US3782689A

US3782689A - Control means for hydraulic jack

Info

Publication number: US3782689A
Application number: US00222090A
Authority: US
Inventors: J Barosko
Original assignee: Tenneco Inc
Current assignee: McNeil Corp
Priority date: 1972-01-31
Filing date: 1972-01-31
Publication date: 1974-01-01
Anticipated expiration: 1991-01-01

Abstract

A sliding member between the high and low speed chambers of a two-speed hydraulic jack acts as a combined valve and seal. The member serves to separate these chambers during the quick-raise movement, but automatically connects them when a load is encountered so that the pump will feed both chambers.

Description

United States Patent 1191 Barosko Jan. 1, 1974 CONTROL MEANS FOR HYDRAULIC JACK 3,593,520 7/1971 Laundy 60/52 HA 3,134,232 5/1964 B sko 60/52 HA [75] mentor: Bamslw Kenosha 2,284,228 5/1942 P2; 60/52 HA [73] Assignee: Tenneco Inc., Racine, Wis.

- Primary ExaminerOthell M. Simpson [22] Filed' Jan- 1972 Att0rneyJ. King Harness et a]. [2]] App]. No.: 222,090

[57] ABSTRACT 52 US. Cl. 254 93 R 61 52 HA i51-i 1111.01 ..B6613 /24,i=151 15/18 A Sliding member between the high and Speed [58 1 Field of Search 254/93 RH- 60/52 HA chambers two'speed hydraulic jack acts as 3 60/97 91/412 bined valve and seal. The member serves to separate these chambers during the quick-raise movement, but [56] References Cited automatically connects them when a load is encoun- UNITED STATES PATENTS tered so that the pump will feed both chambers.

3,567,240 3/1971 Brassington 60/97 H 6 Claims, 4 Drawing Figures PATENTEDJAN 1 M 7 SHEEI 1 BF 2 CONTROL MEANS FOR HYDRAULIC JACK BRIEF SUMMARY OF THE INVENTION It is an object of the invention to simplify and improve the structure and operation of hydraulic forceapplying devices, particularly two-speed jacks such as those shown in my U. S. Pat. Nos. 3,134,232 and 3,581,499. The invention comprises a combination valve and seal means disposed between the high and low speed jack chambers. In the illustrated embodiment, this means is slidably mounted on the center tube and spring-urged to a closed position separating the two chambers by means of contacting valve surfaces and an annular cup-shaped seal engaging the central ram bore. The increased pressure in the high speed chamber when a load is encountered will force the valve open, so that additional pumping will feed both the high and low speed chambers.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view in elevation of the jack embodying the principles of this invention, shown in its retracted position;

FIG. 2 is a fragmentary plan view showing the hydraulic passages;

FIG. 3 is a fragmentary side elevational view, parts being sectioned, of a portion of the jack showing the pump and release valve; and

FIG. 4 is a fragmentary cross-sectional plan view taken along the line 4-4 of FIG. 3 and showing the pump valves and relief valve.

DESCRIPTION OF THE PREFERRED EMBODIMENT The jack is generally indicated at 11 and has a base 12, a cylindrical tank or outer housing 13 extending upwardly therefrom and a connection cap or tank nut 14 closing the top of the housing. A cylinder 15 is threadably secured at its bottom and top ends to base 12 and cap 14 respectively. A ram 16 has a suitably packed piston head 17 at its lower end slidably mounted in cylinder 15, the ram extending upwardly through central guiding and supporting aperture 18 in cap 14 and carrying a load-engaging member 19 at its upper end. A seal or gasket 21 carried by cap 14 seals the working chamber 22 within which ram 16 moves.

A central bore 23 is formed in ram 16, the bore being open at its lower end to a low speed pressure chamber 24 formed between piston head 17 and the bore 25 of cylinder 15 and thus being within working chamber 22. A center tube 26 is disposed within bore 23, this tube being of considerably smaller diameter than the bore and threadably mounted to base 12 at its lower end 27. The interior of tube 26 is connected to the working chamber 28 (FIG. 3) of a pump piston 29 by a passage 31 within which a check valve 32 is disposed. Chamber 28 is fed from a reservoir 33 formed between housing 13 and cylinder 15 by a passage 34 having a one-way valve 35. The arrangement is therefore such that upon the up stroke of the pump piston hydraulic fluid will be drawn from the reservoir, to be delivered to the interior of tube 26 upon the piston down stroke.

The upper end of tube 26 is connected to a quick raise or high speed chamber 36 defined by bore 23, the closed upper end 37 of this bore, and the novel valve and seal means of this invention which is generally indicated at 38. This means comprises a generally cylindrical member 39 slidably mounted on center tube 26. The upper end 41 of this member forms a valve having a surface 42 engageable with the flat undersurface or land of a retainer 43 threadably mounted on the upper end of tube 26. Surface 42 is normally urged against land 44 by a helical coil compression spring 45 disposed between the underside of member 39 and a washer 46 held in position on tube 26 by a retaining ring 47.

The lower portion 48 of the bore within member 39 has a sliding fit with tube 26 with the upper portion enlarged to form an annular passage 49 through valve surface 42. A plurality of radial passages 51 lead from passage 49 outwardly to a chamber 52 formed by the portion of bore 23 which connects with low speed chamber 24. Chamber 52 therefore in effect forms part of the low speed chamber.

