US2575108A

US2575108A - Lifting jack

Info

Publication number: US2575108A
Application number: US9726A
Authority: US
Inventors: Howard Arthur Clifford
Original assignee: Individual
Current assignee: Individual
Priority date: 1944-03-14
Filing date: 1948-02-20
Publication date: 1951-11-13
Anticipated expiration: 1968-11-13

Description

NOV. 13, 1951 A Q HOWARD 2,575,108

LIFTING JACK Filed Feb. 2o, 1948 s Smeets-sheet 1 Fig. I

J Bw] Aitor/1e y NOV. 13, 1951 A, Q HOWARD 2,575,108

LIFTING JACK Filed Feb. 20, 1948 3 Sheets-Sheet 2 Innen or ARTHUR ammo Nov. 13, 1951 A. c. HOWARD LIFTING JACK 3 Sheets-Sheet 5 Filed Feb. 20, 1948 m/Vf/v'nl? A. C. HOWARD e www #7i/1ML? I ATTORNE Patented Nov. 13, 1951 Application Febriiary 20,1948, serial No. 9,726 In Great Britain March'14, 1944 Section 1, Public Law 690, AugustS, 1946 VPatent expires March 14, 1964 Y zclaims. (0.1.""14-169') This invention relates to lifting jacks of the y kind having a rack provided with ratchetteeth that is slidably supported in a pedestal, andtwo pawls by which the rack is raised, retained, and lowered; the rack being provided With a lifting head, and one or both pawls being respectively pivoted to a hollow operating lever according as to whether the jack is singleor double-acting.

With single-acting jacks of the kind set forth, it has been the practice to pivot a lifting pawl by trunnions in bearings formed in the sides of the hollow operating lever in a position between the fulcrum of the latter and the rack, and to pivot a detent pawl to the pedestal in a position above the lifting pawl. In this way, when the operating lever has been depressed, the lifting pawl raised the rack a distance slightly greater than one tooth, and the detent pawl engaged the tooth next below the one it previously engaged. Upon raising the operating lever, the rack was permitted to rest upon the detent pawl, and the lifting pawl was lowered into engagement with the tooth next below the one it previously engaged in readiness for lifting the rack another step. Both of the pawls werefso poised 1 .or spring-loaded that they were urged against the rack, and suitable means for lowering the rack were provided whereby the poise or spring-loading of the two pawls could be modified so that upon depressing the operating lever,`the lifting `pawl raised the rack just sufficiently to free the detent pawl and permit it to be retracted from the rack, and upon raising the operating lever the rack was lowered under the control of the lifting pawl until the detent pawl moved into engagement with the next higher tooth on the rack.

With double-acting jacks of the kind set forth, the construction was similar to that above described but with the principal difference that the detent pawl was supported by trunnions in bearings formed in the sides of the hollow'op- -erating lever, but en the opposite side of the fulvcrum to the bearings for the lifting pawl, and itselfV acted as a second lifting pawl. In this way, the rack was raised one tooth for each upward vand each downward movement of the operating lever. Similarly, when the poise or springloading of the two pawls had been modied as referred to above, the rack was lowered by one `.tooth for each upward and each downward move- ,ment of the operating lever.

A cardinal limiting factor of the mechanical .advantage obtainable with jacks of the kind set forth isk the amount of metal that must be a1- lowed to remain between the bearings for. thefuIfcrum pin of the operating lever and for the trunnions of the pawl or pawls in order that the operating lever was not weakened.

Accordingly, the present invention has for its object a method of supporting the operating lever and lifting pawl of a single-acting jack ofthe kind set forth, and the operating lever and lifting and detent pawls of a double-acting jack of the kind set forth, so that the axes of said pawl or pawls can be set nearer to the operating lever .fulcrum than has hitherto been possible without undesirably weakening thel operating lever.

