US3355310A - Method of forming layers of insulating material in slots of magnetic cores - Google Patents

Description

V- 28, 1 M v. DE JEAN ETAL 3,355,31fl

METHOD OF FORMING LAYERS OF INSULATING MATERIAL] IN SLOTS OF MAGNETIC CORES Filed July 15. 1965 6 Sheets-Sheet 1 Nov. 28, 1967 M. v. DE JEAN ETAL 3,355,310

METHOD 0!" FORMING LAYERS OF [NSULATLNG MATERIAL IN SLOTS OF MAGNETIC 001mg Filed July 15, 1963 6 Sheets-Sheet 2 Nov. 28, 1967 M. v. DE JEAN ETAL 3,355,310

METHOD OF FORMING LAYERS OF INSULATING MATERIAL IN SLOTS 0F MAGNETIC CORES Filed July 15, 1963 6 Sheets-Sheet :5

Nov. 28. 1967 3 M. v. DE JEAN ETAL 3,;65316 METHOD OF FORMING LAYERS OF INSULATING MATERIAL IN SLOTS OF MAGNETIC CORES Filed July 15, 1965 6 Sheets-Sheet 5 Nov. 28, 1967 M. v. DE JEAN ETAL. 3,355,31

METHOD OF FORMING LAYERS OF INSULATING MATERIAL IN SLOTS OF MAGNETIC CORES 6 Sheets-Sheet 6 Filed July 15, 1965 Rial/147M VAL VF T smer SWITCH 02 TIME? 1 l/ Pan/on United States Patent M 3,355,310 METHOD OF FORMING LAYERS OF INSULATING MATERIAL IN SLOTS 0F MAGNETIC CORES Milton V. dc Jean and Dean E. Shaffer, Fort Wayne, Ind.,

assignors to General Electric Company, a corporation of New York Filed July 15, 1963, Ser. No. 295,073 6 Claims. (Cl. 117-18) This invention relates in general to method for applying coatings on articles of manufacture and more specifically to an improved method particularly adapted for use in connection with the application of coatings of insulating material onto the desired locations of magnetic cores of electrical devices, such as stator and armature cores for dynamoelectric machines.

Electrical inductive devices, such as dynamoelectric machines, customarily include one or more core members formed on magnetic material which are provided with a series of slots for accommodating excitation windings. These windings are ordinarily composed of a number of turns of magnet wire conductors having a thin covering of insulation. Since the cores conventionally include a stack of thin laminations which have been stamped out of magnetic sheet material, the edges of the laminations, especially at the entrances of the slots on each side face of the core, contain burrs and other sharp projections produced by the stamping operation. The projections, unless properly covered with insulation material, tend to cause breaks in the wire insulation ultimately resulting in possible short circuit of the Wire conductors.

For this and other reasons, it is necessary to provide an imperforate ground insulation between the core and the winding, both in the slots and at the slot edges, which is sufliciently thin in cross section to permit optimum utilization of slot area for the windings, yet will not break down at the maximum temperatures encountered during machine operation.

In the past there have been numerous proposals for providing insulating material between the windings and the walls of winding slots and slot entrances as well as end faces of cores. One of the most desirable approaches concerns the formation of an adherent, protective, integral insulating layer from fusable powder coating material, such as thermosetting epoxy resin, on these preselected core surfaces after the core has been pre-heated to a particular temperature. The heat energy emitted from the walls coalesces the applied powder material into the integral layer. Normally such material melts, flows slightly, and coalesces onto the core walls with the proper adhesion in the temperature range of 190 C. to 232 C. Examples of this type of resin are Scotchcast Brand Resins, Nos. 260 and XR 5070, commercially available from Minnesota Mining and Manufacturing Company, St. Paul, Minn.

A practical difficulty, however, has been encountered in applying the coating material onto the core walls While the core. is pre-heated in the proper range. For instance, depending upon the core mass, at the outer exposed surfaces of the core which are to receive the powder material, the core has a tendency to cool rapidly below the critical temperature range; e.g., in some cases,

within one-half minute. Thus, there has been a problem in furnishing low cost equipment, suitable for the mass production manufacture of cores, which is not only capable of forming the layer of insulating material on the walls with the requisite adhesive and uniformity of thickness qualities, but is also efficient and rapid in operation.

Consequently, it is a general object of the present invention to provide an improved method for applying coatings onto articles of manufacture and a more specific object to provide a. machine suitable for use in connec- 3,355,319 Patented Nov. 28, 1967 tion with the formation of improved coatings or layers of insulating material on the desired surfaces of cores for electrical devices, such as stator and armature cores employed in dynarnoelectric machines.

It is a further object of the invention to provide an improved method which overcomes the difliculties and problems mentioned .above.

It is another object of the present invention to provide an improved method of forming layers of insulating material in slots of pre-heated magnetic cores to a particular temperature which efficiently and rapidly forms the insulation layers having the desired characteristics on a mass production basis without unduly reducing the temperature of the cores or causing powder build up between the core and its support.

