US3746476A

US3746476A - Hydraulic pump

Info

Publication number: US3746476A
Application number: US00130372A
Authority: US
Inventors: A Bradley
Original assignee: Applied Power Industries Inc
Current assignee: Enerpac Tool Group Corp
Priority date: 1971-04-01
Filing date: 1971-04-01
Publication date: 1973-07-17
Anticipated expiration: 1990-07-17

Abstract

A hydraulic pump of the axial, parallel piston type comprising a housing divided into first and second sections with the first section defining a chamber. A rotatable shaft extends centrally and axially of said chamber through one end of said housing and has a cam plate keyed thereto for rotation with the shaft. The second section, or piston carrier section is comprised of a moldable plastic material having a plurality of modular units embedded therein. Each of the modular units includes a cylinder for slidably receiving a piston, an output check valve unit integrally attached to said cylinder, and a bypass check valve unit integrally attached to and offset from said output check valve unit. An output manifold and a bypass control manifold are connected to the output check valve unit and the bypass check valve unit respectively of each modular unit.

Description

tlnited States Patent 1191 Bradley HYDRAULIC PUMP [75} Inventor: Arthur S. Bradley, Wauwatosa, Wis.

[73] Assignee: Applied Power Industries, Inc.,

Milwaukee, Wis.

[22] Filed: Apr. 1, 1971 [21] Appl. No.: 130,372

[ July 17, 1973 Primary Examiner-Charles J. Myhre Assistant Examiner-Frank H. McKenzie, Jr. Attorney.lohn J. Byrne [5 7] ABSTRACT A hydraulic pump of the axial, parallel piston type comprising a housing divided into first and second sections with the first section defining a chamber. A rotati i able shaft extends centrally and axially of said chamber [58] Fieid 417/269 270 271 through one end of said housing and has a cam plate 417/273 261 5 keyed thereto for rotation with the shaft. The second section, or piston carrier section is comprised of a moldable plastic material having a plurality of modular 6] References cued units embedded therein. Each of the modular units in- UNITED STATES PATENTS cludes a cylinder for slidably receiving a piston, an out- 2,9l3,993 5/1959 TOUImlIl, Jr. l l l 91/488 put check valve unit integrally attached to aid cylin- 219971956 8/1961 SeYvarLm 92/171 X der, and a bypass check valve unit integrally attached U37 5/1970 to and offset from said output check valve unit. An outamps" 53 4 X put manifold and a bypass contro] manifold are cong nected to the output check valve unit and the bypass FOREIGN PATENTS OR APPLICATIONS check valve unit respectively of each modular unit. 189,648 12/1922 Great Britain 417/269 339,272 11 1930 Great Britain 417/269 9 Clam, 9 Drawmg Figures /0 y /4 r 1L r A a 1 PAIENIED JUL 1 1 I915 l/V VENTOI? ART/was. BRADLEY AT UR/VEY PAIENYEUJUL 1 11913v SHEET U 0F 4 INVENTOI? ARTHUR 3 BRADLEY awyw , 4 TORNEY HYDRAULIC PUMP This invention relates to a hydraulic pump and more specifically to a particular arrangement of the pump elements and the method of assembling the elements and forming the housing therefor. This invention is equally adaptable to hydraulic motors as well as to hydraulic pumps; however, for purposes of illustration, the description herein will be directed toward a pump embodiment.

This invention will be described with regard to a hydraulic pump of the type described in copending application Ser. No. 20,875, filed Mar. 27, 1970, by Hamish A. G. Cattanach, entitled VARIABLE PRESSURE SENSITIVE PUMP. Each cylinder of this pump is provided with a bypass to tank adjacent its output end. The bypass is provided with a valve which is automatically controlled by a fluid pressure control signal to vary the amount of cylinder output shunted through the bypass to tank. More particularly, the valve employed in the bypass is similar to a velocity fuse and the outflow of fluid from the cylinder during the power stroke of the piston will tend to seat the valve which is opened during the suction stroke. A control pressure tends to open the valve by acting on a piston or the like attached to the valve. In a sense, the control pressure acts as a biasing force, and the greater the pressure the more force is required to seat the valve. By regulating the control pressure, the length of time the valve is held open during thepiston stroke is varied. The output of the pump is inversely proportional to the change in control pressure since the bypass valve stays open longer with a rise in the control pressure.

