CA1119653A - Commutator construction - Google Patents
Commutator constructionInfo
- Publication number
- CA1119653A CA1119653A CA000330382A CA330382A CA1119653A CA 1119653 A CA1119653 A CA 1119653A CA 000330382 A CA000330382 A CA 000330382A CA 330382 A CA330382 A CA 330382A CA 1119653 A CA1119653 A CA 1119653A
- Authority
- CA
- Canada
- Prior art keywords
- commutator
- segments
- strip
- spring segment
- spring
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
- H01R39/00—Rotary current collectors, distributors or interrupters
- H01R39/02—Details for dynamo electric machines
- H01R39/04—Commutators
Landscapes
- Motor Or Generator Current Collectors (AREA)
Abstract
Case 2596 IMPROVED COMMUTATOR CONSTRUCTION
ABSTRACT OF THE DISCLOSURE
An improved commutator construction for a commutator having copper commutator segments spaced around the periphery of a commutator support cylinder with an insulating layer between the cylinder and the segments, uses bands of glass fiber in epoxy resin to hold the commutator segments to the support cylinder.
A spring segment under compression is used between adjacent commutator segments to provide a force in the peripheral direction to permit expansion and contraction while maintaining the concentricity of the commutator.
Mica strips insulate the spring segment from adjacent commutator segments.
ABSTRACT OF THE DISCLOSURE
An improved commutator construction for a commutator having copper commutator segments spaced around the periphery of a commutator support cylinder with an insulating layer between the cylinder and the segments, uses bands of glass fiber in epoxy resin to hold the commutator segments to the support cylinder.
A spring segment under compression is used between adjacent commutator segments to provide a force in the peripheral direction to permit expansion and contraction while maintaining the concentricity of the commutator.
Mica strips insulate the spring segment from adjacent commutator segments.
Description
~L9G5~3 1 Case 2596 IMP~OVED COMMUTATOR CONSTRUCTION
This invention relates to an improved commutator construction.
In D.C. dynamoelectric machines, particularly in the medium and large sizes, it is important that there be no significant sparking where the brushes contact the segments of the commutator. This means that the surface of the commutator on which the brushes ride must ~e smooth and concentric with the axis of rotation of the commutator. The departure from concentricity or runout that can be tolerated may be as small as 0.002 inch, and depending on size and speed the relative displacement between segments that can be tolera-ted may be as small as 0.001 inch or smaller.
Thus the commutator must be made accurately and this 15 accuracy must be maintained. -To prevent small amounts of relative movement between adjacent segments, it is known to buila an arch force into the assembly. That is, the commutator segments and seasoned mica insulation which separates adjacent segments, form an arch. The arch is, of course, any portion of a cylindrical commutator assembly. Thexe are two arrangements which are commonly used to hold the segments of the commutator in position. These arrangements are sometimes referred to as the "cap and cone" construction and the "glass band" construction. The first arrangement, that is the : ~ ', : ' - . -., i.
~.l.g~i53 Case 2596 cap and cone, uses two spaced apart steel rings whichhave cone-shaped annular projections extending towards one another. The commutator segments have correspon-ding cone-shaped channels in opposite ends. The segments are mounted between the rings, using sheet insulation between the cap and the cone, and a system of bolts applies a force to the two rings tending to move them towards one another pressing the projections or caps into the channels or cones in the commutator segments. This fixes the segments in position with the conical surfaces providing a restraining force against radial movement.
When a machine having cap and cone construction is ope~ated, the temperature increases and the copper/
mica arch tends to expand more than the steel rings which support it. Large forces are created with the arch being under compression and the steel cap under tension. Concentricity is maintained within the desired limits because the steel rings are designed to provide sufficient restraint to the radial ~ovement of the copper and mica arch.
The second arrangement for holding the commutator segments in position is much simpler and less expensive. In this glass band construction the commutator segments are mounted over a steel cylinder, with insulation between the segments and the cylinder, and two or more bands of glass fibers are wound around the commutator segments and set in a suitable hardenable plastic material such as an epoxy resin. The bands have a degree of flexibility which permits the arch to expand slightly when the temperature rises. However, with this expansion there is a tendency for the copper/
mica arch to lose its close contact with the cylinder (that is with the insulation surroundin~ the cylinder) and it may deform or bulge in one area causing the ' :.
