Heavy duty fastener and method of manufacturing same

#This invention relates to heavy duty fasteners and method of manufacturing same, and is more particularly concerned with staples such as may be especially useful in the electrical utilities industries, for example to secure ground wire covers and other members to utility poles.

#Fasteners as heretofore provided have had various and sundry disadvantages, deficiencies, shortcomings and have presented various problems both structurally and economically. Some staples have barbs of such roughness as to unduly tear the wood during driving so that the wood cannot properly recover and grip the fastener whereby poor holding power results, and weathering can creep into the wood along the staple prongs to accelerate deterioration. Where the fastener prongs or legs are inadequately anchored, they will not resist pulling out sufficiently to withstand abuse such as severe weathering conditions, brushing thereagainst of objects such as lawn mowers, linemen's boots, animals rubbing thereagainst, vibrations, bending stresses, etc. Round wire types of staples have had as one shorcoming the single point contact on the head for driving hammer impact so that there is undue concentration at such point and thus the liability of flattening until enough flat results to secure full power of blows to drive the staple into denser types or denser areas of wood. This may result in undesirable bending distortions of the head.

#Prior structures have often been difficult to make, or at least require slow manufacturing techniques, such, for example as round wire staples with rolled barbs in the production of which the wire must first but cut to length, then points formed on the legs, after which roll forming of the barbs is effected by rolling entirely around the perimeter of the wire, and the piece then finally formed into a staple. Production thus depends on how fast the roll forming tools can advance and return to the original position to pick up the next blank.

#Other objects, features and advantages of the invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings although variations and modifications may be effected without departing from the spirit and scope of the novel concepts embodied in the disclosure, and in which:

#FIG. 1 is an enlarged sectional detail view showing a fastener in staple form according to the present invention partially driven into a wood member such as a utility pole;

#FIG. 2 is a face elevational view of the fastener;

#As depicted in FIG. 1, a heavy duty fastener 10 embodying feature of the present invention is especially constructed and adapted to be driven into anchored relation in a timber member such as a utility pole 11, for example, to secure a ground wire cover 12. The fastener 10 is provided with at least one leg or prong 13 having a sharp penetrating tip 14 which may be of generally spade edge shape as shown. In this instance the fastener 10 is of the U-shape staple form having a pair of the prongs 13 in coextensive relation and connected together by an integral arcuately shaped head 15. In practice, the staple 10 is placed with the prongs 13 in straddling relation to the member to be fastened such as the ground wire cover 12 and the staple is then driven home by means of a tool such as a hammer applied against the crown of the head 15. As the prongs 13 penetrate into the wood of the pole 11 they cut across and penetrate through growth rings 17 in the wood.

#By reason of the cross sectional mass of the respective prongs 13, they must compress and displace a corresponding mass of the wood fibers. The denser growth rings 17 resist compression and as shown bend at their severed edges along the prongs 13 in the direction in which the prongs were driven into the wood member. This characteristic is taken advantage of by the present invention by providing the prongs 13 on at least one side and preferably both sides thereof with anchoring notches 18 spaced apart sufficiently to receive in each of the notches a bent edge of one or more of the growth rings 17 and more particularly the dense annual rings. To facilitate thorough anchoring engagement of the turned, bent growth ring edges with the prongs 13 in the notches 18, each of the notches is defined by a shoulder 19 facing generally toward the head end of the respective prong and a surface 20 slanting in from the side of the prong to a juncture with the shoulder. In a desirable construction, the shoulders 18 may be spaced apart about 1/8 inch and the width of the shoulders may be about 1/32 of an inch. By way of example, the fastener 10 so equipped may be made from square wire or rod stock of suitable dimensions such as on the order of from 1/8 inch to 7/32 inch cross section, with the leg prongs 13 on the order of 11/2 to 4 inches long, and the space between the prongs 13 on the order of from 1/4 to 1 3/16 inches.

#Anchoring retention of the prongs 13 by the bent edges of the growth rings 17 interlocking with the shoulders 19 is improved by a sloping shoulder angle of about 15.degree. relative to a plane normal to the longitudinal axis of the associated prong 13, and with the slope directed away from the head end of the prong and generally in the direction of the penetrating tip end of the prong. This has been found to just about match the inclination of the bent growth ring edges toward the shoulder 19, thereby effecting maximum shouldering efficiency and interlocking of the growth ring edges with the shoulder 19 and maximizing the shear forces required to remove the fastener. An included angle of about 90.degree. between the shoulders 19 and the slanting surfaces 20 has been found desirable to hold the growth ring edges bent toward the shoulders 19.