US2942164A - Electromagnet construction - Google Patents

Description

June 21, 1960 L. H. FRosT ELECTROMAGNET coNsTRuc'rIoN Filed May 11, 1955 HG. I

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United States Patent O ELECTROMAGNET CONSTRUCTION Louis H. Frost, 1231 Breton Road, SE., Grand Rapids, Mich.

Filed May 11, 1955, Ser. No. 507,572

4 Claims. (Cl. 317-184) This invention relates to the structure of magnets for use with a'lternating current. It is concerned more par- -ticularly with a structure which embodies va solenoid or coil, a core or frame, 'and an :armature arranged to be moved lincident to the energizng of the coil with alternating current. Sucha structure may be employed as the motivating force or mover for controlling various and divers instrumentalities and elements, such as valves, arranged to be opened and closed, relays or other controlling or controlled devices.

In order to obtain a quiet operation and to eliminate chatter, it has been common heretofore to employ what is known as a shading coil in the pole faces of the frame. Such a shading coil acts as a short circuit turn for the flux and produces a flux through the portion of the pole face which the shading coil surrounds which is out of phase with the main flux. This out of phase fiux provides force ,active upon the armature when the main fiux, incident to the alternating current, is passing through zero. This minimizes buzzing and chattering of 'the armature. The shading .coil tends 'to resist themain flux, or as it might be said, limits the main flux through the shaded varea of the pole face.

The objects of this invention is to provide a structure to more nearly balance the reluctance of the unshaded magnetic circuit to that of the shaded magnetic circuit. In -accordance with the invention, |this is accomplished by providing a mechanical gapV for varying the reluctance of the magnetic circuit which Will function and adjust itself to provide an optimum Operating condition or balance of flux through the shaded and unshaded areas of-the-polefface. -In carrying out the invention the un- 2,942,164 Patented June 21, 1960 Fg. 2 is a top plan view.

'Fig. 3 is an enlarged elevational view showing the pole face 'and armature.

Fig. 4 is an enlarged view showing in plan a pole face and illustrating the shading coil.

Fig. 5 is -a sectional view taken substantially on line 5-5 of Fig. 1 illustrating structure of the device.

Fig. 6 is a sectional view 'taken on line 6-6 of Fig. l showing a yielding element for the armature.

Fig. 7 is a view of diagrammatic nature showing the armature seated upon the pole faces.

The frame of the structure is of U-shape having one arm 1, another arm 2, and a connecting bight portion 3. The frame is preferably made up of a multiplicity of laminations of magnetic material, such as iron or steel, as illustrated in Fig. 2, held together by suitable rivets 5. Below the bight portion 3, as Fg. 1 is viewed, is 'a mounting bracket 6 held by rivets 7 which also pass through the laminations of the frame.

The ends or poles of -the varms 1 and y2 a-re of the overhanging type, as shown in Fig. 3, wherein -i't will be noted that the top of the arm 1 extends laterally to the left, as at 10, as Fig., 3 is viewed, presenting an undersurface l11 indicated in dotted lines. The arm 2 is similarly constructed, the same' extending nwardly to provide an overhanging portion 12.

On each side of the frame is a bracket, one at 14 and one at '15, secured by rivets 16 which also pass through the laminations of the core.

Positioned within the frame is the coil or vsolenoid 20. This coil is positioned to abut against the lbrackets 14 and 15. In order to hold the coil against the brackets 14 and 15, there are two spring elements 21 and 22 spaced relative to each other and disposed between the bight portion 3 and one end of the coil to 'thus constantly urge thecoil against the brackets 14 and 15. The purpose of this will presently appear.

shaded areas of -the pole face are provided with a contour so that some portions thereof are -in a plane different from the plane of the `shaded area and thus are spaced from the cooperating part of the armature when the armature seats upon, or substantially seats upon, the shaded area. This is preferably accomplished by providing some of the surfaces of the unshaded area at an angle 'relative to the surfaces of the shaded area.

The ultimate structure of 'the electromagnet is simple but 'the manner in which the simple structure controls the flux circuit is important -in that the Optimum Operating condition and balance is attained, and it has been found that an elec-tromagnet device constructed in accordance with the invention produces a heavier pull when the arm-ature is seated than the same device, with all other things being equal, will produce without the invention. Thus, the electrom-agnetc device of this invention is more efficient and size for size, other things being equal, performs better than those heretofore.

An electromagnetic device constructed in accordance with the invention is shown in the accornpanying drawmgs:

Fig. 1 is a side elevational view showing the coil, the frame, the armature, and illustrating the armature in one position in dotted lines.

V27 is a spring 30 which underlies the armature.

provided with suitable The frame is provided with centrally located guides of non-magnetic material, such as brass; one such guide is illustrated at 25 and the other at 26 and these guides are of plate form and are secured to the bight portion 3, as -by means of a bolt 27 (Fig. 6). Also secured by the bolt The spring 30 extends transversely across the bight portion 3 and lies |between the springs l21 and 22. The coil 20 is contacts 31 for electrical connection.

