US3090313A

US3090313A - Variable displacement pump

Info

Publication number: US3090313A
Application number: US105357A
Authority: US
Inventors: Budzich Tadeusz
Original assignee: Weatherhead Co
Current assignee: Weatherhead Co
Priority date: 1961-04-25
Filing date: 1961-04-25
Publication date: 1963-05-21
Anticipated expiration: 1980-05-21
Also published as: GB968621A; DE1453693A1

Description

y 1963 T. BUDZICH 3,090,313

VARIABLE DISPLACEMENT PUMP Filed April 25, 1961 4 Sheets-Sheet 1 INV EN TOR.

May 21, 1963 T. BUDZICH VARIABLE DISPLACEMENT PUMP Fild April 25, 1961 4 Sheets-Sheet 2 INVENTOR;

TADEUSZ 56/02/67,

May 21, 1963 T. BUDZICH 3,090,313

VARIABLE DISPLACEMENT PUMP Filed April '25, 1961 4 Sheets-Sheet 3 ATTO/QA/EYS May 21, 1963 T. BUDZICH VARIABLE DISPLACEMENT. PUMP 4 Sheets-Sheet 4 Filed April 25, 1961 INVENTOR.

United States Patent 3,539,313 VARIABLE DlSiLACEh/IENT PUMP Tadeusz Bndzich, Shaker Heights, Ghio, assignor to The Weatherhead Company, Cleveland, Ohio, a corporation of Ohio Filed Apr. 25, 196i, Ser. No. 105,357 9 Claims. (Cl. 103-37) This invention relates generally to positive displacement hydraulic pumps, and more particularly to the reciprocating piston type of positive displacement pumps in which pistons are reciprocated through a fixed stroke, but the effective displacement of the pump can be varied to change the volume of the fluid output.

A principal feature of this invention is the provision of a positive displacement axial piston pump of the fixed stroke type in which the cylinder block is slidabie within the pump housing and carries ports which permit fluid within the pump housing to enter the cylinder bores, in which the effective volume of the pump is varied by axially shifting the position of the cylinder block and hence the ports relative to the piston stroke. For maximum output volume of the pump, the cylinder block is positioned so that the port is fully opened at the rearward reversal of the piston to allow the cylinder bore to fill with fluid, after which forward motion of the piston seals off the port after only a short distance of movement. and forces the remainder of the fluid Within the cylinder bore out through check valves into the outlet port. By shifting the cylinder block in the one direction toward the forward end of the piston stroke, the port is not closed by the piston until a later portion of the stroke, so that some of the fluid in the cylinder is forced back out through the port and therefore a lesser volume is pumped outward through the check valves. Pumps of this type have been disclosed in co-pending applications by the present inventor Serial No. 825,005, filed July 6, 1959 and Serial No. 847,512, filed October 20, 1959.

According to the present invention, the cylinder block may also be moved further toward the rearward end of the piston stroke so that the port is not completely opened during the reversal of the piston and the fluid Within the pump housing is throttled by the decreased size or" the port openings so that the cylinder bore is not completely filled and only that volume of fluid which enters the cylinder =bore is pumped out through the check valves. A pump incorporating this type of control is disclosed in my co-pending application Serial No. 82,292, filed Janumy 12, 1961. In the present invention, both of these types of control are incorporated into the same pump to provide two alternative methods of control for reducing the efi'eotive output volume of the pump.

Another feature of this invention resulting from the incorporation in a single pump of both methods of control is that the position of the cylinder block can be controlled m-anually in such a manner that by employing the spill type control, the cylinder block may be precisely positioned over a relatively long range of movement to provide very precise and accurate control of the output volume, and the pump block can also be positioned by the throttling type control to obtain a very rapid response because of the short distance through which the cylinder block moves to reduce the output volume with this control.

Another feature of this invention resulting from the dual methods of control of the effective output volume of the pump is that an automatic control is supplied to position the cylinder block using the spill type of control while a manual control means is provided to shift the cylinder block in the other direction to control the effective output volume by the throttling of the fluid entering the cylinder bores.

Another feature of this invention is that a manual control for shifting the cylinder block may be supplied for shifting the cylinder block in which the change in output volume is directly proportional to the amount of movement of the cylinder block and hence of an external lever which is provided for shifting the position of the cylinder block.

Another feature of this invention is that no fluid pres sure or spring forces are applied to the cylinder block when the dual manual control is employed so that the cylinder block remains easily shiftable by hand throughout both ranges of control and may be selectively clamped in position any place Within the ranges without producing noticeable stress on any of the pump parts.

Another feature of this invention is that an automatic control for the cylinder block is supplied in combination with a manual control in which the automatic control during manual operation will operate as an excess pressure valve and shift the cylinder block to reduce the effective output volume in case the outlet pressure should exceed a predetermined value even though the pump is heing regulated by manual control.

Another feature of this invention is that in the aforedescribed arrangement employing a combination automatic and manual control, no force is normally applied to the cylinder block in manual operation and the automatic control is rendered inoperative and applies no forces to shift the cylinder block unless the outlet pressure should exceed the predetermined limit.

Many additional features and advantages of this invention relating to the simplicity of construction, ease of operation and low cost of manufacture will readily become apparent to those skilled in the art upon a reading of the following detailed description of several embodiments of the invention as illustrated in the drawings in which:

FIG. 1 is a longitudinal cross-sectional view of a pump according to the present invention in which the cylinder block is shifted manually to control the effective output volume by both spill type control and throttling control;

FIG. 2 is a fragmentary cross-sectional view of the cylinder block and piston when the cylinder block has been shifted to minimum output volume employing the throttling type control;

FIG. 3 is a fragmentary cross-sectional view similar to that of FIG. 2 but showing the cylinder block shifted to the minimum effective volume position according to the spill type control;

PEG. 4 is an end elevational view of the pump of FIGS. 13 showing the external control lever;

FIG. 5 is a side elevational view of the pump showing the external control lever;

FIG. 6 is a longitudinal cross-sectional view of another embodiment of the invention employing an internal automatic control for reducing the effective volume by the spill type control and employing a manual control to reduce the effective volume by throttling type control;

FIG. 7 is a fragmentary cross-sectional view of the pump of FIG. 6 showing the cylinder block shifted to the minimum output volume according to the manual control;

FIG. 8 is a fragmentary cross-sectional view similar to that of FIG. 7 but showing the cylinder block shifted to the minimum output volume by the automatic control; and

FIG. 9 is a side elevational view of the pump of FIGS. 6-8 showing the arrangement of the external control lever.

