US3775027A

US3775027A - Two-speed pump

Info

Publication number: US3775027A
Application number: US00185528A
Authority: US
Inventors: R Craft
Original assignee: Gray Manufacturing Co Inc
Current assignee: Gray Automotive Products Co
Priority date: 1971-10-01
Filing date: 1971-10-01
Publication date: 1973-11-27
Anticipated expiration: 1990-11-27
Also published as: JPS558920B2; CA962553A; JPS4842271A

Abstract

A stepped displacement fluid pump having a plurality of piston members reciprocable individually or in common within a single fluid chamber to displace fluid from the chamber at different rates proportional to the sum of the exposed surface areas of those piston members reciprocating in common. Coupling means carried on the piston members selectively interconnect and disconnect the piston members in different stages of operation of the device in response either to positioning the piston members at predetermined locations relative to one another or in response to the pressure of fluid in the chamber.

Description

United States Patent [191 Craft Nov. 27, 1973 TWO-SPEED PUMP Inventor: Roger L. Craft, St. Joseph, Mo.

[73] Assignee: Gray Manufacturing Company,

Inc., St. Joseph, Mo.

[22] Filed: Oct. 1, 1971 [2]] Appl. No.:,l85,528

[52] US. Cl 417/214, 60/477, 60/486, 417/487 [51] Int. Cl. F04b 19/00 [58] Field of Search 60/52 HA, 52 118, 60/477, 486; 417/212, 214, 486, 487

[561' References Cited UNITED STATES PATENTS 3,112,705 12/1963 Chlebowski 60/52 HA X 1,263,401 4/1918 Fraser 417/487 2,185,264 l/l940 Mistral 60/52 HA 2,703,191 3/1955 Jernander 417/487 X 2,050,000 8/1936 Frost 60/52 HB 2,370,681 3/1945 Mueller 60/52 HB FOREIGN PATENTS OR APPLICATIONS 181,586 10/1966 U.S.S.R 417/487 Primary Examiner-C. J. Husar Assistant Examiner-Leonard Smith Attorney-Schmidt, Johnson, Hovey & Williams [57] ABSTRACT A stepped displacement fluid pump having a plurality of piston members reciprocable individually or in common within a single fluid chamber to displace fluid from the chamber at different rates proportional to the sum of the exposed surface areas of those piston members reciprocating in common. Coupling means carried on the piston members selectively interconnect and disconnect the piston members in different stages of operation of the device in response either to positioning the piston members at predetermined locations relative to one another or in response to the pressure of fluid in the chamber.

16 Claims, 9 Drawing Figures PAIENIEBHUVZ'! I975 3.775.027 sum 1 or 2 INVENTOR. Roger L. Craff I BY TWO-SPEED PUMP This invention relates generally to fluid power systems and, more particularly, to fluid devices capable of displacing motive fluid at different rates without altering the speed or stroke length of the device.

Certain applications of the use of fluid power systems ideally demand that motive fluid flow be supplied at different combinations of flow rates and pressures. For instance, when the hydraulic actuator of the system is encountering minimal resistance to its movement, it is often desirable to deliver fluid at high flow rates in order to drive the actuator at high speeds. Power limitations, however, preclude such high speed operation when the actuator encounters a heavy load. In this latter instance substantial pressures must be built up to drive the actuator, and fluid must necessarily be delivered at a far slower rate in order to remain within the particular power limitations of the system. By providing a system capable of delivering fluid selectively at high or low rates of flow, the power input and effort required to deliver the motive fluid can be maintained at a relatively low level, while drastically altering the operating speed and force output of the actuator to match the changing resistance encountered.

A typical example of such a system is a hydraulically powered lifting jack which travels unhindered through a substantial portion of its stroke before engaging a heavy object to be lifted. A two-stage hydraulic system as described above, will drive the jack at low pressures and high speeds when unloaded, and will drive the jack at slower speeds and higher pressures after the object is engaged. Jack cycling speed is, therefore, maximized without limiting the lifting capabilities of the jack; yet, the effort required to supply motive fluid and operate the jack remains at a level that is amenable to direct operation by a limited manual force.

One prior form of such a hydraulic system capable of operating at multiple combinations of speeds and pressures, contemplates a pair of separately operated piston type pumps delivering fluid to the actuator in different stages. The volume of fluid displaced by each pump is equal to the effective cross-sectional working area of its pumping elementexposed to the fluid, multiplied by the stroke length of the pumping element. One pump is sized to deliver a high volume of motive fluid to the actuator and functions while the actuator in unloaded; the other pump has smaller displacement, either a shorter stroke length or smaller exposed piston working area, to deliver a relatively small volume of fluid and functions when the actuator encounters heavy resistance. Such arrangement, of course, requires duplicate fluid pressure feed systems and pump operating handle members, as well asadditional hydraulic controls that efl'ect operation of the proper pump during each stage of operation.

Another prior art form of a multiple speed fluid power system incorporates a pair of separate pumps which are operated in tandem in all stages of pump operation. A low pressure relief valve in the output flow of one of the pumps opens whenever heavy resistance is encountered and high pressure developes to relieve and divert fluid displaced from that pump to a reservoir so that only fluid from the other non-relieved pump performs work on the actuator during a slower speed operating stage. The displacement of the two pumps effectively add together when operating in tandem to drive the actuator at high speed, thereby reducing the necessary size of at least one of the pumps. A single operating handle is operably included to drive the pumps in equal stroke lengths so that the work performed by the displaced fluid is directly proportional to the sum of the working areas of the pumps during tandem operation, and is directly proportional only to the working area of the non-relieved pump during the slow speed operating stage. While this tandem arranged is somewhat simpler than the separate pump system above described, it still incorporates a number of duplicate, likefunctioning elements. In addition, this type of arrangement has an inherent inefficiency in that fluid displaced from the relieved pump performs useful work during only the high speed stage of operation of the system, while effort expended in displacing that fluid during the low speed stage of operation is completely wasted.

