US2708528A - Spring mechanisms for brick stack lifting forks - Google Patents

Description

y 1955 v. H. CARTWRIGHT ,708,528

SPRING MECHANISMS FOR BRICK STACK LIFTING FORKS Filed NOV. 20, 1952 5 Sheets-Sheet 1 F I G. I. 7 F l G. 2.

y 2 n w J7 39' Z{ g j 4 a @54 7? 6 27 fi ,3 Z5 j:/5 3 0 7 7 INVEN TOR. VICTOR H. GARTWRIGHT May 17, 1955 v. H. CARTWRIGHT 2,708,528

SPRING MECHANISMS FOR BRICK STACK LIFTING FORKS Filed Nov. 20, 1952 3 Sheets-Sheet 2 2,708,528 SPRING MECHANISMS FOR BRICK STACK LIFTING FORKS Filed Nov. 20, 1952 May 17, 1955 v. H. CARTWRIGHT 3 Shee'ts-Sheet 3 INVENTOR. VIGTQR H. GARTWRIGHT BY 6/ 28 War/4 ArraeA/Eys SPRING MECHANISMS FOR BRICK STACK LIFTING FORKS Victor H. Cartwright, Peoria, Ill. Application November 20, 1952, Serial No. 321,623 6 Claims. (Cl. 214-655) In said patent the tines or arms are provided with gripping or clamping means, operated by the relative vertical movement of the two frames, which are connected by a compensating spring, such clamping means being arranged to grip the lower or finger courses of a stack of bricks or other articles disposed between the tines or arms, and thus lift these finger courses, as well,

as the rest of the stack, superposed on such courses above the arms, without the necessity of using a pallet to support the stack.

The present application is a companion case to my prior co-pending application Ser. No. 314,191; filed October 10, 1952, and now Patent No. 2,684,772.

In said prior application there was disclosed, but not claimed, an improved compensating or lifting spring atrangement, interposed between the two frames, and this improved spring arrangement forms the subject of the present application. Similarly, there are many features illustrated and described in the present application which were fully claimed in the said prior application, but which form no part of the present invention and are not claimed herein.

The principal object of the present invention is to devise an improved construction so designed that relatively light loads will extend the springs sufiiciently to permit the minimum amount of relative movement between the two frames necessary to insure the proper operation of the gripping means.

To this end, I provide mechanism whereby, as the rear frame is lifted, the point of attachment of the springs to the front frame shifts, so that the leverage or mechanical advantage of the load on the springs is increased, and the extension of the springs is reduced accordingly. That is to say, the springs are extended less than the minimum distance which the rear frame is required to move.

In order that the invention may be readily understood. reference is had to the accompanying drawings, forming part of this specification, in which:

Fig. 1 is an end elevation of my improved lifting fork, parts being broken away;

Fig. 2 is a vertical transverse section, showing the two frames in a relative position different from that of Fig. 1;

Fig. 3 is a rear elevation of the device, looking toward the left side of Fig. l, with springs shown in no load position;

Fig. 4 is a fragmentary perspective view of the lower portion of my improved spring mechanism, showing how it is connected with the two frames; and

Figs. 5 and 6 are fragmentary side elevations, on an enlarged scale, showing such mechanism in two different positions.

Referring to the drawings in detail, my improved fork comprises a rear frame adapted to be attached to the lifting truck, and a front frame carrying the tines or arms, as in said patent. The rear frame is made up of a pair of spaced vertical members 1 connected by horizontal members 3, 4 and 5. A pair of perforated brackets 6 are secured by bolts '7 to the'vertical members brackets constituting the means by which the rearframe is attached to the fork truck; (these brackets correspond with the brackets 34 in said patent). I

The front frame comprises a pair of spaced 'vertical members 2 connected at their upper ends by a horizontal member 13, and at their lower ends by a heavy beam 14. The members '2 are preferably braced to the beam 14 by triangular gusset plates 2 as shown in Figs.

and 4.

The two frames are connected for relative vertical movement by means of a pair of rollers 8 carried by brackets 9 secured to the vertical members 2 and adapted to engage the outside of the vertical members 1, and a pair of rollers 10 mounted in brackets 11 secured to the lower ends of the members 2 and adapted to bear against the inner faces of the vertical members 1.