Referring now to the drawings in greater detail, there is illustrated in FIG. 1 a pump having a pump housing 10 which encloses a fluid chamber 11 Within which the pump mechanism is located. The pump housing 10 is generally cylindrical in shape and at one end is formed with an internal cylindrical end portion 12 which is closed off by an outlet housing 13. The outlet housing 13 abuts against an inwardly projecting flange 14 on the pump housing and is secured in place by means of suitable set screws indicated at 15. An O-ring seal 16 is provided on the outer periphery of the outlet housing 13 to prevent leakage at the joint between the outlet housing and the pump housing. A threaded inlet opening '18 is formed on the side of pump housing 10 adjacent its mid-point for connection to a fluid reservoir for admission of fluid from the reservoir into the chamber 11.

At its other end, the pump housing 10 is closed ofl by a drive housing 20 secured in place by means of cap screws 21. As shown, drive housing 20 is provided with a radial flange 22 for mounting the pump in position on machinery or a prime mover. An axial bore 24 extends through the drive housing 20 to receive a bearing member 25 at its inner end. The bearing member 25 has an axial portion 26 extending along the bore 24 and a radial portion 27 extending outwardly along the inner wall of the drive housing 20. A drive member 30 is rotatably journaled within the axial portion 26 of bearing member 25 and has a shank portion 31 extending axially outward through the drive housing to make sealing Contact with oil seal '32 fltted within the outer end of axial bore 24. The drive member 30 has a radially extending flange portion 33 making bearing contact with the radial portion 27 of the bearing member which provides a thrust bearing to absorb the axial forces of the pumping action. A drive shaft 35 extends axially through a bore within the drive member 30 and is secured thereto by a spline connection 36. The drive shaft 35 projects axially outward beyond the end of the shank portion 31 for connection to a suitable motor or other prime motor for driving the pump.

Mid-way between the outlet housing 13' and drive housing 20, a web member or plate 38 extends transversely across the fluid chamber 11 and is provided with an axially extending peripheral flange '39 which fits against the walls of the pump housing 10-. The web memberSS is held against axial movement by an inwardly extending annular shoulder 40 formed on the pump housing 10, and at the other end by a snap ring 41. The web member 38 has an axially extending portion 43 which projects toward the drive housing 20. The axial extension 43 is provided with an axial bore 44 which communicates with transverse opening 45 to allow free circulation of fluid within the chamber 11 from one side of the web member 38 to the other. The outer end of axial extension 43 carries a bearing insert 46 which receives the pilot end portion 47 of the drive shaft 3'5.

The drive member 38' is provided with an inclined face 50 and a hub portion 51 which extends perpendicular to the inclined face 50. A bearing member 52 is mounted on drive member 30 and includes a radially extending flange portion 53 lying along the inclined face 50, and an axial sleeve portion 54 extending along the hub portion 51. Bearing member '52 serves to journal a wobble plate 55 which is supported on the radial and axial hearing portions 53 and 54, respectively. At its lower end, the wobble plate 55 is provided with a projecting stud 57 on which is rotatably secured a guide block 58. Guide block '58 is adapted to slide longitudinally within a channel 59 formed in the pump housing 10 to prevent rotation of the wobble plate 55 as it is oscillated by the rotation of the guide members 30. V

A cylinder block 62 is slidably journaled in the cylindrical end portion 12 of pump housing 10 for axial sliding movement therein. The cylinder block 62 is restrained from rotating Within the pump housing by a set screw 63 mounted in the wall of .the pump housing 10 and having a dog point engaging a longitudinal groove or guide slot 64 on the outer periphery of the cylinder block. The cylinder block 62 is provided with a plurality of axially extending cylinder bores 65 which are spaced equidis- 4 tantly about the cylinder block at points equidistant from the axis of the drive shaft 35. Only one cylinder bore has been shown for purposes of clarity, but it is understood that the pump has a plurality of cylinders similar to the one shown in the drawings and described hereinafter. The cylinder block 62 is also provided with one or more passages 67 extending therethrough from one side to the other around the outer periphery and with a centrally disposed axial bore 68 so that fluid can circulate freely within the chamber 11 on both sides of the cylinder block.

A piston or plunger 70 is fitted within the one end of the cylinder bores and has a head portion 71 on the end away from the wobble plate 55. Piston has a tubular skirt portion 72 extending rearwardly away from the head portion 71. A compression spring 74 is fitted around the tubular skirt portion 72 and abuts at the one end against the web member 38. At the other end, compression spring 74 abuts against a spring retainer 75 secured at the outer end of the tubular skirt portion 72. Thus the compression spring 74 serves to bias the piston 70 toward a rearward position within the cylinder bore and toward the wobble plate 55. The piston 70 is drivingly connected to the wobble plate 55 by means of a pis ton rod 77 which is positioned within the tubular skirt portion 72. At its one end, piston rod 77 has a ball end 78 which seats in a suitable recess directly beneath the head portion 71 on the piston 70, and at its other end the piston rod has another ball end 79 which is seated within a cup-like recess 81 on the face of the wobble plate 55. At its midpoint the piston rod 77 is provided with a radially extending flange or centering disc 82 to maintain the piston rod in axial alignment within the tubular skirt portion 72 if either end of the piston rod should become unseated from its seat against either the piston head 71 or the wobble plate 55.

The cylinder block 62 has an annular groove or outer filling slot 85 extending circumferentially about its periphery and opening into each of the cylinder bores 65 to admit fluid therein. A second annular groove or inner filling slot 87 extends radially outward from the axial bore 68 within the cylinder block 62 to open into the cylinder bores 65 at their inner sides. Forward edge 86 of the outer filling slot 85 and the forward edge 88 of the inner filling slot 87 both lie in the same plane, and the spacing of the

forward edges

86 and 88 from the piston head 71 determines the eflective port area of the two filling

slots

85 and 87.

