US1503343A - Lifting jack - Google Patents

Description

jug? 29 '1924. 1,503,343

w. G. ARMSTRONG LIFTING JACK Filed Sept. 23, 1921 2 Sheets-Sheet l "July 29 1924.

1,503,343 W. G. ARMSTRONG LIFTING JACK Filed Sept. 23, 1921 2 Sheets-Sheet 2.

Patented July 29, 1924i 1,503,343 CF'ICE.

WALTER Gr. ABIYISTRONG, F BRIDGEPORT, CONNECTICUT, ASSIGNOR TO THE AMERI- CAN TUBE AND STAlVII-'ING COMPANY, OF BRTDGEPORT, CONNECTICUT, A COR- PORATION OF CONNECTICUT.

LIFTING JACK.

the Severalyiewe pawl and I form cam surfaces on the rear edges of the side walls of the retaining pawl, which are engaged by the lower end of the lifting pawl, as it moves down, to force the retaining pawl toward the rack.

Another feature of my invention con` sists in the manner in which I secure the casing to the base. Laterally-extending feet on the lower end of the casing are rigidly secured to the base and there are also a pair of side plates which are rigidly secured to the sides of the casing and have flanges rigidly secured to the base.

Another feature of my invention consists in a simplified connection between the central part of the spring and the reversing lever. According to this feature, the central part of the spring is formed into a rearwardly-extending shank, which is directly connected, pivotally, to the reversing lever.

In Figs. l and 3, I have shown a ack construction embodying my improved pawl and my improved supportfor the casing. 'This construction includes the pressed metal casing, 10, which has a longitudinally-extending channel formed therein and the rearwardly-extending portions, r11, forming a housing for the operating mechanism. The lateral flanges, 12, at the lower end of the casing are welded to the base-plate, 13. I provide a pair of side-plates, 14, which are welded to the sides of casing, 10 and which have the feet, 16, welded to the base-plate.

' 'Ihese side-plates may be pressed inwardly,

at 15, to lie against the portions, 11, of the casing.

The channel-shaped rack, 17, is slidably mounted in the channel of the casing and has a plurality of teeth, 18, struck out from its base. A head, 19, is mounted on the upper end of said rack. A reinforcing col` lar, 20, is mounted on the upper end of the casing and has a tongue, 21, which extends within the channel of the rack and prevents dust and dirt from entering the interior of the casing.

A retaining pawl is pivoted in the casing on the pin, 22. Since the retaining and lifting pawls are identical, we shall use the same reference numerals in describing them. Each of these pawls comprises the parallei, spaced side walls, 23, connected by a front wall, 24, the latter having a slot, 25, formed centrally therein. IVherever, in this speciH lication and the claims, I refer to the front wall of either pawl, I mean that wall of the pawl which is nearest to the rack. A tongue, 2G, is struck laterally from the rear edge of one side wall and forms a sort or bridge extending between the rear edges of the side walls, 23, and keeping them spaced correctly. rI`his ear, 26, is perforated, at 27,

- to provide a bearing for one end of the spring. Cam surfaces, 28, are formed on the rear edges of the side walls for a purpose to be described hereinafter.

The operating lever, 29, has its rear end formed into a socket, 30, to receive the handle, 31. This lever is pivoted in the casing on the pin, 32, and the forward end, 33, of the lever, which extends into the casing, carries a pivot pin, 34, on which the lifting pawl is pivoted. The end, 33, of the lever extends between the side walls, 23, of the lifting pawl. The easing has a cam surface, 42, which cooperates with the back of the lifting pawl, as will be set forth more fully hereinafter.

A wire spring, 35, has its free ends extending through the perforations, 27, of the lifting and retaining pawls, respectively, and bearing against the ears, 26, at said points. The spring, 35, is provided with a central loop, 36, which is connected by a link, 37, with the reversing lever, 38. This lever, 38, is U-shaped and has one leg extending into the casing and pivotally connected with the rear end of link, 37, and the other leg extending along the outside of the casing and terminating in the finger grip, 40. The reversing lever is pivoted in the casing ony the pin, 39. The outer leg of the reversing lever engages the stop lug, 41, pressed out from the side wall of the portion, 11, of the casing.

