CA2070658C - Electrical commutator and method for making same - Google Patents
Electrical commutator and method for making sameInfo
- Publication number
- CA2070658C CA2070658C CA002070658A CA2070658A CA2070658C CA 2070658 C CA2070658 C CA 2070658C CA 002070658 A CA002070658 A CA 002070658A CA 2070658 A CA2070658 A CA 2070658A CA 2070658 C CA2070658 C CA 2070658C
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- Canada
- Prior art keywords
- commutator
- rings
- segments
- recess
- segment
- 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 - Fee Related
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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
-
- 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
- H01R39/08—Slip-rings
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01R—ELECTRICALLY-CONDUCTIVE CONNECTIONS; STRUCTURAL ASSOCIATIONS OF A PLURALITY OF MUTUALLY-INSULATED ELECTRICAL CONNECTING ELEMENTS; COUPLING DEVICES; CURRENT COLLECTORS
- H01R43/00—Apparatus or processes specially adapted for manufacturing, assembling, maintaining, or repairing of line connectors or current collectors or for joining electric conductors
- H01R43/06—Manufacture of commutators
-
- 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
- H01R39/14—Fastenings of commutators or slip-rings to shafts
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Motor Or Generator Current Collectors (AREA)
- Manufacturing Of Electrical Connectors (AREA)
Abstract
A commutator (10) for a motor is disclosed which includes a plurality of commutator segments (12) arranged in a cylindric array (14) such that the array has a cylindrical outer periphery (20) and two axial ends. An annular recess (26, 28) is formed adja-cent each end (22, 24) of the array so that a portion of each commutator segment (12) forms a part of the radially inner wall of each recess. Two or more rings (34, 36) constructed of an insulating material are provided and one or more rings are press fit into each recess so that the rings (34, 36) exert a radially inward force on the commutator segment (12). The anchoring portions of the commutator segments (12) are then encapsulated with a settable and electrically insulating material (40), such as phenolic. Upon hardening and curing, the phenolic secures the commutator segments (12) together. At the same time, the radially inward force exerted by the rings (34, 36) on the commutator segments (12) serves to stabilize the commutator segments (12) against movement relative to each other during high speed rotation of the commutator (10). A method for manufacturing the commutator is also dis-closed.
Description
2(~7Q65~ .
EL~CTRICAL corlrluTAToR AND ~IET~IOD FOR MAKING SA~IE
Background of the Invention I. Field of the Invention The present invention relates to a novel electrical commutator for electric motors as well as a method for manufacturing the same.
II. Description of the Prior Art There are many types of previously known electrical commutators which are used in electric motors. These previously known electrical commutators typically comprise a plurality of commutator segments which are arranged in a cylindric array so that the outer periphery of the cylindric array is cylindrical in shape. These segments are constructed of an electrically conductive material, such as copper, and are either separated from each other by an insulating material, such as mica, or subsequently machined to electrically insulate these segments from each other.
Since the commutator segments are physically separated from each other, it is necessary to secure the commutator segments together during rotation of the commutator. In some instances, the cylindric array is molded with a settahle material, such as a phenolic which, upon setting, rigidifies and holds these segments together. Such a previously known commutator construction, however, has not proven wholly satisfactory at high speed operation of the commutator.
In order to maintain stability of the commutator segments during high speed rotation, many of the previously known commutators have included an annular recess in one or both ends of the commutator.
A metal ring is placed into each annular recess and is simultaneously electrically isolated from the commutator segments. Thereafter, the commutator ~f 2070 65~
segments are molded with a settable materlal along wlth the metal relnforclng rlng. The purpose of the relnforclng rlng ln this deslgn ls to strengthen the settable materlal so that lt wlll have sufflclent strength to reslst fracture at the maxlmum rotatlonal speed of the commutator.
One dlsadvantage of thls prevlously known commutator constructlon, however, ls that, at hlgh speed rotatlon of the commutator, the centrlfugal force exerted on the commutator segments caused the commutator segments to lncur small relatlve movement wlth respect to each other. Thls relatlve movement ls caused ln part to the shrlnkage of the moldlng materlal away from the anchorlng portlon of the commutator segments durlng the settlng process. Consequently, the outer cyllndrlcal surface of the commutator ls relatlvely unstable and the commutator segments move relatlve to each other.
Relatlve movement of the commutator segments at hlgh speed rotatlon of the commutator dlsadvantageously creates sparklng between the brushes used wlth the commutator and the outer cyllndrlcal surface of the commutator. Such sparklng rapldly erodes the brushes due to the electrlcal dlscharge machlnlng caused by thls sparklng.
Summary of the Present Inventlon The present lnventlon provldes a commutator whlch stablllzes the commutator segments agalnst movement wlth respect to each other at hlgh rotatlonal speeds thereby overcomlng the above mentloned dlsadvantages of the prevlously known devlces.
The present lnventlon provldes a commutator for a motor comprlslng: a plurallty of commutator segments each ~.
