ES367654A1 - Dual speed clutches with brake - Google Patents

Abstract

In a driving and stopping mechanism for a sewing machine wherein an electric motor 10 drives a flywheel 32 directly and a pinion 27 through a toothed belt reduction gear 15, 16, 17, 19, 23, 25, 26, and a driven disc 61 fast with an output pulley 100 is selectively connected to the flywheel 32 and pinion 27 or is held by a brake under the control of an electromagneticaly operated clutch-brake unit 98 and a manual control 85, the clutch-brake unit comprises co-axial electromagnets 75, 76 in an axially slidable housing 72 which respectively control clutch disengagement and brake engagement. Initial depression of an operating pedal (not shown) pivots an arm 105 relative to a bellcrank 87 to operate a micro switch 109 which de-energizes the electromagnets 75, 76 whereupon a spring 96 moves the output shaft 55 and driven disc 61 right to engage the latter with the pinion 27 for low speed drive. On additional depression of the pedal the bellcrank 87 turns abouts its pivot 106 and acts through a sleeve 82, cap 90, ball bearing 81, strut 80, plate 57 and ball bearing 56 to move the shaft 55 and driven plate 61 left to engage it with the flywheel 32 for high speed drive. On release of the operating pedal the spring 96 moves the driven disc 61 right into engagement with the pinion 27 for low speed drive and thereafter the electromagnets 75, 76 are energized. Energization of the electro magnet 75 draws the magnet housing 72 left into engagement with a plate 79 and the housing acts through the plate 57'and' bearing 56 to move left the driven disc 61 to a position in which it is disengaged from both the flywheel 32 and pinion 27. Energisation of the electromagnet 76 clamps a disc 68 fast with the plate 57 against a friction facing 102 fast with the magnet housing 72 to brake the driven disc 61. In Fig. 3 (not shown) the radially outer electromagnet is spring urged to the left for clutch disengagement and is energized to move the magnet housing right during drive. Stopping control circuit. The driven shaft is stoped in a predetermined position by engaging the braking electromagnet when the driven shaft speed has fallen to a predetermined value. When the control pedal is released a switch II is closed and supplies current to a switch 229 or 231 depending on the position of a manually operated switch l2 The switches 229, 231 are closed by a magnet rotating with the driven shaft to produce a pulse at a point D during each rotation of the driven shaft. As the driven shaft speed decreases the length of the pulse increases to provide increasing voltage pulses to the gate 251 of a controlled diode T. When the voltage of the pulses applied to the gate 251 exceeds a threshold value the diode becomes conducting to energize a relay 256 which energizes the braking electromagnet. The switches 229,231 are arranged 180 apart so that by operation of the switch 12 the sewing machine needle may be stopped in either the needle up or needle down position.