US2781728A - Pneumatically powered hydraulic pump - Google Patents

Description

Feb. 19, 1957 H. RHSCHER ETAL 2,781,728

PNEUMATICALLY POWERED HYDRAULIC PUMP 5 Sheets-Sheet 2 Filed March 2. 1954 Feb. 19, 1957 H. R. FISCHER ETAL 2,781,728

PNEUMATICALLY POWERED HYDRAULIC PUMP 5 Sheets-Sheet 3 Filed March 2. 1954 E ATTO RN EY sur Eni @Mmm .mTLP

4 Feb. 19, 1957 H. R. FISCHER ETAL 2,781,728

PNEUMATICALLY POWERED HYDRAULIC PUMP Filed March 2.' 1954 5 Sheets-Sheet 4 ThE/1.11.

ATTORNEY Feb. 19, 1957 Filed March 2,- 1954 H. R. FISCHER ET AL PNEUMATICALLY POWERED HYDRAULIC PUMP 5 Sheets-Sheet 5 W rl/ United States Patent O PNEUMATICALLY POWERED HYDRAULIC PUMP Howard R. Fischer and Marcel P. DHaem, Utica, N. Y., assignors to Chicago Pneumatic Tool Company, New York, N. Y., a corporation of New Jersey Application March 2, 1954, Serial No. 413,980

9 Claims. (Cl. 10S-50) This invention relates to pumps and more particularly to pumps which comprise a pneumatic and hydraulic combination.

Briey, the invention comprises a pump arrangement including a pneumatically powered piston which is automatically operated in a rapid succession of power strokes to pressurize a hydraulic medium taken from an integrally arranged reservoir, the pressurized medium being fed intermittently into a conduit attached to a jack, or other tool, and being fed back into the reservoir after the pumping operation is terminated. The feed back of the hydraulic medium to the reservoir may be accomplished by a manual pressure release means, or by an improved automatic pressure release valve, as desired. The pump of the invention may be operated from a pneumatic source at 90 pounds per square inch, and will deliverV hydraulic medium at 8000 p. s. i.; however, such values are merely representative, and the structural proportions of the invention may be varied to give practically any operating characteristics desired.

The main object of this invention is to provide a pump arrangement which will furnish a high pressure hydraulic delivery when connected to a low pressure pneumatic source.

Another object is to provide a pump having an improved pneumatically operated arrangement, and an improved automatic pressure release valve for return kilow of a hydraulic medium.

A further object of this invention is to provide a pump which has low initial and maintenance costs, is structurally compact, and of relatively small size and low-weight.

These and further objects and features of the invention will become more apparent when viewed in the light of the following specication and the accompanying drawings wherein:

Fig. 1 is an elevational view of a pump arrangement embodying the elements of applicants invention; n

Fig. 2 is a view, chiefly in longitudinal section, taken through the pump of Fig. l, but drawn in a much larger scale, and with a portion of the reservoir broken oli;

Fig. 2A is a section view as seen from line 2A-2A1'n Fig. 2.

Fig. 3 is a section view of an automatic valve of the pump as seen from line 3 3 in Fig. 2;

Fig. 4 is a section view showing a pneumatic inlet, a-

,start of .a pressurizing stroke of the pump piston, and at the beginning of the return stroke ofv said piston'respectively.

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Referring now to Fig. l, the pump comprises an assembly 19 including a hydraulic portion 20, a pneumatic portion 21, and a reservoir portion 22, all of said portions being held together by conventional fastening means. A handle, or frame means 23, may be aixed to the pump assembly for the convenient transportation thereof; if desired, saidframe means 23, may incorporate a wheel arrangement to provide for easy maneuvering of the pump assembly.

The pneumatic portion 21, which includes a pneumatic valve block 24, is aflixed to a cylinder 26, the latter of which engages a hydraulic valve block 27, all being held together as shown in Fig. 2, by bolt means 2S, or equivalent. A piston chamber 25 formed within the cylinder 26, contains a piston assembly 29, which includes a hydraulic ram 31. extending into a pressurizing chamber 32, formed in the valve block 27, and a spring 33 compressively arranged between the piston assembly and the hydraulic valve block 27.