~ 68572-362 commutator segment havlng an lnner perlphery and two substantlally planar sldes, sald sldes lylng ln respectlve planes whlch lntersect a predetermlned dlstance from sald lnner perlphery of sald commutator segment, sald commutator segments belng posltloned slde by slde so that sald commutator segments form an annular cyllndrlc array, sald segments belng constructed of an electrlcally conductlve materlal, means for electrlcally lnsulatlng each commutator segment from lts ad~acent commutator segment, sald cyllndrlc array havlng a cyllndrlcal outer perlphery, an lnner perlphery formed by the lnner perlpherles of sald commutator segments, two axlal ends, and an annular recess formed ad~acent each end so that a portlon of each commutator segment forms a part of a radlally lnner wall of each recess, means for generating a force normal to each planar slde of each commutator segment, sald forces belng offset by forces from the ad~acent commutator segments, sald force generatlng means comprlslngs at least two rlngs, at least one rlng belng assoclated wlth one recess and belng constructed of an electrlcal lnsulatlng materlal, each at least one rlng havlng an lnner dlameter less than the lnner dlameter of lts assoclated recess, sald rlngs belng posltloned lnto thelr assoclated recesses so that sald rlngs exert a radlally lnward force on sald commutator segments whlch ls transformed to sald normal forces to thereby stablllze sald segments agalnst relatlve rotatlon durlng rotatlon of sald commutator, and means for securlng sald commutator segments together.
From another aspect, the lnventlon provldes a method of manufacturlng a commutator for a motor comprlslng the steps s~ 3 -of: arranging a plurallty of commutator segments ln a cyllndrlc array, sald segments belng constructed of an electrlcally conductlve materlal, sald cyllndrlc array havlng a cyllndrlcal outer perlphery, an lnner perlphery, two axlal ends, an annular recess formed ad~acent each end so that a portlon of each segment forms a part of a radlally lnner wall of each recess, press flttlng a palr of rings lnto sald recesses, each rlng belng assoclated wlth one recess end and belng constructed of an electrlcal lnsulatlng materlal, each rlng havlng an lnner dlameter less than the lnner dlameter of lts assoclated recess and an outer dlameter less than the outer dlameter of lts assoclated recess, sald rlngs belng posltloned lnto thelr assoclated recesses so that sald rlngs exert a radlally lnward force on sald commutator segments whlch ls transformed to normal forces to thereby stablllze sald segments agalnst relatlve rotatlon durlng rotatlon of sald commutator and securlng sald commutator segments together.
In operatlon, the radlally lnward force exerted by the rlngs offsets the centrlfugal force of 3a-,~.~
R~ 68572-362 WO9l/08601 PCT/US90/07140 2~65~ -4-the commutator segment during high speed rotation. In doing so, the rings stabilize the commutator segments against relative movement or deflection with respect to each other during high speed rotation. This in turn minimizes electrical discharge machining (ED~I) of the motor brushes.
A method for constructing the commutator is also disclosed.
Brief Description of the Drawing A better understanding of the present invention will be had upon reference to the following detailed description, when read in conjunction with the accompanying drawing, wherein like reference characters refer to like parts throughout the several views, and in which:
FIG. 1 is an end view illustrating a first preferred embodiment of the present invention;
FIG. 2 is an exploded view taken substantially along line 2-2 in FIG. 1;
FIG. 3 is an end view similar to FIG. 1 but with additional parts;
FIG. 4 is a sectional view similar to FIG. 2 but showing the preferred embodiment of the present invention at a further step of manufacturing;
FIG. 5 is an exploded view illustrating a second preferred embodiment of the present invention;
FIG. 6 is a longitudinal sectional view illustrating the embodiment of FIG. 5 and taken substantially along line 6-6 in FIG. 7; and FIG. 7 is an elevational view illustrating the second preferred embodiment of the present invention.
2~70658 Detalled Descriptlon of Preferred Embodlments of the Present Inventlon With reference flrst to FIGS. 1 and 2, a preferred embodlment of the commutator 10 of the present lnvéntlon ls thereshown and comprlses a plurallty of commutator segments 12 arranged slde-by-slde ln a cyllndrlc array 14. Although any conventlonal means can be used to form the cyllndrlc array 14 from the commutator segments 12, as best shown ln FIGS. 1 and 2, preferably the commutator segments 12 are assembled wlthln a dle 16 havlng a cyllndrlcal throughbore 18.
The commutator segments 12 are constructed of an electrlcally conductlve materlal, such as copper. However, as ls well known, the commutator segments 12 must be electrlcally lnsulated from each other ln the finlshed commutator. Any conventlonal means (not shown) can be used to accompllsh thls, such as lnsulatlng strlps between the segments 12, machlnlng the cyllndrlc array 14 after completlon of assembly to create alr spaces between the segments 12, or other conventlonal means.
Each commutator segment 12 lncludes two substantlally planar sldes and each slde of the commutator segment lles ln a plane whlch lntersects the axls or center of the cyllndrlc array. Thus the commutator segments are "ple shaped" and the lnner perlphery of each commutator segment ls spaced radlally outwardly from the center of the cyllndrlc array 14 so that the cyllndrlc array 14 ls annular ln shape.