A reaction piston 96 i slidably journalled within the ends of the cylinder bores 65 opposite the pistons 70 to make a sealing fit within the cylinder bore to prevent leakage of fluid between the reaction piston and the cylinder bore walls. Each of the reaction pistons 96 has an axial bore 91 extending therethrough, and at the end away from the piston 70, the reaction piston 96* has a snap ring 92 which forms one abutment for a compression spring 93 fitted around the end of the reaction piston. The other end of compression spring 93 abut-s against a retainer plate 94 secured to the inner face of the outlet housing 13 by suitable screws 96.

The outlet housing 13 is provided with a bore or chamber 98 opposite each of the reaction pistons to receive a port member 99. Port member 99 is provided with an O-ring seal 101 to make sealing contact with the bore 98 and has a projecting end portion 102 to make sealing contact with the end of the adjacent reaction piston 90. A bore 103 extends through the port member 99 to connect with the axial bore 91 in the reaction piston 90. The opposite end of the bore 98 is closed ofi by a suitable plug 104-, and positioned within the bore is a cage 106 which encloses a compression spring 107 biasing a check valve plate 168 against the other end of the port member 99 to close off bore 103-. Thus the check valve plate 108 serves to permit fluid within the reaction piston 98 and port member 99 to pass outwardly past the plate, but prevents fluid from entering the port member 99 from the outlet side. A connecting passage 109 extends from each of the bores 98 radially inward to connect with an wially located outlet passage bore 111 in the outlet housing 13. Outlet bore 111 is provided with a suitable threaded portion 112 at its outer end to receive a suitable pipe fitting for connection to the outlet line of the pump.

The manual control mechanism for shifting the cylinder block 62 longitudinally within the pump housing 1G is shown most clearly in FIGS. 4 and 5 together with FIG. 1. The pump housing includes a cross shaft housing portion 115 projecting from the lower side of the pump housing beneath the cylinder block 62. A cross shaft 117 is journaled in the cross shaft housing portion 115 and carries a lever arm 118 at its inner end. Lever arm 118 is secured to the inner end of the cross shaft 117 by a set screw 119 and at its upper end is provided with an end portion 121 to fit within the outer filling slot 85 on the cylinder block 62. It will be understood that the end portion 121 fits into the outer filling slot '85 between two of the cylinder bores so as not to block off or obstruct the port area provided by the filling slot at these cylinder bores. An indicia plate 123 is mounted on projection bosses 124 by means of suitable cap screws 125 to extend along the side wall of the pump housing 1%. A control handle 127 is secured at its lower end to the outer end of the cross shaft 117 and extends along the inner side of indicia plate 123. A screw clamp 130 is fastened to the upper end of control handle 127 to slide within an arcuate slot 128 on indicia plate 123. By tightening the screw clamp 130, the control handle 127 can be locked in place on the indicia plate 123. It will be noted that a pointer 131 may be provided on the control handle 127 for alignment with indicia marks 132 along the arcuate upper edge of indicia plate 123 for noting and recording the relative position of the control handle with respect to the indicia plate.

The operation of the pump can be seen most clearly in conjunction with FIGS. 2 and 3. When the cylinder block is in the position of FIG. 1 and the piston 7a is in the rearward or retracted position, the forward edges 86 and 8 8 of the inner and

outer filling slots

85 and 87, respectively, are spaced forward of the piston head 71. Under these conditions, the fluid within the chamber 11 is free to flow inward through the filling slots to completely fill the cylinder bore 65. As the piston 70 moves forward, the piston head 71 will be shifted toward the reaction piston 90 to reduce the volume within the cylinder. Since the filling

slots

85 and 87 are open during the initial portion of the stroke, fluid will be forced outward into the chamber 11 through these slots. However, after the piston head 71 passes the forward edges 86 and 88 of the filling slots, these filling slots are sealed ed and the remainder of the fluid within the cylinder bores will be positively displaced outward through the reaction piston 9th and port member 99, and hence past the check valve plate 168, through connecting passage 169', and into the outlet passage bore 111. When the piston 7 ti is retracted, the check valve plate 108 will close and a partial vacuum will be formed within the cylinder bores until the piston head 71 has retracted past the forward edges 86 and 88 of the filling slots so that they are open to allow fluid within the chamber 11 to flow through the filling slots and refill the cylinder bores.

The effective output volume of the pump may be reduced by two different methods, depending upon which direction the cylinder block is. shifted from the position of maximum output volume as shown in FIG. 1. When the cylinder block is shifted toward the rearward position as shown in FIG. 2, the cylinder block as is brought into contact with the web member 38. The filling slots 85' and 87 are hence moved toward the rearward position of the piston, and in the position shown, the forward edges 86 and 88 of the filling slot will be adjacent the head portion 71 of the piston when the latter is in the retracted position. As a result, the ports provided by the filling

slots

85 and 87 will never be open and no fluid can enter the cylinder bores. Thus the partial vacuum which occurs when the piston is retracted will remain within the cylinder bore and no fluid will be forced outward past the check valve plate 108 when the piston is at the forward end of the stroke and thus the pump will have no effective output volume.

It will be understood that in accordance with the teaching of the inventors co-pending application Serial No. 82,292, previously referred to, that when the cylinder block 62 is in a position intermediate that of FIGS. 1 and 2, where the forward edges 86 and 38 of the filling slots are positioned closer to the piston head 71 when the latter is in the retracted position, the effective port area presented by the filling

slots

85 and 87 will not be sufficiently great to allow the fluid within the pump housing chamber 11 to completely fill the cylinder bores. The reduced effective port area thus serves to throttle the flow of fluid into the cylinder bores to reduce that flow to an amount less than that required to completely fill the partial vacuum created within the cylinder bores by the retraction of the piston. Only the volume of fluid which was permitted to enter by the position of the ports will be pumped outward through the check valve plate 193 and only this amount will constitute the effective output volume of the pump. Since it is necessary to move the cylinder block 62 through only a very short distance to change the effective output volume of the pump from maximum to zero by this method of control, a very fast response can be obtained.

