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Title:
ELECTRIC MOTOR WITH ELONGATED PLASTIC ENDFRAME
Document Type and Number:
WIPO Patent Application WO/1995/012230
Kind Code:
A1
Abstract:
There is presented an electric motor having a drive shaft (10), an armature (14) and commutator assembly (12) fixed to the drive shaft (10), a metal housing (20) disposed around an armature portion of the assembly, and permanent magnets (22) disposed between the armature portion and the housing. An endframe (30) is fixed to the housing and has therein a journal (34) for retaining the drive shaft, brushes (48) in contact with the commutator portion of the assembly, and shunts (50) and terminals (52) connected to the brushes. The endframe extends axially of the motor so as to be disposed around the commutator portion, and such that an open end of the endframe is spaced from the shunts and from the commutator portion. The endframe is of a non-electrically-conductive, noise-absorbing plastic and serves to absorb noise generated by the commutator portion and to prevent shorts by having the shunts in a non-conducting housing.

Inventors:
REID DENNIS G
CLARKE MICHAEL T
Application Number:
PCT/US1994/012416
Publication Date:
May 04, 1995
Filing Date:
October 28, 1994
Export Citation:
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Assignee:
EATON STAMPING CO (US)
International Classes:
H02K5/02; H02K5/04; H02K5/24; H02K5/22; (IPC1-7): H01R43/00; H02K1/04; H02K5/14; H02K5/24; H02K13/00; H02K15/14
Foreign References:
US3760209A1973-09-18
US4303901A1981-12-01
US5006747A1991-04-09
US5004943A1991-04-02
US4922149A1990-05-01
US4897571A1990-01-30
US4677333A1987-06-30
US4355253A1982-10-19
US4293789A1981-10-06
US4209723A1980-06-24
Download PDF:
Claims:
What is claimed is:
1. In an electric motor wherein an armature and commutator assembly is surrounded by a shell housing, an improvement wherein a portion of said shell housing around an armature portion of said assembly is of metal and a portion of said shell housing around a commutator portion of said assembly is of noise absorbing plastic, said plastic portion of said shell housing extending from said commutator portion toward said armature portion such that said commutator portion is disposed fully within said plastic portion of said shell housing and is axially spaced from an open end of said plastic portion and thereby axially spaced from said metal portion of said shell housing.
2. An electric motor comprising an armature portion of an armature and commutator assembly covered by a metal shell, and a commutator portion of said assembly covered by a nonelectricallyconductive plastic endframe, said plastic endframe extending axially of said motor from a substantially closed end thereof a distance greater than a maximum reach of brush shunts housed in said endframe, such that said shunts are unable to reach said metal shell, thereby to prevent development of electrical shorts between said shunts and said metal shell.
3. An electric motor comprising: a drive shaft, an armature and commutator assembly fixed on said drive shaft, a metal housing disposed around an armature portion of said assembly, permanent magnet means disposed between said armature portion and said housing, and an elongated endframe fixed to said housing, said endframe having therein means for retaining said shaft, brush means in contact with a commutator portion of said assembly, and shunt and terminal means connected to said brush means, said endframe extending axially of the motor from a substantially closed end of the endframe so as to be disposed around said commutator portion, and such that an open end of said endframe is axially spaced from a maximum reach of said shunt means, said endframe being of nonelectricallyconductive, noiseabsorbing plastic.
4. The motor in accordance with claim 3 wherein said endframe extends axially from said closed end thereof beyond said commutator such that said commutator is spaced axially from said metal housing.
5. The motor in accordance with claim 4 wherein said endframe plastic is a nylon compound having glass and mineral content.
6. An endframe for an electric motor, said endframe having therein: means for retaining a drive shaft of said motor, a cylindricallyshaped central portion for retaining a commutator portion of said motor, brush tubes extending outwardly from said central portion, a brush disposed in each of said brush tubes, a spring disposed in each of said brush tubes for biasing said brush toward said central portion, a conductive wire connected at a first end thereof to each of said brushes, and a terminal fixed to a second end of each of said conductive wires, said endframe including a substantially closed end and an open end for connection to a housing of said motor, said endframe being of plastic material and comprising a substantially cylindricallyshaped shell, said shell extending from said closed end beyond said brushes such that about onethird of the length of said shell extends beyond said brushes.
7. The endframe in accordance with claim 6 wherein said endframe is of nonelectricallyconductive, noise absorbing plastic.
8. The endframe in accordance with claim 7 wherein said open end of said endframe is spaced beyond a maximum reach of said conductive wires.
Description:
ELECTRIC MOTOR WITH ELONGATED PLASTIC ENDFRAME

