US2953269A - Lift fork for stacking articles - Google Patents

Description

Sept. 20, 1960 E. HALL ET AL 2,953,269

LIFT RoRR FOR sTAcxING ARTICLES 2 Sheets-Sheet 1 Filed Aprl ll, 1958 'ATTORNEYS Sept. 20, 1960 E. HALL ET AL 1.1m" FORK FOR sTAcKING ARTICLES 2 Sheets-Sheet 2 Filed April 1l, 1958 INVENT i taes LFT FORK FOR STACKING ARTICLES Filed Apr. 11, 1958, Ser. No. 727,909

4 Claims. (Cl. 214-653) The present invention relates to lift forks used f or lifting and transporting loads of articles, each load consisting of a multiplicity of articles such as filled cartons or boxes, stacked or arranged in a compact pile or group, and more particularly to improvements on a lift fork of the general type shown and described in Patent No. 2,530,375, issued to V. H. Cartwright. In this patent there is disclosed a lift fork comprising a pair of vertical parallel relatively movable frames, one of which is constructed to be attached topa lift fork truck or vehicle equipped with means for raising and lowering the frame, and the `other ofwhich carries horizontally extending tines adapted to engage theload. These tines are equipped with laterally operable and opposed gripper devices which `are expansible or retractable to grip articles at the lower courses of the load and lift them -together with the remaining upper portion of the load. The upper portion of the load is supported by the top surface ofv these tines, principally, and to some extent may receive some support from the gripped articles in the lower courses of the load.

The present invention, in the preferred form herein illustrated, provides an efiicient means for expanding and contracting the gripper means under the positive control of the lift fork operator so that the articles in the lower portion of the load, when lying between the tines of the fork, may be gripped for lifting independently of action of the lift fork on the upper portion of the load, this being one of the objects attained by the invention.

Another object of the invention is to provide 4a lift fork apparatus which will handle from one article to a full load of articles, thereby eliminating the prior practice of handling partial loads manually.

Another object of the invention is to provide independently controlled fluid actuated means for expanding and contracting the gripper devices carried by the tines, their gripping force being regulable, when gripping articles to lift them, not to exceed a gripping force that will cause damage to the articles.

Another object of the invention is -to provide a lift fork apparatus having the foregoing advantages that is easily and economically constructed and maintained.

Another object of the invention is to provide individual fluid-actuated motors that are remotely controlled for operation in unison for expanding and contracting the gripper devices on each of the tines for, at will, gripping and releasing articles put between the tines.

Other objects and advantages of the present invention will become apparent from a reading of the following description of a preferred embodiment, the appended claims, and the accompanying drawings of the preferred embodiment to which reference is made and in which:

Fig. 1 is a three-quarter front perspective view of the lift fork of the apparatus, a portion of a lift truck or vehicle appearing in phantom view.

Fig. 2 is a rear elevational view of the lift fork frame taken along line 2-2 of Fig. y1.

Fig. 3 is a partially diagrammatic view, showing the fluid system and controls for actuation of the iluid operating motors drivably connected to expand or contract one of the gripper devices.

Fig. 4 is a sectional view of the control valve of the system for manually controlling operation of the motors.

Referring to Fig. l, which illustrates the lift fork apparatus, the apparatus includes a supporting frame 10 which is movably attached to a lifting frame 11 mounted at the front of a truck or vehicle 12, said lifting frame being power operated for lifting and lowering the fork. The supporting frame 10 has a vertical wall frame 13 attached thereto and in spaced relationship. The vertical wall frame 13 has a plurality of 4tines 14 depending horizontally from the lower portion 13a of the wall frame. The tines 14 extend horizontally forward and are spaced apart in parallel relationship, one to the other, the spacings therebetween being substantially equal. Any desired number including at least two tines 14 may be built into the structure. The outermost or end tines 14 are provided with a single set of gripper bars 15, on their inside vertical faces and the intermediate tines between the end tines are provided with two sets of gripper bars 15 on both inside vertical faces. The gripper bars 15 are arranged to `oppose complementary gripper bars on the adjacent tine 14 and are movable laterally with `respect to the tines by expanding and retracting movement to engage an article placed between the tines. The gripper bars 15 rare mounted for movement similar to that disclosed in the Cartwright patent, No. 2,530,375, and are actuated in expanding and retracting movement by reciprocating movement of longitudinal linkage members 16 (Fig. 3) slidable within each tine 1-4.

