System for controlling an electromechanically reciprocable load

Claim 1

A system for selectively reciprocating a load between a retracted position and a working position, comprising: spring means mechanically coupled with said load for driving same in a forward stroke from said retracted position to said working position, said spring means being under a maximum stress in the retracted position of said load; a rotary electric motor operatively coupled with said load and provided with an energizing circuit for exerting thereon a countervailing force opposing the driving force of said spring means; control means in said energizing circuit for modifying said countervailing force in response to external commands for yieldingly resisting said driving force during a forward stroke and for overriding said driving force in a return stroke, said control means including a position sensor in the form of a first potentiometer having a wiper entrainable by said load for progressively reducing said countervailing force in the course of a forward stroke in substantial conformity with the progressive diminution of said driving force due to relaxation of the stress of said spring means, said first potentiometer constituting part of a bridge circuit with a first diagonal defined by said wiper and by a reference point, said control means further comprising a switching circuit connected across said first diagonal and a power supply connected across a second diagonal of said bridge circuit for energizing said motor in an unbalanced state of said bridge circuit, said motor being provided with brake means for immobilizing same in a balanced state of said bridge circuit, said brake means being releasable by an external command initiating a forward stroke, said reference point being a wiper of a second potentiometer connected in parallel with the first potentiometer across said second diagonal, said load including an actuating member of a power brake with linings subject to wear; and a lost-motion coupling between said wipers, the wiper of said second potentiometer being entrainable by said actuating member through said lost-motion coupling with a lag relative to the wiper of said first potentiometer establishing a balanced state of said bridge circuit in positions along said potentiometers advancing with progressive wear of said linings whereby even application of the brake is ensured with such wear.

Claim 2

A system for selectively reciprocating a load between a retracted position and a working position, comprising: spring means mechanically coupled with said load for driving same in a forward stroke from said retracted position to said working position, said spring means being under a maximum stress in the retracted position of said load; a rotary electric motor operatively coupled with said load and provided with an energizing circuit for exerting thereon a countervailing force opposing the driving force of said spring means; control means in said energizing circuit for modifying said countervailing force in response to external commands for yieldingly resisting said driving force during a forward stroke and for overriding said driving force in a return stroke, said control means including a position sensor in the form of a first potentiometer having a wiper entrainable by said load for progressively reducing said countervailing force in the course of a forward stroke in substantial conformity with the progressive diminution of said driving force due to relaxation of the stress of said spring means, said first potentiometer constituting part of a bridge circuit with a first diagonal defined by said wiper and by a reference point, said control means further comprising a switching circuit connected across said first diagonal and a power supply connected across a second diagonal of said bridge circuit for energizing said motor in an unbalanced state of said bridge circuit, said motor being provided with brake means for immobilizing same in a balanced state of said bridge circuit, said brake means being releasable by an external command initiating a forward stroke, said reference point being a wiper of a second potentiometer connected in parallel with the first potentiometer across said second diagonal, said load including an actuating member of a power brake with linings subject to wear; and a lost-motion coupling between said wipers, the wiper of said second potentiometer being entrainable by said actuating member through said lost-motion coupling with a lag relative to the wiper of said first potentiometer establishing a balanced state of said bridge circuit in positions along said potentiometers advancing with progressive wear of said linings whereby even application of the brake is ensured with such wear.

Claim 7

A system for selectively reciprocating a load between a retracted position and a working position, comprising: spring means mechanically coupled with said load for driving same in a forward stroke from said retracted position to said working position, said spring means being under a maximum stress in the retracted position of said load; a rotary electric motor operatively coupled with said load and provided with an energizing circuit for exerting thereon a countervailing force opposing the driving force of said spring means; and control means in said energizing circuit for modifying said countervailing force in response to external commands for yieldingly resisting said driving force during a forward stroke and for overriding said driving force in a return stroke, said control means including a position sensor in the form of a first potentiometer having a wiper entrainable by said load for progressively reducing said countervailing force in the course of a forward stroke in substantial conformity with the progressive diminution of said driving force due to relaxation of the stress of said spring means, said first potentiometer constituting part of a bridge circuit with a first diagonal defined by said wiper and by a reference point, said control means further comprising a switching circuit connected across said first diagonal and a power supply connected across a second diagonal of said bridge circuit for energizing said motor in an unbalanced state of said bridge circuit, said motor being provided with brake means for immobilizing same in a balanced state of said bridge circuit, said brake means being releasable by an external command initiating a forward stroke, said reference point being a wiper of a second potentiometer connected in parallel with the first potentiometer across said second diagonal, said load including an actuating member of a power brake coacting with a rotary element for arresting same in said working position, said control means including accelerometer means coupled with said rotary element for temporarily increasing said countervailing force in response to a rate of deceleration exceeding a predetermined threshold in a final phase of said forward stroke.

Claim 8

A system for selectively reciprocating a load between a retracted position and a working position, comprising: spring means mechanically coupled with said load for driving same in a forward stroke from said retracted position to said working position, said spring means being under a maximum stress in the retracted position of said load; a rotary electric motor operatively coupled with said load and provided with an energizing circuit for exerting thereon a countervailing force opposing the driving force of said spring means; and control means in said energizing circuit for modifying said countervailing force in response to external commands for yieldingly resisting said driving force during a forward stroke and for overriding said driving force in a return stroke, said control means including a position sensor in the form of a first potentiometer having a wiper entrainable by said load for progressively reducing said countervailing force in the course of a forward stroke in substantial conformity with the progressive diminution of said driving force due to relaxation of the stress of said spring means, said first potentiometer constituting part of a bridge circuit with a first diagonal defined by said wiper and by a reference point, said control means further comprising a switching circuit connected across said first diagonal and a power supply connected across a second diagonal of said bridge circuit for energizing said motor in an unbalanced state of said bridge circuit, said motor being provided with brake means for immobilizing same in a balanced state of said bridge circuit, said brake means being releasable by an external command initiating a forward stroke, said reference point being a wiper of a second potentiometer connected in parallel with the first potentiometer across said second diagonal, said load including an actuating member of a power brake coacting with a rotary element for arresting same in said working position, said control means including accelerometer means coupled with said rotary element for temporarily increasing said countervailing force in response to a rate of deceleration exceeding a predetermined threshold in a final phase of said forward stroke.