, :
- : : . , ~
Case 2596 runout to exceed permissible limits for that machine.
To overcome this problem and allow for limited expansionJ a commutator may be made with a slight clearance between the copper segments and the mica insulation which separates them. However the force of the ~rushes on the commutator during running of the machine tends to cause relative movement of the segments and may create such relative movement in the form of a wave-like surface. This may exceed the permissible tolerances for runout and relative displacement.
It appears it may have been the intention when glass band construction was first used, that the mica insulation between segments would provide some resilience to the arch so that the arch could expand and contract more than the steel cylinder on which it is mounted. The mica is, however, too rigid. Other materials, such as rubber coated mica, might provide sufficient resilience but rubber does not age well and will take a permanent set after a period of time at operating temperature.
The present invention is primarily concerned with glass band type construction and provides a spring force in the commutator arch which permits expansion of the arch while retaining a commutator structure with satisfactory runout and relative displacement of segments. The commutator construction of the inyention provides for a spring segment between adjacent copper or copper alloy commutator segments, insulated from the commutator segments by an insulating material such as mica. The spring segments are relatively thin, that is they do not occupy much space in tha circumferential direction, as the deflection required of each segment is small. The spring may be deformed in either the axial or radial direction.
. ,~, , ' , ~ ' d Case 2596 It is therefore a feature of the present invention to provide a spring force in the commutator arch of a glass band construction commutator to accommodate differential expansion.
Canadian Patent No. 54~ 041 - Zollner, issued June 4, 1957, describes a co~nutator construction where the commutator segments are of carbon. In order to ensure current transmission a:Long the length of the carbon segment, a strip of metal is placed beside the carbon segment. The strip of metal is soldered to, or fastened to, or pressed against the carbon segment at spaced points along its length to ensure good current transmission. Where the metal strip is not fastened to the carbon segment but is formed to press against the carbon segment at spaced points, it might provide some spring force, however according to the patent the metal strip must be flexible enough to avoid stressing the carbon segments and consequently would not provide sufficient spring force to stress the arch to allow for differential expansion. Thus, the purpose and properties of the metal strip are different from the spring segment of the present invention.
Carbon commutators have not become popular, perhaps because of the rapid wear.
Accordingly there is provided a commutator for a dynamoelectric machine, comprising a cylindrical commutator support for attaching to the shaft of a dynamoelectric machine, a plurality of commutator segments extending in a generally axial direction around said support and insulated therefrom by a layer of insulating material, a spring segment between predetermined adjacent commutator segments, and a strip of insulating material between each spring segment and at least one of the adjacent commutator segments, the spring segments being compressed between .
;53 Case 2596 adjacent commutator segments to provide a force in the circumferential direction to accommodate expansion and contraction.
The invention will be described in moxe S detail with reference to the accompanying drawings, in which Figure 1 is an isometric view of a commutator construction according to one form of the invention, Figure 2 is a side view of a single commutator segment positioned on the mounting cylinder Figures 3A and 3B are sectional views of two different forms of the invention taken generally along the plane indicated by 3-3 in Figure 2, with adjacent commutator segments added for ease of illustrating the invention, and Figures ~A and ~B are top views of adjacent commutator segments corres~onding respectively to the sectional views of Figures 3A and 3B.
Referring now to Figure 1, a commutator 10 is shown mounted on shaft 11 of a dynamoelectric machine (not shown). Bands 14, 15 and 16, of slightly resilient material, such as several layers of glass fiber embedded in an epoxy resin and cured, can be seen in Figure 1. Commutator segments 17 are mounted on cylinder 18, preferably a steel cylinder, which is fastened to shaft 11. A layer of insulating material 20 surrounds the cylinder 18 to insulate the segments 17 therefrom. The actual commutator segments 17A are spaced apart and a spring segment 17B is mounted between adjacent segments 17A and insulated therefrom ~y insulating strips 21 of mica. Risers 22 are brazed to or otherwise mounted in the ends of respective commutator segments 17A to serve as connectors to the winding of the dynamoelectric machine as is well known in the art.