In pumps wherein the cam plate is rotatable relative to a fixed piston-carrier section, the valves, passageways, manifolds, cylinders and bypass chambers, are machined out of a solid block of steel, or, at the best, the piston carrying section of the pump is divided axially into a plurality of sections which are machined individually to provide the necessary interconnecting fluid passageways, grooves, cylinder chambers, check valve housing, outlets and any other elements of fluid handling systems that go to make up the total piston carrying and fluid output control section.

Not only is this method of forming this section of the pump quite time consuming and, therefore, quite expensive, it also lends itself to inconsistencies or inaccuracies from pump to pump. Further, this type pump is not adaptable readily for manufacture under assembly line principles wherein standardized parts are assembled in automated fashion.

Further, there is great wastage of materials due to the number of borings and machings necessary to form cylinders, bores, manifolds, etc. This is compounded by the fact that many borings are in fact functionally unnecessary'for the successful operation of the pump but are necessary for the production and assembly of other components interiorly of the piston carrying assembly.

It is an objective of this invention to provide a pump wherein a major portion thereof is formed of standardized modular units which enables the pump to be manufactured at locations remote from the factory.

It is an objective of this invention to provide a modular unit for the piston carrying assembly of a hydraulic pump comprising, a cylinder for slidably receiving a piston, an output check valve unit which is integrally joined to and communicating with the cylinder, and a bypass unit joined to the output check valve unit. A

plurality of the modular units are positioned in circular configuration in a mold and are joined by a circular output manifold. The modular units are then encased in a plastic material which not only serves to hold the component parts together but also forms a portion of the pump housing.

More particularly, the pump of this invention comprises a housing divided into first and second sections with the first section having a closed end and an open end and defining a chamber. A rotatable shaft extends axially and centrally into the chamber of the first section and through an opening in said! closed end. A rotatable cam plate is positioned within said chamber and is keyed to said shaft for rotation therewith. The second section of said housing is of a molded plastic material having connecting means at one end thereof for connecting the second section to the first section of the pump housing. The second section includes a plurality of axially extending parallel cylinders or tubes embedded in the plastic material and opening into the cham her at the point of attachment of the first section to the second section. The pistons are slidably received in the cylinders with the ends thereof being in engagement with the cam plate. An outlet check-valve unit isintegrally attached to each of the cylinders and forms a standardized modular unit therewith. A plurality of the modular units are embedded in the plastic material in a circular pattern. A circular outlet manifold connects each of the outlet check-valve units. If desired, bypass units may be integrally attached to each of the outlet check-valve units, which bypass units include valves suitably operated as described earlier herein by a control pressure to selectively shunt a portion of the output of each of the cylinders to reservoir. The cylinder, out put check valve unit and bypass unit form the complete modular unit which is embedded in the plastic material. Whether incorporating a bypass unit or not, the result is a pump that can be easily and readily assembled using standardized units preformed at the factory. The need for time-consuming and laborious machining and boring of steel stock is thereby eliminated resulting not only in a savings in materials but also in the production of more uniform pumps.

