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Publication numberUS692536 A
Publication typeGrant
Publication dateFeb 4, 1902
Filing dateDec 14, 1900
Priority dateDec 14, 1900
Publication numberUS 692536 A, US 692536A, US-A-692536, US692536 A, US692536A
InventorsHugh Mcdermid
Original AssigneeHugh Mcdermid
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Lifting-jack.
US 692536 A
Abstract  available in
Images(1)
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Claims  available in
Description  (OCR text may contain errors)

H. MGDERMID.

LIFTING JACK.

(Application filed Dec. 14, 1900.)

Patented Feb. 4,1902..

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UNITED STATES PATENT CFFIC.

HUGH MCDERMID, OF CHICAGO, ILLINOIS.

LIFTlNe-JACK.

sPEcIFIcATIoN forming perf; e'f Lettere Patent Ne. 692,536, dated :February 4, 1902. Application iiled December 14, 1900. Serial No. 39,872. (No model.)

T0 @ZZ whom, t may concern:

Be it known that LHUGH MCDERMID, a citizen of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Lifting-Jacks, of which the fo'l,

' handle is designed to be fitted. Journaled 'in and between the arms g g of the forked 1elowing is a specification.

My invention relates to lifting-jacks, the same being designed more particularly for use on railways for lifting tracks, cars, and other heavy objects; but its utility is by no means limited to such applications; and the principal object of my invention is to provide a simplied and improved mechanism for operating the vertical lifter-bar.

To this and other ends my invention consists in the parts and combinations of parts, as hereinafter more particularly described, and pointed out in the claims.

My invention is illustrated in the accompanying drawings, in Which'- Figure lis a view in central vertical section of myimproved lifting-jack. Fig. 2 is a plan view, partlyin horizontal section, on the line a: w of Fig. l; and Fig. 3 is a detail of the double pa-Wl.

Proceeding to a detailed description, A designates the main frame or casing of the jack, resting on and secured to a base-plate B. This frame or casing may conveniently be formed of a pair of parallel vertical standards, grooved and hollowed out on their opposing faces to form suitable guides for the lifter-bar C and its antifriction-bearings and securely clamped or riveted together in any suitable manner, as shown. The front face of the casing A is slotted through a portion of itslength, as at A', to permit the play therethrough of the foot C of the lifter-bar, and to the rear of the casing A are integrally or otherwise secured a pair of rearwardly-extending brackets C2 C3, between which is mounted and housed a portion of the lifter-bar-operating mechanism, as hereinafter more fully described.

D is a square shaft or spindle rotatably journaled between the two brackets C2 C3 and having fixedly secured thereon a pair of 'ratchet-wheels E E and between the latter a l ing almost the entire length of the latter.

Loosely mounted onrthe rounded ends of the shaft D is a forked lever, designated as a whole by Gand comprising a pair of parallel armsg g', rigidly united at one end by a crossbar g2, from the center of which latter extends a handle-socket g3, in which a long wooden ver is a double pawl H, the two noses of which are normally kept pressed in engagement with the ratchets E E by a spring a in the `manner plainly shown in the drawings. The

rearwardly-extending shank of the pawl has a hole h formed therethrough for a purpose hereinafter explained, and its two ends are' extended at h h2 to engage recesses b b', cut in the upper edge of the arms g g for a purpose hereinafter disclosed. e

Pivoted between the brackets C2 C3, ,above the shaft D, is a pawl I, the nose of which normally engages the teeth of the rack c on the lifter-bar to hold the latter in the position to which it has been raised by each successive power-stroke of the operating mechanism. Pivoted on the back of this pawl I is a hooked link t', which at a certain point in the operati-on of the device is designed to engage the shank of the double pawl H, preferably in the hole h therein. The pawl I is yieldingly held in engagement with the rack c by any suitable means, as a spring m, the free end of which removably engages a hook t" on acter and to the fact that the power is applied to the rear of the bar, Whilethe resistance orload is usually applied to its front, (on the foo,t,) lthe front and rear faces of the lifter-bar engage their guides in the casing Awith great friction and consequent Awear upon the parts. Howto best overcome this friction and consequent wear has been a matter of much study and experiment with me,

lifter-bar is subjected in jacks of this charand I will now describe the means which I I prefer to employ for this purpose.

upper front part of the casing A and directly in advance of the front face ofthe lifter-bar C is formed a vertical race d, which is filled with a series of hardened-steel balls e of the proper diameter to just engage the face of the lifter-bar, While in the heel of the lifter- In thev vroor bar itself I journal one or more (preferably a series) of hardened-steel rollers f, which engage the rear lower wall of the casing A. It will thus be seen that I provide antifriction-bearings of considerable length on both the front and rear faces of the lifter-bar.

In order to keep the lifter-bar from dropping out of the casing through the slotted base-plate B when at work, as well as to permit the removal of the lifter-bar in that manner when desired for repairs or for any other reason, the upper end of the lifter-bar may be provided with a removable screw-threaded cap K, which may have a broad flat top for the purpose of engaging an object too high to be conveniently engaged by the foot C.