, .
.
. . , . ~
~ ' ' ' ' ' :
Case 2596 It may not be necessary to have a spring segment 17s alternating with segments 17A as shown. In other words, a satisfactory degree of resilience might be achieved with a spring segmenl 17B placed after every two segments 17A, or in any olher predetermined arrangement provided sufficient circumferential force is provided to permit expansion and contraction.
Figure 2 shows the cy]Linder 18 in section with a commutator segment 17A mounted on it and insulated from it by insulating material 20. In Figure 2, three bands of glass fibers 14, 15 and 16 encircle the segments 17 to hold them in position. Flanges 23 are welded to the inner surface of cylinder 1~ at intervals.
Each flange 23 has a bolt receiving hole 24. An annular ring (not shown) may be mounted to shaft 11 (Figure 1) by heat shrinking or other means and bolts passed through holes in the annular ring and through holes 24 to mount the cylinder 18. Other ~orms of mounting may be suitable. The particular mounting means is not an essential feature of the invention. The riser 22 is shown mounted between bands 15 and 16.
Referring now to Figures 3A and 4~, adjacent commutator segments 17A are separated by spring segment 17B. Commutator segments 17~ and spring segments 17B may be made from copper or a copper alloy.
The spring segment 17B has a curvature which extends in the axial direction so that it engages the mica strips 21 on either side along axially extending lines.
The drawings are not to scale. The size of the segments 17B has been exaggerated for ease of explanation. The spring segment 17B needs to provide only a small deflection, perhaps of the order of 0.001 inch in a commutator having a diameter of between 1 and 3 feet.
Consequently~ the segments 17B may be of copper, treated to retain some resilience, having a thickness .
~ ~ . ' ' , ' , ' : , . .
i53 Case 2596 0.001 inch or slightly less and a curvature which provides perhaps 0.002 inch before compression.
Figures 3B and 4s sho~w a slightly different form of spring segment 17B ' where the spring segment 17B' is deformed in a radial direction at intervals to form a wave-like strip. Again the deflection required might be of the order of OoO01 inch so the uncompressed segment might have a dimension between the peaks on one side and the peaks on the other side of 0.002 inch.
An alternative form of construction uses a spring segment similar to segment 17B' but where the segment is composed of a series of separate curved pieces. In other words, referring to figure 4B, one curved piece would be equivalent approximately to that portion of 17B' which is between broken lines 30 and 31 and is designated 32. The segment 17B' would thus be made up of a series of curved pieces 32 placed side by side.
Speaking generally, with reference to Figures
This invention relates to an improved commutator construction.
In D.C. dynamoelectric machines, particularly in the medium and large sizes, it is important that there be no significant sparking where the brushes contact the segments of the commutator. This means that the surface of the commutator on which the brushes ride must ~e smooth and concentric with the axis of rotation of the commutator. The departure from concentricity or runout that can be tolerated may be as small as 0.002 inch, and depending on size and speed the relative displacement between segments that can be tolera-ted may be as small as 0.001 inch or smaller.
Thus the commutator must be made accurately and this 15 accuracy must be maintained. -To prevent small amounts of relative movement between adjacent segments, it is known to buila an arch force into the assembly. That is, the commutator segments and seasoned mica insulation which separates adjacent segments, form an arch. The arch is, of course, any portion of a cylindrical commutator assembly. Thexe are two arrangements which are commonly used to hold the segments of the commutator in position. These arrangements are sometimes referred to as the "cap and cone" construction and the "glass band" construction. The first arrangement, that is the : ~ ', : ' - . -., i.
~.l.g~i53 Case 2596 cap and cone, uses two spaced apart steel rings whichhave cone-shaped annular projections extending towards one another. The commutator segments have correspon-ding cone-shaped channels in opposite ends. The segments are mounted between the rings, using sheet insulation between the cap and the cone, and a system of bolts applies a force to the two rings tending to move them towards one another pressing the projections or caps into the channels or cones in the commutator segments. This fixes the segments in position with the conical surfaces providing a restraining force against radial movement.
