US 4,040,445 AGranted

Electrical linear force motor for servo controls, fluid valves, and the like

AssigneeMurray A. Ruben

InventorJoseph F. McCormick

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Abstract

The invention relates to an electro-mechanical force motor device for converting a controlled electrical input signal into a mechanical movement, particularly for actuation of a hydraulic pilot or servo device. The basic component of the invention is a linear electric force motor with its principal components coaxially disposed and arranged to achieve linear mechanical displacement in accordance with an applied signal of voltage. The armature or coil element of the linear force motor is coupled to a double-acting bellows, which not only serves as a double-acting return spring, but also totally isolates the magnetic and electro magnetic elements of the force motor from the controlled system. This is of particular significance in connection with the electro-hydraulic pilot and servo devices, for example, in which the circulating hydraulic fluid inevitably contains suspended magnetic particles which otherwise can eventually accumulate on the magnetic components of the force motor and impede its normal functioning.

Claims11

Dependent claims

A two-way, linear proportional force motor unit for directly operating an hydraulic utilization device, comprising

a. a permanent magnet connected to magnetic pole pieces and defining an air gap containing a permanent magnetic flux,
b. an electrical winding in said air gap,
c. a mechanical coil support for said electrical winding,
d. a balanced, prestressed, double-acting resilient metallic bellows
e. said mechanical coil support being connected to said bellows at its effective midpoint from without said bellows whereby said electrical winding is external of said bellows,
f. said bellows being prestressed in an amount greater than the operating displacement of said mechanical oil support, whereby said bellows is unidirectionally stressed at all times under normal working conditions,
g. operator means projecting coaxially of the bellows within the confines of said bellows to an exterior point for connection to said utilization device and operatively associated with said mechanical coil support,
h. said bellows being sealed at one end and in sealed communication at its other end with said hydraulic utilization device, whereby said bellows serves to isolate said air gap from the fluid of said hydraulic utilization device independently of sliding-type seals.

5 more elements

A two-way, linear proportional force motor unit for directly operating an hydraulic utilization device, comprising

a. a force motor housing,
b. an hydraulic utilization device connected to said housing,
c. operator means for said hydraulic utilization device extending through said housing and movable relative thereto for activating said utilization device,
d. means in said force motor housing forming a magnetic air gap,
e. an electrical winding movable axially in said air gap,
f. the axes of said air gap and electrical winding being parallel to the effective axis of said operator means,
g. a balanced, prestressed, double-acting resilient metallic bellows supported at its ends in said force motor housing,
h. means mechanically connecting said electrical winding to the effective midpoint of said bellows whereby upon energization of said winding said midpoint will be displaced axially through a distance and in a direction which is substantially a linear function of the electrical current energizing said winding,
i. said bellows being initially prestressed in an amount greater than the maximum intended displacement of said midpoint, whereby said bellows remains under at least limited prestress in all normal operating positions,
j. that portion of said operator means extending within said housing, being entirely within the confines of said bellows and being connected to said bellows midpoint from within the said bellows and said electrical winding being connected to said midpoint outside said bellows, and
k. said bellows, at its ends, being in sealed relation to said force motor housing, whereby said air gap and electrical winding are completely isolated from said hydraulic utilization device.

8 more elements

Dependencies are inferred from the claim text.