US 3119034 A
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Description (OCR text may contain errors)
Jan. 21, 1964 F.ko.LuEr"1BERGER 34,119,034
MAGNETIC CLUTCH Filed July 25, 1961 2 sheets-sheet 1 .FI/Ga In Y lJINVENTOR EpEe/cz [aa/BERGER BYJZMM/ rrakwsys.
United States Patent O 3,119,034 MAGNEIHC CLUTCH Frederik (D. Ltrenherger, .llos Angeles, Calif., assigner, by nies-ne assignments, to lhe Emerson Electric Manu.- facturing Company, St. Louis, Mo., a cn-rporation of lllissouri Filed .luly 25, 1961, Ser. No. 126,558 3 Claims. (Cl. S10-105) This invention relates to a magnetic or eddy-current clutch.
Typical eddy-current clutches are illustrated in patents to King, 2,864,015 and 2,871,383, and to laeschke, 2,971,105. A driving and a driven shaft are provided. Either shaft may be the driving shaft, the other being the driven shaft. One shaft carries an eddy-current drum that is cylindrical in form. The other shaft carries a toothed rotor of magnetizable material that lits, with slight clearance within the eddy-current drum. A nonrotary tield coil carried by the frame or housing sends magnetic flux through the drum Iand the rotor so as to establish a coupling between the eddy-current drum and the rotor.
Uniform ux distribution, eiiicient use of the iron material of the frame, and operation according to design depends upon providing and maintaining within reasonably ,accurate limits, the concentricity and dimensions of the various air gaps. Often, in order to provide substantial braking -torques, the eddy-current drum is of substantial axial length so as to multiply the capacity. As the axial length of the eddy-current drum increases, it becomes increasingly diii'icult accurately to provide required Conlcentricity during manufacture processes, and to hold such concentricities after installation.
The primary object of this invention yis to provide an improved eddy-current clutch in which high tolerances yand `concentricity of parts is readily provided and maintained.
Another object of this invention is to provide an improved magnetic circuit arrangement for an eddy-current clutch or the like whereby it is possible easily to obtain access to the field coil, all in contrast to the usual arrangement which requires virtual disassembly of housing parts for such purpose. A companion object of this invention is to provide a lone-piece, rather than a two-piece, field structure.
in order to accomplish the foregoing objects, the nonrotary magnetic frame and the companion eddy-current drum are uniquely designed. The frame and drum are both formed as tubular members, the fra-me having an inwardly directed flange at one end, and the drum having an outwardly directed llange at the vother end. The field coil ts within the sleeve of the frame, and is enclosed on opposite sides by the tlanges of the drum and the frame. The flanges are quite massive. The large massive drurn flange makes it easier to provide and hold concentricity and tolerances. The mass of the frame has been reduced in comparison with prior devices; yet a substantial mass at one end serves as an adequate anchor to ensure concentricity and maintenance of tolerances. The radii of the two transfer air gaps between the drum and the frame, instead of being of the same size, are of ditferent size, but without any essential functional change. The cylindrical internal contiguration of the eddy-current drum is retained for cooperation with the rotor.
This invention possesses many other advantages, and has other objects which may be made more clearly apparent from `a consideration of one embodiment of the invention. For this purpose, there is show-n a form in the drawings accompanying and forming a part of the present speciication. This form will new be described 3,11%@34 Patented `lain.. 21, 19x64 2, in detail, illustrating thegeneral principles of the invention; but it is to be understood that this detailed description is not to be taken in .a limiting sense, since the scope of this invention is best defined by the appended claims.
Referring to the drawings:
FIGURE l is an axial sectional view of the magnetic clutch incorporating the present invention; and
FIG. 2 is an enlarged transverse fragmentary sectional view taken along the offset plane indicated by line 2-2 of FIG. l.
In FIG. l there is illustrated a housing for the operative partsr of the magneti-c clutch. The housing cornprises a central tubular frame 10 4and end bells 11 and 12 attached to the frame at its opposite end surfaces 10a and 10b by `cap screws (not shown). IDriving and driven shafts 13 and 14 extend coaXially into the housing and are supported by the end bells 11 and 12. The role of these shafts may be interchanged. The inner end of the ldriven shaft .14 is in this instance received or piloted within a recess 15 at the inner end of the driving shaft 13. A ball bearing structure 16 has outer and inner races respectively carried I,by the shafts 13 and 14- at the bottorn of the recessy 15. The driving shaft 13 projects only slightly into the housing, whereas the driven shaft eX- tends almost across the entire housing. The end bell 11.
supports the driving shaft 13 by the aid of a bearing structure 17, and the end bell structure 12 supports the `driven sha-ft 1d by the aid of a bearing structure 18.
An eddy-current drum `191s carried by the driving shaft 13 `for rotation therewith. An end bracket Ztl supports one end of the eddy-current `drum 19 and is fastened as by welding, to a llange ring 13a of the driving shaft 13. An end bracket 21 for supporting the other end of the eddy-current drum 19 is journalled to the end bell 12. For this purpose, the bracket 21 mounts a hollow shaft 22, the outer end of which is received -in a bear-ing structure 23 located just inwardly of the driven shaft supporting bearing 18. The shaft 22 is rotatable about shaft 1d.
A conventional magnetizable rotor 24, carried by the driven shaft 1'4 at the center of the housing, has teeth 25 (FlG. 2) the crests 26' of which are slightly spaced from the interior cylindrical surface 27 of the eddy-current drum 19.