Background of the Invention

1 . Field of the Invention

The invention relates to electric motors and is directed more particularly

to an electric motor having an elongated plastic endframe extending around the

commutator and around the brushes and shunts of the motor.

2. Description of the Prior Art

It is common to provide an electric motor having a steel shell surrounding an armature and commutator assembly. The provision of a plastic endframe is known, the endframe serving as a support for journal and bearing means for a

drive shaft, and for brushes, shunts and terminals. The steel shell is typically

joined to the endframe, surrounds the commutator, and is in close proximity to

the brushes and shunts.

Because of the closeness of the shunts and steel shell, there are recurring

problems with the shunts contacting the steel shell, causing a short in the

motor internal electrical circuit. Further, the steel shell surrounding the commutator and brush interface tends to transmit the noise generated at the

interface.

Noise and recurring short problems are unacceptable where quiet and

reliable operation is required. For example, in D.C. motors used in automobiles

for operation of power seats, it is desirable that the motors operate silently and

necessary that the motors be reliable.

Accordingly, there exists a need for a motor having the commutator

housed in a noise-absorbing material adapted to absorb noise created on the

inside of the motor by the interaction of the commutator and brushes. Further,

there exists a need for separating the metal shell from the brush shunts in the

endframe, to prevent contact between the shunts and the steel frame and

consequent shorting out of the internal motor system.

Summary of the Invention

It is, therefore, an object of the invention to provide a motor having a

steel shell and a plastic endframe with the shell and endframe arranged and

configured to provide the plastic endframe around the commutator to absorb

noise generated by the commutator and brush interface. The material of the

endframe is a noise-absorbing plastic.

A further object of the invention is to provide such shell and endframe

arrangement and configuration as will space the brush shunts at a sufficient

distance from the steel shell as to render virtually impossible contact between

the shunts and the shell. In addition to being noise-absorbing, the material of

the endframe is a non-electrically-conductive plastic, such that contact between

the shunts and the endframe does not result in an electrical short.

With the above and other objects in view, as will hereinafter appear, a

feature of the present invention is the provision of an electric motor comprising

a drive shaft, an armature and commutator assembly fixed on the drive shaft, a

metal housing disposed around an armature portion of the armature and

commutator assembly, and permanent magnet means disposed between the

armature portion and the housing. An endframe is fixed to the housing, the

endframe having therein means for retaining the drive shaft, brush means in

contact with a commutator portion of the armature and commutator assembly,

and shunt and terminal means connected to the brush means. The endframe

extends axially of the motor from a substantially closed end of the endframe so

as to be disposed around the commutator portion, and such that an open end of

the endframe is spaced from the commutator and the shunt means and brushes.

The endframe is of a non-electrically-conductive, noise-absorbing plastic.

In accordance with a further feature of the invention, there is provided an

endframe for an electric motor, the endframe having therein means for retaining

a drive shaft of the motor, a cylindrically-shaped central portion for retaining a

commutator portion of the motor, brush tubes extending outwardly from the central portion, a brush disposed in each of the brush tubes, a spring disposed

in each of the brush tubes for biasing the brush toward the central portion, a

conductive wire connected at a first end thereof to each of the brushes, and a

terminal fixed to a second end of each of the conductive wires. The endframe

includes a substantially closed end, and an open end for connection to a

housing of the motor. The endframe is of plastic material and comprises a

substantially cylindrically-shaped shell, the shell extending from the closed end

well beyond the brushes, such that about one-third of the length of the shell

extends beyond the brushes.

