A wire gripper with improved wire grabber

Abstract

A wire grabber has a cam (28) and anvil pivoted relative to each other to enable the cam to clamp a wire against the anvil. The cam is planar and has a curved cones leading edge (29) and the anvl is

Description

Field of the Invention The present invention relates to wire grippers which are used to tension fencing wire. Background Art Such wire grippers have a wire grabber which is formed from a cam and an anvil which are movable relative to each other so as to grab the wire and hold it tightly during the wire straining process. The wire can be either a plain wire or a barbed wire and the grabber must be able to operate with both types of wire. In addition, the grabber should not cut or otherwise damage the wire, for example by removing an anticorrosion coating of the wire. Genesis of the Invention The genesis of the present invention is a desire to provide an improved wire grabber and an improved wire gripper incorporating the improved wire grabber. Summary of the Invention In accordance with a first aspect of the present invention there is disclosed a wire grabber having a cam and an anvil pivoted relative to each other to enable said cam to clamp a wire between said cam and said anvil, wherein said cam is planar and has a curved convex leading-edge, and said anvil is planar and has a curved concave recess shaped to receive a wire, and is supported on a base plate by a pair of fasteners, and wherein each of said fasteners includes a lip portion which extends beyond said recess to form a wire restraint. In accordance with a second aspect of the present invention there is disclosed a method of grabbing a wire between a cam and an anvil, said method comprising the steps of: forming said cam to be planar and to have a curved convex leading-edge, forming said anvil to be planar and to have a curved concave recess shaped to receive a wire, supporting said anvil on a base plate by a pair of fasteners, and providing each of said fasteners with a lip portion which extends beyond said recess to form a wire restraint. In accordance with a further aspect of the present invention there is disclosed a wire gripper incorporating the above-mentioned wire grabber. Brief Description of the Drawings A preferred embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a reproduction of Fig. 2A of Australian Patent No 2017 204 418 in the name of Infrabuild Wire Pty Limited, Fig. 2 is a reproduction of Fig. 2B of the same patent, Fig. 3 is a reproduction of Fig. 7 of Australian Patent Application No 2008 203 804 in the name of Peter Barrett, Fig. 4 is a reproduction of Fig. 8 of the same patent application, Fig. 5 is a reproduction of Fig. 6 of International Patent Application No WO 2020 / 051630 in the name of the present applicant, Fig. 6 is a reproduction of Fig. 7 of the same International patent application, Fig. 7 is a reproduction of Fig. 17 of the same International patent application, Fig. 8 is a perspective view from above of a wire gripper incorporating the wire grabber of the preferred embodiment and showing the wire grabber closed, Fig. 9 is a perspective view from below of the wire gripper of Fig. 8, Fig. 10 is a plan view of the wire gripper of Fig. 8, Fig. 11 is an inverted plan view of the wire gripper of Fig. 8, Fig. 12 is a perspective view from above of the wire gripper of Fig. 8 but showing the wire grabber open, Fig. 13 is a perspective view from below of the wire gripper of Fig. 12, Fig. 14 is a plan view of the wire gripper of Fig. 12, Fig. 15 is an inverted plan view of the wire gripper of Fig. 12, and Fig. 16 is a side view of the wire gripper of Fig. 8. Detailed Description As seen in Figs. 1 and 2, in one prior art wire gripper incorporating a wire grabber an anvil 218 in the form of a separate plate is mounted on a base plate 214 by means of a pair of fasteners 228. A cam 216 having a curved nose is pivotally mounted relative to the anvil 218. The nose of the cam 216 forces the wire into a recess or hollow formed in the anvil 218 so as to bring about the capture of the wire. The need to manufacture the recess or hollow within the anvil 218 substantially increases the cost of the construction. The anvil 218 is typically cast or machined and must thereafter be heat-treated to be hardened. The fasteners 228 play no role in the wire grabbing action. Turning now to Figs. 3 and 4, in a second prior art wire gripper incorporating a wire grabber, an anvil 11 is cut from sheet steel. The anvil 11 faces the cam 12 so as