US3147410A - Electromagnet with spring-retained armature structure - Google Patents

Description

L. C. ANDERSON, JR., ETAL Sept. 1, 1964 ELECTROMAGNET WITH SPRING-RETAINED ARMATURE STRUCTURE INVENTORS LQUIS C. ANDERSON JR.

FIG. 3

ARTHUR A". HAGSTROM ATJ'ORNEY United States Patent 3,147,410 ELECTROMAGNET WITH SPRING-RETAINED ARMAT STRUCTURE Louis C. Anderson, In, Arlington Heights, and Arthur A. Hagstrom, Hoffman Estates, Roselle, 111., assignors to Teletype Corporation, Skokie, 111., a corporation of Delaware Filed Oct. 17, 1962, Ser. No. 231,227 Claims. (Cl. 317-165) This invention relates to an electromagnet assembly and more particularly to the mechanical construction of an electromagnet assembly.

Heretofore, magnet assemblies have consisted of a relatively large number of expensive elements, adjustable with respect to one another in order to accurately establish a small air gap between the armature and the pole face of the magnet and to maintain this small air gap after a large number of cycles of operation with attendant wear and consequent looseness of elements.

Accordingly, an object of the invention is to provide a magnet assembly that has no adjustable components and which has relatively few and inexpensive elements that are readily assembled and disassembled.

Another object of the invention is to provide a magnet assembly wherein the moving armature element is biased into contact with its bearing surface to take up any looseness therebetween that might occur due to wear.

A further object of the invention is to provide an electromagnet assembly having a wide bearing surface for its armature over which to distribute the wear load thereby reducing the amount of wear normally encountered in electromagnet assemblies.

A further object of the invention is to provide a small powerful electromagnet assembly having a small easily established, nonadjustable air gap between its armature and pole face and wherein a small movement of its armature is translatable into a large movement of extensions operable by the armature.

A feature of the invention is to provide a more compact magnet assembly by disposing the armature extensions in openings provided between the electromagnets coil and laminations.

A feature of the invention is the retaining of the shaft, about which armature pivots, in receiving slots for the shaft under the urging of a spring acting through the armature of the electromagnet assembly.

According to the preferred embodiment of the invention the magnet assembly is comprised of an upper frame member to which are secured the laminations and coil of the electromagnet. The frame member has machined therein receiving slots for an armature pivot shaft, the slots being machined simultaneously in the same operation as the machining of the ends of the laminations to form a pole face for the magnet. Thus, the width and depth of the slots are accurately maintained with respect to the pole face on the magnet laminations since both the slots and the pole face are machined simultaneously in the same machining operation. To secure the armature pivot shaft within the ground slots, a flat plate armature has wide bearing surfaces spring urged into engagement with the armature pivot shaft to retain the armature pivot shaft within the machined slots. Armature extensions are secured to the armature and extend the length of the electromagnet in the openings between the coil and laminations. The armature extensions provide a large amount of movement at their free ends for a relatively small amount of movement of the armature. 1

Other features and advantages of the invention will become apparent from the following detailed description when considered in conjunction with the accompanying drawings wherein:

3,147,410 Patented Sept. 1, 1964 ice FIG. 1 is a side elevational view of the magnet assembly according to the preferred embodiment of the invention;

FIG. 2 is a plan view of the magnet assembly, and

FIG. 3 is an end view of the magnet assembly having a portion of an armature broken away to show the curved end portions of the armature extensions that are secured to the armature.

Referring now to FIG. 1, there is illustrated a magnet assembly 10 for generating large forces capable of operating instrumentalities such as a tape reader of the type shown in the copending application of L. C. Anderson,

In, A. A. Hagstrom and R. A. Thienemann, Serial No. 231,199 filed of even date herewith.