The operation of my improved jack in lifting a load will be readily understood. The foot or cap (as the case may be) of the lifterbar having been secured beneath the object to be raised, the handle of the forked lever G is worked up and down. Af every downstroke the noses of the double pawl II engage the teeth of the ratchet-wheels E E', thereby turning the shaft D and the gear-wheel Rand, through the engagement of thelatter with the rack c, raising the lifter-bar and its engaged load through a small distance. rIhe springm keeps the pawl I in constant engagement with the teeth of the rack @,whereby the lifter-bar C and its load are sustained in their raised positions each time the handle of the forked lever G is being raised preparatory to another powerstroke. During these strokes the front and rear faces of the lifter-bar undergo a rolling rather than a sliding contact with their guides in the casing A, owing to the presence of the balls e and rollers f, thus greatly diminishing the friction and wear on these cooperating parts. l/Vhen the load has been lifted the desired height and secured there, the spring m is disengaged from the hook fi and the hooked link -i is allowed, on the next upward movement of the forked lever G to drop into engagement with the hole hin the shank of the double pawl II. The following downstroke of the forked lever G thereupon withdraws the pawl I through the hook t' from engagement with the rack c, and at the same time the double pawl I-Iis by the hook t' withdrawn from engagement with the ratchets E E, as shown in dotted lines in Fig. 1, thus leaving the lifter-bar C free to descend by its own weight to its lowest position, whereupon the above-described operation may be repeated. During the downward or power strokes of the lever G there is obviously an enormous strain upon the journals of the double pawl 1I. This strain is partly relieved and any tendency of the pawl to buckle is prevented by the engagement of the projections h h2 with the cut-outs b Zi' of the lever-arms g g.

Although I prefer to use a pair of ratchetwheels and a double pawl, as hereinabove described, nevertheless it is manifest that in some cases a single ratchet-wheel and a single pawl might be suflicient, and hence I do not wish to be understood as limiting myself to the double construction (except where speciiicallyrecited)in combination with the other elements of my device.

Having thus described my invention, what I claim as new, and desire to secure by Letters Patent, is-

l. In a lifting-jack, the combination with the casing and the lifter-bar guided to slide vertically therein, of a rack formed on the rear face of the lifter-bar, a pair of brackets secured to the casing, a shaft journaled in said brackets, a gear fast on said shaft and engaging said rack on the lifter-bar, a ratchetwheel also fast on said shaft, a lever loosely mounted on said shaft, aspring-pressed pawl journaled in said lever and normally engaging said ratchet-wheel, a pawl journaled between said brackets and normally engaging the teeth of the rack on the lifter-bar to keep the latter elevated, and separable connections between the two pawls whereby, when they are connected, a downward stroke of the lever withdraws the last-named pawl from the rack and simultaneously withdraws the firstnamed pawl from its ratchet-wheel, substantially as described.

2. In a lifting-jack, the combination with the casing and the lifter-bar guided to slide vertically therein, of a rack formed on the rear face of the lifter-bar, a pair of brackets secured to the casing, a shaft journaled in said brackets, a gear fast on said shaft and engaging said rack on the lifter-bar, a pair of ratchet-wheels also fast on said shaft, one on either side of said gear, a forked lever loosely mounted on said shaft,a spring-pressed double pawl journaled between the arms of said lever and normally engaging said ratchetwheels, a spring-pressed pawl journaled between said brackets and normally engaging the teeth of the rack on the lifter-bar to keep the latterelevated, and separable connections between the two pawls whereby they maybe simultaneously disengaged from their respective coperating parts by a single downward stroke of the lever, thus allowing the lifterbar to drop, substantially as described.

3. In a lifting-jack, the combination with the casing and the lifter-bar guided to slide vertically therein, of a rack formed on the' rear face of the lifter-bar, a pair of brackets secured to the casing, a shaft journaled in said brackets, a gear fast on said shaft and engaging said rack on the lifter-bar, a pair of ratchet-wheels also fast on said shaft, one on either side of said gear, a forked lever loosely mounted on said shaft, a spring pressed double pawl journaled between the arms of said lever and normally engaging said ratchetwheels, a spring-pressed pawl journaled between said brackets and normally engaging the teeth of the rack on the lifter-bar to keep the latter elevated, and a hook pivoted in the back of said last-named pawl and adapted, when the lever is raised to a certain height,

IOO

IIO

IZO'

to drop over and engage the shank of said first-named pawl, whereby, on the next down-l ward stroke of the lever the two pawls are simultaneously disengaged from their respec#` tive coperating parts, thus allowing the lifter-bar to drop, substantially as described.

4. In a paWl-and-ratchet operating mechanism for lifting-jacks and similar devices, the combination with a rotatable shaft having fast thereon a pair of ratchet-*wheels and' an intermediate power-transmitting wheel, of a forked operating-lever pivoted on the ends of said shaft, and adouble pawl journaled between the arms of said forked lever and normally engaging said ratchet-wheels, the shank of said pawl having projections which x5 extend laterally over and engage the upper edges of the armsof saidlever, substantially as and for the purposes described.

In testimony that I claim the foregoing as myinvention I-have hereunto signed my name zo in the presence of two witnesses.

HUGH MCDERMID.

Witnesses: I

SA- UEL N. POND,

, ADAl H. BARNES.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US5540696 *Jan 6, 1995Jul 30, 1996Zimmer, Inc.Instrumentation for use in orthopaedic surgery
Classifications
Cooperative ClassificationB66F3/02