US1737153A - Safety device for screw jacks - Google Patents

Description

Nov. 26, 1929. F. GORMLEY 1,737,153

SAFETY DEVICE FOR SCREW JACKS Filed Jan. 6. 1928 Fly. 1.

liwenlor: Irmlkl. Gormley,

Patented Nov. ltiil FATET OFFECE FRANK L. G GR-MLEY, OF CHICAGO, ILLINOIS, ASSIGNOR TO THE BUDA COMPANY, OF HARVEY, ILLTNOES, A CORPORATION OF ILLINOIS SAFETY DEVICE FOR SCREW JACKS Application filed January 6, 1928. Serial No. 244,860.

This invention relates to journal or other jacks which heretofore have not been provided with means for retarding the lowering of the lifting screw under the weight of the load, the object of the present invention belng the provision of simple but effective means for preventing the accidental turning of said lifting screw and particularly when the screw has become worn.

This object is attained by the mechanism illustrated in the accompanying drawing.

For the purpose of illustrating the invention, one preferred form thereof is illustrated in the drawings, this form having been found to give satisfactory and reliable results, al-

. though it is to be understood that the various instrumentalities of which the invention consists can be variously arranged and organized, and the invention is not limited to the precise arrangement andv organization of these instrumentalities as herein shown and described except as required by the scope of the appended claims.

Of the drawings: t

Figure 1 represents a vertical section of a lifting jack embodying the principles of the present invention, and

Figure 2 represents a partial horizontal.

section on line 2, 2, on Fig. 1.

Similar characters indicate like parts throughout the several figures of the drawings.

- In the drawings 10 is a casing having a cylindrical bearing at its upper end in which the standard 11 is adapted to reciprocate, said standard being prevented from turning about its axis by the key 12 secured to casing 10 and projecting into the vertical slot 13 of standard 11.

The lower end ofthe standard 11 has secured therein a nut 1 f coacting with the rotatable steep pitch screw 15, the lower end of which has keyed thereto a bevel gear 16 meshing with another bevel'gear 17 formed upon the inner end of a driving shaft 18 revoluble in a bearing in the casing 10 and having an actuating device 19 on the outer endthereof.

The actuating device which preferably is used on this driving shaft 18 is that shown in another application of mine, filed Dec. 21, 1926 and numbered 156,109 towhich reference may be made as to construction and operation.

The gear 16 rests upon a bearing plate or disk 20 superimposed upon a plurality of balls 21 disposed in a circular track formed in the upper face of another plate or disk 22 supported upon the removable bottom 23 of the casing 10.

This bottom member 23 is preferably threaded to the lower part of the casing as indicated at 24.

The threads of the lifting screw 15 in a jack of this character must necessarily have a coarse pitch in order to maintain speed when lifting and lowering and still have the jack compact as otherwise it would be necessary to use gears of much greater diameter if the pitch of the screw threads is reduced.

This would necessitate making the lower end of the casing of greater diameter, therer by increasing the weight of the jack and making it awkward to handle.

Moreover, it would be so bulky that it could not be used in some places, especially in close quarters where there would not be room for the actuating device 19 to be operated to run its standard up to and from the load to be raised.

With this steep coarse pitch of thread in screw and its coacting nut 14 a certain amount of wear takes place between these two members after the jack has been in use some time due to the frictional contact between the contacting screw threads and nut threads.

This is very objectionable for the reason that as the wear increases there is a tendency for the standard 11 having a load thereon to cause the screw 15 to turn and thereby accidentally lower the load.

Some means therefore should be provided in jacks of this character to prevent this accidental lowering and one way of accomplishing this is shown in the drawings.

To this end bosses 25 are formed upon the casing 10 these bosses 25 having recesses 26 therein in which are disposed the shanks 27 of shoes 28, the inner faces of which are curved to fit the periphery of the bearing plate 20 on which the gear 16 rest-s and with which it is in frictional contact.

The bosse 25 are in alinement and on opposite sides of the casing 10.

Surrounding each shank 27 is a coiled spring 29 which forces the shoe 28 into contact with the periphery of the bearing plate 20.

The outer ends of the bosses 25 have threaded plugs 30 which may be adjusted to vary the tension of the springs 29.

