GB743258A - Improvements in or relating to means for indicating faults on electrically driven belt conveyor systems - Google Patents

Abstract

743,258. Endless belt conveyers. WOOD & CO., Ltd., H. Dec. 17, 1953 [Dec. 17, 1952], No. 31964/52. Class 78 (1). A belt conveyer includes various faultindicating devices, responsive e.g. to belt slip, excessive temperature, a torn belt, and to material on the underbelt, each of these devices, except that for belt slip, operating a switch 2, 3 or 4 as a result of a fault to close the circuit of an indicator A<SP>1</SP>, B<SP>1</SP>, C<SP>1</SP>, and each switch in its non-operative position closing contacts in series with one another and with a common relay E, whereby when any device other than that responsive to belt slip operates, the relay is de-energized and prevents operation of the belt slip indicator. As shown, the belt slip indicator comprises a switch BP<SP>1</SP> electromagnetically closed by the voltage from a generator driven from a belt idler and adapted to open whenever the speed falls below a predetermined value. The motor circuit MC is broken if either relay E is de-energized through contacts E<SP>3</SP>, or relay H is de-energized by the opening of switch BP<SP>1</SP> through contacts H<SP>2</SP>, contacts G normally being open. If switch BP<SP>1</SP> is opened owing to belt slip without previous operation of the other fault indicating devices, the motor circuit MC will be broken and, as the belt comes to rest, a motionresponsive switch K will close, energizing a lock-off relay J through contacts H<SP>1</SP> and G<SP>1</SP> (the latter being normally closed) and opening contacts J<SP>3</SP> in circuit MC and holding itself in over contacts J<SP>1</SP>. Contacts J<SP>2</SP> also open in the circuit of a delay starter switch DS. Belt slip indicator D<SP>1</SP> is illuminated through normally closed contacts E<SP>1</SP> of relay E. If any of the other fault-indicating devices is operated before the belt slip indicator, contacts E<SP>1</SP> open preventing indicator D<SP>1</SP> from being illuminated when the belt slows down owing to opening of contacts E<SP>3</SP> in circuit MC. The closure of contacts E<SP>2</SP> of relay E ensures relay J being energized in case switch BP<SP>1</SP> does not open when the belt stops. To restart the conveyer after the fault has been rectified, relay E being reenergized, relay J must be de-energized by a re-set switch 9, contacts 9a of which open whilst the contacts 8 close, energizing a test relay F. The latter closes contacts F<SP>1</SP>-F<SP>4</SP> in all indicating circuits to check that the indicators are working. Switch DS is now pressed, this having a delayed opening of twenty seconds, whereby relay G remains energized until the belt has run up to speed. The closing of contact G<SP>2</SP> re-energizes motor circuit MC while the opening of contacts G<SP>1</SP> prevents re-energizing of relay J so that switch 9 may be released. Before contacts G<SP>2</SP> re-open owing to contacts DS opening, switch BP<SP>1</SP> is closed so that contacts H<SP>2</SP> maintain the circuit MC closed.