PCT
`
`WORLD INTEIJJECI'UAL PROPERTY ORGANIZATION
`International Bureau
`
`INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(51) International Patent Classification 6 =
`
`(11) International Publication Number:
`
`WO 96/31936
`
`H02K 15/12, 15/16, 5/22, 5/08
`
`(43) International Publication Date:
`
`10 October 1996 (10.10.96)
`
`(21) International Application Number:
`
`PCT/US96/04723
`
`(22) International Filing Date:
`
`3 April 1996 (03.04.96)
`
`(81) Designated States: AU, CA, CN, JP, KR, MX, N2, 86,
`European patent (AT, BE, CH, DE, DK, ES, FI, FR, GB,
`GR, IE, IT, LU, MC, NL, PT, SE).
`
`(30) Priority Data:
`08/415,639
`
`3 April 1995 (03.04.95)
`
`Published
`With international search report.
`
`US
`
`
`
`An electrical motor and the
`process for forming that motor uti-
`lizes injection molding techniques to
`unitize the stator assembly. The sta-
`tor assembly (21) includes a stator
`lamination stack (27) and preferably
`a metal from end cap (26) which is
`secured to the lamination stack (27)
`after the lamination stack is insulated
`and wound. The windings are tenni-
`nated at a plurality of conductive pins
`(94) fusion welded to the terminating
`ends of the windings. The stator as-
`sembly (21) with front end cap (26)
`in place is positioned in an injection
`molding die. Pressure is applied to
`the die, and molten plastic is injected
`under pressure to fill voids in the sta-
`tor assembly, and also to form a plas-
`tic mass which will serve as the rear
`end cap (25). The rear end cap (25) is
`also molded with a connector portion
`(41) which fixes the conductive pins
`(94) in place as a pan of the connec-
`tor. A bore (30) formed in the stator
`assemny provides mounting surfaces
`(31, 32) for bearings (23, 24) on a rotor assembly (20).
`
`(71) Applicants: E.l. DU PONT DE NEMOURS AND COMPANY
`[US/US]; 1007 Market Street, Wilmington, DE 19898
`(US). PACIFIC SCIENTIFIC COMPANY [US/US]; 4301
`Kishwaukee Street, Rockford, IL 61105 (US).
`
`(72) Inventors: TRAGO, Bradley, A.; 922 Cerasus Drive, Rockford,
`IL 61108 (US). BYRNES, Edward, 1.; Unit #ID, 116
`Woodland Court, Carpentersville, IL 60110 (US). NEAL,
`Griff, D.; Unit 31, 2600 North Southport Avenue, Chicago,
`IL 60614 (US).
`
`(74) Agent: WALKER, R, Michael; E.I. du Pont de Nemours and
`Company, Legal/Patent Records Center, 1007 Market Street,
`Wilmington, DE 19898 (US).
`
`(54) Title:
`
`lNJECI'ION MOLDED MOTOR ASSEMBLY AND METHOD OF FABRICATION
`
`(57) Abstract
`
`Petitioners' Exhibit 1003, pg. 1
`
`Petitioners' Exhibit 1003, pg. 1
`
`

`

`Viet Nam
`
`Amenia
`Austria
`Auslnlia
`Barbados
`Belgium
`Burkina Faso
`Bulgaria
`Benin
`Brazil
`Belarus
`Canada
`Cenn'al African Republic
`Congo
`Switzerland
`can d’lvaire
`Cameroon
`China
`Czechoslovakia
`Czech Republic
`Germany
`Denmark
`
`FOR THE PURPOSES OF INFORMATION ONLY
`
`Codes used to identify States party to the PCI‘ on the front pages of pamphlets publishing international
`applications under the PCI‘.
`
`AM
`AT
`AU
`BB
`BE
`BF
`BG
`3.]
`BR
`BY
`CA
`
`United Kingdom
`Georgia
`Gurnea
`
`Democratic People's Republic
`of Korea
`Republic of Korea
`Kazakhstan
`Liechtenstein
`Sri Lanka
`Liberia
`Lithuania
`Luxembom'g
`Latvia
`Monaco
`Republic of Moldova
`Madagascar
`Mali
`Mongolia
`Mauritania
`
`Malawi
`Mexico
`Niger
`Netherlands
`Norway
`New Zealand
`Poland
`Portugal
`Romania
`Russian Federation
`Sudan
`
`Tajikistan
`Trinidad and Tobago
`Ukraine
`Uganda
`United States of America
`Uzbekistan
`
`Petitioners' Exhibit 1003, pg. 2
`
`Petitioners' Exhibit 1003, pg. 2
`
`

