Motor stator stack op bonded laminations with less bonding material at bolt hole regions
US RE26788 E
Description (OCR text may contain errors)
Re. 26,788 MOTOR STMOR STACK OF BONDED mmmnxous WITH ous Feb. 10, 1970 a. a. HULL LESS BONDING MATERIAL AT 30m HOLE REGI Original Filed June 26, 1964 SheetsF-Sheet l INVENTOR- ob/Z? 5. )70/4 BY Re. 26,788 ous WITH B. B. HULL Feb. 10, 1970 MOTOR STATOR STACK OF BONDED LAMINATI LESS BONDING MATERIAL AT BOLT HOLE REGIONS Original Filed June 26, 1964 4 Sheets-Sheet 2 60 602. 5. Hu/l, by )M.
Feb. 10, 1970 B a HULL Re. 26,788
MOTOR STATOR STACK OF BONDED LAMINATIONS WITH LESS BONDING MATERIAL AT BOLT HOLE REGIONS Original Filed June 26, 1964 4 Sheets-Sheet 5 Feb. 10, 1970 a. a. HULL Re. 26,788
MOTOR STATOR STACK 0P BONDED LAMINATIONS WITH LESS BONDING MATERIAL AT BOLT HOLE REGIONS Omginal Filed June 26, 1964 4 Sheets-Sheet 4 7 n 6 4 5 2 6 M 2 3 A 1 6 1 I :II 5
5 m M 9 PHWMIH|||H u I I l l l l I 9 l I! l l ii III: F A n I l l 1 My I I l a I I I an a w A\.\/\/3.\| w V & 4 5 M H 3 U 5 5 m M E: .525 13:5 BLUE 6 M p 4 M M United States Patent 26,788 MOTOR STATOR STACK 0F BONDED LAMINA- TlONS WITH LESS BONDING MATERIAL AT BOLT HOLE REGIONS Bobbie B. Hull, Holland, Micl1., assignor to General Electric Company, a corporation of New York Original No. 3,299,304, dated Jan. 17, 1967, Ser. No. 378,100, June 26, 1964. Application for reissue Jan. 13, 1969, Ser. No. 802,693
Int. Cl. H02k 1/06, /02 U.S. Cl. 310-217 11 Claims Matter enclosed in heavy brackets I: appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.
ABSTRACT OF THE DISCLOSURE Magnetizable core having low compressibility characteristics comprises a plurality of stacked laminations secured together by hardened interlaminate bonding material. Separated interlaminate pressure regions under compression during change of the bonding material from an anhardenezl to a hardened state form means for imparting low compressibility characteristics to the core. The compression of the pressure regions determines the quantitative distribution of bonding material between next adjacent laminations. The thickness of the hardened interlaminate bonding material at locations other than the interlaminate pressure regions is greater than the thickness of the hardened interlaminate bonding material in the vicinity of the interlaminate pressure regions.
The present invention relates in general to a core for an electrical inductive device, and more particularly to an improved stator especially suitable for use in hermetic motor units.
In the construction of dynamoelectric machines, a stator is usually provided with a laminated core formed of a number of superposed laminations secured together in stacked relation as by a welded structure extending entirely across the periphery of the stock of the type disclosed in U.S. Patent 2,448,785, issued to L. M. Dolan on Sept. 7, 1948. For some dynamoelectric machine applications, as for example, in certain hermetically built refrigeration motor compressor units, it is customary to mount the stator and rotor members for relative rotation wiLhin a motor chamber. In one generally accepted approach, the stator is secured to a stationary frame and supported at one end only with a cantilever type mount to dispose the axis of the rotor receiving bore horizontally within the chamber, co-axial with the axis of the bearings carried by the unit which support the rotor and its shaft. That is to say one side face of the laminated stator core is normally machined to provide an accurately dimensioned wall perpendicular both to the rotor bore of the core and to the rotational axis of the rotor. This finished face at the core is mounted firmly against a machined or otherwics accurately finished plannar surface, located within the motor chamber also formed perpendicular to the axis of rotation for the rotor. A number of mounting bolts extend entirely through the stator core and project into threaded holes tapped into the planar surface of the chamber. These bolts place a compressive load and torsional force on the stator core, the stator laminations being compressed between the bolt heads and the planar surface. This arrangement is intended to position the rotor receiving bore of the stator in a precise, concentric relation to the horizontal axis of the roior so that when both members are supported in the chamber, a generally uniform air gap is defined between the two members, e.g.,
in the order of 10 mils across the gap for many applications.
Unfortunately, this generally accepted approach has certain drawbacks which detract from its satisfactory utilization. For example, in spite of the welds or other mechanical lamination securing means provided at a number of angular locations entirely across the axial length of the laminated stator core, the laminations have a tendency to shift radially relative to each other when the stator is mounted to the planar frame surface. This relative lamination shifting, in turn, destroys the cO-axial relation of the individual laminations which might have been attained during the formation of the stock and produces a non-uniform air gap, and misalignment between the rotor periphery and the stator bore. Such misalignment results in a noticeable loss of output power for the motor due at least in part to eddy current losses created in the motor. In some cases, the misalignment is sufgciently great to prevent rotation of the rotor in the stator ore.
In studying this problem, I have found that the probable reasons for or factors affecting the radial tendency to shift with the resulting misalignment are complex in nature and may be cumulative in effect. By way of illustration, sudden impact or shock loads transmitted to the core after it is formed but before it has been finally mounted, as by accidentally dropping the core on a hard surface or otherwise mishandling it, may have an adverse effect on the alignment characteristics of the core. In addition, during bolt down of the stator core onto the planar frame surface, uneven or unbalanced torsional compressive loads are applied to the core as the bolts are individually tightened in place, tending to create radial relative shifting of the laminations even though they have been secured together with Welds or the like as previously mentioned. For unusually long or heavy stator cores, the core laminations at the free end of the core, that is, remote from the planar surface, tend to shift in a radial direction relative to the remaining laminations due partly to the cantilever type of mounting involved. Another factor upon the tendency to shift is the radial magnetic force produced by the pull of the rotor during motor operation on the individual stator laminations in the vicinity of the bore.
