Patent GB-801209-A (GB)
Title: Improvements in or relating to fastener inserting apparatus
IPC: B25C1/04
Filed: 1956-02-10
Abstract: 801,209. Nailing. BRITISH UNITED SHOE MACHINERY CO., Ltd. Feb. 10, 1956 [Feb. 10, 1955; July 26, 1955 Sept. 20, 1955], No. 4178/56. Class 89(3) A fastener inserting apparatus includes a fastener inserting gun 20 comprising a cylinder 42 containing a piston 44 attached to a driver 46, the return stroke and the driving stroke of which are effected, respectively, by pressurizing and venting a chamber 60 defined in the cylinder 42 on the lower side of the piston 44. In the position of the piston 44 shown in Fig. 2, the apparatus is set ready to perform a driving stroke, and the chamber 60 contains compressed air at the same pressure as exists in a compressed air supply pipe 26. A chamber 62 on the upper side of the piston 44 and an accumulator 64 surrounding the cylinder 42 and communicating with the chamber 62 through ports 66, contain air at a presure below that in the chamber 60. When the nosepiece 24 of the gun 20 is pressed against a workpiece, a valve 106 is pressed upwardly in relation to the gun so that a space below a disc valve 56 which normally communicates with the compressed air supply pipe 26 through a passage 86 and chamber 80, becomes vented through an outlet 120 allowing the disc 56 to move downwardly to vent the chamber 60 through outlets 122. The compressed air in the chamber 62 and accumulator 64 then forces the piston 44 downwardly to perform a driving stroke. Upon removal of the nosepiece from the workpiece, the valve 106 returns to its previous position in which compressed air from the supply pipe 26 flows into the space below the disc 56, thereby lifting the disc 56 on to its seating to close the lower end of the chamber 60. The compressed air flows upwardly into the chamber 60 past a packing 88 in the space 58 between the disc 56 and the driver 46 and urges the piston 44 upwardly to perform a return stroke which also recompresses the air in the chamber 62 and accumulator 64. If the pressure in the chamber 62 is too low the piston moves upwardly until it actuates a valve 96 loaded by a spring 98, which admits compressed air into the chamber 62 from the supply 26. When the pressure in the chamber 62 rises to a value determined by the compression of the spring 98, the piston is moved down sufficiently to close the valve 96. The compression of the spring 98 is adjustable to enable the energy delivered by the piston to be matched to the size and type of nail being driven. The fastener supply means (not shown) is similar to the fastener supply means described in Specification 780,311 and operates in response to pressurization and venting of a signal pipe 30 when the valve 106 moves upwardly due to the nosepiece 24 being pressed against the workpiece. In order to prevent a fastener from being blown completely through the nosepiece by the blast of air by which it is delivered, the nosepiece 24 contains a quill 114, Fig. 3, which is held closed by a locking sleeve 130 until the nosepiece is pressed against a workpiece resulting in upward displacement of the nosepiece 24 and quill 114 in relation to the sleeve 130 into the position shown in Fig. 4 in which the quill is free to open when the nail is driven. Upon removal of the nosepiece from the workpiece the sleeve 130 and nosepiece and quill move downwardly in unison to the position shown in Fig. 4a, and finally, when the driver 46 performs its return stroke the quill closes and the locking sleeve is moved upwardly by a compression spring 140 to lock the quill 114 in its closed position. Two modifications of the gun are described, in each of which the piston 44 is arranged, when the pressure in the chamber 62 is too low, to uncover a port in the wall of the cylinder 42 thereby placing the accumulator 64 in communication with the chamber 60. In Fig. 10 (not shown) as the piston 44 moves upwardly to uncover this port, it acts against an adjustable spring loaded plunger which determines the pressure difference between the chamber 60, 62. In Fig. 12 (not shown), during part of the driving and return strokes of the piston 44, the chamber 62 is vented to the atmosphere through a small hole to ensure a rapid return stroke of the piston. In the two modifications, the nosepiece includes a pair of spring closed jaws which grip a nail to prevent it from being blown completely through the nosepiece by the blast of air by which it is delivered.