US2080371A - Motor - Google Patents

Description

May 11, 1937. L. HAMMOND 2,080,371

MOTOR Filed May 9,` 1932 will g2 T, T7@

21 )fic/M Patented May 11, 1937 PATENT OFFICE MOTOR Laurens Hammond, Chicago, lll., assigner to The Hammond Clock Company, Chicago, IIL, a corporation oi' Delaware Application May 9, 1932, Serial No. 610,098

9 Claims.

The present invention relates to alternating current electric motors, and is particularly concerned with small electric motor units adapted to be used for driving the mechanism of clocks,

timing devices, or similar apparatus which does not require a very high torque.

One of the objects of the invention is the provision of an improved electric motor unit of the class described which is adapted to be manufaclu'tured very economically so that the device may be placed within the means of a vast number of purchasers and employed for numerous purposes in cases Where the cost of the more expensive devices of the prior art would be prohibitive.

l5 Another object of the invention is the provision of an improved motor of the class described which is more quiet than the devices of the prior art, which is more efficient than the devices of the prior art by virtue of the arrangement and construction of its parts, and which is adapted to give service for long periods of time without developing noisy defects due to use or wear.

Another object is the provision of a device of the class described having a minimum number of parts, and the parts of which lend themselves readily to manufacture by stamping operations so that expensive machining operations lmay be eliminated in so far as possible.

Another object of the invention is the provision of a motor of the class described which is selfstarting and which has a greater torque than devices of the same size of the prior art at synchronous speed. I i y Other objects and advantages of the invention willbe apparent from the following description and from the drawing, in which similarcharacters `of reference indicate similar parts throughout the several views.

Referring to the single sheet of drawing:

Fig. 1 is a top plan view of the motor, with the pinion removed;

Fig. 2 is a transverse sectional view taken on the plane of the line 2-2 of Fig. 1; and

Fig. 3 is an exploded view in perspective, showing the parts one above the other in position to be assembled, with certain of the parts in sec tion to show the details of construction.

The present illustration of the invention is made with the spindle in vertical position and the rotor on top, but it should be understoody that the motor may be mounted in any position, and in fact is most frequently mounted with the spindle in a horizontal position. The magnetic thrust on the rotor is preferably suillcient to support the rotor in proper position, even when the rotor is inverted.

For convenience in explanation of the invention, the terms upper and lower have been used in connection with the drawing, but it 5 should be understood that these terms are merely used in their relative sense, referring to one part relative to the location of another, and the terms are not intended to be applied in any limiting sense. 10

Referring to Fig. 3, the complete motor preferably includes the parts which are indicated as follows, rotor disc I0, upper shell Il, upper pole piece disc I2, shading disc I3, lower pole piece disc I4, coil I5, core sleeve I6, core sleeve 15 Il, core washer I8, core washer I9, lower shell 20, securing screw bolt 2l.

It should be understood that all of the details and specific features of these elements are not necessarily required in every embodiment of the invention, and simpler embodiments of the invention, not having all of the advantages of thev preferred construction, need not include all of the foregoing elements.

The present invention includes not only the preferred construction, but all of the simpler embodiments of the invention which may be constructed to utilize any of the advantages of the present construction without embodying Vall of the features-described herein. l

The` motor preferably comprises a casing which is formed of the upper shell II and lower shell 2D, and which is also adapted to form a part of the magnetic circuit of the motor when assembled as shown in Fig. 2. Both of these members may be stamped or drawn out of sheet metal, such as sheet steel, having special magnetic qual ities, and preferably including', a predetermined percentage of silicon.

The lower shell 20 preferably comprises a substantially cylindrical sheet metal member having a fiat bottom 22 and a substantially cylindrical pheripheral wall 23. The bottom 22 is provided with an aperture 24 for receiving the screw bolt 2| which is adapted to secure the parts of the motor together and also to secure the motor to a supporting frame member 25 having an aperture 26 The upper shell II comprises a` substantially cylindrical cup shaped member having a cylindrical peripheral wall 21, the inner surface of which is complementary to the outer surface of the peripheral wall 23 of the lower shell. The upper and lower shells are so proportioned that they may be secured together by close frictional 55 engagement of the parts of these walls which engage each other in Fig. 2, and the casing may be assembled and secured together by merelypressing the upper and outer shell II upon the lower and inner shell 2li with the other parts confined in the shells.

The upper shell II has a substantially circular aperture v28 in its bottom 29, the` periphery of the aperture 28 being provided with radially extending slots 3B forming a multiplicity of pole pieces 3Ilocated at regularly spaced points about the periphery of the aperture 28 and projecting radially inward.