Throttle valve Within the pneumatic valve block 24, as best seen in Figs. 2, 3 and 4, are vertically disposed a throttle valve recess 34, a distributor valve recess 36, and a safety valve recess 37. Also located in the block is a horizontally disposed automatic valve recess 38. An air inlet recess 39, in which is threadab'ly arranged a street L 41, has a passageway 42 leading into the throttle valve recess 34. An air strainer 43, positionally maintained by compression spring 44, is arranged within the air inlet recess 39, as shown in Fig. 4.

At the lower end of the throttle valve recess 34 is a valve cap 46, which is restrained against downward movement by an O ring 47, while at the upper end of the throttle valve recess 34, is a valve bushing 48, whichv is press tted in the position shown. Slidingly arranged within the bushing 48 is a throttle valve 49, the lower end of which has a head portion 51 for air tight engagement with a valve seat 52. A spring 53, compressively arranged between the valve cap 46 and a lower surface of the valve head portion 51, constantly urges the throttle valve upwardly, so that the valve will seat in air tight manner. On the outer periphery of valve bushing 4S are'two circumferential grooves 54 and 56, each of which have radial holes 57 and 58 respectively, leading to the inside of the bushing. The throttle valve 49 has a reduced diameter portion 59 of length slightly greater than the distance between the radial holes 57 and 58. Within the valve block 24 are arranged an exhaust bore 61 in alignment with the valve groove 56, and a bore, or passageway 62,

which leads from the throttle valve recess 34, in the rei gion of the valve groove 54, to the automatic valve recess 38. Pivotally affixed to the top of the valve block 24, is a throttle lever 63, the underside of which is arranged to `abut the projecting end of the throttle valve 49.

In non-operative condition of the pump, the throttle valve 49 and throttle lever 63 are in the position shown in Fig. 2, wherein live air from inlet passageway 42, is trapped within the lower portion of the throttle valve recess 34 by reason of the throttle valve head 51 being seated on valve seat 52, and any air in passageway 62 is free to escape to atmosphere via valve groove 54, radial holes 57, about reduced valve portion 59, radial holes 58, valve groove 56, and exhaust bore 61. In operative condition of the pump, the throttle lever 63 is depressed to unseat the valve 'head portion 51 from the valve seat 52, so that air will flow thereabout, and around the reduced valve portion 59 into radial holes 57, and valve groove 54, then into passageway 62, While the exhaust air circuit through radial holes 58 etc., will be cut off by the upper portion of thethrottle valve, as will be apparent.

Arranged within the automatic valve recess 38 are a valve bushing 64, two identical valve caps 66 (one at each end),` and an automatic valve 67. On the outer periphery of. the valve bushing 64, are, formedy three circumferential grooves 68, 69 and 71', each being connected to the inside of the valve bushing by a plurality of radially disposed holes 72, 73, 74 respectively. The valve bushing 64 is press fitted within the recess. 38, andY the ends thereof are arranged between two passageways 76, 77 formed in the valve block 24, as best seen in Fig. 3. Bushing groove 68 is positioned in alignment with a vertically arranged bore '78 leading into a recess 79 in which is threadably aixed a pipe fitting (street L.) 81. Bushing groove 69 is positioned in alignment with a bore 82 extending downwardly, and opening into the cylinder portion 26. Bushing groove 71 is positioned in alignment with an exhaust air passageway 83. A valve balancing passageway 84 is arranged in the valve block 24, whereby part of the live air entering the bore 78, will be conducted to each end of the valve recess 38, and directed therein at each end of the valve bushing 64, and approximately inline with the passageways 76, 77.

