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Патент USA US3096977

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July 9, 1963
Filed June 4. 1962
2 Sheets-Sheet 1
Jacob A. Duke
July 9, 1963
Filed June 4, 1962
'2 sheets-sheet 2
Jacob A. Duke
United States Patent Office
Patented July 9, 1963
Jacob A. Duke, 1338 Foxwood, Houston 8, Tex.
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 improve
ments in the construction of `a mechanically operated
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 pivot
ally 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
jack which incorporates safety features to enable the jack 10 terminate centrally and inwardly of the side plates 9
where they are pivotally connected to a shaft 27 having
to be used indefinitely without danger of collapse.
a spacing sleeve 28 to maintain the spaced relationship
There have been many different designs of lifting de
of the arms. The shaft 27 projects through vertical slots
vice which provide various degrees of mechanical ad
29 formed in each of the side plates 9 and is restricted
vantage. Whilst these devices perform effectively for
short periods of time, they are not generally considered 15 to vertical movement therewithin in response to raising
and lowering the thrust block 15. A shaft 3() is rotat
suitable for supporting loads indefinitely. The safety of
ably supported in a bearing 31 which is mounted on the
a jack under permanent load is also a function of the
pedestal 11 and the protruding ends of the shaft are
base area of the jack, and permanent stability demands
threaded in opposite hands as indicated at 32 `and 33.
a relatively high base to height ratio.
It is therefore a primary object of this invention to 20 The threaded ends of the shaft extend through threaded
holes 34 formed centrally through the spacer blocks 23
provide a mechanically operated jack suitable for sup
and terminate therebeyond lwith suitable socket catches
porting continuous loads and incorporating safety fea
35 for removably receiving a driving crank 36. It will
tures which will prevent collapse of the jack in the event
of thread failure of the screw drive which aotuates the
thus be seen that rotation of the driving crank 36 in the
25 socket catch at either end of the shaft 30 will cause the
spacer blocks 23 to move towards or away from each
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.
other and thereby causing the thrust block 15 to rise
or lower as required.
A bearing plate 37 is supported on a threaded post
It is a still further object of this invention to provide
a mechanical jack which may be operated remotely by 30 38 which adjustably protrudes through the threaded hole
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 sec
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
ondary extension for adjusting the maximum lift thereof. 35 to the outer sides of the side plates and disposed from
the lower corners thereof to extend upwardly in a con
A full understanding of the details of the invention,
verging manner as seen `best in FIG. 2. These bars are
together with further advantages, will become apparent
notched at 40 along their outer edge for engagement by
by reference to the following detailed description of a
the shaped ends 41 of locking levers 42 which are pivot
preferred embodiment thereof, taken in conjunction with
40 ally mounted at their upper ends to the pins 26 which
the attached drawings wherein:
FIG. l is a plan view of the jack which comprises my
FIG. 2 is a front elevation of the jack showing the
safety device in the engaged position.
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 posi
tioned adjacent the notched bars 39 for immediate en
FIG. 3 is a cross sectional end elevation taken along 45 gagement therein in the event of structural failure of
the jack. Catches 44 are pivotally mounted to the centre
the line 3-3 of FIG. l.
of the locking levers 42 and have hooked end portions
FIG. 4 is a fragmentary c-ross sectional plan View taken
45 which may be selectively engaged over the trunnions
along the line 4-4 of FIG. 2.
24 as indicated in broken lines in FIG. 2, so as to main
FIG. 5 is a fragmentary perspective View showing the
slide mounting of the thrust block which supports the 50 tain the safety catch in the released position whilst lower
ing the jack. The added safety afforded by these auto
matic locking levers will be quite apparent to those
Similar reference characters indicate corrmponding
familiar with the operation of mechanical type jacks.
parts throughout the several views in the drawings.
' Having described the invention with considerable par
Referring now to Ithe drawings in detail, the numeral
8 represents `a flat rectangular base which mounts two 55 trcularity, it sho-uld be understood that various modifica
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
tions 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
formed therealong `and extending towards each other to 60
base, side plates upstanding along opposite sides of the
receive the slide plate 14 of a thrust block 15 there
base, a pedestal mounted centrally of the base and in
which form the corners of a square and have grooves 13
cluding four guides projecting upwardly therefrom, a
The thrust block lhas a vertical threaded hole 16 pass
thrust block including downwardly extending plates for
ing centrally therethrough and has the two slide plates
slideably engaging in said guides, two upper pairs of
14 extending therebeneath in a parallel spaced relation 65 pivotally jointed «arms mounted on opposite sides of the
ship as seen best in FIG. 5, of the drawing. Pour ears
thrust block, two lower pairs of arms pivotally mounted
17 project horizontally from the upper end of the thrust
at their lower ends to said side plates, horizontally spaced
block and are suitably drilled to receive pins 18 there
trunnioned spacer yblocks pivotally connecting said upper
through for pivotally mounting four downwardly diverg 70 and lower pairs of `arms together, a shaft threaded in
ing arms 19. Four further arms 20 are pivotally secured
opposite hands at each end threadably engaging through
at their lower end by means of pins 21 and spacers ‘22
the spacer blocks to cause the said 'blocks to converge
and diverge with respect to each other in response to
Vrotation `of the shaft, stabilizing bars pivotally connected
selective engagement with the notched bars, and catches
on said locking levers for selectively maintaining said
to the upper pairs of arms intermediate the length of the
levers out of engagement with said bars.
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 oon
verging downwardly and terminating with pivotal mount
ing on the stabilizing shaft, and a locking mechanism
comprising upwardly converging notched bars secured to 10
the outer side of vthe side plates, locking levers pivotally
extending from said upper pairs of jointed arms for
References Cited in the ñle of this patent
Grant ________________ __ Oct. 16, 1923
Piper _______________ __ Mar. 11, 1924
Fee Hern et al _________ __ Dec. 13, 1927
Germany ____________ __ Apr. 16, 1935
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