In certain refrigeration motor-compressor applications, such as hermetically sealed compressors, the relative lamination movement problem becomes even more acute. By way of example, it is necessary in many circumstances to remove moisture from the rotor, stator, and other components after the stator has been mounted to the planar frame surface, and after final assembly in the motorcompressor unit so that a minimum amount of moisture is present in the hermetically sealed unit. Thus, these parts are generally subjected to elevated temperatures for prolonged periods; e.g., above C. for 4 hours or more, to evaporate or otherwise vaporize the moisture which may be contained in the parts. In some cases, this procedure is repeated to insure moisturefree components. However, while this procedure may achieve the desired results of removing moisture from the parts, the individual laminations tend to move relative to one another, both axially and radially, when subjected to the prolonged high temperature condition. I have determined after a careful review and study of the foregoing factors, problems, and considerations that, generally speaking, the higher the compressibility characteristics of the laminated core, the greater will be the tendency of the individual laminations to shift radially relative to one another, regardless of the cause or causes producing the shift. By compressibility characteristics" is meant the total amount of compression or reduction in length the core experiences in an axial direction for a given load.
It is therefore a general object of the present invention to provide an improved laminated core for an electrical inductive device and it is a more specific object to provide a stator which overcomes the difiiculties and problems mentioned above.
It is another object of the present invention to provide an improved laminated stator core especially suitable for use in refrigeration motor-compresor application and its method of manufacture which has low com pressibility characteristics and little tendency for relative radial movement of the individual laminations.
It is yet another object of the invention to provide an improved laminated stator core having one end face made perpendicular to its bore and adapated for cantilever mounting to a planar surface, which is capable of retaining a predetermined aligned relationship of laminations achieved during its manufacture, compresses axially in substantially the same manner under the repeated application of preselected forces such as might occur from installing, disassembling, and remounting the stator to its support, and does not require a machining operation of the end face.
It is a still further object of the present invention to form improved laminated cores which are of uniform quality with the relative positions of the laminations being mechanically stable and are capable of manufacture by an improved yet low cost process.
In carrying out the objects in one form thereof, I provide an improved stator especially suitable for mounting one of its side faces onto a planar surface in a refrigeration motor-compressor unit. The stator includes a laminated core having a number of laminations arranged in stacked relation, with each of the laminations having a plurality of selected holes aligned to form passageways extending entirely through the core. A thin film of hardened thermoresponsive adhesive material is disposed between adjacent laminations to bond the laminations together with the areas immediately surrounding the individual holes being substantially free of the adhesive material. Consequently, when bolts or the like are employed to secure the core to the planar surface and hold the stator laminations under compression, the areas surrounding the selected holes will be placed in engagement with one another so that the bolt load is absorbed directly by lamination-to-lamination contact at that location. With the foregoing structure, upon repeated application of bolt pressure, the individual laminations at pressure regions or in the vicinity around each passageway will assume the same general relative position, the core will be mechanically stable, having negligible tendency for the laminations to move radially with respect to one another and the laminations at the separated pressure regions will tend to assume substantially the same relative compressive positions and to be positioned closer together at those regions than the thickness of the thin film of hardened adhesive material.
By a further aspect of the present invention, which now forms the subject matter of and is claimed in the co-pending application Ser. No. 564,155 filed July 11, 1966, I provide an improved method of forming the core. In one form of the process, the laminations are initially stacked with one side face of the stack disposed against an accurately formed planar surface. Thereafter, the laminations are accurately aligned to provide a bore having an axis extending perpendicular to the planar surface. The stack is held under compression on the planar surface by a force at each bolt hole approximating that ultimately used for mounting the stator core in the refrigeration motor-compressor unit. During the application of the predetermined compressive forces at angularly spaced apart bolt hole locations, a thin film of unhardened thermoresponsive adhesive material is applied between the individual adjacent laminations, with the areas surrounding the individual holes being kept as free from the material as possible. After the film has been hardened. the compressive forces are removed to furnish a core of rigid construction having the desired features mentioned above. In addition, the side face of the core adapted for mounting to a planar surface in the motor-compressor unit need not be machined in order to provide a bore axis which extends perpendicular from the planar surface of the unit with the desired accuracy.
The subject matter which I regard as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. My invention, itself, however, both as to its organization and method of operation, together with further objects and advantages thereof may best be understood by reference to the following description taken in connection with the accompanying drawings.