to grip the wire 13 therebetween. The surface of the anvil 11 opposite the cam 12 is cut to form a curved concave recess. The anvil 11 is connected to a support plate by means of a pair of conventional fasteners. These fasteners play no role in the wire grabbing action. Turning now to Figs. 5 and 6, in a third prior art wire gripper incorporating a wire grabber, the wire grabber has a cam fastener 171 to act as a wire guide. A pair of spaced apart fasteners 172, 173 form the anvil. Although the fasteners 172-173 are each secured in position relative to a support surface, the support surfaces play no role in the wire grabbing action and the fasteners 172-173 perform the wire grabbing action. In another prior art arrangement as illustrated in Fig. 7, an anvil 274 is secured to a support surface by means of two fasteners 272, 273. The anvil 274 is located opposite a cam 280. The fasteners 272, 273 also secure in position above the anvil 274 a wire restraint plate 281 which provides a lip facing the cam 280 and which protrudes beyond the concave recess formed in the anvil 274. In this prior art arrangement the fasteners 272, 273 play no part in the wire grabbing action. The wire gripper 15 of the preferred embodiment is illustrated in Figs. 8-16 and includes the wire grabber 16 of the preferred embodiment. The wire gripper can take many forms but preferably takes the form described in the above-mentioned International patent application. That is, the wire gripper 15 has a pair of handles 18, 19, a central pivot 20 and a spring 21 all of which function as described in the abovementioned International patent application. The handles 18, 19 form two arms of a four armed parallelogram arrangement. The other arms take the form of a cam arm 28 which is pivoted to the handle 18 by means of a rivet 23. An anvil arm 29 is pivoted to the handle 19 by means of a rivet 24. The cam arm 28 is pivoted to the anvil arm 29 by means of a first fastener in the form of a first bolt 31 having a first nut 41 (Fig. 9). The anvil arm 29 is formed from two plates 35 and 36. The plate 35 carries the first bolt 31 and first nut 41. The plate 36 is pivotally connected to the handle 19 by means of the rivet 24 and carries the second and third bolts 32, 33 and their corresponding second and third nuts 42, 43. Thus the first function of the fasteners 32, 33, 42, 43 is to secure the two plates 35 and 36 so as to form a single rigid anvil arm 29. As will be explained hereafter, the second function of the fasteners 32, 33, 42, 43 is to provide a wire restraint. The plate 36 is provided with a concave recess 38 as best illustrated in Fig. 14. This concave recess 38 is preferably centrally located relative to the shanks of the second and third bolts 32, 33. The cam arm 28 is provided with a curved convex leading-edge 39. As best seen in Fig. 12, the second and third bolts 32, 33 have a respective head 52, 53 which protrudes over the recess 38 in the plate 36. Thus, the heads 52, 53 form a lip which extends over the recess 38 and thus constitutes a wire restraint which assists in holding the wire (not illustrated) between the recess 38 and the leading-edge 39. This is particularly of assistance where the wire to be restrained is barbed wire since such wire is formed from two twisted strands. In particular, the barbed wire sold in Australia under the generic name IOWA is conveniently restrained in the wire grabber by means of the above-described lip. Preferably the “anvil plate” 36 is formed from hardened steel such as that sold under the trade marks HARDOX, BISALLOY or STRENX and having a grade of 400-450 or above. Both the plates 35, 36 and the cam arm 28 are able to be cut from sheet steel plate, for example using laser cutting techniques. 5 The foregoing describes only one embodiment of the present invention and modifications, obvious to those skilled in the agricultural fencing arts, can be made thereto without departing from the scope of the present invention. For example, the features and advantages disclosed in one facet of the invention may be utilised, 10 mutatis mutandis, in other facets of the invention. For example, the fasteners 31-33 can be inverted so that, for example, a washer under the nuts 41-43 can be used to provide the lips which form the wire restraint. 15 The term “comprising” (and its grammatical variations) as used herein is used in the inclusive sense of “including” or “having” and not in the exclusive sense of “consisting only of’.

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