US 4,048,886 A · Brake monitor with self-checking

Abstract

A monitoring system is disclosed for measuring and classifying the decelerating capabilities of a machine, such as a punch press. The monitoring system includes a timing circuit for measuring the elapsed time from the initiation of brake application to the stopping of the press. Means are provided to distinguish between a regular top-stop in a single stroke press cycle from an emergency stop and to shut down the press if the stopping time is excessive for the type of stop being executed. The monitoring means is provided with a self-checking system which performs dynamic self-checking at the initiation of braking, at the stopping of the press, and at the initiation of clutching. In each self-checking cycle a fault simulating signal is propagated through two independent paths or through a path which has been previously checked. The fault simulating signal will cause the press to be shut down unless it causes a control signal to change from an enabling state to a disabling state and back to the enabling state in less time than that required for the actuation of the relay means for shutting down the press.

Claims22

Dependent claims

A brake monitor for a press having clutch means, brake means and control means for alternately starting and stopping the press crank in a cycle of operation, said monitor comprising:

a signal circuit adapted to be connected with the press to produce a brake signal at the start of braking, a timing circuit responsive to the brake signal for generating a timing signal having a value which is a function of time, said signal circuit being connected with the timing circuit for starting the timing signal, detecting means connected with the timing circuit for producing logic signals indicative of the value of the timing signal relative to reference signals representing stopping times for the press, motion stop detecting means adapted to be connected with the press for generating a motion stop signal when the press comes to a stop, memory means connected with the detecting means for storing said logic signals in response to a motion stop signal, a relay circuit adapted to be connected with said control means of the press for shutting down the press in response to a disabling signal, and logic means connected to said memory means and producing a disabling signal when said logic signals represent a timing signal indicative of excessive stopping time, said logic means being connected with the relay circuit to apply the disabling signal thereto for shutting down the press when the stopping time is excessive.

A brake monitor for a press having clutch means, brake means and control means for alternately starting and stopping the press crank in a cycle of operation, said monitor comprising;

condition signalling means including a brake signal circuit adapted to be connected with the press to produce a brake signal at the start of braking and motion stop detecting means adapted to be connected with the press for generating a motion stop signal when the press comes to a stop, timing means connected with the brake signal circuit and with the motion stop detecting means and being responsive to said brake signal and to said motion stop signal for measuring the elapsed time therebetween, relay means adapted to be connected with the control means of the press for shutting down the press when the relay means are actuated from one condition to another, said relay means including control signal responsive means for receiving plural control signals, each of the control signals being changeable from an enabling state to a disabling state and vice versa, actuation of the relay means being initiated by any one of said control signals being in the disabling state, logic means connected to the timing means and to the control signal responsive means and producing a first control signal, said first control signal being in a disabling state when the elapsed time exceeds a predetermined value and being in an enabling state when the elapsed time is less than said predetermined value, said logic means including disabling means connected with the condition signalling means for forcing the first control signal to change to the disabling state, restoring means connected with the disabling means for forcing the first control signal to change back to the enabling state within a time delay which is less than the time required for actuation of the relay means, said logic means including checking means responsive to said first control signal for producing a second control signal in a disabling state unless the first control signal changes to the disabling state and back to the enabling state within said time delay in response to the condition signalling means.

A brake monitor for a press having clutch means, brake means and control means for alternately starting and stopping the press crank in a cycle of operation, said monitor comprising:

condition signalling means including a clutch-brake signal circuit adapted to be connected with the press to produce a brake signal at the start of braking and to produce a clutch signal at the start of clutching and motion stop detecting means adapted to be connected with the press for generating a motion stop signal when the press comes to a stop, timing means connected with the clutch-brake signal circuit and the motion stop detecting means and being responsive to said brake signal and to said motion stop signal for measuring the elapsed time therebetween, relay means adapted to be connected with the control means of the press for shutting down the press when the relay means are actuated from one condition to another, said relay means including control signal responsive means for receiving plural control signals, each of the control signals being changeable from an enabling state to a disabling state and vice versa, actuation of the relay means being initiated by any one of said control signals being in the disabling state, logic means connected to the timing means and to the control signal responsive means and producing a first control signal, said first control signal being in a disabling state when the elapsed time exceeds a predetermined value and being in an enabling state when the elapsed time is less than said predetermined value, self-checking means including a disabling signal circuit in said logic means connected with the conditon signalling means and forcing the first control signal to said disabling state in response to at least a selected one of the signals produced by the condition signalling means to initiate actuation of the relay means, a time delay latch connected with said relay means and responsive to initiation of actuation of the relay means for producing, after a first predetermined time delay, a second control signal latched in a disabling state, a restoring circuit in said logic means and producing a restoring signal following said selected one of the signals by a second predetermined time delay, said restoring circuit being connected with said disabling signal circuit and forcing the first control signal to change to said enabling state, said second predetermined time delay being shorter than said first predetermined time delay and being less than the time required for actuation of the relay means, whereby said time delay latch will not produce the second control signal if the disabling signal circuit is operative and the first control signal changes to said enabling state within said second predetermined time delay.

Dependencies are inferred from the claim text.

Brake monitor with self-checking

Life of this patent

Brake monitor with self-checking

Life of this patent

Abstract

Claims22