US2458744A - Hydraulic jack - Google Patents

Description

I Janjll, 1949. F. H. SCHWERIN 2,458,744

HYDRAULI C JACK Filed May 22, 1947 2 sheets-Sheet 1 er @ms F. H. SCHWERIN HYDRAULIC JACK Jan. l1, 1949.

2 Sheets-Sheet 2 Filed May 22, 1947 lq @Mw Maikel/Ms Patented Jan. 11, 1949 HYDRAULIC JACK Frank H. Schwerin, Pittsburgh, Pa., assignor to The Duff-Norton Manufacturing Company, Pittsburgh, Pa., a corporation of Pennsylvania Application May 22, 1947, Serial No. 749,680

6 Claims.

This invention relates to hydraulic jacks.

It is among the objects of this invention to provide a hydraulic jack which is as light as possible for the load it must be capable of lifting, which does not become air or Vacuum bound when its reservoir is lled with liquid, which has an air vent that is opened and closed automatically as the jack is raised or lowered, and which will no-t loose its liquid through the air vent if laid `on its side when the jack is lowered.

In accord-ance with this invention, a reservoir for a liquid surrounds a jack -cylinder mounted on a base. The top of the reservoir is closed. A hollow lifting member is vertically movable in the cylinder, and includes a closed top and a piston on its lower end. The cylinder is spaced from the lifting member above the piston, whereby a variable volume chamber is formed between them. A pump is provided for pumping liquid from the reservoir into `the bottom of the jack cylinder to raise the lifting member therein. The jack -is provided with an air passage connecting the upper end of the reservoir with the variable volume chamber, and the lower portion of the lifting member above the piston is provided with an air passage connecting the same chamber with the inside of the lifting member. Finally, the upper portion of the hollow lifting member is provided with an air passage that connects the inside of the member w-ith the atmosphere only when the lifting member is raised in the cylinder. The three passages just mentioned therefore will vent the reservoir to the atmosphere. The inner end of the upper air passage preferably is located at about the axis of the lifting member, while the -outer end of the same passage is located just below the packing through which the lifting member slides, when the lifting member .is in "its lowermost posi-tion.

The preferred embodiment of the invention is illustrated in the accompanying drawings in which Fig. 1 is a plan view of the jack; Fig. 2 is a vertical section taken on the line II-II of Fig. 1; and Fig. 3 is a fragmentary cross section taken on the line IIE-III of Fig. 2.

Referring to the drawings, a rectangular block of metal that serves as the base I of the jack is provided with a pair of laterally spaced threaded recesses that open upwardly. Screwed into the larger of these recesses is the lower end of a vertical jack cylinder 2. Encircling the jack cylinder, but spaced from it, is a circular groove 3 in base I in which the lower end of a cylindrical reservoir -II -is mounted. This reservoir is retained lin position Iand pressed tightly against the base by means of 4a capping nut screwed on the upper end of the jack cylinder and having an outer lower corner of reduced diameter in which the upper end of the reservoir is received. The inner diameter of the nut is greater than the inner diameter of the cylinder. Oil may be introduced into the annular space between the reservoir and cylinder through a port in the capping nut. As shown in Fig. l, this port normally is closed by va screw plug l.

Movable vertically in the jack cylinder is a plunger-like lifting member or ram having e. hollow body 8 closed at its lower end by a plug 9 on which is mounted a piston that includes a packing cup I Il engaging the cylinder so that fluid pressure below the piston can raise the lifting member. The hollow body of the lifting member is spaced from the cylinder wall, thereby forming between them a chamber I2 of any desired width and which decreases in volume as the piston rises. The upper end of the hollow body is closed by a heavy cap I3 having the same diameter as the body.

Resting on top of the jack cylinder, but having a smaller diameter, is a metal ring Ill. A pair of packing rings I6 and I'I are pressed against the metal ring by means of a threaded ring I 8 encircling cap I3 and screwed into capping nut B. These packing rings engage the lifting member and seal the upper end of chamber I2. By removing from inside the capping nut the four rings just mentioned, the lifting member can be lifted from the jack cylinder for inspection or repair Without disturbing the capping nut and `the other elements eng-aging it. The upper end of the reservoir is connected by inclined passages i9 vthrough the capping nut with the annular space 'between the nut and the top lof the jack cylinder, and that space is connected through notches 2t in the top of the jack cylinder with the upper end of chamber I2. Near its upper end the Cylinder is provided with relief orices 2l that are so positioned as to permit liquid below the rising piston to iiow through them back into Ithe reservoir before the top of the piston can jam against metal ring I4.

Screwed into the other recess 'in the base is the lower end of a pump cylinder 22 in the upper end of which there is a packing recess containing a packing member 23 and a packing nut 24. Vertically reciprocable in the pump cylinder is a plunger 2-6, the upper end of which projects above the packing nut and into a slot 21 in the lower part of a socket member 28 where it is pivotally retained by a pin 29. As shown in Fig.

