US1528236A - Lifting jack - Google Patents

Description

Mar. 3, 1925.

1,528,236 W. G. ARMSTRONG LIFTING JACK Filed March 2, 1.922 2 sheets shefi 19 F-W57 'INVENTOR.

HALTER AEMSTPON ATTORNEY.

w. s. ARMSTRONG Mir.

LIFTING JACK I Filed March 2, 1922 2 Sheets-Sheet 2 ATTORNEY.

*INVENTOR.

Nurse 6. Aensr ouq.

Patented Mar. 3, 1925.

UNITED STATES PATENT OFFICE.

WALTER G. ARMSTRONG, OF BRIDGEPORT, CONNECTICUT, ASSIGNO'R TO THE AMERI- CAN TUBE & STAMPING COMPANY, OF BRIDGEPORT, CONNECTICUT, A CORPORA- TION OF CONNECTICUT.

LIFTING JACK.

Application fi1ed.March 2, 1922. Serial No. 540,494}

To all whom it may concern: 1

Be it known that I, WAIJ1ER G. ARM- STRONG, a citizen of the United States, residing at Bridgeport, Connecticut, have invented certain new and useful Improve type and the leading object of my present invention isto improve upon the constructions of said applications by simplifying the construction of the jack and reducing the number of parts. A further object of my invention is to provide a better and more effective spring action for actuating the pawls. 7

Further objects, and objects relating to details and economies of operation and con struction, will definitely appear from the detailed description to follow. plish the objects of my invention, in one instance, by the devices and means described in the following specification. My invention is clearly defined and pointed out in the appended claims. A structure constituting a preferred embodiment of my invention is illustrated in the accompanying drawings, forming a part of this speclfication, in

which Fig. l is a side elevation of my improved jack, the operating mechanism being shown in dotted lines.

Fig. 2 is a sectional view on anenlarged scale through the upper part of the jack, showing the spring set for lowering movement.

Fig. 3 is a perspective view of one of the pressed metal pawls used in this jack, and

Fig. 4 is a sectional view similar to Fig. 2 of a modified construction, showing the spring set for raising.

I accom In the drawings, the same reference numerals refer to the same parts throughout the several views.

The form of lifting jack disclosed in my pending applications, comprises a casing, a rack 's-lidably mounted in the casing, an operating lever pivoted in the casing, and a pair of pawls adapted to engage the teeth of the rack. One of these pawls, the lifting pawl, is pivoted on the inner end of the operating lever and the other, the holding pawl is pivoted on a pivot fixed in the casing. A spring is provided, the ends of which extend through perforations iii the back walls of the pawls and the action of the jack is reversed by shifting the center of the spring from one side to the other of a straight line connecting said perforations. When the center of the spring is nearer the rack than the ends of the spring, said ends yieldingly force the pawls into engagement with the rack and the parts are in raising position. 'When the center of the spring is further from the rack than the ends, said ends tend to withdraw the pawls and the parts are in position for lowering movement. In said construction, the shifting of the spring is effected bya pivoted reversing lever and a link connecting a central part of the spring with said reversing lever.

My present invention consists in eliminating the link and using a specially formed spring, the central portions of which extend rearwardly and connect directly to the reversing lever. One important feature of my present invention consists in a special, double-armed spring connected directly to the reversing lever. Each arm of the spring may be of right-angled formation so that'the portions which take the place of the link, used in my prior constructions, are a part of the spring arms and the effective length of the spring arms is correspondingly increased.

lower end of the casing are welded to the base plate, 13. I provide a pair of sideplates, 14, which are welded to the sides of casing, 10, and which have the feet, 16, welded to the base-plate. These side-plates may be pressed inwardly, at '15,. to lie agaji'n'stthe 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 collar, 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 parallel, spaced side walls, 23, connectedby a front wall, 24;, the latter having a slot, 25, formed centrally therein. A tongue, 26, is struck laterally from the rear edge of one side wall and forms a sort of bridge extending beween the rear edges of the side walls, 23, and keeping them spaced correctly. This ear, 26, is perforated, at 27, to provide a bearing for one end of the spring. Cain 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 casing has a cam surface, 43,- which cooperates with the back of the lifting pawl, as will be more fully set forth hereinafter.

A wire spring of special double-armed form is provided for actuating the pawls. Each arm of this spring is of substantially right angle form, as shown in Fig. 2, consisting of the rearwardly extending portion, 35, and the vertically extending free end, 36. The central portion of the sprin at the rear ends of the portions, 35, is bent to form the loop, 37, which engages the pin, 38, on the reversing lever, 39. The free ends of the springextend through the perforations, 27,01? the lifting and retaining pawls, respectively, and bear against the ears, 26, at said points. The reversing lever, 39, is. U- shaped and has one leg extending into the casing and pivotally connected with the rear end of the spring by the loop, 37, and the other leg extending along the outside of the casing and terminating in the finger grip,

41. The reversing lever is pivoted on the casing on the pin, 40. The outer leg of the reversing lever engages the stop lug, 4L2, pressed out fromthe 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. In this modified construction, the spring, 44, has its central portion bent or twisted to form a rearwardly extending shank, a5, having an eye, 416, which receives the pin, 38, by which the shank, 45, is pivotally connected .to the inner leg of the reversing lever, 39. The free ends of the spring, 4L work in the perforations, 27, of the pawls, just as in the form previously described.

