US2000715A

US2000715A - High speed commutator

Info

Publication number: US2000715A
Application number: US635514A
Authority: US
Inventors: Gaylord W Penney
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1932-09-30
Filing date: 1932-09-30
Publication date: 1935-05-07
Anticipated expiration: 1952-05-07

Description

May 7, 1935- G. w. PENNEY HIGH SPEED CQMMUTATOR Filed Spt. so, 1952 INVENTOR Gaylord W. Penney ATTOhNEY Patented May 7,, 1935 UNITED STATES PATENT OFFICE 2,000,715 men srnnn COMMUTATOR Pennsylvania Application September 30, 1932, Serial No. 635,514

'lClaims.

I My invention relates to commutators for electric machines and more particularly machines operating at a high speed of rotation or high temperature or both. One object of my invention is the provision of a commutator that remains properly centered regardless of the speed of operation of the machine or the temperature of the commutator. 7

Another object of my invention is to provide a :commutator that is simple in structure, inexpensive in design, may be readily manufactured and installed, and is not distorted by temperature variations.

' A still further object of my invention is the provision of a commutator, the segments of which may freely yet uniformly expand in both the longitudinal as well as the radial direction.

It is also an object of my invention to maintain a commutator properly centered for its entire range of operating temperatures.

It is also an object of my invention to maintain a commutator properly centered for its entire range of operating speeds. I

A further object of my invention is the provision of a commutator of such unique and novel structure as to prevent the segments from sliding on their supporting structure with changes in temperature. a

One other object of my invention is to maintain the arching pressure of the segments substantially constant and uniform thereby preventing excessive stresses in the commutator and the consequent distortion of the commutator.

Other objects and advantages will become apparent from a study of the following specification particularly when done in conjunction with the accompanying drawing, in which:

Figure 1 is a view showing a longitudinal section of a portion of a commutator or cylinder constructed in accordance with my invention;

Fig. 2 is a view, on a larger scale than Fig. 1, showing the relativeposition of the inner clamping ring to the machine shaft, to the insulating layers, and to the portion of the supporting sleeve not engaging the shaft of the machine; and

Fig. 3 is a view, on a larger scale than Fig. 1, showing a "commutator mounted on a shaft'and illustrating the distortions, somewhat exaggerated, of the clamping and centering disc relative to a heated commutator operating at a high speed. a

Referring more particularly'to Fig. 1 of the drawing, reference character I designates a bushing or sleeve which constitutes the support for the commutator druml. The commutator drum 2 is built up of a plurality of commutator segments 3 which, as to their individual configuration, are substantially rectangular wedge-shaped members and thus when assembled constitute a drum consisting of a hollow cylinder. Disposed about the bushing I is a shell of insulating material 4 which is made somewhat thicker at the point 5 so that the overall diameter at point 5 is somewhat greater than the diameter, for the remainder of the bushing and insulating shell. The commutator drum is disposed concentrically with the bushing and firmly engages the insulating material 4 at point 5, and with the aid of the shrink ring 8 firmly mounts the commutator drum on the bushing. Y I

A retaining ring 6 is disposed adjacent the inner or left hand end of the bushing for protecting the insulation 4 at point 5 and helps to prevent any shifting of the commutator drum in the direction of the machine M using the commutator that is toward the left. Each commutator segment 3 is provided with a neck or connector 9 which extends radially outwardly from its inner end, the connectors are obviously for the purpose of electrical connection with the armature windings of the machine provided with the commutator. The commutator drum is further provided with shrink rings I8 and 28 which are chosen of a kind of material, preferably steel, so that their section may be a minimum and, further,.each of the shrink rings is insulated from the commutator segments 3 by annular strips of insulating material I, I1 and 21, respectively. Since the shrink rings grip the commutator segments with considerableforce, a rigid connection between the drum and the bushing is maintained at point 5 of the insulating material 4 and, further, the commutator drum is held in spaced relation with reference to the insulating material 4 and the bushing for the greater portion of the length of the bushing. The bushing is made of steel or other material having some flexibility and particularly, since the thickness of the bushing at point It is less than at other points, the bushing which is usually of resilient steel, has sufilcient radial flexibility to remain firmly against the bars or drum 2 at all operating temperatures. Furthermore, when the bushing is mounted on the shaft M which is of a smaller diameter than the internal diameter of the bushing at the portion it a clearance I5 is produced between the shaft and the bushing. In this connection see Fi 2.

In view of the radial flexibility of the steel bushing, the action of the shrink ring 8 in coacting with the thin portion [6 at the clearance IE will be such as to tend to radially spread the right hand or outer ends of the commutator segments. The segment thus at no time frictionally engages the bushing or the insulation thereon if properly centered. To prevent such radial spreading and to keep the commutator drum properly centered with reference to the bushing, a centering plate I8 is provided on the outer end of the bushing having a ring [0 firmly secured to the bushing and having a flexible disk portion l firmly secured to the ring II and to a relatively heavy annular portion l2 which surrounds the disk-like portion H. The annular portion i2 is sufficiently heavy that expansions and contractions of the commutator drum do not distort the ring 2. The ring I2 is provided with a cylindrical projection l3 engaging the outer periphery of the shrink ring 28 to firmly, yet resiliently, hold the free end of the commutator drum 2 centered on the bushing or the shaft H of the machine M.