1, one end of this member is pivotally connected to the upper end of a link 3|, the lower end of which is pivotally mounted in a recess 32 in the base l. The opposite end of the socket member is provided with a socket 33 for receiving a hand lever' (not shown) by which the socket member may be swung up and down in order to reciprocate the plunger in the pump cylinder.

The .pump is connected with the reservoirl and jack cylinder in conventional manner. Thus, the end of base l adjacent the pump is provided with a threaded socket into which a sealingplug E46 is screwed. The plug is spaced from the cylinder E is a passage 38 the innerv end of which opens into a hole 39 drilled into the base below the lifting member. base from the inner wall of the socket is a passage 4l parallel to passage 38. The inner end of passagell opens into the bottom of a hole42 drilled down into the base from the bottom of the uid reservoir. The reservoir thus-s connected by this hole, passage lli, socket chamber 3l, passage 38, and hole with the bottom of the jack cylinder. rIhe bottom of'pump cylinder 22 is connected by a vertical passage 43 in the base with an enlarged central portion of passagefdl. This enlarged portion is provided on opposite sides of the vertical passage with check valve seats againstwhich an inlet ball d5 and an outlet ball it normally rest. rlhe inlet ball is prevented from closing the vertical passage byv any suitable means, such as by a coil spring lll engaging it and the other ball. toward its seat by means of a light coil springv 48 compressed between it and plug 36.

With this arrangement, when the pump is operated, liquid from the reservoir is drawn past the v inlet ball and up through passage 43 into the,V` pump cylinder, and then the liquid is forced Aback y down through the same passage, past the uout-letV ball, and through socket chamber 31 to passage.

t8 through which it is conducted to the jack cylinder to elevate the lifting member therein. Re-

verseiiow of liquid in passage lll is prevented lbyl the checkv valve balls.

In order to release the liquid fromthe jackcylinderwhen the lifting member is to be lowered, a by-pass opening 5]-- (Fig. l) is drilled in the base for connecting the lower end of hole 42 with passage 38. This by-pass normally is maintained closed by a manually operable valve- 5l -havingvoir is automaticallyvented to the atmospherev as soon as the llifting member has begun to rise in the cylinder, whereby the jack will not become air or vacuum bound. Accordingly, the plug 9 at the-lower end of the lifting member is provided above the piston with an inclined passagel 55 connecting the inside of hollow body 3 with the chamber l2 around it. The upper end of the hollow body is connected by an air vent with the atmosphere, after the lifting member has been raised a short distance. Preferably, this air vent is formed by drilling a-hole d@ a short distance up into the centerof cap i3, and drillingra passage 5l radially throughy the upper end ofthehollow bodyv and the capv into; the hole just-mentioned The outer end-of thevent is spaced .lust fan; enough` from the top ofy thecap-tojlocate'itbelowf Also drilled inwardly ofthe- The outlet ball is urged 4 packing rings i6 and Il when the lifting member is in its lower position.

Consequently, when the jack is down or closed, it is impossible for the liquid in it to leak out through the vent even though the jack is lying on its side. As soon as the lifting member rises far enough for the outer end of the vent to communicatewith the atmosphere above the packing rings, the reserfvoiriis automatically connected with the atmosphere through passage i9, chainber I2, passage 55, hollow body 8, and vent passages 5,6and 5l. This prevents the lifting member from becoming air or vacuum bound as it rises ordescends `in the jack cylinder. Yet, an oversize reservoir is not necessary, because an air chamber does not have to be left above it. My system of ventingthe reservoir being automatic, there is no valve to be opened and closed, o1' to be accidentally knocked off the jack or otherwise damaged. Even if the jack falls on its side when the lifting memberis-up, there is little chance of any liquid leaking out through the exposed vent, because the vacuum that it would tend to create in thefreservoir would restrain it. It some liquid ran into the reclining hollow body 3, there would be little likelihood of it rising high enough to enter the entrance 56 of the vent.

According to the provisions of the patent statutes, I have explained the principle and construction of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced .otherwise than as specifically illustrated and described.

I claim:

l; A hydraulic jack comprising a base, a jack cylinder mounted thereon, a liquid mounted on the base around the cylinder and having a closeditop, a hollow lifting member verticallymovable in the cylinder and including a closed top and a piston on its lower-end, the cylinder'being spaced from said member above the piston to form a variable volume chamber, and a pump for pumping liquid from the reservoir into the bottom of the cylinder to raise the lifting member therein, the jack being provided with anair passage connecting the upper end oi the reservoir with saidv chamber, the lower portion of the lifting member above the piston being provided with an-air passage connecting the inside of said member with said chamber, and the upper portion of the lifting member being provided with `a vent-passage connecting the inside of said meinber withV the 4atmosphere when the lifting memberis raisedl in the cylinder, whereby said passages and' chamber will connect the reservoir with the atmosphere.