It would be highly advantageous, therefore, to provide a single fluid device capable of delivering fluid at various combinations of pressures and rates of flow wherein all fluid displaced from the device performs useful work.

Accordingly, it is an important object of the present invention to provide a staged operating fluid device capable of displacing fluid at different flow rates in response to different pressures of the fluid delivered wherein all of the fluid displaced during all stages of operation performs useful work in order to minimize inefficient energy loss by the device.

Another important object of the invention is to provide a fluid device having a fluid chamber and piston means movable therein for displacing fluid therefrom to a single discharge duct directing the fluid through external circuitry to perform useful work, wherein the piston means include separate pistons movable individually or in common in the chamber to vary the exposed working area of the piston means in relation to the number of commonly moving pistons so that flow through the single discharge duct may be altered in corresponding stages without inducing substantial energy loss and without requiring incorporation of a multiplicityof like functioning elements.

Another object of the present invention is to provide a reciprocating piston pump having piston means including a primary working piston movable in a fluid chamber to displace fluid therefrom, and an accessory working piston that can be selectively coupled to the primary piston to increase the effective working area of the piston means when coupled, so that the pump displaces a higher rate of fluid when the pistons are coupled than when uncoupled without requiring alteration of the stroke length of the pump or speed of operation of same.

A more particular object of the invention is to provide a pump constructed in accordance with the preceding object and further provided with pressure responsive coupling means which are engageable with the primary and accessory pistons to couple same when the pressure of motive fluid in the chamber is below a predetermined level so that the pump can displace said high rate of fluid flow at low pressures in a first operational mode, said pressure responsive coupling means being operable to automatically disengage and uncouple the pistons during movement of the primary piston while chamber pressure is above the predetermined level so that the pump displaces a low rate of fluid flow at high pressures in a second operational mode.

Another important object of the invention is to provide a fluid device as constructed in accordance with any of the preceding objects that further includes sealing means operable to seal both statically and dynamically between the relative moving pumping members, and between the walls of the fluid chamber and the piston means, in order to prevent fluid leakage from the chamber during all operational modes of the device.

A more particular object of the invention is to provide a pump constructed in accordance with the preceding object which utilizes a unitary seal member that effects both the sealing between the several piston members, as well as the sealing between the chamber walls and the piston means, in order to avoid inclusion within the device of a multiplicity of similarly functioning sealing pump components.

Another important object of the invention is to provide a reciprocating piston pump having a primary working piston and an accessory working piston selectively movable in common with the primary working piston to displace fluid at different rates when coupled and uncoupled, and position responsive coupling means selectively interconnecting the primary and accessory pistons upon positioning same in a predetermined coupling position relative to one another to displace fluid in direct proportion to the sum of the exposed working areas of the primary and accessory pistons, said coupling means being operable to disengage upon moving one of the pistons away from said relative coupling position to permit the latter piston to reciprocate alone and displace fluid in direct proportion to its working area so that the displacement capability of the pump changes as the coupling means engage and disengage.

A further object of the invention is to provide a piston pump constructed in accordance with the preceding object wherein said position responsive coupling means are also responsive to the pressure of motive fluid displaced by the pump in such a manner as to automatically disengage during movement of said one piston in response to a rise in pressure above a predetermined level to permit said reciprocation of the one piston alone in order to automatically reduce the effort required to operate the pump at high pressures.

These and other objects and advantages of the present invention are specifically set forth in or will become apparent from the following detailed description of a preferred embodiment of the invention and several modifications thereof, together with the accompanying drawings, wherein:

FIG. 1 is an elevational view of a hydraulically operated lifting jack provided with an actuating fluid pump constructed in accordance with the present invention;

FIG. 2 is a top elevational view of the actuator assembly mounting block with the pump and actuator removed;

FIG. 3 is a longitudinal, cross-sectional view of the mounting block taken along line 33 of FIG. 2;

FIG. 4 is a longitudinal, cross-sectional view taken along line 44 of FIG. 2 showing the mounting block and actuator assembly;

FIG. 5 is a longitudinal, cross-sectional view taken generally along line 5-5 of FIG. 2 showing the mounting block and improved pump;

FIG. 6 is a longitudinal, cross-sectional view of a modified form of the fluid device as contemplated by the invention;

FIG. 7 is a longitudinal, cross-sectional view similar to FIG. 6 of still another modified form of the present invention;

FIG. 8 is a longitudinal, cross-sectional view of yet another modified form of the invention and illustrating the low volume mode of operation thereof; and

FIG. 9 is a view similar to FIG. 8 illustrating the high volume mode of operation.

FIGS. 1-5 illustrate a lifting jack assembly 10 having an integrally carried fluid power system which includes a fluid device in the form of a supply pump 12, constructed in accordance with the present invention. The fluid power system also includes a ram-type hydraulic actuator assembly 14 that is supplied with fluid from pump 12 to operate the jack. The overall construction and operation of the jack assembly and fluid power system will be first described.

The jack assembly 10 has a scissors frame composed of crossed, pivotally interconnected

arms

16 and 18 which respectively open and close in scissors-like action to effect raising and lowering of the frame arm 16. A lifting pad 20 is provided at the upper end of arm 16 so as to liftingly engage and disengage a vehicle or other heavy object as the

arms

16 and 18 rotate in opposite directions about frame pivot 22.

The fluid power system is pivotally connected to frame arm 18 at pivot 26 and pivotally connected to frame arm 16 at pivot 28. A mounting block 30 carries the supply pump 12 and actuator assembly 14 as a unit in fixed relationship to the jack frame through its connection at pivot 26 to frame arm 18, while the outer end of a ram 32 depending out of the actuator assembly 14 is mounted on frame arm 16 by pivot 28. During operation of the jack, ram 32 is driven outwardly and downwardly with respect to FIGS. 1 and 4 to effect raising of lift pad 20, and retracts back into actuator assembly 14 to effect opposite rotation of the frame arms to lower the lift pad.