In carrying out the objects of this invention in one form thereof, we provide a method especially adapted for applying a coating onto pre-selected surfaces of an article, such as a magnetic core of an electrical inductive device.

Initially, the core, preheated to a preselected temperature, is mounted at a core loading station onto a holder in a retracted position in which the core and holder are movable relative to one another at a core. The holder is then moved into frictional engagement with the periphery of the core and the core and holder are subsequently angularly driven into a powder spray coating station. Insulating material in powder form is applied onto the slot surfaces of the core from powder applicators disposed at least at one location adjacent each side of the core while the holder, and consequently the core, are turned at a speed sufficiently low to permit the disposition of powder on the 'slot surfaces throughout the axial lengths of the slots as well as onto the slot edges. During the application of the powder, the holder prevents the formation of a coating on the part of the core frictionally engaged by the holder.

In order to insure powder collision in the vicinity of the axial center of the slots with-out reducing the preheated condition of the core, the powder is applied from the powder applicators at a pressure not substantially in excess of 6 psi; as the holder is turned at ,a speed not substantially above 30 r.p.m. In addition, during the application of powder from the powder applicators, powder which may have passed entirely through the slots is predirected by bafiie means back into the slots for deposit thereof onto the slot edges .and surfaces desired to be covered.

The core and holder are then angularly driven away from the coating station to a core unloading station, the holder being returned to its redirected position and the coated core being removed from the holder within twelve seconds from the time that powder was deposited on the slot surfaces. In this Way, the tendency of a hardened insulation bridge to form at the periphery of the core adjacent the holder is reduced or prevented and the core may readily be dismantled from the holder.

The holder is then prepared for mounting of another core thereon in the case of stator cores by clean excess powder from the periphery of the holder and thereafter applying a film of friction-reducing material on the holder periphery.

In this way, a process is provided which is efficient and winding slot and slot edges of a magnetic core when the aforementioned machine is employed in the fabrication of magnetic cores.

The subject matter which we regard as our invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. Our 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 front view of an article coating machine having a number of angularly spaced apart Work stations, the machine incorporating the preferred embodiment of the present invention;

FIG. 2 is an enlarged side view, partially broken away to show details, of a portion of the machine seen in FIG. 1;

FIG. 3 is an enlarged rear view of the machine of FIG. 1;

FIG. 4 is an enlarged view in section of the preferred manner in which each article to be coated, a stator magnetic core in the exemplification, is supported in the machine of FIG. 1 for independent rotation when disposed in certain work stations;

FIG. 5 is an enlarged view of the rotating manifold and valve assembly seen in FIG. 2 for operating the article holder at pre-selected angular positions of travel;

FIG. 6 is a section taken alonglines 55 in FIG. 5

FIG. 7 is a view in perspective of the coating applying station preparatory to actuation of the coating applying devices;

FIG. 8 is a view similar to FIG. 7, showing a coating being formed on pre-selected surfaces of the core;

FIG. 9 is a fragmentary view showing a part of the reconditioning operation being performed on the holder in the reconditioning station;

FIG. 10 is a view similar to FIG. 9 showing a second reconditioning operation on the holder being completed.

FIG. 11 is a schematic representation withself explanatory legends identifying the electrical and fluid pressure controlling mechanisms and systems of the machine; and

FIG. 12 is a view in cross section of the coupled device of FIG. 4 mounting a work holder assembly for use in coating a dynamoelectric machine armature core.

Now, with more specific reference to the drawings, the preferred form of an automatic coating applying machine is shown generally in FIGS. 1-3 and includes ametal frame 21 having a vertical orupright support wall 22 and a number ofcovers 23. The machine, especially adapted for use in the formation of an adherent, integral insulation coating on desired locations in cores for electrical inductive devices, is provided with a plurality of angularly spaced apart work stations or stages. In the illustrated embodiment, these stations are four in number, designated by letters A-D inclusive, respectively denoting a loading station, a coating applying or spraying station, an unloading station, and an article holder reconditioning station. These stations, which are located 90 degrees apart, will be described in detail hereinafter. A turntable, disposed somewhat centrally ofwall 22 and rotatably supported thereby, is formed of acast member 25 having a plurality ofradial arms 26 corresponding in number and angular spacing to the stations. Each arm terminates at its outer end in acylindrical section 27 carrying an arrangement, generally indicated at 35, to detachably mount anarticle holder assembly 40 for independent rotation relative tomember 25.

Any suitable means may be employed for imparting intermittent motion to rotatemember 25 for turning .theholder assembly 40 successively from one work station to another in a timed 90 step by step fashion. Any indexer unit, shown generally at 31 in FIG. 2, may be used centrally ofmembers 25, such as air actuated Erickson Model 600 available from Erickson Tool Company of Cleveland, Ohio. Unit has aframe 32 suitably secured to and supported bywall 22 which also functions to mountmember 25 for periodic movement relative to the work stations, as by cooperating air actuatedcylinders 33 andratchet driver 34 attached to member 25 (FIGS. 3 and 11).