When a machine having cap and cone construction is ope~ated, the temperature increases and the copper/
mica arch tends to expand more than the steel rings which support it. Large forces are created with the arch being under compression and the steel cap under tension. Concentricity is maintained within the desired limits because the steel rings are designed to provide sufficient restraint to the radial ~ovement of the copper and mica arch.
The second arrangement for holding the commutator segments in position is much simpler and less expensive. In this glass band construction the commutator segments are mounted over a steel cylinder, with insulation between the segments and the cylinder, and two or more bands of glass fibers are wound around the commutator segments and set in a suitable hardenable plastic material such as an epoxy resin. The bands have a degree of flexibility which permits the arch to expand slightly when the temperature rises. However, with this expansion there is a tendency for the copper/
mica arch to lose its close contact with the cylinder (that is with the insulation surroundin~ the cylinder) and it may deform or bulge in one area causing the ' :.
, :
- : : . , ~
Case 2596 runout to exceed permissible limits for that machine.
To overcome this problem and allow for limited expansionJ a commutator may be made with a slight clearance between the copper segments and the mica insulation which separates them. However the force of the ~rushes on the commutator during running of the machine tends to cause relative movement of the segments and may create such relative movement in the form of a wave-like surface. This may exceed the permissible tolerances for runout and relative displacement.
It appears it may have been the intention when glass band construction was first used, that the mica insulation between segments would provide some resilience to the arch so that the arch could expand and contract more than the steel cylinder on which it is mounted. The mica is, however, too rigid. Other materials, such as rubber coated mica, might provide sufficient resilience but rubber does not age well and will take a permanent set after a period of time at operating temperature.
The present invention is primarily concerned with glass band type construction and provides a spring force in the commutator arch which permits expansion of the arch while retaining a commutator structure with satisfactory runout and relative displacement of segments. The commutator construction of the inyention provides for a spring segment between adjacent copper or copper alloy commutator segments, insulated from the commutator segments by an insulating material such as mica. The spring segments are relatively thin, that is they do not occupy much space in tha circumferential direction, as the deflection required of each segment is small. The spring may be deformed in either the axial or radial direction.
. ,~, , ' , ~ ' d Case 2596 It is therefore a feature of the present invention to provide a spring force in the commutator arch of a glass band construction commutator to accommodate differential expansion.
Canadian Patent No. 54~ 041 - Zollner, issued June 4, 1957, describes a co~nutator construction where the commutator segments are of carbon. In order to ensure current transmission a:Long the length of the carbon segment, a strip of metal is placed beside the carbon segment. The strip of metal is soldered to, or fastened to, or pressed against the carbon segment at spaced points along its length to ensure good current transmission. Where the metal strip is not fastened to the carbon segment but is formed to press against the carbon segment at spaced points, it might provide some spring force, however according to the patent the metal strip must be flexible enough to avoid stressing the carbon segments and consequently would not provide sufficient spring force to stress the arch to allow for differential expansion. Thus, the purpose and properties of the metal strip are different from the spring segment of the present invention.
Carbon commutators have not become popular, perhaps because of the rapid wear.
Accordingly there is provided a commutator for a dynamoelectric machine, comprising a cylindrical commutator support for attaching to the shaft of a dynamoelectric machine, a plurality of commutator segments extending in a generally axial direction around said support and insulated therefrom by a layer of insulating material, a spring segment between predetermined adjacent commutator segments, and a strip of insulating material between each spring segment and at least one of the adjacent commutator segments, the spring segments being compressed between .
;53 Case 2596 adjacent commutator segments to provide a force in the circumferential direction to accommodate expansion and contraction.
The invention will be described in moxe S detail with reference to the accompanying drawings, in which Figure 1 is an isometric view of a commutator construction according to one form of the invention, Figure 2 is a side view of a single commutator segment positioned on the mounting cylinder Figures 3A and 3B are sectional views of two different forms of the invention taken generally along the plane indicated by 3-3 in Figure 2, with adjacent commutator segments added for ease of illustrating the invention, and Figures ~A and ~B are top views of adjacent commutator segments corres~onding respectively to the sectional views of Figures 3A and 3B.