The actuator. assembly 14 includes an external, longitudinal cylinder 42 affixed upon the upper face 31 of the mounting block 30 and an inner cylinder 44 concentrically arranged with respect to the external cylinder 42 and threadably secured to the mounting block 30 at a through bore 34 therein. An end cap 46 is rigidly secured to the upper end of inner cylinder 44 and sealingly engages the walls of external cylinder 42 so as to form the upper ends of both cylinders 42 and 44. The inner cylinder 44 has an internal, longitudinal fluid working chamber 48, while the concentric cylinders 42 and 44 define an annular reservoir chamber 50 therebetween disposed concentrically to the actuator working chamber 48. The end cap 46 is provided with an internal passage 52 communicating with the internal working chamber 48 and annular reservoir chamber 50, with portions of internal passage 52 extending through a valve body 54 affixed within end cap 46. The outer cylinder 42 has a removable plug 72 facilitating the filling of the fluid reservoir chamber 50.

A valve stem 56 is threadably received within valve body 54 and has a manually operable knob 58 secured thereto. Upon rotation of knob 58, a needle valve 60 carried at the inner end of valve stem 56 is driven between positions blocking and permitting flow through internal passage 52. Needle valve 60 acts as a manual pressure release valve, blocking communication between low pressure reservoir 50 and working chamber 48 in the position shown in FIG. 4 to permit pressurization of chamber 48 and operation of the actuator. When moved away from its non-flow blocking position, needle valve 60 permits return fluid flow from working chamber 48 to low pressure reservoir 50 to allow retraction of ram 32.

Ram 32 is received within working chamber 48 to'be responsive to the pressure of motive fluid therein. A bearing guide 62 at the inner end of ram 32 cooperates with the inner wall of cylinder 48 to guide the ram in longitudinal reciprocation within chamber 48. Sealing means 64 at the lower end of mounting block 30 in the area of bore 34 cooperate with ram 32 to prevent fluid leakage from working chamber 48. Ram 32 is slightly smaller than bore 34 to assure constant fluid communication of the latter with the fluid chamber 48 proper. Ram bearing guide 62 has a plurality of passages 66 extending therethrough to interconnect the portion 68 of working chamber 48 disposed between the upper end surface of bearing guide 62 and end cap 46, with the annular portion 70 of working chamber 48 defined between the main body of ram 32 and the internal wall of cylinder 44. Upon introduction of pressure fluid flow into chamber 48, pressure therein acts upon the upper surface of bearing guide 62 to force ram 32 outwardly and downwardly from working chamber 48. During retraction of ram 32, fluid is displaced from working chamber 48 across the opened needle valve 60 through internal passage 52 to low pressure reservoir chamber 50.

Pump 12 (described in greater detail below) has a housing 74 secured to mounting block 30, and an actuator rod member 76 with an inner end disposed within an internal longitudinal fluid chamber 78 formed as a constant diameter bore in housing 74. A duct 80 connects the fluid chamber 78 with a passage 82 in mounting block 30. Passage 82, in turn, communicates with separate fluid inlet and

outlet passages

84 and 86. A one-way inlet check valve 36 intercepts inlet passage 84 and is spring-biased to a closed position shown in FIG. 5, blocking communication from inlet passage 84 to passage 82. A one-way outlet check valve 38 disposed in outlet passage 86 is similarly biased to its closed position, blocking flow from passage 82 to outlet passage 86. Inlet passage 84 extends to the upper face 31 of mounting block 30 to communicate with annular reservoir chamber 50, and outlet passage 86 opens into bore 34 of mounting block 30 so as to communicate with actuator working chamber 48 at all times.

General operation of the jack assembly proceeds as follows. Upon upward, suction stroke travel of actuator rod member 76, pressure in chamber 78 and passage 82 drops to a very low level permitting inlet check valve 36 to move to an open position in opposition to its spring-bias so tthat fluid may be drawn from annular reservoir 50 through inlet passage 84 to pump fluid chamber 78. Upon downward travel of actuator rod member 76, pressure increases sufficiently to close inlet check valve 36 and overcome the bias of outlet check valve 38 and effect opening of same. Fluid displaced from pump chamber 78 is accordingly across outlet check valve 38 to outlet passage 86 and the actuator working chamber 48. A separate pressure relief passage 88, shown in FIG. 3, extends between through bore 34 and the upper face 31 of mounting block 30 to permit selective communication between actuator working chamber 48 and annular reservoir 50. A high pressure relief valve 40 of conventional structure, in-

tercepts relief passage 88 to permit flow therethrough only when excessive pressure develops within working chamber 48 in order to protect the actuator from over-pressurization and resultant injury thereto.

The jack is operated in a power-lifting stroke by pumping handle 24 to repeatedly cycle pump actuator rod member 76 pivotally connected thereto by a connecting link 90. The pump alternately draws fluid from reservoir chamber 50 from inlet passage 84 and pumps the same through outlet passage 86 to actuator working chamber 48 to move ram 32 downwardly a short distance to a new position upon each cycle of the handle and rod member 76. Outlet check valve 38 prevents reverse flow from working chamber 48 during the pump suction stroke to hold the ram in its new position while awaiting the next pumping stroke. The

jack frame arms

16 and 18 rotate in a scissors opening movement about frame pivot 22 to raise lifting pad 20 and the object engaged thereby.

To collapse the jack and lower the lift pad 20, valve knob 58 is rotated on drive needle valve upwardly and clear end cap passage 52. The load experienced by ram 32 drives it upwardly in work chamber 48 to displace fluid therefrom through cleared passage 52 to reservoir 50. Ram 32 thus retracts back into cylinder 44 to lower liftpad 20 and collapse the jack frame. The ram may be held in a desired position by moving needle valve 60 to its closed position to isolate working chamber 48 and hydraulically lock ram 32.