When the cylinder block 62 is shifted in the opposite direction away from the web member 33 and toward the outlet housing 13, it reaches a limiting position as shown in FIG. 3 in which the effective output volume of the pump is also reduced to zero. As previously stated, when the piston starts its forward stroke, the fluid within the cylinder ibore will be spilled out through the filling slots S5 and 87 until the piston head 71 has passed to the forward edges 86 and 83 of the filling slots to seal off these slots and prevent passage of fluid from within the cylinder bore outward into the pump housing chamber 11. As the cylinder block 62 is shifted toward the outlet housing 13, the piston 70 must move farther forward along its stroke before the filling

slots

85 and 87 are closed off. Thus, a lesser portion of the piston stroke is employed for forcing fluid past the check valve plate 1% and smaller volume of fluid will therefore be discharged into the outlet passage bore 111 for each piston stroke. When the cylinder block 62 is shifted to the limiting position of FIG. 3, the forward edges '86 and '88 of the filling

slots

85 and 87, respectively, are positioned on a line with the edge of the piston head 71 when the latter is at the forward end of its stroke. Thus, the piston head 71 will never be able to close off the filling

slots

85 and 87 before the end of the stroke and all of the fluid within the cylinder bores will be discharged outward through the filling slots and none will be pumped outward past the check valve plates 198.

This latter method of controlling the pump volume requires that the cylinder block 62 be shifted through a distance equal to a substantial portion of the stroke of the piston 70 to vary the effective output volume from maximum down to Zero. As a result, this method of control allows the effective output volume to be very precisely controlled since the cylinder block 62 can be positioned with a high degree of accuracy over the relatively long length of the control stroke. On the other hand, the response with this method will not be as fast as that obtained with the throttling method since it naturally will take more time to shift the cylinder block through the longer distance with this type control. Thus the pump provides two methods of control, one employing throttling control which requires that the cylinder block be moved only a short distance to provide fast response, and the other employing spill control in which a high degree of accuracy can be obtained because of the relatively long length of movement of control handle.

It should be noted that there is no substantial resistance to a movement of the cylinder block 62 between either of the limiting positions as shown in FIGS. 2 and 3. This is true because the design of the pump pro-v vides that none of the pumping forces or reactive forces are transmitted to the cylinder block itself. Since the reaction piston is of the same diameter as the pumping piston 79, the pumping reaction forces will be absorbed entirely by these members and will lie directly along the axis of movement of the cylinder block. Thus the only forces opposing the movement of the cylinder block between these positions is the sliding friction of the moving parts and the necessity of displacing the oil from one side to the other of the cylinder block as it is shifted within the chamber 11. 7 An alternative embodiment of the invention is shown in FIGS. 6 through 9 in which the position of the cylinder block is controlled by a manual and an automatic control. The pump shown in these figures includes a pump housing or body which encloses a fluid charnher 141. Fluid from a reservoir or other source fills the chamber 141 through an inlet opening 14-2. At the one end, pump housing 140 is closed off by an end plate 143 which is fixedly secured to an outlet housing 144 by suitable locating pins indicated at 145. The end of plate 143 has a tubular guide portion 147 extending axially into the chamber 141, and guide portion 147 has an axial bore 148 extending therein from the outer end. A stop plate 150 has a shank portion fitted within axial bore 148 and a radially extending web portion 151 extending toward the walls of the pump housing 140.

At the other end of pump housing 140, an annular bearing member 153 is mounted on the pump housing to journal a drive member 155. This drive member has an axial ibore to receive a drive shaft 156 extending therethrough and making a spline connection indicated at 157 to rotatably drive the drive member 155. The drive shaft 156 extends into the chamber 14-1 and at its inner end carries a pilot portion 153 which is journaled within a bore on the stop plate 150. The other end of drive shaft 156 extends outward through a bore 169 in the Walls of pump housing 149 to make sealing contact with anoil seal 161 at the outer end of bore 160. The drive member carries an inclined annular bearing member 164 to rotatably journal a wobble plate 165. In order to prevent the wobble plate 165 from rotating within the pump housing 141} as it is oscillated by rotation of drive member 155, it is provided with a projecting stud 167 at its lower end to rotatably journal a bearing block 168. The bearing block 168 is made a sliding fit within a longitudinal channel or guide 169 formed on the walls of pump housing 140.

A cylinder block is slidably mounted on a tubular guide portion 147 for longitudinal movement withm the purnp housing 140. The cylinder block 175 carries a guide pin 176 to fit within a longitudinal slot 177 on the tubular guide portion 147 to prevent rotation of the cylinder block within the pump housing. At its one end, cylinder block 175 is limited in longitudinal movement by the web portion 151 of the stop plate 159. At the other end, the cylinder block 175 is adapted to move into abutment with a spring abutment plate 178 slidably journaled within a cylindrical portion 179 of the pump housing 140. A snap ring 181 is positioned within the cylin drical portion 179 to limit movement of the spring abutment plate 178 toward the stop plate 15%. The cylinder block 175 is provided with a plurality of longitudinal cylinder bores 189 extending from end to end through the cylinder block and spaced equidistantly about the axis of the drive shaft 156. An annular filling slot 183 extends circumferentially about the outer periphery of cylinder block 175 and opens into the cylinder bores 186 to serve as aport for admitting fluid therein. A piston is slidably mounted within the cylinder bore 188 and has a head portion 136 extending forward within the cylinder bore to a point adjacent the forward edge 134 of the filling slot 183. The piston 185 also has a tubular skirt portion 187 projecting rearwardly out of the cylinder bore and toward the wobble plate 165. A compression spring 139 is fitted around the tubular skirt portion 187 and abuts at its one end against the web portion 151 of stop plate 156. -At its other end, spring 189 abuts against a spring retainer 196 secured to the outer end of tubular skirt portion 187. A piston rod 192 is fitted within the tubular skirt portion 187 and at its one end carries a ball portion 193 which bears against the underside of the piston head portion 186. The other end of piston rod 192 is formed with another ball portion 194- and fits within a cup-like recess 196 on the face of wobble plate 165. The midportion of piston rod 192 is enlarged as at 197 to maintain the axial alignment of the piston rod 192 in case either of the ends of the piston rod should be removed from their respective sockets.

