Patent GB-973454-A (GB)
Title: Improvements in or relating to electrically-controlled coupling mechanisms
IPC: F16H33/02
Filed: 1962-07-09
Abstract: 973,454. Positive clutches; spring mechanisms. LANDIS & GYR A.G. July 9, 1962 [July 18, 1961], No. 26271/62. Headings F2C and F2S. [Also in Division H2] An electrically controlled clutch for driving valves, air flaps &c. has a spring permanently connected between its driving and driven shafts and carries a switch controlling a driving electric motor, the arrangement being such that on voltage failure the driven shaft is returned to its initial position by the energy stored in the spring. In one form, an electric motor 2, Fig. 1, carries on its shaft 1 a hub 3 mounting a clutch pin 12 spring-biased to disengage radially from a hole 13 in a drum 7 fast upon a driven shaft 6 but engaged in the hole when an electromagnetic 9, Fig. 2, is energized to attract an armature 11, the driven drum carrying a twoposition switch 16 actuated by an operating protection 15 on the hub 3 to control the motor, and a spiral tension spring 4 connecting the two shafts. As a modification, the electromagnet 9, &c. may be replaced by an electrothermal device. In the initial rest position of the clutch, and with the electromagnet 9 energized, the parts take the position shown in Fig. 2, a lug 20 on the driven drum 7 engaging a stop 21 on the motor housing and the clutch pin 12 engaging its hole, while the spring 4 is under tension. The switch 16 is conditioned as shown in Fig. 5, to engage a contact 19, and a limit switch 30 is closed. When a control switch 26 is operated to make a circuit from supply lines O, P through a contact 27, the motor 2 drives to the driven shaft 6. Immediately a limit switch 29 is mechanically closed by rotation of the driven shaft 6, to allow reversal of the motor by operation of the switch 26 to engage a contact 28. If the switch 26 is maintained in engagement with the contact 27, the motor 2 continues to drive until the driven shaft 6 reaches the end of its travel. The limit switch 30 is then automatically opened to stop the motor 2, and the parts come to rest. The operative position of the driven shaft 6 has now been reached. If the applied voltage fails, the electromagnet 9 is de-energized. The pin 12 is accordingly withdrawn from the hole 13 by spring bias, and the spiral spring 4 winds the driven drum 7 back to its first position, so that the lug 20 again abuts the stop 21. Relative rotation between the hub 3 and the driven drum 7 conditions the switch 16 so that its movable contact engages a second contact 18. When the applied voltage is restored and the switch 26, 27 is again closed, current is fed through a wire 33 to the opposite side of the motor 2, which rotates reversely, to wind-up the spring 4 and, the electromagnet 9 having been re-energized, the clutch pin 12 ultimately re-engages its hole 13 and the limit switch 29 is automatically opened, thus restoring the position shown in Fig. 2. In a modified construction, Fig. 6 (not shown), spring return of the driven shaft to its initial position is retarded by the aerodynamic resistance to rotation of a fan, driven through a train of gears and a helical spring ratchet clutch.