Patent GB-849209-A (GB)
Title: Sewing machines
IPC: D05B35/12
Filed: 1958-09-22
Abstract: 849,209. Sewing machines. SINGER MANUFACTURING CO. Sept. 22, 1958 [Sept. 26, 1957], No. 30158/58: Class 112 . The invention relates to a machine for automatically sewing a series of buttonholes along the seamed edge of a shirt front-portion. Work guides and supports. The machine has a work clamp which is actuated by a cable 43 operated by automatic means described below or by a pedal. Secured to the lower jaw of the work clamp is a work guide (see Fig. 10) comprising a bottom plate 51, to which is secured an angle bracket 54, and a top plate 57 adjustably secured to the bracket 54 by screws 63. Spring workpressing members 64, 65 are secured to a raised work guiding flange 58 formed on the top plate. A shirt front section (Fig. 12, not shown) is introduced, face side upwards, between plates 51 and 57 with the hemmed edge disposed on the righthand side as viewed in Fig. 10. The shirt front is then folded back over the top guide plate 57 and the hemmed edge introduced, bottom side up, beneath the members 64, 65 and against the flange 58. Feed by clamps. The top edge of the shirt front is then inserted between the jaws of a work gripper 66 and the jaws closed. The gripper comprises jaws 71, 73, Fig. 2, pivoted on a block 67 which is slidable in vertical guide rails 68, 69, the gripper being shifted downwards in steps by means of a chain 157 to manipulate or index the work between successive button-hole sewing operations of the machine. The automatic operation of the machine is effected by a mainshaft 93, Figs. 5 and 9, driven through a one-revolution clutch 94 by a sprocket wheel 92 which is driven by an index drive motor 89, Fig. 15. The clutch has a control disc 95 having stop shoulders 96, 97 either of which may be engaged by a spring biased stop lever 98, a solenoid 99 being provided which, when energised, withdraws the stop lever. Arms carried on the shaft 93 are arranged to engage with microswitches 100 and 110 respectively at different angular positions of the shaft. A clamp opening cam a shirting cam 130 and a work indexing cam 140 are secured to the shaft 93. The clamp opening cam has a follower which operates the cable 43 to open the work holding clamp. The starting cam 130 has a follower 131 which operates a push rod 132 to shift the stop motion frame 26 into the sewing-machine starting position. The work-indexing cam 140 is engaged by a follower lever 141 pivoted on a shaft 123. A connecting rod 148 carries at its upper end a socket 149 embracing a knuckle pin 144 which is slidably adjustable along the length of the lever 141. The lower end of the rod 148 is connected to a rock arm 152 pivoted on an indexing shaft 153 and drivably connected to it by a free wheel mechanism 154 which transmits motion to the shaft only in a clockwise direction as viewed in Fig. 5. A sprocket wheel 155 is journalled on the shaft 153 and is operatively connected to it by an electrically operated magnetic clutch 156. The sprocket wheel carries a lug 181 which can engage and open a normally closed microswitch 180. The chain 157 secured at one end to the sprocket wheel extends vertically upward between the guide rails 68, 69, is attached to the work gripper 66 and passes over sprockets 158, 159, its other end carrying a counterweight 160 sliding in a pipe 161. A dashpot bore 163 at the bottom of the pipe receives a plunger 164 on the counterweight to check the latter's descent. The machine is shown at rest with the cams and clutches disposed ready for the start of a new cycle of operation in which a series of button holes are to be made in the shirt front, which is not here shown. The driving motor and the index drive motor are running. Closure of the starting switch 220 (see Fig. 15) energises relays R4 and R5 in turn to complete the circuit of the clutch stop solenoid 99, which withdraws the lever 98 from the stop shoulder 96, engaging the clutch 94 to cause the shaft 93 to rotate, one arm thereon then leaves microswitch 100 which opens to de-energise the relay R5 and consequently the solenoid 99, the lever 98 being released to ride on the clutch control disc 95. The clamp opening cam rotates with shaft 93 to close the work clamp after about 55 degrees of rotation of the shaft. After about 90 degrees of rotation the cam 130 starts the sewing machine which then commences to sew a buttonhole. As the shaft 93 approaches 120 degrees of rotation the microswitch 110 is closed by the other arm on the shaft 93, and at 120 degrees of rotation the lever 98 engages the shoulder 97 of the clutch control disc and stops the mainshaft. The buttonhole is then cut by a mechanism which is only operative if the needle thread has not been broken. After the machine has completed its buttonhole sewing and cutting, a sensing lever 40, Fig. 7, is operated by the buttonhole cutting mechanism to close the microswitch 190 to energise, through the held closed microswitch 110, the relay R5, whereupon the lever 98 is withdrawn from the shoulder 97 to permit the shaft 93 to begin to complete its revolution. The appropriate arm on the shaft 93 leaves the switch 110 which then opens, de-energising solenoid 99 and releasing the lever 98. The work clamp is opened by its cam, while cam 140 rotates the sprocket wheel 155 through the clutch 156, the latter being energised through a circuit which includes the normally closed contacts R6C of the relay R6. The work gripper 66 is thus moved a distance down the ribs drawing the shirt front between the plates 51, 57 to present another part of the shirt front to the stitching instrumentalities for the formation of a buttonhole. The rotation of the sprocket wheel causes the cam lug 181 to leave, and thus close, the switch 180. As the shaft 93 completes its revolution the arm again closes the switch 100 which completes a circuit to energise the relay R5 and the solenoid 99, withdrawing the arm 98 to allow the shaft to start revolving again. The cycle of operations is repeated automatically for each buttonhole until a cam member 171 carried on the work gripper, block 67, engages and closes a microswitch 170 to energise the relay R6 and de-energise relay R4 which respectively de-energises the clutch 156 to free the wheel 155 from the shaft 153, when the counterweight 160 returns the work gripper to its original position at the top of the rails, and stop the shaft 93 at its zero position. The work gripper is opened, just prior to the closure of the switch 170, by the engagement of its handle with a trip lug 172. Counting mechanism. A counting relay is incorporated in the circuit to prevent the commencement of a new sewing cycle if the thread remaining in the bobbin is insufficient to complete the cycle.