A reaction piston 200 is fitted within the other end of the cylinder bore 181) and extends toward the end plate 143. The reaction piston 290 has an axial bore 201 therein to conduct fluid from the cylinder bore to the pump outlet. At the end adjacent the end plate 143, reaction piston 200 is provided with a snap ring 282 which serves as an abutment for a helical compression spring 203 which fits over the outer surface of the reaction piston and abuts at its other end against the spring abutment plate 178. The outlet housing 144 has a recess 205 in axial alignment with the cylinder bore to receive a port member 266. The port member 206 is provided with an O-ring seal 207 on its outer periphery to make sealing contact with the recess 205 and has a projecting end 298 which extends out through an opening 259 in end plate 143 to make sealing contact with the end of the reaction piston 20%. An axial bore 210 extends through a port member 206 in alignment with the axial bore 201 in the reaction piston. A cage 212 is fitted within recess 205 to support a compression spring 213 which biases a check valve plate 214 against the end of port member 206 to prevent a reverse flow of fluid from the recess 295 back into the reaction piston and cylinder bore. A connecting passage 216 extends radially inward to connect to an axially aligned outlet passage 218 formed in the outlet housing 144. The outer end of outlet passage 218 is threaded at 219 to receive a suitable pipe fitting for the outlet line from the pump.

The end plate 143 is provided with an axial extension 222 which extends into outlet passage 213 to seal off the latter at the inner end. Leakage of the high pressure outlet fluid past extension 222 is prevented by an O-ring seal 223 on its outer periphery. A reduced axial bore 224 extends through the extension 222 between outlet passage 218 and the axial bore or chamber 148 within the guide portion 147. A valve spool 226 is slidably fitted withinthe axial bore 224 and has outer and inner reduced annular portions 227 and 228 which define a land portion 229 between them. A passage 231 connects the outlet passage 218 to the outer reduced annular portion 227, and another passage 232 extends between the inner reduced portion 228 and the chamber 141 within the pump housing. An annular port 233 is formed on extension 222 opposite the land 229 and is connected through passage 243 to chamber 148.

The inner end of valve spool 226 extends into the axial bore 148 and supports a cap 236. The cap 236 is pro vided with a socket on its inner face to receive a ball 237 which is also received in a spring abutment member 238. A control spring in the form of helical compression spring 239 extends longitudinally within the axial bore 148 and seats at its one end against the spring abutment 238 and at its other end against another abutment 241 which is secured in the outer end of axial bore 148 by means of a snap ring 242. Adjacent the spring abutment member 2.41, a radial passage 24:; extends outward through the wall of tubular guide portion 147 to connect the axial bore 143 with annular passage 246 formed in the cylinder block 175 about the guide portion 147. In turn, annular passage 246 connects with an axial cylinder bore 247 formed within the cylinder block 175 about tubular guide portion 147. A piston 24 8 is secured on the end of tubular guide portion 147 by a snap ring 249 and makes sealing contact with the walls of the axial cylinder bore 24-7 to form an expansible fluid chamber 256- between the cylinder block and the piston.

In order to provide an external control for shifting the cylinder block 175, a control shaft housing 252 projects downwardly below the pump housing 14%, and a transverse control shaft 255 is journaled within housinng 252. A lever 254 is secured to control shaft 253 within the housing 252 and extends upward toward the cylinder block 175 where it has a ball end 256 adapted to fit within the filling slot 183 on the cylinder block. A longitudinal slot 257 is formed on the outer surface of cylinder block 175 to allow lever 254 and ball end 256 to move freely forward toward the spring abutment plate 1' 8 so that the lever 254 can be rotated out of contact with the sides of the filling slot 183 when the pump is under automatic control.

The control shaft 253 extends outward to the exterior of the pump, and as shown more clearly in FIG. 9, an arm 259 is secured on the outer end of the shaft adjacent an indicia plate 261. A handle 262 is pivotally mounted on the upper end of arm 259 by pivot pin 263, and a torsion spring 264 it fitted over the projecting end of pivot pin 263 and is connected both to a pin 266 on arm 259 and to another pin 267 on handle 262. Torsion spring 264 provides a spring-loaded connection between the handle and arm and is positioned to normally bias the handle 262 into contact with a stop pin 268 on arm 259. Thus, the handle and arm are normally in alignment as indicated in FIG. 9 but force applied to the arm 259 by rotation of the control shaft 253 as the cylinder block is moved toward the outlet housing under operation of the automatic control will cause the handle 262 in the operators hand to pivot around pivot pin 263 against the force of torsion spring 264 to prevent possible injury to the operators hand if he is holding the handle 262 for shifting the cylinder block under manual control when the automatic control comes into operation.

The operation of this embodiment of the pump can be seen more clearly in conjunction with FIGS. 7 and 8. When the cylinder block 175 is in the intermediate position as shown in FIG. 6, the filling slot 183 will present a maximum port area at the rearward reversal of the piston so that the cylinder bore will be completely filled at each reversal and all the fluid within the cylinder 'bore corresponding to the displacement of the piston stroke will 'be pumped out through the reaction piston 269 and port member 2% to the outlet passage 218. If the cylinder block 175 is shifted by means of the manual control lever toward the stop plate 150, the forward edge 134 of filling 183 will be shifted toward the piston head 166 to reduce the efiective port area of the filling slot. As has been previously described, the reduction in port area for the cylinder serves to throttle the flow of fluid into the cylinder bores and therefore reduces the effective output volume of the pump toward the zero output condition which occurs when the cylinder block is in the position of FIG. 7, so that the filling slot 183 is never uncovered by the piston head. It should be noted that since the spring abutment plate 178 is limited in its range of movement by the snap ring 181, there are no pumping or spring biasing forces exerted on the cylinder block 175 when the latter is between the position shown in FIG. 6 and that shown in FIG. 7. Therefore, it requires no noticeable effort on the part of the operator to shift the cylinder block within this range by means of the manual control handle.

