US2786453A

US2786453A - Hydraulic jack

Info

Publication number: US2786453A
Application number: US392570A
Authority: US
Inventors: William S Pine
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-11-17
Filing date: 1953-11-17
Publication date: 1957-03-26
Anticipated expiration: 1974-03-26

Description

7 March 26, 1957 Filed NOV. 17', 1953 W. S. PINE HYDRAULIC JACK 2 Sheets-Sheet l INVENTOR: W/LL /A M 5.- Pm E March 26, 1957 w. s. PINE HYDRAULIC JACK 2 Sheets-Sheet 2 Filed Nov. 17, 1953 INVENTOR: W/LUAM 6. PM:

United States Patent HYDRAULIC JACK William S. Pine, Sunland, Calif.

Application November 17, 1953, Serial No. 392,570

2 Claims. (Cl. 121-46) This invention relates generally to lifting devices and particularly to a hydraulic jack for moving an object. Specifically, the invention is concerned with improvements in a hydraulic jack of the general type disclosed in my United States Patent No. 2,654,568, granted October 6, 1953, for Hydraulic Jack.

My prior patent referred to above discloses a jack having a base provided with a vertical post and a lifting tube or ram slidable on the post and having an upper closed end, the post having a vertical passage communicating with the interior of the ram. Pump means are provided for forcing pressure fluid through the passage into the ram to raise the same. According to the patented structure, the ram is provided with a laterally projecting t-oe adapted to engage under an object to be lifted and in order to compensate for lateral stresses imposed upon the ram during the lifting of the object by means of the oifset toe, a roller is provided adjacent the lower end of the ram, said roller engaging and being rollable along a flat, vertical surface of the post.

While such a jack is now used widely for industrial purposes and is regarded as highly eflicient for such use, it has been found that failure of operators to follow directions for operating the device has frequently resulted in damage to the jack. To be more specific, the post has an enlarged piston-like head at its upper end and in the event that the ram is forced upwardly beyond a recommended height the roller is caused to strike against this head to cause damage to the head or to the roller, or both.

It is therefore an important object of the present invention to obviate this disadvantage by providing stop means operative to limit the upward movement of the cylindrical ram to a height which will preclude engagement of the roller means with the piston-like head so as to avoid damage to the parts.

Another object of the invention is to provide a hydraulic jack, of the character referred to, in which the stop means consists of a valve device so constructed and arranged as to function automatically, in response to upward movement of the ram to a predetermined height, to prevent further introduction of hydraulic fluid into the ram, such closing of the fluid passage occurring immediately prior to engagement of the roller means against the upper head of the post.

Another object of the invention is to provide a hydraulic jack of the type indicated in which the valve-type stop means includes an annular, sleeve-like, seat element screwed into the upper end of the fluid passage, and a plunger having an upper end portion of fluted cross section, said flutes forming ducts through which the fluid normally flows from the passage into the ram, the stop means further including a circumferential flange or valve element which, when the ram has moved through its predetermined, safe, upward stroke, moves into sealing engagement with the lower end of the seat element to shut ofi the flow of fluid.

Another object of the invention is to provide a hydraulic jack of the class specified in which the stop means I, 2,786,453 Patented Mar. 26, 1957 includes a spring pocketed in the fluid passage of the post and surrounding the lower end of the plunger with its upper end engaging the flange thereof, the spring thus functioning to normally maintain the upper, projecting end of the plunger against the upper end wall of the ram. By this provision, 'the plunger is caused to slide upward- 1y with the ram to cause the valve element to move progressively toward the seat element and to engage the same upon movement of the ram through its predetermined operative stroke.

Another object of the invention is to provide in a hydraulic valve, of the type referred to, sealing means for sealing the seat element against leakage of fluid.

A further object of the invention is to provide a strokelimiting means which is extremely simple in construction and economical to produce, one which is highly efficient and fool-proof in action, and one which may be readily applied to existing, as well as to new jacks during the manufacture thereof.

Further objects will appear from the following description and from the drawings, which are intended for the purpose of illustration only, and in which:

Fig. l is a side elevational view of the improved hydraulic jack, one of the pumps being shown in section;

Fig. 2 is a vertical sectional view through the jack;

Fig. 3 is a fragmentary, vertical sectional view, showing the stop-valve open to allow flow of the hydraulic fluid into the hollow ram to raise the same;

Fig. 4 is a view similar to Fig. 3, showing the stop valve closed to shut off the flow of the fluid into the ram; and

Fig. 5 is a cross-sectional view, taken on line 5-5 of Fig. 2.