The valve caps 66 have a snug tit within the recess 38, and are locked against outward movement by means of retaining rings 86. On the inner side of each cap 66 is a recess S7, of slightly larger diameter than that of the automatic valve 67, and which is adapted to contain an end of said valve during certain phases of the pump operating cycle. The automatic valve 67, which is slidably arranged in the bushing 64, has a reduced diameter midportion 8S, the length of which is approximately equal to the maximum distance between radial holes 72 and 73, or radial holes 73 and 74, while each end of the valve 67 has a bore 89 for purposes of reducing the weight thereof.

It will be seen that with the automatic valve 67 in the position shown in Fig. 3, any live air coming from passageway 62, can flow into valve groove 68, through bore 78 and into pipe fitting 81, and simultaneously through balancing passageway 84 to each end of the valve recess 38; also air in the cylinder portion 26, can escape to atmosphere through bores 82, into groove 69, about the reduced portion 88 of the automatic valve 67, through radial holes 74, into groove 71, and through exhaust air passageway 83. When the automatic valve 67 is shifted to the opposite end of the recess 38, in a manner which will later be discussed, live air coming from passageway 62, can iiow from groove 68, through radial holes 72,

around the reduced portion 88 of the valve 67, through i radial holes 73, into groove 69, and then Ithrough bore 82 into the cylinder portion 26; also escape of air to atmosphere is blocked because an end portion of the valve 67 closes off radial holes 74. lt should be noted, that during the entire time the throttle lever 63 is depressed, air is being delivered, via certain passageways and bores as above discussed, to the pipe lifting 81.

Distributor valve Within the distributor valve recess 36, and in press iit relation thereto. is a distributor valve bushing 91, said valve bushing having two circumferential grooves 92, 93 on the outer periphery thereof. Extending through the bushing from groove 92, are two sets of radial holes 94, 96, While one set of radial holes 97 extend through the bushing from groove 93. The end of passageway 76 opens into the automatic valve recess 36 in .the region of groove 92, while the end of passageway 77 opens into the recess 36 in the region of groove 93, Slidingly arranged in the valve bushing 91, is a distributor valve 9S having a head portion 99 extending into the piston chamber Z and being connected yto a piston 101 of the piston assembly 29. The head portion 99 abuts a ram head spacer 102, which is positioned between the bottom surface of the piston 101 and a ram return Washer 103. By

means of such arrangement, it will be seen, that as the piston 101' moves in the piston chamber 25, it will move the distributor valve 98 with it. The distributor valve is bored to provide a hollow portion 104, and has two sets of radial holes 106, 107, the latter of which opens into a circumferential groove 108 formed on the outer pcriphery of the valve as seen in Fig. 2. An exhaust holc 109. is formed in the, upper end of the recess 36.

When the distributor valve 98 is in the position shown in Fig. 2', passageway 76 is opened to the atmosphere via valve groove 92, radial yholes 96, valve bore 104, radial holes 106, recess 36, and exhaust air hole 109; at the A same time passageway 77 is closed to the atmosphere,

since the distributor valve 98 is blocking radial holes 97. When the piston 101 moves downwardly in `the piston chamber 25 during pump operation, the distributor valve closes radial holes 94, 96 and toward the end of such downward movement, uncovers radial holes 97, so that passageway 77, will be open to the atmosphere via recess 36, and exhaust air hole 109.

Safety valve Positioned within the safety valve recess 37 is a safely valve assembly consisting of a valve seat bushing 111, a check valve 112, a valve spring 113, an adjusting screw 114, and a valve cap 116. The bushing 111 is press fitted within the recess 37 so that its bottom edge is flush with the lower surface of the valve block 24 within the piston chamber 25 of the cylinder assembly 26. An exhaust air passageway 117 is formed in the valve block 24, and is positioned a short ldistance above the `top edge of the bushing 111. The check valve 112 is slidably a1'- ranged with the valve recess 37 and is urged toward seating engagement with the top edge of the bushing 111, by means of the spring 113 which is compressivcly maintained between .the check valve 112 and the adjusting screw 114. Valve cap 116 is threadably affixed in the end of the recess 37, and the adjusting screw 114 has a threaded engagement within the cap. A relief passageway 118, formed in the valve block 24, exhausts air bchind the valve 112, so that said valve need operate only against the pressure of spring 113.