There is sufficient frictional contact between shoes 28 and the plate 20 to prevent this plate from turning under normal conditions but when a load is on the standard the friction between the gear 16 and plate 20 exceeds the friction between the shoes 28 and plate 20 so that said plate 20 will rotate with said gear during the raising and lowering of the load by rotating the ear 17 and the driving shaft 18.

WVhen the main screw 15 is not rotated by manual power the friction between shoes 28 and plate 20 will be sufhcient to prevent any rotation thereof under the weight of the load and this is true even when the threads of screw 15 and nut 1 1- are practically worn out.

This friction between the shoes 28 and plate 20 is also sufficient to overcome the frictional contact between ratchet and pawl in the actuating device 19 so that the standard 11 may be raised by short strokes of said actuating device.

Parallel flanges 31 extending inwardly from the casing 10 and contacting with the upper and lower faces of the shoes 28 prevent these shoes from turning about the axes of the shanks 27.

The friction devices are shown coacting with the periphery of the bearing plate 20 and this is the preferred construction but it is quite obvious that said friction devices may be applied to some other cylindrical member rotating with the main screw 15 and accomplish the same results.

It is believed that the operation and many advantages of the invention will be understood without further description.

Having thus described my invention, I claim:

1. In a lifting jack including a casing, a

vertically movable standard, and a rotatable member within the casing for moving said standard; a cylindrical plate rotatable with said member; shoes on opposite sides of said plate; and means supported by said casing for forcing said shoes into frictional contact with the periphery of said plate and preventing its rotation under normal conditions.

2. In a lifting jack including a standard and a rotatable steep pitch screw for raising said standard enclosed within'a casing; a gear 7 rotatable with said screw; a cylindrical member in frictional engagement with said gear i and adapted to rotate therewith; and yielding means supported by said casing and in frictional contact with the periphery of said member.

3. In a lifting jack including a standard and a rotatable steep pitch screw for raising said standard enclosed within a casing; a gear rotatable with said screw; a cylindrical member in frictional engagement with said gear and adapted to rotate therewith; yielding means supported by said casing on opposite sides of said member and in frictional contact therewith; and means for varying said frictional contact.

4. In a lifting jack including a standard and a rotatable steep pitch screw for raising said standard enclosed within a casing, said casing having oppositely disposed cylindrical recesses with parallel inwardly extending flanges; a gear rotatable with said screw; a cylindrical member in frictional engagement with said gear and adapted to rotate therewith; and yielding means supported in said recesses and including shoes disposed between I said flanges and having curved faces in frica driving gear ke ed thereto; a bearing plateupon which saic gear rests; and yielding means within and supported by said casing consisting in part of a shoe in frictional contact with the periphery of said bearing plate.

6. In a lifting jack including a standard, a rotatable steep pitch screw for raising said standard enclosed within a casing and having a driving gear keyed thereto; a bearing plate upon which said gear rests; shoes on opposite sides of said plate; and yielding means in recesses formed in said casing adapted to force said shoes into frictional contact with the periphery of said plate.

7 In a lifting jack, a casing containing an elevating and lowering mechanism consisting in part of a rotatable cylindrical member; and yieldingmeans supported disposed between inwardly extending flanges on said casing and having elongated curved surfaces in frictional contact with the member.

8. In a. lifting jack, a casing containing means for elevating and lowering a load supporting standard, consisting in part of a rotatable gear; a cylindrical plate in'frictional engagement with said gear and normally rotatable therewith; a device within said casing in frictional engagement with said plate, the degree of friction being less between said device andplate than between said plate and gear; and means for; manually rotating said gear and overcoming the friction between said vice from said plate.

9. Inalifting jack, a casing containing periphery of said means for elevating and lowering a load supporting standard, consisting in part of a rotatable gear; a plate in frictional engagement With the lower side of said gear, said frictional engagement being increased When said standard is supporting a load; a device supported by said casing coacting with the periphery of said plate and creating a friction thereon sufficient to prevent normal rotation of said gear; and manually actuated means for rotating said gear and overcoming the friction created by said device Without disenga ing said device from said plate.

igned by me at Harvey, Illinois, this 3rd day of January, 1928.

FRANK L. GORMLEY.

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