Electromagnetic operator
United States Patent 2358828

My present invention relates to electromagnetic operators, and in particular to those of the so-called "weak-current" type which are adapted to be operatively energized by a minute amount of power, such as that available from a thermoelectric generating device heated by an ordinary small pilot-burner...

Ray, William A.
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Ray, William A.
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251/129.16, 335/282
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My present invention relates to electromagnetic operators, and in particular to those of the so-called "weak-current" type which are adapted to be operatively energized by a minute amount of power, such as that available from a thermoelectric generating device heated by an ordinary small pilot-burner flame. The magnitude of such power is of the order of ten milliwatts, and has generally been considered as insufficient to operate a control device, such as an ordinary gas valve, without the aid of supplemental means and energy-as, a motor operated by the energy derived from the pressure of the fluid controlled by the valve.

It is therefore a main object of this invention to provide a "weak-current" electromagnetic device which is capable of operating "directly" (i. e., without the requirement for supplemental means or energy), for example, a gas valve of suffcient capacity to control the heating of a small residence.

Another object of this invention is the provision of an electromagnetically operated valve, having a capacity sufficient to supply the demand of a domestic gas heating device, which can be operatively energized by a pilot-burnerheated thermoelectric generating device, so that it is independent of the electric service lines and is relatively noiseless in operation.

Another object is the provision of an electromagnet having a pole face, the area of which is considerably greater than that of the cross-sectional area of the body of its core, so thatwhen the flux density in the core, produced by a weak magnetizing force, is at a point considerably below the knee of the magnetization curve for the core material-the flux density in the large-area pole face is substantially the. same as that which could be produced by the weak magnetizing force if the cross-sectional area of the body of the core were not reduced. An allied object is the provision of an electromagnet, for energization by weak current and of the general character described, wherein the cross-sectional area of the body of the core is small, so that the mean turn-diameter of a coil wound around it is small and the electrical resistance of the coil correspondingly small.

Another object is the provision of an electromagnetic operator, comprising a U-shaped core 1 having enlarged pole faces, wherein the parts are so arranged that leakage flux is minimized. Other objects and advantages of the Invention will be found in the description, the drawing, and in the claims; and for complete understanding i of the invention reference may be had to the following detailed description and accompanying drawing, wherein: Figure 1 is a view, in longitudinal section, of an electromagnetically operated fluid control valve embodying my invention; Figures 2 and 3 are transverse sections taken along the lines 2-2 and 3-3, respectively, of Fig. 1; Figure 4 is an enlarged fragmentary section taken along the line 4-4 of Fig. 3; and Figure 5 is a schematic view, in perspective, of the magnetic circuit of the device shown in the other figures; and a diagram of a suitable coil-energizing circuit.

In the drawing, the numeral II indicates a valve casing having an inlet 12 and an outlet 13 separated by a partition 14. Threaded in an opening through the horizontal portion of this partition is a valve port member II, in the top surface of which there is an annular recess 16. The side walls of the recess terminate at the surface in a plane to form an inner and an outer valve seat 17 and II, respectively (Fig. 4), the adjacent surface of the port member being relieved so that the seats are generally knifeedged. The recess I is fluidly connected with the valve outlet 13 by a plurality of openings 19.

Cooperable with the valve seats is a disk-like closure 20, preferably of non-magnetic material, which is centrally apertured and has a plurality of transverse openings 21 (Fig. 4) whereby the inlet fluid can communicate with the area adjacent the inner valve seat 17. When the maximum lift of the closure is very small (as in the arrangement shown), increase of flow capacity of the valve is effected by the double valve seat arrangement, since the fluid can pass to the recess in substantially equal amounts across both of the seats. This feature is the subject of Patent No. 2,261,562, granted to me November 4. 1941.

Secured by screws to the top surface of the closure 20 is a disk-shaped armature 22; a diaphragm 23, of flexible material such as artificial rubber, being interposed therebetween. This diaphragm serves as a guide for the armatureclosure member, and is secured at its margin between the apertured top wall of the valve casing 10 and a structure 24 mounted thereon.

