GB599450A - Improvements in or relating to mechanical actuator mechanism - Google Patents

Abstract

599,450. Operating clutches. STEVENS, A. H. (Lear, Inc.). July 17, 1945, No. 18259. [Class 80(ii)] [Also in Groups XXX and XXXIII] In a mechanical actuator, especially for operating the landing hook of a carrier based aircraft, excess torque responsive means are provided to substantially instantaneously arrest the motion when the moving member reaches either of the limiting points, and a drum and cable mechanism is provided for alternative actuation. An electromagnetic clutch 35, as described in Specification 549,552 has a driving disc 31 secured to the driving shaft of a motor 30, and an axially slidable driven disc 33 normally urged against a braking surface 38 by a spring 37. The disc 33 has a pinion 36 engaging with the gears 41 rotatable on the shafts 51 which are secured to a movable mounting plate 42. Rigid with the gears 41 are pinions 43 which engage with an annulus 44, supported in the bearing 46, and having a shaft extension 52 carrying a pinion 53 which, through the countershaft gears 83,84, 85, 87, drives a shaft 88 having a sprocket 11 keyed thereto. A chain 14, Fig. 1, driven by sprocket 11 and supported by a sprocket 12 carries the landing hook 15. The movable plate 42, Fig. 3, has teeth 54 engaging with the teeth 56 on a sector 57 pivoted on a shaft 60 and having a roller 77 which contacts the push-buttons 78 or 80 when the sector moves to its extreme position at either side. Springs 68, 70 having adjusting means 71, 73 and 72, 74 locked by the nuts 75, 76, respectively, urge the sector to a central position. Operation of a push-button 16 in the aircraft cockpit energises the motor and clutch, which are in the same circuit, and causes rotation of the pinion 36 and hence the sprocket 11 to extend the hook 15. When the hook 15 reaches its limit of travel the increase in torque on the gears 41, 43 causes the plate 42 and sector 57 to move against the loading of the spring 68 or 70 whereupon the roller 77 contacts either push-button 78 or 80 to break the clutch and motor circuit. As soon as the circuit is broken, the clutch 35 frees to eliminate the armature inertia, and the spring 37 forces the disc 33 against a braking surface 38 to stop rotation of the gear trains and the sprocket 11. Operation of the button 17 energises the motor to rotate in the reverse direction to retract the hook. The push-buttons 16, 17 act through electrical relays having holding circuits to maintain operation of the motor until the circuit is broken by the respective bush-button 78 or 80, a warning light circuit is also included to show when the hook is extended. Manual operation of sprocket 11 is provided by a cable 26 wound on a drum 107 freely mounted on a shaft 100 supported in shaft 88 at one end and secured to bracket 97 at the other. A spring, fixed to a member 108, rigid with bracket 97, and to the drum 107 rewinds the cable during the return period; unidirectional drive, on pulling cable 26, being imparted to a ratchet 112 on the boss 111 of the sprocket 11 through a pawl 113 pivoted on the drum 107.