As best shown ln FIG. 2, the cyllndrlc array 14 has a cyllndrlcal outer perlphery 20 and two axlal ends 22 and 24.
Annular recesses 26 and 28 are respectlvely formed ln the axial ends 22 and 24 of the cyllndrlc array 14. Furthermore, as best shown ln FIG. 2, a portion 30 and 32 of each commutator segment 12 respectlvely forms a portion of the lnner radlal walls of the annular recesses 26 and 28.
Wlth reference now especlally to FIG. 3, the commutator 10 of the present lnventlon further lncludes a palr of rlngs 34 and 36 so that one rlng 34 ls assoclated wlth the annular recess 26 whlle, slmllarly, the second rlng 36 ls assoclated wlth the other annular recess 28. The rlngs 34 and 36 are constructed of an electrical lnsulating material, such as glass flber relnforced resln. Other types of electrlcal insulating materials may, however, alternatlvely be used.
The rlngs 34 and 36 are dlmensloned so that both the lnslde and outslde dlameters of the rlngs 34 and 36 are smaller than the outslde and lnslde dlameters of thelr assoclated annular recesses 26 and 28. The rings 34 and 36 are then press fit into their associated recesses 26 and 28, as illustrated diagrammatically for the ring 36 ln FIG. 2.
Once the rlngs 34 and 36 are press flt lnto thelr assoclated recesses 26 and 28, an lnterference flt ls created between the portlons 30 and 32 of the commutator segments 12 and rlngs 34 and 36. Conversely, the outer perlphery of the rlngs 34 and 36 are spaced radlally lnwardly from the outslde radial wall of the recesses 26 and 28. Consequently, with the rlngs 34 and 36 press flt lnto thelr recelvlng recesses 26 and 28, the rlngs 34 and 36 exert a radially inward force on the commutator segments 12 ln addltlon to any radlal force exerted by the dle 16 on the commutator segments 12. Slnce the cyllndrlc array 14 ls annular ln shape, the radlally lnward 2û~06S8 force imparted by the rlngs 34 and 36 ls transformed or translated lnto forces normal to the plane of each slde of each commutator segment 12. These normal forces, ln turn, are offset by normal forces from the sldes of ad~acent commutator segments of equal magnltude but opposlte in dlrectlon.
Furthermore, slnce the plane of each slde of each commutator segment 12 lntersects the center of the cyllndrlc array, the normal forces from the sldes of each commutator segment, when added, comblned lnto a net radlally lnward force.
The amount of lnterference between the rlngs 34 and 36 and thelr assoclated recesses 26 and 28 wlll vary dependlng ln large part upon the dlameter of the commutator. For example, an lnterference of between .015 and .020 lnches has proven sufflclent for a one lnch dlameter commutator. Larger lnterferences would be used for a larger dlameter commutator and vlce versa.
Wlth reference now to FIG. 4, the cyllndrlc array 14 as well as the rlngs 34 and 36 are molded wlth a flowable settable materlal 40 whlch ls also an electrlcal lnsulator.
Any conventlonal materlal 40 can be used, such as a phenollc, epoxy, melamlne or polyester, whlch becomes rlgld upon settlng. In the well known fashlon, the materlal 40, once lt becomes rlgld, secures the commutator segments 12 together and forms the commutator. After the materlal 40 has cooled or otherwlse set, the commutator ls then e~ected from the dle 16.
Followlng constructlon of the commutator descrlbed above, the materlal 40 serves to hold the commutator segments 12 together agalnst centrlfugal force which occurs durlng hlgh speed rotatlon of the commutator. Addltlonally, however, .~i ~r 68572-362 after formation of the commutator, the rlngs 34 and 36 continue to exert a radlally lnward force on the commutator segments 12. Thls radlally lnward force serves to stablllze the commutator segments agalnst relatlve movement wlth respect to each other durlng hlgh speed rotatlon of the commutator.
Such stablllzatlon of the commutator segments 12 mlnlmlzes any electrlcal dlscharge machlning of the brushes that would otherwlse occur due to such relatlve movement between the commutator segment 14.
Wlth reference now to FIGS. 5-7, a modlflcatlon to the present lnventlon ls thereshown ln whlch the commutator segments 12', when arranged ln the cyllndrlc array 14', lnclude an enlarged dlameter bore 50 ad~acent the end 24. The annular recess 28' ls ad~acent to but spaced radlally lnwardly from the end 24 of the cyllndrlc array 14. In addltlon, a dovetall-shaped notch portlon 52 ls also formed wlthln the cyllndrlc array 14' by the commutator segments 12' between the annular recess 28' and the axlal end 24 of the cyllndrlc array 14'.
As best shown ln FIG. 5, the commutator segments 12' are arranged as descrlbed before ln the dle 16 whlle each lnsulatlng stablllzlng rlng 34 and 36 ls press flt lnto lts assoclated recess 26 and 28' respectlvely. An lnsulatlng materlal 54 ls then ln~ected so that lt covers the segments 12' and, upon hardenlng, secures the commutator segments 12' together.