Supported by the structure 24 is an electromagnet comprising a U-shaped core 25, formed of round material, to the end of each of the side arms of which is attached a generally semi15 circular pole plate 26 (Fig. 2). The extremities of the core are tapered to fit in correspondingly tapered holes in the pole plates, the material of the plates around these holes being punchedup to provide relatively large contact area, and the ends of the tapered portions of the core are riveted-over to maintain intimate engagement between them and the plates. Extending from the outer edge of each of the pole plates is a plurality of bent-up ears 21 whereby the core and pole-plate assembly is secured (as by rivets or screws 28) to the inner flange of a circular frame 29 which forms the upper section of the structure 24, the lower section comprising an annulus 30, and both of the sections being of non-magnetic metal. Between the sections, in a plane immediately below the underside or pole faces of the plates 26, is a thin disk or diaphragm 31, of non-magnetic material, which serves both to shield the electromagnet from the fluid controlled by the valve and also as means for preventing direct contact of the armature 22 with the pole faces. The frame 29 has a strengthening cross rib 32 (of non-magnetic metal) which extends closely between the adjacent edges of'the pole plates 26 and thus fills the "air gap" therebetween, the bottom surface of the rib being in the plane of the pole faces.

Around the side arms of the core is a pair of interconnected coil windings 33; and covering the electromagnet is a housing 34, preferably of non-magnetic metal.

Communication between the inlet of the valve and the space above the armature 22 is provided by the transverse passages 2 through the closure 20, and by a central opening 35 through the armature. The fluid pressure above and below the armature is thus equalized; and any dirt carried by the controlled fluid is prevented, by a filter 36 covering the lower end of the opening 35, from reaching the shallow space between the armature and the pole-face diaphragm 31.

When the electromagnet is energized by passage of current through the coil windings 33, the armature-closure member 22, 20 is attracted toward the faces of the pole plates 26, thus opening the valve; a plurality of small bosses 3T (Fig. 4), projecting integrally from the armature, serving to maintain the major portion of the top surface of the armature spaced by a short distance from the diaphragm 31. For ensuring release of the armature from the electromagnet when the same is deenergized, a plurality of spring-pressed pins 38 (Fig. 4) is provided, these pins extending through openings in the armature and having shoulder portions which engage the underside of the armature so that the tops of the pins are maintained out of engagement with the diaphragm 31 when the armature is in unattracted position; initial attractive movement of the armature thus being unimpeded.

In Fig. 5, the relation between the size of the core body 25' and of the pole plates 26' Is clearly brought out; as illustrated, the ratio of area of each of the pole faces to the cross-sectional' area of its respective core arm being approximately 25:1. The electromagnet is shown in this figure connected, in series with a switch or thermostat 39, for energization by an ordinary thermoelectric generating device 4V!, which is assumed to be of such size that it can be properly heated by the flame of an ordinary pilot burner and is capable of producing power of the order of ten milliwatts. Material of high permeability, such as "high-nickel iron" alloy, is preferably employed for the construction of the electromagnet and the armature 22'. When, as was pointed out in the objects, the flux density in the core is at a point considerably below the knee of the magnetization curve for this material, the flux density in the large-area pole faces is substantially the same as could be produced by this weak magnetizing force if the cross-sectional area of the core were the same as that of the pole face.

However, by reducing the diameter of the core arms and by making them relatively long, the mean turn diameter of the coil winding may be small and its electrical resistance correspondingly small. The minute amount of energy generated by the thermoelectric device is thus effective to produce a flux density in the core which, as it appears at the enlarged pole faces, produces an attractive force on the armature which is considerably greater than could be produced in an electromagnet of conventional form.

While I have herein shown and described a specific embodiment of my invention, I wish it to be understood that modifications may be made without departing from the spirit of the invention, and that I intend therefore to be limited only by the scope of the appended claims.

I claim as my invention: 1. In an electromagnet: a U-shaped core having at the end of each of its side arms a plate defining a pole face the area of which is at least several times greater than the cross-sectional area of its respective side arm, a coil winding around at least one of the arms of the core, said pole faces being in a plane and spaced apart to provide an air gap therebetween, and a support for said electromagnet comprising an apertured member surrounding said pole plates and having a plane outer surface so located as to coincide substantially with said plane of the pole faces and an inner surface parallel thereto, a marginal portion of each of said pole plates adjacent said member being formed to provide a surface in engagement with said inner surface of the member.

2. An electromagnet -structure, as defined in claim 1, wherein said supporting member is provided with a non-magnetic cross-rib extending through said air gap between the pole plates and in engagement with the adjacent edges of said plates.

3. In an electromagnetic operator: an electromagnet comprising a core having an end portion defining a plane pole face, means for supporting said electromagnet comprising a first apertured member surrounding said end portion of the core and having a plane outer surface located in the plane of said pole face, a flat second member having an aperture corresponding substantially to that of said first member, means for securing said members together, a thin flat nonmagnetic diaphragm interposed between said members and covering said pole face, a disk-like armature substantially'coextenslve with said pole face and positioned closely adjacent thereto, and means for supporting and guiding said armature comprising a flexible diaphragm secured thereto and to the outer plane surface of said second member, said diaphragms and said armature defining with the interior of said second member a shallow chamber.