2. A hydraulic jack comprising a base, a jack cylinder mounted thereon, a liquid reservoir mounted on'the base around the cylinder and having a closed top, a hollow lifting member vertically vmovable in the cylinder and including a closed top and a piston on its lower end, the cylinder being spaced from said member above the piston to form a variable volume chamber, and a pump for pumping liquid from the reservoir into the bottom of the cylinder to raise the lifting member therein, the jack being provided with an air passage connecting the upper end of the reservory with said chamber, the lower portion of the lifting member above the piston being provided` with anair-passage connecting the inside :of sa-idinembenwith said chamber, and the upper reservoir f portion of the lifting member being provided with a vent passage extending from the inside of said member laterally to the atmosphere when the lifting member is raised in the cylinder, whereby said passages and chamber will connect the reservoir with the atmosphere.

3. A hydraulic jack comprising a base, a jack cylinder mounted thereon, a liquid reservoir mounted on the base around the cylinder and having a closed top, a hollow lifting member vertically movable in the cylinder and including a closed top and a piston on its lower end, the cylinder being spaced from said member above the piston to form a variable volume chamber, and a pump for pumping liquid from the reservoir into the bottom of th-e cylinder to raise the lifting member therein, the jack being provided with an air passage connecting theupper end of the reservoir with said chamber, the lower portion of the lifting member above the piston being provided with an air passage connecting the inside of said member with said chamber, and the upper end of the lifting member being provided with a vent passage extending axially up into it and then laterally to the outside of said member, the outer end of said vent passage being exposed to the atmosphere only when the lifting member is raised in the cylinder, whereby said passages and chamber will connect the reservoir with the atmosphere.

4. A hydraulic jack comprising a base, a jack cylinder mounted thereon, a liquid reservoir mounted on the base around the cylinder and having a closed top, a hollow lifting member vertically movable in the cylinder and ncluding a closed top and a piston on its lower end, the cylinder being spaced from said member above the piston to form a variable Volume chamber, a packing surrounding the lifting member above said chamber, and a pump for pumping liquid from the reservoir into th-e bottom of the cylinder to raise the lifting member therein, the jack being provided with an air passage connecting the upper end of the reservoir with said chamber, the lower portion of the lifting member above the piston being provided with an air passage connecting the inside of said member with said chamber, and the upper portion of the lifting member being provided with a vent passage extending from inside of said member to its outside, the outer end of said vent passage being located below said packing when the lifting member is in its lowered position and being exposed to the atmosphere when said member is raised in the cylinder, whereby said passages and chamber will connect the reservoir with the atmosphere.

5. A hydraulic jack comprising a base, a jack cylinder Amounted thereon, a liquid reservoir mounted on the base around the cylinder and having a closed top, a hollow lifting member vertically movable in the cylinder and including a closed top and a piston on its lower end, the cylinder being spaced from said member above the piston to form avariable volume chamber,

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a packing surrounding the lifting member above said chamber, and a pump for pumping liquid from the reservoir into the bottom of the cylinder to raise the lifting member therein, the jack being provided with an air passage connecting the upper end of the reservoir with said chamber, the lower portion of the lifting member above the piston being provided with an air passage connecting the inside of said member with said chamber, and the upper portion of the lifting member being provided with a vent passage extending up into it near its center and then laterally to the outside of said member below said packing when said lifting member is in its lowered position, the outer end of said vent passage being raised above said packing and exposed to the atmosphere when the lifting member is elevated in the cylinder, whereby said passages and chamber will connect the reservoir with the atmosphere.

6. A hydraulic jack comprising a base, a jack cylinder mounted thereon, a liquid reservoir mounted on the base around the cylinder, a nut screwed on the upper end of said cylinder and closing the space between it and the upper end of the reservoir, a hollow lifting member vertically movable in the cylinder and nut and including a closed top and a piston on its lower end projecting radially into contact with said cylinder, whereby a variable volume chamber is formed between said member and cylinder above the piston, the inner diameter of the nut being greater than the diameter of the piston, a packing ring engaging the lifting member above the i cylinder, a threaded ring screwed into said nut to hold down the packing ring, and a pump for pumping liquid from the reservoir into the bottom of the cylinder to raise the lifting member therein, said nut being provided with an air passage connecting the upper ends of said reservoir and chamber, the lower portion of the lifting member above the piston being provided with an air passage connecting the inside of said member with said chamber, and the upper portion of the lifting member being provided with a vent'l passage extending from inside of said member to its outside, the outer end of said vent passage being located below said packing when the lifting member is in its lowered position and being exposed to the atmosphere when said member is raised in the cylinder, whereby said passages and chamber will connect the reservoir with the atmosphere.

FRANK H. SCHWERIN.

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

UNITED STATES PATENTS

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