By manipulation of adjusting screw 114, and assuming that spring 113 is properly designed, it will be seen that the valve 112 can be fixed for unseating at any value of air pressure within the piston chamber 2S. Once the pressure in the piston chamber exceeds the value for which the check valve 112 is set, the latter will be unseated, thereby releasing the air pressure in the piston chamber to the atmosphere. In the pump illustrated, the safety valve will remain seated until the air pressure in the piston chamber 25 is such as to provide a hydraulic pressure in excess of 8000 p. s. i.

Hydraulic arrangement The reservoir portionv 22 of the pump assemblage, comprises a cylindrical tank 119, having two openings 121, 122, an inlet boss 123 iixedly secured to the tank at opening 121, an oulet boss 124 fixedly secured to the tank at opening 122, a filler cap 126 and oil gage 127 assembly, and a handle means 128. An air inlet conduit 129 connects with the pipe fitting 81, and leads into the inlet boss 123 as shown. The ller cap 126 is threadably mounted in the inlet boss 123, and has an integrally formed cylindrical shank 131, which includes a flared lower portion 132' arranged to set just inside the tank 119, to serve as adeector for incoming air. The oil gage 127 is formed integral with the shank 131. Oil, or other suitable hydraulic medium is placed in the reservoir, preferably to the level indicated. Keeping in mind the air circuit previously described, it will be seen that when the throttle lever 63 is depressed, live air pressure will be exerted against the top surface of the oil in the tank 119.

A recess 132 formed in the hydraulic valve block 27, extends from the outer surface of the valve block to the pressurizing chamber 32. Within the recess 132 is a check valve assembly including a check valve seat bushing 133, a check valve 134, a spring 136, and a spring abutment 137. The valve seat bushing is arranged to abut the outside surface of the outlet boss 124, and has a recess 138, in which is positioned a frustro-con'ical strainer' 139 surrounding the end of an elongated tubular Strainer 141, the latter of which extends through the outlet boss 124 and tank opening 122, into the tank 119. 'l'he check vave seat bushing 133 has a bore 142 extending from the recess 138 to the inner end face of the valve seat, whereon is formed a seating surface against which the check valve 134 can seat in a uid tight manner. Check valve 134 is maintained in slidable position within the recess 132 by virtue of a flange portion 143, the edges of which are squared, as best seen in Fig. 2A, to provide for ow of hydraulic medium about the iiange portion. The spring 136 is compressively arranged between the flange portion 143 and the abutment 137, to urge the valve 134 in seated position against the end of the valve seat 133, It will be apparent that the check valve assembly described, allows for one way flow of hydraulic medium from the tank 119 to the pressurizing chamber 32 when the check valve 134 is unseated.

Referring now more particularly to Fig. 5, it will be seen that a second check valve assembly is arranged in the valve block 27, and is positioned within a recess 144 extending from the outer surface of the valve block to the pressurizing chamber 32. The second check valve assembly includes a check valve seat bushing 146, a check valve 147, a valve spring 148, a spring abutment 149, and a valve plug cap 151. The valve seat bushing 146 is positioned within the recess 144 between the pressurizing chamber 32 and a bore 152, which enters the recess 144 and connects with an enlarged bore 153, the latter of which extends to the outer surface of the valve block 27, and is threaded to receive a high pressure pipe fitting 154 and hose 156. Valve spring 148 is compressively arranged between the valve 147 and the abutment 149, the latter of which is maintained in position by means of the valve plug cap 151, which is threadably arranged within the end of recess 144. Spring 148 constantly urges the valve 147 toward fluid tight seating engagement with the end of the valve seat 146. Valve 147 has a squared flange portion 157, similar in shape and function to the flange portion 143 of the check valve 134 of the first described check valve assembly. lt will be apparent that the second check valve assembly, allows for one way flow of hydraulic medium from the pressurizing chamber 32 to the high pressure hosef156 when the check valve 147 is unseated.

