US3433376A - Combination facing for clamp device - Google Patents

Description

March 18, 1969 W. W. JORDAN COMBINATION FACING FOR CLAMP DEVICE Sheet of 2 Filed April 26, 1967 INVENTOR WAYNE W. JORDAN ATTORNEY March 18, 1969 w. w. JORDAN COMBINATION FACING FOR CLAMP DEVICE Sheet FIG. 4

FilECl April 26, 1967 INVENTOR WAYNE W. JORDAN 7/ 4 ATTORNEY United States Patent 3,433,376 COMBINATION FACING FOR CLAMP DEVICE Wayne W. Jordan, Battle Creek, Mich., assignor to Clark Equipment Company, a corporation of Michigan Filed Apr. 26, 1967, Ser. No. 633,968 US. Cl. 214-653 5 Claims Int. Cl. B66f 9/18; B66c 1/42 ABSTRACT OF THE DISCLOSURE A carton clamp especially for lift trucks having secured to the clamping surfaces two different facing materials of different thickness and yieldability so arranged that clamping pressure is more equally distributed over the sides of a cartonized load, and any tendency of the load to slip or to pivot out of the clamp is minimized.

Background of the invention The field of the invention relates to clamping apparatus, and includes a pair of oppositely disposed load-clamping plates which are actuated toward each other and against opposite sides of a load to enable the load to be lifted and transported.

One of the important considerations in the design of such clamping devices concerns the means for distributing substantially uniformly the clamping force on the sides of the load. Common types of loads handled by such devices are stored in cartons which may be damaged when non-uniform pressures are applied over a side. If relatively high pressure is exerted over certain areas the carton may be partially crushed; if, on the other hand, a relatively light pressure is exerted in certain areas the carton may slip or become dislodged from the clamp.

Heretofore, various types of constructions for loadclamping arms have been proposed. A clamp arm that is canted inwardly, and flexes outwardly into parallelism with the slides of a load when the same is clamped by the arm has been proposed. A load-clamping arm including an outer, primary arm which extends forwardly from the usual load carriage of a lift truck, and an inner, secondary arm which is joined to a forward Portion of the primary arm and extends forwardly and rearwardly therefrom and having a face plate mounted on the am structure through connections with the forward and rear portions of the secondary arm member has also been proposed. In this arrangement the primary and secondary arms both flex when clamping a load, and the flexure is utilized to distribute the clamping force. Again, clamp arms have been used having one or more facing materials of a uniform effective thickness secured thereto and coextensive with the area of the clamping surface for providing frictional contact between the sides of the load and the clamp arms.

Summary of the invention The present invention is an improvement of such prior devices. It effects a desirable distribution of clamping force over the sides of a load in a very simple manner, making unnecessary the use of special flexing arm designs, and the like, by securing over different and predetermined areas of each clamping surface facing materials having charactersistics which differ such that good distribution of clamping force is effected. It is therefore a principal object of my invention to distribute in a desirable manner over the sides of a load a clamping force by providing diflerent facing materials secured to the clamping surfaces in a predetermined manner.

3,433,376 Patented Mar. 18, 1969 Brie) description of the drawing FIGURE 1 is a front perspective view of a lift truck having associated therewith one form of a clamp attachment which embodies my invention;

FIGURE 2 is an enlarged partial view of the front lower corner portion of one of the clamp arms of FIG. 1;

FIGURE 3 is a sectional view taken along line 33 of FIG. 2; and

FIGURE 4 is a side perspective view showing another form of a lift truck clamp attachment for which my invention is especially well adapted.

Description of the preferred embodiments Referring now to FIGS. 1-3, the front masted portion of an industrial lift truck is shown generally at numeral 10. Front drive wheels 12 are connected by a drive axle, not shown, to the housing of which is mounted the front end of the truck chassis and a mast or upright assembly shown generally at numeral 14. Upright 14 includes a hydraulic lift cylinder 16 adapted to elevate in known manner nested telescopic rail sections and a carriage 18 (FIG. 4) supported thereby for vertical movement by chains 20.

Supported from the carriage is a clamp support and actuator 22 of known construction which comprises generally a pair of vertical side support members 24 to which are secured the ends of upper and lower pairs of clamp support cylinders 26, two of which have telescopic cylinder members 28 supporting left clamp arm 30, as viewed in FIG. 1, and the other two of which have telescopic cylinders 32 supporting right clamp arm 34. A pair of hydraulic actuator cylinders 36 are located centrally between the pairs of upper and lower support cylinders 26; one of the actuators has a piston rod 37 connected to left clamp arm 30 for actuating the .same laterally, and the other is similarly connected by a piston rod 37 to clamp arm 34. A plurality of staggered load support members 38 move laterally inwardly and outwardly during actuation of the clamp arms in interlocking relationship within and without central frame cover member 39, said members 38 functioning as a load back support to prevent damage to cartons and the like which are engaged by the clamp attachment.