The construction shown in Fig. 4 is identical with that just described, except for the formation of the spring and its connection with the reversing lever. In this modified construction, the spring, 43, has its central portion bent or twisted to form a rearwarally-extending shank, 44, having an eye, 45, which receives the pin, 46, by which the shank, 44, is pivotally connected to the inner leg of the reversing lever, 38. The free ends of spring, 43, work in the perforations, 27, of the pawls, just as in the form previously described. In this modification, link, 37, is eliminated, thus reducing the number of parts in the jack.

From the description of the parts given above, the operation of my improved lifting jack should be readily understood.

In Fig. 1, the parts are shown in the liftingposition so that, when the handle, 31, is worked up and down, the rack, 17 will be raised to lift the load engaged by head, 19. In this position, the center of spring` 35, is nearer the rack than the ends, and the ends ofthe spring, engaging the pawls at the perforations, 27, force the pawls toward the rack. As the handle, 31, is depressed, the lifting pawl is raised carrying the rack with it, while the retaining pawl rides over a tooth of the rack and snaps into engagement with the next lower tooth. When the handle, 31, is raised, the rack is held from dropping by the retaining pawl, while the lifting pawl moves down, riding over a tocth nffthe `rack land springing into Ae11- gagement with the next lower tooth. This operation is repeated at each stroke .of the handle. When it` is wished to lower the load, the :reversing lever, l38, :is shifted to the position-shown in Fig. 3. This-shifts the center of the spring, 3,5, so that it is further from the rack than the ends of the springs and, consequently, they tend to move the pawls-away from-the rack. rFhis tendency `is ineective as long as there isa loadon `the pawl. In Fig. 3, the handle is lowered and thespring 35, has withdrawn the retaining pawl from the rack. -As the handle, 31, is raised, the lifting pawl is lowered'and the load causes the rack to drop with saidpawl. Toward the end of the upstrolre of the handle, the lower end of the lifting pawl engages the cam surfaces, 28, O n-.the back ofthe retaining pawl and forces the latter inta-engagement with the rack, so that lthe fdownwardmovement of the rack is halted and theload is shifted from the lifting pawl to the retaining pawl. When this takes place, the spring, 35, withdraws the lifting pawl from engagement with the rack. Now, the handle, 31, is depressed land the lifting pawl, which is clear of the rack, moves upwardly. Toward the end of this movement, the back of the lifting pawl engages the cam surface, 42, of the casing and is forced by it into engagement with the rack so that, as its upward movement continues, it takes the load from the retaining pawl and spring, 35, withdraws the latter from engagement with the rack. This operation is repeated at each stroke of the handle. The operation of the modified construction shown in Fig. 4 is the same.

The improved pawl which I have disclosed is capable of supporting a very heavy load, because the front wall, 24, is almost exactly in line with the line in which the load is transmitted from the tooth of the rack to the pivot of the pawl. This load is applied longitudinally of the front wall and thus the full strength of the metal is utilized. This is true of both the lifting and retaining pawls. The slot, 25, in the case of theY lifting pawl, permits the central portion of spring, 35, to work through it. This results in a very compact structure. The ear, 26, not only provides a bearing for the end of spring, 35, but also insures correct spac- ,ing of the side walls, 23, so that they cannot move toward each other and bind on the inner end, 33, of the operating lever. The side plates, 14, give a very strong connection between the casing and the base, 13. As I have already indicated, the modified form of spring, 43, results in a simpler construction by eliminating link, 37.

I am aware that the construction described herein may be altered considerably without departing from the spirit of my invention and, 511,811.09, .I ,c.1aim :my invention broadlyeas indicated by the appended-claims.

