US2520426A

US2520426A - Hydraulic jack

Info

Publication number: US2520426A
Application number: US779845A
Authority: US
Inventors: Joseph J Mueller
Original assignee: Auto Specialties Manufacturing Co
Current assignee: Auto Specialties Manufacturing Co
Priority date: 1947-10-15
Filing date: 1947-10-15
Publication date: 1950-08-29
Anticipated expiration: 1967-08-29

Description

Aug- 29, 1950 J. J. MUELLER 2,520,426

HYDRAULIC JACK Filed OC. l5, 1947 Patented Aug. 29, 1950 HYDRAULIC JACK Joseph J. Mueller, St. Joseph, Mich., assignor to Auto Specialties Manufacturing Company, St. Joseph, Mich., a corporation of Michigan Application October 15, 1947, Serial No. 779,845

9 Claims.

This invention relates to hydraulic jacks or pushing and pulling devices generally, wherein an hydraulic cylinder is utilized to contain a ram and wherein the liquid under pressure is pumped into the cylinder to. force the ram outwardly to exert a pushing or lifting action.

Among the objects of the present invention is to provide a construction of the foregoing nature wherein a very simple means is provided in association with the ram, which is the piston operating within the hydraulic cylinder, wherein upon the outermost portion of the lifting or pushing stroke of the ram-like piston, a by-pass will be mechanically operated to permit the liquid under pressure within the ram cylinder to pass around the piston into the reservoir whereby to remove the pressure within the ram cylinder so that the ram piston cannot travel beyond a predetermined lifting or pushing distance, and wherein if the pumping is continued after such a distance has been travelled by the ram piston the liquid will be by-passed so as to prevent breakage.

Another object of the invention resides in providing a construction wherein a ram piston head is constructed and arranged to cooperate with the internal walls of the ram cylinder so that as the ram is being pushed along its lifting or pushing path of travel by the pressure of the liquid in the hydraulic cylinder, a leak-proof connection is formed between the piston parts, the piston, and the internal Walls of the ram cylinder, and however when the ram piston reaches a predetermined position at the end of its travel itautomatically encounters a stationary member which, contacting a part of the piston, shifts the piston with relation to the piston stem or ram, whereby to form a by-pass for the liquid in the ram cylinder to pass the liquid back to the reservoir and thus relieve any further pressure. I

Yet another object of the present invention resides in providing the lower portion of the ramlike piston with more or less loosely formed and relatively shiftable parts which are capable of shifting with respect to the stem or ram of the piston and are arranged so that under pressure of the hydraulic liquid in the cylinder for raising or pushing the ram, a tight connection is effected which maintains the pressure in the ram cylinder and yet when the ram reaches its outermost stroke the relatively shiftable parts of the piston will contact an abutment, thereby shifting the parts and causing a by-pass passageway to be formed between said parts and the ram or piston stem to permit the liquid in the ram cylinder to by-pass therethrough into the reservoir.

Yet another object of the invention resides in providing a ram having a lower portion formed with stepped cylindrical portions upon which loosely t a three-part piston for the ram head comprising a metallic ring, a packing disk, and an outermost ring of relatively hard non-metallic material which clamps the packing ring between the two relatively harder rings and wherein these three elements make a loose fit with respect to the stepped portions of the ram itself and in association with the ram form a by-pass so that when the ram piston reaches the uppermost portion of its travel it will contact an abutment whereby to shift these relatively loosely fitting annular members with respect to the ram itself to form a by-pass passage to permit the liquid under pressure in the ram cylinder to pass the piston and escape to the reservoir whereby to relieve the pressure.

Another object of the invention is to provide a pressure relief device for an hydraulic jack wherein the relief device is formed by slidably mounting the ram piston on the ram in a manner to provide a rather loose t between the inner walls of the piston and the external walls of that portion of the ram on which the piston is mounted, the loose fit forming a liquid relief passage which is normally closed on the working stroke of the ram by intercontacting surfaces between the inner walls of the piston and the external walls of the ram embraced by the piston, and in providing means at the outer portion of the working stroke of the piston for shifting the piston relatively to the ram so as to cause said relief passage to open and permit the liquid to pass from the Working sideof the ram to the relief side of the ram, and which relief side of the ram is always in communication with the reservoir.