The clamp arms, only the rear ends of which are shown at 30 and 34, extend forwardly along the outer sides of the pair of opposed clamp pads or platens 40 which are mounted approximately centrally thereof for slight pivotal movement about vertical pivot pins, not shown, connecting the clamp pads to the forward ends of the clamp arms. Each clamp pad or platen preferably comprises a one piece aluminum alloy plate which has the advantages of low weight and minimum thickness, thereby permitting the attachment to be used in areas of small clearance or spacing between load stacks. Heretofore such platens have had secured, as by bonding, over the inner clamping surfaces thereof a rubber-like facing material for providing a positive grip on loads. Thus, in using prior clamps of this general type a truck can approach a large cartonized load, for example, with clamp arm-s 30 and platens 40 extended, as in FIG. 1, to straddle the sides of the carton, after which actuator cylinders 36 are retracted to cause platens 40 to engage the sides of the carton with a clamping action. The frictional holding force of such clamping action has been aided heretofore by such single thickness rubber-like facing material or materials secured to the clamping surface of each platen.

The description up to now has been concerned primarily with known construction and features of carton clamps, and so constructional details beyond what is described above are not required. Further details of the clamp mechanism described above may be found, for

example, in assignees own Model B-5 Palletless Carton Clamp, as specified, for example, in Sales Sheet No. 1667 of assignee.

I have found in the use of such clamping devices as described above which utilize a single thickness resilient or rubber-like platen facing, that certain disadvantages inhere. The manner in which I have combined materials for facing the platens minimizes such disadvantages. In the embodiment of my invention shown in FIGS. 1-3, I utilize a relatively narrow strip of relatively thin, hard and cut-resistant rubber 44 having a rough top or a friction type surface which provides a relatively high degree of gripping ability. This material is preferably bonded to a thin strip of metal 46 which is in turn bonded to the inner surface of each platen 40 so as to extend longitudinally of and adjacent the bottom corner portion of each platen as shown in FIGS. 1-3. A suitable material for such use has been found to be Rough Top Arrnaplate, manufactured by Goodyear Tire and-Rubber Company. The entire remaining portion of the inner surface of each platen preferably has bonded thereto a sheet of relatively soft rubber facing 48 having a diamond-shaped raised rib pattern over the gripping surface thereof and substantially greater in thickness than the material illustrated at numeral 44. A suitable material having such characteristics and particularly well adapted for use in combination with said Armaplate for the purpose here intended is known as Wedge-Grip, also manufactured by Goodyear Tire and Rubber Company. Wedge-Grip material has a tough rubberized fabric backing which is adapted to be bonded to the surface of the platen. In practice, it has been found desirable also to secure the facing materials to the platens by means of countersunk bolts, not shown, in addition to securing the same by bonding.

In operation, the clamping of a large cartonized load is effected by driving the clamp arms 40 of the lift truck into straddling relation with opposite sides of the carton and in substantially aligned and parallel relation to the sides of the carton for clamping the same between the platens. Whether the carton is at floor level or located in an elevated position on another carton or platform, the platens 40 should be aligned so that material strips 44 are located at opposed lower corner portions of the carton. Clamping action is then effected by retracing piston rods 37. The hydraulic system which controls the operation of cylinder assemblies 36, 37 includes a regulator valve which limits clamping pressure to a predetermined amount and eliminates the need for operator judgment in this respect, thereby effectively eliminating the possibility of dropped or crushed cartons. During clamping action the thicker, softer material 48 first contacts the sides of the carton above the bottom corner portions thereof and has been actuated into full and compressed frictional engagement therewith at such time as frictional engagement is effected between the thinner, harder strips 44 and the longitudinal bottom corner portions of the carton. Thus, full frictional engagement and generally equal distribution of clamping force occurs over the entire engaged side portions of the carton. Use of single thickness facing material or materials over the entire surface of the platens, as provided prior to this invention, tended to result not only in an unequal distribution of clamping force, but also facilitated a tendency of the carton when clamped to pivot or rotate forwardly out of the clamp attachment as a result of the major holding force being applied along the bottom corner portions of the carton, the carton being unsupported at the front side thereof, or, if sufficient clamping force was applied to avoid the above tendency, the bottom corner portions of the carton were frequently crushed.

Referring now to FIG. 4, wherein similar parts have been numbered similarly as in FIG. 1, a double platen clamp attachment is disclosed wherein a somewhat different arrangement of platen facing material, such as the Wedge-Grip and Armaplate materials described above, is used. Clamp arms 50 are mounted from opposite pairs of support cylinders 26, 28, actuator cylinders 36 being mounted as in FIG. 1 for opening and closing the clamp arms 50 with extension and retraction of piston rods 37. Mounted at the front end of each clamp arm 50 is a pair of longitudinally extending and vertically spaced arms 52 to which are mounted for limited pivotal movement adjacent the opposite end portions thereof a pair of longitudinally spaced clamp platens 54 and 56. Pivot pin assemblies 58 are mounted in end openings in each arm 52 for mounting the respective platen 54 or 56 to the arms 52, which in turn are pivoted by pin means, not shown, located in the front end portion 60 of each clamp arm 50. An upper platen portion 62 is secured to each platen 54 and 56 by bracket and metal strap means 64.