As best shown ln FIG. 6, the lnsulatlng materlal 54 completely fllls the notch portlon 52 of the cyllndrlc array 14' thereby strengthenlng the commutator. Slmultaneously, the ~Yh 68572-362 ' ~FJ"~
lnsulatlng materlal 54 forms a cylindrical recess 56 in the end 24 of the commutator. Thls recess 56 ls dlmensloned to recelve a portlon of the motor assembly, such as a bearlng assembly, thereby shortenlng the effectlve axlal length of the commutator. Thls construction ls thus partlcularly deslrable for appllcatlons ln whlch the axlal length of the commutator ls crltlcal.
Although the commutator has been descrlbed as havlng one rlng 34 or 36 ln thelr respective recesses 26 and 28, ln practlce one or more rlngs are posltloned ln each recess. For example, in some appllcatlons two or even more rlngs are posltloned ln a slngle recess so that the rlngs are axlally allgned wlth each other.
Slmllarly, although the commutator segments have been descrlbed as separate elements prior to the moldlng operatlon, in some appllcatlons the segments are of a one piece constructlon prlor to the moldlng process. In this case, the commutator ls machlned after moldlng ln order to electrlcally lsolate the segments from each other. In any event, as used ln thls patent, the term "segments" shall lnclude commutator segments whlch are both dlscreet from each other prlor to moldlng and whlch are lntegral wlth each -8a-_g _ `20~0658 other prior to molding and subsequently machined to electrically isolate them from each other.
From the foregoing, it can be seen tha~ the present invention provides a simple and yet effective means for stabilizing the commutator ~gments against relative movement during high spee~ ~otation.
naving described my ~nvention, however, many modifications theret~ ~ill become apparent to those skilled in the art to which is pertains without deviatio~ ~rom the s2irit of the invention a~ ~e~ed by t~e s~e ~ the appended claims.
I claim:
EL~CTRICAL corlrluTAToR AND ~IET~IOD FOR MAKING SA~IE
Background of the Invention I. Field of the Invention The present invention relates to a novel electrical commutator for electric motors as well as a method for manufacturing the same.
II. Description of the Prior Art There are many types of previously known electrical commutators which are used in electric motors. These previously known electrical commutators typically comprise a plurality of commutator segments which are arranged in a cylindric array so that the outer periphery of the cylindric array is cylindrical in shape. These segments are constructed of an electrically conductive material, such as copper, and are either separated from each other by an insulating material, such as mica, or subsequently machined to electrically insulate these segments from each other.
Since the commutator segments are physically separated from each other, it is necessary to secure the commutator segments together during rotation of the commutator. In some instances, the cylindric array is molded with a settahle material, such as a phenolic which, upon setting, rigidifies and holds these segments together. Such a previously known commutator construction, however, has not proven wholly satisfactory at high speed operation of the commutator.
In order to maintain stability of the commutator segments during high speed rotation, many of the previously known commutators have included an annular recess in one or both ends of the commutator.
A metal ring is placed into each annular recess and is simultaneously electrically isolated from the commutator segments. Thereafter, the commutator ~f 2070 65~
segments are molded with a settable materlal along wlth the metal relnforclng rlng. The purpose of the relnforclng rlng ln this deslgn ls to strengthen the settable materlal so that lt wlll have sufflclent strength to reslst fracture at the maxlmum rotatlonal speed of the commutator.
One dlsadvantage of thls prevlously known commutator constructlon, however, ls that, at hlgh speed rotatlon of the commutator, the centrlfugal force exerted on the commutator segments caused the commutator segments to lncur small relatlve movement wlth respect to each other. Thls relatlve movement ls caused ln part to the shrlnkage of the moldlng materlal away from the anchorlng portlon of the commutator segments durlng the settlng process. Consequently, the outer cyllndrlcal surface of the commutator ls relatlvely unstable and the commutator segments move relatlve to each other.
Relatlve movement of the commutator segments at hlgh speed rotatlon of the commutator dlsadvantageously creates sparklng between the brushes used wlth the commutator and the outer cyllndrlcal surface of the commutator. Such sparklng rapldly erodes the brushes due to the electrlcal dlscharge machlnlng caused by thls sparklng.
Summary of the Present Inventlon The present lnventlon provldes a commutator whlch stablllzes the commutator segments agalnst movement wlth respect to each other at hlgh rotatlonal speeds thereby overcomlng the above mentloned dlsadvantages of the prevlously known devlces.
The present lnventlon provldes a commutator for a motor comprlslng: a plurallty of commutator segments each ~.