The electromagnet assembly 10 has a plurality of sheet metal laminations 11 of an E-shaped configuration secured together by a plurality of rivets 12 to constitute a unitary core assembly 13. The central leg of the core assembly 13 supports a hollow plastic bobbin 14 upon which are wound the turns of wire that constitute an energizable coil 15 for the electromagnet assembly 10. The coil 15 is adapted to be energized in the conventional manner and causes magnetic flux to be distributed through the legs of the E-shaped laminations 11 to attract a metallic armature 20 against the end portions of the legs of the E-shaped laminations 11 that constitute the pole face 22 of the electromagnet assembly 10.

The pole face 22 of the laminations is machined by grinding or milling to assure a flat pole face 22 that is square with the laminations 11 and, simultaneously with the machining of the pole face 22, slots 25 are machined in a magnet support frame 26 and the frame 26 is machined square with the pole face 22. The same machine tool is used to machine the pole face 22 and slots 25. As seen in FIG. 2 the magnet support frame 26 is of the same general E-shaped configuration as the laminations 11 which are secured thereto by the rivets 12. As seen in FIG. 1, the magnet support frame 26 has an upwardly directed, strengthening flange 27 running longitudinally of the laminations 11 and ending in vertically rising portion 28; and as seen in FIGS. 2 and 3, the magnet support frame 26 has an identical vertical portion 28 on the side opposite that shown in FIG. 1.

Since the receiving slots 26 are machined simultaneously with machining of the pole face 22, the receiving slots 26 are accurately located both as to the height of the slot above the laminations and also as the depth of the slot relative to the pole face 22. Disposed within the receiving slots 25 is an armature pivot shaft 30 which serves as the pivot about which the armature 211 rotates when it is moving either toward or from the pole face 22. The armature 20 is a piece of flat plate material with a pair of spaced upstanding fingers 31 (FIG. 3) which are in engagement with the cylindrical surface of the armature pivot shaft 30. As seen in FIG. 1 the fingers 31 extend upwardly from the armature 20 to engage the armature pivot shaft 30 at a line of contact 32, and elongated slots 33 in vertical cars 34 on a pair of armature extensions 35 contact the armature pivot shaft 30 at an upper point of contact 36 and a lower point of contact 37. The armature extensions 35 terminate in inwardly directed extremities 38 (FIG. 3) which are fixedly secured by welding or other suitable means to the armature 20 thereby constituting a unitary armature and armature extension.

It should be noted the armature pivot shaft 33 is not fully seated within the slots 33 since the armature pivot shaft 34) engages the armature 20 at the line 32, which line is to the left of the end of the slots 33 as shown in FIGJI. Thus, the tolerances or adjustments between the depth of the slots 33 and the armature 20 at the line 32 have been eliminated. Also, it should be noted that the rightmost portion of the armature pivot shaft extends to the right beyond the plane of the pole face 22 as seen in FIG. 1.

To afford a compact electromagnet assembly, the armature extensions 35 are made of n onmagnetic material so as not to pick up flux and carry it to the armature 20 and the extensions are extended rearwardly in the space on either side of the coil between the coil-15 and the outer legs of the E-shaped laminations 11. The armature extensions 35 extend upwardly and outwardly to terminate in horizontal portions 40 each of which have an aperture 41 therein for connection to an instrumentality to be actuated by the electromagnet assembly 10.

To secure the armature pivot shaft 30 within its receiving slots 25 and to bias the armature to its normally open position shown in FIG. 1 there are provided a pair of contractile armature return springs 42 secured between the upstanding ears 34 on the armature extensions 55 and a spring-anchoring shaft 43 carried in a pair of open ended slots 44 formed in the vertically rising portions 28 of the magnet support frame 26.

The armature return springs 42 are always under tension and thus serve to exert a continual force tending to pull the shaft 43 rightwardly as viewed in FIG. 1 and to pull the upper end of the ears 34 of thearmature extensions 35 in a counterclockwise direction as viewed in FIG. 1 about the armature pivot shaft 30. Since the armature 20 is attached to the inwardly turned extremities 38 (FIG. 3) of the armature extensions 35, the armature 20 is continually urged into contact with the armature pivot shaft 30 at the line of contact 32 by the armature return springs 42. Inturn, the armature pivot shaft 30 is urged to fully seat itself within the receiving slots formed in the legs 28 of the magnet support frame 26.