It will be observed at this time from the drawings tha the article to be coated in the exemplification is a laminated stator core 1 of the salient pole type, formed from magnetic material, such as electrical grade iron. The core conventionally includes a centralannular bore 2 and a number of angularly spaced apart windingaccommodating slots 3 which evtend axially through the core and terminate at side faces 4 where winding pins 5 project away from the core. The walls ofslots 3 and side faces 4 are the regions or walls of the stator core on which an adherent coating of insulating material is formed in this exemplification when the core is in a pre-heated condition. Consequently, in the preferred form, eachholder assembly 40, when used with stator core 1, may be conveniently fabricated with an outer generally cylindrical or annularflexible member 41 adapted to cooperate withbore 2 of the core such that it not only supports and drives the core, but also masks thebore 2 where no coating is desired.Flexible member 41 is preferably formed of material, such as silicone rubber, which is impervious to the insulating powder and heat of the core, and is movable between retracted and extended positions at predetermined angular locations of members 25 (to be discussed later). When retracted, (solid lines in FIG. 4) the outer diameter ofmember 41 is slightly less than the bore diameter of the core to permit relative movement therebetween. In the extended position, shown by the broken lines in that figure,flexible member 41 is expanded sufficiently to provide a firm frictional engagement throughout the axial length ofbore 2.

Although any suitable means may be utilized to control the actuation of and urgeflexible member 41 between the retracted and extended positions, we have found in actual practice that the illustrated mechanisms and fluid pressure system are advantageous to employ in view of the additional functions which the fluid, such as air, can perform. For use with the air pressure system,article holder assembly 40 may be conveniently constructed in the manner shown in FIG. 4. The illustratedassembly 40 includes, by way of example, a central, elongatedtubular element 42 having asleeve 43 attached thereto formed withenlargements 44 at each end. The outer surface ofsleeve 43 and the interior ofmember 41 define anair receiving pocket 45.Flexible member 41 is attached in sealed relation to these enlargements by an inwardly projectingflange 46 formed integral at each end ofmember 41.Flange 46 is held tightly betweenwasher 47 and the associated enlargement in anannular groove 48 provided in the side of the enlargement. These parts are secured in place onelement 42 between ashoulder 49 and nut 51 threadedly received onstud 52. The stud is in turn fastened withintubular element 42. A number ofradial openings 55 connectair receiving pocket 45 withhollow center 54 for transferring fluid therebetween.

Still referring to FIG. 4, the illustrated arrangement 35 for detachably mountingassembly 40 for independent rotation relative to angularlymovable member 25 will now be described. Arrangement 35 comprises acoupler device 61 having ahollow shaft 62 and a sealedbearing unit 63, arranged insection 27 ofmember 25, rotatably supporting thecoupler shaft 62. With respect tocoupler device 61, a cup-shapedouter housing 65 includes anopening 66 on one Wall for mountinghollow shaft 62 which has apassageway 67 in communication with the interior ofinner chamber 68 of the housing. On the sides of the housing, remote fromshaft 62, aremovable plate 69 is connected thereto by bolts 70. Centrally of thisplate 69 is furnished an integral extension 72 having acentral bore 73, which carries asleeve insert 74, and a longitudinal aperture 75 running betweenchamber 68 and the end face of extension 72. On the outside surface thereof is formed threads 71 to engage complementing threads ofcollar 57 connected to the extreme end ofelement 42 ofholder assembly 40.Suitable seals 76 may be used to make the device air tight. Confined withinchamber 68 and in sealed relation with the chamber walls byannulus 77 is apiston type element 78, provided centrally thereof with ahole 79 and a needle type valve 80 outwardly thereof. A coil spring 81 is disposed betweenelement 78 and insert 74 to bias the element towardsshaft 62. The exact functions of the parts withinchamber 68 will be brought out hereinafter but it should be recognized now that they permit article holder assemblies for different articles to be attached to plate 69 and passage of air therethrough.

With regard to sealedbearing unit 63, the outer races of a pair ofball bearings 82 are seated in a cast cylindrical housing 83 having acavity 85, with the inner races being affixed to rotate withshaft 62 ofcoupler device 61. Resilient rings 86, 87 seal the bearing races with respect to the housing and shaft.Sleeve 91 retains the inner bearing races in their proper spaced apart relationship while aresilient annulus 92, disposed betweenhousing 85 andsleeve 91 adjacent the bearings, provides a seal at this location forcavity 85. Very smallair bleeder openings 93, formed in eachannulus 92 next to the balls of the bearings, direct a fine flow of air from thecavity 85 past the balls to the ambient atmosphere to keep the balls free of powder during the coating operation. These parts are held together in assembled relation by a screw and shoulder combination indicated at 94. It should be noted at this time thatcavity 85 is open topassageway 67 ofcoupler shaft 62 and hencechamber 45 of theholder assembly 40, by aligned holes 81 in the shaft andsleeve 91.

