US2613964A - Clamp - Google Patents

Description

Oct. 14, 1952 A, A, HOCHER 2,613,964

CLAMP Filed June 25, 1949 Patented pt. 14, 1952 CLAMP Andrew A. Hocher, Glenshaw, Pa., assignor to Hubbard & Company, Pittsburgh, Pa., a corporation of Pennsylvania Application June 25, 1949, Serial No. 101,438

(c1. asi- 1) Claims. l

The present invention relates to the art of connecting a load, generally a load in tension, to a bar of wood or piece of timber or the like lengthwise of the same. The problem of attaching a steel or other metal harness to the end of a wood bar or timber in such a Way as to develop advantageously the loading value of the materials involved has always presented a challenge. For example, in Douglas nr Wood, the average ultimate compression stress endwise of the grain will be found to be about 3600 p. s. i., whereas the average elastic limit in compression perpendicular to the grain will be found to be about 630 p. s. i. Medium steel will exhibit an ultimate strength in compression or tension of about 60,000 to '70,000 p, s. i. In the case of an exposed installation standing under load, and being subject to alternate wetting and drying, with consequent tendencies to expand and to contract, the hydroscopicity of the wood greatly complicates the problem.

In the construction of electric transmission lines, there is frequent need for hitching a load to a wood bar or timber, and the present invention finds application in that field as well as in others.

I have studied the characteristics of prior devices for this purpose, and observe that they are generally subject to a variety of faults, among which are the following:

Where a self-energizing action is incorporated with one of the wedging surfaces consisting of the wood member, the Vplastic deformation under changes in atmospheric moisture Will tend to alter or destroy the shape of the wedging surfaces. In other devices of the prior art, the wood member escapes laterally under the grip of the clamp due to the plastic flow on changes of moisture content. Some devices of the prior art require special formation of the end of the Wood bar which makes uneconomical use of the timber available, and it involves the additional expense of a forming operation.

In my companion application, Ser. No. 81,005, led March 11, 1949, I have taught the broad principles of a successful harness or clamp which overcomes the defects of the prior art. According to those teachings, the self-energization action must be incorporated in the metal parts which have the necessary strength to retain their shape and formation, even under the stress of the load. For a successful clamp or harness exposed freely to atmospheric influences, the clamp must confine the entire, or substantially the entire cross section of the portion to be gripped.

In the interest of economy, the harness or clamp must be applicable to plain straight woodbars or timbers of rectangular cross section as they are shaped in commercial processing of lumber.

The present invention embodies the principles disclosed in the said prior application in a novel mechanical embodiment which constitutes an improvement upon the invention disclosed inthe said application.

Whereas in the specific embodiment disclosed in the aforesaid application, the wedge portions through Whichthe self-energizing action under load is effected are formed primarily as bosses or projections upon the clamping plates or straps, and move with such plates or straps, according to the present embodiment, the bolts which lsustain the reaction of the wedging pressure, and which are held stationary in the wood part, carry special Wedge shaped fittings or washers under the heads (xed head and nut) which wedge washers cooperate with the adjacent partsV of the clamping plates or straps to tighten' the bolts by relativemovement between them.

The margins of the openings in the clamping plates or straps are preferably plain, and preferably comprise merely round punched holes, since that is the least expensive Way of making an opening. However, these edges may be turned up or otherwise reenforced or formed to stiften them and to promote the clamping action by self-energization.

The present form of clamp or harness ischaracterized by simplicity and neatness of construction. For the strength which it develops it is inexpensive and requires feWeroperations for its construction. By making the Wedge parts separate from the plates, it is possible to regulate the amount of compression per unit of travel, or to change the 'rate of application ofl pressure for unit travel by merely substituting one form of separate Wedge part or Wedge washer for another.

VNow in order to acquaint those skilled in the art with the manner of constructing and operating a device embodying my invention, I shall disclose, in connection with the accompanying drawings, a specific embodiment of the same.

