Abstract:
An armature assembly support pallet has armature assembly support surfaces which exhibit a magnetic field that magnetizes the portions of the armature shaft adjacent the support surfaces so that armature assembly is magnetically attracted to the support surfaces and thereby maintained in a precise axial position on the pallet as the pallet is conveyed between work stations. The magnetic field is preferably created by thin layers of magnetic material secured to upwardly-facing surfaces of V-shaped portions of support members or blocks affixed to the body of the pallet. The pallets may be used without changes or adjustments for supporting armature assemblies having a substantial range of various different configurations. Pallets of known construction, including those with adjustable support members, may be modified or retrofitted by providing them with magnetic support surfaces.

Description:
FIELD OF THE INVENTION 
     This invention relates to an armature assembly support pallet used for conveying a partly constructed electric motor armature assembly during manufacture. 
     BACKGROUND OF THE INVENTION 
     During manufacture of electric motor armature assemblies having cores made from a stack of laminations, partially manufactured armature assemblies may be supported on support pallets conveyed by a conveyor between manufacturing stations. At one or more of the manufacturing stations, a partially manufactured armature assembly is removed from the pallet for processing by armature handling mechanisms that may include an elevator or a pick and place mechanism, and returned to the same pallet or to an essentially identical pallet by the same handling mechanisms. The handling mechanisms must be capable of transferring the armature assemblies to the processing machines in precise positions or orientations in order to be handled by the processing machines. To simplify the tasks of the handling mechanisms, an armature assembly is positioned on a conveyor pallet in a relatively accurate location. The transverse position of an armature assembly on a pallet is generally maintained by V-shaped supports that support opposite ends of a shaft forming part of the armature assembly. However, the pallets are usually so constructed that the armature assembly can be slightly displaced, on the order of one-sixteenth of an inch or so, in the axial direction of the armature shaft. Thus, the precise axial position of the armature assembly on a pallet is not maintained. Maintenance of an armature assembly location on a pallet within about one-sixteenth of an inch is usually satisfactory and will not prevent proper processing of the armature assembly. However, carefully machined stops and other devices are often needed to hold the location of an armature assembly on a pallet within tolerance. 
     Electric armature assemblies have many different parameters, such as different shaft lengths, different commutator constructions or locations on their respective shafts, or different lamination stack lengths or locations on their respective shafts. A given pallet may be dedicated for use in conveying an armature assembly of only one configuration so that different pallets will have to be provided for use with armature assemblies having different configurations. Some pallets are not so limited but are provided with readily changeable armature shaft supporting members or with adjustable, i.e., axially movable and/or rotatable, armature shaft supporting members so that the pallets are usable with a wider range of armature constructions. Examples of pallets with adjustable supporting members are described in U.S. Pat. Nos. 5,346,058 and 5,348,142. These same patents show relatively complex pallets and mechanisms for adjusting the positions of the armature shaft supporting members on the pallets. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to provide an inexpensive armature support pallet by which an armature assembly being manufactured may be maintained in a fixed axial position on the pallet while being conveyed from one workstation to another workstation. 
     Another object of this invention is to provide an inexpensive armature support pallet which is usable with armature assemblies having a substantial range of different armature configurations. More specifically, an object of this invention it to provide such a pallet which requires no changes or adjustments in order to handle armatures of different configurations. Accordingly, an armature support pallet in accordance with this invention can be used in various different armature manufacturing lines without requiring any initial set up time. If a manufacturing line is changed over from the manufacture of one armature to a different armature, the same pallet can be used, without changes or adjustments, within a large range of various different armature configurations. 
     In accordance with this invention, an armature assembly support pallet has a body member and a pair of mutually-spaced support assemblies mounted on the body member. The support assemblies support spaced-apart portions of an armature shaft. Each of the support assemblies includes a support member having upwardly-facing, shaft-engaging support surfaces. The support surfaces exhibit magnetic fields so that the portions of the armature shaft adjacent the support surfaces are magnetized and thereby magnetically attracted to the support surfaces. 
