US2869048A - Electromagnetic device - Google Patents

Description

Jan. 13, 1959 G. REED 2,869,048

ELECTROMAGNETIC DEVICE Filed May 18, 1953 35 INVENTOR.

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United States Patent ELECTROMAGNETIC DEVICE Gabriel Reed, London, England, assignor to Ultra Electric, Inc., Wilmington, Del., a corporation of Delaware Application May 18, 1953, Serial No. 355,424

Claims priority, appiication Great Britain May 22, 1952 3 Claims. (Cl. 317-165) This invention relates to an improved electromagnetic device, of the kind comprising a fixed magnetic member (stator) cooperating with a movable magnetic member (armature) and excited by a solenoid to produce movement of the said armature against a load force, for example a force exerted by a spring, and in which the said movement is required to bear a given relationship with the current fed to the device, for instance a linear relationship.

It is known to provide in a device of the kind referred to a solenoid into which an iron armature in the form of a plunger is attracted against a constraining force, the desired relationship between current and movement being obtained by suitable shaping of the end of the plunger and/or of a fixed pole-piece in the solenoid. All such known arrangements have the common characteristic that the working air-gap varies in length with the movement of the plunger. In these prior arrangements the plunger is large and heavy. The consequent inertia of the system precludes its use when rapid response to change in current is required, or when the arrangement is subject to external accelerations as, for example, when used in aircraft.

The object of the invention is to provide an electromagnetic device of the kind referred to, in which a small and light armature is used and in which the relationship between the current fed to the device and the force exerted against the load force may be selected from between wide limits.

According to the present invention, an electromagnetic device in which movement of the armature against a load force, more particularly a spring, bears some desired relationship to the exciting current comprises fixed and movable cooperating magnetic members whose relative movement is such that the perpendicular distance across the air-gaps between juxtaposed faces of the said members remains constant, and such that the overlapping areas of the said juxtaposed faces change with said movement and in which one or more of either or both said faces is or are so shaped that the said overlapping areas change in a non-linear manner with respect to said movement.

The invention will be better understood after reading the following description of several exemplary embodiments with reference to the accompanying drawings in which:

Figure 1 is an elevational view of an electromagnetic device of E-shaped construction;

Fig. 2 is an end view of the armature of Figure 1, as seen in the direction of the arrow A;

Fig. 3 is an exploded perspective view, partly broken away, of a pot-shaped electromagnetic device;

Fig. 4 is an elevational view of an electromagnetic device comprising a rotary armature; and

Fig. 5 is an end view of the armature of Fig. 4, as seen in the direction of the arrow B.

Referring to the construction shown in Figures 1 and 2, 7

a is an E-shaped stator energized by the solenoid b and cooperating with a C-shaped armature c, the two limbs c of which are tapered in the direction of its movement relatively to the stator, as seen in Fig. 2, but its width between the inner and outer limbs of the stator is constant.

Referring to the construction shown in Fig. 3, 2a is a pot-shaped stator energised by the solenoid 2b and cooperating with an annular armature 2c, portions of which towards the stator are tapered by two downwardly inclined cuts being made diametrically opposite each other, as shown in the figure.

Referring to the construction shown in Figs. 4 and 5, the stator 3a, energised by the solenoid 3b, is provided with two opposite concave shaped pole-pieces cooperating with a rotary armature 3c of Z-shape, the ends c of which are tapered in its direction of rotary movement, as shown in Fig. 5.

The details for carrying the invention into eflect, in connection with a D. C. or an A. C. electromagnet, may be modified without departing from the essence of the invention aforementioned. For instance, instead of the stator, the armature may be energised and instead of the ends of the armature being tapered in the direction of movement, the face of the stator cooperating with the ends of the armature may be suitably tapered.

What I claim is:

1. An electromagnetic device comprising a stator member having a core and at least one pole face of magnetic material, an armature member of magnetic material mounted for parallel movement in spaced relationship with respect to said pole face, said movement being such that the perpendicular distance across the air-gap between juxtaposed faces of said pole face and said armature member remains constant throughout its movement while the overlapping area of said juxtaposed faces changes with said movement, and a winding for energizing one of said members operatively supported thereon, characterized by one of said juxtaposed faces having a triangular shape in the plane parallel to the other face and disposed such that upon movement the overlapping area of said juxtaposed faces increases at a greater than linear rate as the armature moves into overlapping relation with respect to said pole face.

2. An electromagnetic device according to claim 1, in which said core consists of an E-shaped member with parallel legs, said armature consists of a C-shaped member with its arms disposed between the legs of said core,

.and the arms of said armature have a triangular shape in the plane parallel to the opposing faces of the legs of the core and have a constant width in the plane of said core.

3. An electromagnetic device according to claim 1, in which said core comprises two concentric, opposite, and concave pole faces and said armature comprises a Z- shaped rotatable member having its ends tapered along the arcs of their movement so as to have said triangular shape and having its faces concentric with those of the said pole faces.

References Cited in the file of this patent UNITED STATES PATENTS 293,076 Piette Feb. 5, 1884 2,127,265 Martin Aug. 16, 1938 2,337,375 Cramer Dec. 21, 1943 2,738,450 Matthews Mar. 13, 1956 FOREIGN PATENTS 215,679 Great Britain May 15, 1924 551,790 Great Britain Mar. 10, 1943

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