In the drawings:

Figure 1 is a side elevational view of a" clamp or hitch of my invention for connecting a load to a Wood bar or timber;

Figure 2 is a longitudinal vertical section through the device of Figure 1 on an enlarged sca e;

3 Figure 3 is a plan View of the top and bottom plates;

Figure 4 is a similar plan view of the side plates;

Figure 5 is a plan view; and

Figure 6 is a side view of a form of wedge washer employed in the structure of Figures 1 and 2;

Figure 'l is a plan view; and

Figure 8 is a side view of a modied form of Wedge washer;

Figure 9 is a fragmentary section through a bolt, wedge washer and clamp plate showing a modified form of opening in the clamping plate; and

Figure 10 is a similar fragmentary sectional view of a modified form of the clamp plate.

Referring to Figures 1 and 2, a square wood bar I, with the grain running lengthwise thereof, has attached to the end thereof a clamp 2 through which there is adapted to be applied through the sheave 3 the pull of a cable wrapped around the sheave 3. Any other load may be transferred to the clamp 2 through the bolt 4. rI'he bolt 4 passes through a pair of parallel ears 5, 5 integral with a pair of straps or clamping plates 6, 6, disposed on opposite sides of the wood shaft or stick I. Two or more plates 6 on each side may be utilized as disclosed in my aforesaid application. The main body of the plate 6 is connected to its corresponding lug 5 by a diagonal portion 1, so that the load may be more nearly centralized for equalization of the pull upon each of the plates 6, 6. Each plate 6 has notches, such as 8, 8, at the opposite sides of the body, and has holes of relatively large diameter punched through the plate, as shown at 9, 9, in Figure 3. A pair of side plates I 0, I0 shorter than the plates 6, 5 clamp the opposite sides of the wood bar or timber I. These side plates have projections I2, I2 at their opposite edges, and have holes I3, I3 similar to the holes 9, 9 in the plate 5.

By way of example, but not by way of limitation, for a wood bar of approximately 3 x 3 in cross section, the top and bottom plates or straps 6, 5 and the Side plates IIl, I0 may be made of 1A flat stock, and the holes 9, 9 and I3, I3 may be of 1%" diameter for receiving clamping bolts I5, I5 substantially M2 in diameter. The machine bolts I5, I5 extend through wedge washers I6, I6, through the holes 9, S of the topplate 6, through holes I1, II drilled through the wood bar I and closely fitting the same. The bolts I5, I5 are seated in the holes in the wood bar and provide the resistance required for establishing the self-energizing action hereafter described. The bolts extend through similar wedge washers I5, I6 at the opposite end, and carry nuts I8, I8 by which the bolts may be tightened to press the Wedge Washers rmly against the margins of the holes 9, 9 in the top and bottom plates 6, 6. The wedge Washers I6, I6 are shown in plan View and in side elevation in Figures 5 and 6, respectively. It will be observed that each washer comprises a round, cylindrical top portion I8', and a generally conical depending integral portion I9, which conical portion may be of increasing taper toward the apex or may be a straight cone or otherwise shaped as desired. The tightening of the nuts I8, I8 draws the washers IS, I6 centrally into the holes 9, 9 in the opposed plates and clamps the said plates directly against the corresponding face of the wood bar I. For a round opening the wedge is preferably round, but if the wedge washers cooperates with a slot the wedge may be cut away at the sides so that the projection provides a guiding function. The superficial outline of the washer is not important so long as it does not conflict with the requirement for the intended wedging function.