Theextreme end 95 ofshaft 62, remote fromcoupler device 61, is solid and protrudes beyondunit 63 to carry suitable means by which rotary motion is transmitted to theholder assembly 40, throughcoupler device 61, and to core 1 in the coating and reconditioning stations B and D. This means, best shown in FIGS. 2 and 3, is in the form of asheave 96 connected to shaft end 95, which is adapted to travel into frictional engagement withbelts 97, rotatably driven at stations B and D, whenmember 25 is turned into these stations. The belts are rotatably carried bypulleys 98 mounted tovertical wall 22 and are driven continuously byelectric motor 101 by way of standard belt-speed reduction means 102, all supported bywall 22.

Returning again to the description of the illustrated fluid pressure system, air under pressure is supplied at pre-selected times to each bearingcavity 85 of bearingunit 63 and then throughcoupler device 61 toholder pocket 45 from a main line pressure source shown at 110 in FIG. 11. A conventional valve 111 and pressure regulator 112 connect the pressure source byline 113 toa rotary manifold orvalve assembly 115, which serves to control the flow of air to and from each bearing cavity 85 (and hence the holder assembly), through fourtubes 116, 117, 118, and 119. Each of these tubes extends from bearingcavity 85 radially inward alongarms 26 ofrevolvable member 25, throughindexer driver 34 adjacent the axis of revolution thereof to a rotatable plate 121 ofassembly 115, now to be described in detail in connection with FIGS. 2, S, and 6.

On the side of plate 121 facingholder assemblies 40, ayoke section 123 surrounds the end of tubes 116-119 and is received inwall hole 122. This section joins the plate to ratchetdriver 34 of theindexer 31. A number ofidentical bores 124, formed in the plate, extend from the various tubes, which are connected therein, and terminate at runningface 125 inopenings 127. All openings are at the same radius with respect to the axis of rotation of the plate. Integral with face is a flange which, withface 125, furnishes a sealed running relation to underface 132 of astationary plate 131. Theplate 131 is in turn attached to wall 22 by means of aflanged bracket 134 andstuds 135. Plate faces 125 and 132 are maintained in the sealed, running relation by biasingspring 136 disposed betweenthrust collars 137 andpin 138, which passes entirely throughbracket 134 andplate 131 to enter rotatable plate 121 at its center to rotate therewith.

Formed onunderface 132, best shown in FIG. 6, are

four mutually isolated arc-like grooves 141, 142, 143, and 144, each having a common axis with the axis of rotation and the same radius as thebore openings 127 offace 125.Grooves 141 and 143 in the stationary plate located at the same angular positions as the loading and unloading stations A and C. The circumferential centers ofgrooves 142 and 144 correspond in position to the coating applying and reconditioning stations B and D, the grooves being connected to pressuresource 110 throughinlet ports 146. Each of the other grooves, that is 141 and 143, is in communication with the ambient atmosphere by suitably provided exhaust oroutlet ports 147.

Consequently, by correlating FIG. 6 with FIGS. 1 and 11, it will be observed that as each of theholder assemblies 40 pass successively into and out of stations AD, its corresponding bore in rotatable plate 121 will be either in communication with the atmosphere viastationary grooves 141 and 143 to retractflexible member 41, or withpressure source 110, by way ofgrooves 142 and 144, to urge and maintain flexible member in the extended position. At locations A and C, withmember 41 being retracted, it is simple to unload or load the article on the machine.

In this regard, the loading at station A (FIG. 1) and unloading at station C of the article (core 1 of the exemplification), may be accomplished manually or by any well known automatic transfer loading and unloading equipment (not shown). In order to expedite loading of the article to be coated, station A may be located near an oven or the like (not shown) where the core has been pre-heated to the requisite temperature, such as in the range of 190 C. to 232 C. Thus, the heated core can readily be removed from the oven as it emerges and loaded onholder assembly 40 at station A.

The coating applying station B will be explained with reference to FIGS. 7 and 8. Special type identical powder applicators, generally indicated bynumerals 151, 152, 153, and 154, are arranged in cooperating pairs for applyingpowder material 155, such as epoxy resin of the kind previously mentioned, onto the side faces, edges and slot walls of core 1. In particular, each of the applicators is identically formed withcentral Venturi channels 156 terminating in anozzle 157 having a divergent exit. Powder is fed to channel 156 and then tonozzle 157 by any suitable manner, by Way of example, from a standard fluidizedbed powder source 160 in FIG. 1, and into the applicators throughhoses 161 andports 162. The channel end remote from the nozzle is attached to pressure source 110 (FIG. 11) througha'timed applicator valve 163, pressure regulator 164 andair lines 165 to develop predetermined pressure in the Venturi channel to causepowder material 155 to be delivered out of thenozzles 157 at low velocity; e.g., the nozzle pressure preferably being below six p.s.i.