Referring to the drawings in detail, the improved hydraulic jack is of the general type disclosed in my patent referred to above, the jack having a base 10 adapted to rest upon a surface, 'the base having a slot 11 at one side. Formed integrally with the base 10 is a vertical post 12 which has an axial bore or fluid passage 13. At its side adjacent the slot 11, the post is provided with a flat, vertical surface 14. Projecting upwardly from the base 10 is a cylindrical reservoir 15 for containing a supply of hydraulic fluid F, the reservoir having a filler opening, closed by a filler plug 16.

One or more pump means 29 are provided on the base iii, each pump including an upstanding link 21 pivoted at 22 and an actuating lever 23 pivotally connected to the upper end of the link 21 and to the upper end of a reciprocable plunger or piston 24. The plunger 24 is slidable in a bearing 25 which, in turn, is connectedto a valve housing 26 having passages 27 and 28 which communicate with

passages

29 and 30 which, in turn, communicate respectively with the interior of the reservoir 15 and the bottom of the flow passage 13. Incorporated in the

valve passages

29 and 30 are ball valves 31 and 32. When the piston 24 is moved upwardly, it unseats the ball 31 and draws hydraulic fluid fromthe reservoir through the line 29. During downward movement of the piston 24, the ball 31 is seated and the ball 32 is unseated to cause the fluid to be forced through the line 30 into the lower end of the post 12.

Carried by the post 12 at its upper reduced end 34 is a stationary piston head 35 having sealing rings 36. Surrounding the head 35 is a tubular ram 38 having an upper closed end 39. A sealing element 40 carried by the reduced end 34 to further seal the clearance space between the head 35 and the inner surface of the ram 38. At its lower end, the ram 38 is provided with a laterally projecting toe 42 adapted to underlie an object to be lifted. Disposed inwardly of the toe 42 is a recess 43 across which extends a pin 44, a roller 45 being rotatable .on this pin and adapted to roll along the flat surface 14 as the ram moves upwardly and downwardly on the post 12.

As willbe apparent, when hydraulic fluid is forced upwardly through the passage 13 and impinges against the upper end 39 of the ram 38, the latter is forced upwardly to lift the object supported ...upon the .end .39 orsby the toe'42. A return passage Sll'lea'ds fromlthe flowpassage '13 .to areturn pipe 51 which returns theLfluid tothe reservoir. 'The passage 50 normally is.closed.bya.ball '52 which isseated by means ofarelease screw.5-3. With the ball SZ-seated, the (fluid istrapped withinithe ram 38 to maintain the object in raised, position. When it .is desired t-olower the ram38, the screw 53 is loosened to allow unseating of "the ball .52 and return of .the fluidto the reservoir 15.

As thus far described, thejack structure is .identical withthat disclosed in my patent hereinbefore referred to. While such a jack ishiglily tficient in use, it has the disadvantage of allowing the ram to move upwardly to a position where the roller '45 may strike against the lower end of'the stationary.piston'head 35 to cause damage to 'thesefparts. The present invention is concerned with stop meansdesigned .to'limit'the upward strokeof the ram 38 toa'height wherein the roller "45 is located in proximity to, but spacedslightly below, the piston head '35 so as to prevent damage to these parts. The stop or strokelimiting means is constructed and arranged as next described.

The stop means '60 is in the nature of an automatically actuated valve and includes a sleeve-like seat element-61 which is screwed intoa threaded counterbore-62 at the upper end of the post 12, .the element having a bore 63 being coaxial and communicating with the passage 13. The seat element 61 has alower, reduced end 64 which carries an annular resilient seal 65, in the form of an ,0 ring which is compressedagainst the bottom surface of the counterbore 62 to seal the'threads of the seat element 61.

The stop means 60 also includes a plunger 70 which is "slidable vertically in the flow passage 13. The plunger 70 has an upper portion 71 which is fluted as indicated at 72, thisportion being slidable through the bore 63. The flutes or grooves 72 define with the bore 63 a plurality of channels 73 (Fig. through which the hydraulic fluid normally can'flow upwardly into and downwardly from the ram 38. The plunger 70 has a lower, circular portion 74 and an intermediate enlargement-or flange 75 providing a valve element, there being clearance between the periphery of the flange and the passage 13.