~ 68572-362 commutator segment havlng an lnner perlphery and two substantlally planar sldes, sald sldes lylng ln respectlve planes whlch lntersect a predetermlned dlstance from sald lnner perlphery of sald commutator segment, sald commutator segments belng posltloned slde by slde so that sald commutator segments form an annular cyllndrlc array, sald segments belng constructed of an electrlcally conductlve materlal, means for electrlcally lnsulatlng each commutator segment from lts ad~acent commutator segment, sald cyllndrlc array havlng a cyllndrlcal outer perlphery, an lnner perlphery formed by the lnner perlpherles of sald commutator segments, two axlal ends, and an annular recess formed ad~acent each end so that a portlon of each commutator segment forms a part of a radlally lnner wall of each recess, means for generating a force normal to each planar slde of each commutator segment, sald forces belng offset by forces from the ad~acent commutator segments, sald force generatlng means comprlslngs at least two rlngs, at least one rlng belng assoclated wlth one recess and belng constructed of an electrlcal lnsulatlng materlal, each at least one rlng havlng an lnner dlameter less than the lnner dlameter of lts assoclated recess, sald rlngs belng posltloned lnto thelr assoclated recesses so that sald rlngs exert a radlally lnward force on sald commutator segments whlch ls transformed to sald normal forces to thereby stablllze sald segments agalnst relatlve rotatlon durlng rotatlon of sald commutator, and means for securlng sald commutator segments together.
From another aspect, the lnventlon provldes a method of manufacturlng a commutator for a motor comprlslng the steps s~ 3 -of: arranging a plurallty of commutator segments ln a cyllndrlc array, sald segments belng constructed of an electrlcally conductlve materlal, sald cyllndrlc array havlng a cyllndrlcal outer perlphery, an lnner perlphery, two axlal ends, an annular recess formed ad~acent each end so that a portlon of each segment forms a part of a radlally lnner wall of each recess, press flttlng a palr of rings lnto sald recesses, each rlng belng assoclated wlth one recess end and belng constructed of an electrlcal lnsulatlng materlal, each rlng havlng an lnner dlameter less than the lnner dlameter of lts assoclated recess and an outer dlameter less than the outer dlameter of lts assoclated recess, sald rlngs belng posltloned lnto thelr assoclated recesses so that sald rlngs exert a radlally lnward force on sald commutator segments whlch ls transformed to normal forces to thereby stablllze sald segments agalnst relatlve rotatlon durlng rotatlon of sald commutator and securlng sald commutator segments together.
In operatlon, the radlally lnward force exerted by the rlngs offsets the centrlfugal force of 3a-,~.~
R~ 68572-362 WO9l/08601 PCT/US90/07140 2~65~ -4-the commutator segment during high speed rotation. In doing so, the rings stabilize the commutator segments against relative movement or deflection with respect to each other during high speed rotation. This in turn minimizes electrical discharge machining (ED~I) of the motor brushes.
A method for constructing the commutator is also disclosed.
Brief Description of the Drawing A better understanding of the present invention will be had upon reference to the following detailed description, when read in conjunction with the accompanying drawing, wherein like reference characters refer to like parts throughout the several views, and in which:
FIG. 1 is an end view illustrating a first preferred embodiment of the present invention;
FIG. 2 is an exploded view taken substantially along line 2-2 in FIG. 1;
FIG. 3 is an end view similar to FIG. 1 but with additional parts;
FIG. 4 is a sectional view similar to FIG. 2 but showing the preferred embodiment of the present invention at a further step of manufacturing;
FIG. 5 is an exploded view illustrating a second preferred embodiment of the present invention;
FIG. 6 is a longitudinal sectional view illustrating the embodiment of FIG. 5 and taken substantially along line 6-6 in FIG. 7; and FIG. 7 is an elevational view illustrating the second preferred embodiment of the present invention.
2~70658 Detalled Descriptlon of Preferred Embodlments of the Present Inventlon With reference flrst to FIGS. 1 and 2, a preferred embodlment of the commutator 10 of the present lnvéntlon ls thereshown and comprlses a plurallty of commutator segments 12 arranged slde-by-slde ln a cyllndrlc array 14. Although any conventlonal means can be used to form the cyllndrlc array 14 from the commutator segments 12, as best shown ln FIGS. 1 and 2, preferably the commutator segments 12 are assembled wlthln a dle 16 havlng a cyllndrlcal throughbore 18.
The commutator segments 12 are constructed of an electrlcally conductlve materlal, such as copper. However, as ls well known, the commutator segments 12 must be electrlcally lnsulated from each other ln the finlshed commutator. Any conventlonal means (not shown) can be used to accompllsh thls, such as lnsulatlng strlps between the segments 12, machlnlng the cyllndrlc array 14 after completlon of assembly to create alr spaces between the segments 12, or other conventlonal means.
Each commutator segment 12 lncludes two substantlally planar sldes and each slde of the commutator segment lles ln a plane whlch lntersects the axls or center of the cyllndrlc array. Thus the commutator segments are "ple shaped" and the lnner perlphery of each commutator segment ls spaced radlally outwardly from the center of the cyllndrlc array 14 so that the cyllndrlc array 14 ls annular ln shape.
As best shown ln FIG. 2, the cyllndrlc array 14 has a cyllndrlcal outer perlphery 20 and two axlal ends 22 and 24.