As shown in FIGQI, the amount of gap between the armature 20 and pole face 22 is limited by the instrumentalities (not shown) attached tothe armature extensions 35. Obviously, a stop could be provided in the path of the armature 20 to limit its return rotation about the shaft 30. The gap between the armature 26 and pole face 22 near the midpoint of the pole face 22 is approximately .020 of an inch and about .025 at the lower ends of the pole face 22 and armature 20.

To prevent lateral movement of. the armature pivot shaft iiti relative to the magnet support frame 26, a pair of snap rings 45 are secured to the armature pivot shaft, one on each side of one of the vertically rising portions 28 of the magnet support frame 26. Similarly, toprevent lateral movement of the armature extensions 35 and armature 20 relative to the laminations 11 and the coil 15, a pair of snap rings 47 are secured to the pivot shaft 30 and positioned on each side of one of the armature extensions 35.

It should be appreciated that the entire assembly of laminations 11 and coil 15, on the frame 26 with shaft 30, shaft 43 and armature 20 and armature extensions are held together by the springs 42. Thus, the magnet assembly is readily capable of assembly and disassembly without the use of the usual fasteners.

In operation, the coil 15 of electromagnet assembly It is energized and creates a magnetic field to attract the armature 20 towards the pole face 22 on the laminations 11. During movement of the armature 20, armature extensions 35 move therewith in an arcuate manner about the armature pivot shaft 30. The amount of movement of the armature 20 to its pole face 22 is .025 at the greatest point and at the midpoint of the pole face 22 is about .020 which is a small distance, and hence the magnetic force applied to the armature 20 is quite large. It should be noted that the armature 20 engages the pole face 22 only at its lower extremity since the upper extremity of the armature is maintained at a distance from the pole face by that portion of the pivot shaft 30 which extends outwardly beyond the pole face 22. The armature extensions 35 multiply the .020 of an inch of movement of the armature 20 into a large movement of approximately .l00 of an inch at the outer extremity of the armature extensions 35. Upon de-energization of the coil 15, the armature return springs 42 will act through the upstanding ears 34 of the armature extensions 35 to rotate the armature 20 in a counterclockwise direction, as viewed in FIG. 1, about the armature pivot shaft 30 to return the armature 20 to the position shown in FIG. 1. In practice, it has been found that armature pivot shaft 30 rotates in the receiving slots 25 over a large number of operations thereby distributing the Wear over the entire peripheral surface of the pivot shaft 30. Any small amount of wear of the shaft 30 reduces the extent to which the shaft 30 extends over the pole face 22. With a decreasing air gap, the magnet becomes more powerful than it was with a large air gap.

From the foregoing, it should be apparent that the mag- 7 net assembly is an exceedingly simple structure that is readily assembled and disassembled merely upon the disengaging of the armature return springs. Also, it should be apparent that adjustments can be eliminatedand close tolerances held by the grinding of the poleface and receiving slots simultaneously and by having the armature urge its pivot shaft within the receiving-slots. Also, if any wear occurs there will be no accompanying looseness of parts since these armature return springs urge the armature and its pivot shaft into contact with each other and urge the shaft into the slot 25. Finally, it should be apparent that a more compact assembly is achieved by disposing the armature extensions within the space existing between the coil and laminations on each side of the coil.

Although only one embodiment of the invention is shown in the drawings and described in the foregoing specification, it will be understood that invention is not limited to the specific embodiment described, but is capable of modification and rearrangement and substitution of parts and elements without departing from the spirit of the invention.

What is claimed is:

1. An electromagnet assembly comprising a frame, an energizable coil carried by said frame, a plurality of metallic laminations fixed to said frame and constituting a magnetizable core for the electromagnet, said laminations having their ends disposed to constitute a pole face for the.

electromagnet, locating surfaces in said frame, an armature shaft urged into engagement with said locating surfaces and free for rotation with respect thereto, an armature having at least one flat surface engaging the periphery of said shaft in a line of contact and movable into engagement with said pole face upon energization of the coil of the magnet, and biasing means urging said flat surface of said armature against said armature shaft and thereby urging said armature shaft into engagement with said locating surfaces in said frame whereby said shaft and said fiat surface of the armature maintain a line of contact between them during operation of the armature.