The over-all clamp structure of FIG. 4 as described above is known, and need not be described in further detail here. The clamp is used primarily for handling a plurality of large cartons simultaneously between the front and rear pairs of platens 54 and 56. Exemplary of such clamp construction is assignees Model B-S Double Platen Clamp. I have found that previously all such double platen clamps which used a facing material over the inner clamping surfaces of the platens used a single material, such as Armaplate, over the entire surfaces of both pairs of platens 54 and 56. As a result, the carton or cartons engaged by the forward pair of platens 54 were frequently gripped with less clamping force than is desirable, or the carton or cartons gripped by the rear pair of platens 56 were clamped with too great a force which tended to crush the cartons. In addition, the cartons held by the front platens 54 frequently tended to rotate forwardly out of the clamp. These undesirable effects were caused primarily by the prior use of a single thickness facing material, as aforesaid. I have found that in addition to the problem encountered with single platen arms, as described above with respect to FIG. 1, the forward platens 54 of a double platen clamp construction tend to deflect outwardly under clamping force a greater amount than the outward deflection of platens 56, being located as they are at the front ends of relatively long arms 52. Previously, therefore, the engagement of side by side cartonized leads by front and rear platens such as 54 and 56 either resulted in less than the desired clamping force at platens 54, or greater than the desired clamping force at platens 56, both as a result of the difference in deflection between the pairs of platens mentioned above. Furthermore, the problem relating to the holding effect at the bottom corner portions of platens 54 described above with regard to FIG. 1 also pertains in FIG. 4 to the forward platens 54 per se, thereby further tending to effect a loss or slipping of the load held between platens 54.

My invention provides a facing material having characteristics such as Armaplate, described above, over the entire inner surface of each platen 56, while at the same time utilizing the same or a similar material along a relatively narrow sttip longitudinally of the bottom of each platen 54, and facing the remainder of each platen 54 with a material having characteristics such as Wedge-Grip, described above. In the combination of FIG. 4, therefore, the facing of platens 54 correspond to the facing of platens 40 in FIG. 1. Thus, when clamping force is applied to cartonized loads by the clamp of FIG. 4, the front carton will be first engaged by the relatively thick, soft facing material of platens 54. Said latter material will compress and platens 54 will deflect a small amount outwardly until the relatively thin, hard facing material of platens 56 engages the sides of the rear carton. At the same time, full engagement of the sides of the forward carton by platens 54 is assured as the bottom corner strip of relatively thin, hard facing material moves into engagement with the bottom corner portions of the forward carton as described in detail with respect to FIG. 1. As a result. the pair or pairs of cartons are held by the double platen clamp with a sufficiently uniform force distributed over the various carton surfaces to prevent any tendency of any carton to become dislodged or slip during handling and transport thereof by the clamp attachment of FIG. 4.

It will be apparent to those skilled in the art that various changes in the structure and relative arrangement of parts may be made without departing from the scope of my invention. It will be understood, of course, that reference above to specific clamp models and platen facing materials is intended to be exemplary only, and not limitative. Any suitable combination of materials for facing the single or double platen clamps in the manner described above which will provide the desired clamping characteristics, are intended to be covered herein.

I claim:

1. In a material handling device having a vertically movable load support carriage, oppositely disposed clamp plate members supported by the carriage and means on the carriage for actuating said plate members laterally in and out for engaging and lifting therebetween cartonized loads, a pair of inner clamping surfaces on said clamp plate members, and facing means secured to and substantially covering each said surface, said facing means including a relatively narrow strip of relatively thin material having a friction type surface secured longitudinally of and to the bottom portion of each said surface and a relatively thick and yieldable material having a friction type surface secured over at least a major portion of the remainder of each said clamp surface above said narrow strip, said relatively thick material being adapted to first engage the sides of a load during clamping action of said plate members and said relatively thin material being adapted to subsequently engage the bottom corner portions of the load during said clamping action.

2. A material handling device as claimed in claim 1 wherein said relatively thick material is secured over the entire portion of each clamping surface excepting only said narrow strip.

3. A material handling device as claimed in claim 1 wherein said relatively thick material has a relatively soft rubber-like outer ribbed portion which yields under clamp pressure to enable said bottom narrow strip of relatively thin material to frictionally engage the longitudinal bottom corner portion of the load.

4. A material handling device as claimed in claim 1 wherein an additional pair of oppositely disposed clamp plate members are supported by the carriage longitudinally rearwardly of the first-named pair of said clamp plate members for clamping movement therewith, said second pair of plate members having facing means, which is composed of said relatively thin material, secured to and substantially covering a corresponding pair of inner clamping surfaces.

5. A material handling device as claimed in claim 4 wherein clamping action of said first and second pairs of clamp plate members effects frictional engagement between the sides of a load and the facing of said second pair of plate members subsequent to such engagement by the relatively thick facing material of said first pair of plate members.

References Cited UNITED STATES PATENTS 2,675,935 4/1954 Thurow 2l4653 3,145,866 8/1964 Farmer 214653 GERALD M. FORLENZA, Primary Examiner.

G. F. ABRAHAM, Assistant Examiner.

US. Cl. X.R. 294-088.

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