Turning now particularly to the improved fluid pump 12 which is the subject of the present invention, pump 12 has a centrally located rod pumping member 76 of substantially smaller diameter than the constant diameter of the pump fluid working chamber 78. A seal pack comprising an elastomer seal 92 and rigid

backup washers

94 and 96, one of which is metallic, is disposed in the annular ring area defined between rod 76 and the cylindrical wall of chamber 78 to sealingly engage both rod 76 and the chamber wall. A tubular coupling sleeve is disposed within the internal chamber of housing 74 and extends between seal backup washer 96 and the upper end surface 102 of the housing interior chamber 78. Rod 76 has a pair of spaced, annular shoulders which carry a compressible detent ring 106 therebetween in sliding relationship to the interior surface of tubular sleeve 100. The tubular sleeve 100 has an indented ridge 108 near its upper end that protrudes inwardly into interfering relationship with compressible detent ring 106.

Whenever actuator rod 76 moves upwardly during its suction stroke, detent ring 106 will ultimately contact ridge 108, whereupon slightly greater force must be exerted to pull actuator rod 76 farther upwardly and simultaneously radially compress detent ring 106 to permit the latter to travel upwardly past sleeve ridge 108. When so located above ridge 108 in what may be termed a coupling position, detent ring 106 cooperates with the sleeve ridge to exert a downward force on sleeve 100 and seal 92, tending to carry the latter downwardly in common reciprocation with the rod. A snap ring shoulder 110 at the lower end of rod 76, contacts the bottom of seal 92 when detent ring 106 is located above ridge 108 in this coupling position to effect common upward reciprocation of the seal 92 and rod 76. Accordingly, when rod 76 is located in this coupling position relative to sleeve 100 and seal 92, the actuator rod 76 and seal 92 will reciprocate in common to displace fluid from chamber 78 at a rate directly proportional to the sum of the area of exposed working surface 112 of the rod, and the annular area of the lower exposed surface 114 of seal 92. It will be apparent that during such common reciprocation, fluid is displaced at a rate proportional to the entire diameter of chamber 78 in view of the sealing engagement of seal 92 with the walls 98 of chamber 78.

Rod 76 is also adapted to reciprocate alone within chamber 78 and relative to seal 92 while the latter remains in stationary relationship to housing 74. This operational mode of the pump is effected whenever the frictional securement between detent ring 106 and ridge 108 is broken and the detent ring 106 is positioned below ridge 108 in the manner depicted in FIG. 5. The outer surface of rod 76 slides upon the annular inner surface of seal 92 when reciprocating alone in chamber 78 in what may be termed the low speed-high pressure operating stage of pump 12. In this operating stage it will be apparent that only the exposed surface 1 12 of rod 76 is moving within chamber 78 so that fluid is displaced from the chamber at a rate directly proportional to the cross-sectional area of surface 112. A lesser volume of motive fluid is thereby displaced from the pump during each full stroke of rod 76 than is displaced when seal 92 reciprocates in common with rod 76. Though actuator ram 32 operates at a slower rate during this low volume operating mode, all effort expended by stroking handle 24 is concentrated upon the smaller fluid volume displaced, enabling this smaller volume to be displaced at a substantially higher pressure to create a correspondingly greater lifting force, all this without wasting effort expended on handle 24. The pump 12 is particularly adaptable to manual operation therefore, since a limited manual power input can effect rapid rise of lifting pad 20 when the same is unloaded by driving the rod 76 and seal 92 in common reciprocation, and since this limited input power can also be concentrated to deliver smaller volumes of higher pressure fluid to exert greater lifting force by driving only the rod 76 in reciprocation in fluid chamber 78. In the embodiment illustrated in FIG. 5, the crosssectional diameter of rod surface 112 is approximately one-half of the combined diameter of surfaces 112 and 114 so that the pump displacement is four times as great when rod 76 and seal 92 move in common reciprocation than when rod 76 reciprocates alone.

Whenever rod 76 is positioned in the coupling position described above, the frictional holding force exerted between compressible detent ring 106 and indented ridge 108 is effectively opposed by the hydraulic force created from pressure of fluid in chamber 78 exerted on seal 92 to resist downward travel of the latter. The magnitude of the frictional holding force exerted between detent ring 106 and ridge 108 is determined by the rigidity of detent ring 106 as well as the distance of radial interference between ridge 108 and detent ring 106, the latter distance factor controlling the amount of radial compression required of detent ring 106 in traveling across ridge 108. The pump 12 is constructed so that the hydraulic resisting force exerted upon seal 92 will exceed the frictional holding force of the detent ring whenever pressure within chamber 78 rises above a predetermined operating level. In the preferred embodiment this predetermined pressure level is of a magnitude representing engagement by pad 20 of a load to be lifted, i.e., whenever chamber pressure is below this predetermined level, the jack is unloaded and amenable to high speed operation; while upon engagement of a load, pressure in chamber 78 rises above this predetermined level.

Upon forcing actuator rod 76 downwardly in its power stroke while pressure in chamber 78 is above this predetermined level, the hydraulic resisting force overcomes the frictional intersecuring force tending to urge the sleeve and seal 92 downwardly. Accordingly, the seal and sleeve will remain in their upper positions illustrated in engagement with upper chamber end surface 102, and detent ring 106 will compress and travel across ridge 108 to uncouple the seal and rod upon forcing rod 76 downwardly in its power stroke. Rod 76 is thereby released to reciprocate along within the chamber 78 to effect the low speed-high pressure operational mode of the pump. In this manner, the rod is automatically uncoupled from sleeve 100 and seal 92 whenever the rod is stroked while pressure in chamber 78 is above the predetermined level and offering resistance greater than the frictional intersecuring force created by detent ring 106. Thus, for instance, if the jack comes into lifting contact with a heavy load during midstroke of rod 76, pressure in chamber 78 will instantly rise above the predetermined level and the detent ring will immediately uncouple to switch the pump to the low pressure-high flow operational mode and permit completion of the stroke.