Yet another object of the invention resides in providing a pressure relief mechanism for an hydraulic jack which eliminates cup washer scoring in devices which relieves the ram cylinder of excessive pressure at the outermost working stroke of the ram in the ram cylinder, and this is accomplished by providing a ram piston which is shiftable bodily relatively to the ram and automatically provides a liquid relief passage between the connection of the piston and the ram.

These and other objects of the invention will be apparent from a perusal of the following specication lwhen taken in connection with the accompanying drawing, wherein:

Figure 1 is a sectional view of one type of jack to which the invention is applied;

Figure 2 is an enlarged view of a portion of Figure 1, taken on the line 2--12 of Figure 1, showing the ram moving upwardly with the piston ram parts arranged to hold the pressure within the ram cylinder;

Figure 3 is a section following Figure 2 but showing the ram piston at the upper end of its travel with the piston parts shifted to provide a liquid passage therethrough to the reservoir; and

Figure 4 is a section taken on the line 4-4 of Figure 2.

Referring now to the drawing in detail, it will be understood that the exemplification of the invention herein is disclosed and illustrated as applying to any type of hydraulic pushing and pulling device involving a ram cylinder and a ram operated hydraulically, and wherein the ram moves within the cylinder over a predetermined length of travel and wherein means is provided at the en-d of the travel for effecting relief of the pressure in the ram cylinder, through the ram y reservoir I therewithin; The base 2 is threaded about the well 4 as at I2 to receive the lower threaded walls of a ram cylinder I4. Also, the base is provided with the downwardly extending passage I6 and the diagonally disposed counterbore I8. The passage I6 is closed by the plug and the usual type of high pressure pump cylinder 22 is disposed in the bore I8. Within the pump cylinder 22 lthere operates a piston 24 operated by means of an actuator 26 pivoted to the side wall 8 as at 28.

Any type of release valve, not herein shown, may be utilized for relieving the pressure from the ram cylinder 4 into the reservoir I0. In addition to thelpassageway I6 I likewise provide another passageway 30 whichconnects a port in the side wall of the pump cylinder I8 with the reservoir I0. It is to be understood that in accordance with the usual custom an additional reservoir, not shown, and a controlling, manually actuated valve for the same, is provided in the base for connecting the ram cylinder 4 with the reservoir II) in a manner independently of the passageways 30 and I6. It is'also to be understood that the bottom of the pump cylinder I8 connects as by means of an additional passageway 32 with the passage I6 connecting with the ram lcylinder 4.

The outer ends of the cylinders 8 and I4 are closed by means of a, head 36 having downwardly extending portion 38 suitably threaded as at 39 to engage the outer threads of the ram cylinder I4, and this ring-like head 36 is provided with a shouldered portion 4u which engages the outer ends of the cylinder 8 and clamps tightly thereagainst when the threads 39 are drawn up tightly. In addition, the head'36 is provided with an inwardly extending ange 42 through which a ram piston or stem 44 passes. A packing 46 held in position by an externally threaded ring '48 holds the packing in place about the ram stem 44. It is noted that the diameter of the ram stem 44 is considerably less than the internal diameter of the ram cylinder I4. At the upper end of the ram cylinder a chamber 50 is provided, and this chamber communicates by means of an elongated passage 52 which terminates as at 53 in open communication with the reservoir I0 so that there is a constantly open passage at the upper end of the ram cylinder via the chamber 50, the passage 52, and the port 53.

The stem 44 is formed on its lowermost end with an internal bore 54 which is of considerable 5 diameter and is likewise formed with a, rst annular wall 56 of smaller diameter than the outer diameter of the stem 44, thereby forming a shoulder 58. In addition, below the wall 56 which runs parallel with the outer cylindrical wall 60 of the ram 44, the lower portion of the ram is provided with a parallel wall such as 62 which is of even smaller diameter than the wall portion 56, thereby creating a second shoulder 64 which is disposed below the shoulder 58. The lower end of the ram 44 is rolled over to provide a, retaining shoulder 66 which serves to retain or hold the piston proper thereon. In addition, the lower end of the ram, just above the shoulder 66, is provided with a port 68, as seen best in Figures 2 and 3. The piston is preferably formed of three parts, a metallic ring 10, and a hard rubber ring or ring of other relatively hard material 12, which has an annular cutout on its under side of substantially V-shaped form, as shown at 14. The inner wall of this ring ares inwardly as at 16 so that at its top portion of the ring 12 is of lesser cross section than at its bottom, and this taper is so arranged in magnitude that when in the position shown in AFigure 3 there is a passageway 18 formed between the inner wall of this washer 12 and the o-uter reduced wall 62 of the lower portion of the ram stem. The lower portion of the relatively hard annulus 12, as shown in Figure 3, is adapted to contact and abut the rolled over flange 66 of the ram stem 44.