Referring now to Figure 1, a commutator 10 is shown mounted on shaft 11 of a dynamoelectric machine (not shown). Bands 14, 15 and 16, of slightly resilient material, such as several layers of glass fiber embedded in an epoxy resin and cured, can be seen in Figure 1. Commutator segments 17 are mounted on cylinder 18, preferably a steel cylinder, which is fastened to shaft 11. A layer of insulating material 20 surrounds the cylinder 18 to insulate the segments 17 therefrom. The actual commutator segments 17A are spaced apart and a spring segment 17B is mounted between adjacent segments 17A and insulated therefrom ~y insulating strips 21 of mica. Risers 22 are brazed to or otherwise mounted in the ends of respective commutator segments 17A to serve as connectors to the winding of the dynamoelectric machine as is well known in the art.
, .
.
. . , . ~
~ ' ' ' ' ' :
Case 2596 It may not be necessary to have a spring segment 17s alternating with segments 17A as shown. In other words, a satisfactory degree of resilience might be achieved with a spring segmenl 17B placed after every two segments 17A, or in any olher predetermined arrangement provided sufficient circumferential force is provided to permit expansion and contraction.
Figure 2 shows the cy]Linder 18 in section with a commutator segment 17A mounted on it and insulated from it by insulating material 20. In Figure 2, three bands of glass fibers 14, 15 and 16 encircle the segments 17 to hold them in position. Flanges 23 are welded to the inner surface of cylinder 1~ at intervals.
Each flange 23 has a bolt receiving hole 24. An annular ring (not shown) may be mounted to shaft 11 (Figure 1) by heat shrinking or other means and bolts passed through holes in the annular ring and through holes 24 to mount the cylinder 18. Other ~orms of mounting may be suitable. The particular mounting means is not an essential feature of the invention. The riser 22 is shown mounted between bands 15 and 16.
Referring now to Figures 3A and 4~, adjacent commutator segments 17A are separated by spring segment 17B. Commutator segments 17~ and spring segments 17B may be made from copper or a copper alloy.
The spring segment 17B has a curvature which extends in the axial direction so that it engages the mica strips 21 on either side along axially extending lines.
The drawings are not to scale. The size of the segments 17B has been exaggerated for ease of explanation. The spring segment 17B needs to provide only a small deflection, perhaps of the order of 0.001 inch in a commutator having a diameter of between 1 and 3 feet.
Consequently~ the segments 17B may be of copper, treated to retain some resilience, having a thickness .
~ ~ . ' ' , ' , ' : , . .
i53 Case 2596 0.001 inch or slightly less and a curvature which provides perhaps 0.002 inch before compression.
Figures 3B and 4s sho~w a slightly different form of spring segment 17B ' where the spring segment 17B' is deformed in a radial direction at intervals to form a wave-like strip. Again the deflection required might be of the order of OoO01 inch so the uncompressed segment might have a dimension between the peaks on one side and the peaks on the other side of 0.002 inch.
An alternative form of construction uses a spring segment similar to segment 17B' but where the segment is composed of a series of separate curved pieces. In other words, referring to figure 4B, one curved piece would be equivalent approximately to that portion of 17B' which is between broken lines 30 and 31 and is designated 32. The segment 17B' would thus be made up of a series of curved pieces 32 placed side by side.
Speaking generally, with reference to Figures
2, 3 and 4, the commutator segments 17A are machined after temporary mounting with recesses or channels to receive bands 14, 15 and 16. It is convenient to have spring segments 17B extend only from band 14 to band 15 and this construction has provided satisfactory results. However, under certain circumstances it may be necessary to provide a short length of spring segment which extends axially between bands 15 and 16.
It may also be found to be desirable to place spacers 30 between segments 17A beneath bands 14, 15 and 16 to avoid minor distortion which might occur where there is no spring segment 17B. However, it has been found that in most instances this is unnecessary, perhaps because of the slight resiliency in the glass bands.