The means for separating chambers 36 and 52 comprises the sealing engagement of surfaces 42 and 44 and an annular rubber-like or resilient packing ring 53 having a U-shaped cross section. The base of this ring is supported by a shoulder 54 extending outwardly from member 39 and the inner and outer lips engage member 39 and bore 23 respectively. The concave portion of this ring faces high speed chamber 36. Shoulder 54 has clearance with respect to bore 23 to permit return flow from chamber 52 past ring 53 to chamber 36 when the jack is being lowered. Packing ring 53 thus acts as a seal during the pumping cycle and a one-way valve during the release cycle.

In operation, assuming an initial position of the parts as shown in FIG. 1, upward movement of the pump piston 29 will draw hydraulic fluid from reservoir 33 through passage 34, past valve 35 and into the pump chamber 28. On its down stroke the pump piston will force the fluid past valve32, through passage 31 and tube 26 into high speed chamber 36. This will raise ram 16 in a rapid manner until the load is engaged. During this portion of the lifting cycle, spring 45 will hold valve and seal means 38 in its closed position as shown, so that no fluid will pass from chamber 36 to chamber 52. During the quick raise portion of the cycle, oil from reservoir 33 will fill the rapidly expanding low speed chamber 24 by unseating a ball check valve 55 (FIG. 2) in a cross passage 56 connecting the reservoir with chamber 24.

When load-engaging member 19 encounters a load, the pressure in chamber 36 will increase with continued action of the pump. Upon reaching a predetermined value this excess of pressure acting on packing ring 53 will cause member 39 to shift downwardly against the action of spring 45. Surfaces 42 and 44 will become separated, connecting chambers 36 and 52 through passages 49 and 51. Continued operation of the pump will therefore fill both the quick and slow raise chambers simultaneously and the jack will lift the load with increased power. A bypass 57 (FIG. 4) is provided between pump chamber 28 and a passage 58 leading to reservoir 33 to prevent overstressing.

When it is desired to lower the jack, a normally closed release valve 59 (FIG. 3) will be opened. This valve will connect a passage 61 leading from conduit 31 to reservoir 33 through a passage 62. Fluid will flow from chambers 24 and 52 past ring 53 to chamber 36 and thence through tube 26 to conduit 31 and the reservoir.

I claim:

1. In a hydraulic force applying device, a cylinder, a ram member slidable in said cylinder and defining a working chamber therewith, said ram having a pressure end defining a pressure chamber within the working chamber, a longitudinal bore extending partially through said ram member and connected at its open end to said pressure chamber, a fixed tube member disposed within and smaller than said bore, one end of said tube member being fixed and the other end opening into said bore, valve and seal means disposed between said tube and bore and separating the bore into a first chamber connected to said tube and a second chamber connected to said pressure chamber, said lastmentioned means being slidably mounted on one of said members, resilient means urging said valve and seal means to a first position separating said first and second bore chambers, the valve and seal means being responsive to a predetermined excess of pressure in said first bore chamber over that in the second bore chamber to connect said chambers, whereby fluid pumped through said tube to the first bore chamber will pass to the second bore chamber and the pressure chamber.

2. The combination according to claim 1, said valve and seal means comprising an element slidable on one of said members and having a valve surface, a valve land carried by the other member, said resilient means urging the valve surface against the valve land, an annular packing ring carried by said element and preventing passage of fluid from the first to the second bore chamber, and passageway means in said element conducting fluid between said bore chambers when the valve surface is lifted off its land by said excess pressure.

3. The combination according to claim 2, said element being slidably mounted on said tube and carrying said packing ring, said land comprising a shoulder mounted on the end of said tube, the resilient means comprising a helical coil compression spring surrounding said tube.

4. In a two speed hydraulic jack, a cylinder, a ram slidable in said cylinder and forming a working chamber therewith, a pressure end on said ram defining a low speed pressure chamber within said working chamber, a longitudinal bore in said ram open to said low speed chamber, a fixed tube extending within said bore and of smaller diameter to provide a flow passage connecting said low speed chamber with the tube, means selectively connecting the tube to a source of hydraulic liquid at pumping pressures and to a hydraulic liquid reservoir, valve and seal means in the space between said bore and tube, resilient means normally holding said valve and seal means in a position separating said flow passage into a high speed chamber connected to said tube and a second chamber connected to the low speed chamber, said valve and seal means being responsive to a predetermined excess of pressure in said high speed chamber when said ram encounters a load to shift said valve and seal means to a second position permitting fluid flow from said high speed chamber to the second bore chamber and thence to the low speed chamber.

5. The combination according to claim 4, said valve and seal means comprising an element slidable on said tube, said resilient means urging a valve surface on said element against a land carried by said tube, and a sealing ring engaging said element and bore.

6. The combination according to claim 5, said sealing ring being deflectable in response to release of pressure in said high speed chamber to permit return fluid flow from said second bore chamber to the high speed

Claims

1. In a hydraulic force applying device, a cylinder, a ram member slidable in said cylinder and defining a working chamber therewith, said ram having a pressure end defining a pressure chamber within the working chamber, a longitudinal bore extending partially through said ram member and connected at its open end to said pressure chamber, a fixed tube member disposed within and smaller than said bore, one end of said tube member being fixed and the other end opening into said bore, valve and seal means disposed between said tube and bore and separating the bore into a first chamber connected to said tube and a second chamber connected to said pressure chamber, said last-mentioned means being slidably mounted on one of said members, resilient means urging said valve and seal means to a first position separating said first and second bore chambers, the valve and seal means being responsive to a predetermined excess of pressure in said first bore chamber over that in the second bore chamber to connect said chambers, whereby fluid pumped through said tube to the first bore chamber will pass to the second bore chamber and the pressure chamber.

6. The combination according to claim 5, said sealing ring being deflectable in response to release of pressure in said high speed chamber to permit return fluid flow from said second bore chamber to the high speed chamber.