These and other objectives of the invention will become more apparent to those skilled in the art by refer ence to the following detailed description when viewed in light of the accompanying drawings wherein:

FIG. 1 is a perspective view of the pump of this invention;

FIG. 2 is a cross sectional view taken along lines 22 of FIG. 1;

FIG. 3 is an exploded view in perspective of the components which make up the piston carrier section of the pump of this invention;

FIG. 4 is an exploded view in perspective showing the components of FIG. 3 in assembled relationship prior Referring now to the drawing wherein like numerals indicate like parts, the pump of this invention is generally indicated by the numeral and includes a housing having a first section 12 and a second section or piston carrying section 14. The first section 12 is of conventional construction and includes a housing 16 having an open end 18 and a closed end 20. A rotatable shaft 22 connected to any suitable drive means extends through the closed end and centrally and axially into chamber 24. A cam plate 26 is keyed to the shaft and rotates therewith. An inlet 28 communicates the chamber 24 with a reservoir of hydraulic fluid.

As mentioned earlier, in the prior art, the piston carrying section of a pump generally comprises steel stock bored for piston receiving cylinders and fluid communicating passageways. The piston carrying assembly of this invention includes a plurality of modular units 30a through 30d best seen in FIG. 3. Of course, it is understood that any number of modular units can be employed in the pump depending on the number of pistons in the pump. Each of the modular units comprises, as best seen in FIGS. 8 and 9, a cylinder 32 defining a piston receiving chamber 34. The cylinder 32 is of suitable tubular stock able to withstand the high pressures and temperatures encountered during the operation of the pump.

lntegrally attached to the cylinder 32 is an output check valve unit generally indicated by the numeral 36. The unit 36 includes an annular protuberance 39 which is telescopically received in one end of the cylinder 32'. The unit can be joined to the cylinder by welding or by any other suitable bonding means such that the unit 36 and cylinder 32 form an integral modular unit.

The output check valve unit is provided with an output passageway 38 having an inlet end 40 and an outlet end 42. Positioned across the passageway is a check valve 44 comprising a ball 46 normally urged to the seated position on valve seat 48 by means of spring 50. A spider 52 is telescopically received in the output passageway 38 and includes a projection 54 extending in the direction of the ball valve. The projection 54 serves as a stop to limit the backward or rearward movement of the ball when it is unseated by the pressure of fluid exiting from the cylinder during the power stroke of the piston. The spider 52 includes a rearwardly extending skirt 56 which extends beyond the body portion 58 of the unit 36 a slight distance to provide a nipple or protuberance 42. As will be described later in the specification, the protuberance 42 is telescopically received in an aperture in an output manifold to which each of the modular units is connected.

The modular unit can comprise only the cylinder and the output valve units. However, it may be desirable to provide means for controlling the output of the pump by means of a control bypass unit generally indicated by the numeral 60. A pump of the type wherein a bypass is controlled by a control pressure signal to vary the output of a pump is set forth in assignees copending application Ser. No. 20,875 filed Mar. 27, 1970, by Hamish A. G. Cattanach, entitled VARIABLE PRES- SURE SENSTIVE PUMP. The bypass unit 60 includes a bypass passageway 62 which is communicated with the output passageway 38 by means of passageway 64 defined by slanted openings 66 and 68 in adjacent side walls of the output valve unit and the bypass unit. The sub-units are each hexagonal in cross section and are joined together at abutting flat sides by welding or the like.

A port 70 is provided in a side wall in the unit 60 and communicates with a central axially extending passageway which leads to the reservoir, which axially extending passageway will be described in greater detail later herein. The aperture 70 is provided at one end of the bypass passageway 62 remote from the end adjacent to the passageway 64. Extending across the passageway 62 is a velocity fuse or valve 72 which is normally urged to its seated position on seat 74 by means of spring 76. The spring 76 is mounted on a spring stop 78 which also serves as an end plug for the axial passageway 62.

A control piston 80 is slidably received in the portion 82 of the passageway 62 and includes a piston rod 84 extending from one end thereof towards the ball 73. One end of the unit 60 is machined to define a nipple 86, which telescopically receives a fitting 88 is counterbore 90. The fitting 88 is provided with an axially extending restricted passageway 92 and includes a nipple or protuberance 94 which is received by apertures in a control pressure manifold which join each of the bypass units as will be described below.