As illustrated particularly in Figures 2, 5, 6 and 9, the washer IG consists of an outer portion heretofore referred to as the cylindrical top portion I3', and the centrally disposed conical portion I9. The top portion I8 is of such diameter relative to the diameter of the hole 9 that the margin of the washer extends out over and rests upon the margin of the metal of the plate 6 about the hole 9, so as to distribute Ithe clamping pressure of the bolt I5 over suflicient area to avoid too great concentration of stress. The conical projection I9 has a rather at taper for the initial movement of the plate 6. The washer I5 initially serves as a at washer for the initial tightening of the bolt l5 by the drawing up of the nut I 8, and when the endwise load applied to the clamp becomes great enough to overcome the friction of the plate against the wood surface, slippage of the plate 6 causes a wedging of the margins of the plate 6 about the hole 9, under the conical part I9 of the washer I6 to increase the grip of the plate upon the wood surface. The conical washer I6 thus does not wedge itself into the hole in its initial clamping position, but tends rather to cover the margins of the hole with the projection 9 depending loosely into the hole.

So much of the structure, i. e., the plates 6, S, 'bolts I5, I5 and Washers I6, I6 constitutes a selfenergizing clamp which may be sufficient under certain circumstances and for certain purposes to effect connection to the bar I. However, the complete device suitable for outdoor service involves additionally the side plates I0, I 0 which are mounted by means of bolts 20, 20 registering with the openings I3, I3 in the side plates, and clamping the said side plates against the sides or flanks of the wood bar I, with similar washers I6, I6 under the heads and nuts of the bolts 20, 20. The top and bottom plates 6, 6 are of a width greater than the width of the face of the wood bar I upon which they rest by an amount at each side substantially equal to the thickness of the side plate I0, whereby the projections I2, I2 on the side plates may engage in the notches 8, 8 in the top and ybottom plates 6. The width of the side plates across the projections I2, I2 is substantially equal to the width of the top and bottom plate 6, so that a full cross section of the metal of the top and bottom plate and of the side plate is interengaged at each corner and form a suitable interdigitation. This arrangement of notches and projections permits the shrinking or moving together towards the center of all four plates with increase of pressure upon them. Suf cient clearance is provided between the edges of the side plates I0, I0 and the overhanging margins of the top and bottom plates 6 to take up the necessary decrease in cross sectional area under compression which the wood bar I undergoes under load.

The operation of the device is as follows: Assume that the top and bottom plates and the side plates have been applied, and the bolts with their wedge washers in place in their respective openings have been tightened up, the frictional engagement of the top and bottom plates and of the side plates upon the lateral surfaces of the wood bar I should be sufficient to carry the load put upon the hitch formed by the ears 5, 5 and the bolt 4. As above explained, the sheave 3 is Athe holes.

a convenient method of attaching a Wire cable, such as a strand of guy wire, the said sheave 3 then resting in a bight of the strand. If, however, due to shrinkage of the wood, the pressure which is imposed by the bolts I5, I5 and 20, 2|] is relaxed, the pull upon the hitch will tend to slip the plates 6, 6 to the right as viewed in Figure 1. Any slippage of these plates will carry with them the side plates I0. However, slippage of the plates on the surface of the wood bar I is not accompanied by movement of the bolts I5, I5 and 20, with the result that the edges of the holes 9, 9 and I0, I0 shift with respect to the conical surface of the wedge washers I6, I 6, with the result that the plates I0, IIJ are forced towards each other, and the plates 6, 6 are forced towards each other, thus shrinking the grip of the clamp upon the end of the wood bar.

Ihe self-energizing action under load is thus secured by the provision of the separate Wedge washers under the bolt heads bearing upon the adjacent surfaces of the plates at the edges of This construction requires no special shaping of the plates to provide cam surfaces, since the cam or wedge surfaces are provided by the wedge washers.

In Figures 7 and 8 I have shown a modified form of the wedge washer in which the top part is oval, so that the hole over which it is placed will continue to be covered even though there is some travel of the plate relative to the washer.

In Figure 9 I have illustrated a modification of the formation of the holes in the plates wherein the edges are turned up or slightly hanged as at 22 to reenforce the metal at this point. This is optional.