A pair of brackets 12 is also secured to the vertical members 2 near their lower ends and have their free ends bent around the members 1, as shown in Fig. 1, so as to hold such members in contact with'the rollers 10.

A track member 15 is mounted on and extends parallel with the beam 14, being spaced therefrom by a strip 16.

A plurality of vertical plates 17, 17 17 and 17 bear against the front face of the track member 15 and each is provided at its upper end with a roller 19 carried by a bracket 20, which roller engages behind the track member 15 in the space between such track member and the beam 14, as clearly shown in Figs. 1 and 2.

Also secured to each plate 17, 17, etc. near itslower end is a'roller 21 carried by a bracket 22, which roller bears against the front face of the beam 14. Thus, each of these plates is free to traverse the track member 15 and beam 14 and to move laterally relative thereto.

The plates 17, 17, etc. carry the tines or arms 18, as I clearly shown in Fig. 1. Each of these arms is equipped with gripping means 18', as indicated in dotted lines in. Fig. 1, such gripping means being constructed and. opera To the outer end of the lever 24 is pivotally connectedthe lower end of a link 27, the upper end of which is" rigidly secured to a cylindrical block 28. I All of these cylindrical blocks associated with eac of the arms 18, are enclosed within and slide freely through a tubular member 29, having an open slot at its lower side to accommodate the links 27. This tubular member 29 is welded or otherwise secured to an angle member 30 extending along the rear frame and securedto the vertical members 1 thereof.

It will be seen that the above described blocks and tubular member constitute a slidable connection between each of the operating rods or links 27 and the frame members 1, this slidable connection permitting the free' Patented May 17, 1955 1 near their upper ends, these lateral movement of the arms and the operating mechanism associated therewith.

A guide plate 31 having a slot, through which the link 2.7 passes, is preferably provided, such plate being rigidly securedas by welding to the bracket 26.

Rigidly secured by suitable brackets to the top of the plates 17, 17 etc. are internally threaded blocks or nuts 32, which nuts engage screw threaded portions of a shaft 33. The portions of the shaft 33 adjacent one end are reversely threaded with respect to the portions adjacent the other end, so that, when said shaft is rotated, the respective nuts 32, and arms by which they are carried, move in opposite directions. This provides means for varying the spacing between the arms, as desired, as fully described and claimed in my said copending application S. N. 314,191, but which forms no part of the present invention.

Secured to the vertical members 2 by brackets 35, just above the shaft 33, is a channel member 36, in which freely slides a toothed rack 37. The channel member 36 has a slot extending longitudinally therethrough for part of its length and a bolt works freely through this slot and extends into the rack 37. This bolt also passes through a bracket 62 which lies snugly against the lower surface of the channel 36.

A pinion 40 is mounted on a shaft 41 and engages the rack 37. This pinion is turned by means of a sprocket wheel 42 on the shaft 41, which sprocket wheel is driven by a sprocket chain 43 extending up over a sprocket wheel 44 secured to a hollow shaft 45 mounted in a suitable framework at the top of the machine and pro vided at its free end with a hand wheel 46 by means of which it may be turned.

Another horizontal shaft 47 is journalled' in bearings 48 secured to the frame members 2 and is formed with a key or spline 49 extending along the same. A sprocket wheel 50 having a hub 5G provided with a keyway engaging the key 49 is slidably mounted on this shaft 47. A sprocket chain 51 extends around the sprocket wheel 50 and around a sprocket wheel 52 secured to the shaft 33. A forked bracket 53, rigidly secured to the rack 37, engages an, annular groove in the hub 50 of the sprocket 50, so that this sprocket is caused to move laterally with the rack 37.

A sprocket wheel 54 is carried by the end of the shaft 47 and a chain 55 extends around this sprocket wheel and a sprocket wheel 56 mounted on a shaft 57 journalled in suitable bearings at the top of the ma chine. This shaft 57 carries at its end a beveled gear which meshes with a similar gear carried at the end of a shaft which passes through the hollow shaft 45 and carries at its. other end a hand wheel 61 by means of which it may be turned.

The. bracket 62, above referred to, and clearly shown in Fig. 5, embraces the shaft 33 between spaced collars 63 fixed thereto. As above explained, this bracket is rigidly secured to the rack 37 so that when the rack 37 moves, the shaft 33 moves with it.

