Patent GB-773454-A (GB)
Title: Sewing machine
IPC: D05B69/28
Filed: 1955-04-14
Abstract: 773,454. Sewing machines. SINGER MANUFACTURING CO. April 14, 1955 [April 26, 1954], No. 10741/55. Class 112. In a buttonhole sewing machine which is started when a lever 80 is rocked to draw a rod 81 downwardly, and in which a workclamp 14 is opened against the bias of a spring 53 when a lever 70 is rocked to draw a chain 73 downwardly, said levers are adapted to be rocked by a fluid pressureoperated control unit, and the latter is controlled by a lever 111 which is normally biased to one end position by a spring 117 for maintaining the work clamp open, and is movable by means of a treadle or knee press through a chain 115 to the other end position for starting the machine and allowing the work clamp to close. Rod 81 is coupled, via a spring-biased rod 26 to a lever 23 and thereby turns the latter clockwise when lever 80 is rocked, when a member 24 on lever 23 carries a driving belt 19 from a loose pulley 20 to a fast pulley 21, and a spring-biased plunger 25 on lever 23 is disengaged from a stop cam 27 on the main driving shaft 22, a notch 29 in rod 26 being engaged by a spring-biased pivoted latch 28 to retain lever 23 in the running position. At the end of the stitching cycle, a projection on a rotary pattern cam 30 rocks latch 28 for allowing lever 23 to return to the stop position. Latch 28 may also be rocked at any time during the stitching cycle by means of a handoperated lever 31 having an arm 32 engageable with a pin 33 on latch 28. The initial downward movement of plunger 25, when re-engaging the stop cam, is utilised to operate a buttonhole cutter, a roller 34 on the plunger being disposed in a slot at one end of a lever 35, and the latter being coupled by a link 36, lever 37 and link 38 to a cutter bar 39 carrying a cutting blade 40. To prevent accidental premature operation of the cutter bar, a pin 42 on lever 37 is freely movable in a slot 41 in link 36 till near the end of the stitching cycle, when pin 42 is engaged by a shoulder 44 on a latch 43 pivoted to link 36, a spring-biased trip-lever 45 normally engaging latch 43 to hold the shoulder disengaged, and a rotary cam 47 disengaging lever 45 near the end of the stitching cycle. A pin 49 on latch 43 serves as a handle, whereby latch 43 may be held to prevent operation of the cutter bar. The control unit comprises a body 60 attached by upright arms 61 to the sewing machine table, said body containing a pair of cylinders 63 and 64. A piston 65 in cylinder 63 has a piston rod 66 which underlies one end of lever 70. A piston 74 in cylinder 64 is biased downwardly by a spring 82 and has a piston rod 75 which underlies one end of lever 80. A valve cylinder 83, disposed below cylinder 63, contains a fixed sleeve 90 the bore of which communicates via a port 85 with cylinder 63. A valve stem 91 is disposed in the bore of sleeve 90 and is slightly longer than the latter, whereby one or the other of a pair of neoprene washers 92, 93 disposed in cylinder 83 on opposite sides of sleeve 90 is engageable with a valve seat formed on its side of sleeve 90. A spring 94 biases washer 92 towards the sleeve, and a plunger 96, formed with a longitudinal groove 97, extends from washer 93 through the open end of cylinder 83. A compressed air line 87 is connected to the closed end of the latter. A valve cylinder 84, located under cylinder 64 and connected to the latter by a port 86 and to an air line 88, contains valve means identical with those contained in cylinder 83, the corresponding parts being indicated by primed numerals. The control lever 111 has a lug 110 which is positioned between the plungers 96, 96' and carries a bolt 116 which is normally biased by spring 117 to move plunger 96 inwardly, whereby compressed air enters cylinder 63 to rock lever 70 for opening the work clamp. If lever 111 is moved slightly clockwise, so that lug 110 and bolt 116 are respectively free from plungers 96' and 96, spring 94 moves plunger 96 to vent cylinder to the atmosphere, whereby lever 70 is freed and the work clamp closes. If lever 111 is moved further clockwise, lug 110 moves plunger 96' inwardly to admit compressed air to cylinder 64, whereby lever 80 is rocked to start the machine. Means are provided for preventing the return of lever 111 till the completion. of the stitching cycle. For this purpose a locking arm 120 is pivoted concentrically with lever 111, is resiliently coupled to the latter, and is provided with a pair of spaced projections 126, 127 which define a notch 142. A pivoted latch 128 has an upstanding cam surface 131 which underlies a roller 132 carried by lever 80, whereby latch 128 is held against the bias of a spring 130 when cylinder 64 is inoperative. Rocking of lever 80, to start this machine, raises roller 132 above cam 131, when spring 130'moves latch 128 under projection 127 to a position such that, when lever 111 is released, lug 110 is moved by spring 117 free from plunger 96', whereby cylinder 64 is vented, but insufficiently to bring bolt 116 into contact with plunger 96. At the end of the stitching cycle, when lever 80 is rocked in the reverse direction, roller 132 co-operates with cam 131 to move latch 128 free of projection 127, whereby bolt 116 moves plunger 96 to open the work clamp. Return of lever 111 is also prevented when lever 31 is operated to stop the machine before the completion of the stitching cycle. For this purpose lever 31 is connected by a rod 147 to a bell-crank lever 145, the arrangement being such that when lever 31 is operated, lever 145 moves a pivoted latch 140 against the bias of a spring 143 into notch 142. In addition, latch 140 is connected by a flexible cable 144 to the handle 49, whereby latch 140 is moved into notch 142 when handle 49 is operated at the end of a stitching cycle to hold shoulder 44 clear of pin 42 for preventing operation of the cutter bar. An electric motor 18 drives the belt 19 and also drives an air compressor 100 for operating the control unit.