The axis of each nozzle is disposed generally parallel to the rotation axis ofholder assembly 40, with a pair of noz zles being spaced apart in face to face relation such that the nozzle exit in each pair is located adjacent the slot edges, during the spraying operation. The axial distance between theface 4 and the exit should be over one-half inch for best coverage of the slot edges.

The manner in which the applicators are supported in powder applying station B may also be seen from FIGS.

7 and 8. The applicators are arranged in apowder collector 170 which reclaims material not deposited on the walls of the articles, and alower hopper 171 returns this unused material tofluidized beds 160 for reuse. Arod 172 adjustably secures each cooperating apir of applicators toaxles 173, 174 by two sets of clampingblocks 175, 176 with each cooperative pair being attached to one axle arranged below (as viewed in the drawings) but in spaced parallel relation to the axis of rotation ofholder assembly 40. This arrangement permits relative adjustment of each applicator in radial, axial, and angular planes relative to the core being coated, as dictated by the dimensions and type of slots of the article. Movement of the applicators between the operative and inoperative locations is effected, as seen in FIG. 2, by astandard air cylinder 177 and crank-gear assembly 178 attached to an extremity of each axle for turning the axle and consequently the applicators. In the inoperative position, the applicators are located such that they clear core 1 andcore holder assembly 40 as these parts are rotated into and out of station B.

Since unloading station C has already been referred to, reconditioning station D will be outlined and may include, by way of illustration, the components shown in FIGS. 2, 9, and 10. More specifically, it will be recalled thatflexible member 41 is maintained in its extended position in station D and is independently rotated therein. Ablade unit 181 or other material stripping device supported axially beyondholder assembly 40 is driven across the outer surface ofmember 41 to clean it or strip it of excess material asassembly 40 is being rotated. This axial movement may be achieved by attachingunit 181 to apiston rod 182 actuated bycylinder 183, the parts being rigidly supported bybeam 185 andwall 22.Unit 181 is moved by the cylinder and rod in the direction of the arrows shown in FIGS. 9 and 10, the unit moving entirely across the axial length offlexible member 41 during the scrapping action. In addition, anozzle 186 may be attached torod 182, directly behindunit 181, for applying a light film of lubricant orwax 188 onto the peripheral surface offlexible member 41 after the excess material has been removed frommember 41 byunit 181. This film serves as a shield onmember 41 to prevent the powder material of station B from becoming embedded into the flexible member. The film also reduces the sliding friction of the core relative tomember 41 when the core is loaded thereon at station A. Of course, if desired this later film applying or similar protective operation could be performed in a separate station disposed angularly beyond station D.

The way in which machine of the illustrated embodiment operates, may be best understood by reference to the FIGURE 11, taken primarily in conjunction with FIGS. 1, 4, 6, and 8. The machine operator energizes the machine by closingmain switch 191 which exciteselectric motors 101 to drivebelts 97 at a pre-selected speed.Flexible member 41 ofholder assembly 40, disposed in loading station A, will be in a retracted position for the reasons already set forth, the holder assembly being exhausted to the atmosphere by reason of valve assembly 115 (FIG. 6). After the article to be coated (heated core 1 of the exemplification), has been slid ontoflexible member 41, operation ofindexer 31 may be initiated by manual control switch or timer means, indicated at 192, which in turn operatessolenoid valve 194 to actuateindex cylinders 33. As assembly holder and bore opening 127 invalve assembly 115 are moved in concurrence from A towards station B, after an angle of 15, opening 127 invalve assembly 115 travels beyondexhaust groove 141 and into communication withgroove 142 in the stationary plate, connecting holder assembly pocket to theair pressure source 110 throughinlet port 146,tube 116, bearingunit 63, andpiston element hole 79 ofcoupler device 61.Flexible member 41 is thus urged to its extended position (the broken lines in FIG. 4) where firm engagement is made with the entire circumference of core bore 2. A pressure of twenty p.s.i. inair pocket 45 is suflicient to perform this movement. Air moving into and out ofpocket 45 has the tendency to effect a slight cooling offlexible member 41, keeping its temperature low.

Switch 192, when closed, also energizes atimer switch 193 which actuatessolenoid valve 197 to open theair cylinders 177 to pressuresource 110 afterrotatable member 25 has been stopped byindexer 31 withholder assembly 40 disposed in station B. The applicators are swung from their inoperative (FIG. 7, by operation of cylinders 177) to the operative (FIG. 8) positions where theapplicator nozzles 157 are arranged adjacent to thefaces 4 of the core. It should also be noted that as theholder assembly 40 is being turned into station B, sheave 96 on shaft end travels into frictional engagement with the continuously rotatingbelt 97, and theholder assembly 40 is independently rotated at a predetermined speed. In order to keep the powder withincollector 170, a thincircular plate 29 may be supported onrotatable member 25,adjacent coupler device 61, by bolts andintegral posts 28 projecting outwardly from themember 25. In addition, a generallyU-shaped cover 170a may be mounted overpowder collector 170 and provided with an opening sufficiently large to permit core 1 andholder assembly 40 to be rotated into and out of the powder applying station.