Various other shapes of longitudinally .. . . .
. . ~ .
:. . . ' . ' ' ' ' - ~: , ' Case 2596 extending spring segments might be used, for example, strips with longitudinally extending small ripples, and materials other than copp~r can be used as long as they provide a spring force.
' :
. ~
~: : -, - . ~ -. .
It may also be found to be desirable to place spacers 30 between segments 17A beneath bands 14, 15 and 16 to avoid minor distortion which might occur where there is no spring segment 17B. However, it has been found that in most instances this is unnecessary, perhaps because of the slight resiliency in the glass bands.
Various other shapes of longitudinally .. . . .
. . ~ .
:. . . ' . ' ' ' ' - ~: , ' Case 2596 extending spring segments might be used, for example, strips with longitudinally extending small ripples, and materials other than copp~r can be used as long as they provide a spring force.
' :
. ~
~: : -, - . ~ -. .
Claims (14)
1. A commutator for a dynamoelectric machine, comprising a cylindrical commutator support for attaching to the shaft of a dynamoelectric machine, a plurality of commutator segments extending in a generally axial direction around said support and insulated therefrom by a layer of insulating material, a spring segment between predetermined adjacent commutator segments, and a strip of insulating material between each spring segment and at least one of the adjacent commutator segments, the spring segments being compressed between said adjacent commutator segments to provide a force in the circumferential direction to accommodate expansion and contraction.
2. A commutator as defined in claim 1 in which the spring segment is a strip of material deformed about an axis extending in the axial direction to provide a slightly curved strip.
3. A commutator as defined in claim 1 in which the spring segment comprises strip material deformed about radially extending axes.
4. A commutator as defined in claim 1 in which the spring segment comprises a plurality of separate pieces each deformed about an axis extending radially and placed side by side between said adjacent commutator segments.
5. A commutator as defined in claim 1 in which the spring segment is a strip of material deformed at intervals along the strip about radially extending axes Case 2596 to provide a wave-like strip.
6. A commutator as defined in claim 1 in which a commutator segment and a spring segment alternate around the commutator.
7. A commutator as defined in claims 1, 2 or 3 in which said segments are of copper.
8. A commutator for a dynamoelectric machine, comprising a cylindrical commutator support for attaching to the shaft of a dynamoelectric machine a plurality of copper commutator segments extending in a generally axial direction about the periphery of said support and insulated therefrom by a layer of insulating material, a spring segment compressed between adjacent commutator segments providing a circumferentially directed force to the arc of the commutator, a strip of insulating material on either side of said spring segment insulating it from adjacent commutator segments, and at least two spaced apart bands of insulating material encircling said commutator segments to hold said commutator segments in position on said support.
9. A commutator as defined in claim 8 in which the spring segment is a strip of material having a length dimension several times greater than a width dimension and is deformed about its longitudinal axis to form a curved strip.
10. A commutator as defined in claim 8 in which the spring segment is a strip of material having a length dimension several times greater than a width dimension and is deformed laterally to provide a wave-like strip.
11. A commutator as defined in claim 8 in which the spring segment comprises a series of similar Case 2596 separate curved pieces placed side by side between said adjacent commutator segments with the axis of curvature extending in a radial direction.
12. A commutator as defined in claims 8, 9 and 11 in which the spring segments are basically of copper, treated to retain its resiliency.
13. A commutator as defined in claim 8 in which the strip of insulating material on either side of said spring segment is mica.
14. A commutator as defined in claim 8 in which said bands are formed of fibers of glass in a cured epoxy resin.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000330382A CA1119653A (en) | 1979-06-22 | 1979-06-22 | Commutator construction |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA000330382A CA1119653A (en) | 1979-06-22 | 1979-06-22 | Commutator construction |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1119653A true CA1119653A (en) | 1982-03-09 |
Family
ID=4114525
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000330382A Expired CA1119653A (en) | 1979-06-22 | 1979-06-22 | Commutator construction |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1119653A (en) |
-
1979
- 1979-06-22 CA CA000330382A patent/CA1119653A/en not_active Expired
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