Referring now to FIG. 3, a control pressure manifold 98 is provided with apertures 96 for receiving the nipples 94 of the bypass units, and an inlet 100 which is in communication with a suitable control pressure source. The control pressure is transmitted to the area of the bore 82 behind the control piston 80 causing the piston to move toward the left to unseat the ball 73. During the power stroke of the piston, the fluid will tend to follow the path of least resistance through passageway 64 past ball 73 in passageway 62 and out through aperture 70 to tank. The pressure will also tend to seat the ball 73 as is well known in the operation of velocity fuses. However, the seating of the ball will be delayed proportionally in accordance with the degree of the control pressure exerted against the piston 80. In other words, the greater the control pressure, the longer the ball 73 will remain unseated. In that way, the output of the pump will be lessened since more of the fluid will return to tank through the bypass. It is to be understood that the control pressure is very low in comparison to the pressures generated in the cylinder 32 during the power stroke of the piston. However, due to the varied sizes of the working surfaces, the pressure can be raised to a sufficient level to keep the ball of of its seat against the pressure of the fluid from the cylinder 32 for a portion of the power stroke.

The modular units are assembled in the manner shown in FIG. 3. An output manifold 104 is provided with an outlet 106 and an outlet fitting 108 which is seated on the outlet 106. The outlet 108 is the main outlet of the pump. The manifold 104 is circular in configuration and defines an annular chamber therein and may be manufactured by welding together two circular halves having annular grooves therein. The manifold is provided with a plurality of apertures 110 which receive the protuberances 42 of the output units 36. The modular units 30a 30d, when assembled to the manifold, will be disposed in a circular pattern and are further held in spaced relationship by means of spacer block 112. The modular units are oriented about the longitudinal axis of the cylinders 32 in the manner shown in the end view of FIG. 5 whereby the same flat side of each hexagonal bypass unit is in surface contact with the rectangular spacer block and the

nipples

94 and 42 are positioned in concentric circular patterns coincidental with the concentrically disposed manifolds. lt is to be noted, however, that the manifold 98, which is of a lesser diameter than that of manifold 104, is not wholly disposed within the output manifold 104, and in this regard the nipples 94 protrude somewhat beyond the plane in which the outer ends of the protuberances or nipples 42 lie.

As mentioned earlier, the output manifold 104 is provided with an outlet 106 having outlet fitting 108 joined thereon. The outlet 108 is provided at its inner end with a polygonal flange 114. The inlet 100 of the control pressure manifold 98 is provided with an inlet fitting 116 which is likewise provided with a polygonal flange 118. Each of the

fittings

108 and 116 are provided with nipples like that shown on fitting l 16 and identified by numeral 120 which are telescopically received in the

openings

106 and 100 respectively of the

manifolds

104 and 98. A third fitting 122 also. having a polygonal flange 124 and a protuberance or nipple 126 is telescopically received in the central opening 128 of the control pressure manifold 98 in a manner to be more fully explained later in this application. The fitting 122 communicates a central passageway or cavity 130, best seen in FIG. 6, with the reservoir of hydraulic fluid. The cavity is defined in part by the inwardly directed side walls of the hexagonal bypass units 60 and the end wall is defined by the spacer block 112. The other end, is provided with fitting 122. The apertures 70 of the bypass units, earlier referred to in the description of FIG. 9, communicate with the central passageway 130. Thereby, fluid entering a bypass unit and flowing past the velocity fuse 72 will exit from the pump through the aperture 70, the central passageway or cavity 130 and the fitting 122. As will be seen, the sidewalls of the central passageway are not only defined by the side walls of the units 60 but are also defined and rendered watertight by means of a moldable mass in which the modular units 30a 30d and the manifolds are embedded.