A passageway 158 extends from the enlarged bore 153 to a bore 159, the latter of which is concentric with a hydraulic pressure release chamber 161 which has an enlarged end portion 160 for threadably receiving a manual release valve 162. Within the pressure release chamber 161 is a release Valve ball 163, which may be held in seated engagement with the end of bore 159 by means of an elongated portion 170 of the release valve 162. A passageway 164 extends from the pressure release chamber 161 and connects with passageway 166 (Fig. 2), one end of which connects with the check valve recess 132, while another passageway 165 is formed between the enlarged end portion 160 of the pressure release chamber 161 and the passageway 164. A plurality of radially arranged holes 167 in the check valve seat 133, allows hydraulic medium from the passageway 166 to return to the reservoir, or tank 119.

As should now be apparent, return ow of hydraulic medium from the high pressure hose 156 to the tank 119, cannot occur by way of the two check valve assemblies, but rather will occur through passageway 158, bore 159, pressure release chamber 161, passageways 164 and 166, through radial holes 167 of the check valve seat 133, and then to the tank 119. lf the release valve ball 163, is

held in contact with .the end of bore 159 by means of the release valve portion 170, the return ow circuit will be disrupted and the accumulated pressure in high pressure hose 156 will be maintained. Auxiliary means for automatically returning the hydraulic medium to the tank after cessation of pump operation, will later be described. Considering pressurizing chamber 32, it will be seen; that said chamber is located at the lower end of a vertical bore 168 formed in the valve block 27. A ram bushing 169 is press fitted in the bore 168, and is adapted to slid-- ingly receive the hydraulic ram 31. High pressure packing Imeans 171 surrounds the ram at the Vend of bushing 169, to prevent seepage of pressurized hydraulic medium into the piston chamber 25. The bushing 169 has a slightly increased inner diameter portion 172 at the upper end, and a radial hole 173 connecting the portion 172 to a vertical slot 174 formed on the outer surface of the bushing. Slot 174 extends to a circumferential groove 176, formed on the bore 168, and the passageway 166 intersects said groove 176. Any pressurized hydraulic medium which seeps by, or is drawn along, the ram will be returned to the tank 119, `via portion 172, hole 173,' slot 174, groove 176 and passageway 166.

Hydraulic ram 31 is provided with a head portion 177 which is arranged in a recess 178 formed on the lower side of the head spacer 102, the bottom surface of said head portion 177 engaging the return washer 103. It will be seen that the ra-m 31 will be forced downwardly toward the pressurizing chamber 32 by the piston 101 during a hydraulic pressurizing stroke, and will be pulled upwardly by the return washer 103, as the spring 33 returns the piston 101 upwardly in the piston chamber 25. The valve block ,27 is connected with the tank 119 by means of two screws 179, one of' which is shown in Fig. 5,

. and which are threaded; into a bracket 181 aixed to the tank.

Automatic release valve Forl purposes of providing an automatic hydraulic medium return release, an automatic valve assemblymay be used in place of the manual release valve 162 and release valve ball 163. Referring more particularly to Figs. 6 to l0 inclusive, the automatic release valve comprises a cylinder 182 having a threaded extension 183, which is adapted to be screwed into the enlarged end portion 160, formed in the valve block 27. A piston 184, slidably arranged within the cylinder 182, has-a stem portion 136, the lowerend of which is slidably enclosed within the threaded extension 133. Threadedly secured within the upper end ofthe cylinder 182 is a cylinder cap 187, which supports a lock screw 18S having a handle 189 and a lock screw nut 191. A spring 192 surrounding the piston stem 186, is compressively maintained between the under surface of the piston 184 and the bottom of the cylinder chamber, as shown. The piston stem 186 is hollow and a plurality of radial holes 193 connect the interior of the piston stemto a reduced diameter end portion 194- Abutting the end portion 194 is a needle valve 196 which is slidably supported partly within a needle Valve seat bushing 197, the latter of' which abuts in fluid sealing manner, a valve 19S slidingly arranged within the pressure release chamber 161. A spring 199 is compressivel'y.Y arranged between the valve 198 and the end of the bore 159.