Annular recesses 26 and 28 are respectlvely formed ln the axial ends 22 and 24 of the cyllndrlc array 14. Furthermore, as best shown ln FIG. 2, a portion 30 and 32 of each commutator segment 12 respectlvely forms a portion of the lnner radlal walls of the annular recesses 26 and 28.
Wlth reference now especlally to FIG. 3, the commutator 10 of the present lnventlon further lncludes a palr of rlngs 34 and 36 so that one rlng 34 ls assoclated wlth the annular recess 26 whlle, slmllarly, the second rlng 36 ls assoclated wlth the other annular recess 28. The rlngs 34 and 36 are constructed of an electrical lnsulating material, such as glass flber relnforced resln. Other types of electrlcal insulating materials may, however, alternatlvely be used.
The rlngs 34 and 36 are dlmensloned so that both the lnslde and outslde dlameters of the rlngs 34 and 36 are smaller than the outslde and lnslde dlameters of thelr assoclated annular recesses 26 and 28. The rings 34 and 36 are then press fit into their associated recesses 26 and 28, as illustrated diagrammatically for the ring 36 ln FIG. 2.
Once the rlngs 34 and 36 are press flt lnto thelr assoclated recesses 26 and 28, an lnterference flt ls created between the portlons 30 and 32 of the commutator segments 12 and rlngs 34 and 36. Conversely, the outer perlphery of the rlngs 34 and 36 are spaced radlally lnwardly from the outslde radial wall of the recesses 26 and 28. Consequently, with the rlngs 34 and 36 press flt lnto thelr recelvlng recesses 26 and 28, the rlngs 34 and 36 exert a radially inward force on the commutator segments 12 ln addltlon to any radlal force exerted by the dle 16 on the commutator segments 12. Slnce the cyllndrlc array 14 ls annular ln shape, the radlally lnward 2û~06S8 force imparted by the rlngs 34 and 36 ls transformed or translated lnto forces normal to the plane of each slde of each commutator segment 12. These normal forces, ln turn, are offset by normal forces from the sldes of ad~acent commutator segments of equal magnltude but opposlte in dlrectlon.
Furthermore, slnce the plane of each slde of each commutator segment 12 lntersects the center of the cyllndrlc array, the normal forces from the sldes of each commutator segment, when added, comblned lnto a net radlally lnward force.
The amount of lnterference between the rlngs 34 and 36 and thelr assoclated recesses 26 and 28 wlll vary dependlng ln large part upon the dlameter of the commutator. For example, an lnterference of between .015 and .020 lnches has proven sufflclent for a one lnch dlameter commutator. Larger lnterferences would be used for a larger dlameter commutator and vlce versa.
Wlth reference now to FIG. 4, the cyllndrlc array 14 as well as the rlngs 34 and 36 are molded wlth a flowable settable materlal 40 whlch ls also an electrlcal lnsulator.
Any conventlonal materlal 40 can be used, such as a phenollc, epoxy, melamlne or polyester, whlch becomes rlgld upon settlng. In the well known fashlon, the materlal 40, once lt becomes rlgld, secures the commutator segments 12 together and forms the commutator. After the materlal 40 has cooled or otherwlse set, the commutator ls then e~ected from the dle 16.
Followlng constructlon of the commutator descrlbed above, the materlal 40 serves to hold the commutator segments 12 together agalnst centrlfugal force which occurs durlng hlgh speed rotatlon of the commutator. Addltlonally, however, .~i ~r 68572-362 after formation of the commutator, the rlngs 34 and 36 continue to exert a radlally lnward force on the commutator segments 12. Thls radlally lnward force serves to stablllze the commutator segments agalnst relatlve movement wlth respect to each other durlng hlgh speed rotatlon of the commutator.
Such stablllzatlon of the commutator segments 12 mlnlmlzes any electrlcal dlscharge machlning of the brushes that would otherwlse occur due to such relatlve movement between the commutator segment 14.
Wlth reference now to FIGS. 5-7, a modlflcatlon to the present lnventlon ls thereshown ln whlch the commutator segments 12', when arranged ln the cyllndrlc array 14', lnclude an enlarged dlameter bore 50 ad~acent the end 24. The annular recess 28' ls ad~acent to but spaced radlally lnwardly from the end 24 of the cyllndrlc array 14. In addltlon, a dovetall-shaped notch portlon 52 ls also formed wlthln the cyllndrlc array 14' by the commutator segments 12' between the annular recess 28' and the axlal end 24 of the cyllndrlc array 14'.
As best shown ln FIG. 5, the commutator segments 12' are arranged as descrlbed before ln the dle 16 whlle each lnsulatlng stablllzlng rlng 34 and 36 ls press flt lnto lts assoclated recess 26 and 28' respectlvely. An lnsulatlng materlal 54 ls then ln~ected so that lt covers the segments 12' and, upon hardenlng, secures the commutator segments 12' together.