The above and other features of the invention, including various novel details of construction and combinations of parts, will now be more particularly

described with reference to the accompanying drawings and pointed out in the

claims. It will be understood that the particular devices embodying the

invention are shown by way of illustration only and not as limitations of the

invention. The principles and features of this invention may be employed in

various and numerous embodiments without departing from the scope of the

invention.

Brief Description of the Drawings

Reference is made to the accompanying drawings in which is shown an

illustrative embodiment of the invention, from which its novel features and

advantages will be apparent.

In the drawings:

Fig. 1 is a partly side elevational, partly sectional, view of one form of

motor illustrative of an embodiment of the invention; and

Fig. 2 is an end view of an endframe portion of the motor shown in Fig.

1 , taken from the open end of the endframe.

Description of the Preferred Embodiment

Referring to the drawings, it will be seen that the illustrative motor

includes a drive shaft 10. Fixed to the drive shaft 1 0 is an armature and

commutator assembly 1 2, including an armature 14, a commutator 1 6, and

appropriate windings 1 8.

A metal housing shell 20 is disposed around the armature 14. The

housing 20 may be of steel. Permanent magnets 22 are disposed between the

housing shell 20 and the armature 14 and are secured to the housing shell.

An endframe 30 is fixed to the housing shell 20. The endframe 30 has

formed in a substantially closed end 32 a journal 34 for retaining a bearing 36 which, in turn, supports the drive shaft 10. Disposed in the endframe 30 is a

brush card 40 which comprises a cylindrically-shaped central portion 42

configured to retain the commutator 16. Extending radially from the central

portion 42 are opposed brush tubes 44 (Fig. 2). The central portion 42 and the

brush tubes 44 are of plastic and may be formed integrally. Each of the brush

tubes 44 has disposed therein a coil spring 46 and a brush 48, the spring 46

biasing the brush 48 into engagement with the commutator 1 6. Each brush 48

has attached thereto a conductive wire lead, or shunt, 50, the other end of

which is connected to a terminal 52 fixed in a terminal housing portion 54.

Referring to Fig. 1 , it will be seen that the endframe 30 extends axially of

the motor a sufficient distance to provide a plastic shell housing 56, comprising

a side wall portion 58 of the endframe 30, around the commutator 1 6. The

wall portion 58 of the endframe 30 extends towards the armature 14 such that

the commutator 1 6 is disposed fully within the plastic endframe 30 and is axially spaced from an open end 60 of the endframe 30. In a preferred

embodiment, about one-third or more of the endframe wall 58 extends beyond

the brushes and commutator. Thus, the commutator 1 6 is axially spaced from

the metal shell 20, and the noise-absorbing plastic extends beyond either end of

the commutator to absorb the noise generated by the commutator-brush

interface. Further, the distance by which the elongated endframe 30 extends

away from the closed end of the endframe places the metal shell 20 beyond the

maximum reach of the shunts 50 in the endframe. Thus, the shunts are unable

to reach the metal shell to cause a short. The endframe plastic is non-

electrically conductive, rendering any contact between the shunts 50 and the endframe 30 harmless.

A plastic material which has been found suitable for the endframe 30 is a

nylon plastic having about 20% glass and 20% mineral content, by weight, the

compound being manufactured and sold by E.I. Dupont under the name "Rynite

940. " The plastic is less dense than steel and serves as a good sound-

absorbing medium.

There is thus provided an electric motor having facility for quiet running

and for operation devoid of the threat of shorts between the shunts and the

metal shell of the motor.

It is to be understood that the present invention is by no means limited to

the particular construction herein disclosed and/or shown in the drawings, but

also comprises any modifications or equivalents within the scope of the claims.

For example, while the illustrative embodiment includes a discrete brush card

mounted in the endframe, in many instances the brush card structure is molded

integrally with the endframe.

Having thus described our invention, what we claim as new and desire to

secure by Letters Patent of the United States is:




 
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