The armature is of T-shape having a main or stem portion 35 arranged to slide in the guides 25 and 26 and lateral portions 36 and 37 forming the cross bar. The armature is preferably made of a plurality of laminations such as magnetic steel or iron held together by rivets 38 and 39. The outside pieces of the armature may be heavier than the other laminations, and they project in- Wardly and upwardly therefrom as indicated at 40 and 41 and are provided With aligned apertures 42 for attachment to an inst-rumentality to be operated. When the armature is attracted, the stem engages the spring 30 which is flexed so that the cross bar can be drawn substantially flush against the pole faces. This stores energy in the spring 30 which provides a force for overcoming the residual magnetism when the current is inter'rupted to thus move the armature from the pole faces. The spring also cushions the impact When the armature is attracted. Also, it will be noted that when the magnetic force pulls the armature down, as Fig. l is viewed, the reaction forces on the coil is against the brackets 14 and 15. Since the solenoid or coil is at all times held against the bracket 14 or 15 there is no possibility of relative movement of the coil relative to the frame and furthermore the springs 21 and 22 are not called upon to take the reaction of the forces acting upon the armature.

. sweet There is a shading coil for each pole of the frame, one being illustrated at 45 and the other at 46 and since they are identical, only one is shown `in detail in Figs. 3 and 4. The shading coil is a closed Aturn of copper or in'other words, a copper ring as shown in Pig. 4. The coil shown is of rectangular Shape having two runs 46a and 47 and connecting side portions 48 and '49. The pole face is formed with grooves 50 for receiving the portions 46a and 47 and to hold the shading coil in position, some of the metal -of the core is peened over as at 51.

To obtain the Optimum balanced condition the unshaded portions, as aforesaid, are contoured to provide a mechanical gap relative-to the armature. portion, of course, is the portion which lies within the shading coil while the unshaded portions are those lying without the shading coil. The Contour given Vto the unshaded'portions, as shown herein, resides in angular faces 55 and 56. Both pole faces are the same and have the same reference characters applied. Thus, a mechanical gap 57 is provided by the contour 55 and mechanical gap 58 provided by the Contour 56. The angle of the faces 55 and 56, as shown herein, is about 45 relative to the plane of the pole faces. This angle, however, may be varied to obtain a balanced condition for particular physical dimensions and magnetic conditions involved. Moreover, the gap may be provided by differently shaped contours.

The shaded When energized the flux attracts the armature and it 1 moves from the dotted line position shown in Fig. 1 until the cross bar of the T substantially seats upon the pole fac'es. The fiux path is across the pole faces traveling through the armaturc. The shaded area, that is, the area within the shading coil, may be larger than the cross sectional area of the respective arms 1 and 2 of the frame. Therefore, the area actually has flux carrying capacity in excess of the frame arms, but the shading coil resists the lfiow of flux therethrough and delays it, so to speak, so that when the alternating current is passing through zero the =delayed flux holds the armature seated tight thus minimizing or eliminating buzzing or chattering. The provision Vof the mechanical gap in the unshaded portions, in effect,

adds resistance to the fiow of flux in the unshaded areas. Thus, it might be said it contributes to the shading function serving to balance the reluctance of .the unshaded magnetic circuit to that of the shaded magnetic circuit. As stated above, an electromagnetic device thus constructed produces a pull on the armature when the armature is .seated greater than a magnetic device wconstructed without the invention, otherithings as to mechanical structure and magnetic conditions being equal.

I claim:

1.*1An electrornagnetic device for use with alternating electrical current comprising, a coil ar'ranged to be supplied with alternating electrical current, a frame member formed of magnetic material disposed in proximity to said coil and having a pole face, a movable armature member disposed in magnetic proximity to said coil and frame, said arrnjaturev member being arranged togjbe' moved by magnetic force having its source in said coil and frame, said armature member having a face, a shadi'ng coil in said face of one of said members defining a shaded area within the lshading -coil and `an funshadedgarea outside of the shading coil, the other of said facesv and said shaded area having complementary conforrnation so that said Shader] area is engagable throughout the major portion of its area with said other face, said unshaded area and said other face having surface portions With complementary conformations so that said surface portion of said 'unshaded area is engaga'ble throughout the major part of its area With said other face portion, the surface of one of said faces being sloped so that a tapering gap iso provided between another portion of said unshaded area and the area of the face apposed thereto when vsaid armature memberv face substantially seats on said frame member face. i

2. The device defined in claim l wherein said shaded area is engagable throughout substantially ,its entire extent with said other face. v

3,. The device defined `in claim 1 wherein the interen'- gagable portions of said shaded area and other face .are substantially planar and said -interengagable portions of said unshaded area and other face' are substantially planar.

4. The device defined in claim 3 where'in said 'substantially planar portions of said shaded area and 'unshaded area lie substantially in the same plane.

References Cited in the lfile of this patent UNITED sTATEs PATENTS, i

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