The automatic control operates to shift the cylinder block to reduce the effective output volume of the pump whenever the pressure within the outlet passage 218 exceeds a predetermined level. When the pressure in the outlet passage 218 is well below this predetermined level, the control spring 239 acting through abutment 238, ball 237 and cap 23-6 will bias the valve spool 226 in a leftward direction as shown in FIG. 6. With the valve spool 226 in this position, the land 229 is shifted to the left of the annular port 233 which is then connected by the inner reduced annular portion 228 to the drain passage 232 leading to the interior of the pump housing. Since the annular port 233 is connected through passage 243 to the axial bore 148, and the latter is in turn connected through the radial passage 244 to the chamber 259, this latter chamber will therefore be at the low pressure corresponding to that of the fluid within the pump housing chamber 141. Thus the biasing force of the compression springs 203 on the reaction pistons 29% will bias the spring abutment plate 178 toward the right and maintain the cylinder block 175 shifted in the position of FIG. 6 to insure that the pump is operating at maximum output volume, unless the operator through the manual control lever should shift the cylinder rblock further toward the stop plate 156 to reduce the volume by manual control.

When the pressure within the outlet passage 21% builds up to the control pressure level, this pressure exerts a force on the end of the valve spool 2 26 tending to shift it toward the right as shown in FIG. 6 against the biasing force of the control spring 239. When this biasing force of the fluid pressure is sufficiently great to shift the valve spool to a position where the land 229 is to the right of the annular port 223, this latter port will be connected through the outer reduced annular portion 227 on the valve spool to the passages 231 leading to the outlet passages 21% Fluid under high pressure then enters through the passages 231, past the outer reduced annular portion 227 to the annular port 233, whence it flows through passage 243 into the axial bore 148. From axial bore 148, the high pressure fluid enters the chamber 250 to expand the size of that chamber by shifting the cylinder block 175 toward the outlet housing 144.

As the cylinder block 175- is shifted, it moves the spring abutment plate 178 away from the snap ring stop 181 to compress the springs 263 on the reaction pistons. The shifting of the cylinder block in this direction serves to shift the forward edge 184 of the filling slot 183 closer to the end of the reaction piston and tothe end of the compression stroke of the pistons 185. Thus the movement of the cylinder block in this direction through the operation of the automatic control reduces the effective output volume of the pump by the spill type control in a manner similar to the manual control in the embodiment of FIGS. 1 through 5.

When the reduction in the effective output volume of the pump serves to drop the pressure within outlet passage 218 to the preselected value, the valve spool 226 will be shifted to the intermediate position of FIG. 6, where the land 22 9 blocks off the annular port 233 to prevent further flow of fluid either into or out of the chamber 251). It will be seen that the forces on the valve spool 226' tending to admit fluid into the chamber 25% depend solely upon the pressure in the outlet passage 218, While the forces tending to shift the valve spool 226 toward the left to connect the chamber 250 with the pump housing chamber 141 are the sum of the biasing force of the control spring 239, and the pressure within the chamber 254) and axial bore 148 acting on the inner end of the valve spool 226, and these pressures will be dependent upon the amount of compression of the compression springs 293 biasing the cylinder block toward the maximum volume position.

If, when the cylinder block 175 is shifted toward the minimum output volume position as shown in FIG. 8,

with the cylinder block in the position where the piston head 186 fails to cover the filling slot 183 to seal off the intake port and hence no fluid is pumped into the outlet passage 218, an increase in demand at the outlet passage 218 will cause the pressure therein to decrease. The control mechanism will therefore act to shift the cylinder block back toward the maximum position to increase the output volume of the pump to maintain the selected pressure in the following manner. Decrease in the pressure at the outlet, passage 218 will cause the valve spool 226 to be shifted toward the left as a result of the aforesaid forces of the control spring 239 and the fluid pressure Within chamber 259. The land 229 will then be shifted to the left of the annular port 223, and the axial bore 148 and chamber 250 will then be connected to the pump housing chamber 141 in the aforedescribed manner. The biasing force of the compression spring 203 will then tend to shift the spring abutment plate 178 and cylinder block 175 toward the right and force the fluid within chamber 250 out into axial bore 148 and hence past the valve spool 226 into the pump housing chamber 141. This action will continue until either the cylinder block 175 has been shifted back to the maximum volume position where the spring abutment plate 178 is in contact with the snap ring stop 181, or else the pressure within the outlet passage 218 rises to a point where the valve spool 226 is shifted back toward the right so that land 229 blocks off the annular port 233.

If the pump is in operation under manual control with the operating handle 262 moved to shift the cylinder block 175 to a position where it is intermediate the spring abutment plate 178 and the stop plate 150, and the pressure within the outlet passage 218 should exceed the automatic control level, the valve spool 226 will be shifted in to admit fluid into chamber 250 and thereby force the cylinder block 175 past the maximum volume position toward a reduced volume position within the spill control range. Thus the automatic control serves as a pressure overload protective device to prevent the operator from exceeding the maximum pressure for the system when he is operating the pump under manual control. When it is intended to operate the pump using automatic control, the control handle 262 will be shifted to the lefthand position as seen inFIG. 9, so that the ball end 256 on lever 254 is shifted toward the end of the longitudinal slot 257 adja cent the spring abutment plate 178. This insures that position of the cylinder block 175 under the automatic control will not impart any motion to the lever 254 and hence to the operating handle 262. However, if the handle should be left in the righthand position as shown in FIG. 9, and if the automatic control should take over to shift the cylinder block 175 toward the left, the motion of the cylinder block 175 will force the lever 254 to the left, since the forces of the pressure within the chamber 250 biasing the cylinder block in that direction are relatively high compared to the forces which can be applied to the cylinder block by hand. If the operator is holding the handle 262 under these conditions, the rotation of the control shaft 253 and hence arm 259 will cause the toggle joints between the arm and handle to break against the biasing force of torsion spring 254 and the control shaft 253 will be able to rotate without movement of the handle 262 and the latter will not be forced from the operators hand in a manner which could cause serious injury.

While several embodiments of the invention have been shown in the drawings and described hereinabove in considerable detail, it is understood that this invention can take many other forms and embodiments, and that such forms and embodiments as may occur to those skilled in the art may be resorted to without departing from the scope of the invention as defined in the following claims.