Powder is fed to the applicators by Venturi action afterassembly 40 is in station E. Initiation of the powder application is also started bytimer switch 193 which controls actuation ofapplicator solenoid valve 163.Powder 155 is applied onto the core faces 4, slot edges, and into theslots 3 as the core is rotated sufficiently slow to permit penetration of the powder material to the center of the core slots. Depending upon the thickness of the layer desired, the nozzle pressures, speed of core rotation, and density of the powder mass being applied, are all regulated to meet the particular layer thickness requirements for the given article. However, it has been found in actual practice that for optimum coating results with respect to magnetic cores for electrical inductive devices, it is desirable to rotate the cores at a relatively low speed, that is, not substantially above thirty r.p.m. while maintaining low powder velocity passing from the nozzle exit (e.g., preferably below six p.s.i.). This slow rotation does not appreciably affect the cooling rate of the core 1 at its exposed surfaces. Good results have been achieved with a synthetic polyester resin of the kind disclosed and claimed in US. Patent No. 2,936,296-Precopio and Fox, assigned to the General Electric Company as well as with other insulating powder resins.

Each set of applicators cooperate to direct a mass of powder into the slots from theopposed nozzles 157 such that the opposed powder flows produce particle collision of the opposed streams in the vicinity of the center of the slots. This action appears to create a slight turbulence therein for depositing the powder somewhat uniformly along the extent of the heated core slot walls.Baflies 179 may be mounted on each applicator to redirect the powder which does pass through the slots back into them. The heat from the core melts the powder material on the walls, with the material flowing slightly into a coating, and coalesces into a layer. Sincemember 41 never reaches the melting temperature of thematerial 155, no layer will be formed on the outer surface of the member. Moreover, due to the masking function of the expanded flexible member, powder is deposited on thebore 2 of core 1.

Once melted, the resin usually remains in a liquid form in the neighborhood of nine to twelve seconds after it has been deposited on the walls. If the powder material is allowed to coalesce on the walls of core 1 at the periphery ofmember 41 into a somewhat hardened layer, a bridge may be formed, making it dilficult to remove the core from the holder assembly. Moreover,

once hardened, this bridge may form an undesirable ridge at that location. Thus, it is desirable to dismantle core 1 frommember 41 in unloading station C as soon as possible. When the desired amount ofmaterial 155 has been deposited on core 1, which may take no longer than seven-nine seconds,timer switch 193 opens andsolenoid valves 163 and 197 are deenergized to discon tinue the application of powder and to return the applicators to their inoperative positions.Indexer 31 then turnsmember 25 andholder assembly 40 from station B to unloading station C.

Just prior to entrance ofholder assembly 40 into the unloading station C, boreopening 127 becomes aligned withstationary groove 143 andoutlet port 147 ofvalve assembly 115, thus ventingholder pocket 45 to the ambient.Flexible member 41 is returned to its retracted position, allowing the core 1 to be readily and rapidly dismantled fromassembly 40. Consequentlymember 41 and core 1 are in firm engagement for the greater portion of the angular travel of the parts from station A to C to insure proper support for core 1. Moreover, since operation offlexible member 41 is performed in the preferred embodiment during each indexing part of the cycle, e.g., a duration of 1% seconds, no time is lost at the loading and unloading stations to accomplish this function. The

reconditioning operations performed onmember 41 in the reconditioning station D have already been described in detail. No further detailed explanation will be included here other than to state that its operation may also be regulated bytimer switch 193 which initiates operation ofsolenoid valve 195 which in turn controlscylinder 183 to cause the axial travel ofpiston rod 182.

It is important to note that except for the indexing movement ofholder assembly 40 between the stations (e.g., 1% seconds), all operations, such as the loading and unloading of the work article and the reconditioning operation conducted on thework holder assembly 40, are performed while the powder material is being applied to the article in station B. Since the powder application part of the cycle may be completed in about ten seconds, the entire cycle through stations AD requires no more than forty-six seconds. Of course, this time duration for a single cycle maybe varied as desired.