In the drawings:
FIG. 1 is a fragmentary sectional view of a hermetic refrigeration electric motor and compressor unit incorporating a stator having a core constructed with one form of the present invention;
FIG. 2 is a view taken along line 22 in FIG. 1 to show the manner in which the stator laminations are secured together;
FIG. 3 is an enlarged fragmentary view of a part of the stator of FIG. 1 to illustrate the way in which the laminations, interlaminate bonding material, and the through-bolts cooperate;
FIG. 4 is a sectional view of a step in fabricating the stator core of FIG. 1 revealing the preferred way in which the individual laminations are stacked, aligned, and temporarily secured together;
FIG. 5 is a plan view, partially broken away to show details of the apparatus and laminated stack seen in FIG. 4;
FIG. 6 is a sectional view of the aligned stack of laminations illustrated in FIGS. 4 and 5 showing the stack being immersed in suitable bonding material while the laminations are temporarily held to a fixture of the apparatus seen in FIG. 4 by through-bolts;
FIG. 7 is a schematic representation of the preferred step-by-step formation of the stator core of the exemplifieation after the core holding fixture and stacked laminations have been dismantled from the apparatus of FIGS. 4 and 5;
FIG. 8 is a partial view, partly broken away, of another manner of forming a stator core for the motor-compressor unit of FIG. 1;
FIG. 9 is an enlarged view of the stator core of FIG. 8, showing the cores mounted on a fixture having an accurately finished wall similating the mounting surface in the motor-compressor unit after the winding coils have been arranged in place in the core and the winding end turns have been formed to the desired shape;
FIG. 10 is a sectional view of the stator, including the core and windings, being immersed in a container of suitable bonding material with the stator core mounted on the fixture seen in FIG. 9;
FIG. 11 is a sectional view showing excess bonding material draining from the stator after it has been removed from the container of FIG. 10 preparatory to the hardening of the bonding material; and
FIG. 12 is a partial view broken away of the stator core formed by the procedure revealed in FIGS. 8I1 to show details.
Turning now to a more detailed description of the drawings, and in particular to FIGS. 13 inclusive, one form of the present invention is shown incorporated in a hermetically sealed motor-compressor unit, partially illustrated in FIG. 1 and generally indicated by numeral 20, suitable for use in a refrigeration system. In this exemplification of the invention, unit 20 includes a hermetically sealed cast casing 21 of conventional design forming communicating motor and compressor chambers 22, 23 respectively. The compressor chamber 23 is provided by an enlarged housing 24 cast integral with a central axial tubular extension 25 which projects into the motor chamber and mounts a sleeve type bearing 26 for rotatably supporting a section of main drive shaft 27. The main drive shaft, in turn, has a crank shaft section connected to a reciprocating piston in driving relation therewith (not shown). Since the components of the compressor part of the unit may be of any suitable and well-known standard construction, no further description will be set forth.
With regard to the illustrated details of motor chamber 22, it will be observed from FIG. 1 that casing 21 has a cylindrical cast shell 28 attached at one end to a wall of housing 24 through the intermediary of a radial flange 29 and a number of angularly spaced screws 31 extending through the flange and into complementary threaded holes provided in housing 24. The other end of shell 28 also includes a radial flange 32 which mounts an enclosure member 33, provided with the customary inlet port-valve assembly 34.
Mounted within chamber 23 for driving shaft 27 is an electric motor having a stator 40 which incorporates one form of my invention. For purposes of illustration, the mo or is of the type commonly employed in hermetic refrigeration motor-compressor units; i.e., unidirectional alternating current induction single phase, having a rotor 36 such as that shown and described in US. Patent No. 3,075,106 issued to Jerome N. C. Chi and assigned to the same assignee as the present invention. The rotor has a laminated core 37 secured to shaft 27 rotation therewith, as by an interference fit, and is counterbored at one end 38 so as to overhang extension 25 in spaced relation thereto. The outer periphery of the core is finished to form an accurately dimensioned cylindrical surface 39 made concentric to the rotational axis of shaft 27. The core carries a standard cast squirrel cage winding 35 short circuited at each end in the usual way.
Turning now to a description of stator 40, it will be observed from FIG. 2 in particular that the illustrated stator includes a laminated core fabricated from a preselected number of identical punchings or laminations 41, stamped or punched from magnetic sheet material, such as steel or the like. During the stamping operation, each lamination is provided in the usual way with a plurality of angularly and equally spaced apart generally radial, notches 42 and a central circular bore 43, with the notches and bore being in communication through narrow entrances 44. Intermediate the notches are teeth sections 46 which are joined to a yoke section 47 located outwardly of the notches, section 47 terminating in a circular peripheral outer edge 48. When notches 42 and bore 43 of the individual laminations are aligned in a manner to be described hereinafter, they form axially extending winding accommodating slols and a rotor receiving bore respectively. Each slot conventionally carries coil sides of a main running winding 50 and an auxiliary winding 51 suitably insulated from the core by any convenient means; e.g., cuffed liners 52 such as described in U.S. Patents 2,169,097 and 2,180,983 issued to Hall. The coils have end turns 54 (FIG. 1) projecting beyond the respective side faces 56 and 57 of the core which are held in a compact mass by cord 53 and phase insulators 59 are employed between windings 5t 51 in the usual way.
Before further details are outlined of stator 40, the manner in which the stator is firmly mounted in the desired location within the nzoior chamber seen in FIG. 1 will be considered. Four angularly and equally spaced apart through-bolts 61 project axially through passageways formed by aligned but slightly enlarged bolt holes 62 which may be furnished in the yoke sections of the individual laminatious adjacent edge 48 during the stamping operation. The threaded end 63 of the respective bolts (FIG. 1) is thrcadingly received in a complementary hole arranged in each of four axial, angularly spaced, casing extensions 64 made integral with housing 24. The extensions terminate in flat, accurately machined planar surfaces 66 which are all located in a common plane projecting perpendicular or normal to the rotational axis of the motor. Side face 57 of the stator core is held firmly between planar surfaces 66 and bolt heads 68 by a predetermined force, with stator bore 43 being arranged concentric to the rotational axis of shaft 27 and surrounding the rotor to define a generally annular air gap with rotor periphery 39.