In Figure 10 I have shown a modification of the holes to constitute slots not substantially wider than the diameter of the corresponding bolt I5, with the washer Ilia reaching across the edges of the slot 23, which edges are flanged as indicated at 24 and shaped to provide a wedge surface allowing for a degree of travel in which the wedge supplied by the upturned flange 24 will serve to take up the required shrinkage of the cross section of the wood, and the nal takeup may be provided by the projection I9a. which in this case is reduced at the sides and provided in full only at the front and rear of the bolt. The projection I9a is guided in the slot 23 between the parallel sides of the upturned flanges 24 at the sides of the slot.

The form of interengaging wedge washer and hole shown in detail in Figure 2 is applicable for movement of the plate in any direction. This means that the load upon the hitch might be either a pull or a push with the resulting selfenergizing increase in the grip or clamping effect of the device.

The conical wedge washers tend to center themselves upon the edges of the holes, and thereby center the plates 6, 6 and I0, I0 with respect to the bolts. Since the wood bar I may be drilled in advance in a fixed jig or fixture, the application of the device to the wood member is accurate, expeditious and convenient. The clamp of my invention acts like the Chinese nnger trap to this extent, that the greater the load, the tighter is the grip upon the bar I. This is done by my invention upon a square section without injury to the fibers of the wood by the applied pressure. An important feature of the invention is that the full strength of the wood bar in tension can be developed, and the pressure of the plates on all four sides assists in strengthen- 6 ing the end of the wood bar against splitting or tearing out of the bolts I5, I5 and 2U, 20 endwise of the grain of the wood.

While I have shown the holes 9 and I3 as circular, they may obviously be oblong with their major axis in the direction of movement of the plate to increase the clamping eect. The holes being substantially larger than the bolts permit, in the example given, of is" motion relative to the bolts before the continued Wedging action is exhausted. The inclination or throw of the wedges may be designed to increase more rapidly towards the end of the travel, so that the inward movement of the plates before the wedging action is exhausted may be fairly large. Thus, forexample, Where the wedge washer projects 1A down into the hole in the plate, the margin of the plate must move towards the center of the bar 1A" on a side before the possibility of further wedging action is exhausted. When I speak of wedge washers I do not intend to confine the meaning of the term to a round plate or a round projection. The outline is not important so long as it does not interfere with the function.

The interdigitation provided by the projections I2 and recesses 8 may be increased by increasing the number of projections and recesses if so desired.

It will be observed in Figurev2 that the adjacent bolts are tangent or substantially tangent. The purpose of this is first to produce a band of constriction substantially at right angles to the longitudinal axis of the bar, and, second, where the bolt I5 bears against the bolt 20, the bolt I5 cannot tear out without carrying the bolt 20 with it. This is a feature which, however, is optional.

As previously explained, the advantages of my invention, in useful degree, may be secured by the employment of the aforesaid self-energizing grip upon only two opposed plates, with or without side plates of conventional construction.

I do not intend to be confined to the exact form of the elements herein disclosed, except as the same is made essential by the specific recitation of the appended claims, for those skilled in the art will find it advantageous to adapt the teachings of my invention to the special circumstances of their requirements.

I claim:

1. A self -energizing clamp for clamping a bar of wood comprising a pair of clamp members having bar engaging faces for engaging opposite sides of a bar to be gripped, said members having registering transverse openings therethrough, a through bolt adapted to be seated xedly transversely in the bar and having its ends extending through said openings, said openings being substantially larger than the cross section of the bolt, heads on the outer ends of said bolt, and wedge members mounted on the bolt one under each head, each of said wedge members being inclined inwardly relative to the corresponding bolt head in the direction in which the corresponding clamp member is urged by the applied load, said wedge members projecting into said openings.

2. The clamp of claim 1 wherein the wedge members carried by the bolt are in the form of tapered washers and the openings in the plates are substantially round holes.

3. The clamp of claim 1 wherein the wedge members carried by the bolt are thick washers each having a central conical projection of increasing steepness toward the apex, and the openings in the plate are larger than the diameter 7 of the bolt to the extent of admitting the inner ends of the conical projections.