`

`
`
`WO 96/31936
`
`PCTfU896/04723
`
`l
`
`INJECTION MOLDED ROTOR ASBEHBLY AND
`METHOD OF FABRICATION
`
`
`
`Wigwam
`
`W T
`
`he present invention relates to electric motors,
`
`and more particularly to a fabrication method and
`
`related assembly of potted electrical motors.
`
`I.
`
`.
`
`E
`
`ll
`
`E J
`
`l
`
`I
`
`E
`
`I
`
`United States Patents 4,922,604 to Marshall et a1.
`
`and 5,008,572 to Marshall et a1., both assigned to an
`
`assignee of the present invention and hereby
`
`incorporated by reference, describe an electrical motor
`
`and fabrication method for achieving precise bearing
`registration of an internally disposed rotor assembly.
`As described more fully in the aforementioned
`
`references, an electrical motor comprising stator and
`
`rotor assemblies is fabricated by utilizing a potting
`
`compound to both unitize the stator assembly and provide
`improved thermal characteristics.
`
`More particularly,
`
`the stator assembly is formed
`
`from a stack of stator laminations having inwardly
`
`projecting poles that define the walls of an unfinished
`
`internal chamber for housing a rotor assembly. Through-
`
`bolts attach front and rear aluminum end caps to the
`
`lamination stack, and this entire stator assembly is
`
`potted to unitize the lamination stack and fill voids
`
`between the stator poles with potting compound.
`
`The
`
`internal chamber is then finished by machining a
`
`continuous, cylindrical bore substantially coincident
`
`with the sidewalls defined by the inwardly projecting
`
`stator poles. Precision registration of the rotor
`
`assembly is achieved by aligning end bearings on the
`
`rotor shaft with internal receiving surfaces machined in
`
`the stator end caps; the receiving surfaces being part
`
`of the cylindrical bore.
`
`While the motor and fabrication method described in
`
`the '604 and '572 references achieve substantial
`
`Peflfionas'Exmbfl1003,pg.3
`
`Petitioners' Exhibit 1003, pg. 3
`
`

`

`WO 96/31936
`
`PCTfU596104723
`
`advances over the prior art, further improvements are
`
`still desired.
`
`In this regard, various features of the
`
`assembly and method described in the '604 and '572
`
`references were identified for improvement.
`
`One area sought to be improved relates to the
`
`potting of the stator assembly. Specifically, it has
`
`been determined empirically that a double cure cycle is
`
`desired for the potting compound;
`
`the second cure cycle
`
`improves the rigidity of the stator assembly,
`
`thereby
`
`yielding more efficient operation over the life of the
`
`motor. When only a single cure cycle is employed it has
`
`been found that, after a period of use,
`
`the rotor
`
`assembly occasionally locks within the stator assembly,
`
`thereby limiting the useful life of the motor. Adding a
`
`second cure cycle, however, undesirably increases
`
`
`
`manufacturing costs.
`
`A related aspect sought to be improved is the
`
`removal of air pockets formed within the potting
`
`compound. As discussed in the '572 and '604 references,
`
`air is a poor thermal conductor. Filling the otherwise
`
`open space between the stator poles with potting
`compound,
`improves thermal conductivity and,
`
`accordingly,
`
`improves dissipation of the heat developed
`
`within the motor.
`
`The process used in potting the
`
`stator assembly, however,
`
`is known to leave an air
`
`pocket under the rear end cap. This impedes the flow of
`
`heat from the rear end cap. Therefore, further
`
`improvements in the thermal characteristics of the motor
`
`assembly are sought by eliminating the air pocket.
`
`Another area sought to be further improved relates
`
`to providing external electrical connections to the
`
`stator windings within the motor assembly. As described
`
`in the '572 and '604 references, an insulator having
`
`connectors is seated against the rear end of the stator
`
`lamination stack.
`
`The terminating ends of the stator
`
`windings are brought out to the connectors, and a
`
`printed circuit board is configured to plug into
`
`Peflfionas'Exmbfl1003,pg.4
`
`Petitioners' Exhibit 1003, pg. 4
`
`

