US2624174A - Hydraulic jack - Google Patents

Description

J. LOEF HYDRAULIC JACK Jan. 6, 1953 wn/mp 1 JA/fa 0f/f Arr/3 Patented Jan. 6, 1953 UNI-TED STATES PATENT OFFICE 1949,' Serial No; 86,471 October 1; 1948 'v claims. (c1. en -52.)

Applicatinn April 9, InGermany This yinvention relates .to hydraulic units. for lifting tackles. such as lifting. jacks for, vehi-cles, lift. trucks and similar devices equipped with hydraulic units consisting of a pump unit, a motor unit, a reservoir for the hydraulic fluid, andthe customary accessory equipment.

Limiting the maximum travel of the motor unit'in hydraulic devices of this character is ordinarily accomplishedby the `useof mechanical stops. Since the forces involved are very large, these stops must be of relatively large dimensions. In spite of their large size, breakage ofthe stops occurs relatively frequently.

This invention deals with the problem of providing means for limiting the maxi-mum travel of the mot-or piston which is especially intended for utilization in apparatus in which the pump piston, p ump cylinder, motor piston, motor cylinder and storage reservoir are'arranged'cof'axi'ally The sole''gure shows an embodiment of my in` vention wherein the pump unit 4, Zis co-axially positioned within themot'orlp'iston II.` This 'arrangement ofthe pump unit inthe hollow motor piston vII ofthe motor unit I, II permits limiting the stroke of the motor piston vI I, or ofthe motor cylinder I, without the'necessityY for providing stops'or providing slits in the compression cylinder I. In thisway difficulties in operation which might otherwise occur because of the presence of such 'stop members. are, to a very great extent, completely avoided.

Referring specifically to the drawing, the motor-'piston I I is hollow. Pump cylinder!! with its pump; piston .29 are positionedwithinitlie motor piston II.A A' cylindrical continuation 62 ofthe mot-or pistonA I I isy also hollow, vand is in communication with the'pumping cavity within the motor piston. It is traversed by the pumppistcn 2D; which is Vformed withthe eye 6 vat its end.' This eye, in the con-struction shown, is situated betweenthetwo cheeks 1, which are carried Vby the continuation 62, or by arotatable ring 13,'so that there can be relativeaxial movement between the cheeks 1 and the pump piston 20. The interior of 'extension'IZ vserves as a supply reservoir 33 -for the hydraulic liiuid.

The -wall- 62'of reservoir 33 is stiiened by a reinforcement' Yat-the end opposite to eye 6. At the outer periphery of` the reinforcement 80,

there'is a jacket 1 I, fastened thereto by screws or4 bolts 12'. This jacket .or shell surroundsvthe compression cylinder, forming therebetween an intermediateI space or interstice 10. Jacket 1I is provided near the end of .the motor pistoni I with flanges 31 on one side, lout. `it iis. otherwisecpen on this side. Inthe intermediate spacelil there is av return compression spring 38, whichserves `for lowering or restoring the device to its initial condition when no load is present. The abutments for compression spring 38 are formed by the beads or flanges 31 on one end, and by closure member 52 of the compression cylinder I at the opposite end.

The pump piston 20 is subjected to the action of .a return compression spring 65, which spring, at one end, rests against ya recess'or shoulder in the pump piston 20 and, at the opposite end, rests against the right hand end of pump cylinderII. Along with lpump cylinder 4, there are positioned in motor piston II an insert 1|4 for th-e suction valve 24, an insert 15 for motor check valve 21 and a brake valve 4 I, 42.

