Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1999-09-30
2001-09-25
Waks, Joseph (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S047000
Reexamination Certificate
active
06294857
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to electric power tools. More particularly, the present invention relates to a structure for attaching brush holders for holding brushes, such as carbon brushes, in predetermined positions of a housing and against a commutator motor of an electric power tool.
2. Description of the Related Art
In some electric power tools and other motor-driven appliances and devices to which the present invention is applicable, brush holders are attached to the housing with rivets or calking pieces provided on the brush holders so as to hold the brushes against the commutator of the motor of the tool. In another structure for attaching brush holders, brush holders are provided with barbed lugs for fitting into through-holes in the housing.
Such conventional structures, however, suffer from various shortcomings. Attachment of brush holders with rivets and calking pieces is time-consuming and thus reduces the efficiency at assembly sites. Moreover, as rivets must be provided as separate parts, they also raise the manufacturing cost of the entire devices. Although structures using barbed lugs require no separate parts, lugs often need to be fitted into the through-holes with jigs due to the difficulty in maintain close manufacturing tolerances.
Furthermore, brush holders are sometimes removed from electric power tools in order to recycle the housings. Such removal is troublesome if barbed lugs, rivets, or calking pieces are employed to secure the brush holders to the housing.
Various improved structures have been proposed to overcome the aforementioned shortcomings. For example, Japan Published Unexamined Utility Model Application No. 50-72901 discloses such a structure in which each of the two brush holders is set in a recess formed in a first housing portion and provisionally held in the recess with a L-shaped elastic member. According to this structure, the brush holders are secured by fitting a second housing portion to the first housing portion. Japan Published Unexamined Utility Model Application No. 7-27274 discloses another example, in which a pair of brush holders is received in a pair of grooves in a first housing portion, and a pair of ribs formed on the inner surface of a second housing portion is brought into contact with and secures the brush holders when the second housing portion is assembled to the housing portion. The first structure, however, still requires additional parts (the elastic members) in order to provisionally retain the brush holders in the recesses, whereas the brush holders of the second structure are not stably seated in the grooves or accurately positioned during the assembly thereof, thus affecting mounting or replacement of the brushes and connection and wiring of leads to the holders.
SUMMARY OF THE INVENTION
In view of the above-identified problems, an important object of the present invention is to provide a structure for attaching brush holders to an electric power tool without requiring any parts, such as rivets, calking pieces, or elastic members, in addition to the brush holders.
Another object of the present invention is to provide a structure for attaching brush holders to an electric power tool that securely and stably retains the brush holders even when the holders are provisionally retained in the tool.
Still another object of the present invention is to provide a structure that permits easy attachment of brush holders to and removal from an electric power tool.
The above objects and other related objects are realized by the invention, which provides a structure for attaching a brush holder in a predetermined position on a housing of a tool. The structure comprises: at least one positioning hole which has inner walls and is formed in the predetermined position in the housing; and at least one elastic strip protruding from the brush holder for insertion in the at least one positioning hole when the brush holder is attached to the predetermined position on the housing. The at least one elastic strip presses at least one of the inner walls of the positioning hole when the elastic strip is inserted in the positioning hole so as to removably attach the brush holder in the predetermined position.
According to one aspect of the present invention, the at least one elastic strip has a first end connected to the brush holder and a second free end which is folded back so as to have a tapering, V-shaped cross-section.
According to another aspect of the present invention, the brush holder includes an upper surface and two elastic strips which protrude in parallel to each other from bottom edges of the brush holder, with the free ends of the elastic strips folded back toward the upper surface of the brush holder.
According to still another aspect of the present invention, the structure can further comprises a pair of guide walls provided on the housing along the at least one positioning hole for guiding the folded elastic strips into the at least one positioning holes, thereby facilitating attachment of the brush holder to the predetermined position on the housing.
According to yet another aspect of the present invention, the housing is divided into first and second casing halves along a dividing plane intersecting the at least one positioning hole. Furthermore, the second casing half may include an elastic member that abuts the upper surface of the brush holder when the second casing half is assembled to the first casing half.
In accordance with another aspect of the present invention, the second casing half further includes a cut-out which exposes the brush holder when the brush holder and the second casing half are assembled so as to permit access to the brush holder.
In one practice, the second casing half further includes an outer cover detachably assembled to an outer surface of the second casing half so as to cover the cut-out.
In another practice, the elastic strip is a metal strip integrally formed with the brush holder and the elastic member is a cylindrical rubber pin provided on an inner surface of the second casing half.
Other general and more specific objects of the invention will in part be obvious and will in part be evident from the drawings and descriptions which follow.
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Foley Hoag & Eliot LLP
Makita Corporation
Waks Joseph
LandOfFree
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