`

`WO 96/31936
`
`PCTfU596/04723
`
`3
`
`connectors, establishing electrical continuity between
`the stator windings and conductive traces on the printed
`circuit.
`
`
`
`is provided in conjunction with'the
`printed circuit,
`printed circuit board to accommodate remote access to
`the stator windings by way of a complementary external
`connector.
`In this way, external signals are readily
`connected to the stator windings for controlling the
`motor operation.
`
`This second connector is nested within the rear
`stator end cap. As previously described, both end-caps
`are attached to the lamination stack by means of several
`through bolts, before the potting compound is applied.
`To prevent any potting compound from leaking between the-
`rear end cap and the second connector, a sealing means
`is provided around the second connector. Although the
`aforementioned structure provides an effective means for
`connecting external motor drive signals to the stator
`windings, a simpler and therefore more cost-effective
`solution is desired.
`
`improvements are sought which will more
`In short,
`efficiently address the aspects described above, while
`maintaining the benefits and advantages in the motor
`assembly and method as described in the '572 and '604
`references.
`
`Su
`
`a
`
`o
`
`t e
`
`v
`
`In view of the foregoing, it is a primary aim of
`the present invention to simplify and,
`thereby, achieve
`a lower cost motor assembly and fabrication method,
`than
`that presently known.
`
`thermal characteristics.
`
`In more detail, it is an object of the present
`invention to eliminate the small air gap between the
`potted windings and the metal of the aluminum end cap.
`
`Peflfionas'Exmbfl1003,pg.5
`
`Petitioners' Exhibit 1003, pg. 5
`
`

`

`WO 96/31936
`
`PCTIU896/04723
`
`4
`
`
`
`In even greater detail, an object of the present
`invention is to provide high dielectric paths of good
`thermal conductivity between the electrical conductor
`
`in
`and pole structure and the exterior of the motor,
`order to increase the capacity of the motor to dissipate
`heat.
`
`Another object of the present invention is to
`
`provide an electrical motor fabrication method that
`
`simplifies the method previously known and used by
`eliminating the cost and time demanded by a second
`potting compound cure cycle, while maintaining the
`structural integrity of the final motor assembly.
`Still another object of the present invention is to
`
`provide an electrical motor assembly having a simplified
`and thus improved electrical connection between the
`
`internal stator windings and an external connector.
`
`Additional objects, advantages and other novel
`
`features of the invention will be set forth in part in
`the description that follows and in part will become
`
`apparent to those skilled in the art upon examination of
`the following or may be learned with the practice of the
`invention.
`The objects and advantages of the invention
`
`may be realized and obtained by means of the
`
`instrumentalities and combinations particularly pointed
`out in the appended claims.
`
`To achieve the foregoing and other objects, one
`
`aspect of the present invention is directed to a method
`
`of producing an electrical motor, wherein an
`
`intermediate or unfinished stator assembly is formed by
`
`compiling a stack of stator laminations and stator
`
`windings.
`
`The intermediate stator assembly is then
`
`placed into a mold, and molten plastic is injected under
`
`pressure into the mold, whereby the molten plastic is
`
`forced into and fills interior voids between poles of
`
`the intermediate stator assembly.
`
`The molten plastic
`
`also forms a rear end cap for the stator assembly.
`
`The
`
`plastic used in this invention may be any
`
`Peflfionas'Exmbfl1003,pg.6
`
`Petitioners' Exhibit 1003, pg. 6
`
`

`

`
`
`WO 96131936
`
`PCTIU596/04723
`
`5
`
`thermoplastically processible resin, or blends of such
`resins.
`The resin may optionally include additives such
`as flame retardants, reinforcements, colored pigments,
`fillers, plasticizers, heat or light stabilizers; Next,
`
`molded stator assembly to produce a concentric bore for
`housing a rotor assembly;
`the bore also providing
`mounting surfaces for receiving rotor assembl
`Finally,
`the rotor assembly is mounted into the stator
`assembly by inserting the rotor assembly into the
`continuous bore and engaging the rotor bearings with the
`mounting surfaces.
`
`
`
`A
`
`A related aspect of the present invention is
`directed to the injection molded electrical motor
`assembly, which includes a rotor assembly having a
`central rotor portion on a rotor shaft, and a rotor
`bearing disposed near each end of the rotor shaft.
`unitary stator assembly includes a stator lamination
`stack which forms stator poles that carry stator
`windings, and front and rear end caps.
`The stator poles
`and windings are substantially encapsulated by an
`injection molded plastic mass, which fills the space
`between the stator poles.
`The molded plastic also
`integrally forms the rear end cap.
`A continuous bore
`formed in the stator assembly through the front end cap,
`the stator lamination stack, and the rear end cap,
`forms
`mounting surfaces in the end caps for receiving the
`rotor bearings;
`the rotor assembly being carried within
`the bore by an engagement between the rotor bearings and
`the mounting surfaces in the end caps.
`Having summarized the present invention above,
`discussion will now be directed to a preferred
`embodiment of the invention. As an intermediate step of
`the fabrication process of a preferred embodiment, a
`matrix of conductive pins is fusion welded to the stator
`windings.
`The rear end cap is formed by the injection
`molded molten plastic to surround the matrix of pins and
`
`the
`
`Peflfionas'Exmbfl1003,pg.7
`
`Petitioners' Exhibit 1003, pg. 7
`
`