As best seen in FIGS. 2 and 3, the stator core of the exemplification is constructed with hardened adhesive material 71, preferably of measurable thickness, contacting juxtaposed laminations to hold them rigidly together, which in the illustrated embodiment [by an important feature] of the present invention, does not cover next adjacent lamination sides in the regions surrounding or in the immediate vicinity of the individual bolt holes 62. These regions, denoted by numeral 72 in the figures, are generally free of material and permit controlled engagement of the next adjacent laminations at that location when bolts 61 mount the stator to planar surfaces 66, the Iurninations at the inter/animate pressure regions being movable closer together than the measurable thickness of hardened adhesive mart-rial referred to above. It has been found that with this arrangement, the core has excellent assembly stability and relatively low compressibility characteristics and the tendency of radial shift among the laminations is minimized, if not entirely eliminated. For example, during repeated assembly and dismantling of the stator onto and from planar surfaces 66, in actual practice the laminations do not appear to change their relative radial positions with respect to one another. The same is also true upon repeated heating of the stator, as might occur for example when it is being dehydrated after final installation into casing 21 or when it is in operation in unit 10. Further, unbalanced loads applied on the core as the stator is being bolted down onto surfaces 66 do not appear to change the excellent stability and alignment characteristics of the core.
It should be noted that in the preferred form not only are regions 72 substantially free of material 71, but, also, for best results, it has been found that end faces 56 and 57 should be bare; e.g., devoid of insulation, at the locations where they touch bolt heads 68 and planar surfaces 66 respectively. It should be additionally noted that even though next adjacent laminations are in pressure engagement at regions 72 in the vicinity of the bolt-holes, this contact does not detract from the beneficial results achieved in reduction of eddy current core losses resulting from the slight lamination separation effected by material 71. Of course, the precise number and size of bolt holes, their exact locations in the yoke section, and the total area of regions 72, in order to derive optimum benefits from the present invention for a given application, will be dependent upon such factors as overall size and weight of the stator, among others.
With respect to the attributes of material 71, by way of example, in the preferred embodiment it is in the form of a relatively thin interlaminate, but not necessarily continuous film (greatly exaggerated in FIG. 2) adhering to adjacent laminations. It is preferably a cured thermoresponsive high temperature insulating and bonding material, such as a thermosetting acrylic or epoxy resin type varnish. To provide the greatest possible availability of magnetic material for a given stack length, it is desirable that material 71 have a relatively thin interlaminate crosssection, the preferred manner of formation being set out hereinafter. For refrigeration applications, material 71 should also be compatible with the refrigerant of the system; that is, it should be insoluble in the refrigerant and should not be adversely affected or attacked by the system components.
Further advantages and henfiets of the present invention will become more apparent from a consideration of FIGS. 4-7 inclusive which reveal the preferred form of the process for manufacturing the stator of FIGS. 1, 2, and 3.
In one form, after the punchings or laminations 41 have been stamped or otherwise cut into the desired configuration, such as that already outlined, the punchings may be suitably annealed, and then cleaned, by any wellknown procedure (not shown). Thereafter, the laminations are stacked to a preselected height and properly aligned to form passageways for receiving through-bolts 61, axially extending slots to accommodate the windings, and rotor receiving bore 43 provided perpendicular to side face 57 of the end lamination of the stack. During alignment of the laminations, side face 57 of the stack rests upon a planar surface which, in effect, simulates the planar surfaces 66 of the housing 24. Further, the regions of the individual laminations around the individual holes forming the through-bolt passageways are held in intimate contact relations with the same type of force that the core will experience when finally assembled within cae 21 of FIG. 1. The foregoing may be achieved by stacking the laminations onto the lamination holding device 80 shown in FIGS. 4 and 5.
By way of example, the device has a removable ring 81 machined fiat on one side to provide a planar surface 82. The ring preferably extends radially beyond edge 48 of the end laminations in the stack and is detachably secured to a base plate 84 by a pair of diametrically opposite screws 85 and pins 85a. In order to align the laminations, a mandrel 86 is suitably connected to base plate 84, centrally of ring 81, with the cylindrical outer surface 87 of the mandrel disposed perpendicular to planar surface 82 of ring 81 as best seen in FIG. 4. A bolt and nut arrangement, generally indicated by numeral 88, may be used to hold the mandrel and the base plate together in assembled relation. Outer surface 87 of the mandrel includes radial projections 89 which fit into slot entrances 44 to provide axial alignment for the laminations of the stack.
Through-bolts 61, identical to those to be used in the final mounting of the core within casing 21 of the unit, are employed to bolt down the stack onto planar surface 82 of the ring with the same approximate bolt-down force as will be experienced by the core when finally mounted on surfaces 66 within the motor-compressor unit. In this way, the laminations in the vicinity of region 72 around each bolt hole will have lamination'tolamination contact.
With the predetermined force maintained on contacting region 72 around the bore holes and side face 57 of the end lamination of the stack held firmly against planar surface 82, the adhesive material 71 may be applied in an unhardened state by any convenient mariner between adjacent laminations to form the thin adhesive layer or film, best seen in FIGS. 2 and 3 and previously described.
FIG. 6 shows one way in which this application may be achieved after the stack and ring sub-assembly has been dismantled from plate 84 by removal of screws 85. The sub-assembly is subsequently mounted to a hooked carrier, generally identified by numeral 91, having suitable hooked ends 92 which extend through the opposed screw receiving openings in ring 81 to support the sub-assembly with the stack depending therefrom. The depending stack is dipped or immersed into unhardened adhesive material 71a by lowering the carrier in the manner indicated by the arrow in FIG. 6. The unhardencd material will be introduced through all exposed surfaces of the stack; e.g., bore 43, slots, and the outer periphery, in between the individual laminations to cover the teeth and yoke sections except in the regions being maintained in firm contact by bolts 61. This serves to keep the immediate area around the bolt holes free from the material. It is believed that the laminations form a wick for the adhesive material and there is a natural tendency for the material to be drawn between next adjacent laminations iii due to capillary action. This material, however, may, of course, be injected or otherwise forced between the laminations with sufi'icicnt pressure to provide adequate penetration. However, such penetration should not be so extensive as to cover regions 72 of the laminations.