The coil I5, which is located in the shell 20, preferably consists of a preformed coil of insulated wire of a predetermined number of turns, the coil being provided with ilat ends 32, 33.' a substantially cylindrical periphery 34, and a cylindrical aperture 35 passing through the coil. The coil is covered with an insulating layer 36 of paper, tape, thin fiber, or other suitable insulation. f

'I'he coil I5 is provided with a pair of leads 31, 38 which project from the casing II, 2|) through an aperture 39 which is formed by a slot 40 in the upper shell.

'I'he coil I5 may be supported in central position in the shell 20 by means of a plurality of sleeves I6 and I1. 4Each of the sleeves I6, I1 consists of a circular tube or a strip of metal formed into the shape shown, and preferably provided with a slot 4|, 42 extending from one end of the sleeve to the other to eliminate excessive eddy current losses. l

The sleeve I6 is adapted to t within the sleeve I1, and the sleeve I1 ts within the aperture 35 in the coil I5, the slots 4I, 42 being preferably staggered.

Any number of sleeves may be employed to increase the number of laminations in the sleeve core. In the embodiment illustrated, two sleeves are employed for the reason that satisfactory results are secured with a minimum number of sleeves, and such a structure may also be manufactured most economically.

When the coil is energized, the ilux path is through the sleeves, I6, I1and the shells I|,.20. At the lower end of the sleeves I6, I1 the flux ex tends outward radially in the bottom of the shell 20, and it will be evident that the cross section of the ux path at any point in the bottom 22 would be equal to the thickness of the metal at that point multiplied by the width of the path at that point. The width of the path at any point would be determined by the circumference of a circle drawn at that point with the axis of the screw 2| as a center. The cross section of that part of the core which is formed by the bottom 22 would increase in a radial direction, and the point of minimum cross section of the core would be immediately below the lower ends of sleeves I6, I1, were it not for the core washers I8, I9, which are included for the purpose of providing a ux path of substantially constant cross sectional area. Thus the washer I9 comprises a circular disc of magnetic sheetsteel, having a centrally located aperture 43 forv passing the screw bolt 2| and a radially extending slot 44 for reducing eddy current losses.

The washer I 8 comprises a member of exactly similar structure, but of lesser diameter, and the washers are preferablyassembled with the slots staggered. Any number ot washers or laminations may be employed, but a flux path of sufllciently constant cross sectional area is provided by the use of two washers, as shown. The washers I8 and I 9 when assembled with the bottom 22 of shell 20 increase the cross sectional area of the flux path in the bottom by increasing the thickness of the bottom assembly toward the center and decreasing the thickness of the core toward the outer edge of the bottom. The core washers I8 and IS are clamped between the bot-` tom 22 and coil I5 and secured in place by the same screw 2| which secures the other parts of the assembly together.

The lower pole piece disc I4 comprises a disclike metal member constructed oi magnetic sheet metal having a plurality of upwardly extending pole pieces 45 located at regularly spaced points about the periphery of the disc I4. The disc is provided with a centrally located circular aperture 46 adapted to receive a cylindrical core plug 41 which is provided with an axially located threaded bore 48 having threads complementary to the threads 49 on the end of screw bolt 2|. The plug 41 is also provided with a counterbore 50 forming an annularshoulder 5I against which is seated a disc 52 of insulating material, such as an insulating iiber, constructed of layers oi fabric impregnated with a phenolic condensation compound. The size of the disc 52 is such that it may be xedly retained in the counterbore 50 against the shoulder 5| by the frictional engagement of its periphery with thewall of the counterbore 50.

The plug 41 is alsov provided with a second counterbore 53, thereby forming a second annular seat 54, against which is seated a similar fiber disc 55, having a cylindrical aperture 56, which forms a bearing for a spindle 51. The disc 55 may be permanently secured in the counterbore 53 by staking over the adjacent metal of the plug, thereby forming an overhanging shoulder 58 of metal for retaining the disc 55 in place. groove 59 is formed by the roller of the tool which effects the staking operation.

The plug 41 is provided-with a radially extending portion 6|), having a lower annular shoulder 6I for securing the parts I2 to 2| together in The the shells II, 20. It desired, the upper pole piece i disc I2 may have its aperture 62 of such a size that the plug 41 has a close frictional fit in the aperture 62. 'I'he upper pole piece disc I2 is preferably formed with a circumferentially extending offset 63 spaced slightly from the border of the aperture 62, thereby locating vthe central part 54 of the disc I2 in a plane slightly below the outer part 65 of the disc I2 and forming a space between the outer portion of disc I2 and disc I4 for receiving the shading disc I3. The shading disc I3 comprises a substantially circular sheet metal member which is preferably constructed of nonmagnetic metal having electrical conducting properties, such as, for example, copper. The shading disc I3 is provided with an enlarged centrally located aperture 66 adapted to receive the offset portion 63 of the upper pole piece disc I2.

