Patent GB-691894-A (GB)
Title: Improvements in overedge sewing machines
IPC: D05B73/12
Filed: 1951-07-24
Abstract: 691,894. Sewing-machines. UNION SPECIAL MACHINE CO. July 24, 1951 [Nov. 17, 1950], No. 17446/51. Class 112. [Also in Group XXV] Overedge stitching; trimming. -In an overedge sewing-machine with a needle moving substantially in a plane which is substantially parallel with the line of feed and preferably vertical, a carrier for an overedge looper (threaded or threadless) is reciprocable along and oscillatable about an axis substantially perpendicular to that plane and a carrier for an under-looper is reciprocable along a line at an acute angle to the plane. In the machine shown, the needle 35 is curved and is carried by an arm 36 on a rock-shaft which is oscillated by a pitman 40 from an eccentric on the shaft 22, the under looper 42 is carried by a rod 43 reciprocated in an inclined guide 44 by a pitman 57, crank 52, and link 49, and the overedge looper 60 is fixed to the end of a rod 63 which is reciprocated in a horizontal guide 67 by a. pitman 91 and crank 87, 81, and is oscillated on its axis during its reciprocation by engagement of a projection on it with a helical slot 71 in the guide 67. Both loopers may be threaded, or the upper one may be replaced by a forked unthreaded looper. An arm 102, fixed on a shaft oscillated by an eccentric 113 connected to a depending arm on the shaft, carries a trimming blade 99 co-operating with a legerblade fixed on a pedestal 98 in the usual way. The three threads pass through tension devices 160 carried on a bracket fixed to the rear part of the machine. The needle thread then passes through guides 166, 168 to the needle 35, the guide 168 being so placed that the thread is substantially vertical when the needle enters the work; between the guides the thread passes through a take-up eye in a member 167 fixed to the trimmer lever 102. The thread for the overedge looper 60 passes through guides 171, 172 and a take-up eye in a lug 173 on the trimmer lever 102. The under looper thread passes through guides 178, 179 to the looper 42, the guide 179 comprising two eyes in parallel members between which the thread may be engaged by a take-up cam 180 (not shown in Fig. 5) fixed to the end of the shaft 22; in a modification, the take-up cam has a deep peripheral groove which is entered by a fixed finger to prevent lifting of the thread by the cam. A stitch finger may be provided on the throat-plate or the presser-foot. The same looper arrangement and mechanism may be used with a straight needle. Feed.-Two feed dogs 115, 116 are provided, and are given differential movements by eccentrics 124, 125 which are fixed on the end portion of the shaft 22 and may be replaced by others of different eccentricity to vary the feed. The feed-bars are' slidably supported at the rear of the machine on a pivoted block and. near the front on a feed-lift eccentric portion 122 of the shaft 22. The dog 116 has an opening to permit passage of the looper 42. Frames lubricating; work supports; cooling. -The frame forms an enclosed chamber containing most of the mechanism and providing an oil reservoir, the bottom of it being closed by a removable plate 12; oil is splashed on the mechanism by a dipper 94 extending downwards from the pitman actuating the overedge looper. A cover 13 in the top gives access to the mechanism. A lug 155 on the side carries the presserbar spring mechanism. An extension 19 at the side at the bottom has a rear wall carrying the rear mounting of the feed-bars and having pivoted to it a bracket carrying the work-plate 20, which can thus be swung clear for operating on tubular work, and a cover 130 partially enclosing the feed mechanism and apertured for the passage of the hub of the under-looper thread control cam. A pedestal 98 fixed on the front of the extension 19 carries the trimming leger blade. The throat plate 157 is cut away to clear the moving trimmer blade and the overedge looper 60. A chamber 15 at the right-hand end of the frame encloses a fan 33 on the shaft 22, air being drawn by the fan through slots a in the front and rear walls of the chamber and blown against vertical cooling ribs 34 on the wall of the mechanism chamber. Presser -bars.-The presser - foot is pivotally carried by a lever 137 which is mounted on a shaft parallel to the shaft 22 at the rear of the frame and is hinged at 139 so that it can be swung clear of the work. It is pressed downwards by a spring 152 adjustably carried in a casing 154 which is fitted into the frame lug 155 so that it can be held in operative position or withdrawn sufficiently to free the lever 137. An arm 146 on the presser-lever shaft, actuated by hand, foot, or knee, has means engaging the presser-lever to lift it when required. Specification 672,098 is referred to.