Referring now to FIG. 4, the modular unit is shown in assembled relationship on the manifolds. The outer ends or open ends of the cylinders 32 are then inserted in axially extending apertures 132 in a connector plate 134. The connector plate is of a suitable heavy-duty metal. As will be pointed out later, the connector plate is used to connect the piston carrying section of the pump to the cam plate carrying section or first section of the pump.

Once the connector plate has been suitable joined by welding or the like to the standardized modularized units and, more specifically to the outer ends of the cylinder 32, the entire joined assembly is placed in a mold 136 as shown in FIG. 7. It is to be understood that any particular molding technique can be used. The mold as shown in FIG. 7 is a two-part mold with cutouts being provided in the mating halves to define an aperture for receiving the outlet fitting 108. The mold defines a mold cavity about the assembled component parts of the piston carrying assembly of the pump into which plastic molding material or the like such as epoxy resin is poured. The molding material completely encapsulates those elements of the pump within the mold cavity, with the exception of the outer parts of the fittings attached to the manifolds. As mentioned earlier, the molding material helps define and render fluid-tight the central passageway or cavity 130. A removable tubular mold element, not shown, is connected to form thecavity during the molding process. The manifold 98 must be removed, of course, to allow for the insertion and removal of the mold elements. After the plastic material has set, not only are the respective components held immovable in assembled relationship, but the plastic material forms the housing 138 of the piston-carrying assembly 14 of the pump as best seen in FIGS. 1 and 2. Thereafter, pistons 140 are inserted in the cylinders 32 and the piston carrying assembly 14 is joined to the cam plate carrying section of the pump by means of the connector plate 134 and suitable threaded fasteners 142 inserted through apertures peripherally spaced about the outer periphery of the connector plate.

In operation, a suitable drive means drives the rotatable cam plate 26, the surface of which is engaged by the pistons 140. Hydraulic fluid from a suitable source enters the chamber 24 through inlet 28 and is sucked into piston chamber 34 not only through conventional openings in the ends of the pistons but through the by pass units 60. If the control pressure in the chamber 102 is insufficient to unseat the ball 73, the entire output of the cylinder will be pumped past the checkvalve 44 and to the output manifold 104. It is to be understood that though the control pressure may be zero, the ball 73 may unseat somewhat during the suction stroke of the piston due to the suction forces. However, it will immediately seat upon decrease in the suction pressure due to the force of the spring 76. If the control pressure is raised in chamber 102, the'piston '80 will unseat the ball 73 and the ball will stay unseated for a certain duration of the piston stroke whereby a portion of the hydraulic fluid from the chamber 34, seeking the path of least resistance, will flow past the velocity fuse 72 and I through aperture 70 to tank. The level of the control signal pressure in chamber 102 controls the length of time that the ball 73 remains unseated and, therefore, controls the amount of fluid to go to tank.

The modular units 30 may be manufactured with or without the bypass units and sold as part of a standardized kit for assembly at a remote point. If, of course, can easily be seen that the use of standardized'modular parts leads to more inexpensive and more accurate assembly techniques not heretofore known in the art. Further, there is a substantial saving in materials in that the prior art required the machining of rather expensive steel stock and substantial wastage thereof due to the machining, while the pump of the instant invention uses relatively inexpensive durable plastic materials. The component parts lend themselves to assembly line technique of manufacture and once the parts have been made, the actual assembly thereof is a relatively simple matter involving an inexpensive and relatively uncomplicated molding step.

Further, this invention has been described with respect to a hydraulic pump although it is to be under-- stood that it can also be used with hydraulic motors. Further, it is to be understood that the techniques of this invention involving modular standardized unit con cepts and molding plastic housings are not limited to any particular type of pump. The invention herein has been described with respect to a particular type pump made in the arrangement, disposition, and form of the parts without departing from the principle of the present invention as comprehended within the scope of the accompanying claims.