The discs I2, I3 and I4 may be nested together upon the plug 41, and the annular shoulder 6I, engaging the uppermost disc, may draw all of thes parts together into engagement with the coil 5.

The shading disc is preferably provided with a plurality of outwardly extending lugs 61 which terminate in upwardly extending lugs 68. The lugs or fingers 68 are preferably so formed that they ilt within thelslots 3l in the upper shell and that they engage the peripheral edges llv o! the slots 3l to eiIect an accurate centering of the disc assembly with respect to the shell I| at the 5 upper end of the motor. Lugs 'il may i'rictio'nally and resiliently engage the inner edges of the top 13 at the bases 89: of the slots 30, and by virtue of the interengagement between the discs I2, Il and Il the pole pieces carriedby the l0 Vdiscs I2 and Il are also accurately centered with respect to the other parts at the top oi' the motor.

The upper pole piece disc I2 carries a multilplicity oi regularly spaced outwardly and upwardly extending pole pieces of predetermined l5 width, which are located in the slots 30 in predetermined position with respect to the pole pieces 3| of the upper shell. 'I'he upwardly extending pole pieces 45 of the lower pole piece disc I4 are also located in the slots 30 in spaced relation to 2^) the pole pieces 3| and 10. 'I'he proportions oi' the cross ,sections of the pole pieces 45, 10, and 3| are preferably in the ratio of four to ilve to seven respectively. It will thus be observed that the shading disc I3 is interposed between the pole piece discs I2 and Il at the upper end of the motor, thereby causing the ilux to lag in prede-A termined poles.

The rotor disc I0 preferably comprises a magnetic sheet steel member ot silicon steel which is preferably provided with four radially extending slots 1| located at equally spaced pointsabout the periphery of the disc. 'I'he purpose o1' the slots 1| is to increase the torque at synchronous speed.

The disc I0 is provided with a centrally lof cated aperture 12, which is received upon the cy` lindrical portion 13 of a hub 14. 'I'he disc may be secured between an annular shoulder 15 and the riveted-over portion 16 of the hub. The hub is provided with an axially extending cylindrical aperture 11 and is secured upon the spindle 51V by a close frictional lit between these parts. The spindlefr51 mayvbe suitably scored or grooved in the hub-and's'p'indle.A A

'I'he rotor disc I0 is preferablyl located above the poles 3|, "45 and 10 in order to produce anl axial thrustV upon the spindle 51', which tends to maintainthe conically pointed end 18er-the spindle in engagement with thefilber. discgjZ and prevents a tendency toward rattling or other y noisy defects. The spindle may be provided with a pinion 19 and with an auxiliary bearing at its upper end in the'torm of a circular aperture 80 in a similar fiber disc 8| carried by a frame member 32, which is iixedly supportedwith respect to the frame member 25. The fiber discA 52 constitutes a thrust bearing, while the fiber disc 8| constitutes a 4 .cylindrical bearing i'or the spindle 51. f

The .principle 9i" operation ot the present motor is fundamentally the'. same as 'other electric motors'of the same ti/Defend will be evident to 'gone skilled inthe art. The present structure, however, .embodies a multiplicity of improved ieai'll'l're's, all of which have important advantages in'the particular adaptation of the motor to the 'purpose for which it is intended. Thus the sleeves, laminations and shell form a ilux path of substantially constant cross sectional area. thereby greatly increasing the emciency of the assembly. 'Ihe location of the rotor disc above the pole ends renders the operation of the rotor quiet at all times and permits the maintenance en axial direction to'lprevent rotation between quantitiesat a minimum cost, and expensivev I machining operations are eliminated.

While I have illustrated a preferred embodiment of my invention, many modifications -may be made without departing fromthe spirit of the invention, and I do not wish to be limited to theprecise details of construction set forth. but desire to avail myself of all changes within the scope of the appended claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States, is:

1. In an electric motor, the combination of a pair of cup shaped metallic shells of magnetic metal forming aeasing, with an energizing coil located in said casing, a plurality of concentrically nesting sleeves located in said coil and forming a core', a disc of magnetic material having a plurality of axially extending pole pieces, one of said shells being formed with an aperture having radially inwardly extending pole pieces, and a rotor comprising a disc member rotatably mounted adjacent the ends oi said pole pieces.