Theibrake valve for retarding the return stroke ofthe motor piston consists of a pin 4I which passes through the left end of motor piston II and extends into the motor cylinder I. Com-l pression spring 28, acting on check valve ball 21, with its opposite end applies a load via aplate or flange to the pin 4I, which is provided with a tapered keyway or fiuid passage 42.

intake valve support 45 is Ipositioned within the insert 114, the intake valve support 445 containing intake check valve ball 24. Furthermore, a pusher element 46 consisting of a pin ijs axially movable in support 45. Finally, insertion member 14 is further provided with a channel 41 and hollowedeout porti-on 48, which makes for the unimpaired ow of the pumping liquid to the motor piston check valve comprising -hall 21. Pump pirstonZ has a conical recess 5l, the mouthedge 5t of which is intended to enter into alternating action with inlet valve ball 2-4, while the bottom of the conical recess is intended to press against pin 46, the oppositerend of which acts on the outlet valve ball 21.

Displacement `of pump piston 2i) beyond its dead center or ordinary limit of travel (to the left in the drawing), will cause piston 20 and a ringlilre exten-sion thereof, 8i to lift the two check valve balls 24 and 21 from their respective seats at the same time retaining .a circular configuration at the end of the piston 2li. The left end of piston 23 can therefore be turned at will without impairing the opening of the ball check valves.

Screwed into thei ront side of pump piston 20, there is va hollow threaded plug 68, which `is intended to engage and displace pin 46 so as'to open 'the moto-r check valve 21. As the position of this threaded plug 68 is longitudinally adjustablewith respect to piston `2li. itsdistance awayl from :push

pin 46 can be varied, and it can thus lbe seen that substantially simultaneous opening of the two ball check valves 24 and 21 takes place.

In the present embodiment of my invention, a safety valve is disposed within the pump plunger 25. For vthis purpose, lanother hollow threaded plug 69 is screwed into plunger 20, behind threaded plug B8, its channel being closed by the springloaded safety valve ball I8. From safety valve ball I8, an axial bore 22 in piston 20 leads, via a radial channel 1B, into an annular space 60 between pump cylinder 4 and compression piston II.

An annular space S is provided between oompression piston II and the compression cylinder I. Channel 49 of suction valve 24 leads into this annular space and, furthermore, the wall of the compression cylinder I I is provided with a channel 6I which connects the annular spaces 58 and 60. Collar 59 of the motor piston closure member 52 is positioned to shut off the openings of channels 49 and 6i, said closure member closing 01T the openings of pump intake channel 49 and the channel 6I leading from the reservoir 33 into the annular space 58 upon completion of the full stroke of motor cylinder I I.

The operation of my improved hydraulic unit will now be described.

The hydraulic liquid is drawn, upon the intake stroke of piston 2i] (to the right), out of the reservoir 33, via the annular passage S9, the opening 6I the external annular passage 53 and the pump intake opening de, when the suction valve 24 is lifted. The power stroke of piston 2Q to the left forces the hydraulic recess 4B, the housing 42 of brake valve 4I,

of spring 28 and the keyway into cylinder I. The return stroke of the pump piston 2d is eiected by the spring 65. In the course of the power stroke compression cylinder I is moved to the left in the drawing. In accordance with the amount of pressure of the hydraulic uid during the return stroke of the motor piston II, the pin 4i is displaced against the action of compression spring 28, the pin 4I moving towards the right in the drawing. With increased displacement of pin 4I toward the right the effective flow crosssection is reduced by reason of the tapering of the keyway or slot 42. This cushions the return stroke and meters the return iiow through keyway 42.

With the displacement of cylinder I during the power stroke, the sealing collar 59 comes closer and closer to the mouth of the two channels 6I and 49. Finally, it happens that, first, the mouth of channel 5I (and, possibly thereafter if displacement of motor piston I I is continued the mouth of channel 69), is covered by the collar, so that the pump piston 2 can no longer draw out pressure liquid during the suction part of the stroke from the annular spaces 58 and 6I), or from the reservoir 33. In this way, the pumping is terminated, and this also results in termination of the power stroke of the motor cylinder and motor piston.

With the lifting of check valve balls 24 and 27 from their seats by maximum displacement of pump piston 2Q, (towards the left in the drawing), the liquid contained in compression cylinder i can flow back during the return stroke. The collar 59 which, incidentally is made of metal, is not stressed at any time by the closing of the passages EI and 49, inasmuch as it is not under pressure.