Having thus described my,invention,`what I-claim as `'new-and desire to secure by Letters Patent is k:1. .A ldevice vof the class described comprising a casing, a lifting rack slidably mounted therein, a lever pivoted inI said, casing, anda vhollow lifting :pawl carried by said lever and engaging the teeth of said rack,-sai-d pawl -havinga front Vwall, side walls-and an ear projecting from one side wall toward the other and perforated to receive `an actuating spring. p

A2. A device of the classdescribed comprising a casing, a rack slidably mounted therein,an operating lever pivoted in said casing, a hollow :lifting pawl carried by said lever and engaging said rack, a hollow retainingA pawl pivoted in the casing and-engaging said rack, each of said pawls having a front wall, side walls and-a portion projecting from one side wall toward the other and provided with a hole, al spring having its endsextendingthroughsaid holes, and means forshifting the center of. saidN spring from one side to the other ofa straight line connecting said holes.V

3. A device of the class described compris ing a casing, a rack slidably mounted therein, an operating lever pivoted in said casing, a hollow lifting pawl carried by said lever and engaging said rack, a hollow retaining pawl pivoted in the casing and engaging said rack, each of said pawls having a front wall, side walls and a portion projecting from one side wall toward the other and provided with a hole, a spring provided with a central loop and having its free ends engaging in .said holes, and means engaginosaid central loop for shifting the centra portion of said spring.

4. A device of the class described comprising a casing, a rack slidably mounted therein, an operating lever pivoted in the casing, a hollow lifting pawl carried by said lever and engaging the rack, a hollow retaining pawl pivoted in the casing and engaging said rack, each of said pawls having a front wall, side walls and a portion projecting from one side wall toward the other and provided with a hole, a spring having its ends engaging in said holes, and a reversing lever pivoted on the casing and con? vnected to the central portion of the Spring.

5. A device of the class described comprising a casing, a rack slidably mounted therein, an operating lever pivoted in the casing, a hollow lifting pawl carried by the lever and engaging said rack, a hollow retaining pawl pivoted in the casing and engaging said rack, each of said pawls having a front wall, side walls and a portion projecting from one side wall toward the other and provided with a hole, the front wall of so i llO

the lifting pawl having a slot therein, a spring working in said slot and having its ends engaging in said holes, and a pivoted reversing lever' connected to the central portion of said spring. f

6. A device of the class described comprising a casing, a rack slidably mounted therein, an operating lever pivoted inthe casing, a hollow lifting pawl carried by said lever and engaging said rack, a hollow retaining pawl pivoted in the casing and engaging said rack, each of said pawls having a front wall, side walls and a portion projecting from one side wall and provided with a hole, the front wall of the lifting pawl having a slot therein, a spring having a central loop therein working in saidslot and having its ends engaging in said holes, a pvoted reversing lever,'and a link connecting said loop and the reversing lever.

T, In a lifting jack, in combination with a easing, a rack and an operating lever, a pressed metal pawl carried by said lever and comprising a front wall, spaced side walls and a portion projecting klaterally from the rear edge of one side wall toward the other side wall and provided with a hole.

8, In a liftingjack, in combination With a easing, a rack and an operating lever', a pressed metal pawl carried by said lever and comprising a 'front wall, spaced side walls and an ear struck laterally from the rear edge oi' one side wall and bridging the space between said side walls, said ear being provided with a hole.

9. In a lifting jack, in combination with a casing, a rack, and an operating lever, a pressed metal pawl carried by said lever and comprising a front wall, spaced side walls and an ear extending laterally from the rear edge of one side wall and perforated, said iront lwall having a central slot therein.

l0. In a lifting jack, in combination with a casing, a rack and an operating lever, a channelsshaped, pressed metal pawl carried by said lever with the base of the channel presented .toward the rack, said pawl having a perforated ear projecting laterally from the rear edge of one oi' the side walls thereof toward the other side wall, and a pavvl-actu-y ating spring engaging in said perforated ear.

In testimony whereof, I alflx my signature.

WALTER e. ARMSTRONG.

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