2,. In an electric motor, the combination of a pair of cup shaped metallic shells of magnetic metal forming a casing, with an energizing coil located in said casing, a plurality* of concentrically nesting sleeves located in said coil and forming a core,'a disc of magnetic material having a plurality of axially extending pole pieces, one of said shells being formed with an aperture having radially inwardly extending pole pieces, a rotor comprising a disc member rotatablyl mounted adjacent the ends of said pole pieces, said rotor be, ing locatedl outside of said pole pieces, whereby said rotor is subjected to an axial thrust, and a thrust bearing for said rotor to eilect a more quiet 3. In an electric motor, the combination of a cup shaped metal shell with a'plurality of washer laminations ofl decreasing diameter located in said shell to provide a flux path of constant cross secvtional larea,a core, a coil in said shell, a second shell comprising a cup shaped sheet metal member having a multiplicity of inwardly extending pole pieces, a rotor rotatably carried by said core, and a second pole piece unit comprising a disc located above said coil and having pole ends located at right angles to the pole ends of said second shell.

4. In an electric motor, the combination of a cup shaped metal shell with a plurality of washer laminations of decreasing diameter located in said shell to provide a flux path of constant cross sectional area, a core, a coil in said shell, a second shell comprising'a cup shaped sheet metal member having a multiplicity of inwardly extending pole pieces, a rotor rotatably carried by said core, a second pole piece unit having axially extending pole pieces located beside the pole pieces of the rst pole piece unit in between the poles of said wardy extending pole pieces. with an inner pole piece assembly comprising an electrically conductive disc ot non-magnetic metal. with a magnetic pole piece disc on each side oi .said electrically conductive disc, said pole piece discs having axially extending pole pieces locatedabout their peripheries, acoil in lsaid shells, and a rotor rotatably mounted upon said assembly with' respect to said pole pieces'.

6. In an electric motor, the combination of a l disc having a plurality of outwardly and axially extending lugs engaging one of said shells between said radially inwardly extending pole pieces for centering said pole piece assembly with respect to said shells. l

7. In an electric motor, the combination of a pair oi cup shaped shells of magnetic metal, said shells having a press nt with each other, and one of said shells having a multiplicity of radially inwardly extending pole pieces, with an inner pole piece assembly comprising an electrically conductive disc of non-magnetic metal, with a magnetic pole piecedisc on each side of said electrically conductive disc, said pole piece discs having axially extending pole pieces located about their peripheries, a coil in said shells, and a rotor rotatably mounted upon said assembly with respect to said pole pieces, said electrically conductive disc having a plurality oi outwardly and axially extending lugs engaging one ot said shells between said radially inwardly .extending pole.

pieces for centering said pole piece assembly with r respect to saidshells, and a plurality ot split sleeves located between saidpole piece assembly and the lower one oi' said shells, forming a core in said coil.

8. In an electric motor, the combination oi.' a pair of cup shaped shells of magnetic metal, said shells having a press iit with each other, and one oi' said shells having a multiplicity of radially inwardlyextending pole pieces, with an ,inner pole piece assembly `comprising an electrically conductive disc of non-magnetic metal, with a magnetic pole piece-disc on each side of said electrically conductive disc, said pole piece discs having axialy extending pole 'pieces located about their peripheries. a coil in said shells, a rotor rotatably mountedl upon said assembly with respect to said pole pieces, said electrically conductive disc having a plurality oi outwardly and axially extending lugs engaging one of said shells between said radially inwardly extending pole pieces for centering said pole piece assembly` with respect to said shells. a plurality ci split sleeves located between said pole piece assembly and the bottom, one of said shells forming a core in said coil, a plug of magnetic material having an annular shoulder engaging outside said pole piece assembly, said plug engaging in the sleeves of said core, and threaded means extending through said bottom of said shell -and engaging said `plug to clamp said pole piece assembly, coil, shells and sleeves together. I

9. A synchronous motor, comprising a shaft carrying a disc-shaped rotorformed of magnetic material, bearing means including an end thrust bearing for supporting said rotor shaft for rotation, a plurality of groups of poles positioned b`eycnd the periphery' of said disc in a plane spaced s ightly from the plane oi' said disc thereby to exert an axially directed force upon said rotor in a direction to hold said shaft against said thrust bearing, a field winding arranged to be connected to a source of alternating current for energizing said poles and means for shading one of said groups of poles.

LAURENS HAMMOND.

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