Patent GB-1200871-A (GB)
Title: Improvements in or relating to a sewing machine provided with a thread-cutting device
IPC: D05B65/00
Filed: 1969-01-06
Abstract: 1,200,871. Sewing machines. VIRGINIO RIMOLDI & CO. S.p.A. 6 Jan., 1969 [16 Jan., 1968], No. 760/69. Heading D1G. A sewing machine provided with a driving motor having a clutch-operating arm for operably coupling the motor to the sewing machine, thread-cutting means, and means for stopping the sewing machine with its needle in either the lowermost or the uppermost position, is additionally provided with a pneumatic control and drive device which is mechanically coupled to the clutch-operating arm and to a manual control, the pneumatic control and drive device being also connected to a further pneumatic control device and to an auxiliary pneumatic container, charging of which with compressed air being effected by the pneumatic control and drive device when the machine is started, operation of the further pneumatic control device being effectable by the pneumatic control and drive devices only when the sewing machine is stopped with its needle in the uppermost position to operate a distributing valve in order to admit the air from the charged container into a spring-return cylinder for operating the thread-cutting means, and the capacity of the container being sufficient to effect only one operation of the spring- return cylinder. A sewing machine 10 is driven by a motor 11 via pulleys 13, 15 and a belt 14. Pulley 13 is coupled to the motor by a clutch on actuation of an arm 12 by a treadle 16 via a pneumatic control and drive device 23. A rod 17 is pivoted to the rear edge 18 of treadle 16, passes slidably through a bracket 19, and is fitted at its upper end with nuts 21. Bracket 19 is rigid with a rod 20 carying at its upper end a valve cylinder 31, and is also rigid with a valve cylinder 22 containing a piston 24 biased downwardly by a spring 27 to engage a valve stem 25 with a bracket 26 adjustably fixed to rod 17. A piston 32 in cylinder 31 is connected by its rod to arm 12, and a spring 33, stronger than the spring associated with arm 12 for raising the latter to the inoperative position, is interposed between piston 32 and the upper end of cylinder 31. A compressed air line 29 is connected by a line 28 to cylinder 22 at a position above the lowered position of piston 24. The upper part of cylinder 22 is connected by a line 30 to cylinder 31 at a position closed by piston 32 when machine 10 is inoperative. Line 30 is connected by a line 35 to the right hand end of a further control cylinder 36 to urge the piston 41 therein to the left hand end. Since 28 is connected by a line 37 to a valve cylinder 38 at a position between two pistons 42 when the latter are at the right hand end of cylinder 38, whereby line 37 is connected by a line 39 to thread-severing means for biasing the latter to the inoperative position. Pistons 41 are connected by a rod 46 to a piston 44 in a cylinder 45 containing a spring 43 biasing piston 44 rightwards. To start the machine, the rear edge 18 of treadle 16 is depressed to lower arm 12 to the clutch-engaged position, when further depression of edge 18 serves to lower cylinder 31 against the bias of spring 33 and thereby interconnect lines 30 and 34 to charge a container 47. When treadle 16 is released, arm 12 returns to the inoperative position and the machine stops with the needle automatically lowered. To effect thread severing, the rear edge 51 of treadle 16 is depressed, whereby the machine starts and then automatically stops with the needle raised. Rod 17 is thereby also raised relatively to bracket 19, whereby bracket 26 raises stem 25 and piston 24 to disconnect line 28 from line 30, and to connect line 28 to a line 52 connected to the left hand end of cylinder 36. Piston 41 thereby moves rightwards, but can complete its stroke only if an extension 56 of the associated piston rod enters a slot 54 formed in a disc 53 rigid with pulley 15 in conformity with the needle being in the raised position. Piston 41 is coupled to a piston 60 in a valve cylinder 49, whereby piston 60 moves rightwards to connect container 47 via lines 48 and 50 to the right hand end of cylinder 45. Piston 44 is thereby moved leftwards to connect line 37 via the space between pistons 42 and a line 40 to the thread-severing means for actuating the latter. Thereafter, when the supply of air in container 47 is exhausted, spring 43 moves piston 44 rightwards for re-connecting line 37 to line 39. When treadle 16 is released, piston 41 again moves leftwards. In a modification the pneumatic control and drive device 23 comprises a casing 72 formed with a through bore which receives opposed plungers 73, 74 pivoted to arm 12 and treadle 16 respectively. Plunger 73 is biased inwardly by a spring 75 to engage a flange 77 on plunger 73 against a stop surface. Plunger 73 is formed at its inner end with a piston portion 78 and an adjacent portion 79 to a radial bore 83 in portion 79. In the inwardly-disposed position of plunger 73, bore 83 communicates with an outlet 81 connected to an air pressure line. Plunger 74 is biased outwardly by a spring 84 to engage a flange 86 on plunger 74 with a stop surface. Plunger 74 is formed with portions 88, 89, 90 of reduced diameter, and with an axial bore 94 extending from the inner end of plunger 74 to a radial bore 93 in portion 89. In the outwardly-disposed position of plunger 74, bore 93 communicates with an outlet 92 connected to the right hand end of valve cylinder 36. When the edge 18 of treadle 16 is depressed to start the machine, casing 12 moves downwards relative to plunger 73 and outlet 81 is connected via portion 79 and bore 83 to an outlet 80 communicating with container 47. When the edge 51 of treadle 16 is depressed to sever the threads, plunger 74 moves upwards relative to casing 72, whereby compressed air from the right hand end of cylinder 36 is exhausted via portion 88 and an outlet 91, while compressed air is supplied via bore 93 to an outlet 95 communicating with the left hand end of cylinder 36. When the treadle is released, compressed air is again connected to outlet 92, and compressed air from outlet 95 is exhausted via portion 90 and an outlet 96. For raising the presser foot 70, a knee pad 63 is actuated to shift twin pistons 66 in a valve cylinder 62 against a spring 64, thereby to disconnect an air pressure line 65 from line 29, and to connect line 65 via a line 67 to a cylinder 68 for raising the presser foot-actuating piston 69 therein against the bias of a spring 71.