After material 712. has been applied, excess material may be removed from the exposed surfaces of the core as well as ring 81 where coverage is not desired and the material subsequently hardened or solidified sufficiently to bond the laminations rigidly together. This procedure lends itself quite well to automation which is depicted schematically in FIG. 7. The stack of laminations, temporarily attached to ring 81 as previously outlined, may be assembled as a sub-assembly at a loading station to carrier 91 which in turn depends from overhead conveyor 93. The laminated stack may then be dipped as discussed in connection with FIG. 6 and transferred immediately to the next station where excess adhesive material is removed. With ring 81 disposed above the stack, the adhesive material will tend to drain away from sur' faces 57 and 82 of the stack and ring respectively. Blowers 94 or other suitable means, such as wipers or brushes (not shown) may be utilized to perform this function. The conveyor then transports the carrier and its sub-assembly through an oven 96 where heat is applied to material 71 for curing it. The exact temperature of the oven and length of cure are primarily related to the composition of thermoresponsive material 71. Finally, the carrier and its sub-assembly are cooled, as at a cooling station 97, and the stack of bonded laminations are dismantled from carrier 91. Thereafter, the bonded together stack may be placed on a continuous belt type conveyor 98 and transported to machinery for inserting slot liners 52, forming the windings and otherwise completing the fabrication of stator 40 by well-known techniques.
The following example is given to illustrate how the invention, as described above, has been carried out in actual practice and the advantages which can be derived therefrom. A quantity of stator cores were similarly fabricated in the preferred form as already outlined. The cores had a nominal bore diameter of 3% inches, an outer nominal diameter slightly over 6% inches, and a nominal stack length of 3 inches. The round laminations each had a thickness of 0.018 inch and were stamped with the type of slots and number of bolt holes shown in the illustrated embodiment of FIGS. 1-7. Four bolts, A inch in diameter, were each tightened to a torque of inch-pounds when the laminations 41 were initially mounted to ring 81 as the sub-assembly. Thermosetting acrylic and epoxy resins were used as the interlaminate adhesive material 71. Subsequent to the completed formation into stators, bolts 61 mounted the cores onto planar surfaces 66 of easing housing 2.4 with a similar bolt torque of 140 inchpounds. Each stator core and housing was then subjected to a temperature of C. for six hours for dehydration purposes. All stator cores were inspected and showed no discernible change in lamination alignment attained during their fabrication. In addition, they had good electrical qualities and their compressibility and torque retention characteristics were tested. A partial tabulation of the test results for a representative stator core is set out below:
Consequently, as indicated by the above table, the core compressed only slightly in an axial direction (average 110 produced a bolt-down torque of 140 inch-pounds) and the core did not change in either accuracy of lamination alignment or retention of the applied forces. This was the case in spit of the fact that thermosetting resin material has a well-known creepage or flow characteristic which is exaggerated at temperatures in that range, an inherent property of cross-linked materials.
The advantages and benefits of the foregoing become even more significant and striking when compared with proposed stator constructions using the same interlaminate adhesive material to bond laminations together which do not incorporate the present invention. For purposes of comparison, a number of laminated cores incorporating identical laminations with those used for the above example were bonded together to form cores of the same nominal dimensions by the procedure suggested in the M. B. Sawyer US. Patent No. 2,057,503 issued Oct. 13, 1936. Succinctly stated, the individual laminations of the stack were lowered in loose relation into unhardened adhesive material 71 and their interlaminate faces, including all surfaces of the yoke and teeth sections, were completely covered with the material. Thereafter, the yoke sections of the stack were compressed axially between a pair of rings with a pressure of approximately two tons and all but a very thin film was squeezed out from between next adjacent laminations. While this pressure was maintained on the stack, material 71 was cured. These finished stator cores were then mounted onto planar surfaces 66 by four bolts, each applying a torque of 140 inchpounds and subjected to the same heating or dehydration conditions mentioned above for the sator cores incorporating the present invention. The following are the test Thus, these cores not only had higher compressibility characteristics than the stator cores made in conformance with my invention, but they also were not stable, loosing their torque retaining qualities. Further, among other shortcomings, the alignment qualities of the individual laminations were not as satisfactory as those attained with the present invention and a repeated application of bolt torque to the cores seemed to have a tendency to change the relative positions of the individual laminations in spite of the bonding strength attributable to cured material 71.
FIGS. 8l2 inclusive show the preferred fabrication of a stator, suitable for mounting in casing 21 of FIG. 1, which has mechanical means; e.g., welds, supplementing the securement achieved by adhesive material 71. In this procedure, the material introduced between the laminations may also advantageously be applied concurrently to the interstices of the winding sides and end turns for bonding the wire turns of the winding together. In these latter figures, identical parts with those already described in connection with FIGS. 1-7 are indicated by like numerals.
After laminations 41 have been formed by a stamping operation, they are stacked into the desired height and properly aligned relative to one another on a holding device, such as that indicated by numeral 110 in FIG. 8. The illustrated device 110 includes a steel base plate 111 furnished with an upper planar surface 112 for temporarily supporting the stack of laminations. A central collet type assembly, arranged within bore 43 of the stack, is used to align the laminations. For instance, the collet has a number of individually movable elements 113, formed with arcuate-shaped outer walls 114, separated by stationary studs and are radially movable between retracted and extended positions within bore 43 of the laminations. Each element may include axial ribs 113a to fit into slot entrances 44 for alignment purposes. In the retracted position, walls 114 of diametrically disposed elements are of less diameter than that of bore 43. Any suitable means, such as coil spring 117 positioned in circular recess 118, may bias the elements toward that position.
