GB636171A - Improvements in electric actuators - Google Patents

Abstract

636,171. Electric actuators. MILES AIRCRAFT, Ltd., HUNT, C. L., and HAWKINS, A. S. Oct. 19, 1944, Nos. 25959/45 and 25960/45. Divided out of 627,005. [Class 78 (iii)] [Also in Group XXXVII] An electric actuator intended primarily for the operation of component parts of aircraft is provided with means for automatically discontinuing the drive to the output member after a predetermined travel thereof and with means for reversing the direction of travel of this member. These means are especially applicable to the actuator described in Specification 627,004. The hollow output member 5, Fig. 1, has a projection 36 which engages a limit switch 35 at each end of the stroke. These switches form the subject-matter of Specification 636,216, [Group XXXVII]. In a modification, Figs. 9 and 12, contacts 421, 431 are mounted on blades 44, 45 of which the former protrudes into the path of the projection 36. In a further modification, Fig. 8, a switch is shown which is interposed in the connections of the motor 2 so as to cause reversal when it is actuated. Spring blades 48, 481 each carrying a pair of contacts 49, 491 are mounted on an insulating rocker arm 47 which is moved to either position by a hinged strut 56 engaged by a slide 59. The blades are connected by hairpin springs 52 to terminals 53, 531 so that in one position of the switch contacts 50, 511 are connected to these terminals and in the other position contacts 51, 50<SP>1</SP> are connected thereto. The member 5 has helical grooves formed in its internal surface to receive a series of balls 8 which also engage in similar grooves 7 formed on a spindle 6. This spindle is connected to the motor 2 through epicyclic or other reduction gearing 3 and a solenoid actuated'clutch 11, 12 having dog teeth 13. Means is provided for preventing rotation of the member 5. Current passes through the windings of a solenoid 14 to maintain the part 11 in driving connection whether or not current is passing through the windings of the motor. The drive is disconnected when current fails by a spring 15. The tubular part 4 in which the member 5 moves is fitted with shock absorbers 22 for limiting the movement. The force exerted by the actuator is limited by a friction band 25 which surrounds the internally toothed annulus 24 of the gearing 3 and is adjusted by means 25<SP>1</SP> to slip under a predetermined load. The motor is provided with an electric brake 26, the windings of which are so interconnected with the motor windings that it is applied when the motor comes to rest and is released when it is started. The spindle 28, Fig. 4, of the motor armature carries a brake disc 29 which co-operates with a disc 30 slidably but non-rotatably mounted on the spindle and forming an armature of the solenoid 32. A spring 31 forces the discs into contact.