsequently the liquid is exhausted through the outlet passage 90, outlet port 86 and outlet bore 82 in the valve core. Thus, any bubbles or vapors entrained in the liquid are swept through the internal volume of the pump rather than remaining in the pump as would occur if the liquid did not move in the same direction at all times within the pump.

The continuous, constant flow output of the pump can be best appreciated by referring to FIG. 5 which illustrates the piston stroke of each of the three pistons in the metering pump of the invention over a complete revolution of the rotor of the pump. As can be seen, as the exhaust stroke of one piston terminates, the exhaust stroke of the next piston commences, thus producing a continuous exhausting of liquid from the pump, and, therefore, the liquid moves at a constant volumetric rate of displacement through the pump as illustrated by the straight line curve in the upper portion of the diagram in FIG. 5. Thus, by applicants invention there is provided only a minimum number of piston and cylinder assemblies, namely three, with a single valving member, namely, the valve core 16-, yet this inexpensive and simple arrangement provides a continuous and even flow of liquid at both the intake and discharge sides of the pump. It will be understood that other valving arrangements than that described herein could be utilized as, for example, the inlet port 80 and outlet port 86 in the valve core could be axially aligned with only a single passage connecting the cylinder 36 and bore 14 of the rotor. However, the specific valving arrangement shown in detail in FIGS. 6 to 9 causes the fluid to flow in one direction only through the pump, except for the working volume 36 of each cylinder, thereby sweeping any entrained bubbles in the liquid through the pump. Without this arrangement, the bubbles would destroy the positive displacement characteristics of the pump since variations in the bubble size with pressure changes from intake to discharge would effectively change the displacement volume of the pump, therefore altering the output of the pump.

One of the advantages of the design of the pump of the invention is the mounting of the cam track to one side of the rotor 12 and within the outer circumference of the rotor, thereby providing a more compact arrangement than is normally provided by a pump in which the cam track surrounds the rotor. This compact arrangement is permitted by extending the cam followers 50 through slots 56 in the wall of the rotor.

While the pump of the invention may be formed of any desired materials, it is preferred when the pump is to be utilized in chromatographic processes to form the rotating parts of materials which are resistant to corrosives and have self-lubricating qualities, such as is provided by certain plastics having a relatively low friction coefiicient, for example, Teflon or Kel-F. A pump formed out of such materials and incorporating the conical valve core 16 as shown in FIG. 1 has been found to operate satisfactorily for routine operating backpressures up to about 450 p.s.i. However, for pressures above that figure, leakage will occur between the rotor and valve core. Therefore, according to another feature of the invention there is provided an improved sealing assembly which permits operation of the metering pump substantially above 1000 p.s.i. backpressure. Such a sealing assembly, generally designated as numeral 100, is illustrated in FIGS. 10 to 14. More specifically, in FIG. 10 there is illustrated a fragmentary section of a modified form of the valve core 102 which has a cylindrical outer surface mating with a cylindrical bore 104 in the rotor 12. The core 102 is illustrated in FIG. 11 with the seal ing assembly 100 removed, As seen in FIG. 11, there are provided in the surface of the core 102 a pair of axially displaced

annular grooves

106 and 108 interconnected by a pair of axial grooves 110, only one being shown. The inlet and

outlet ports

80 and 86 are formed in the surface of the valve core 102 within the area enclosed by the

grooves

106, 108 and 110.

The sealing assembly which is adapted to be positioned in the grooves formed on the outer surface of valve core 102 is composed of an outer part 112 and an inner part 114 of substantially the same configuration except that the outer diameter of the inner part 114 is substantially the same as or slightly less than the inner diameter of the outer part 112. The outer part 112 of the sealing assembly comprises a pair of

annular members

116 and 118 interconnected by axially extending

portions

120 and 122 having essentially the same configuration as the grooves in the outer surface of the core 102. The outer part 112 of the sealing assembly is formed of a plastic having a relatively low friction coeflicient, such as Teflon. The inner part 114 includes

annular sections

124 and 126 interconnected by

axial sections

128 and 130. The inner part 114 of the sealing assembly is formed of an elastomeric material, such as silicon rubber. The elastomeric inner part 114 of the sealing assembly is deformed to be assembled into the grooves on the outer surface of the valve core 102 and then the outer plastic part 112 is forced over the elastomeric inner part 114 to provide the final assembly shown in FIGS. 10 and 14. The deformation of the elastomeric part 114 causes a sealing force between the inner faces of the core 102 and the bore 104 of the rotor 12. The plastic outer part 112 provides a mechanical wearing surface of low friction coeflicient for relative motion between the core 102 and the rotating rotor 12. Since the sealing assembly surrounds both inlet port 80 and outlet port 86, complete scaling is provided for the parts. For example, a pump as illustrated in FIGS. 10 to 14 has been constructed and operated at pressures as high as 2200 p.s.i. without leakage occurring.

Referring now to FIG. 15 there is illustrated an additional embodiment of the pump of the present invention. In this embodiment, the pump is designed to permit a constant throughput of liquid through the pump. In other words, the design of the pump is such that the linear continuity or columetric distribution of the liquid as it passes through the pump is not disrupted. This is in contrast to the pump illustrated in FIG. 1 in which that portion of the liquid which first enters the cylinder 36 upon the suction stroke of the piston is the last portion of the liquid to exhaust from the cylinder and exits through the outlet bore 82. The pump illustrated in FIG. 15 permits a constant throughput of liquid by locating the outlet passage for each cylinder in the piston of the cylinder.