Disposed between the two relatively

hard annuli

10 and 12 is a relatively soft packing 80 which may be of any semi-resilient or yieldable material which will not deteriorate and will hold its form. It may be of leather or any usual or desirable material. The inner wall of this ring is of substantially the same diameter as the upper portion of the inner wall 16 of the lower annulus 12 so that it forms a continuation of the passage 18 hereinbeforey described.

The combined dimension from top to bottom of the upper annulus 10, the washer 80, and the lower annulus 12, is less than the distance between the shoulder 58 and the top edge of the rolled abutment or flange 66, so that the three

annuli

10, 80 and 16 may have a shifting movement between the shoulder 58 and the shoulder 66. It is to be noted that the upper wall 82 of the annulus 10 projects beyond the outer wall ,55 of the ram 44 but lies within the projection of the flanges 42 on the head 36 so that when the ram 44 has moved upwardly to the position shown in Figure 3, the upper surface 82 of the annulus 1D will strike the lower surface of the 60 portion 42 of the head 36 so that on still further outward movement of the ram the annulus 10,

the packing 80 and the lower annulus 12 will be shifted downwardly to the position shown in Figure 3v thereby permitting liquid to flow from the ram cylinder 4 from a 4continuation of the well through the port 68, thence via the passage 18, this passage being formed between the inner wall of the annulus 12, the inner wall of the packing and the inner wall -of the upper anmoving upwardly under the pressure within the ram cylinder, the pressure in the ram cylinder will `force the

annuli

10, 80 and I2 upwardly against the shoulder 58 and likewise against the shoulder 64, thereby blocking off the liquid passage 'I8 to prevent the escape of the liquid to the chamber above the piston so that the piston in this position will remain a liquid seal not only with the ram stem 44 but also with the internal walls of the ram cylinder I4 and it is only when the upward travel has been reached that the upper annulus 'l0 strikes the shoulder 42 and the annuli are shifted downward to form a fluid connection with the chamber 50 and channel 52 to cause liquid to pass therethrough to the reservoir I0, thereby relieving further pressure in the raml cylinder and preventing breakage in the parts.v It will be noted from the foregoing that by,

reason of this loose connection or loose flt between the annuli on the lower end of the ramA stem, the formation of the port therein andthe disposition of the upper channel 50, the passage- 52, and the port 53 back to the reservoir, I have' provided a very simple, inexpensive means for relieving the pressure in the ram cylinder at the outermost portion of the lifting or pushing stroke,

and which construction at the same time provides -a liquid seal of the piston against the ram stfnf'i and the inner walls of the ram cylinder. By means of this construction I eliminate the heretofore present scoring of the walls of relief valves by the passage of liquid therethrough under the heavy pressure of the liquid in the ram cylinder as it by-passes the ram and is passed into the reservoir. Underthe present construction I have eliminated the necessity of expensive shiftable valves, ball valves, springs, and other constructions which generally include a scoring of the valve parts under the terrific strain of the liquid in the ram cylinder escaping, and provide a simple type of mechanism for relieving pumping pressure when the ram has reached its outermost position. By means of the construction I have provided a loose fit between the ram piston and the ram stem by means of the shouldered construction of the ram stem on its lower end and have utilized the loose t to provide shiftable parts of the piston providing a liquid passageway to pass the escaping liquid from the ram cylinder therethrough at the proper time and in aA manner to prevent the scoring ofi. .f

the walls which would otherwise tend to increase the size of the passage and ultimately prevent correct passage, while at the same time there has been assured a complete sealing of the liquid under proper working conditions.