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 shownin the lifting position 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. adjacent ends of the vertically extending portions, 36, of the spring are nearer the rack than the ends engaging the pawls and such free ends, 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 hen the handle, 31, is raised, the rack is held fron'i-dropping by the retaining pawl, while the lifting pawl moves down, riding over a tooth of the rack and springing into engagement with the next lower tooth. This operation is repeated at each stroke of the handle. hen it is wished to lower the load, the reversing lever, 39, is shifted to the position shown in Fig. 2. This shifts the spring so that the adjacent ends of the vertically extending portions, 36, of the spring are further from the rack ,tnan the free endsof such portions and, consequently, the spring tends to move the pawls away from the rack. This tendency is ineffective as long as there is a load on the pawl. In Fig. 2, the handle is lowered and the spring arm 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 said pawl. Toward the end of the upstroke ofthe handle, the lower end of the lifting pawl engages the cam surfaces, 28, on the back of the retaining pawl and forces the latter into engagement with the rack, so that. the downward movement of the rack is halted and the load is shifted from the lifting pawl to the retaining pawl. Vhen this takes place, the spring HlIiVllJll: draws the lifting pawl from engagement with the rack. Now, the handle, 31, is de pressed and 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, 43, of the easing 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 the spring arm withdraws the latter from engagement with the rack. This operation is repeated at each stroke of the handle. The operation of the modified con struction shown in Fig. 4 is the same.

The improved construction disclosed herein results in a simplification of the jack since the spring is connected directly to the reversing lever and no link is used as in my prior constructions. Furthermore, the spring is anchored at the loop, 37, and both the rearwardly extending portion, 35, and the vertically extending portion, 36, constitute a part of the spring arm, so that I have a longer spring arm and, consequently, a better and more effective spring action. It will be noted that the portions, 35, flex with respect to each other with a scissors-like action, when the spring is in action and that the entire spring arm from the loop, 37, to the free end of the spring flexes under pressure. The form shown in Fig. 4 results in a simplification of construction by eliminating the link but the spring arm is not so long and the spring is not so effective as the preferred form.

I am aware that the construction de scribed herein may be altered considerably without departing from the spirit of my in vention and, therefore, I claim my invention broadly, as indicated by the appended claims.

Having thus described my invention, what I claim as new and useful and desire to secure by Letters Patent is 1. i1 device of the class described comprising a casing, a rack slidably mounted therein, an operating lever pivoted on said casing, a lifting pawl carried by said lever and engaging said rack, a retaining pawl pivoted on said casing and engaging said rack, a spring having its ends engaging said pawls and its central portion extending rearwardly, and a reversing lever directly connected to said rearwardly extending central portion.

2. A device of the class described comprising a casing, a rack slidably mounted there in, an operating lever pivoted on said casing, a lifting pawl carried by said lever and engaging said rack, a retaining pawl pivoted on said casing and engaging said rack, a spring having its ends engaging said pawls and its central portion formed into a loop, and a reversing lever pivoted on the casing and having a pin engaging in said loop.

3. A device of the class described comprising a casing, a rack slidably mounted therein, an operating lever pivoted on said casing, a lifting pawl carried by said lever and engaging said rack, a retaining pawl pivoted on said casing and engaging said rack, a spring havinga central loop and a pair of spring arms extending first forwardly and then vertically from said loop with the free ends of said arms engaging said pawls, and areversing lever pivotally connected to said central loop.

a. A device of the class described comprising a casing, a rack slidably mounted therein, an operating lever pivoted on said casing, a lifting pawl carried by said lever and engaging said rack, a retaining pawl pivoted on said casing and engaging said rack, a spring having a pair of angular spring arms the free ends of which engage said pawls, and a reversing lever connected directly to said spring at the junction of said arms.

5. A device of the class described comprising a casing, a rack slidably mounted therein, an operating lever pivoted on said casing, a lifting pawl carried by said lever and engaging said rack, a retaining pawl pivoted on said casing and engaging said rack, a spring having a central loop and a pair of right-angled spring arms each extending forwardly from said loop and thence vertically, and a reversing lever pivotally connected to said central loop.

6. A device of the class described comprising a casing, a rack slidably mounted there in, an operating lever pivoted on said casing, a lifting pawl carried by said lever and engaging said rack, a retaining pawl pivoted on said casing and enga 'ing said rack, a spring having a pair of right-angled spring arms each including a horizontal and a vertical portion, the outer ends of said vertical portions engaging said pawls and said arms crossing each other adjacent theinner ends of said vertical portions, and a reversing lever connected to the rear ends of the horizontal portions of said spring arms.

7. A device of the class described comprising a casing, a load-lifting member movable therein, an operating lever pivoted on said casing, a lifting pawl carried by said lever and engaging said member, a retaining pawl pivoted on said casing and engaging said member, a spring having a pair of angular spring arms the free ends of which engage said pawls, and a reversing lever directly connected to said spring arms.

8. A device of the class described comprising a casing, a rack slidably mounted therein, an operating lever pivoted on the casing, a lifting pawl carried by the lever and engaging the rack, a retaining pawl pivoted on said casing and engaging said rack, a spring having its ends engaging said pawls and its central portion formed into a shank extending laterally from the portions of the spring which engage the paw ls, and a revel-sing lever pivotally connected to said shank.

9. A device of the class described comprising a casing, a rack slidably mounted therein, an operating lever pivoted 0n the casing, a lifting pawl carried by said lever and engaging said rack, a retaining pawl pivoted on said casing and engaging said rack, a

spring having its ends engaging said paw-ls and its central portion twisted to form a rearwardly extending shank, and a reversing level' directly connected to the rear end of said shank.

In testimony whereof, I affix my signature.

WALTER G. ARMSTRONG.

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