What is claimed is:

1. A pump comprising a pump housing providing a fluid chamber therein, an inlet port to said fluid chamber,

an outlet port on said pump housing, a cylinder block mounted for slidable movement within said fluid chamber along a longitudinal axis, a plurality of cylinder bores in said cylinder block, a piston within each of said cylinder bores, means in said pump housing to progressively reciprocate said pistons in said cylinder bores between forward and retracted positions, means connecting each of said cylinder bores to said outlet port, an inlet port for each cylinder bore in said cylinder block, said port having axially spaced edges, said cylinder block defining a maximum volume position when the piston head is intermediate said port edges when the piston is in the retracted position, means to shift said cylinder block in one direction from said maximum volume position to reduce the effective area of said cylinder bore inlet ports, and means to shift said cylinder block in the other direction from said maximum volume position to reduce the effective length of the pumping stroke of the pistons.

2. A pump comprising a pump housing providing a fluid chamber therein, an inlet port to said fluid chamber, an outlet port on said pump housing, a cylinder block mounted for slidable movement within said fluid chamber along a longitudinal axis, a plurality of cylinder bores in said cylinder block, a piston within each of said cylinder bores, means in said pump housing to progressively reciprocate said pistons in said cylinder bores between forward and retracted positions, means connecting each of said cylinder bores to said outlet port, an inlet port for each cylinder bore in :said cylinder block, said port having axially spaced edges, said cylinder block defining a maximum volume position when the piston head is intermediate said port edges when the piston is in the retracted position, manual control means on the exterior of said pump housing adapted to shift said cylinder block along said longitudinal axis, said manual control means being operable to shift said cylinder block in one direction from said maximum volume position to reduce the effective area of said cylinder bore inlet ports, said manual control means being operable to shift said cylinder block in the other direction from said maximum volume position to reduce the effective length of the pumping stroke of the pistons.

3. A pump comprising a pump housing providing a fluid chamber therein, an inlet port to said fluid chamber, an outlet port on said pump housing, a cylinder block mounted for slidable movement within said fluid chamber along a longitudinal axis, a plurality of cylinder bores in said cylinder block, a piston Within each of said cylinder bores, means in said pump housing to progressively reciprocate said pistons in said cylinder bores between forward and retracted positions, check valve means connecting each of said cylinder bores to said outlet port, an inlet port for each cylinder bore in said cylinder block, said port having axially spaced edges, said cylinder block defining a maximum volume position when the piston head is intermediate said port edges when the piston is in the retracted position, manual control means to shift said cylinder block in one direction from said maximum volume position to reduce the effective area of said cylinder bore inlet ports, and control means responsive to fluid pressure in said outlet port to shift said cylinder block in the other direction from said maximum volume position to reduce the effective length of the pumping stroke of the pistons.

4. A pump comprising a pump housing providing a fluid chamber therein, an inlet port to said fluid chamber, an outlet port on said pump housing, a cylinder block mounted for slidable movement Within said fluid chamber along a longitudinal axis, a plurality of cylinder bores extending axially through said cylinder block, a piston within one end of each of said cylinder bores, wobble plate means in said pump housing to progressively reciprocate said pistons in said cylinder bores between forward and retracted positions, a tubular reaction piston within the other end of each of said cylinder bores, said reaction pistons having the same diameter as said pistons, check valve means on said pump housing adjacent each of said tubular reaction pistons, means connecting each of said check valve means to said outlet port, an inlet port for each cylinder bore in said cylinder block, said port having axially spaced edges, said cylinder block defining a maximum volume position when the piston head is intermediate said port edges when the piston is in the retracted position, means to shift said cylinder block in one direction from said maximum volume position to reduce the effective area of said cylinder bore inlet ports, and means to shift said cylinder block in the other direction from said maximum volume position to reduce the effective length of the pumping stroke of the pistons.

5. A pump comprising a pump housing providing a fluid chamber therein, an inlet port to said fluid chamber, an outlet port on said pump housing, a cylinder block mounted for slidable movement within said fluid chamber along a longitudinal axis, a plurality of cylinder bores extending axially through said cylinder block, a piston within one end of each of said cylinder bores, wobble plate means in said pump housing to progressively reciprocate said pistons in said cylinder bores between forward and retracted positions, a tubular reaction piston within the other end of each of said cylinder bores, said reaction pistons having the same diameter as said pistons, check valve means on said pump housing adjacent each of said tubular reaction pistons, passage means connecting each of said check valve means to said outlet port, an inlet port for each cylinder bore in said cylinder block, said port having axially spaced edges, said cylinder block defining a maximum volume position when the piston head is intermediate said port edges when the piston is in the retracted position, manual control means on the exterior of said pump housing operable to shift said cylinder block along said longitudinal axis, said manual control means being operable to shift said cylinder block in one direction from said maximum volume position to reduce the effective area of said cylinder bore inlet ports, said manual control means being operable to shift said cylinder block in the other direction from said maximum volume position to reduce the effective length of the pumping stroke of the pistons.

6. A pump comprising a pump housing providing a fluid chamber therein, an inlet port to said fluid chamber, an outlet port on said pump housing, a cylinder block mounted for slidable movement within said fluid chamber along a longitudinal axis, a plurality of cylinder bores extending axially through said cylinder block, a piston within one end of each of said cylinder bores, wobble plate means in said pump housing to progressively reciprocate said pistons in said cylinder bores between the forward and retracted positions, a tubular reaction piston within the other end of each of said cylinder bores, said reaction pistons having a diameter equal to the diameter of said pistons, check valve means on said pump housing adjacent each of said tubular reaction pistons, passage means connecting said check valve means to said outlet port, an inlet port for each cylinder bore in said cylinder block adjacent the head of the piston therein when the piston is in the retracted position, manual control means on said pump housing operable to shift said cylinder block in one direction to reduce the effective area of said cylinder bore inlet ports, and control means responsive to fluid pressure in said outlet port to shift said cylinder block in the other direction to reduce the effective length of the pumping stroke of the pistons.