`

`WO 96/31936
`
`PCTfU896/04723
`
`6
`
`
`
`In
`form a connector housing about the conductive pins.
`this way,
`the motor assembly provides a connector that
`is readily adapted for electrical connection to an
`
`external or remote source for controlling the motor.
`The injection molded end cap is an extension of the
`injection molded mass in the stator, and thus provides
`an efficient continuous path for dissipation of heat
`generated in the windings.
`
`fiziefi Description of the Drawings
`
`The accompanying drawings incorporated in and
`
`forming a part of the specification,
`
`illustrate several
`
`aspects of the present invention, and together with the
`description serve to explain the principles of the
`invention.
`In the drawings:
`
`Figure 1 is a perspective view illustrating a
`completely assembled motor constructed in accordance
`
`with one embodiment of the present invention;
`
`2 is a partially exploded view showing a motor
`FIG.
`according to the invention with the rotor assembly
`removed from the stator assembly;
`
`3 is a process flow chart illustrating the
`FIG.
`steps of constructing a motor in accordance with the
`
`preferred embodiment of the present
`
`invention;
`
`FIG.
`4 is an elevational view illustrating a
`partially assembled rotor,
`including a partial cut-away
`view;
`
`FIG. 5 is an elevational view illustrating a rotor
`
`assembly with bearings and bushing in place and ready
`for insertion into a stator assembly;
`
`FIG.
`
`6 is an elevational view of an individual
`
`stator lamination,
`
`illustrating the inwardly directed
`
`stator poles and pole teeth;
`
`FIG. 7 is a perspective view showing an assembled
`
`stator lamination stack made up of individual
`
`laminations as illustrated in FIG. 6;
`
`,
`LEAD ORIGINAL J
`
`Peflfionas'Exmbfl1003,pg.8
`
`Petitioners' Exhibit 1003, pg. 8
`
`

`

`WO 96/31936
`
`PCTIU596/04723
`
`7
`
`FIG. 8 is a perspective view of the front end of
`the stator lamination stack of FIG.
`
`7 with insulators
`
`and stator windings in place;
`FIG. 9 is the cut-away view as illustrated by
`arrows in FIG. 6, illustrating a wound stator assembly
`within the caps and connector in place;
`. 10 is a perspective view of the rear end of
`the unfinished stator assembly, showing the insulators,
`stator windings, and matrix
`
`
`
`of connector pins as disposed in relation to the stator
`lamination stack;
`
`FIG. 12 is a partial view illustrating the
`partially completed stator assembly of FIG. 9 after
`injection molding;
`
`FIG. 13 is a view similar to FIG. 12 illustrating
`the injection molded assembly after it has been machined
`and is thus ready for insertion of the rotor assembly;
`FIG .
`
`present invention;
`‘FIG. 15 is a perspective View with a partial cut-
`away of the mold fixture shown in FIG. 14;
`FIG. 16 is a partly broken away side view, and
`FIG. 17 is an axial section taken along the line 17-17
`of FIG. 16, respectively, showing an alternative
`construction of motor adapted for practice of the
`present invention;
`
`FIG. 18 is an elevational view of a rotor assembly
`for the motor of FIGS. 16 and 17; and
`
`FIGS. 19 and 20 are an elevational cross section
`and an axial cross section taken along the line 20-20 at
`FIG. 19, respectively, showing a permanent magnet motor
`adapted for practice of the present invention.
`Reference will now be made in detail to various
`presently preferred embodiments of the invention,
`
`I
`
`1
`
`BAD ORIGENAL Q]
`
`Peflfionas'Exmbfl1003,pg.9
`
`Petitioners' Exhibit 1003, pg. 9
`
`