It is apparent that many widely Vdifferent embodiments of this invention may be made without departing from the spirit and scope thereof, and therefore it is not intended to be limited except as indicated in the appended claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:

l. In combination, a base, a ram cylinder formed on the base and a reservoir associated with the base and the ram cylinder, a ram operable in the cylinder and having a portion of smaller diameter than the cylinder, pump means for drawing liquid from the reservoir and for forcing liquid into the ram cylinder, the lower portion of the ram being of reduced diameter and a piston shiftably mounted on said portion of the ram reduced diameter, said piston being of an external diameter snugly fitting the interior wall of the ram cylinder, means including the internal walls of said piston in association with the external reduced surface of the ram providing a pressure release passage connecting portions of the ram cylinder on opposite sides of the piston, and means disposed in the path of travel of the piston as it approaches its extreme limit of outward travel for shifting the piston on the ram to open said release passage to allow the liquid in one end of the cylinder to flow therethrough to the opposite end of the cylinder, and a normally open passageway connecting the opposite side of the ram cylinder with the reservoir.

2. An hydraulic jack comprising a base having a ram cylinder and a reservoir, a ram in the ram cylinder, said ram being of less diameter than the ram cylinder, said ram having its lower end formed of decreased diameter, a piston mounted on said ram portion of decreased diameter and capable of shifting movement therealong in the direction of the longitudinal axis of the ram, the external wall of said piston forming a liquid-tight t with the inner wall of the ram cylinder, and means associated with the internal walls of the ram piston and the outer wall of the ram stem along Whichthe ram piston ismovable forming a liquid by-pass passage through the ram piston, means at the upper end of the ram cylinder forming an unobstructed liquid passage therefrom to the reservoir, said piston when subjected to the pressure of the ram cylinder in the raising of the load forming a liquid seal with the walls of the ram stem which are of reduced diameter, and said piston having means thereon causing the same to be shifted longitudinally of the ram stem when said piston reaches the outermost portion of its working stroke whereby the piston is shifted longitudinally of the ram stem to form a passageway between the inner walls of the piston and the reduced portion of the ram stem which it surrounds to permit the liquid to pass therethrough and into the reservoir.

3. An hydraulic jack comprising a base, a ram cylinder thereon and a reservoir thereon, means for creating hydraulic pressure in the ram cylinder, a ram in the ram cylinder, said ram including a piston operable by the pressure in the ram cylinder to raise the ram, said ram being of lesser diameter than the internal walls of the ram cylinder, the lower portion of the ram being of reduced diameter and providing shoulders thereon, a piston mounted on said portion of reduced diameter of the ram, the internal walls of the piston being of lesser diameter than the external walls of the reduced diameter of the ram whereby to provide a liquid by-pass between the internal walls of the piston and the external walls of reduced diameter of the ram, said piston being shiftable along the ram portion of reduced diameter in a direction longitudinally of the longitudinal axis of the ram, and said piston and portion of reduced diameter of the ram and said shoulders formed in said portion of reduced diameter being operable under the pressure in the ram cylinder to shift said piston against said shoulders to close said by-pass passageway to prevent passage of liquid therethrough, and means disposed at the outer end of the ram cylinder adapted to contact said piston to shift it longitudinally of the ram portion of reduced diameter to open said by-pass passageway to permit the passage of liquid therethrough to relieve the pressure in the ram cylinder.

4. An hydraulic jack comprising a base, a ram cylinder thereon and a reservoir, a ram in the ram cylinder of less diameter than the internal walls of the ram cylinder, the lower end of the ram having a wall of reduced diameter to provide an upper shoulder disposed normally to the longitudinal axis of the ram and having a second portion of greater reduced diameter than the first mentioned portion to provide an intervening shoulder extending normally to the longitudinal axis of the ram, the outer end of the lower portion of the ram being provided with a retaining shoulder and an annular piston disposed about that portion of the ram of reduced diameter between the upper shoulder and the retaining shoulder, the length of the piston between said shoulders being less than the distance apart of said shoulders, the internal walls of said piston being of greater diameter than the external walls of the portion of reduced diameter of the ram whereby to provide a liquid by-pass passage through the piston, means at the upper end of the ram cylinder forming a liquid passage therefrom to the reservoir, and means disposed in the path of travel of the ram piston as it reaches its outermost limit of travel along the ram cylinder adapted to contact said piston to shift the same relatively to the ram on which it is mounted for opening said by-pass passage to permit liquid under pressure in the ram cylinder to pass to the end of the ram cylinder and through said liquid passage and into the reservoir.