From the foregoing explanation of the construction of my commutator, it is apparent that the individual segments and the drum as a whole, being secured at one end only, are free to move longitudinally with reference to the bushing with changes of temperature. Any expansions or conractions of the commutator drum, therefore, do

not distort the drum. Furthermore, the centering plate i9 having a flexible disk like portion I l permits of longitudinal movement of the outer or right hand end of the drum whereas the cylindrical projection l3 permits some radial motion of the individual commutator segments due to transverse or radial expansion resulting from either changes in temperature of the commutator or resulting from the centrifugal force of the commutator or both.

As is well known in former practice, commutators were either arch bound or drum bound. The arch bound construction was such that excessive stresses were set up in the copper or material when hot and, in addition, the bars between the shrink rings tended to lift off from the shaft or bushing so that they would neither remain centered nor present a smooth surface. Further, in the drum bound construction, the bars are required to slide along the bushing when expanding or contracting as the result of changes in temperature. The commutator construction I provide permits a free movement of the drum longitudinally of the bushing and also permits considerable radial movement of the individual segments of the commutator without in any way destroying the symmetry or the concentric position of the drum with reference to the shaft of the machine.

To clearly comprehend what takes place when the outer or right hand end of the drum is moved longitudinally and radially, reference should be had to Fig. 3 Where the distortions in the centering plate is are illustrated in somewhat exaggerated form. It will be noted that the annular portion l2, for any given section, has substantially no rotation about a given axis but all of the flexing takes place in the resilientdisk like portion l i and the resilient cylindrical portion l3.

While I have shown one specific embodiment of my invention in the foregoing disclosure and the accompanying drawing, it is obvious that other modifications falling within the spirit of this invention may be readily devised by those skilled in the art after having had the benefit of the teachings of this invention and I, therefore, Wish to be limited only by the pertinent prior art and the scope and spirit of the appended claims.

I claim as my invention:

1. A high-speed high-temperature commutator comprising, in combination, a support, a plurality of commutator segments, mounting means for securing corresponding ends to said support, said means being designed so that said other corresponding ends of the segments are spaced from the support and are subjected to a force tending to move the segments radially with reference to the support, and centering means for resiliently retaining said other corresponding ends in a given relative position, thereby preventing independent radial movement of the respective segments.

2. A commutator comprising, in combination, a shaft, 2. bushing mounted rigidly on the shaft but having a clearance between the shaft and bushing at the inner end of the bushing, insulating material on the bushing, commutator bars, suitably insulated from each other, disposed about said bushing; in spaced relation to said insuiating material on said bushing except adjacent the inner end of the bushing, clamping means near the inner end of the commutator bars to rigidly interconnect said bars with said bushing at one end of said bars, and a clamping disc secured to the outer end of the bushing and adapted to resiliently engage the outer' end of said bars to permit longitudinal and radial expansion independently as well as simultaneously of said bars.

3. A commutator structure comprising, in combination, a shaft, a bushing, snugly fitting said shaft except at one end thereof at which end there is a cylindrical space between the shaft and bushing, a sheet of insulating material covering said bushing, commutator segments, shorter than said bushing, suitably insulated from each other", disposed substantially about the mid-portion of the bushing, and engaging said insulating shell at the end having the cyiindrical space, a. clamping member disposed about said segments at the cylindrical space and firmly gripping said segments so that the other ends thereof tend to spread radially, and a resilient centering member secured to the other end of the bushing to limit such spreading but which permits the ends of the segments to expand longitudinally and radially independently and simultaneously without distortion of the commutator.

4. A commutator structure comprising, in combination, a commutator drum comprising a plurality of segments, a support, means for holding one endof the drum substantially in fixed relation to the support, and a centering means mounted on the support and engaging the drum, said centering means including. a clamping ring engaging the support, a resilient disc portion on the ring, a relatively heavier rigid annular portion integral with and surrounding said disc portion, a resilient cylindrical portion engaging the outer periphery of said drum.

5. A commutator structure comprising, in combination, a bushing having a somewhat resilient cylindrical portion at one end, a plurality of commutator segments substantially rectangular in shape assembled to constitute a hollow drum whose internal diameter is somewhat greater than the external diameter of the bushing, means for fixing one end of the drum to the bushing at the resilient cylindrical portion of the bushing so that said segments are biased to move radially with reference to the bushing and the drum encircles the bushing so that substantially the entire drum is spaced from the bushing and tree to move relative thereto with changes in operating conditions and means secured to the other end of the bushing including resilient means for maintaining said drum concentric with said bushing for varying operating conditions and resilient means adapted to permit radial movement 0! the free end of the drum.

6. A commutator structure comprising, in combination, a bushing, a plurality of commutator segments substantially rectangular in shape assembled to constitute a hollow drum whose internal diameter is somewhat greater than the external diameter of the bushing. means for fixing one end of the drum to the bushing to encircle the same so that substantially the entire drum is spaced from the bushing and tree tomove relative thereto with changes in operating temperatures, and a member having a resilient disc-like portion and a resilient cylindrical portion for engaging the drum and the support to maintain said drum concentric with said bushing for varying operating temperatures but providing for independent and simultaneous radial and longitudinal movement 01 the free end of the drum.

7. A commutator structure comprising, in combination, a plurality oi commutator segments each being substantially rectangular in section assembled to constitute a hollow drum, a cylindrical support, clamping means for securing a relatively small cylindrical portion of the drum to the support and holding the remainder in spaced or tree concentric relation to the support, a centering plate adjacent the free end of the drum secured to the support and engaging the outer periphery of the free end of the drum to hold the drum centered with reference to the support, said plate having a flexible disc-like portion to permit longitudinal movement or the drum relative the support and having a flexible cylindrical portion for permitting radial movement of the elements of the drum.

' GAYDORD W. PENNEY.