Valve 198, which is adapted to seat against a shoulder in bore 159, has a small diameter Vertical passageway 201 which extends from the seating end surface to an enlarged diameter `bore 202, which opens upon the Opposite end of the valve. Needle valve seat 197 has a small diameter vertical passageway 203, which extends from the seating end surface and opens into a larger diameter bore 204 in which the needle valve 196 is supported. The needle valve is pointed so that it can enter into the end of the passageway 203 and effectively seal off flow of hydraulic medium therethrough. A radial hole 206, formed in the needle valve seat bushing 197, connects the bore 204 with the lower end ofthe enlarged end portion 160; Although the needle valve seat bushing 197 abuts against the lower surface of the threaded extension 183, a sealing arrangement is not thereby provided because said extension 183, has a plurality of radially disposed slots 207 formed at the end thereof. It may be further noted that the volume under the piston 184 within cylinder 182, is vented by means of a relief hole 208.

With anunderstanding of the structure of the automatic release valve as above described, the purpose and function thereof will become readily apparent from a description of the pump operation, which will now be discussed.

Operation-Manual pressure release Referring now to Fig. ll, said diagrammatic sketch illustrates the relative position of the operative parts of the pump at the beginning of a hydraulic medium pressurizing stroke. The automatic valve 67 has been shifted to the extreme left by virtue of the fact that the live air, owing from passageway 62 and around groove 68, enters passageway 84 wherein it flows to both ends of the bushing 64 and escapes to atmosphere at one end thereof via passageway 76, bore 194, and hole 109, causing a pressure differential at opposite ends of the automatic valve 67 resulting in the shifting thereof. In such position of the automatic valve, live air tiows through radial holes 72, about the reduced mid-portion 8S of the automatic valve, through radial holes 73 and groove 69 to passageway 82, and into piston chamber 25, to act upon the piston 191 and drive the piston assembly 29downwardly. Prior to such downward stroke, live air owing from passageway 1129, exerted pressure on the hydraulic medium in reservoir 119, causing a portion of the medium to ow through opening 122 and unseat the valve 134, thereby lling the pressurizing chamber 32. The pressure of the hydraulic medium at this stage is not suicient to unseat the valve 147. As the ram 31 descends into-chamber 32, the pressure ofthe hydraulic medium is rapidly increased so that valve 134 will be seated, while valve 147 will be unseated, resulting in the ow of pressurized hydraulic medium into hose 156, and onward to the jack (not shown), or other tool. For purposes of clarification, the pneumatic medium How is indicated by single headed arrows, the unpressurized hydraulic medium by double headed arrows, and the pressurized hydraulic medium hv triple headed arrows.

/ts the piston 101 descends in the piston chamber 2S, the distributor valve 98 is drawn along until the position illustrated in Fig. l2 is realized. When this occurs, it will be seen that the air in passageway 77 isrexhausted to atmosphere via holes 97 and 109, while the end of passageway 75 is blocked by the wall of the distributor valve 98.` As a result, the air owing into the automatic valve recess 38 via passageway 84, causes a pressure differential to exist between the opposite ends of the automatic valve 67, whereby the latter is shifted to the extreme right position. In this position, the automatic valve 67 allows air to flow from the piston chamber 25, through passageway 82 and around the valve mid-portion 88, through radial holes 74 into groove 71, then to atmosphere via exhaust passageway 83. When the pressure atop piston 161 is thus released, spring 33, which was compressed during the downward stroke of the piston, will expand and return the piston 191 and ram 31 to initial position, as in Fig. ll. As the ram 31 is Withdrawn from the pressurizing chamber 32, valve 147 will be seated, and another slug of hydraulic medium will be forced into the chamber 32, in tthe manner, and for reasons already described. When the automatic valve 98 and piston assembly 29 approach the position indicated in Fig. l1, the automatic valve will be suddenly shifted toward the left, and another pressurizing strokeof the piston 191 will occur.