As seen in Fig. 3, each Iof the longitudinal members 16 is pin connected to a pivotal crank 17 by pin 18, the crank 17 being pivoted on a bracket 19` integral at the back side of the lower portion 13a of the wall frame 13. This crank connection is provided ttor reciprocal action of each longitudinal member 16 in tines 14. Fluid-operated motors 21 -are provided to drive each member 16, the motors being in the form of cylinderpiston assemblies, which comprise a cylinder 22 with 0pposite end ports 23 and 24 for the admission of pressure lluid to move its internal piston in either direction. The piston (not shown) carries a connecting rod 25 having an end block 26 and is pivotally connected thereby at its outer end to the free end of the corresponding crank 17 by a pin 27 extending through one of the series of holes 28 in block 26. This lseries of holes 28 permits a stroke adjustment for each of the motors 21. As indicated on Fig. 2, the outermost motors may be of smaller size than the motors located inwardly therefrom, since these -outermost motors are required to drive but one set of the gripper bars 15 at the innerfacing on each of the outermost or end tines. The tines located intermediate these two end tines each have a double set of gripper bars facing in opposite `directions on their vertical facings, hence, the motor for driving them is preferably of a correspondingly larger size. In any event, each of the mot-ors 21 are lmounted similarly yand operate in the same manner and in unison, as will be presently described. Each cylinder 22 of the two outermost motors have an upper end lug 29 pin connected at pin 30` to bracket 31 projecting rearwardly on lower wall frame 13a. The centrally disposed motor 21 has a similar pin connection on crossbar 32 across the uprights of wall frame 13. Thus, the cylinders of the motors 21 are each held on the wall frame of the lift fork.

As seen from Figs. 2 and 3, each of the motors are connected into a pressure uid system for activating the motors in either direction. In this connection, the system herein illustrated is provided for operating doubleacting cylinder assemblies, however, it should be obvious that single-acting cylinder piston assemblies would operate just as well if, as will be seen from the following description of the system for double-acting cylinders, the movement of the motor for releasing the gripperdevices is powered by a spring biasing the power or positive stroke of the cylinder.

From Fig. 3, we see that a sump and pump unit 33 supplies a continuous source of uid under pressure into a conduit 34. Conduit 34 is connected in series with a conventional variable pressure regulator 35 that is adjustable for regulating the pressure of the iluid being supplied from the pump. At the outlet side of the pressure regulator is a conduit connection 36 to the inlet port 37 of a manually-operated control valve, referred to generally as 38. A pressure gauge 39 may be interposed in conduit 36 to'indicate a measurement of the pressure of the fluid that is being supp-lied by the pump through the pressure regulator 35. As may be seen from Fig. 4, with occasional cross-reference to Fig. 3, the control valve 38 has an axial shiftable valve spool 40 having three annular lands 4l, 42, and 43 thereon. The central shaft 44 of the valve spool 40 extends outwardly of the body of the Valve 38-and is sealed against leakage by a gland 45. The outer end of shaft 44 has a pivotal connection to the lower end of control lever 46 at a yoke 47 pinned through a bearing 44a on shaft 44. The lever 46 is mounted on a pivot 48 journaled on a bracket 49 which is part of the vehicle l2. Lever 46 is shiftable between the extreme settings- A (solid outline) and B (dotted outline) and is capable of being set in an intermediate position C. The pumpl and sump unit 33 is preferably mounted on the truck l2 of the lift fork apparatus and driven by power take-olf connection (not shown) from the vehicle l2. The control valve 38 and lever 46 may be conveniently mounted on the Vehicle l2 for ready access to these controls by the lift fork operator.

The control valve 38 'has ports 5.0 and 51 connected by uid conduits 52 and 53, respectively, which extend to respective connectionson a rst header 54 and a second header 55. These rst and second headers 54 and 55 are fastened transversely of the vertical uprights at the back of the wall frame i3. The first header 54-has Huid connections by conduits 56 to the upper port 23 of each of the cylinders 22 of the motors. The second header 55 has fluid connections by conduits 57 to the lower port 24v of each cylinder 22 of the motors. The Valve 38 also has upper exhaust ports 58 7and 59 connected, respectively, by iiuid connections at conduits 60 and 61 leading to the sump of the pump-sump unit 33.