     Preferably, each of the support surfaces which exhibits a magnetic field is formed from a layer of magnetic material secured to its respective support member. In addition, the body member may have an aperture formed therein to provide access from beneath the pallet to an armature assembly carried on the pallet. If the pallet has such an aperture, the support assemblies are preferably mounted on the body member adjacent respectively opposite margins of the aperture. Also, known pallets, including those with adjustable support assemblies, may be modified or retrofitted by securing magnetic material to some or all of their support surfaces. 
    
    
     Other objects and advantages of this invention will become apparent from the following drawings and description. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partially-exploded, perspective view of an armature assembly support pallet in accordance with this invention and a partially-manufactured armature assembly which is carried by the pallet. 
     FIG. 2 is an elevational view of the armature assembly support pallet and the partially-manufactured armature assembly of FIG.  1 . 
     FIG. 3 is a partially-exploded, perspective view of an existing armature assembly support pallet that has been modified or retrofitted in accordance with this invention. 
     FIG. 4 is a partially-exploded perspective view similar to FIG. 3, but showing the pallet reconfigured to provide a different spacing between the supports. 
    
    
     DETAILED DESCRIPTION 
     With reference to FIG. 1, a pallet, generally designated  10 , in accordance with the preferred embodiment of this invention includes a body member  12  in the form of a rectangular plate having a central aperture  14 . As well known to those familiar with the art, the aperture  14  provides access from beneath the pallet  10  to an armature assembly, generally designated  16 , loaded on the pallet. Mutually-spaced support assemblies, generally designated  20 A and  20 B, which engage and support spaced-apart portions of the armature shaft  22 , are mounted on the body member  12  adjacent respective opposite margins of the central aperture  14 . 
     Referring also to FIG. 2, each of the support assemblies  20 A and  20 B includes a generally rectangular nylon block or support member  24 A and  24 B, respectively, the top portion of which is V-shaped. Each of the support members  24 A and  24 B is fixedly mounted to the body member  12  by a pair of socket-headed cap screws  17  located in recesses  18  in the support members  24 A and  24 B. The screws  17  are threaded into tapped bores  19  in the body member  12 . The support members  24 A and  24 B may be formed from a nylon material such as Nylatron™ GS nylon available from The Polymer Corporation, Reading, Pa. 19612. Nylatron™ GS nylon has been used to form pallet support members because it does not damage armature shafts. However, as will become apparent, wear due to contact between the armature shaft  22  and the support members  24 A and  24 B may be disregarded when constructing a pallet in accordance with the preferred embodiment of this invention. Therefore, the support members  24 A and  24 B of the pallet  10  may be formed from a less expensive, lower grade of nylon or any other suitable non-ferrous material. 
     It is preferred to machine straight-walled channels  30  into the support members  24 A and  24 B to partially receive a thin layer of magnetic material  28 . The thin layer of magnetic material  28  is secured in each of the channels  30  in the V-shaped portions of the support members  24 A and  24 B to maintain the axial position of a supported armature assembly  16 . Any commercially available magnetic material may be used, but it is presently preferred to form the layer of magnetic material  28  from a roll of flexible magnetic stripping such as magnetic stripping available from McMaster-Carr Supply Co., 600 County Line Road, Elmhurst, Ill. 60126. For reasons which will be described below the magnetic material  28  preferably projects above the channels  30 . 
     The magnetic material  28  is preferably secured in the channels  30  using an adhesive material. Here, it will be noted that one of two manners of securing the magnetic material  28  is contemplated, although any sufficient securing method may be used. Suitable magnetic material with an adhesive backing is commercially available and can be self-adhered to the support members  24 A and  24 B using the adhesive backing. As an option, the back surface of the magnetic material  28  and the channels  30  may be coated with an adhesive material such as Pliabond™, available from W.J. Ruscoe Co., 483 Kenmore Boulevard, Akron, Ohio 44301. Thereafter, the coated parts are placed together, and the adhesive is permitted to cure. Although the preferred embodiment described herein includes a layer of magnetic material  28  secured to each side of the V-shaped portions of the support members  24 A and  24 B, it will understood that pallets in accordance with this invention may be constructed having fewer magnetic surfaces. 