From the foregoing it-will be recognized that the machine of the present invention can be utilized to coat articles other than stator core 1. By way of example, FIG. 12 illustratescoupler device 61 detachably mounting hold erassembly 40a which, by way of example, is adapted to support a shaft 1a of a dynamoelectric armature core or the like. In this embodiment,holder assembly 40a comprises an outercast coupling shell 201 having acentral passageway 202 enlarged atcoupling end 203 and provided withinternal threads 204 for engagement with the external threads ofcoupler plate 69. Pins 205 may be used to lock these pieces together, if desired, to prevent relatively angular movement. Prior to the attachment of thecoupler shell 201 todevice 61, a threadedpin 207 is placed intoinsert 74 and connected topiston element 78 viahole 79. The other end of the pin is received in acap 208 which abuts against asleeve 209, having shaftaccommodating recess 210 for receiving shaft 1a. This sleeve in turn, is wedged tightly against a movable flexible member orcollet 41a. As withflexible member 40 for supporting stator core 1,collet 41a is movable between a retracted position (shown in solid in FIG. 12) and an extended position in which the collet is forced to grip the shaft to support it. This movement is accomplished in the exemplitication by air pressure which entersinner chamber 68 ofdevice 61, and applies force against the face ofpiston element 78, overcoming the bias of spring 81, to cause the element to travel in the direction of the arrows.Pin 207,cap 208,sleeve 209, and finallycollet 41a are accordingly forced to the right as viewed in FIG. 12. The collet is reduced in cross-section and is squeezed around shaft 1a by the innerinclined wall 212 of the shell.

Air pressure is supplied to thecoupler device 61 in the same manner as that already explained in connection withholder assembly 40. For instance, whenever boreopenings 127 inrotatable plate 125 are in communication withgrooves 142 and 144, movement of the collet into the extended position will be effected for engaging shaft 1a to support it.

Needle valve of element 81, inoperative whendevice 61detachably mounts assembly 40, is functional in the support ofassembly 40a. It allows a small flow of air to be directed to and through the collet during the coating cycle for blowing the powder away from the collet without adversely affecting the layer being formed on the article.Air ducts 211, 214, and 215 connect the needle valve with the collet for this purpose. When valve ventsdevice 61 to the atmosphere at the loading and unloading stations,collet 41a will be returned to its retracted position by spring 81 to permit movement of theshaft 101 relative to the collet.

The principle features and advantages of the present invention have been suggested during the description of the illustrated embodiment thereof. The process permits the use of a machine which is simple in construction, 'efiicient and rapid in operation, and is capable of use in the mass production manufacture of articles having differing configurations. The method of this invention is also versatile in nature and can be used with a number of work holder assemblies and machines of different constructions. It should be appreciated that in order to increase the output of the machine, more than the four stations illustrated could be employed which, of course, would require a corresponding increase in the number of work holder assemblies. Additional stations, similar to those of the present invention, could also be located coaxial with the illustrated embodiment and operated by a single indexer. Furthermore, a satisfactory coating may be applied onto the article even though the article must be in a heated condition during the coating operation and the article has a tendency to lose its heat at a high rate from the exposed surfaces to be coated.

While in accordance with the patent statutes, we have described what at present is considered to be the preferred embodiments of our invention, it will be obvious to those skilled in the art that numerous changes and modification 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 we claim as new and desire to secure by Letters Patent of the United States is:

1. The method of forming a layer of insulating material on the surface of axially extending winding accommodating slots, and slot edges of a magnetic core for use in an electric inductive device comprising the steps: mounting the cgre in pre-heated condition onto a holder and moving th holder into firm frictional engagement with a selected surface of the core for support thereof; driving the holder and core held thereby into a spray coating station; applying insulating material in powder form onto at least the slot surfaces thereof from powder applicators disposed at least at one location adjacent each side of the core while concurrently turning the holder at a speed sufficiently low to permit the disposition of powder on the slot surfaces throughout the axial length of the slots and covering the slot edges, thereby to form a generally uniform coating thereon with the holder being maintained in communication to a source of fluid pressure, and with the holder aiding to prevent the formation of a layer of insulating material on at least the selected surface of the core frictionally engaged thereby; driving the core and holder away from the coating station, and removing the coated core from the holder within twelve seconds from the time of powder deposition on the slot surfaces to prevent the formation of a hardened insulat- 1 1 ing bridge at the selected surface of the core adjacent holder.

2. The method of claim 1 in which the magnetic core is a salient pole stator core and during the step of applying insulating material in powder form onto at least the slot surfaces, at least some of the powder which may have passed entirely through the slots of the salient pole stator core is re-directed by baffle means back into the slots for deposit thereof onto the slot edges and surfaces.

3. The method of claim 1 in which the insulating material is applied onto at least the slot surfaces at a pressure not substantially in excess of six p.s.i. from the powder applicators as the holder is turned at a speed not substantially above thirty r.p.rn. thereby to insure powder collision in the vicinity of the axial center of the slots without appreciably reducing the pre-heated condition of the core.