According to the invention, a hollow operating lever, for a single-acting jack of the kind set forth,.has a pair of trunnions which serve for fulcruming the lever in the jack, and has a bearing barrel arranged, with its axis parallel to, ,but off-set from, the axis of the trunnions, to bridgean opening in the lever in the region of the trunnions, and to provide a convex bearing surface to coact with a corresponding concavity inthe foot of the lifting pawl, which latter is lin the lever in the region of the trunnions, each ofthe barrels providing a convex bearing surface to coactrwith a corresponding concavity in the feet of the lifting and detent pawls, respectively, which pawls are held in these positions so as to be rockable circumferentially of the associated barrels. e i

The, or each, pawl can be held in position on its bearing barrel by a metal strap which. is

secured. to the'V former and-passes either lcom pletely or partially around the barrel. In the case of a double-acting jack, these straps can be of the-latter type and be passed over the remote sides ofthe two barrelsso as to permit of there being a minimum of space between the latter.

The operating lever, trunnions, and bearing barrels may be cast in one piece, in which event thelower portions of the trunnions and bearing barrels at their adjacent ends may merge into leach other, so as to enhance the strength of the casting, and a space is left between the bottoms of the bearing barrels and the lower wall ofthe hollowoperating lever so as tolaccommodate the aforesaid straps. Alternatively, the structure may be welded together or otherwise fabricated.

The aforementioned straps may be J -shaped so that they can be secured to their respective pawls,

as by riveting, and extend suflicientlyround their respective bearing barrels to retain the pawls in position. Alternatively, particularly in the case of a single-acting jack, the straps may be U- Y than half of the circumference of the barrels,

shaped and have both ends attached to the paw'l. "l0

The straps may, in some instances, be recessed into their pawls and bearing-barrels.

A major advantage accruing rom the present invention is the fact that the diameters for the trunnions and bearing barrels can bemad'e -foi .I5

adequate size Without reference to the distance between their respective axes, also, thatas'fthle; bearing .barrels can be set above the leve'l of the trunnions, the full width of the former can bef,l

utilised for the bearinglfsurface for the pawls.

In the accompanying drawings, Y

Fig. 1 is a side elevation, yin part section,cf -a double-acting jack, of known type, Vembodying the present invention, and showing a tommy bar in position,

2 is a plan view, in part section, of the operating lever showing the arrangement :of the lever'trunnions and the bearing barrels,

r Fig.3 is `a longitudinal section indicated by thel'arrows 3-3'in Fig. 2,

Fig. 4 anend View from .the .left ci Fig. i2.

Fig. 5 isa Adetail lview of one 'of the pawls,

Fig. 6 is a view corresponding to Fig. 2 .but 'showing oneof the pawls in positioman'd the straps passing through the spaces I6 bel'tween the bottoms of the barrels and the lower wall ofthe operating lever.

' It "will be seen that the pawls can be mounted much "closer together and to the operating lever fulcrurn than if they were themselves pivoted uponpins, as hitherto, with a resultant increase the .mechanical advantage obtained. Also,

Figures 7 and 18v 'are 'views corresponding `'ref -35 spec-tively vwith Figures V1 and .3 .but illustrating a single-'acting jack according tothe invention.

Referring now to the drawings, the jack 4com- `prises a'pedestal I having affect 2.an'd ahandle 3 by `which the jack can-be :moved frornplace .to 4D place. The Vpeck-:stal contains .a .rack f4 .having -ratchet' teeth and is surmounted Vvby fa lifting head .'i. A hollow. operating lever 8, the vconist'ruction of whichwill be described later, is .pivoted in the pedestal and'carries a .lifting `pawl 7l land ,a detent pawl 8. YThe two pawls Aare connected by Ya .spring-loading device, indicated vgenerally .at 8, incorporating fa bell-'crank lever IU and a'connectingrrod II by 'which the springloading on the pawls is modified so 'as either'to vv50 cause the rack to vbe raised step-by-step, or lowered in the same way, 'for each 'up and down movement of the operating lever, and according to the position of the bell-crank. AThis raisinsr and lowering mechanism is of known kind and,

as stated above, the improvements eiected by the present invention reside in the Aformation and disposition of the pivots 'for the operating lever and the two pawls.