From the foregoing, it will be apparent that, when the rack 37 is moved longitudinally of the channel 36 .j

by turning the hand wheel 46, it carries with it both the sprocket 50 and the shaft 33. As the shaft moves longi tudinally, it carries with it the nuts 32, and the arms 18, so that the entire group of arms is shifted as a unit laterally of the frame, that is to say. to one side or the other of the center. This feature of shifting the arms laterally, as desired, is described in more detail and fully claimed in my said co-pending application, and forms no part of the present invention.

As described in my prior patent, and already mentioned in the present specification, the gripping or clamping means associated with the arms is operated by the vertical movement of the rear frame relative to the front frame. To permit this relative vertical movement of the frames and operation of the gripping means, I provide a Oil resilient connection between the two frames. As shown, this consists of a pair of rods 68 suspended from the frame member 3, carried by the rear frame, each such rod supporting, by means of a bracket 69, a set of springs 70, the lower end of these springs being connected by a bracket 69 to a member 71. The tension of these springs may be regulated by means of a nut 68 threaded on the upper end of the rod 68. The springs must be strong enough to sustain the. Weight of the front frame and hold the arms or prongs in normal or no load position.

Instead of anchoring the member 71 directly to the beam 14 of the front frame, as in my said patent, I provide the improved mechanism which constitutes the present invention. In this improved mechanism, the member 71 straddles a lever 73, pivoted to the rear frame member 1 at 74, by means of a block 74*, and carries at its lower end a roller or trolley 72 which engages the lower edge of the, lever 73, all as best shown in Fig. 4. The free end of this lever is connected by links 75, 75 with a pivot pin 76, carried by a stud 76 secured to the beam 14 of the. front frame.

When the arms of the fork are inserted under the- It will be understood, that there is a minimum distance i which the rear frame must move, relative to the front frame, to effect the proper operation of the clamping means for gripping the finger courses. If the load is. a heavy one, it serves to hold the arms down while the rear frame moves a sufiicient distance to actuate the gripping means, and the springs, if anchored directly to the front frame, as in my said patent, would stretch to the same extent. But, if the load is a lighter one, its weight would not be great enough to cause the springs to stretch sufliciently to permit the necessary minimum relative movement of the two frames. It is to enable a light load to satisfactorily operate the grippers that the present improvements have been devised.

Fig. 5 illustrates the position of the parts in their initial position, that is, in the position they occupy be.- fore the rear frame has been lifted. In this position the lever or lifting bar 73 is inclined upwardly from its pivot 74, and it will be particularly noted that the outside angle between the axis of the member 71 and the upper edge of the bar 73 is somewhat less than a right angle (see Fig. 3), so that the tension of the springs forces the member 71 toward the outer end of the bar 73 and against the link 75*.

As the rear frame member 1 is lifted by the truck, it moves the pivot 74 upwardly, toward the position shown in Fig. 6, and after it moves a predetermined distance and approaches such position the bar or lever 73 becomes inclined downwardly from such pivot. As soon as the inside angle between the member 71 and the upper edge of the bar 73 becomes less than the tension of the springs will force the member 71 to. travel inwardly along the bar until it engages the stop 73 thus shifting the point of attachment of the springs to the front frame laterally. In this position it will be seen that, although the springs are somewhat more extended than in Fig. 5, the extension is less than the distance through which the rear frame has moved, that is less than it would have been if the springs had re.- mained fixed at the outer end of the bar 73. Thus, my improved construction results in decreasing the stretch and hence the tension or pull of the springs below what of the front frame acts with a mechanical advantage on the springs, due to the leverage exerted by the bar 73, thus enabling a lighter load to stretch the springs sufficiently to allow a great enough relative movement of the two frames to operate the gripping means. The stop 73: may of course be placed at any desired point to give the necessary leverage, or with exceptionally light loads, may even be omitted entirely. In this case, when the rear frame moves upward, the member 71 will travel inwardly to the pivot 74, and the springs will exert practically no pull on the front frame. It will therefore remain temporarily stationary due to its own weight. After the rear frame has moved the necessary distance relative to the front frame, the cross member 5 thereof engages the ends of stop screws 77, carried by horizontal member 78, carried by the front frame, thus preventing further relative movement of the frames, and the arms then lift the load as herein above mentioned, and also as described in my said prior patent.