More specifically, there is illustrated in FIG. 15 a pump 132 having essentially the same construction as that shown in FIG. 1 except that the forward portion 38 of the piston has a radial passage 134 therein opening through the radially inward end of the piston. A liquid connector extends through a radial slot 142 in the wall of the rotor and through the wall of the piston to communicate with the radial passage 134. A flexible conduit 144 connects the liquid connector 140 to an outlet passage 145 in the rotor. Each of the three pistons in the pump illustrated in FIG. 15 include a flexible conduit 144 connected in the same manner as illustrated in FIG. 15. Except for the outlet passage 145 being connected to the cylinder 36 via the passage 134, connector 140 and flexible conduit 144, the pump illustrated in FIG. 15 and the valving arrangement therefor is the same as that illustrated in FIG. 1.

In operation of the metering pump illustrated in FIG. 15, on the suction stroke of the piston, with the valve core 16 and rotor in the position illustrated in FIG. 15, liquid is drawn through the inlet bore 76 to fill the cylinder 36. At the end of the suction stroke, the inlet port 80 in the outer surface of the core 16 closes and the outlet port 86 opens. As the piston moves radially inwardly during the exhaust stroke, liquid in the cylinder 36 flows through the passage 134 in the piston port 38, through the connector 140, flexible conduit 144 and returns through the outlet port 86, which will then be in registry with the outlet passage 145. Thus, by the arrangement illustrated in FIG. 15, there will be no disruption in the linear continuity of the fluid as it passes through the pump, thus rendering the pump particularly useful in liquid chromatographic processes in which separation and identification of liquids is accomplished and mixing or recombining of separated liquids cannot be tolerated.

What is claimed is:

1. A positive displacement hydraulic metering pump comprising:

a base member;

a valve core supported by said base member;

a rotor having a central bore therethrough receiving said valve core for rotation of said rotor about said valve core;

said rotor having a plurality of radially extending cylinders therein;

a piston slidably mounted in each of said cylinders for reciprocating movement;

said base member supporting cam track means arranged to effect reciprocating movement of said pistons during rotation of said rotor, said cam track means having a suction section, a high dwell section, an exhaust section and a low dwell section;

each of said pistons including cam follower means engaging said cam track;

said rotor having axially displaced inlet and outlet passages therein between each of said cylinders and said core for providing flow communication therebetween;

said valve core having axially displaced inlet and outlet ports in its outer surface, said ports being displaced about the surface of said valve core;

means loosely connecting said valve core to said base member but restraining said valve core from rotation about its axis;

means other than said valve core rotatably mounting said rotor on said base member; and

upon rotation of said rotor about said valve core, said inlet port successively registering with the inlet passages of said cylinders and the surface of said valve core closing said outlet passages of said cylinders when the cam follower means of said pistons engage said suction section of said cam track, and said outlet port successively registering with the outlet passages of said cylinders and the surface of said valve core closing said inlet passages of said cylinders when the cam follower means of said pistons engage said exhaust section, whereby hydraulic flow through said ports is in one direction only.

2. A pump as set forth in claim 1 wherein said valve core and rotor bore have mating conical surfaces and spring means biasing said surfaces of said valve core and rotor into sealing relationship.

3. A pump as set forth in claim 2 wherein a portion of said outlet passage for each of said cylinders extends radially through the piston in said cylinder.

4. A pump as set forth in claim 2 including sealing means between said cylindrical surfaces, said sealing means including two annular members, one of said members being disposed between one end of said valve core and said ports, the other of said member being disposed between the other end of said valve cores and said ports, said sealing means also including two axially extending portions on the i surface of said valve core between the ends of said ports and connecting said annular members.

5. A pump as set forth in claim 4 wherein said sealing means is formed of inner and outer parts having essentially the same configuration, said inner parts being formed of an elastomeric material and said outer part being formed of a plastic having a relatively low friction coefficient;

said valve core having annular and axially extending grooves therein aligned with said annular members and axially extending portions of said sealing means; and

said sealing means being disposed in said annular and axially extending grooves in said valve core.

8 6. A positive displacement hydraulic metering pump comprising:

a base member;

a valve core supported by said base member;

said rotor having a plurality of radially extending cylinders therein;

a piston slidably mounted in each of said cylinders for reciprocating movement;

each of said pistons including cam follower means engaging said cam track, and each of said pistons having a passage therein with one end of said passage opening through the radially inward end of said piston and the other end of said passage opening through the wall of said piston;

a flexible conduit for each piston and associated cylinder, each of said conduits having one end connected to said other end of said passage in each of said pistons and the other end of each of said conduits terminating in each of said outlet passages in said rotor associated with each respective cylinder;

said rotor having axially displaced inlet and outlet passages therein between each of said cylinders and said bore for providing flow communication therebetween;

said valve core having axially displaced inlet and outlet ports in its outer surface, said ports being displaced about the surface of said valve core; and

7. A pump as set forth in claim 6 wherein said rotor has a radial slot through one side thereof communicating and aligned with each of said respective cylinders;

each of said flexible conduits extending through each respective radial slot; and

each of said outlet passages in said rotor opening through the wall of said rotor and receiving said other end of each respective conduit.

References Cited UNITED STATES PATENTS 2,213,236 9/ 1940 Benedek 103161 3,034,451 5/ 1962 Sullivan et al. 103--16l 3,287,993 11/1966 Lomnicki 103-161 X FOREIGN PATENTS 163,356 6/ 1949 Austria.

400,834 6/ 1909 France.

420,102 8/ 1924 Germany.

804,945 5/ 1951 Germany. 1,095,591 6/ 1957 Germany.

WILLIAM L. FREEH, Primary Examiner.