The operating lever 6 has two integraltr'un- 3 nion pins I2 projecting outwardly from .its side Walls and adapted to be received in bearingsin the sides of a slot inthe pedestal. The "inner end of the lever 6 is .openz'at the-top, and the said `side walls are bridged by two bearingbarrels 'I3 vand I4, also formed integrally therewith. The lower portions of the adjacent sides of the barrels, rat their ends, areY preferably fairedintothe side walls of the operating lever, as indicatedJat I5, for the purpose of vstrengthening the structure, and a space .is leit .between 'the bottoms `of the barrels and the lower wall of the lever, 'as indicated at I6., for .the purpose hereinafter described.

f Thefootoeach pawl providedzwith la`con- 'owingvto the greatly increased bearing area, and the robustness of the bearing barrels, as compared with the pins as hitherto used, a greater load, commensurate with the enhanced mechanical advantage, can be sustained without danger of damaging the jack. Furthermore, the trunnions I2 caribe made more robust -than the pivot pin Ahitherto used for supporting the operating lever, and as these trunnionpins are on the opposite sides of the side walls of the operating lever to the vbearing barrels for the pawls, said pins and .barrels can be made to over-lap.

The straps I8 .serve merely to locate ther-pawls and do not take any further load; they can, therefore, be made narrow, and the spaces 'be tween and beneath the barrels, need be only :of suliicient size to accomodate them, thus `avoid-- ing unduly increasing the size of the operating lever 'to secure adequate strength.

The single-acting .jack illustrated by Figures 7 vand 8 has its parts indicated by Alike reference numerals, and it will be seen that it only differs from the double-acting .jack in that the barrel I4 is omitted and the .pawl 8a is pivoted to the ljack body at Ma.

In both forms of the invention spaced side walls 2U at 'the inner end of the handle 6 define a space .which vis open upwardly and outwardly and closed only at the sides by the walls 20 and at the lower part by 'a bottom wall 2I which 'may have at its Yfree Vend an upstanding rib 22 which may be 'in the saine general vertical plane with the 'trunnions I2 and in the case of li'igure 3 pro yjects up toward the space between the two bearing .barrels 13 and I'4,' and generally acts to strengthen the structure.

It will be notedv that the bearing barrel verbaryrels bridge the space between 'the side Walls 20 and Yare spaced above the bottom wall 2| "and its rib 22, while the trunnions I2 are completely outside the 'space coniined `between the side Walls 2U and in fact project laterally in opposite directions from the `outside surfaces of the side 'Walls 20.

Whilst the invention has been described with jreference to one form of lifting jack, it 4will-:be understood-that it is equally applicable to the support of voperating levers and theV p'awls Vmounted thereon for use with other types `of jaclc What I claim as my inventionV and desire to secure by Letters VPatent of the United States is:

1. For use -with a jackhaving `a pedestal Vand a rack bar slidable inthe pedestal, an improved operating yhandle and Dawl construction comprising a v'handle member .having spaced walls at an end portion thereof with 'the space lbe- -tween-l the walls opening upwardly :and out wardly, trunnions integral with said walls projecting laterally therefrom and adapted to be journaled in the pedestal, a bearing barrel integral with said side walls and disposed therebetween in radially-overlapping but axially-01T- set relation to said trunnions, a pawl adapted to engage the rack bar and having a partcylindrical concavity rotatably received over said bearing barrel, and securing means for retaining the paWl against detachment from said bearing barrel.

2. For use with a jack having a pedestal and a rack bar slidable in the pedestal, an improved operating handle and pawl construction comprising a handle member having spaced walls at an end portion thereof with the space -between the walls opening upwardly and outwardly, a trunnion formed integral with each of said side walls and projecting laterally from the outer surface of each of said side Walls with the axes of the trunnions substantially in alignment transversely of said walls, said trunnions being adapted to be journaled in the pedestal, and bearing barrels integral with said side walls and bridging the space between said side walls and 6 disposed in spaced apart relation from one another, said bearing Abarrels radially-overlapping and being axially-offset from the transverse line of the axes of said trunnions, pawls adapted to engage the rack bar and having part-cylindrical concavities rotatably received one over each of said bearing barrels, and securing means for retaining the pawls against detachment from their respective bearing barrels.

ARTHUR CLIFFORD HOWARD.

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

UNITED STATES PATENTS Number Name Date 437,077 Alfred Sept. 23, 1890 1,107,611 Hindman Aug. 18, 1914 1,483,665 Klasing Feb. 12, 1924 1,802,067 Reif Apr. 21, 1931 FOREIGN PATENTS Number Country Date 163,621 Great Britain May 26, 1921