4. The method of forming a layer of insulating epoxy resin material on axial extending winding accommodating slots, side faces, and slot edges of a stator core for use in a dynamoelectric machine comprising the steps: mounting the stator core in pre-heated condition onto a flexible annular holder in a retracted position, increasing the transverse dimensions of the holder from the retracted position into firm frictional engagement with the bore of the stator core; driving the expanded holder and stator core held thereon angularly into a spray coating station; spraying powdered epoxy resin insulating material onto the side faces, slot edges and internal slot surfaces thereof from powder applicators disposed in oprative positions at least at one location adjacent each side of the stator core while concurrently rotating the holder and core at a speed sufficiently low to permit a uniform deposition of powder throughout the axial length of the slots with the expanded holder serving to prevent formation of a coating on the stator bore; driving the stator core and holder angularly away from the spray coating station and de creasing the transverse dimension of the holder to return the holder to its retracted position, and removing the coated stator core from the retracted holder within twelve seconds from the time the powdered resin is deposited onto the side faces, slot edges and internal slot surfaces of the stator core.

5. The method ofclaim 4 in which, subsequent to the removal of the coated stator core from the retracted holder, the holder is prepared for mounting another stator core thereon by cleaning excess powder from the periphery of the holder and applying a film of frictionreducing material thereon.

6. The method ofclaim 4 in which before the step of spraying powdered epoxy resin insulating material onto the internal slot surfaces of the stator core, the powder applicators are moved from inoperative positions to the operative positions, and returned to the inoperative positions after the powdered epoxy resin has been sprayed onto the internal slot surfaces thereby to allow the core to be driven angularly into and out of the spray coating station.

References Cited UNITED STATES PATENTS 2,336,946 12/1943 Marden et a1. 117-18 3,016,875 1/1962 Ballentine et a1. 117-18 X 3,025,188 3/1962 Larsh et al 117-230 3,028,266 4/1962 Larsh 117-232 3,034,479 5/1962 Larsh et al. 118-406 3,074,808 1/1963 Harrison 117-18 X 3,093,510 6/1963 Olson et a1. 117-18 X 3,185,131 5/1965 Manning 117-21 X 3,226,245 12/1965 Dettling et al. 117-21 3,247,004 4/1966 Dosser 117-18 WILLIAM D. MARTIN, Primary Examiner.

P. F. ATTAGUILE, Assistant Examiner.

Claims (2)

1. THE METHOD OF FORMING A LAYER OF INSULATING MATERIAL ON THE SURFACE OF AXIALLY EXTENDING WINDING ACCOMMODATING SLOTS, AND SLOT EDGES OF A MAGNETIC CORE FOR USE IN AN ELECTRIC INDUCTIVE DEVICE COMPRISING THE STEPS: MOUNTING THE CORE IN PRE-HEATED CONDITION ONTO A HOLDER AND MOVING THE HOLDER INTO FIRM FRICTIONAL ENGAGEMENT WITH A SELECTED SURFACE OF THE CORE FOR SUPPORT THEREOF; DRIVING THE HOLDER AND CORE HELD THEREBY INTO A SPRAY COATING STATION; APPLYING INSULATING MATERIAL IN POWDER FORM ONTO AT LEAST THE SLOT SURFACES THEREOF FROM POWDER APPLICATORS DISPOSED AT LEAST AT ONE LOCATION ADJACENT EACH SIDE OF THE CORE WHILE CONCURRENTLY TURNING THE HOLDER AT A SPEED SUFFICIENTLY LOW TO PERMIT THE DISPOSITION OF POWDER ON THE SLOT SURFACES THROUGHOUT THE AXIAL LENGTH OF THE SLOTS AND COVERING THE SLOT EDGES, THEREBY TO FORM A GENERALLY UNIFORM COATING THEREON WITH THE HOLDER BEING MAINTAINED IN COMMUNICATION TO A SOURCE OF FLUID PRESSURE, AND WITH THE HOLDER AIDING TO PREVENT THE FORMATION OF A LAYER OF INSULATING MATERIAL ON AT LEAST THE SELECTED SURFACE OF THE CORE FRICTIONALLY ENGAGED THEREBY; DRIVING THE CORE AND HOLDER AWAY FROM THE COATING STATION, AND REMOVING THE COATED CORE FROM THE HOLDER WITHIN TWELEVE SECONDS FROM THE TIME OF KPOWDER DEPOSITION ON THE SLOT SURFACES TO PREVENT THE FORMATION OF A HARDENED INSULATING BRIDGE AT THE SELECTED SURFACE OF THE CORE ADJACENT HOLDER.

3. THE METHOD OF CLAIM 1 IN WHICH THE INSULATING MATERIAL IS APPLIED ONTO AT LEAST THE SLOT SURFACES AT A PRESSURE NOT SUBSTANTIALLY IN EXCESS OF SIX P.S.I. FROM THE POWDER APPLICATORS AS THE HOLDER IS TURNED AT A SPEED NOT SUBSTANTIALLY ABOVE THIRTY R.P.M. THEREBY TO INSURE POWDER COLLISION IN THE VICINITY OF THE AXIAL CENTER OF THE SLOTS WITHOUT APPRECIABLY REDUCING THE PRE-HEATED CONDITION OF THE CORE.

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