I claim:

1. A hydraulic pump comprising a first housing section having a closed end and an open end and defining a chamber, a rotatable shaft extending axially and centrally into said chamber through an opening in said closed end, a rotatable cam plate within said chamber and keyed to said shaft for rotation therewith, a molded plastic second housing section attached at one end to said open end of said first housing, a plurality of axially extending parallel cylinders embedded in said plastic material defining said housing and opening into said chamber, a self-contained outlet valve assembly defining an outlet passageway attached to and communicating with each of said cylinders, pistons slidably received in said cylinders with the ends thereof engaging said cam plate, whereby upon rotation of said cam plate, said pistons reciprocate within said cylinders, and inlet means and outlet means for said pump.

2. The pump of claim 1 and including an outlet manifold embedded in said second housing section having an outlet port and communicating each of said outlet passageways with said outlet port.

3. The pump of claim 3 further including a selfcontained, enclosed bypass unit embedded in said first housing section'and attached to said valve assemblies and defining a passageway communicating at one end with said bypass unit intermediate said passageway and a valve seat for said valve, said valve being disposed such that the pressure of said output tends to seat said valve, and control means responsive to a hydraulic control pressure for adjustably maintaining said valve in the unseated position for a predetermined portion of said output stroke whereby a portion of said fluid output is bypassed to the reservoir.

4. The pump of claim 3 wherein said control means includes a control piston slidably mounted in a control cylinder coaxial with said passageway in said bypass unit, said control piston having an end thereof in engagement with said valve and the other end exposed to a pressure chamber defined by said control cylinder and said control piston, and a control pressure manifold communicating the pressure chambers of each of said bypass units with a source of control pressure, whereby upon increasing the pressure in said control chamber said piston is caused to unseat said valve.

5. The pump of claim 3 wherein said output valve assemblies and bypass units are elongated and polygonal in cross section and have flat, elongated sides and are joined to each other along a pair of adjacent flat'sides.

6. The pump of claim 4 wherein the longitudinal axes of said output valve assemblies lie on a circle and the longitudinal axes of said bypass units lie on a second circle concentric with said first circle and of smaller diameter.

7. The pump of claim 6 wherein said output manifold is an annular hollow ring and said control signal manifold is an annular hollow ring of a smaller diameter than that of said output manifold.

8. In a hydraulic pump of the type having a housing defining a chamber, a shaft extending axially and centrally into said chamber through said housing, a cam plate within said housing and axially extending parallel pistons slidably received in cylinders in a piston carrier in said housing with the ends thereof in engagement with said cam plate whereby said pistons are caused to reciprocate upon relative rotation between said carrier and said cam plate, the improvement comprising, a plurality of unitary cylinder and valve assemblies each comprising a first section defining a cylinder for slidably receiving a piston, a second self-contained, enclosed section integrally attached to said first section and defining an outlet passageway communicating with said cylinder, a check valve in said passageway normally biased to the closed position and adapted to unseat during the power stroke of said piston, and a third self-contained, enclosed section offset from said second section and defining a bypass passageway leading to reservoir, a shunt passageway connecting said bypass passageway with said cylinder, valve means in said bypass passageway and means for selectively opening said valve whereby the output of said piston can be varied by selectively opening said valve in said bypass passageway.

9. The pump of claim 8 wherein said unitary assemblies are embedded in a molded plastic material which forms a part of said housing.

Claims

3. The pump of claim 3 further including a self-Contained, enclosed bypass unit embedded in said first housing section and attached to said valve assemblies and defining a passageway communicating at one end with said bypass unit intermediate said passageway and a valve seat for said valve, said valve being disposed such that the pressure of said output tends to seat said valve, and control means responsive to a hydraulic control pressure for adjustably maintaining said valve in the unseated position for a predetermined portion of said output stroke whereby a portion of said fluid output is bypassed to the reservoir.

5. The pump of claim 3 wherein said output valve assemblies and bypass units are elongated and polygonal in cross section and have flat, elongated sides and are joined to each other along a pair of adjacent flat sides.