As best shown ln FIG. 6, the lnsulatlng materlal 54 completely fllls the notch portlon 52 of the cyllndrlc array 14' thereby strengthenlng the commutator. Slmultaneously, the ~Yh 68572-362 ' ~FJ"~
lnsulatlng materlal 54 forms a cylindrical recess 56 in the end 24 of the commutator. Thls recess 56 ls dlmensloned to recelve a portlon of the motor assembly, such as a bearlng assembly, thereby shortenlng the effectlve axlal length of the commutator. Thls construction ls thus partlcularly deslrable for appllcatlons ln whlch the axlal length of the commutator ls crltlcal.
Although the commutator has been descrlbed as havlng one rlng 34 or 36 ln thelr respective recesses 26 and 28, ln practlce one or more rlngs are posltloned ln each recess. For example, in some appllcatlons two or even more rlngs are posltloned ln a slngle recess so that the rlngs are axlally allgned wlth each other.
Slmllarly, although the commutator segments have been descrlbed as separate elements prior to the moldlng operatlon, in some appllcatlons the segments are of a one piece constructlon prlor to the moldlng process. In this case, the commutator ls machlned after moldlng ln order to electrlcally lsolate the segments from each other. In any event, as used ln thls patent, the term "segments" shall lnclude commutator segments whlch are both dlscreet from each other prlor to moldlng and whlch are lntegral wlth each -8a-_g _ `20~0658 other prior to molding and subsequently machined to electrically isolate them from each other.
From the foregoing, it can be seen tha~ the present invention provides a simple and yet effective means for stabilizing the commutator ~gments against relative movement during high spee~ ~otation.
naving described my ~nvention, however, many modifications theret~ ~ill become apparent to those skilled in the art to which is pertains without deviatio~ ~rom the s2irit of the invention a~ ~e~ed by t~e s~e ~ the appended claims.
I claim:
Claims (18)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A commutator for a motor comprising:
a plurality of commutator segments each commutator segment having an inner periphery and two substantially planar sides, said sides lying in respective planes which intersect a predetermined distance from said inner periphery of said commutator segment, said commutator segments being positioned side by side so that said commutator segments form an annular cylindric array, said segments being constructed of an electrically conductive material, means for electrically insulating each commutator segment from its adjacent commutator segment, said cylindric array having a cylindrical outer periphery, an inner periphery formed by the inner peripheries of said commutator segments, two axial ends, and an annular recess formed adjacent each end so that a portion of each commutator segment forms a part of a radially inner wall of each recess, means for generating a force normal to each planar side of each commutator segment, said forces being offset by forces from the adjacent commutator segments, said force generating means comprising:
at least two rings, at least one ring being associated with one recess and being constructed of an electrical insulating material, each at least one ring having an inner diameter less than the inner diameter of its associated recess, said rings being positioned into their associated recesses so that said rings exert a radially inward force on said commutator segments which is transformed to said normal forces to thereby stabilize said segments against relative rotation during rotation of said commutator, and means for securing said commutator segments together.
a plurality of commutator segments each commutator segment having an inner periphery and two substantially planar sides, said sides lying in respective planes which intersect a predetermined distance from said inner periphery of said commutator segment, said commutator segments being positioned side by side so that said commutator segments form an annular cylindric array, said segments being constructed of an electrically conductive material, means for electrically insulating each commutator segment from its adjacent commutator segment, said cylindric array having a cylindrical outer periphery, an inner periphery formed by the inner peripheries of said commutator segments, two axial ends, and an annular recess formed adjacent each end so that a portion of each commutator segment forms a part of a radially inner wall of each recess, means for generating a force normal to each planar side of each commutator segment, said forces being offset by forces from the adjacent commutator segments, said force generating means comprising:
at least two rings, at least one ring being associated with one recess and being constructed of an electrical insulating material, each at least one ring having an inner diameter less than the inner diameter of its associated recess, said rings being positioned into their associated recesses so that said rings exert a radially inward force on said commutator segments which is transformed to said normal forces to thereby stabilize said segments against relative rotation during rotation of said commutator, and means for securing said commutator segments together.
2. The invention as defined in claim 1 wherein said rings are constructed of glass fibers.
3. The invention as defined in claim 2 wherein said rings each include a resin binder.
4. The invention as defined in claim 1, 2 or 3 wherein said securing means comprises a settable material in a liquid form which encapsulates a portion of each segment and which becomes rigid upon setting.
5. The invention as defined in claim 4 wherein said settable material is a phenolic resin.
6. The invention as defined in claim 4 wherein said settable material is an epoxy.
7. The invention as defined in claim 4 wherein said settable material is a polyester.
8. The invention as defined in claim 4 wherein said settable material is a melamine.
9. The invention as defined in any one of claims 1 to 3, or 5 to 8 wherein said rings are press fit into their associated recesses.
10. The invention as defined in any one of claims 1 to 3 or 5 to 8 wherein at least one annular recess is spaced inwardly from its adjacent axial end, and wherein said cylindric array includes an annular notch portion between said last mentioned recess and axial end, said notch portion being filled with said settable material which rigidifies said commutator.
