US3096967A - Mechanical jack - Google Patents

Description

J. A. DUKE MECHANICAL JACK July 9, 1963 Filed June 4. 1962 2 Sheets-Sheet 1 Illlllllul.:

INVENTOR Jacob A. Duke July 9, 1963 J. A. DUKE 3,096,967

MECHANICAL JACK Filed June 4, 1962 '2 sheets-sheet 2 IN V E N TOR Jacob A. Duke United States Patent Office 3,096,967 Patented July 9, 1963 Filed June 4, 1962, Ser. No. 199,743 1 Claim. (Cl. 254-126) This invention relates generally to lifting devices, and more specifically to certain new and useful improvements in the construction of `a mechanically operated jack which incorporates safety features to enable the jack to be used indefinitely without danger of collapse.

There have been many different designs of lifting device which provide various degrees of mechanical advantage. Whilst these devices perform effectively for short periods of time, they are not generally considered suitable for supporting loads indefinitely. The safety of a jack under permanent load is also a function of the base area of the jack, and permanent stability demands a relatively high base to height ratio.

It is therefore a primary object of this invention to provide a mechanically operated jack suitable for supporting continuous loads and incorporating safety features which will prevent collapse of the jack in the event of thread failure of the screw drive which aotuates the jack.

It is a further object of this invention to provide an efiicient mechanical jack which is specially designed for supporting house trailers and heavy duty vehicles.

It is a still further object of this invention to provide a mechanical jack which may be operated remotely by rotation of the drive screw in a horizontal axis.

It is yet a further object of this invention to provide a mechanical jack of the above class which is rugged in construction, simple to operate, and incorporates a secondary extension for adjusting the maximum lift thereof.

A full understanding of the details of the invention, together with further advantages, will become apparent by reference to the following detailed description of a preferred embodiment thereof, taken in conjunction with the attached drawings wherein:

FIG. l is a plan view of the jack which comprises my invention.

FIG. 2 is a front elevation of the jack showing the safety device in the engaged position.

FIG. 3 is a cross sectional end elevation taken along the line 3-3 of FIG. l.

FIG. 4 is a fragmentary c-ross sectional plan View taken along the line 4-4 of FIG. 2.

FIG. 5 is a fragmentary perspective View showing the slide mounting of the thrust block which supports the load.

Similar reference characters indicate corrmponding parts throughout the several views in the drawings.

Referring now to Ithe drawings in detail, the numeral 8 represents `a flat rectangular base which mounts two normally upstanding spaced apart side plates 9 which terminate upwardly with an `arc-uately formed edge 1t). A pedestal 11 is formed by four vertical sleeve guides 12y which form the corners of a square and have grooves 13 formed therealong `and extending towards each other to receive the slide plate 14 of a thrust block 15 therebetween.

The thrust block lhas a vertical threaded hole 16 passing centrally therethrough and has the two slide plates 14 extending therebeneath in a parallel spaced relationship as seen best in FIG. 5, of the drawing. Pour ears 17 project horizontally from the upper end of the thrust block and are suitably drilled to receive pins 18 therethrough for pivotally mounting four downwardly diverging arms 19. Four further arms 20 are pivotally secured at their lower end by means of pins 21 and spacers 22 to the inner side of 4the side plates 9. These further arms diverge outwardly and upwardly and terminate in a pivotal relationship with the outer ends of the arms 19, the said ends being spaced apart by a spacer block 23 having trunnions 24 projecting from cach end for pivotally mounting the ends of the converging arms 19 and 20. Stabilizing arms 25 are secured by pins 26 to the diverging arms 19 at a point inwardly spaced from their outermost ends. These arms converge downwardly and terminate centrally and inwardly of the side plates 9 where they are pivotally connected to a shaft 27 having a spacing sleeve 28 to maintain the spaced relationship of the arms. The shaft 27 projects through vertical slots 29 formed in each of the side plates 9 and is restricted to vertical movement therewithin in response to raising and lowering the thrust block 15. A shaft 3() is rotatably supported in a bearing 31 which is mounted on the pedestal 11 and the protruding ends of the shaft are threaded in opposite hands as indicated at 32 `and 33. The threaded ends of the shaft extend through threaded holes 34 formed centrally through the spacer blocks 23 and terminate therebeyond lwith suitable socket catches 35 for removably receiving a driving crank 36. It will thus be seen that rotation of the driving crank 36 in the socket catch at either end of the shaft 30 will cause the spacer blocks 23 to move towards or away from each other and thereby causing the thrust block 15 to rise or lower as required.

A bearing plate 37 is supported on a threaded post 38 which adjustably protrudes through the threaded hole 16 formed centrally and vertically through the thrust block 1S. This feature enables further adjustment in the degree of lift available from the jack.

The safety catch device comprises four bars 39 secured to the outer sides of the side plates and disposed from the lower corners thereof to extend upwardly in a converging manner as seen `best in FIG. 2. These bars are notched at 40 along their outer edge for engagement by the shaped ends 41 of locking levers 42 which are pivotally mounted at their upper ends to the pins 26 which secure the stabilizing arms 25. The levers incorporate balancing arms 43 projecting normally therefrom such that the shaped ends 41 of the levers are constantly positioned adjacent the notched bars 39 for immediate engagement therein in the event of structural failure of the jack. Catches 44 are pivotally mounted to the centre of the locking levers 42 and have hooked end portions 45 which may be selectively engaged over the trunnions 24 as indicated in broken lines in FIG. 2, so as to maintain the safety catch in the released position whilst lowering the jack. The added safety afforded by these automatic locking levers will be quite apparent to those familiar with the operation of mechanical type jacks.

Having described the invention with considerable partrcularity, it sho-uld be understood that various modifications may be made to the precise detail thereof, without departing from the scope or spirit of the invention, as defined in the appended claim.

I claim:

A mechanical jack with safety locks, comprising, a base, side plates upstanding along opposite sides of the base, a pedestal mounted centrally of the base and including four guides projecting upwardly therefrom, a thrust block including downwardly extending plates for slideably engaging in said guides, two upper pairs of pivotally jointed arms mounted on opposite sides of the thrust block, two lower pairs of arms pivotally mounted at their lower ends to said side plates, horizontally spaced trunnioned spacer yblocks pivotally connecting said upper and lower pairs of `arms together, a shaft threaded in opposite hands at each end threadably engaging through the spacer blocks to cause the said 'blocks to converge and diverge with respect to each other in response to to the upper pairs of arms intermediate the length of the said arms, a stabilizing shaft extending through said plates, said plates having vertical slots formed therein to receive the stabilizing shaft and restrict the saine to movement in a vertical plane, said stabilizing bars oonverging downwardly and terminating with pivotal mounting on the stabilizing shaft, and a locking mechanism comprising upwardly converging notched bars secured to the outer side of vthe side plates, locking levers pivotally extending from said upper pairs of jointed arms for selective engagement with the notched bars, and catches on said locking levers for selectively maintaining said levers out of engagement with said bars.

References Cited in the le of this patent UNITED STATES PATENTS 1,470,830 Grant Oct. 16, 1923 1,486,797 Piper Mar. 11, 1924 1,652,821 Fee Hern et al Dec. 13, 1927 FOREIGN PATENTS 617,313 Germany Apr. 16, 1935

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