Pocketed within the passage 13 and surrounding the lower portion 74 is a coil spring 76. The lower end of the spring 76 seats against the lower end of the passage 13 and its upper end engaged under the valve flange 75. The compressed spring 76 thus functions to force the plunger 70 upwardly so as to maintain its upper end engaged against the under side of the closed end 39 of the ram 38.

Assuming that the ram 38 is in its lower, inoperative position with its closed end 39 adjacent the upper end 34 of the post 12, the valve flange'75 is located at a considerable distance below the'seat element 61. To lift an object, the jack is positioned to locate either its upper end 39 or its toe 42 beneath the object and the pump means 2% is actuated to force hydraulic fluid upwardly through the passage 13 and channels 73 to react between the upper end of the post 12 and the end 39 of the ram to force the latter upwardly and lift the object. During this upward, operative stroke of the ram, the upper end of the plunger 70 is maintained against the closed end 39 by the action of the spring 76.

'As the pumping action is continued, the plunger 70 slides upwardly and the roller 45 approaches the piston head 35. Eventually, the valve flange or element 75 engages against the lower end or seat of the sleeve-like element .61 to shut off theflow of the fluid into the ram and thusprevent further upward movement of the ram. The valve flange 75 istightlyseated againstelernent 61 due to the combined force of the fluid pressure acting against the effective area of the flange and the upward thrust of the spring 76. The length of the fluted portion 71 of the plunger above the valve portion is so calculated that the flow of fluid is stopped when the upper portion of the roller 45 is located slightly below the lower end of the piston head 35.

To lower the ram, it islonlynecessary to loosen the screw 53 to unseat .the ball 52, whereupon the weight of the ram causes the latter to descend under the influence of gravity, this .action forcing the fluid downwardly through the channels 73 and,passage 13 and thence through the returnline'50 and pipe51 into the reservoir. At the same time, the plunger 70 is pu'shed downwardly to inoperative position by the ram.

it is thus seen that by the present stop or limit means, upward movement of the ram through an operative stroke is positively checked so as .to avoid engagement of parts which would cause damage thereto. .The strokealimiting valve means is especially simple in construction and economicalto produce. Moreover, the valve means may be incorporated inhydraulic jacksduring the manufacture thereof, or readily installed in existing jacks without materially modifying their structure.

.In accordance with the provisions of the patent statutes, I have hereindescribed the principle of themvention, together with the construction which I now consider to represent the best embodiment thereof. I wish to have it understood, however, that the stroke-limiting means is suseptible of various modifications which would fall within the spirit and scope-of the invention, as defined in the appended claims.

I claim as my invention:

1. In a hydraulic motor having an upstanding post provided with an axial flow passage, a cylindrical ram slidable on said post and having an upper closed end, pressure fluid introduced between said post and said closed end effecting upward movement of .said ram through an operative stroke: anannular seat element detachably mounted in the upper end of said post and having -a bore coaxial with said :passage; an elongate plunger disposed 'coaxially within said flow passage and having an upper portion slidable in said seat element, said upper portion having longitudinally-extending grooves in its periphery defining with said bore aplurality of channels through which hydraulic fluid can flow from said passage into said ram, saidplunger'having an enlargement disposed below said seatelement and providing an annular valve .portion; :and a isprin'gpocketed within said passage and surrounding the lower end of said-plunger and engaging said-valve 'portion,'said spring being operative to force said plunger upwardly tomaintain its upper end in engagement with =said'closed end of said ram so as :to cause the plunger to move 'vertically with the ram, said valve portion being engagea'ble with said seat element to shutofl the'flow ofhy'clraulic fluid into said ram upon movement of said ram through a predetermined operative stroke.

2. A hydraulic jack as defined in claim 1 in which said seat elementconsists of an externally threaded sleeve screwed into a screw-threaded counterborein the upper end of said post,said seat element'having a'reduced lower extension; and a sealing riug'surroun'ding said-extension and compressed against the bottom'of said counterbore.

"References Cited in the file 'of this patent UNITED STATES PATENTS