2. In an electromagnet assembly having a frame means,

a coil, and laminations attached to the frame means, the improvement comprising: i

(a) a pair of open ended bearing surfaces in said frame means,

(b) an armature shaft in engagement with said bearing surfaces,

(c) an armature urged into engagement with a portion of said armature shaft,

(d) armature extension means secured to said armature and having slots therein for partially encircling said armature shaft thereby constituting with that portion of the armature in engagement with the armature shaft, a pivot for the armature, and p (e) a spring interconnecting said frame means and said armature extension means thereby urging said arma ture against said armature shaft to retain said armature shaft against said bearing surfaces.

3. The magnet assembly of claim 2 wherein a pair of open ended slots are provided in said frame means, a spring anchoring shaft is seated within the slots and wherein the spring means interconnecting the armature extension means and the frame means retains said anchoring shaft in said slots.

4. In an electromagnet assembly having a frame to which are secured a coil and a core forming laminations and having an armature movable upon energization of the electromagnet, the improvement comprising:

(a) a pair of open ended slots constituting location surfaces in said frame,

(b) a pole face on said laminations spaced a predetermined distance from said location surfaces,

(0) a shaft disposed in the slots in the frame and thereby having a portion of its peripheral surface accurately located with respect to said pole face,

(d) an armature means having a portion thereof in engagement with said shaft thereby accurately locating said armature with respect to said pole face,

(e) armature extension means secured to said armature and movable with said armature to amplify the movement of said armature means,

(1) said armature extension means having open ended slots formed therein for engaging said shaft at two spaced points and thereby constituting with said armature means a pivot for said armature means and said armature extension means,

(g) holding means on said frame, and

( h) armature return spring means interconnecting said holding means and said armature extension means thereby urging said armature means against said shaft and holding said shaft in the slots and said armature means in engagement with said shaft.

5. In the electromagnet assembly of claim 4, said laminations surrounding said coil on at least two sides and spaced from said coil on these two sides, said armature extensions being of nonmagnetizable material being disposed in this space.

References Cited in the file of this patent UNITED STATES PATENTS Stevens Mar. 9, 1926 2,259,127 Eaton Oct. 14, 1941

Claims (1)

1. AN ELECTROMAGNET ASSEMBLY COMPRISING A FRAME, AN ENERGIZABLE COIL CARRIED BY SAID FRAME, A PLURALITY OF METALLIC LAMINATIONS FIXED TO SAID FRAME AND CONSTITUTING A MAGNETIZABLE CORE FOR THE ELECTROMAGNET, SAID LAMINATIONS HAVING THEIR ENDS DISPOSED TO CONSTITUTE A POLE FACE FOR THE ELECTROMAGNET, LOCATING SURFACES IN SAID FRAME, AN ARMATURE SHAFT URGED INTO ENGAGEMENT WITH SAID LOCATING SURFACES AND FREE FOR ROTATION WITH RESPECT THERETO, AN ARMATURE HAVING AT LEAST ONE FLAT SURFACE ENGAGING THE PERIPHERY OF SAID SHAFT IN A LINE OF CONTACT AND MOVABLE INTO ENGAGEMENT WITH SAID POLE FACE UPON ENERGIZATION OF THE COIL OF THE MAGNET, AND BLASING MEANS URGING SAID FLAT SURFACE OF SAID ARMATURE AGAINST SAID ARMATURE SHAFT AND THEREBY URGING SAID ARMATURE SHAFT INTO ENGAGEMENT WITH SAID LOCATING SURFACES IN SAID FRAME WHEREBY SAID SHAFT AND SAID FLAT SURFACE OF THE ARMATURE MAINTAIN A LINE OF CONTACT BETWEEN THEM DURING OPERATION OF THE ARMATURE.

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