     The layers of magnetic material  28  are engaged by the armature shaft  22  when the armature assembly  16  is carried by the pallet  10 . These layers of magnetic material  28  exhibit magnetic fields that cause the portions of the armature shaft  22  adjacent the magnetic material to become at least partly magnetized in accordance with well-known physical principles. Consequently, the armature shaft  22  is magnetically attracted to the layers of magnetic material  28 . Due to the attraction between the armature shaft  22  and the magnetic material  28 , the armature shaft  22  will remain axially stationary as the pallet  10  is conveyed between workstations, absent any force sufficient to overcome the magnetic attraction. As is evident, the above-described construction is capable of maintaining the axial position of an armature assembly  16 , regardless of the configuration of the armature assembly  16 . 
     In addition to the magnetic restraint of the armature shaft  22 , the preferred magnetic material  28  also frictionally restrains axial motion of the armature assembly  16  relative to the pallet  10 . This frictional restraint is present because the preferred magnetic material  28  is formed from magnetized barium ferrite particles that are heavily interspersed throughout a soft, flexible thermoplastic material, which has a relatively high coefficient of static friction. However, it will be recognized that such frictional restraint will not be as prominent if the magnetic material has a relatively low coefficient of static friction. In such cases, it may be necessary to select a magnetic material of greater magnetic strength to achieve the desired axial restraint of the armature assembly  16 . The frictional restraint is enhanced because the magnetic material  28  projects above the channels  30  so that the armature shaft  22  does not contact the nylon support members  24 A and  24 B, which typically will have a relatively low coefficient of static friction. 
     Of course, one skilled in the art will recognize that the benefits of this invention are dependent on the material from which the armature shaft  22  is formed and the strength of the magnetic field exhibited by the layers of magnetic material. For example, the greatest benefits are obtained when the material from which the armature shaft  22  is formed has a high content of ferromagnetic material. The benefits diminish as the ferrous content of the armature shaft material is reduced. 
     The pallet  10  shown in FIG. 1 does not rely on confronting surfaces on the support assemblies  20 A and  20 B and the armature assembly  16  to restrict axial movement of the armature assembly  16 . Therefore, the pallet  10  in accordance with this invention may be used to support armature assemblies  16  of various sizes without adjustment. However, the range of armature assemblies  16  that may be carried by the pallet  10  is limited by the distance separating the support assemblies  20 A and  20 B. For example, an armature shaft  22  must have a certain minimum length to be supported by the support assemblies  20 A and  20 B. In addition, the maximum stack height and the maximum distance between the stack and the commutator of a supportable armature assembly  16  is also dictated by the distance between the support assemblies  20 A and  20 B. 
     Referring now to FIG. 3, a pallet, generally designated  110 , of known construction is shown modified or retrofitted in accordance with this invention. The known pallet  110  comprises a pair of support assemblies, generally designated  120 A and  120 B mounted on the body member  112  having a central aperture  114 , which may be identical to the body member  112 , as described above. Both of the support assemblies  120 A and  120 B of the pallet  110  are adjustably mounted on the body member  112 , as described below, so that they may be moved closer or farther from one another to provide a change in the range of armature configurations that may be carried on the pallet  110 . The pallet  110  is modified from its original construction so that the support assembly  120 B shown in FIG. 3 includes upwardly facing support surfaces formed from magnetic material  28 . In this respect, the support member  124 B is constructed in the same manner as the support members  24 A and  24 B, as described above. 
     The body members  124 A and  124 B of the support assemblies  120 A and  120 B, respectively, are not directly and fixedly mounted on the body member  112 . Rather, mounting plates  130 A and  130 B, one for each body member  124 A and  124 B, respectively, are secured to the body member  112 . The mounting plates  130 A and  130 B are each secured to the body member  112  by a pair of socket-headed cap screws  117  that pass through openings  118  in the mounting plates  130 A and  130 B and are received in the tapped bores  119 . Each of the mounting plates  130 A and  130 B has a pair of mutually-spaced mounting pins  132 A and  132 B, respectively, extending upwardly therefrom between the openings  118 . 
