US2425421A - Automatic grab - Google Patents

Description

Aun 12, v1947. A. T. DEILY AUTOMATIC GRAB Filed Nov. 4, 1944 2 Sheets-sneet 1 A. T. DEILY AUTOMATIC' GRAB Aug. 12, 1947.

2 Sheets-Sheet 2 Filed NOV. 4, 1944 afa :ma -Tui r wm,

l @fron/ver Patented Aug. 12, 1947 AUTOMATIC GRAB Arthur T. Deily, Pittsburgh, Pa., assignor to Aluminum Company of America, Pittsburgh, Pa., a corporation of Pennsylvania Application November 4, 1944, Serial No. 561,949

3 Claims.

This invention relates to lifting device of the grab or tong type such as is used for engaging and moving or otherwise handling articles of ani7 configuration but particularly those which are roughly square or oblong in configuration such as trays, baskets, racks, pieces of timber, large metal ingot and the like.

The object of the invention is to provide a lifting device which may be moved from one place to another by means of a crane or hoist and which is more or less automatic in the sense that it will, under proper manipulation, engage and disengage the article to be lifted without manual help.

The attached drawings illustrate in several views a lifting device embodying the principles of the invention, said views being as follows:

Fig. 1 is a top view;

Fig. 2 is a view in side elevation;

Fig. 3 a cross sectional view taken on the line 3-3 of Fig. 1 in the direction indicated by the arrows;

Fig. 4 a top view taken on theline 4 4 of Fig. 3 in the direction indicated by the arrows; and

Fig. 5 a cross sectional view taken at the line 5--5 of Fig, 2 in the direction indicated by the arrows.

Referring to these drawings, in which like numerals designate like parts, the lifting device or grab consists of three main parts: a suitable supn porting frame I, which is preferably square or rectangular in plan and which is adapted to carry all of the cooperating parts of the lifting device, and two side frames which depend from the supporting frame I and are pivoted to said frame i for swinging motion. Each of the side frames forms, in total, a work engaging or tong or grab arm and consists of a plurality of spacedmembers 2 which are pivotally connected to the frame I and which at their other end are joined together by achannel frame member 3 which not only joins themembers 2 into a unit to form the side frame or arm but likewise forms a ledge adapted to support the object grasped by the arms as they are swung into register with said object. In order that themembers 2, and therefore the arm of which they are a part, may swing freely, each such member is provided with an inwardly projectingend piece 4 adapted to be mounted, as shown, on shafts 5 and keyed to said shafts. Shafts y5 are mounted -on the top of the frame I and are there suitably supported inbearings 6. The members .2 which lie at the extremities of each side arm are provided with an upward extension 1, which in turn bears abolt 8 on which is mounted thecross piece 9. Springs I3 are provided at the top of the frame I at each end thereof and one endof each spring is Xedly attached to uprights II carried in the center of said frame I, the other end of the springs being attached to thecross pieces 9. Springs IB are tensioned as by adjustment of thecross-pieces 9 on thebolts 8 so that they tend to pull the crosspieces toward the lcenter of the frame I and thus swing the side arms outwardly.

The device thus described is adapted to be lifted by a hoist or crane which attaches (at two longitudinally spaced points in the specific device shown) to the ring I2, which ring in turn is linked to the swinging arms of the lifting device by the flexible chains I3. It will be apparent that either a single or multiple point suspension may be used and that in a lifting device of the type illustrated in the drawings a balanced two-point suspension is to be preferred. Regardless of the number of points of suspension, the ring I2 and flexible chains I3 are located above and attached to one end of theend pieces 4 ofopposite members 2, and at the place where these points of suspension are located theend piece 4 is so shaped as to form a lever or crank whereby force applied upwardly through ring I2 and chains I3 will tend to rotate themembers 2 on the shafts 5 and thus close the side arms against the action of springs I.