Seal member 92 is operable to effect a static seal with rod 76 and to dynamically seal against the walls of fluid chamber 78 during common reciprocation with the rod, and is conversely operable to statically seal against the chamber walls and dynamically seal against the rod when the rod 76 reciprocates relative to seal 92. A conventional V-shaped lip elastomer seal with concentric, radially compressible lips at its inner and outer annular surfaces has been found quite suitable for use in the improved pump. The relatively rigid backup washers prevent extrusion of compressible seal 92 and provide sufficient support therefor to permit the seal pack to function as a pressure fluid displacing pumping member.

The rod 76 is reciprocable through a full stroke length delimited in one direction by engagement of upper shoulder 104 with upper chamber end surface 102, and delimited in the opposite direction by engagement of rod lower surface 112 with the lower end surface 116 of the fluid chamber 78. In the preferred form shown in FIG. 5, the ridge 108 and detent ring 106 are positioned respectively upon sleeve 100 and rod 76 relative to one another and to the chamber end surfaces 102 and 116 so as to permit the rod to travel throughout its full stroke length both when coupled and uncoupled from sleeve 100. Rod 76 is permitted slight overtravel in its upward suction stroke relative to the upward travel of sleeve 100 in order to move the coupling position described above; however, the rod is still movable substantially throughout its full stroke length either when reciprocating alone or in common with seal 92 since the rod must be moved essentially to the end of its stroke before reaching its coupling position.

The modified fluid pump illustrated in FIG. 7 incorporates a pair of concentrically arranged

piston elements

132 and 134 reciprocably disposed within an interior fluid chamber 138 of housing 140. Seals 156 are carried on

piston elements

132 and 134 to effect dynamic and static sealing between the pistons and between the outer piston 134 and the chamber walls. The

centrally disposed piston element 132 acts as the pump actuator rod and carries a compressible detent ring 142 movable to opposite sides of annular ridge 144 on the adjacent, concentric piston member 134. When positioned relative to ridge 144, as shown in FIG. 7, the detent ring 142 exerts a predetermined frictional securing force actingto carry the piston member 134 in common reciprocation with actuator piston 132. When detent ring 142 is disposed below ridge 1'44, piston member 132 is free to reciprocate alone inchamber 138.

The position-coupling, pressure-uncoupling and consequent relative and common reciprocation of

piston members

132 and 134 is analogous to that described above with respect to actuator rod 76 and seal 92, and therefore, will not be set forth again in detail. Suffice it to say, that fluid will be displaced from chamber 138 at rates proportional to the exposed working area of surface 146 of piston member 132 during relative, alone reciprocation of piston member 132, and at rates proportional to the sum of area 146 and the exposed working area of surface 148 of piston member 134 during common reciprocation.

The detent mechanism of FIG. 7 includes a compressible, annular detent ring 142 preferably formed of slightly resilient plastic material. Detent ring 142 is longitudinally spaced from an enlarged diameter end portion 158 of the central piston member 132 to define a space between detent ring 142 and end portion 158 for accepting the indented ridge 144 of annular piston 134. Ridge 144 is positionable in the space between detent ring 142 and end portion 158 by forcing slight overtravel of piston member 132 in the upward direction in a manner analogous to the coupling-efi'ecting overtravel of rod 76 described with respect to the embodiment of FIGS. 1-5.

The modified form of the invention depicted in FIG. 6 of the drawings is quite similar to FIG. 7 but incorporates a third, concentric, annular pumping member 136 disposed within chamber 138 intermediate the piston member 134 and the walls of chamber 138 to present a triple-stepped displacement pump. Pressurevof fluid in chamber 138' biases piston member 136 to its uppermost position shown in contact "with snap ring stop member 150 afiixed to housing 140'. Piston member 136 has an annular ridge 152, similar to ridge 144, protruding radially inwardly toward piston member 134 to be in interfering relationship with a compressible detent ring 154 carried on the exterior of middle piston member 134. When the piston members are positioned as shown in FIG. 6, the

inner members

132 and 134 are adapted to reciprocate in common and relative to outer piston member 136. Common reciprocation of all three piston members can be realized upon pulling

piston members

132 and 134 upwardly to compress detent ring 154 and force same over ridge 152 to a position above the latter. The consequent interfrictional securement of detent ring 154 and ridge 152 will urge the outer piston member to reciprocate in common with the two

inner piston members

132 and 134. Alone reciprocation of rod132 is again realized upon positioning detent ring 142 below ridge 144.

In the above manner, it will be apparent that the FIG. 6 embodiment presents a pump having three modes of operation, wherein displacement of the pump is correspondingly proportional to the number of piston members moving in common. Detent ring 154 is selectively sized to exert a frictional holding force upon ridge 152 smaller than the corresponding frictional force exerted by detent ring 142 upon ridge 144 so that the outer piston will be automatically uncoupled when pressure in chamber 138 rises above a first predetermined level, and piston member 134 will subsequently uncouple when pressure rises above a higher, second predetermined level during downward travel of piston member 132. As pressure increases, therefore, pump displacement capability reduces in sequential steps.

An O-ring seal 156 is carried upon the exterior surface of each of the three piston members to seal against the adjacent interior surface of the adjacent piston member. Seal 156 on outer piston member 136, of course, sealingly engages the walls of fluid chamber 138. The embodiments of FIGS. 6 and 7 therefore illustrate that any number of a plurality of piston members may be used to produce a corresponding number of operating modes wherein the pump exhibits differing displacement capabilities.

Another modified version of the invention illustrated in FIGS. 8 and 9 includes a housing 160 threadably secured to a fluid-conducting block 162 and an end cap 166 closing one end of a fluid working chamber 164 within housing 160. An actuator rod piston member 168 is longitudinally reciprocable within a central bore in end cap 166. Carried within chamber 164 is an annular sleeve stop shoulder 170 disposed either tightly or loosely within the chamber that has a lower face 172 spaced longitudinally from the end cap lower surface 174. A coupling and detent shoulder member in the form of snap ring 176 is carried upon rod piston member 168 so as to operatively engage an annular, ringshaped piston member 178 concentrically disposed with respect to the central rod piston member 168. Below and adjacent piston member 178 is an annular, V-shaped elastomer seal member 180 similar to seal 92 of FIG. 5, and a load-bearing metal washer 182. A compression spring 184 extends between the stop shoulder formed on block 162 and the load-bearing washer 182 to provide a mechanical biasing force urging the washer 182, seal 180 and piston member 178 upwardly into engagement with the sleeve end surface 172.

