Patent GB-818024-A (GB)
Title: Cam clutch device
IPC: B25B23/14
Filed: 1957-05-16
Abstract: 818,024. Positive clutches. CHICAGO PNEUMATIC TOOL CO. May 16, 1957 [July 30, 1956], No. 15568/57. Class 80 (2). In a combination of a torque-responsive clutch with a secondary clutch, automatic means separate the driving and driven elements of the secondary clutch as the torque-responsive clutch re-engages. A power screwdriver has a drive spindle 32 splined to a tubular drive-shaft 36 on which are carried driving and driven clutch-plates 54,..55.-which are, respectively, axially free and rotatably free on the shaft 36. Between the clutch plates and located in a cage 76 is a series of balls 74 forming with pockets 73, 75 a ball cam clutch, axially loaded to disengage at predetermined torque by a spring 66 abutting the clutch-plate 54 and an adjustable stop 67 threaded on the drive-shaft 36. The lower face of the clutch-plate 55 is formed with dog teeth engageable with complementary teeth on a driven clutch-plate 56, this secondary clutch being urged into engagement by a spring 82 located between the plate 56 and a plate 83 located on a driven shaft 45 by a spring ring 84. The driven shaft 45, which is adapted to receive a tool at its lower end 47, has a longitudinal slot 88 to receive a driving key 87 which also seats in a slot 89 in the driven plate 56; the key is retained for axial movement in the shaft 45 by a spring-ring 93 and has a lug 86 which engages an internal shoulder 85 in the plate 56. Within the bore of the drive-shaft 36 and the driven shaft 45 is carried a quill shaft 42 having a reduced diameter upper portion 112 over which is located, for limited axial movement by a ball in a slot 120, a lock-out sleeve 109 urged downwardly by a spring 111, and carrying a radial pin 106 projecting through a slot 107 in the drive-shaft 36 to rest on a cup washer 105 on the upper face of the boss of clutch-plate 54. The portion 112 has three radial holes containing balls 114 which can be urged inwardly by a camming chamfer on the lower end of sleeve 109 and outwardly by a chamfer 117 on a lockout plunger 102 within the bore of the quill shaft 42. The quill shaft 42 has a shoulder 43 which can abut the lower end of the drive-shaft 36 and slides within a recess in the upper end of the driven shaft 45, this shoulder also engages an inwardly-projecting shoulder on the key 87. The quill shaft 42 is urged upwardly by two disengaging springs 95, 104 acting respectively between a shoulder 101 on the lock-out plunger 102 and a stop-ring 96 seating on a thrust collar 97 secured within the driven shaft 45, and the shoulder 101 and the end of the reduced bore of the quill shaft. Operation.-In the initial condition the driven shaft 45 is held downwardly by the springs 95, 104 and the clutch driven plate 56 is held disengaged through the action of the spring ring 93 and the key 87; rotation of the spindle 32 imparts rotation through the shaft 36, balls 64, driving plate 54 and ball cam-clutch 73, 74, 75 to the clutch plate 55. Pressure on the casing to engage the tool head 47 with the work-piece moves the driven shaft upwards together with the spring plate 83, spring 82, key 87 and clutch plate 56 to engage the clutch 56, 55 and also to compress the disengaging springs 95, 104 and start the lock-out plunger 102 on its upward movement. The plunger 102 moves until it is held by the engagement of the chamfer 117 with the balls 114 which cannot move radially outwards due to the locking sleeve 109. Under these conditions drive is imparted to the tool head 47. When the work is tightened to the predetermined torque, the ball cam clutch 54, 74, 55 disengages against the spring 66 and clutch plate 54 moves upwards as the balls 74 ride from the recesses 73, 75, this moves the cupped washer 105, pin 106 and the lockout sleeve 109 upwards and allows the lockout plunger 102 to move the balls 114 radially outwards to lock the quill shaft to the sleeve 109. As the clutch plates 54, 55 continue to rotate relatively, the recesses 73, 75 re-align and allow the plate 54 to move downwards, whereupon the spring 111 urges the lockout sleeve 109, balls 114, quill shaft 42 and key 87 downwards to disengage the dog clutch 55, 56 and stop the drive to the tool head 47. Removal of the tool head from the workpiece allows the driven shaft 45 to move downwards under the action of 104, 95 which causes the lock-out plunger 102 to move downwards until the chamfer 117 cleans the balls 114 to permit them to move radially inwards, whereupon the chamber on the lockout sleeve 109 cams the balls 114 out of engagement with the sleeve. Quill shaft 42 is thus released and moves upwards under springs 104, 95 to allow reengagement of the dog clutch, which restores the mechanism to its starting condition. The trailing edges of the recesses 73, 75 are slightly radiused to provide a lower separating torque in the forward drive condition than in reverse drive. In a modification, the recesses 73, 75 are joined by an arcuate annular groove to form tracks for the balls 74, and the cage 76 is omitted. In a second embodiment, Fig. 28a, upward movement of the tool head 164 produces engagement of a dog clutch 159, 157 and upward movement of a lock-out plunger 174, spring 173 and a lock-out sleeve 178 until the latter is stopped by engagement with balls 182 which are prevented from radial movement by the driving plate 139 of a ball cam clutch 139, 142, 137. On attainment of the predetermined torque, the driving plate 139, which is driven from a motor shaft 133 through a driving cup 134 having fingers 138 fitting grooves in the periphery of clutch plate 139, moves downwards under the cam action of the balls 142, against a spring 143, to disengage the drive. As the plate 139 moves it allows the balls 182 to move radially outwards under the action of a chamfer on the lock-out sleeve 178 into.recesses 184 in the plate, and so lock the plate to a quill shaft 151 carrying the dogclutch member 156. As the ball cam clutch re-engages, the quill shaft 151 moves upwards to disengage the clutch 156, 159 and disconnect the drive. Removal of the tool from the workpiece allows the lock-out pin 174 to move downwards, taking with it the lock-out sleeve 178 and freeing the balls 182 from the clutch plate 139. The dog clutch member 156 and quill shaft 151 then move downwards under the action of a spring 162 to reset the mechanism to its starting condition.