Thus it will be observed that if the lifting device rests, for instance, on the floor with one of its side arms on either side of the object to be lifted, said side arms will be swung into the outward position indicated by the dotted line in Fig. 3 and lwill be maintained in this position by the normal force of the springs ill, which tend to rotate themembers 2 outwardly. If, however, force is applied through ring I2 tending to raise the lifting device upwardly, that force, if not otherwise opposed, will tend to rotate the side arms inwardly to the full line position' shown in Fig. 3, whereupon the tray I5 or other article which lies between those arms will be grasped by those arms and seated thereon in the manner shown at Fig. 3. Further lifting force applied through the ring by the hoist or crane to which they are attached will maintain the side arms in a work grasping position while the article or tray is moved from one spot to another, but when the lifting device and its contained tray is again placed on a floor and tension from the hoist is eliminated and chains I3 are loosened, the normal action of the springs Il) will automatically disengage the side arms from the tray and return them to the position indicated in dotted line at Fig. 3. In orderthat the varied positions of the side arms, which are automatically assumed under the conditions above outlined, may be maintained at proper intervals, there is associated with at least one set ofcorresponding members 2 of each side arm a ratchet mechanism, which is best shown at Figs. 3 and 4. This ratchet mechanism comprisesra star wheel I keyed to a shaft I'I, which shaft is Vjournaled in bearings I3 carried by transverse members of the supporting frame I. Said star wheel bears projections I9, equally spaced circumferentially, and a like number of recesses 2i! between said projections. Pivotally connected to theopposed members 2 are the plunger rods 2i, which are positioned in space by means of apertures in thecross members 29 and the frame I, through which apertures the plunger rods pass. If desired, each rod may carry at its inner end anadjustable nose piece 22 for such length adjustments as are necessary. Therods 2! are so aligned that their inner ends Vare adapted to register with either the projections i or the recesses 2li of the star Wheel IS, depending upon the position of the star wheel at any given moment. The star wheel I6 is rotated to bring its projections or recesses into or out of register with the ends of the plunger rods 2l by means vof the ratchet wheel 23 which is keyed to a hub extensionv of said star wheel. Pawl 2li is mounted Yto prevent rotaton of ratchet wheel .23 in one direction. Movement in the other direction of the ratchet wheel is imparted bylever 25 mounted on shaft l'l which lever is adapted to be raised by means of theflexible connection 26 between the lever and lifting ring I2. Thelever 25 carries a spring pressedpawl 2 vwhich is so mounted on said lever that lifting of the lever brings the ,pawl 2? into position to engage a tooth on the ratchet wheel.Spring 28 is mounted to constantly pulllever 25 downwardly so that when the lifting device is placed upon la floor or support and the -exible chains I3 and thelever operating chain 26 become slack thespring 28 operates thelever 25 pulling the lever and its attached pawl 2l downwardly, thereby indexing the ratchet star wheel i .to the next position.

The lifting device as illustrated in the drawings has been particularly designed for .the lifting of .stacked trays such as those shown at I5 and therefore includes refinements not necessary to the operation of kthe device in its broader applications but particulariyuseful in that specific application. Included among such reiinements are means for insuring that, when the lifting `device l'is placed over the stacked trays and its .side arms closed, the arms as they are swinging together will register with the spaces sii provided in the tray for the entry ofthe arm ends (see Figs. 3 and 5'). Referring to Figs. 2 and 5, this means consists of stop arms 3l pivoted at their upper ends inextensions 32 vof the frame i and adapted to be swung inwardly so that their ends contact -the top of the stacked tray I5 and prevent the lifting device from being lowered vbeyond a pre- .determined point. To hold said stop arms .3i in vtheir inwardly swung .positionremovable pins 2,3 are suitably provided at a proper point in thelframe extensions 32. Another refinement are the wheels ,34 mounted for free turning movement on shafts at the bottom of Aeachmember 2 of `each side arm. These wheelsmerely provide ro- ,tating guideswhen the lifting .device'bearing the 4 trays is lowered between conning walls such as the walls of an immersion tank.