     With further reference to FIG. 3, the support member  124 A that forms part of the support assembly  120 A includes three axially-spaced pairs of laterally-spaced apertures  134  that extend upwardly from the bottom surface of the support member  124 A. Each pair of apertures  134  is so spaced and dimensioned that the support member  124 A may be positioned above the mounting plate  130 A to align any one of the pairs of laterally-spaced apertures  134  with the mounting pins  132 A. To mount the support member  124 A on the mounting plate  130 A, the support member  124 A is lowered with a pair of the apertures  134  aligned with the pins  132 A so that the pins  132 A are snugly received in the apertures  134 . 
     The support member  124 A may be removed from the pins  132 A and moved axially to another position wherein another pair of apertures  134  is aligned with the pins  132 A so that the pins are received in the other pair of apertures  134 . By so moving the support member  124 A, it may be moved closer to or farther from the center of the pallet  110  to accommodate different armature configurations. The support member  124 A also includes a stop pin  136  projecting upwardly in the V-shaped portion of the support member  124 A. The stop pin  136  serves to limit axial motion of a supported armature assembly  16  in the direction of the support member  124 A. 
     Again referring to FIG. 3, the support member  124 B has a single pair of laterally-spaced apertures  134 B formed therein that extend upwardly from the bottom surface of the support member  124 B. As with the support member  124 A, the apertures  134 B are spaced apart so that they may be aligned with the mounting pins  132 B. The support member  124 B is mounted on the mounting plate  130 B, plate  130 B being secured to the body member  112 , by aligning the pair of apertures  134 B with the pins  132 B and lowering the support member  124 B so that the pins  132 B are snugly received in the apertures  134 B. So that the support member  124 B is readily adjustable, the pair of apertures  134 B is offset toward the face  138  of the support member  124 B. The support member  124 B may be mounted on the pins  132 B in one of two different orientations, depending on the direction in which the face  138  faces. The support member  124 B is reoriented by removing the support member  124 B from the pins  132 B and remounting the support member  124 B on the pins  132 B so that the face  138  faces in the opposite direction, as shown in FIG.  4 . Due to the off-center nature of the apertures  134 , such reorientation locates the support member  124 B either closer or farther from the center of the pallet  110 . 
     In many instances, the armature assembly  16  is loaded onto the pallet  110  with the commutator  140  (FIG. 1) in contact with the support member  124 B, which limits axial movement of the armature assembly  16  toward the support member  124 B. In such instances, axial movement of an armature assembly  16  carried on the pallet shown in FIG. 3 is limited in one direction by engagement of the stop pin  136  with the armature shaft  22  and in the other direction by engagement of the commutator  140  with the support member  124 B. Thus, no magnetic material  28  is needed to maintain the axial position of the armature assembly  16 . However certain situations require the armature assembly  16  to be carried on the pallet  110  before the commutator  140  is placed on the shaft  22 . In such situations, the armature assembly is free to move axially in the direction of the support member  124 B. Therefore, the pallet  110  may be modified or retrofitted in accordance with this invention, as shown in FIG. 3, to include support surfaces formed from a layer of magnetic material  28  secured to the support member  124 B to prevent axial movement of the armature assembly  16  (without a commutator  140 ) in the direction of the support member  124 B. If the magnetic material  28  is secured to the support member  124 B, channels are preferably formed in the support member  124 B and the magnetic material is secured in the channels as described above regarding support member  24 A and  24 B. 
     It will be recognized that the mounting and adjustment procedures described above for support members  124 A and  124 B may be used for support members of other configurations. For example, the support members may be L-shaped or may have various different numbers of pairs of apertures formed therein. In addition, pallets may be constructed so that both of the support assemblies are fixed or so that both are adjustable as described above. If only one support assembly is adjustable, it may be adjustable by removal and axial movement, as the support member  124 A, or by removal and replacement as described above with respect to either the support member  124 A or the support member  124 B. If both support assemblies are adjustable as shown in FIGS. 3 and 4, they may each be adjustable by removal and replacement as described above with respect to either the support member  124 A or the support member  124 B. 
     Although the presently preferred embodiments of this invention have been described, it will be understood that within the purview of the invention various changes may be made within the scope of the following claims.