4. In a device of the class described, the combination of a plate havingv a flat clamping face for frictionally engaging a wood bar, a hole extending through said plate, a clamping bolt extending through the hole and being loosely surrounded by the edge of the hole, said bolt having a head and a wedge member projecting into the hole and held under the head of the bolt in engagement with the margins of the plate about the hole by tension on the bolt, the tension of the bolt being transmitted through the Wedge member to the plate and being adaptedto press the plate against the surface of the wood bar to be gripped, said wedge member permitting motion of the plate relative to the bolt to increase the grip of the plate on the bar.

5. The device of claim 4 wherein the hole through the plate is a round circular hole, the wedge member is a washer having a central conical projection extending within the confines of the hole and a fiat outwardly extending margin, and the bolt presses the at margins of the washer against the flat margins of the plate around the opening.

6. Means for clamping a wood bar in order to sustain endwise stress which comprises at least one set of opposed flat plates having registering openings for receiving a clamping bolt, a bolt extending through the openings of opposed plates and wedge washers having wedge portions projecting inside the confines of the openings and margins engaging the flat margins of the plates about the openings, and held in place by the bolt, said wedge plates increasing the tension upon the bolt when the plates are moved endwise by the stress to be sustained.

7. Means for applying endwise stress to a wood bar which comprises a first pair of opposed clamp members having means to apply endwise stress upon both of them, a second pair of opposed clamp members adapted to be disposed `laterally of the members of the rst pair, inter-engaging shoulders between the members of one pair with the members of the other pair whereby endwise stress imposed upon the rst pair of members imparts endwise stress to the members of the second pair, at least one bolt extending through and connecting the members of each pair, said bolts having heads and being adapted to be seated iixedly in the wood bar to be clamped, said members having openings through which the bolts extend and the bolts having wedge surfaces under their heads extending into said openings, the motion of the members relative to the bolts being adapted to cause the margins of the members about the openings to ride under the Wedge members and press the clamp members of the corresponding pair towards each other.

8. In a device of the class described, two pairs of clamping plates for embracing four sides of a wood bar, the edges of adjacent plates being inter-digitated whereby movement of one plate carries with it its adjacent plates, each pair of plates having at least one opening therethrough for receiving a transverse bolt, a bolt loosely extending through said openings of each pair, and at washers with central conical projections under at least one of the heads of each bolt, said washers having their conical portions projecting into the openings in the corresponding plate, and their flat margins bearing upon the margins of the plates about said openings.

9. In combination, a wood section of substantially uniform cross section with straight sides, a pair of clamp members on opposite sides of said wood section, coupling means for connecting a load to said members, bolts extending through the members and the wood section, said bolts being xedly seated in the wood section; said clamp members having openings therein surrounding the bolts, wedge members carried on the bolts and projecting into said openings, said wedge members being adapted to engage the margins of the plates about the openings and to react directly against the bolt heads when the clamp members move forwardly on the surface of the wood section.

10. In a clamp for clamping the end of a wood bar, a pair of clamp plates adapted to face each other and having registering hitch extensions, said plates having registering openings for a clamp bolt, a bolt adapted to be xedly seated in the wood bar to be clamped, and to extend through said openings, heads for the bolt and wedge washers carried on the bolts under the heads thereof for applying the clamping pressure of the bolt heads to the clamp plates, movement of the plates on the Wood bar and relative to the bolt carrying the margins of the openings farther under the Wedge washers and increasing the clamping pressure of the plates upon the wood bar.

ANDREW A. HOCHER.

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

UNITED STATES PATENTS Number Name Date 143,879 Cathcart Oct. 2l, 1873 974,681 Le Manquais Nov. 1, 1910 1,569,060 Wright Jan. 12, 1926 1,737,869 Taylor Dec. 3, 1929 1,836,743 Austin Dec. 15, 1931 1,972,615 Austin Sept. 4, 1934 2,046,949 Horner July 7, 1936 2,099,000 Carpenter Nov. 16, 1937 2,362,664 Reed Nov. 14, 1944 2,441,709 Manke May 18, 1948

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