What I claim is:

1. In a lifting fork, the combination with a vertically movable lifting frame and a load carrying frame adjacent thereto, means whereby, after an initial movement of said lifting frame relative to said load carrying frame, the two frames move upwardly together, a plurality of horizontally extending, spaced arms supported by said load carrying frame, article clamping means mounted on said arms, means operated by the vertical movement of said lifting frame relative to the load carrying frame for actuating said clamping means, spring means connecting said frames and arranged to extend to permit the initial vertical movement of said lifting frame relative to the other, and means for in-- creasing the mechanical advantage of said load carrying frame on said spring means as said lifting frame moves upward, whereby a lighter load will extend said spring means enough to allow suflicient relative movement of said lifting frame to actuate said clamping means.

2. In a lifting fork, the combination with a vertically movable lifting frame and a load carrying frame associated therewith, a plurality of horizontally extending, spaced arms supported by said load carrying frame, article clamping means mounted on said arms, means operated by the vertical movement of said lifting frame relative to the other for actuating said clamping means, spring means connecting said frames, means for movably attaching said spring means to said load carrying frame, and means brought into operation by the movement of said lifting frame through a predetermined distance for automatically shifting the point of attach ment of said spring means laterally.

3. In a lifting fork, the combination with a vertically movable lifting frame and a load carrying frame associated therewith, a plurality of horizontally extending, spaced arms supported by said load carrying frame, article clamping means mounted on said arms, means operated by the vertical movement of said lifting frame relative to the other for actuating said clamping means, a substantially horizontal bar pivotally connected at one end to said lifting frame and connected through links at its other end with said load carrying frame, and generally vertical tension spring means connected at its upper end with said lifting frame and having at its other end a slidable connection with said bar.

4. In a lifting fork, the combination with a vertically movable lifting frame and a load carrying frame associated therewith, a plurality of horizontally extending, spaced arms supported by said load carrying frame, article clamping means mounted on said arms, means operated by the vertical movement of said lifting frame relative to the other for actuating said clamping means, a substantially horizontal bar pivotally connected at one end to said lifting frame and connected through links at its other end with said load carrying frame, and generally vertical tension spring means connected at its upper end with said lifting frame and having at its other end a trolley engaging under and capable of travelling along said bar.

5. In a lifting fork, the combination with a vertically movable lifting frame and a load carrying frame associated therewith, a plurality of horizontally extending, spaced arms supported by said load carrying frame, article clamping means mounted on said arms, means operated by the vertical movement of said lifting frame relative to the other for actuating said clamping means, a substantially horizontal bar pivotally connected at one end to said lifting frame and connected through link means at its other end with said load carrying frame, whereby, when said lifting frame moves upward a predetermined distance the angular relation of said bar relative to said lifting frame is changed from an outwardly and upwardly inclined position to an outwardly and downwardly inclined position, and generally vertical tension spring means connected at its upper end with said lifting frame and so connected at its lower end with said bar that it travels along the same toward its pivot when the inclination of said bar is thus changed.

6. In a lifting fork, the combination with a vertically movable lifting frame and a load carrying frame adjacent thereto, means whereby, after an initial movement of said lifting frame relative to said load carrying frame, the two frames move upwardly together, a plurality of horizontally extending, spaced arms supported by said load carrying frame, article clamping means mounted on said arms, means operated by a predetermined minimum vertical movement of said lifting frame relative to the other frame for actuating said clamping means, extensible spring means interposed between said frames to permit the initial relative vertical movement of said lifting frame, and means connecting said spring means to said load carrying frame in such manner that the total amount of extension of said spring means is substantially less than the said minimum relative vertical movement of said lifting frame, whereby a lighter load will extend said spring means enough to allow sufficient relative movement of said lifting frame to actuate said clamping means.

References Cited in the file of this patent UNITED STATES PATENTS 1,384,793 Weber et al. July 19, 1921 2,530,375 Cartwright Nov. 21, 1950 2,578,016 Rike Dec. 11, 1951 2,636,768 Hansen Apr. 28, 1953 2,684,772 Cartwright July 27, 1954 FOREIGN PATENTS 276,951 Great Britain Jan. 5, 1928

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