US3185899A - Magnet structure - Google Patents

Description

May 25, 1965 F. c. SKELTON, JR 3,185,899

MAGNET STRUCTURE Filed May 21, 1962 Il l l' Pg-2 I I/ pm. l,

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grani C. Skelton (jr. 11 (dwf/.7 l Z/...Q UTTGRNEYM/ United States Patent O 3,135,399 MAGNET STRUCTURE Frank C. Skelton, Ir., Beloit, Wis., assigner to Warner Electric Brake & Clutch Company, South Beloit, Ill., a corporation of Delaware Filed May 21, 1962, Ser. No. 196,372 3 Claims. (Cl. 317-158) This invention relates to a magnet adapted for use in a magnetic friction clutch or brake to force magnetic flux into and out of an abutting face of a narrow magnetic armature and thereby draw the latter into gripping engagement with the magnet pole faces. In View of the narrow width of the armature, it has been the practice heretofore to bevel the adjacent edges of the magnet pole pieces and fill the resulting V-shaped groove with non-magnetic material which separates the pole faces by a very narrow gap while securing the pole pieces rigidly together.

The primary object is to provide a separating filling of the above character which facilitates low cost manufacture of the magnet and insures precise and uniform edgewise spacing of the pole faces by a non-magnetic gap of the desired narrow width.

A more detailed object is to separate the pole faces by a thin shim which is located in the initial assembly and becomes an integral part of the filling.

Other objects and advantages of the invention will become apparent from the following detailed description taken in connection with the accompanying drawings, in which:

FIGURE l is a fragmentary diametrical sectional View of a friction clutch embodying the novel features of the present invention.

FIG. 2 is an eight-times enlargement1 of a part of FIG. 1.

FIG. 3 is a perspective view of the ring forming the non-magnetic gap.

The improved filling construction is especially suited for use in a friction coupling of the general type shown in which driving and driven members and 11 are frictionally coupled together by winding up a helical spring coil 12 to contract a split friction band 13 around surfaces 14 and 15 on the members axially spaced along the clutch axis. The coil is formed of wire of magnetic material and narrow rectangular cross-section, one end being anchored at 16 on the driven member. The opposite end turn 17 constitutes the armature of a magnetic pilot clutch having annnular pole pieces 18 and 19 carried by the driving member 10 and secured together in closely spaced edge to edge relation with their exposed faces 20 and 21 disposed flush with each other and closely adjacent the axial face of the armature 17 which, by bending of the wire of the coil, is disposed in an axial plane.

The magnet pole faces are radially separated by a narrow gap 22 which is disposed midway between the inner and outer edges of the armature. At their opposite ends, the pole pieces 18, 19 are formed with surfaces 23, 24 which are concentric with the clutch axis and telescope with inner and outer legs of a stationary magnetic core 25 of U-shaped cross-section enclosing a multiple turn winding 26. When the latter is energized, magnetic flux threads the toroidal path 27 which extends around the gap 22 and into and out of the inner and outer portions of the armature 17. The latter is thus drawn into gripping engagement with the pole faces thereby developing a friction torque for winding up the coil 12 to engage the clutch.

Rigid joining of the poles pieces 18, 19 is achieved by a ring 30 of non-magnetic material `such as bronze Patented May 25, 1965 "ice melted and flowed as by a welding torch into a groove delined by opposed surfaces 31, 32 on the pole pieces diverging away from each other from an apex 33 which is axially spaced a short distance away from the pole faces so as to leave cylindrical surfaces 34 on the opposed edges of the pole pieces. These surfaces are machined accurately so as to be precisely concentric with the axis of the pole rings.

In accordance with the present invention, the gap 22 separating the edges 34 of the pole rings is formed of a thin strip 36 of shim stock usually about .006 of an inch thick bent into the form of a cylinder as shown in FIG. 3 and composed of brass or other non-magnetic metal which will bond with the metal of the filling 30 but will not be destroyed during flowing of the latter into the groove 31, 32. The strip is substantially wider than the edge surfaces 34 so that when one edge portion 37 is disposed between these surfaces and flush with the pole faces 20, 21, the opposite edge portion 33 will extend well into the apex portion of the groove. In the welding of the lling into this groove, the molten bronze flows around the portion 3S and becomes bonded thereto.

With part of the strip thus firmly embedded in the lilling, the portion 37 which forms the gap 22 will be held securely between the pole edges and completely filling the space between the two with solid non-magnetic metal and of a thickness determined by that of the shim. The

latter wears away with the pole faces in service use but1L there is no possibility of accumulating between the edge surfaces 34 any iron particles that would afford paths for by-passing flux directly between the pole pieces. By using a separate metal strip to form the gap 22, the width and the uniformity thereof are established with great accuracy and at low cost while providing a filling of the desired diverging cross-section. That is to say, the pole pieces are formed in simple machining operations and no elaborate fixturing is required during welding of the filling into the groove.

I claim as my invention:

1. In a magnet construction, the combination of, a thin strip of non-magnetic metal, two magnetic pole pieces arranged edge to edge in surface abutment with opposite sides of one edge portion of said strip and having exposed end faces disposed in a common plane substantially flush with the edge of said one end portion, the edge surface of said pieces opposite the other edge portion of said strip diverging away from opposite sides of such portion so as to define a V-shaped groove divided by such other edge portion of the strip and a rigid metal filling disposed in said groove and bonded securely to said other edge portion of the strip and the diverging side walls of said groove so as to unite said pole pieces and said strip into a rigid structure with said pole faces and the side surfaces of said pole pieces magnetically separated by said one edge portion of said strip.

2. A magnet construction as defined in claim l in which the outer edge of said strip forms with said pole faces an uninterrupted planar surface.

3. A magnet construction as defined in claim 1 in which the thickness of said strip is on the order of a few thousandths of an inch.

References Cited by the Examiner UNITED STATES PATENTS 2,739,684 3/56 Meyer l92-84 2,798,581 7/57 Supitilov 192-84 2,857,998 10/58 Harter 192--84 3,055,470 9/62 Pierce 192--84 JOHN F. BURNS, Primary Examiner.

FRANK SUSKO, Examiner.

Claims (1)

1. IN A MAGNET CONSTRUCTION, THE COMBINATION OF, A THIN STRIP OF NON-MAGNETIC METAL, TWO MAGNETIC POLE PIECES ARRANGED EDGE TO EDGE IN SURFACE ABUTMENT WITH OPPOSITE SIDESOF ONE EDGE PORTION OF SAID STRIP AND HAVING EXPOSED END FACES DISPOSED IN A COMMON PLANE SUBSTANTIALLY FLUSH WITH THE EDGE OF SAID ONE END PORTION, THE EDGE SURFACE OF SAID PIECES OPPOSITE THE OTHER EDGE PORTION OF SAID STRIP DIVERGING AWAY FROM OPPOSITE SIDES OF SUCH PORTION SO AS TO DEFINE A V-SHAPED GROOVE DIVIDED BY SUCH OTHER EDGE PORTION OF THE STRIP AND A RIGID METAL FILLING DISPOSED IN SAID GROOVE AND BONDED SECURELY TO SAID OTHER EDGE PORTION OF THE STRIP AND THE DIVERGING SIDE WALLS OF SAID GROOVE SO AS TO UNITE SAID POLE PIECES AND SAID STRIP INTO A RIGID STRUCTURE WITH SAID POLE FACES AND THE SIDE SURFACES OF SAID POLE PIECES, MAGNETICALLY SEPARATED BY SAID ONE EDGE PORTION OF SAID STRIP.

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