GB979487A - A new or improved overload clutch or torque limiting device - Google Patents

Abstract

979,487. Overload release clutches; controlling clutches. FISHER & LUDLOW Ltd. April 6, 1961 [April 14, 1960 ; May 31, 1960], Nos. 13506/60 and 19148/60. Headings F2C and F2L. An overload release clutch for conveyers &c. comprises a driving pulley 11, Fig. 1, mounted for axial and rotary movement on a sleeve 13 fast with a driven shaft 14, a spring 15 biasing the driving pulley to engage holes 17 therein with torque transmitting balls 19 also engaging holes 18 in a disc 12 secured to the driven shaft, a ball-retaining disc 20 carried by the driven disc having inclined slots 21, Fig. 4, through which the balls pass, the inner ends 21a of the slots being at the same radial distance from the clutch axis as the ball-receiving holes 17, 18. On overload, the balls 19 ride out of the holes 17, 18 in the driving pulley 10 and the driven disc 12, and roll along to the ends 21b of the inclined slots 21 in the retaining disc 20, where they are held radially outwards of the holes. To re-engage the clutch, the drive pulley 10 is brought to rest and then turned backwards. The ball-retaining disc 20 may be removed, reversed and put back with the slots 21 directed in the opposite circumferential sense, to enable the clutch to be used when the driving pulley 11 turns in the other direction. The spring 15 biasing the pulley 10 to the clutch engaging position acts through an axially slidable plate 16 which, when the clutch disengages on overload, engages a cam roller 28 to open a switch 26 and stop an electric motor driving the pulley 11. To enable the clutch to be held engaged when the torque loading applied to the shaft 14 exceeds that at which the balls 19 would move to the disengaged position, as when starting the drive, a lock roller 32, Fig. 7, on the end of a lever 29 may be projected by energization of a solenoid 33 to engage the back of the plate 16. The solenoid 33 may be in circuit with the driving electric motor and the arrangement may be such that the solenoid is energized when the motor is first switched on, but de-energized as soon as the motor reaches its normal operating speed, the roller 32 and the lever 29 then falling to a position clear of the plate 16. The lever 29 itself pivots on a lever 31 supporting the solenoid 33 and pivoting on a fixed bracket at 37, a spring 39 yielding to allow clutch disengagement by turning of the lever 31 if a substantial overload is applied to the driven shaft 14 while the lock roller 32 is held in engagement with the plate 16. In a modified form, not shown, a further ball-retaining plate having radial slots through which the balls 19 pass lies beside the disc 20 and can turn relatively thereto.