The upper, inner Walls 119 of elements 113 are inclined to cooperate with the outer inclined wall 121 of an inverted frustoconical shape member 122, which extends downwardly into a central opening 123 in plate 111 and is connected to end 124 of a piston (not shown). Downward movement of piston end 124 to the location shown in FIG. 8 drives member 122 in that direction. During this travel, inclined wall 121 forces elements 113 from their retracted to their extended positions, overcoming the bias of springs 117. Arcuate shaped walls 114, being sectors of the same circle, will thus move firmly into engagement with the bore 43 of the laminations and, with ribs 113a, serve to align the laminations.
As the piston is being operated and elements 113 are moved to their extended positions, a preselected compressive force is applied axially to the stack, such as by curved steel blocks 127 adapted to engage side face 56. A unit force in the range of 200-1000 pounds per square inch has been found to be quite satisfactory in this regard for most applications. The blocks are, in turn, attached to a piston head 128 by coil springs 129 which act to cushion the force of the blocks as the blocks engage face 56 of the laminations. With the laminations aligned and held under axial compression, weld 131 intermediate each bolt passageway are simultaneously formed on the stack periphery for its axial length by angularly spaced and axially movable welding mechanisms 132 of standard design. For reasons to be explained hereinafter, it is desirable that the welds be located beyond the immediate vicinity surrounding bolt holes.
With the welds serving to hold the laminations firmly together in stacked relation, the stack may be blue annealed and furnished with finished windings suitably insulated from the stack. With the stator completed as shown in FIG. 9, the interlaminate oxides which may have been formed during anneal and bind next adjacent laminations together are broken and the laminatiors together are broken and the laminations finally aligned preliminary to the introduction of unhardened adhesive material between the laminations. To achieve this end, side face 57 of the end lamination of the stator is temporarilv held against planar surfaces simulating surfaces 66 in FIG. 1 and the laminations are compressed axially in the vicinity of the bolt holes 62 with the same approximate force as used in the final mounting. The equipment for accomplishing the foregoing is seen in FIG. 9 and includes a cast iron ring 141 having spaced apart upright setcions 142 each terminating in a planar surface 143 simulating in area and relationshins planar surfaces 66 of housing 24. Thus, like the exemplificntion of FIGS. 1-7, there are four equally and angularly spaced apart surfaces 143. Ring 141 is detachnbly held onto a stationary base 144 by a number of pins 145 and spring biased retainers or clamping members 146, pivotally carried by upright posts 147 located outwardly from ring 141. There is a member 146 and post to cooperate with each upright section 142.
Centrally of ring 141 and base 144 is a rigid elongated sleeve or cylindrical plug 151 having one of its ends 152 suitably secured within a recess of base 144. The other end of the plug projects upwardly, between the four sec tions 142, so as to provide an outer peripheral surface perpendicular to planar surfaces 143. Consequently, stator 40a, having the welded core and windings 50, 51 arranged in place, is assembled over plug 151 and bo ted down with a force approximating that to be used in casing 21 by four through-bolts 61 which extend through the bolt holes 62 and into complementary threaded holes 153 in sections 142. Core side face 57 will thus be located against planar surfaces 153 in the same manner as that provided by housing surfaces 66 and plug 151 will finally align the laminations. During placement of the stator core over the plug and into the position seen in FIG. 9, a rubber mallet (not shown) or other impact type apparatus may be employed against the periphery of the core for the purposes of assembly and breaking the interlaminate oxide bonds, if any. In actual practice, a plug having machined diameter of 3.120 inches has been satisfactorily used with core laminations having a to erance bore diameter from 3.125 to 3.1265 inches.
Ring 141 and stator 403. are then dismantled as a subassembly from the equipment seen in FIG. 9 and unhardened thermoresponsive material 71a may then be applied concurrently both to the end turns for filling the interstice thereof, that is, impregnating the windings, and entering any voids or spaces between next adjacent laminations of the welded core. This may readily be accomplished by a dipping step shown in FIG. 10. For instance. the sub-assembly may be attached onto a movable carrier 156 having hooked ends 157 adapted to engage ring 141 in the manner seen in FIG. 10. It should be noted at this time that ring 141 permits exposure of the winding end turns as well as the bore and outer periphery of the core so that the unhardened adhesive material 71a can readily enter the desired portions of the stator. To insure this end. stator 40a should not, of course, include any components in the bore and preferably at its outer longitudinal periphery which could interfere with the unimpeded admission of the unhardened material to the windings and between the laminations. Further, the unhardened liquid material 71a should be sufficiently fluid to allow its entry into the confines of the windings and between the laminations 41. A piston 158 and its rod 159 is shown attached to the upper end of the carrier 156 for lowering the sub-assembly into an open-ended container 161 having the unhardened adhesive material 71a.
Immediately after the application of unhardened material 71a to the end turns and between next adjacent laminations by the immersion step described above, excess material may be removed from the exposed surfaces of the sub-assembly by any convenient means. For example, the stator, indicated by numeral 40b in FIG. 11, and the ring 141 may be placed onto a V-shaped rack 162, and excess material recaptured through conduit 163 and communicating channel 164 as it drains off of the sub-assembly. If desired, of course, excess material may be wiped, brushed, or otherwise removed at this time. Finally, the material in between laminations may be hardened or cured in the manner already explained in connection with the procedure of FIGS. 4-7. When cured, the material secures the laminations together and bonds the windings into a compact mass. Obviously, in the process of FIGS. 8-11, material 71a need be applied to only one of the winding end turns or to none at all by proper masking of the winding if such is desired, but the procedure is particularly beneficial for impregnating both end turns.