11. A method of manufacturing a commutator for a motor comprising the steps of:
arranging a plurality of commutator segments in a cylindric array, said segments being constructed of an electrically conductive material, said cylindric array having a cylindrical outer periphery, an inner periphery, two axial ends, an annular recess formed adjacent each end so that a portion of each segment forms a part of a radially inner wall of each recess, press fitting a pair of rings into said recesses, each ring being associated with one recess end and being constructed of an electrical insulating material, each ring having an inner diameter less than the inner diameter of its associated recess and an outer diameter less than the outer diameter of its associated recess, said rings being positioned into their associated recesses so that said rings exert a radially inward force on said commutator segments which is transformed to normal forces to thereby stabilize said segments against relative rotation during rotation of said commutator and securing said commutator segments together.
arranging a plurality of commutator segments in a cylindric array, said segments being constructed of an electrically conductive material, said cylindric array having a cylindrical outer periphery, an inner periphery, two axial ends, an annular recess formed adjacent each end so that a portion of each segment forms a part of a radially inner wall of each recess, press fitting a pair of rings into said recesses, each ring being associated with one recess end and being constructed of an electrical insulating material, each ring having an inner diameter less than the inner diameter of its associated recess and an outer diameter less than the outer diameter of its associated recess, said rings being positioned into their associated recesses so that said rings exert a radially inward force on said commutator segments which is transformed to normal forces to thereby stabilize said segments against relative rotation during rotation of said commutator and securing said commutator segments together.
12. The invention as defined in claim 11 wherein said rings are constructed of glass fibers.
13. The invention as defined in claim 12 wherein said rings each include a resin binder.
14. The invention as defined in claim 12 wherein said rings each include an epoxy binder.
15. The invention as defined in claim 12 wherein said rings each include a polyester binder.
16. The invention as defined in claim 12 wherein said rings each include a melamine binder.
17. The invention as defined in any one of claims 11 to 16 wherein said securing step comprises flowing a settable material in a liquid form so that said material encapsulates a portion of each segment allowing said material to set and rigidify.
18. The invention as defined in claim 17 wherein said material is a phenolic resin.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US44609089A | 1989-12-05 | 1989-12-05 | |
| US446,090 | 1989-12-05 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2070658A1 CA2070658A1 (en) | 1991-06-06 |
| CA2070658C true CA2070658C (en) | 1996-06-04 |
Family
ID=23771285
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002070658A Expired - Fee Related CA2070658C (en) | 1989-12-05 | 1990-12-05 | Electrical commutator and method for making same |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0504294A4 (en) |
| JP (1) | JPH05502326A (en) |
| KR (1) | KR920704383A (en) |
| CA (1) | CA2070658C (en) |
| FI (1) | FI922600A7 (en) |
| WO (1) | WO1991008601A1 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE19956512A1 (en) * | 1999-11-25 | 2001-06-21 | Bosch Gmbh Robert | Commutator for an electric rotary machine |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2671865A (en) * | 1951-04-17 | 1954-03-09 | Nippert Electric Products Comp | Electrical collector ring assembly |
| DE1056256B (en) * | 1956-03-26 | 1959-04-30 | Bisterfeld & Stolting | Device for the manufacture of collectors for electrical machines |
| DE1275193B (en) * | 1963-10-15 | 1968-08-14 | Siemens Ag | Process for manufacturing a commutator for electrical machines |
| FR1451412A (en) * | 1965-07-08 | 1966-01-07 | Advanced training in rotating electrical appliance collectors | |
| JPS58139656A (en) * | 1982-02-12 | 1983-08-19 | Mitsubishi Electric Corp | Manufacture of commutator |
| DE3714098A1 (en) * | 1987-04-28 | 1988-11-10 | Kautt & Bux Kg | COMMUTATOR FOR MACHINES SMALL TO MEDIUM SIZE AND METHOD FOR THE PRODUCTION THEREOF |
-
1990
- 1990-12-05 JP JP3501957A patent/JPH05502326A/en active Pending
- 1990-12-05 EP EP19910901443 patent/EP0504294A4/en not_active Ceased
- 1990-12-05 WO PCT/US1990/007140 patent/WO1991008601A1/en not_active Application Discontinuation
- 1990-12-05 KR KR1019920701325A patent/KR920704383A/en not_active Withdrawn
- 1990-12-05 FI FI922600A patent/FI922600A7/en unknown
- 1990-12-05 CA CA002070658A patent/CA2070658C/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH05502326A (en) | 1993-04-22 |
| WO1991008601A1 (en) | 1991-06-13 |
| FI922600L (en) | 1992-06-05 |
| KR920704383A (en) | 1992-12-19 |
| EP0504294A4 (en) | 1993-06-30 |
| CA2070658A1 (en) | 1991-06-06 |
| FI922600A0 (en) | 1992-06-05 |
| EP0504294A1 (en) | 1992-09-23 |
| FI922600A7 (en) | 1992-12-31 |
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| Date | Code | Title | Description |
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| EEER | Examination request | ||
| MKLA | Lapsed |