`

`WO 96/31936
`
`PCTfU896104723
`
`8
`
`examples of which are illustrated in the accompanying
`
`drawings.
`
`
`
`Detailed nesgziption 0: ins Ereferred Embodiments
`
`Turning now to the drawings, FIG.
`
`1 shows a
`
`perspective view of a hybrid permanent magnet stepping
`
`motor, and FIG.
`
`2 a partly exploded View showing the
`
`rotor and rotor retaining elements removed from the
`
`stator assembly.
`
`It will be noted at the outset,
`
`however, that while the invention will be described in
`
`connection with a hybrid stepping motor, it is also
`
`applicable to other motor types.
`
`For example,
`
`the
`
`invention is applicable to brushless variable reluctance
`
`stepping motors, permanent magnet brushless motor
`
`designs, switched reluctance motors, enhanced variable
`
`reluctance motors, as well as enhanced and unenhanced
`
`stepping motors of the hybrid stepping type. Finally,
`
`induction motors could also utilize the present
`
`invention as could other motor types as will be apparent
`
`to those skilled in the art upon reading the following
`
`detailed description.
`
`Referring to FIGS.
`
`1 and 2,
`
`there is shown a hybrid
`
`stepping motor generally designated by reference numeral
`
`20 comprised of a stator assembly 21 and a rotor
`
`assembly 22.
`
`The rotor assembly is fitted with bearings
`
`23, 24 which in turn mount in end caps 25, 26 that
`support the rotor assembly 22 for rotation in the stator
`
`The end caps 25, 26, sandwich a central
`assembly 21.
`stator lamination stack 27 that forms stator poles which
`
`carry stator windings (not shown in FIGS. 1 and 2).
`
`In
`
`the presently preferred embodiment,
`
`the stator
`
`laminations are aligned in registry and initially
`
`secured by weld joints 70 (See FIG. 7) along the corners
`
`of the lamination stack. As will be described in
`
`greater detail below,
`
`the lamination stack is further
`
`secured by means of a high-strength injection molded
`
`plastic which completely encapsulates the interior of
`
`the lamination stack and preferably projects partly into
`
`Pefiflonas'Exmbfi1003,pg.1O
`
`Petitioners' Exhibit 1003, pg. 10
`
`

`

`
`
`WO 96/31936
`
`PCTfUS96/04723
`
`9
`
`a central bore 30 after molding.
`
`The bore 30 is then
`
`machined as by honing to form bearing surfaces 31, 32
`
`(See FIG. 9)
`
`in the end caps 25, 26 and also to form a
`
`
`
`smooth bore 30 through the lamination stack 27,
`contiguous with the bearing surfaces 31, 32.
`
`In the illustrated embodiment of FIG. 2, retaining
`rings 36 secure the rotor assembly 22 in the stator
`
`the rotor assembly
`In another embodiment,
`assembly 21.
`22 is retained in the stator assembly by a press-fit
`
`engagement between bearings 23, 24 and receiving
`surfaces 31, 32.
`The front end cap 26 has a flange 37
`which in turn has a machined surface 38 with a mounting
`boss 39 to locate the motor in a mounting bracket.
`Mounting holes 40 provide means for mounting the motor
`to its bracket (not shown).
`The rear end cap 25
`includes an integral electrical connector 41 for
`
`supplying power to the stator windings.
`
`As shown in FIG. 2,
`
`the rotor assembly 22 includes
`
`a rotor shaft 50 which supports a rotor section 51,
`(i.e., the portion of the rotor which is magnetically
`active) and outboard bearings 23, 24.
`In the
`
`illustrated embodiment,
`the rotor comprises toothed
`lamination sections 52, 53 separated by a permanent
`
`magnet 54.
`The magnet is positioned to provide the
`lamination sections 52, 53 with opposite magnetic
`polarities making, for example,
`lamination section 52 a
`
`In
`north pole and lamination section 53 a south pole.
`one embodiment,
`the laminations are formed with external
`
`teeth, of the same pitch as the teeth associated with
`
`the stator poles of the stator assembly. Other ratios
`
`of stator/rotor pitch can also be used such as 52/50 or
`
`48/50. As is known in the art,
`
`the teeth of section 53
`
`are offset by about one half pitch with respect to the
`
`teeth of the section 52 in order to form a hybrid
`
`permanent magnet rotor. Thus, when the stator windings
`
`are energized by a drive current coupled through the
`pins of connector 41,
`the rotating magnetic field which
`
`Pefiflonas'Exmbfi1003,pg.11
`
`Petitioners' Exhibit 1003, pg. 11
`
`