5. A device as set forth in claim 4 wherein the piston is composed of three parts, an upper metallic annulus, a lower annulus of hard material, and an intermediate packing annulus or washer, the upper surface of the metallic annulus being adapted to contact the rst shoulder and the upper surface of the packing annulus being adapted to contact the second shoulder, and the lower inner wall of the third annulus being adapted to contact the retaining shoulder in the alternate movements of the piston relatively to the ram, and the outer walls of at least one of said annuli making a liquid-tight seal with the inner walls of the ram cylinder.

6. In combination, a base, a ram cylinder and a reservoir, a ram in the ram cylinder, said ram having a reduced diameter compared with the, diameter of the internal walls of the ram cylinder, a piston on the lower end of the ram, the outer walls of the piston making a liquid-tight seal with the internal walls of the ram cylinder, the internal walls of the piston and the external walls of the lower part of the ram being formed to provide a loose fit therebetween to provide a, liquid by-pass passage therebetween, said piston being shiftable along the lower end of the ram in a direction parallel to the longitudinal axis of the ram, and said lower portion of the ram providing shouldered means in one position to engage the piston to form a liquid-tight seal therewith to close the liquid passage between the inner walls of the piston and the reduced portion of the ram, means forming a liquid connection between the upper end of the cylinder and the reservoir, means disposed in the path of travel of the piston at the outer portion of the path of travel of the ram in the ram cylinder for contacting the piston to shift it longitudinally whereby to open the passage formed between the internal walls of the piston and the external walls of the lower portion of the ram to permit liquid under pressure in the ram cylinder to pass therethrough and escape to said passages and into the reservoir.

7. In an hydraulic device, the combination of a ram cylinder and a ram shiftable therealong under liquid pressure in the ram cylinder, the ram having a piston shiftably mounted thereon and forming a loose fit therewith toprovide in one position a liquid by-passage between the ram and the piston and in another position and under the pressure of the liquid in the ram cylinder to press the piston against a portion of the ram to block said passage, and means disposed at the outermost path of travel of the ram in the ram cylinder for shifting the piston relatively to the ram to open said passage to permit the passage of liquid through the piston.

8. An hydraulic jack comprising a base and a ram cylinder, a ram in the cylinder of less diameter than the internal diameter of the cylinder, a piston slidably mounted on said ram and having external walls snugly fitting the cylinder, the internal Walls of the piston being of larger diameter than that portion of the external walls of the ram which are surrounded by the piston to form a liquid relief passage, and said external walls of the ram having portions engageable by said piston to close said passage, said piston when subjected to working pressure in the ram cylinder being shiftable to a position along said ram so as to close said relief passage, and means operated by said movement of the piston as it arrives substantially at the end of the working stroke of the ram for shifting the piston along the ram for opening the relief passage between the internal walls of the piston and the walls of the ram embraced thereby.

9. In combination with a, ram cylinder, a ram in the cylinder, liquid sealing means disposed on the ram and slidably and continuously engaging the inner wall of the ram cylinder and forming a liquid-tight seal with the inner wall of the cylinder, said sealing means being shiitably mounted on said ram and under pressure created by the pressure in one end of the ram cylinder being operable for sealing against said ram, said sealing means cooperating with said ram to form a liquid passage operable when said passage is not sealed to pass liquid under pressure through said passage only when the ram approaches one end of the cylinder, and means operableI in the path of said sealing means as said ram approaches its extreme movement in one direction with respect to the cylinder and operable on said sealing means for shifting said sealing means relatively to the ram to open said liquid passage for relieving the pressure in said working pressure end of said cylinder.

JOSEPH J. MUELLER.

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

UNITED STATES PATENTS Number Name Date 1,707,497 Shevlin Apr. 2, 1929 2,136,835 Begg NOV. 15, 1938 2,322,314 Pomeroy June 22, 1943 2,352,920 Stevens July 4, 1944 2,438,317 Gabriel Mar. 23, 1948