Patent GB-871018-A (GB)
Title: Improvements in or relating to intermittent driving mechanisms
IPC: F16H27/10
Filed: 1957-06-18
Abstract: 871,018. Gearing for stopping and starting machinery; converting rotary into oscillating motion; variable throw cranks. SCHJELDAHL CO., G. T. June 18, 1957 [Dec. 24, 1956], No. 19206/57. Classes 80 (1), 80 (2) and 80 (3). In order to provide intermittent rotation of a shaft 82, Fig. 3, it is intermittently coupled by a clutch-brake 86 to a sleeve 81 geared to a shaft 68 which is rotated in alternate directions by a rack 65 on an adjustable-throw crank-arm 33 carried by a motor-driven shaft 23, the clutchbrake 86 having a controlling solenoid 139 actuated in synchronism with the rack movements by a switch 117 controlled by a cam 30 on the shaft 23 so that shaft 82 is rotated only during the downward movements of the rack 65. The shaft 23 is coupled to a gear driven by a continuously-running motor M by means of a second clutch-brake 38 having a controlling solenoid 121 which may be continuously energized by closing a manual switch 128; or which may be energized for a single cycle only by closing a push-button 127 co-operating with a switch 108 actuated by a cam 27 on the shaft 23. The clutch brake 38, a constructional form of which is illustrated in Fig. 1 (not shown), comprises a core 44 fixed to the shaft 23, the core being engaged either with a clutch element 42 which is loose on the shaft and is driven by the motor M, or with a fixed brake element 49. The intermittently - rotated output shaft 82 is mounted in the sleeve 81 through roller bearings, (Fig. 1 (not shown), and carries the core 98 of the clutch-brake 86. The core 98 is engaged either with a fixed brake element 101 or with a clutch element 87 on the sleeve 81. Direct current is fed from a supply DC to the two clutch-brakes 38, 86 through respective solenoids 121, 139 which are themselves fed with an alternating current supply AC. When the solenoids 121, 139 are de-energized, the brake elements 49, 101 are energized. The solenoid 121 is energized either continuously through switches 124, 128 or for a single cycle through the cam-actuated switch 108, the single cycle being initiated by a push-button 127. The brake element 101 on the output shaft 82 is normally energized through a manual switch 146. As soon, however, as the shaft 23 rotates (counterclockwise) the carn switch 117 is closed to energize solenoid 139 through a normally-closed switch 137 and hence the brake 101 is de-energized and the shaft 82 is clutched to the sleeve 81. As the rack 65 reaches the bottom of its stroke the cam switch 117 is opened and the shaft 82 accordingly stops. If the manual switch 128 has not been closed for continuous running the shaft 23 is stopped during the up-stroke of rack 65 by the cam switch 108. The adjustable throw crank 33 has a guideslot for a block 60 to which the rack 65 is pivoted through a roller bearing, the block 60 being in threaded engagement with a rotatable adjusting screw 54 provided with a thumb-nut 55. The rack 65 is held against the pinion 71 by a guide, Fig. 2 (not shown) carried by the shaft 68. The shaft 68 is geared to the sleeve 81 through an intermediate shaft 74 which forms a power takeoff for machine parts requiring an oscillating movement. Where the cam 30 is shaped to hold the switch 117 closed over approximately 180 degrees, the drive through crank 33 ensures that the speed of shaft 82 is virtually sinusoidal with a high accelerating and decelerating torque. If desired, however, the cam 30 may be shaped to stop the shaft 82 abruptly before the rack reaches the end of its stroke-e.g. to cause tumbling of particles on a conveyer. The switch 137 may be operated by automatic means to interrupt and re-establish the circuit of solenoid 139, and hence stop and restart the shaft 82, at any time during which cam switch 117 is closed. The crank 33 may be adjusted to vary the speed of shaft 82. The switch 124 may be operated by means not shown to stop and restart the shaft 23, i.e. to insert controlled rest periods in a series of cycles. If desired, the speed of motor M may be varied during a rest period. The mechanism may be used for making containers from a web of flexible material which is advanced, stopped, cut and sealed before advancing again. Different thicknesses of web may require different stopped periods for cutting and sealing. The various operations required during a cycle may be effected by solenoids such as 149, 154 controlled by switches actuated by cams 29, 28 on the shaft 23.