It should now be apparent that as long as the throttle valve 49=is depressed, allowing live-air ow into passageway 62, pumping action will be automatically effected. However, once the hydraulic medium being forced out of chamber 32 isY pressurized to the maximum valve commensurate with the air pressure acting atop piston 101, the ram 31 will be stalled, and further pumping action will be arrested. When such condition occurs, valve 147 will be seated, due to action of spring 148, and the hydraulic pressure in hose 156 will be maintained. To release the pressure in hose 156, valve 162 must be manually turned, whereupon ball valve 163 will be unseated allowing flow of hydraulic medium back into tank 119 via passageways 158, bore 159, chamber 161, passageways 164 and 166, recess 132, and holes 167 of check valve seat 13 The valve 162 will be operated for return iiow action of the hydraulic medium, only after the throttle valve i9 has been released, for if the ball valve 163 is unseated during pump action, the hydraulic uid will be short circuited, and it will not be possible to build up pressure in the hose 156.

Operation-Automatic pressure release In certain types of pump applications, it is desirable to have the hydraulic fluid in hose 156 return to the tank 119 automatically after the throttle valve lever 63 is released. For such purpose, the automatic valve assembly illustrated in Figs. 6 to l0 inclusive, may be used in place of the manual release valve 162, as heretofore pointed out.

Fig. 6 illustrates the position of the various movable parts of the automatic valve assembly, in non-operative position, i. e., before throttle valve 49 is depressed by throttle lever 63.

Fig. 7 illustrates the condition of the movable parts of the automatic valve assembly in the first stage of operation, i. e., just after the throttle valve 49 is depressed by the operator. Hydraulic medium under pneumatic pressure acting within the tank 119, flows through passageways 166 and 165 into enlarged end portion 160, through slots 207 and upwards through the hollow portion of the valve stem 136 to the top of piston 184, causing the latter to be forced downwardly as indicated. As the pump operates to pressurize the hydraulic medium entering hose 156, a portion of said hydraulic medium tows through passageway 158 into bore 159, and through passageway 261 of the valve 198, into the enlarged diameter bore 202 thereof. As the hydraulic pressure increases during pump operation, the total pressure acting against the lower surface of the needle valve seat 197 and the end of the needle valve 196, becomes greater than the total pressure acting atop piston 184, resulting in the upward movement of the piston 184, needle valve 196, and needle valve seat 197, so that the condition illustrated in Fig. 8 will prevail. In such position it will be seen that the top surface of the needle valve seat 197 is abutting the threaded extension 183, while the needle valve 196 remains seated in the needle valve seat 197.

Since the total hydraulic pressure acting atop piston 184` is greater than the total hydraulic pressure acting against the end of seated needle valve 196, the condition illustrated in Fig. 8 will remain fixed as long as the throttle valve of the pump is depressed.

When the throttle valve 49 is released by the operator at the finish of pump operation, the hydraulic pressure existing atop piston 184 is released, and the hydraulic medium ows back toward the tank 119 via the circuit which took the tluid to the top of the piston, while spring 192, which was compressed when the piston 184 was forced downwardly, expands and moves the piston to initial position. Thereupon needle valve 196 is unseated and the hydraulic medium holding the valve 198 seated against the end of bore 159, is released via hole.

206, all as illustrated in Fig. 9. Thespring 199 then unseats the valve 198, so that a quick return of'hydraulic medium to tank 119 is accomplished via passageway 158, bore 159, and passageways 164 and 166, leavingthe aveu/.as

various parts of the automatic valve as shown in Figi. 10, or initial condition.

The automatic valve assembly is arranged so that the hydraulic pressure in hose 156 may be maintained after pump operation ceases, i. e., after the throttle valve 49 is released by the operator, and in such manner can be operated to provide the same eifect as the manual release valve 162. To achieve such effect it is only necessary for the operator to turn the lock screw 13S so that it engages the piston 184 and forces the latter downwardly, so that the needle valve 196 moves the needle valve seat 197 in rm abutment with the valve 198, whereby the latter will be seated in the end of bore 159. In such position, the hydraulic medium in the hose 156, passageway 158 and bore 159, will be prevented from returning to the reservoir after pump operation ceases, and can only do so after the lock screw 18S is released by the operator from engagement with the piston 184, as will be apparent.

