Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
2002-05-21
2004-03-09
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S732000, C029S825000, C029S827000, C310S071000
Reexamination Certificate
active
06701604
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to power tools and, more particularly, to a method for assembling and an electrical connector assembly for a power tool.
BACKGROUND OF THE INVENTION
A typical power tool includes a motor housing and an electric motor supportable by the motor housing and electrically connectable with a power source. The electric motor may include a field assembly, including one or more field windings, a rotatable armature supporting a commutator, a carbon brush for electrically engaging the commutator, and a switch for electrically connecting the components of the electric motor to the power source. In some power tools, the components of the electric motor are directly electrically wired to one another to provide a complete electrical circuit for the motor.
In some other power tools, the components of the electric motor include respective terminals and the motor also includes an electrical connection system electrically connecting the motor components. In such power tools, the electrical connection system includes separate contact strips which are separately mounted on the housing. Once mounted, the forward ends of the contact strips are engaged with the field terminals, and the rearward ends of the contact strips engage the brush terminals or the wiring harness for connection to the switch to provide a complete electrical circuit for the motor.
SUMMARY OF THE INVENTION
One independent problem with power tools having above-described directly-wired components is that direct wiring of the motor components during assembly of such power tools is time-consuming and labor-intensive, greatly increasing the cost and the complexity of the method and the machinery for assembling the power tools.
One independent problem with the power tool with the above-described electrical connection system including contact strips is that, while the contact strips improve the efficiency of assembly of the power tool, each of the separate contact strips must be accurately positioned and fixed to the housing so that the components of the motor can be electrically connected. If a contact strip is improperly positioned or improperly fixed to the housing, corrective action is required so that the motor components can be electrically connected to one another, reducing the efficiency of the assembly process.
Another independent problem with the power tool with the above-described electrical connection system is that the motor housing must be designed to fixably support and retain the contact strips in the required position. If the motor housing is improperly formed, the motor housing will not support the contact strips in the required location (for proper connection to the motor components) and, therefore, will not be useable.
Yet another independent problem with the above-described power tools is that, because the direct wires or the contact strips do not provide additional structural rigidity to the motor housing, the motor housing, which is typically formed of a moldable material, requires a greater amount of material and a more durable material, increasing the cost of the power tool.
Another independent problem with some of the above-described power tools is that the power tool cannot be configured to have different operating conditions, such as with or without a braking capability, without changing the wiring or the electrical connection system of the power tool.
The present invention provides a method for assembling and an electrical connector assembly for a power tool that alleviates one or more of the above-identified and other problems with the above-described power tools. In some aspects, the invention provides a one-piece trace or spider terminal member assembly which provides points of connection for the motor components, such as the field assembly, the brushes and the switch. To assemble the motor, the one-piece terminal member assembly is positioned in the motor housing. To mount the terminal member assembly, the terminal member assembly is preferably co-molded as a unit with the housing or, alternatively, may snap-fit into connectors formed on the housing. The terminal member assembly and the housing are then preferably punched or stamped at points to provide the necessary number of electrically separated contact elements to connect the components of the motor. For example, the female ends or terminals of the field assembly, the brushes and the switch are connected to the electrically separated contact elements to provide a suitable complete electrical circuit for the motor. A non-conducting plug may fill the openings created by punching or stamping. The plug also confirms that the openings were punched or stamped. Further, the plug provides a seal to prevent debris from entering the opening and effecting the electrical circuit of the motor.
More particularly, the invention provides a method for assembling a power tool, the power tool including a motor housing, and a motor supportable by the housing, the method comprising the acts of providing a terminal member assembly including a plurality of electrically separable contact elements, mounting the terminal member in the motor housing, electrically separating the plurality of electrically separable contact elements of the terminal member assembly from one another to provide a corresponding plurality of electrically separated contact elements, supporting the motor in the motor housing, and electrically connecting the plurality of electrically separated contact elements to the motor to provide a complete electrical circuit for the motor.
Preferably, the housing is formed of a molded material and the act of mounting the terminal member assembly includes molding the terminal member assembly as a unit with the motor housing. Also, the act of separating preferably includes creating an opening in the terminal member assembly between adjacent ones of the plurality of electrically separable contact elements to provide the plurality of electrically separated contact elements.
In addition, the act of creating an opening may preferably include punching an opening in the terminal member assembly between adjacent ones of the plurality of electrically separable contact elements to provide the plurality of electrically separated contact elements. Preferably, the act of punching provides a corresponding hole in the motor housing substantially aligned with the opening between adjacent ones of the plurality of electrically separated contact elements.
The method may further preferably comprise the act of positioning a non-conducting element in the opening between adjacent ones of the plurality of electrically separated contact elements and, preferably, through the corresponding hole in the motor housing. Also, the method may further preferably comprise the act of providing a separate motor housing cover having the non-conducting element mounted thereon, positioning the separate motor housing cover over the motor housing, and positioning the non-conducting element in the opening between adjacent ones of the plurality of electrically separated contact elements.
The motor may include a field having a plurality of field terminals, and each of the plurality of electrically separated contact elements may have at least a first contact. Preferably, the act of supporting the motor includes supporting the field in the motor housing, and the act of electrically connecting the plurality of electrically separated contact elements to the motor includes electrically connecting the first contact of a corresponding one of the plurality of electrically separated contact elements with one of the plurality of field terminals. Preferably, the act of supporting the field occurs substantially simultaneously with the act of electrically connecting the first contact of the corresponding one of the plurality of electrically separated contact elements with the one of the plurality of field terminals.
Also, the motor may include a switch having a switch terminal, and at least one of the plurality of electrically separated contact elements may have a first contact
Hessenberger Jeffrey C.
Zeiler Jeffrey M.
Arbes Carl J.
Michael & Best & Friedrich LLP
Milwaukee Electric Tool Corporation
Phan T. D.
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