`

`WO 96/31936
`
`PCT/US96/04723
`
`10
`
`is produced in the stator tends to successively align
`
`the teeth of rotor lamination sections 52, 53, with the
`
`field of the stator teeth,
`
`causing the motor to step in
`
`sequence. Control of the rotational rate and direction
`
`of the stator field thus allows control of the rate and
`
`direction of rotor rotation.
`
`
`
`Turning now to FIG. 3,
`
`there is illustrated the
`
`process for fabricating a motor in accordance with the
`
`present invention. Concentrating first on the rotor
`
`assembly, it is seen that the primary raw materials
`
`which go to make up the rotor are brought together at
`
`process step 100, and include rotor shafts, rotor
`
`laminations (or prestacks) and magnets. Those items are
`
`assembled at a step 101 and the assembled rotor which
`
`results is best illustrated in FIG. 4. There is shown a
`
`rotor shaft 50 having a pair of lamination stacks 52, 53
`
`disposed thereon, with a permanent magnet 54 interposed
`
`between the lamination stacks forming a rotor section 51
`
`intended to be driven by the rotating magnetic field
`
`produced by the stator.
`
`In a hybrid permanent magnet
`
`stepping motor,
`
`the rotor laminations 52 and 53 have
`
`alternate teeth and valleys of a given pitch related to
`
`(as described above)
`
`the pitch of the teeth on the
`
`stator poles. Moreover,
`
`the teeth in the sections 52
`
`and 53 are offset with respect to each other by one-half
`
`pitch.
`
`The magnet 54 serves to magnetically polarize
`
`the stacks 52, 53 with, for example,
`
`the stack 52 being
`
`a north pole and the stack 53 being a south pole.
`
`The shaft 50 has a pair of machined sections 60, 61
`
`adapted to receive the inner race of bearings 23, 24
`
`(FIG. 5) for support of the rotor within the stator
`
`assembly.
`
`The shaft 50 can have its output end keyed as
`
`illustrated, unkeyed if desired, or with any other
`
`adaptor configuration.
`
`The motor can also be configured
`
`with an output shaft on the rear end to form a double-
`
`ended motor.
`
`Such constructional details form no part
`
`Pefiflonas'ExmbH1003,pg.12
`
`Petitioners' Exhibit 1003, pg. 12
`
`

`

`
`
`WO 96/31936
`
`PCT/US96/04723
`
`11
`
`of the present invention and will not be emphasized
`herein.
`
`Having assembled the rotor 22 in step 101 (FIG. 3),
`the rotor is then passed to a grinding station where
`
`step 102 is performed to grind the rotor outer diameter.
`
`Such grinding tends to produce teeth in the lamination
`
`stacks 52, 53 which have relatively sharp corners.
`
`In
`
`addition,
`
`the grinding step produces a rotor which is
`
`substantially concentric and therefore can operate in a
`
`carefully machined stator bore with a relatively small
`air gap.
`
`Having thus configured the rotor magnetic section
`
`51, and after machining debris is cleaned from the
`
`rotor, a step 103 is then performed in which bearings
`
`22, 23 are assembled onto the bearing support surfaces
`
`
`
`60, 61 of the rotor.
`
`In the exemplary embodiment,
`
`spacer bushings 62, 63 are interposed between the
`
`bearings 23, 24 and the lamination stacks 52, 53
`
`respectively.
`
`The bushings ride between the lamination
`
`stack and the inner race of the bearings to form a
`
`spacer element to properly locate the hearings on the
`
`shaft.
`
`The bearings are press fit on the shaft,
`
`preferably in an appropriate fixture,
`
`in the step 103.
`
`Referring to FIG. 5,
`
`there is shown the rotor
`
`assembly including bearings 23, 24 and the spacing
`bushings 62, 63, providing a rotor assembly which is
`
`ready for insertion into a stator assembly.
`
`FIG. 5
`
`illustrates,
`
`in somewhat exaggerated fashion,
`
`the fact
`
`that the outer diameter of the bearings 23, 24 is
`
`slightly greater than the outer diameter of the rotor
`
`section 51.
`
`It was previously noted that the stator
`
`bore is a continuous straight through bore formed in a
`
`single operation after assembly of the stator. Thus,
`
`providing the bearings 23, 24 with a slightly greater
`
`outer diameter than the rotor section 51 allows the
`
`entire rotor assembly to be inserted into the bore, with
`
`the outer race of the bearing 23, 24 seating in the
`
`Pefiflonas'Exmbfi1003,pg.13
`
`Petitioners' Exhibit 1003, pg. 13
`
`