Hence, as the control lever`46 is set in the position A (sho-wn in solid outline), fluid from the pump enters the valve 3S at port 37 and is conducted between lands 42 and 43 of the valve spool 40 to the port 5i and into the irst header 54 through conduit 53. The pressure fluid present in the rst header is then conducted through the three conduits 56 into the upper ports 23 of the three cylinders 22 of the motors forcing their pistons downwardly to extend the connecting rod 25. Fluid below the pistons is permitted to exhaust out ports 24, conduits S7 and iiow tol second header S5., thence through conduit 52, valve port Sti, exhaust port 55, conduit 66, and to the sump of pump-sump unit 33. This permits driving motionv by the motors to rotate the three cranks 17 counterclockwise about their pivots 20 to drive the longitudinal linkage members )i6 longitudinally into the tines and force the gripper bars i to expand against an article placed between the tines. By setting the pressure regulator 35 of this system to a fluid pressure corresponding to a driving force of the motor that is slightly. in excess of the force necessary to grip and lift articles engaged by the gripper bars will provide a satisfactory means for handling these articles without causing damage thereto by, excessive compressive forces upon gripping them, rJhe control lever 46 may also be set in its intermediate position C in which event the valve spool lands 41, 42, and 43, respectively, will block ports 53, 3'7, and 59 of the valve and lock the gripper bars on the tines in gripping engagement on the articles.

To release gripped articles, the control lever may be shifted to the indicated position B, in which event the valve spool 4t) will connect fluid pressure entering at inlet port 37 to port 50 and conduct uid pressure through conduit 52 to the second header S5. The pressure then in header S5 will be distributed through conduits 5'7; to enter the cylinders 22 of the three motors through their lower ports 24 `and actuate their pistons upwardly. Fluid above the pistons of cylinders 22 is exhausted through ports 23, conduits 56|, iirst header 54, conduit 53, port 5l, exhaust port 59, and conduit 61 to the sump. This movement will drive the crank 17 in a clockwise direction about theirV pins 20 and withdraw the longitudinal linkage member 16 in the tines 14 causing'the gripper bars 15 to retract and release the articles.

Various modications may be resorted to within the spirit and scope of the appended claims.

We claim:

1. In `a lift fork apparatus for carrying articles provided with a frame adapted tobe mounted for Vertical movement on a vehicle and including a plurality of parallel members attached to depend horizontally from said frame and'having equal spacing therebetween to receive articles, and opposed article gripper means movable on said members in cooperating relationship to act on articles received between said members when moved in one direction and to release the articles when moved in the other direction, in combination therewith, a longitudinally disposed linkage along each said member and operable by reciprocating movement to move said gripper means -inreither direction, a crank arm operatively connected to each said linkage and pivotally mounted on the frame, fluid-operated reciprocating motors for driving said linkages individually through pivotal connection of the connecting rod thereof on said crank arm, the cylinder of said motor being held on the frame, opposite end ports in the cylinder of each said motor, a rst fluid header, uid conduits connecting said iirst header to one end port of each said cylinder, a second fluid header, Huid conduits connecting said second headerto the. other. end port of each said cylinder, a fluid pressure source, a sump, a hand-operated control valve, fluid conduits connecting the control valve respectively to the source, first header, second header and the sump, said control valve being adapted for settings alternatively to: (l) connect the rst header andthe source and the second header and the sump and cause pressure iuid to actuate each of the motors to move their said linkage and gripper means in the direction to act on articles between said members, and (2) connect the second header and the source and the iirst header and the sump and cause pressure fluid to actuate each of the motors to move their linkage and gripper means in the direction to release said article.

2. The combination defined in claim 1, wherein the said control valve includes an alternative hold setting, said setting blocking the respective connections between both said first and second headers.` andthe pump and the sump, whereby the motors lock the article gripping means against movement in either direction.

3. The combination deiined in claim 1, characterized by including -a Variable pressure regulating meansin. the iluid conduit between the first header andthe source, thereby to permit regulation of the pressure actuating force of the motors in moving the gripper means in the direction to act on `a given kind of articles of' slightly more than the gripping force necessary to lift one ofsaid articles and prevent damage thereto upon gripping same.

4. The combination defined in claim 3, including, in .operative series connection in said fluid conduit with the 5 variable pressure regulating means, a pressure gauge in- 2,571,550 dioating the amount of ud pressure being delivered to 2,771,204 said rst header.

References Cited in the file of this patent 5 132 666 UNITED STATES PATENTS 2,530,375 Cartwright NOV. 21, 1950 6 Ehmann Oct. 16, 1951 McCormick Nov. 20, 1956 FOREIGN PATENTS Australia May 18, 1949

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