The operation of the specic device will now be described. Assuming that the crane operator desires to lift a set of stacked trays I5 and that the lifting device is resting on the floor with its side arms opened outwardly by the normal force of the springs l0, the rrst step of the operator is to set the star wheel I6 so that its projections I9 are in register with ends 22'ofplunger rod 2 If. So positioned the star wheel I6 will prevent the side arms from closing as the lifting device is raised from the floor by the crane and lowered over the trays I5 because, although the force exerted by the lifting movement through the Y chains I3 would tend to pull the side arms inwardly against the action of the springs I0, the side arms are held in their outward position by the plunger rods 2l and thepawl 24 operates to hold the ratchet wheel 23 stationary. However when the lifting device is lowered by the operator over the stacked trays and comes to rest thereon as stop arms 3l contact the top of the upper tray (as shown'in Fig. 5) and the chainsV I3 and 2e again become slack the spring 28'pullslever 25 and its spring actuatedpawl 21 downward thus moving ratchet wheel 23 and indexing star wheel iE so that recesses 20 register withend 22 of the plunger rods. Therefore, the crane operator by taking up the slack of chains I3, and thereby beginning the raising of the lifting device, immediately pulls the side arms inwardly into contact with the stacked trays (as shown in Fig. 3) the plunger arms 2 I allowing this movement by pressing into therecesses 20 of the star wheel I6, and the trays may be lifted Ato another spot. When the trays are to be released the crane operator merely lowers the lifting device to the iloor whereupon the slackening of thechainV 26 againallows the spring 23 to function indexing the star wheel I5 to where its projections I9 again prevent closing of the side arms as the lifting device is raised from its position around said trays.

Having thus described my invention, I claim:

1. in a lifting device, in combination, a frame, depending side arms pivotally mounted on said frame, means cooperating with said arms to normally and yieldingly force said arms out of lifting position, means for suspending the lifting device from the mechanism for lowering and raising said device, said suspension means being linked to said arms to normally .force the arms into lifting position during suspension, a ratchet mechanism, means cooperating with said ratchet to periodically prevent movement of said arms into lifting position and a link connecting the said ratchet mechanism and said suspension means and operable .by the suspension operation to cause timed movement of the ratchet 4mechanism with .respect thereto.

2. AIn a lifting device, in combination, a frame, depending sidey arms pivotallymounted on said frame, crank extensions Aon said arms to swing them toward each other into closed position when v,lifting force `is .applied Vto said extensions, spring means forswinging saidarms away from each other into open position when said lifting force is removed, suspension means connected to said extensions Aby which said vdevice is attachable to a raising and lowering mechanism@ `pawl and ratchet mechanism carried bysaid framean operating Vmember therefor, a spring for actuating said member inthe ratchet operating direction, vvmeans actuated by :said lratchet lmechanism to alternately ,permit and yprevent movement of said arms into closed position, and means connecting said suspension means and said operating member for moving said member against its said actuating spring upon application of lifting force to said suspension means, to condition said member for subsequently actuating said ratchet mechanism upon removal of the lifting force from said suspension means,

3. In a lifting device, in combination, a frame, depending side arms pivotally mounted on said frame, means cooperating with said arms to normally and yieldingly force the arms out of lifting position, suspension means adapted to suspend the lifting device during each cycle of raising and lowering said device and linked to said arms to normally force the arms into lifting position during suspension, an indexing mechanism adapted to prevent movement of said arms into lifting position during suspension in alternate cycles and means directly linking said indexing mechanism to said suspension means and operable under the application of raising force by said 6 suspension means to induce an indexing action at the completion of the raising and lowering cycle, whereby the indexing mechanism is positioned to prevent movement of they lifting arms into lifting position during alternate cycles.

ARTHUR T. DEILY.

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

UNITED STATES PATENTS

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