As seen in FIG. 12, which shows a portion of the stator in section with the windings and related parts removed, like the embodiment of FIGS. 1-7 inclusive, regions 72 whch are devoid of interlaminate hardened adhesive material 71 surround bolt holes 62. Consequently. even with welds 131, the laminations are relatively free to make the desired intimate engagement in these locations as the stator is bolted down on planar surfaces 66 in casing 21 of FIG. 1 and the welds and material 71 conjointly secure the laminated stack securely together. While, for any given size core, the procedure of FIGS. 8-11 may not always provide as much total interlaminate surface area coverage of material 71 as that of FIGS. 4-7, the welds augment the bonding strength attributed to that material.
It should be obvious to those skilled in the art that as used herein in connection with the illustrated embodiments of FIGS. 6, 7, 10 and 11, the term unhardened material 71a may be, among other things, commercially available adhesives in liquid or highly plastic form, or in solid, finely granulated or powdered form suspended in a suitable liquid carrier. If in the latter form, the particles must be sufliciently small in order to penetrate between the laminations to the desired depth, and in the case of FIGS. 10 and 11, to become embedded Within the confines of the windings. The compactness of the windings also has a bearing on the depth of penetration achieved by material 71a. During the heating step in the illustrated embodiments, this latter type of unhardened material 71a initally coalesces into a generally integral adherent coating which then becomes hardened when it cures. Unhardened material in whatever form having a Brookfield No. 1 viscosity at 4 r.p.m. of less than centipoises should meet the requirements for most core situations known to me. It should also be recognized that magnetizable metal laminations 41 inherently include slight depressions and other irregularities on their surfaces, and that in the illustrated embodiments of the present invention, the adhesive material in its unhardened state may enter and be held in these depressions in interlaminate regions 72. However, the quantity contained by these imperfections is not sufficient to interfere with the pressure type metalto-metal engagement obtained at these interlaminate bolt hole locations.
The advantages and features of the present invention are readily manifest from the above description. It is now possible to produce an improved laminated core by a practical process particularly suitable for mass production use. The process produces stator cores, especially suitable for refrigeration motor-compressor applications, which incorporate accurately aligned laminations in a rigid stack with a minimum of variation between the individual cores so constructed at a relatively low unit cost. These stator cores have low compressibility characteristics, a high degree of stability and strength, and effectively resist, if not entirely overcome, the tendency of the individual laminations to shift radially relative to one another from causes, such as those previously listed. In addition, they retain the accurate alignment of laminations even under adverse conditions where the loads applied to the core from whatever source vary in degrees of magnitude and intensity. Further, the cores may be operated at relatively high temperatures and have nonmachined end faces mounted in cantilever supporting fashion, without producing any adverse effects on the accurate alignment ensuing from the process of their formation.
While in accordance with the patent statutes, I have described what at present are considered to be the preferred embodiments of my invention, it will be obvious to those skilled in the art that numerous changes and modifications may be made therein without departing from the invention and it is therefore aimed in the appended claims to cover all such equivalent variations as fall within the true spirit and scope of the invention.
What I claim as new and desire to secure by Letters Patent of the United States is:
1. A magnetizable laminated core for use in an electrical inductive device, said core comprising a number of laminations each having openings and a plurality of selected holes spaced from the openings, said laminations being in stacked relation with the openings and selected holes of the individual laminations being aligned to form respectively winding accommodating means and at least a plurality of passageways axially through the stack, means including a hardened adhesive bonding material disposed between and engaging next adjacent laminations securing the laminations together, the regions around the individual holes of said adjacent laminations being sub stantially free from bonding material whereby said regions adjacent the plurality of passageways of said laminations tend to assume generally the same relative compressive positions to one another upon repeated applications of predetermined compressive forces by core securing means to said regions.
2. A dynamoelectric machine stator comprising a core formed of a number of magnetizable laminations in stacked relation having a bore, winding accommodating means and a yoke section formed outwardly from said bore, each lamination including a plurality of spaced apart selected holes with the selected holes of the individual laminations being axially through said yoke section to form stator mounting means receiving passageways, means including hardened thermoresponsive adhesive material disposed between and engaging next adjacent laminations securing said laminations together, the regions surrounding the individual holes of next adjacent laminations being substantially free of hardened material with said regions being in engaging relation whereby the individual laminations in the vicinity around each passageway tend to assume generally the same relative compressive positions upon repeated application of predetermined compressive forces to said section by stator mounting means extending through said stator mounting means receiving passageways when securing the stator by the compression forces to a support.
3. A dynamoelectric machine stator comprising a core formed of magnetizable generally identically shaped laminations in stacked relation having a bore, winding accommodating means formed outwardly from the bore, at least one winding carried by said means and a yoke section formed outwardly from said means; each lamination including a plurality of selected, spaced apart holes with the plurality of selected holes of the individual laminations being axially aligned through said yoke section to form a corresponding number of bolt receiving passageways; a thin film of cured thermoresponsive resinous adhesive material disposed between and engaging adjacent laminations securing the laminations together, except in the regions immediately surrounding the selected holes forming the respective passageways; said adjacent laminations being in engagement at said regions whereby the individual laminations in the vicinity around each passageway tend to assume substantially the same relative compressive positions upon repeated applications of predetermined compressive and torsional forces to said section when bolts extend through said passageways and secure the stator with the predetermined forces to a support.