Water or suitable coolant is circulated through the housing, there being illustrated in FIG. 1 an inlet conduit 28 at the end bell 11 and an outlet 29" at the end bell 12 so that the coolant must traverse the eddy-current drum f1.94 and rotor 24. Conventional seals 30 and 3l cooperable with end brackets 2t) and 21 isolate the bearings lfrom the coolant and are respectively supported on the bells .11 and 112.
In order to establish the requisite coupling between the shafts 13 and 14, 'flux must pass radially inwardly at one end of eddy-current drum 19 along the rotor teeth 25 and radially outwardly at the other end of the eddy- :current `drum 19, and as indicated by the arrows 32. To provide such flux, an annular iield coil 34 is provided that is mounted by the iframe 1t) so that the frame 10 and the eddy-current drum 19 together surround the coil to define a circuit for the flux. The flux is caused to pass through the air gap at the interior cylindrical surface 27 by virtue of saturation at the relatively thin central band 35 of the eddy-current drum. Optionally an annular non-magnetic insert could be provided between opposite ends of the eddy-current drum.
The magnetic frame 10 is generally tubular or cylindrical, one end of the frame having a. massive radially inwardly extending wall or tiange 36. The frame 1t) may rbe considered as having a recess at one end and a counterbore at the other. The eddy-current drum 19 similarly is tubular or cylindrical, and is surrounded by the frame.
The end of the `drum opposite the fiange 36 has a massive radially outwardly extending wall or flange 37 accommodated in the counterbore area of the frame l0. The lianges 36 and 37 of the frame and drum are axially spaced in order to `define a space for the coil 34.
The coil 34 lits the interior cylindrical surface 38 of the frame, and engages the end of an annular recess 39 in the flange 36. A snap ring 4() locks the coil in place. Lead-in conductors (not shown) pass through appropriate apertures in the frame flange 36.
The outer surface 41 of the flange 37 on the eddy/- current drum 19 is cylindrically formed and opposes thei interior cylindrical surface 38 of frame lll to form a transfer air gap at one end of the device. The inner surface 42 of the frame ange 36 surrounds the cylindrical` exterior surface 43 of the eddy-current drum to fornr a transfer air 'gap at the other end of the device. The magnetic circuit for the coil 34 is thus completed.
The cylindrical end ofthe drum 19 is relatively narrow in order to provide high reluctance in an axial direction along the drum, yet low reluctance radial to the drunr whereby the rotor 24 is suitably linked. The massive flange 37 facilitates accurate machining of the surfaces 27, 4l, `and 43, the surface 43 at the thin portion extending only half the length which would be required for a corresponding conventional drum. Also, the unassive liange 37 solidly anchors the drum and precludes flexure after installation. Air gap dimensions are thus readily provided and maintained.
The frame l@ is also yet massive enough to facilitate accurate machining of cylindrical surfaces and their maintenance thereafter. The one piece construction of the frame l@ is also a simplification, and the coil 34 can be readily removed and replaced.
The inventor claims:
l. 'In an eddy-current device having a pair of relatively rotatable shafts and a -rotor coupled to one of the shafts, the combination therewith of: an eddy-current drum coupled to the other of the shafts, and having axially elongated interior cylindrical sur-face means surrounding said rotor, said drum having a radially outwardly extending wall surrounding a substantial portion of the axial length of the said interior cylindrical surface and adjacent one end of said interior cylindrical surface; said wall being unitarily formed on the drum; said wall having an annular surface beyond the interior cylindr-ical surface; the cross-sectional area o-f the drum in planes spaced from the Wall being relatively reduced, and pro- 'viding a peripheral cylindrical surface; a relatively nonrotary magnetic frame extending about `the drum and providing surfaces opposing said annular surface and said peripheral cylindrical surface; and a coil carried by the frame for circulating flux through the druni and the rotor.
2. In an eddy-current device having a pair of relatively rotatable shafts and a rotor coupled to one of the shafts, the combination therewith of: an eddy-current drum coupled to the other of the shafts, and having interior cylindrical surface means surrounding said rotor, .said drum having a radially extending wall at one and and unitarily :formed therewith providing a first exterior cylindrical surface, the other end of said drum being rela- `tively reduced, and providing a second exterior cylintdrical surface; a relatively non-rotary magnetic iframe circumscribing the drum, said magnetic frame having a .iirst cylindrical interior surface extending inwardly from -one end and opposing the said first exterior cylindrical ,surface lof said `drum to form therewith a first flux trans- '.lfer air gap; said frame also having a radially inwardly yextending Wall at its other end, and provided with a second interior cylindrical surface opposing said second exterior cylindrical surface of said drum to `form therewith a second flux transfer air gap; and an annular coil received within said first interior cylindrical surface for mounting by said Aframe, the radial Iwalls of said frame :and said `drum closing the end access to the coil when the drum and frame are assembled.
3. In an eddy current device having a pair of relatively rotatable shafts and a rotor coupled to one of shafts: a unitary `frame having a cylindrical recess `and a cylindrical counterbore; an electromagent coil in the iframe and recessed within the counterbore; said coil having an opening providing access to said recess; an eddy current drum having provisions for attachment to the other of the shafts, one end of said drum extending into said recess with its other end surrounded by said counterllore; the said other end of said `drum having an integrally formed substantially massive peripheral fiange substantially occupying the space defined by said counterbore; said drum having a cylindrical internal surface extending `through both of said drum ends, the respective ends of said `cylindrical internal surface forming boundaries of working air gaps; said drum ends having peripheral cylindrical surfaces of differing diameters annularly opposing the cylindrical recess and the cylindrical counterbore respectively to form boundaries of liux transfer gaps.
References (Iited in the file of this patent UNITED STATES PATENTS 2,193,214 Winther Mar. 2, 1940