Rod 168 is illustrated in FIG. 8 as being located in a coupling position relative to piston member 178 wherein snap ring 176 engages an upper detent surface of member 178. Rod 168 is capable of overtravel in an upward direction relative to piston member 178 when the latter is engaging sleeve end surface 172 to move away from the relative coupling position to the phantom position of FIG. 8. In traveling through this first portion of its longitudinal stroke, rod 168 effects a first mode of operation of the pump wherein snap ring 176 remains spaced from the upper detent surface of piston member 178. Rod 168 freely slides through the central opening of the piston member 178 to reciprocate alone within the chamber 164 and displace fluid therefrom at rates proportional to the cross-sectional area of the lower surface of piston member 168 exposed to the chamber.

Rod piston member 168 is also reciprocable through a second, lower portion of its stroke as illustrated in FIG. 9, wherein snap ring 176 engages and carries piston member 178 in common reciprocation with the rod member 168. It will be apparent that piston member 168 remains in its coupling position relative to the annular piston member 178 throughout this lower portion of its stroke, and forces the annular piston member 178 downwardly to displace fluid in opposition to the urgings of spring-biasing member 184. The frictional interengagement of snap ring 176 with the upper detent surface of piston member 178, in conjunction with pressure in chamber 164 and the bias of spring 184, frictionally holds and carries piston member 178 with piston member 168. During upward, suction stroke travel of rod 168, the biasing member will urge the annular piston member 178 upwardly in common reciprocation therewith until the sleeve end surface 172 is engaged. In this stage of operation, fluid is displaced from chamber 164 at rates directly proportional to the sum of the cross-sectional surface areas of

piston members

168 and 178 exposed to the chamber.

Similar to the operations of the previously described embodiments, the pump of FIGS. 8 and 9 is adapted to displace a high volume of low pressure fluid when moving through the lower portion of its stroke of FIG. 9, and adapted to displace smaller volumes of higher pressure flow when operating in the upper portion of its stroke as shown in FIG. 8. It will be apparent that the higher volume operation depicted in FIG. 9 can be effected by a limited operating force on actuator rod 168 only if pressure within chamber 164 is below a predetermined level. For instance, assuming rod 168 is stroked by a direct manual force, the resisting force offered by pressure 164 and acting upon both piston members will ultimately exceed this inherently limited input force as pressure builds within chamber 164 and rises above a certain level. This pressure level is, of course, directly related to the magnitude of the input force and denotes the point when the hydraulic resisting force exceeds the limited strength of the manual operator. The pump can, therefore, operate in its high volume mode only when pressure chamber 164 is below a certain level related to the magnitude of the input force. Above this pressure level, of course, rod 168 is still reciprocable through the upper portion of its stroke shown in FIG. 8 to effect displacement of lower volumes of higher pressure fluid.

While the preferred embodiment and three modifications thereof have been described above in great detail for explanatory purposes, it will be apparent that other modifications and alterations to the invention may be made by those skilled in the art. The foregoing detailed description, therefore, is to be considered exemplary. in nature and not as limiting to the scope and spirit of the invention as set forth in the appended claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

1. A stepped displacement fluid device comprising:

a housing provided with a fluid pressure chamber and duct means for accommodating flow of fluid to and from said chamber;

piston means reciprocably mounted in said chamber and having a working surface exposed to the pressure of fluid in said chamber, said piston means being operable to reciprocate alone in said chamber when said chamber pressure is above a predetermined level for displacing fluid therefrom to said duct means in relationship to the area of said exposed working surface;

unitary piston sealing means disposed about said piston means in sealing engagement with the walls of said chamber;

pressure actuatable coupling means for selectively engaging said piston sealing means to thereby effeet said common reciprocation, said piston sealing means being adapted to engage the walls of said chamber to effect a static seal therebetween while simultaneously providing a dynamic seal between said piston and sealing means as said piston means reciprocates alone, and operable to engage said piston means to effect a static seal therebetween while simultaneously providing a dynamic seal between said sealing means and said chamber walls as said piston and piston sealing means reciprocate in common; and

actuator means operatively connected to said piston means for reciprocating therewith during the reciprocation of said piston means alone and during said common reciprocation of said piston and piston sealing means.

2. A stepped displacement fluid device comprising:

a housing provided with a single fluid chamber and duct means for accommodating flow of motive fluid to and from said chamber;

piston means reciprocably mounted in said chamber in sealing engagement with said housing for displacing fluid from said chamber in proportion to the working area of said piston means exposed to pressure in said chamber and reciprocating therein, said piston means including first and second members selectively reciprocal together in common movement to displace fluid in proportion to the sum of the working areas of said first and second members exposed to pressure in said chamber and operable to move relatively to displace fluid in proportion to said exposed working area of the first member;

a single, pressure actuatable, selectively engageable coupling means on said piston means for operatively interconnecting said first and second members to effect said common movement thereof when said coupling means are engaged, said coupling means being the sole coupling force between said members and operable to permit said relative movement of the members when said coupling means are disengaged;

stop means on said housing for engaging said second member to limit movement thereof in one direction when engaged therewith, said first member being positionable in a coupling position relative to said second member while the latter is in said stopengaging position to effect engagement of said coupling means and movable relative to said second member away from said coupling position while said second member is in said stop-engaging position to effect disengagment of said coupling means; and

actuator means operatively connected to said first member for moving therewith during both said relative movement and said common movement of said members.