4. A magnetizable laminated core for use in an electrical inductive device, said core comprising a number of laminations each having openings and a plurality of selected spaced apart holes axially therethrough; said laminations being in stacked relation, with the openings and selected holes of the individual laminations being aligned to form respectively winding accommodating means and a plurality of spaced apart passageways axially through the stack for mounting the core; means securing the laminations together into a rigid core including hardened adhesive bonding material disposed between and engaging next adjacent laminations; the regions in the immediate vicinity of said selected holes of next adjacent laminations being substantially free of said bonding material, with next adjacent regions being engageable relative to one another, whereby the laminations form a rigid core of low compressibility and next adjacent laminations have little tendency to shift radially relative to one another upon repeated applications of predetermined compressive forces to said regions resulting from core mounting means positioned in the passageways.
5. A dynamoelectric machine stator comprising a core formed of magnetizable laminations in stacked relation having a pair of end faces, a yoke section and a bore; winding accommodating means arranged outwardly from the bore; at least one winding carried by said means, with end turns projecting away from each end face; each lamination including a plurality of selected spaced apart holes, with the selected holes of the individual laminations being axially aligned through said yoke section to form a corresponding number of bolt receiving passageways; means securing said laminations together comprising mechanical means extending transversely across the stack and hardened thermoresponsive adhesive material disposed between and engaging next adajacent laminations, with regions of next adjacent laminations immediately surrounding the selected holes forming the respective passageways being in engagement and substantially free of said hardened thermoresponsive adhesive material; hardened thermoresponsive adhesive material retaining at least the end turns of the winding in a rigid mass, whereby the Winding end turns are firmly secured in place and the laminations form a rigid core of low compressibility in which next adjacent laminations have little tendency to shift radially relative to one another even upon a repeated application of predetermined compressive and torsional forces to said yoke section as a result of bolts extending through said passageway for mounting the stator onto a support.
6. A magnetizable laminated core having low compressibility characteristics for use in an electrical inductive device, said core comprising a number of laminations each having openings and a plurality of selected holes spaced from the openings, said laminations being in stacked relation with the openings and selected holes of the individual laminations being aligned to form respectively winding accommodating means and at least a plurality of passageways axially through the stack, means for causing the laminations in the vicinity of the selected holes to tend to assume generally the same relative compressive positions to one another upon repeated subsequent applications of predetermined compressive forces to said core and for imparting low compressibility characteristics to the core, said latter means including a hardened adhesive bonding material having a measurable thickness disposed between next adjacent laminations engaging next adjacent laminations and securing the laminations to gether, areas adjacent the individual holes of adjacent laminations forming separated interlaminate pressure regions determined by predetermined compressive forces applied thereto during change of the adhesive bonding material from an unhardened to a hardened state, said laminations at the interlaminate pressure regions being movable closer together than said measurable thickness.
7. The magnetizable laminated core of claim 6 in which the adhesive material is a cured thermoresponsive resin having a Brookfield No. I viscosity at 4 rpm. in its uncured state below centipoises.
8. A dynamoelectric machine stator comprising a core formed of magnetizable generally similarly shaped laminations in stacked relation having a bore, winding accommodating means formed outwardly from the bore, at least one winding carried by said means and a yoke section formed outwardly from said means; each lamination including a plurality of selected, spaced apart holes with the plurality of selected holes of the individual laminations being axially aligned through said yoke section to form a corresponding number of stator-mounting passageways adapted to receive mounting means; means for causing the laminations in the vicinity of the selected holes to tend to assume the same relative compressive positions to one another upon repeated subsequent applications of predetermined compressive forces to the core, said last mentioned means including cured thermoresponsive resinous adhesive material having a measurable thickness disposed between and engaging adjacent Iaminations to secure the laminations together, and separated pressure regions in the vicinity of selected stator-mounting passageways of adjacent laminatio-ns defined by compressive forces independently applied to each region as said resitlOtls adhesive material is being cared from an uncured state such that the individual laminations at said sepa rated pressure regions tend to assume substantially the same relative compressive positions and to be positioned closer together at the interlaminate pressure regions than said measurable thickness upon repeated applications of predetermined compressive and torsional forces to said section when mounting means extend through said selected stator-momzting passageways for securing the stator onto a support.
9. The dynamoelectric machine stator of claim 8 in which the core includes at least one end lamination having unmachined separated planar surfaces in the vicinity of the selected bolt receiving passageways adapted to be mounted to the support.
10. A magnetizable laminated core having low compressibility characteristics for use in an electrical inductive device, said core comprising a number of laminations each having openings and a plurality of selected holes spaced from the openings, said Iaminations being in stacked relation with the openings and selected holes of the individual laminations being aligned to form respectively winding accommodating means and at least a plurality of passageways axially through the stack, means for causing the laminations to tend to assume generally the same relative compressive positions to one another upon repeated subsequent applications of predetermined compressive forces to said core, said means imparting low compressibility characteristics to the core and including an intcrlaminate film formed of hardened adhesive bonding material disposed between next adjacent laminations, said bonding material engaging next adjacent laminations and securing next adjacent laminations together, said means for imparting low compressibility characteristics to said corc further including areas adjacent the individual holes of said adjacent laminations forming separated interlaminate pressure regions that have been held under compression by predetermined compressive forces as said adhesive bonding material is changed from an unhardened to a hardened state, the thickness of hardened bonding material at locations other titan said interlaminate pressure regions being greater than the thickness of the hardened bonding material in the vicinity of the interlaminate pressure regions.
11. The laminated core of claim If) in which the core includes at least one end lamination having separated planar surfaces in the vicinity of a plurality of the passageways adapted to be mounted to a support, said separated planar surfaces lying in a desired plane substantially normal to the bore, thereby to eliminate the need to machine said planar surfaces in order to have said planar surfaces lie in such desired plane.
References Cited The following references, cited by the Examiner, are of record in the patented file of this patent or the original patent.
WARREN E. RAY, Primary Examiner US. Cl. X.R. 310--42, 45