In constructing a pump embodying the principles of the invention, advantage should be taken of well known mechanical expedients to insure etlicient and satisfactory operation. In the specification, no speciiic mention is ordinarily made of means such as piston rings or seals, gaskets, and the like, but it is to be understood that these elements should be provided in the pump wherever necessary, and particularly where indicated in the related drawings.

What is claimed is:

1. A pump including in combination a pneumatic portion having a housing including a pressurized pneumatic medium inlet means, an automatic valve arranged in a recess formed in the pneumatic portion, an hydraulic portion having a housing including a pressurizing chamber, a reservoir portion having an enclosed reservoir for containing a supply of hydraulic medium, means to conduct pressurized pneumatic medium from the pneumatic portion to the surface of hydraulic medium in the reservoir, means including passageways to allow ow of hydraulic medium from the reservoir portion to the pressurizing chamber, a cylinder afxed to the housing of the pneumatic portion, a piston means reciprocably arranged in the cylinder and having a ram extendable into the pressurizing chamber, means including a distributor valve arranged in the pneumatic portion and aixed to the piston means, said distributor valve adapted to direct ow of pressurized pneumatic medium to operate the automatic valve so that the latter will direct ow of pressurized pneumatic medium into the cylinder to cause movement of the piston and the ram, an outlet means connected to the pressurizing chamber, and means including passageways to allow tlow of hydraulic medium from the outlet means to the reservoir when pump operation is terminated.

2. A pump according to claim 1, wherein a spring 10 means is arranged to move the piston means whereby the piston ram is withdrawn from the pressurizing chamber.

3. A pump according to claim 2, wherein a tirst check valve is arranged to permit tlow of hydraulic fluid from the reservoir portion to the pressurizing chamber, and a second check valve is arranged to permit How of hydraulic Huid from the pressurizing chamber to the outlet means.

4. A pump according to claim 3, wherein a manually operable pressure release valve is arranged in the hydraulic portion whereby hydraulic fluid in the outlet means may be returned to the reservoir portion without passing through the pressurizing chamber.

5. A pump according to claim 4, wherein a safety valve is arranged in the pneumatic portion whereby the pneumatic medium admitted to the cylinder to drive the piston means may be released to atmosphere when the pressure thereof exceeds a predetermined value.

6. A pump according to claim 5, wherein a throttle valve is arranged in the pneumatic portion whereby pneumatic medium may be admitted `to the automatic valve.

7. In a pump according to claim 1, an automatic pressure release valve arrangement for returning hydraulic uid from the outlet means to the reservoir portion and including a cylinder having a threaded extension for engagement with a threaded recess in the hydraulic portion, a piston slidably arranged in the cylinder and having a hollow stem portion, providing a passageway to the top of the piston, a needle valve positioned at one end in abutment with the end of the piston stem and adapted to the other end to seat in a hole of a needle valve seat which is slidably supported within the hydraulic portion, a valve slidably supported within the hydraulic portion and adapted at one end to abut the needle valve seat and to seat in the end of a bore formed in the hydraulic portion, and a resilient means arranged to urge the valve in the direction of the needle valve seat.

8. An automatic pressure release valve arrangement according to claim 7, wherein a resilient means is arranged to urge the piston upwardly in the cylinder.

9. An automatic pressure release valve arrangement according to claim 8, wherein means are provided for changing the valve to a manual release valve and including a lock screw for engagement with the piston whereby the latter may be maintained in downward position so that the needle valve and needle valve seat urge the valve in seated engagement with the end of the bore formed in the hydraulic portion.

References Cited in the le of this patent UNITED STATES PATENTS 1,485,138 Johnson Feb. 26, 1924 2,163,436 Raymond et al. June 20, 1939 2,588,164 Roberts et al. Mar. 4, 1952

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