Abstract: An electrically-controlled force-exerting actuator comprising a force-applying power spring arranged to exert a force on an output member, a force-applying control spring arranged with respect to the power spring such that the force exerted by the control spring is detracted from the force exerted by the power spring to determine the residual force exerted on the output member by the power spring, and an electric motor operable to vary the detractive force exerted by the control spring.

Abstract: An electric actuator having an output member movable into and out of a force-exerting position, electric motor means operable both to move the output member to and from its force-exerting position and, when the output member is in that position, to control a spring system to generate a required output force on the output member, and means for withholding the spring system from generating a force on the output member until the output member is determined as being in its force-exerting position.

Abstract: An electric actuator having an electric motor operable to determine the output force generated on an output member by a spring system, and an adjustable stop by which can be limited the maximum value of the output force, the position of the adjustable stop being variable in accordance with variation of the required maximum value of the output force to be exerted by the output member.

Abstract: The present invention provides an electric actuator having an output member movable from a first variable position to a second variable position; an electric motor operable to control a spring system to exert an output force on the output member when in its second position; a device for generating an electrical signal when the output member is about to leave the second position as it returns to the first position; and a motor-control electrical circuit which recognizes the generation of the electrical signal and thereafter operates the electric motor to a pre-determined degree to move the output member a corresponding pre-determined distance back to the first position so that there is preserved a substantially constant distance between the first and second positions.

Abstract: An electric actuator which comprises an electric motor operable to a varying degree correspondingly to cause a spring to generate on an output member an output force which varies in accordance with the varying degree of operation of the electric motor.

Abstract: An electric actuator having an electric motor operable to control the output force generated by a spring system of the actuator on an output member of the actuator; measuring means responsive to a characteristic of the spring system which is indicative of the value of the output force; and an electrical circuit by which operation of the electric motor can be initiated and can be terminated when the measuring means detects the characteristic as being indicative of the output force of a required value.

Abstract: An electric actuator which comprises an electric motor operable to a varying degree correspondingly to cause a spring to generate on an output member an output force which varies in accordance with the varying degree of operation of the electric motor.