`

`WO 96131936
`
`PCTIU896/04723
`
`12
`
`bearing surfaces of the end caps while the rotor section
`
`51 has a sufficient, although a very small, clearance
`
`for rotation.
`
`The precision thereby achieved allows the
`
`motor to be configured with a relatively small air gap,
`thus providing higher torque and efficient operation.
`
`As illustrated in FIG. 3,
`
`the initial raw material
`
`component for the stator assembly procedure is
`
`individual stator laminations which are assembled in a
`
`step 105.
`
`An individual lamination 27a is illustrated
`
`in FIG. 6.
`
`it is seen that each lamination, which can
`
`be formed by stamping, has a series of poles 66a with a
`
`plurality of teeth 67a formed on each of the poles.
`
`The
`
`poles 66a are separated by gaps 68a which provide an
`
`area for receiving the stator windings.
`
`The laminations
`
`also have punched clearance holes 69a through which
`
`alignment bolts can pass for initially registering the
`
`stator assembly. Preferably a clearance hole 69a is
`
`associated with each pole 66a such that the stator
`
`laminations are symmetrical and can be installed in any
`of eight orientations. Thus, it is possible in assembly
`
`to turn the stator laminations with respect to each
`other such that the grain of the steel from which the
`
`laminations are made is not in a single direction,
`
`allowing the magnetic properties of the lamination stack
`
`due to grain to be averaged.
`
`
`
`As illustrated in FIG. 7,
`
`the step 105 (FIG. 3)
`
`is
`
`implemented by assembling a stack of laminations of a
`
`predetermined height and affixing the laminations
`
`together,
`
`in the illustrated embodiment by means of
`
`welds 70. Alternatively, prestacks (i.e., groups of
`
`laminations joined by stamped dimples formed during the
`
`laminations stamping operation) may be used. Using the
`
`welding technique, preferably a stack of laminations is
`
`placed under pressure, and automatic machinery gauges
`
`that the laminations stack is of the appropriate height
`
`before the welds are made.
`
`If it is not laminations are
`
`either added or removed until the desired height is
`
`Pefiflonas'Exmbfi1003,pg.14
`
`Petitioners' Exhibit 1003, pg. 14
`
`

`

`
`
`WO 96/31936
`
`PCTfU396/04723
`
`13
`
`
`
`obtained at which point automatic welding equipment
`
`preferably applies four welds 70 at corners of the
`
`lamination stack displaced 90 degrees from each other.
`
`As seen in FIG. 7,
`
`the assembled lamination stack
`
`thereupon provides a pole structure 66 separated by
`inter-pole winding gaps 68, each pole structure having
`axially disposed teeth 67 of a predetermined pitch.
`It
`is also seen that the anchor holes 69 are aligned such
`that an alignment bolt or injection molding needle can
`
`pass through the lamination stack at the appropriate
`point in the assembly process.
`
`After the lamination stack is assembled, and in the
`optional case where an "enhanced" motor is to be
`
`in a step 105 elongate magnetic strips 85 are
`produced,
`inserted in each gap between stator teeth 67 (See FIG.
`12). As will be described below,
`the magnets which are
`inserted between stator teeth tend to enhance the
`
`magnetic properties of certain classes of motor.
`
`The
`
`magnetic strips have sufficient frictional engagement
`with and magnetic attraction for the gaps into which
`
`they are inserted to temporarily maintain the strips in
`place during subsequent manufacturing steps until they
`are firmly secured in their gaps by means of injection
`molded plastic material.
`
`Following the magnet insertion step 105 if
`
`performed, or the simple welding of the lamination stack
`
`105 for a non—enhanced motor, as shown in FIG.
`
`3
`
`subsequent operations are performed on the assembled
`
`lamination stack to associate the stator electrical
`
`components with the stack and to magnetize the stator
`
`poles.
`
`In this regard,
`
`the stack is insulated, wound,
`
`and the windings are terminated.
`
`In FIG.
`
`3 the
`
`insulation step is indicated at 106. Preferably,
`discrete insulators are supplied along with the welded
`
`stator lamination stack in order to provide appropriate
`insulation between the stator windings and the
`
`lamination stack. Turning briefly to FIG. 8, one end of
`
`Pefiflonas'Exmbfi1003,pg.15
`
`Petitioners' Exhibit 1003, pg. 15
`
`