.. There is connected to channel 6I, at the outer fluid through channel 41,

wall of compression piston I I, a groove extending in the direction of channel 49. By means of this groove any hydraulic fluid in the annular space 58, which remains after the termination of the stroke, is reduced to a minimum amount, and return of the pressure liquid into the annular spaces 60 and the supply receptacle 62 is facilitated.

It should of course be understood that various changes and modifications can be made in my invention as herein described which would fall within the scope of my invention, and it is my intention that such changes or modifications as are within the purview of the appended claims shall be considered as part of my invention.

What I claim is:

1. A hydraulic unit of the class described, comprising: a motor cylinder, a motor piston movably disposed within the motor cylinder and having a pump cylinderand closable pump inlet passage formed therein said pump cylinder communicating through outlet check valve means with the motor cylinder; a pump piston reciprocally disposed within the pump cylinder; a reservoir adapted to contain hydraulic fluid; inlet check valve means carried by the motor piston and disposed to admit iluid from the reservoir through said pump inlet fluid passage into the pump cylinder upon the suction stroke of the pump piston; and closure means carried by the motor cylinder and disposed to close said pump. inlet fluid passage in response to a predetermined maximum movement of the motor piston relative to the motor cylinder, whereby the maximum stroke of the motor piston is limited by making the pump ineiective.

2. A hydraulic unit according to claim l, wherein said pump inlet fluid passage comprises two open ends successively closable by said closure means.

3. A hydraulic unit according to claim 1, yfurther comprising a return flow regulating member carried by the motor piston, sai-d regulating member being yieldingly movablewith respect to said motor piston and having a tapered passageway formed therein, said passageway being progressively restricted during the final period of motor retraction for metering the rate of said return flow.

4. A hydraulic unit of the class described, comprising: a pump piston; a motor piston having a pump cylinder formed therein, said pump piston being reciprocably disposed within said pump cylinder, said motor piston having rst and second fluid passages formed therein, said rst fluid passage extending from the exterior portion of said motor piston into said pump cylinder; a rst check valve means carried by said motor piston and disposed in said first iluid passage for admitting iiuid into said pump cylinder; a reservoir adapted to receive hydraulic fluid; a motor cylinder within which said motor piston is movably disposed, a third iluid passage formed in -said motor piston, said third passage being closable and communicating between said reservoir and said rst uid passage, said second fluid passage communicating between said pump cylinder and said motor cylinder; a. second check valve meanscarried by said motor piston and disposed in said second iluid passage for admitting uid from said pump cylinder into said motorl cylinder; and closure means carried by said motor cylinder and effective after a predetermined of said motor piston and t0yk maximum movement close said rst fluid passage.

5. A hydraulic unit according to claim 4, wherein said closure means is disposed to close said third iiuid passage prior to the closure of said first fluid passage.

6. A hydraulic unit according to claim 4, wherein said pump cylinder and said motor cylinder are coaxially disposed, said third fluid passage communicating with a space intermediate the internal surface of said motor cylinder and the external surface of said pump cylinder,

7. A hydraulic unit according to claim 4, fui'- ther comprising release means carried by said pump cylinder and operative in an extreme pressure stroke position of travel of said pump piston for opening both said first and second check Valve means to permit reverse fluid flow therethrough; and flow retarding means disposed in said second uid passage for metering the rate of said reverse flow during the final period of motor retraction.

JAKOB LOEF.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATNTS Number Name Date 947,613 Gathrnann Jan. 25, 1910 1,080,062 Hess Dec. 2, 1913 1,201,180 Hennessy Oct. 10, 1916 1,611,703 Zabriskie Dec. 21, 1926 1,709,000 Bolens Apr. 16, 1929 1,819,378 Nilson Aug. 18, 1931 2,146,403 Nilson Feb. 7, 1939 2,187,279 Nilson Jan. 16, 1940 2,359,060 Strom Sept. 26, 1944

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