7. A pump comprising a pump housing providing a generally cylindrical fluid chamber therein, and inlet port to said fluid chamber, an outlet port on said pump housing, a guide member secured to said pump housing and extending longitudinally coaxial with said fluid chamber, a cylinder block mounted for axially slidable movement on said guide member, a plurality of cylinder bores extending axially through said cylinder block, a piston within one end of each of said cylinder bores, wobble plate drive means in said pump housing to progressively reciprocate said pistons in said cylinder bores between for- Ward and retracted positions, a tubular reaction piston within the other ends of each of said cylinder bores, said reaction pistons having the same diameter as said pistons and being axially slidable relative to said cylinder block and said pump housing, check valve means on said pump housing adjacent each of said tubular reaction pistons, spring means maintaining said reaction piston in sealing engagement with said check valve means, means connecting each of said check valve means to said outlet port, an inlet port for each cylinder bore in said cylinder block adjacent the head of the piston therein when the piston is in the retracted position, manual means to shift said cylinder block in one direction to reduce the effective area of said cylinder bore inlet ports, and control means responsive to fluid pressure in said outlet port to shift said cylinder block in the other direction to reduce the effective length of the pumping stroke of the piston.

8. A pump comprising a pump housing providing a generally cylindrical fluid chamber therein, an inlet port to said fluid chamber, an outlet port on said pump housing, a cylinder block slidably journaled in said pump housing for longitudinal movement therein, guide means preventing rotation of said cylinder block in said pump housing, a plurality of cylinder bores extending axially through said cylinder block, a piston within one end of each of said cylinder bores, wobble plate drive means in said pump housing to progressively reciprocate said pistons in said cylinder bores between forward and retracted positions, a tubular reaction piston within the other end of each of said cylinder bores, said reaction pistons having the same diameter as said pistons and being axially slidable relative to said cylinder block and said pump housing, check valve means on said pump housing adjacenteach of said tubular reaction pistons, spring means maintaining said reaction pistons in sealing engagement with said check valve means, passage means connecting each of said check valve means to said outlet port, an inlet port for each cylinder bore in said cylinder block, said port having axially spaced edges, said cylinder block defining a maximum volume position when the piston head is intermediate said port edges when the piston is in the retracted position, manual control means on the exterior of said pump housing operable to shift said cylinder block longitudinally within said pump housing, said manual control means being operable to shift said cylinder block in one direction from said maximum volume position to reduce the effective area of said cylinder bore inlet ports, said manual control means being operable to shift said cylinder block in the other direction from said maximum volume position to reduce the effective length of the pumpin stroke of the pistons.

9. A pump comprising a pump housing providing a fluid chamber therein, an inlet port to said fluid chamber, an outlet port on said pump housing, a cylinder block mounted for slidable movement within said fluid chamber along a longitudinal axis, a plurality of cylinder bores extending axially through said cylinder block, a piston Within one end of each of said cylinder bores, wobble plate drive means in said pump housing to progressively reciprocate said pistons in said cylinder bores, a tubular reaction piston within the other end of each of said cylinder bores, said reaction piston having the same diameter as said piston and being axially slidable relative to said cylinder block and said pump housing, check valve means on said pump housing adjacent each of said tubular reaction pistons, spring means maintaining said reaction pistons in sealing engagement with said check valve means, passage means interconnecting said check valve means and said outlet port, an inlet port for each cylinder bore in said cylinder block, said port having axially spaced edges, said cylinder block defining a maximum volume position when the piston head is intermediate said port edges when the piston is in the retracted position, a rocker 15 shaft in said pump housing extending transversely to said longitudinal axis, means interconnecting said rocker shaft and said cylinder block whereby rotation of said rocker shaft moves said cylinder block axially, lever means exteriorly of said pump housing for rotating said rocker shaft, whereby movement of said control lever in one direction from the maximum position with respect to said pump housing shifts the position of said cylinder block to reduce the effective output volume of the pump by decreasing the effective length of the stroke of said pistons, and movement of said lever in the other direction from said maximum position shifts said cylinder block to reduce the effective output volume of the pump by reducing the efiective inlet port area.

References Cited in the file of this patent UNITED STATES PATENTS LOrange May 19, 1936 Cameron Feb. 13, 1945 Tuck et al July 4, 1961 FOREIGN PATENTS Great Britain Dec. 7, 1933

Claims

1. A PUMP COMPRISING A PUMP HOUSING PROVIDING A FLUID CHAMBER THEREIN, AN INLET PORT TO SAID FLUID CHAMBER, AN OUTLET PORT ON SAID PUMP HOUSING, A CYLINDER BLOCK MOUNTED FOR SLIDABLE MOVEMENT WITHIN SAID FLUID CHAMBER ALONG A LONGITUDINAL AXIS, A PLURALITY OF CYLINDER BORES IN SAID CYLINDER BLOCK, A PISTON WITHIN EACH OF SAID CYLINDER BORES, MEANS IN SAID PUMP HOUSING TO PROGRESSIVELY RECIPROCATE SAID PISTONS IN SAID CYLINDER BORES BETWEEN FORWARD AND RETRACTED POSITIONS, MEANS CONNECTING EACH OF SAID CYLINDER BORES TO SAID OUTLET PORT, AN INLET PORT FOR EACH CYLINDER BORE IN SAID CYLINDER BLOCK, SAID PORT HAVING AXIALLY SPACED EDGES, SAID CYLINDER BLOCK DEFINING A MAXIMUM VOLUME POSITION WHEN THE PISTON HEAD IS INTERMEDIATE SAID PORT EDGES WHEN THE PISTON IS IN THE RETRACTED POSITION, MEANS TO SHIFT SAID CYLINDER BLOCK IN ONE DIRECTION FROM SAID MAXIMUM VOLUME POSITION TO REDUCE THE EFFECTIVE AREA OF SAID CYLINDER BORE INLET PORTS, AND MEANS TO SHIFT SAID CYLINDER BLOCK IN THE OLTHER DIRECTION FROM SAID MAXIMUM VOLUME POSITION TO REDUCE THE EFFECTIVE LENGTH OF THE PUMPING STROKE OF THE PISTONS.