`

`WO 96131936
`
`PCT[U596/04723
`
`14
`
`
`
`the insulator assembly is illustrated at 71 and is shown
`
`to completely line the slot 68 as well as to cover the
`
`face 72 of each pole 66. Upstanding insulator sections
`
`71' help retain the stator windings, and will interface
`
`with the end cap when they are juxtaposed. Bolt
`
`protectors 71" insulate the fasteners 28 and prevent
`
`contact between the fasteners and the windings.
`
`A
`
`mating end for the insulator is illustrated in FIG. 10
`
`at 90.
`
`It is seen that the insulator 90 is similar to
`
`the insulator 71 in that it provides a face 92 for
`
`insulating the end of the pole, channels 93 which
`
`completely line the inter-pole slots, and upstanding
`
`projections 90' for retaining the stator windings.
`
`FIG.
`
`10 illustrates bolt protectors 90" on the rear facing
`
`insulator section.
`
`Since the rear end cap 25 is formed
`
`from molded plastic and bolts are not used to secure it
`
`to the lamination stack 27, it should be appreciated
`
`that the bolt protectors 90" are not necessary.
`
`However,
`
`in a preferred embodiment they are maintained
`
`so that insulator sections 71 and 90 are interchangeable
`
`and only one type needs to be stocked. Moreover,
`
`the
`
`bolt protectors 90" provide an irregular face that
`
`enhances the bond formed between the molded rear end cap
`
`25 and the lamination stack 27.
`
`Having thus insulated the pole structure, windings
`
`schematically illustrated at 73 are applied (FIG. 12),
`
`preferably automatically,
`
`to each of the poles in a step
`
`107 (FIG. 3).
`
`The windings serve as means for
`
`magnetizing the poles on which they are wound.
`
`It will
`
`be appreciated that in the typical case, a winding of
`
`significant dimension (more significant than illustrated
`
`in the FIGS.) will build up in order to get the
`
`necessary turns on each pole.
`
`It is seen, however, that
`
`the turns are insulated from the magnetic structure by
`
`means of the insulator sections 71, 90. Having wound
`
`the coils in step 107,
`
`the coil ends are then terminated
`
`in step 108.
`
`In this step, conductive pins 94 are
`
`Pefiflonas'Exmbfi1003,pg.16
`
`Petitioners' Exhibit 1003, pg. 16
`
`

`

`WO 96/31936
`
`PCTIUS96I04723
`
`15
`
`aligned in a row or matrix by spacer 95 -- the pins
`
`having a projecting end 94' and a terminating end 94"
`
`(See FIG. 11).
`
`
`
`In the illustrated motor which has eight pole
`
`structures each with a winding, eight pins 94 are
`
`provided for terminating the coil ends. Thus, at the
`
`start of the windings, a first end of a coil is fusion
`
`welded to the terminating end 94" of a pin 94, wound
`
`around four poles,
`end of another pin.
`
`then fusion welded to the terminating
`It should be appreciated that a
`
`larger matrix of conductive pins 94 may be desired if,
`for example,
`the coils are bifilar wound, if a separate
`coil is desired for each pole, or alternatively, if a
`larger number of stator poles are provided.
`
`Having thus configured the stator electrical
`
`components including the magnetic stator lamination
`
`stack and the associated electrical components, a step
`110 (FIG. 3)
`is performed to assemble the stator.
`In
`
`the preferred embodiment, this step is performed by
`aligning and securing a front end cap 26 with the
`
`lamination stack. Preferably, four self tapping screws
`
`28 secure the end cap 26 to the lamination stack 27,
`
`in
`
`a fashion sufficient to maintain alignment during motor
`fabrication, and subsequently during motor operation.
`
`As will be described in more detail in connection with
`
`FIGS. 14 and 15,
`
`the mold fixture is adapted to maintain
`
`precise registration between the front end cap 26 and
`
`the front end cap
`the lamination stack 21. Preferably,
`26 is cast aluminum, and has pilot holes 80 that align
`with anchor holes 69 of the lamination stack.
`
`Since,
`
`in practicing the invention,
`
`the motor is to
`
`be pressure filled with a molten plastic,
`
`the practice
`
`of the invention further contemplates the sealing of the
`
`stator elements to prevent leakage of the molten plastic
`
`during the injection step. This sealing is accomplished
`in the present invention during the injection molding
`
`process.
`
`For example, as will be described below, a
`
`P