3. The device of claim 2, wherein said second member is responsive to the pressure of fluid in said chamber to be biased thereby toward said stop-engaging position, and wherein said coupling means comprise detent means associated with each of said first and second members operable to frictionally intersecure said members for said common reciprocation upon positioning said first member in said relative coupling position, said detent means being located at fixed positions on said first and second members so as to disengage upon movement of said first member and associated detenting lip away from said coupling position while said pressure responsive second member and associated detenting lip remain in said stop-engaging position.

4. A stepped displacement fluid device comprising:

a housing provided with a single fluid pressure chamber and duct means for accommodating flow of fluid to and from said chamber;

first piston means reciprocably mounted in said chamber and having a first working surface exposed to the pressure of fluid in said chamber, said first piston means being operable to reciprocate alone in said chamber when said chamber pressure is above a predetermined level for displacing fluid therefrom to said duct means in relationship to the area of said exposed first working surface;

second pressure responsive piston means reciprocably mounted in said chamber and having a second working surface exposed to said chamber pressure, said second piston means being adapted to move in common reciprocation with said first piston means only when said chamber pressure is below said predetermined level for displacing fluid to said duct means and performing work in relationship to the sum of the areas of said first and second exposed surfaces;

a single, pressure actuatable coupling means carried by one of said piston means for selectively interengaging said first and second pistons when said chamber pressure is below said predetermined level to effect said common reciprocation, said coupling means being the sole coupling force between said pistons and acting in response to a rise in said chamber pressure above said predetermined level to completely disengage said first and second piston means; and

actuator means operatively connected to said first piston means for reciprocating therewith during both said reciprocation of said first piston means alone and during said common reciprocation of said first and second piston means.

5. The device of claim 6, wherein said coupling means comprise a shoulder on said rod disposed to engage said sleeve to carry the latter with said rod during one portion of travel of said rod to effect said common reciprocation during said portion of rod travel, said shoulder disengaging from said sleeve to allow said relative reciprocation of the rod during another portion of rod travel.

6. The device of claim 1, wherein said first piston means includes a cylindrical rod having an inner end disposed in said chamber defining said first exposed working surface and an outer end extending outwardly of said chamber defining said actuator means, and wherein said second piston means includes a cylindrical sleeve mounted to reciprocate longitudinally in said chamber, said sleeve being positioned surrounding said rod and defining an annularly shaped second exposed working surface, said rod operable to reciprocate longitudinally relative to said sleeve during said reciproca tion of said rod alone.

7. The device of claim 6, wherein said second piston means further comprises a second cylindrical sleeve defining an annularly shaped third working surface exposed to said chamber pressure, said second sleeve being operable in response to said chamber pressure to move in common reciprocation with said first sleeve when said chamber pressure is below a second predetermined pressure level lower than said first predetermined pressure level to thereupon effect fluid displacement in direct proportion to the sum of the areas of said first, second and third exposed surfaces.

8. The device of claim 6, further comprising means carried by said first piston means for dynamically sealingly engaging said sleeve and rod to prevent fluid leakage therebetween during said relative reciprocation of the rod and operable to effect a static seal therebetween during said common reciprocation of the rod and sleeve.

9. The device of claim 8 further comprising second sealing means carried by said second piston means for sealingly engaging the walls of said chamber and said sleeve to prevent fluid leakage therebetween.

10. The device of claim 6, wherein said coupling means comprise noncompressible and compressible detents located upon adjacent surfaces of said rod and sleeve and being interengageable to exert a predetermined friction force interconnecting said rod and sleeve to effect said common reciprocation, said detents being positioned relative to said chamber so that during movement of the rod, said chamber pressure effectively exerts a force on said detents of opposing said predetermined friction force and exceeding same when chamber pressure is above said predetermined level to thereupon effect disengagement of said detents and permit said relative reciprocation of the rod.

11. The device of claim 10 further comprising a first stop member carried on said housing and located to engage said sleeve to limit movement thereof in a first longitudinal direction, said rod being movable in said first direction to a coupling position relative to said sleeve to effect interengagement of said detents when said sleeve is engaging said stop member.

12. A stepped displacement fluid device comprising:

a housing provided with a single fluid pressure chamber and duct means for accommodating flow of fluid to and from said chamber; a cylindrical rod reciprocably mounted in said chamber and of a diameter to present a cylindrical space between the rod and the chamber, said rod being positioned to travel longitudinally of said chamber l to effect displacement of fluid therefrom in propor- 3 tion to said rod diameter; unitary piston sealing means of annular configuration disposed in said cylindrical space of the chamber T for operatively engaging the walls of said chamber and said rod to prevent fluid leakage from the chamber, said piston sealing means being selectively reciprocable in common with said rod to ef- 1 fect fluid displacement from said chamber in proportion to said chamber diameter, said rod also being reciprocable relative to said sealing means to effect said fluid displacement proportional to said rod diameter; and a single, pressure, actuatable coupling means on said 1 rod for selectively engaging said piston sealing 1 means to thereby effect said common reciprocation thereof and said fluid displacement proportional to said chamber diameter upon rod travel,

said coupling means being selectively disengageable from said piston sealing means to thereby effect said relative reciprocation thereof and said fluid displacement proportional to said rod diame ter upon rod travel, said piston sealing means being operable to statically and dynamically seal against said rod during said common and said relative reciprocation of said rod respectively.

13. The device of claim 12, wherein said piston sealing means include a unitary fluid seal of annular configuration having an inner annular surface positioned in dynamic and static sealing engagement with said rod and an outer annular surface positioned in dynamic and static sealing engagement with said chamber walls.

14. The device of claim 12, wherein said coupling means comprises a detent member carried on said rod operable to frictionally engage said piston sealing means to secure the latter to said rod upon positioning the rod at a predetermined coupling position relative to said piston sealing means.

15. The device of claim 14, wherein said detent member is arranged relative to said chamber to be responsive to the pressure of fluid therein and to disengage from said piston sealing means in response to pressure in said chamber above a predetermined level.

