Patent GB-738813-A (GB)
Title: Improvements in apparatus for controlling the drive of conveyor belts
Inventor: WALKER DANIEL NORMAN
IPC: B65G43/04
Filed: 1951-11-16
Abstract: 738,813. Gearing for stopping and starting machinery. COAL INDUSTRY (PATENTS), Ltd. Feb. 16; 1953 [Nov. 16, 1951], No. 26899/51. Class 80 (2). [Also in Group XXX] Control apparatus for a belt conveyer comprises a differential gear driven on one input side by the belt itself and on the other by the driving drum or by the gear driving said drum, the differential sum of these two speeds being used to rotate a centrifugal governor which under the influence of a predetermined degree of slip of the belt actuates a timing mechanism which is connected to a trip device when the timing mechanism has been actuated for a predetermined period of time, the trip device serving to interrupt the drive of the belt. In Fig. 1, the gear 3 of a differential is driven from the belt 1 by a flexible drive 5 and a friction drive 4, whilst the gear 6 of the differential is driven from the belt drum 2 or the gearing driving the drum by a shaft 8 and a friction drive 7. The differential crown wheel 9 drives through a gear 12 and shaft 11 a a centrifugal governor 10 comprising a pair of weights 13 connected by a spring 16 and pivotally mounted at 14 on a sleeve 15 free to move along the shaft 11 but splined to cooperate with splines on the shaft 11 so as to be driven thereby. The sleeve 15 is connected to a lever 17 pivotally mounted at 18 and connected by a link 19 to a bearing 22 supporting one end of a shaft 20 mounted in a rocking bearing 21. The other end of the shaft 20 carries a friction wheel 23 engageable with a friction wheel 24 on the shaft 8. When slip occurs between the belt 1 and drum 2, the gear 3 lags with respect to the gear 6, and the wheel 9 is rotated at a speed proportional to the slip. This causes rotation of the shaft 11 and when the slip reaches a predetermined amount, the weights 13 move outwardly causing the sleeve 15 to slide along the shaft 11 to rock the lever 17 and the shaft 20 so as to move the friction wheel 23 into engagement with the wheel 24 and be driven thereby. A spring 25 of a timing mechanism connected to a shaft 26 is then wound up. When this is fully wound, the drive is transmitted by a drum 27, to which the spring is secured at its outer end, to a pinion 28 and shaft 29 so as to move a contact 31 into engagement with a contact 32 and complete a circuit 33 to operate a relay 35 and disconnect the drive to the belt 1 and operate a visual and/or audible alarm. In a modification, Fig. 2, the link 19 of the centrifugal governor is connected to the free end of a push rod 37 pivoted at 38 to a rocking arm 39 pivotally mounted at 40. The rod 37 is normally clear of an eccentric 36 on the shaft 8 as shown in broken line, but on the occurrence of a predetermined degree of slip, the link 19 rocks the rod into engagement with the eccentric and at the same time a detent 44 is lowered to engage a ratchet wheel 42 of the timing mechanism. The shaft 8 through the eccentric 36 operates a pawl 41 through the arm 39 so as to rotate the wheel 42 step-by-step against its spring 43. If the predetermined degree of slip persists for a predetermined period, the wheel 42 is fully rotated to operate a relay or trip as in Fig. 1.