Positive limit control for motorized drive units

Claim 1

A CONTROL SYSTEM FOR A REVERSIBLE MOTOR COMPRISING AN AMPLIFIER HAVING A PAIR OF OUTPUT SIGNAL CHANNELS RESPECTIVELY TERMINATING IN SWITCHING MEANS FOR SELECTIVE ENERGIZATION OF THE MOTOR IN CORRESPONDING DIRECTION FROM A POWER LINE, POLARITY-SENSITIVE MEANS FOR DIRECTING THE OUTPUT SIGNAL OF SAID AMPLIFIER TO ONE OR THE OTHER OF SAID CHANNELS IN DEPENDENCE UPON THE POLARITY OF SAID OUTPUT SIGNAL, MEANS IN THE INPUT SYSTEM OF SAID AMPLIFIER FOR PRODUCING A FIRST AMPLIFIER-OUTPUT SIGNAL COMPONENT HAVING A POLARITY CHARACTERISTIC NORMALLY DETERMINATIVE, AS DIRECTED BY SAID POLARITY-SENSITIVE MEANS TO A CORRESPONDING ONE OF SAID CHANNELS, OF THE SENSE OF ENERGIZATION OF SAID MOTOR FOR ROTATION THEREOF IN A SELECTED DIRECTION, MEANS IN THE INPUT SYSTEM OF SAID AMPLIFIER EFFECTIVE UPON ENERGIZATION OF THE MOTOR TO PRODUCE A SECOND AMPLIFIER-OUTPUT SIGNAL COMPONENT IN OPPOSITION TO SAID FIRST SIGNAL COMPONENT AND NORMALLY DAMPING ITS SPEED IN THE SELECTED DIRECTION, AND MEANS INCLUDING LIMIT SWITCHES ACTUATED AS THE MOTOR APPROACHES EITHER LIMIT OF ITS TRAVEL EFFECTIVELY TO ELIMINATE SAID FIRST COMPONENT OF THE AMPLIFIER-OUTPUT SIGNAL TO PRECLUDE FURTHER ENERGIZATION OF THE MOTOR IN THE SELECTED SENSE, AND, BY ROUTING OF THE REMAINING SECOND COMPONENT OF THE AMPLIFIER-OUTPUT SIGNAL TO THE OTHER OF SAID CHANNELS BY SAID POLARITYSENSITIVE MEANS, TO PROVIDE FOR REVERSE ENERGIZATION OF THE MOTOR TO BRING IT QUICKLY TO REST.