16. The device of claim 15, further comprising stop means on said housing for contacting said piston sealing means to limit travel thereof in one longitudinal direction, said rod being forcibly movable farther in said one direction than said piston sealing means to permit corresponding forcible overtravel by said rod to said relative coupling position while said piston sealing means are engaging said stop means, whereby upon forcing overtravel of the rod to said coupling position, said detent member frictionally engages said piston sealing means to secure the latter to said rod.

g gi UNITED STATES PATENT OFFICE CERTIFICATE OF CO'RRECTIGN Patent No. 3,775,027 Dated November 27, 1973 Inventor(s) ROGER L'. CRAFT I It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

In Claim 6, line 1, the dependency reference numeral (1) should be deleted, and thenumeral l substituted therefor.

Signed and sealed this 21st day ofMay 197g.

Si JAL) Attest EDWARD .FLETGIUER, JR. EFARSlLXLL DAii'i-L Attesting Officer Cormissloner of Patents

Claims

1. A stepped displacement fluid device comprising: a housing provided with a fluid pressure chamber and duct means for accommodating flow of fluid to and from said chamber; piston means reciprocably mounted in said chamber and having a working surface exposed to the pressure of fluid in said chamber, said piston means being operable to reciprocate alone in said chamber when said chamber pressure is above a predetermined level for displacing fluid therefrom to said duct means in relationship to the area of said exposed working surface; unitary piston sealing means disposed about said piston means in sealing engagement with the walls of said chamber; pressure actuatable coupling means for selectively engaging said piston sealing means to thereby effect said common reciprocation, said piston sealing means being adapted to engage the walls of said chamber to effect a static seal therebetween while simultaneously providing a dynamic seal between said piston and sealing means as said piston means reciprocates alone, and operable to engage said piston means to effect a static seal therebetween while simultaneously providing a dynamic seal between said sealing means and said chamber walls as said piston and piston sealing means reciprocate in comMon; and actuator means operatively connected to said piston means for reciprocating therewith during the reciprocation of said piston means alone and during said common reciprocation of said piston and piston sealing means.

2. A stepped displacement fluid device comprising: a housing provided with a single fluid chamber and duct means for accommodating flow of motive fluid to and from said chamber; piston means reciprocably mounted in said chamber in sealing engagement with said housing for displacing fluid from said chamber in proportion to the working area of said piston means exposed to pressure in said chamber and reciprocating therein, said piston means including first and second members selectively reciprocal together in common movement to displace fluid in proportion to the sum of the working areas of said first and second members exposed to pressure in said chamber and operable to move relatively to displace fluid in proportion to said exposed working area of the first member; a single, pressure actuatable, selectively engageable coupling means on said piston means for operatively interconnecting said first and second members to effect said common movement thereof when said coupling means are engaged, said coupling means being the sole coupling force between said members and operable to permit said relative movement of the members when said coupling means are disengaged; stop means on said housing for engaging said second member to limit movement thereof in one direction when engaged therewith, said first member being positionable in a coupling position relative to said second member while the latter is in said stop-engaging position to effect engagement of said coupling means and movable relative to said second member away from said coupling position while said second member is in said stop-engaging position to effect disengagment of said coupling means; and actuator means operatively connected to said first member for moving therewith during both said relative movement and said common movement of said members.

4. A stepped displacement fluid device comprising: a housing provided with a single fluid pressure chamber and duct means for accommodating flow of fluid to and from said chamber; first piston means reciprocably mounted in said chamber and having a first working surface exposed to the pressure of fluid in said chamber, said first piston means being operable to reciprocate alone in said chamber when said chamber pressure is above a predetermined level for displacing fluid therefrom to said duct means in relationship to the area of said exposed first working surface; second pressure responsive piston means reciprocably mounted in said chamber and having a second working surface exposed to said chamber pressure, said second piston means being adapted to move in common reciprocation with said first piston means only when said chamber pressure is below said predetermined level for displacing fluid to said duct means and performing work in relationship to the sum of the areas of said first and second exposed surfaces; a single, pressure actuatable coupling means carried by one of said piston means for selectively interengaging said first and second pistons when said chamber pressure is below said Predetermined level to effect said common reciprocation, said coupling means being the sole coupling force between said pistons and acting in response to a rise in said chamber pressure above said predetermined level to completely disengage said first and second piston means; and actuator means operatively connected to said first piston means for reciprocating therewith during both said reciprocation of said first piston means alone and during said common reciprocation of said first and second piston means.

6. The device of claim 1, wherein said first piston means includes a cylindrical rod having an inner end disposed in said chamber defining said first exposed working surface and an outer end extending outwardly of said chamber defining said actuator means, and wherein said second piston means includes a cylindrical sleeve mounted to reciprocate longitudinally in said chamber, said sleeve being positioned surrounding said rod and defining an annularly shaped second exposed working surface, said rod operable to reciprocate longitudinally relative to said sleeve during said reciprocation of said rod alone.

12. A stepped displacement fluid device comprising: a housing provided with a single fluid pressure chamber and duct means for accommodating flow of fluid to and from said chamber; a cylindrical rod reciprocably mounted in said chamber and of a diameter to present a cylindrical space between the rod and the chamber, said rod being positiOned to travel longitudinally of said chamber to effect displacement of fluid therefrom in proportion to said rod diameter; unitary piston sealing means of annular configuration disposed in said cylindrical space of the chamber for operatively engaging the walls of said chamber and said rod to prevent fluid leakage from the chamber, said piston sealing means being selectively reciprocable in common with said rod to effect fluid displacement from said chamber in proportion to said chamber diameter, said rod also being reciprocable relative to said sealing means to effect said fluid displacement proportional to said rod diameter; and a single, pressure, actuatable coupling means on said rod for selectively engaging said piston sealing means to thereby effect said common reciprocation thereof and said fluid displacement proportional to said chamber diameter upon rod travel, said coupling means being selectively disengageable from said piston sealing means to thereby effect said relative reciprocation thereof and said fluid displacement proportional to said rod diameter upon rod travel, said piston sealing means being operable to statically and dynamically seal against said rod during said common and said relative reciprocation of said rod respectively.