Wrapped driving anvil

An anvil is provided for use in a blind fastening system. The anvil is made using a process of wrapping a piece of wire stock around a mandrel. This process provides significant cost advantages compared to the process of machining the anvil.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT While the invention may be susceptible to embodiment in different forms, there is shown in the drawings, and herein will be described in detail, a specific embodiment with the understanding that the present disclosure is to be considered an exemplification of the principles of the invention, and is not intended to limit the invention to that as illustrated and described herein. The novel anvil 60 of the present invention is shown in FIGS. 5 - 8 . As shown in FIG. 5 , the anvil 60 includes a cylindrically shaped tubular first portion 62 and a second portion 64 . The first portion 62 has a bottom end 66 and a top end 68 . The second portion 64 extends radially outwardly from the top end 68 of the first portion 62 . A central passageway 74 is provided through the center of the first portion 62 and the second portion 64 . A slot 72 extends through the first portion 62 and the second portion 62 and is in communication with the passageway 74 . Two free ends 70 are provided on either side of the slot 72 . Unlike the prior art anvils which are made by machining bar stock, the anvil 60 of the present invention is formed from wire stock 80 which is wrapped. As shown in FIG. 6 , the wire stock 80 used to from the anvil 60 includes elongated rectangular first portion 82 and an elongated rectangular second portion 84 perpendicular to the elongated first portion 82 . Side 85 a of the wire stock 80 will define the wall of the central passageway 74 through the anvil 60 and side 85 b of the wire stock 80 will form the exterior surface of the anvil 60 . As shown in FIG. 7 a , to form the anvil 60 , the wire stock 80 is cut to a predetermined length, creating the two free ends 70 . Side 85 a of the wire stock 80 is placed against a mandrel 90 . A brace 92 with a generally U-shaped groove 94 is placed against the side 85 b of the wire stock 80 . As the mandrel 90 is brought within the U-shaped groove of the brace 92 , the wire stock 80 is wrapped around the mandrel 90 so that the side 85 a of the wire stock 80 follows the curvature of the mandrel 90 and the side 85 b of the wire stock 80 follows the curvature of the U-shaped groove 94 of the brace 92 . Two arms 96 are then used to force the two free ends 70 against the mandrel 90 to complete the wrapping of the anvil 60 around the mandrel 90 as shown in FIG. 7 b . Depending upon the length of the wire stock 80 and the dimensions of the mandrel 90 , the free ends 70 may or may not abut each other. The angle of the slot 72 depends upon the length to which the wire stock 80 has been cut and the diameter of the mandrel 90 around which the wire stock 80 is wrapped. It has been found that the angle of the slot 72 can be as large as sixty degrees (60°) without significantly impacting the performance of the anvil. The smaller the angle of this slot however, the more similarly the anvil 60 will function like the prior art machined anvil. The anvil 60 is then removed from the mandrel 90 and is ready for assembly with the remaining parts of the fastening system. The L-shaped cross section of the wire stock 80 used to form the anvil 60 can be seen in FIG. 8 . Side 85 a of the wire stock 80 defines the central passageway 74 through the anvil 60 . Side 85 b forms the exterior surface of the anvil 60 . As shown in FIGS. 1 - 4 , the malleable locking collar 38 is designed to fill the gap 44 between the sleeve 20 and the stem 22 . With the anvil 60 of the present invention, because the anvil 60 includes a slot 72 , rather than filling the gap 44 , a portion of the malleable locking collar 38 may bleed into the slot 72 . The larger the slot 72 , the more bleeding that will occur and the smaller the slot 72 , the less bleeding will occur. Thus the smaller the slot 72 , the closer the anvil 60 will function to a machined anvil. The process of forming the anvil 60 using a wrapping process results in very little material waste. First the wire stock 80 can be cut precisely to the length desired to form an anvil with a desired diameter. Second, the wire stock 80 is formed to provide the upper and lower portions 62 , 64 of the anvil. This eliminates the need for drilling or for using a lathe to create the required inner and outer diameters. Thus, material is not lost to these processes. Additionally, time is not lost to these processes. The reduction of waste and the simplified method of creating the anvil 60 results in significant reduction in the cost of manufacturing the anvil. It is estimated that the cost of manufacturing the anvil is reduced by thirty to forty percent using the wrapping process instead of machining the anvil. In addition to the cost benefits which are provided by the wrapped anvil 60 , there are also structural benefits. The wire stock 80 used to make the anvil 60 is generally purchased in spools of hundreds or thousands of feet. Because the anvil 60 used in the blind fastening systems are generally very small, dozens of anvils 60 can be formed from a single foot of wire stock. Because the material properties of the wire stock are generally consistent throughout the continuous spool, the material properties of anvils made from that spool will also be consistent. The material consistency is important for consistent operation of the anvil within the blind fastening system. While a preferred embodiment of the present invention is shown and described, it is envisioned that those skilled in the art may devise various modifications of the present invention without departing from the spirit and scope of the appended claims.