Electrical generator or motor structure – Dynamoelectric – Reciprocating
Reexamination Certificate
1999-11-18
2001-07-10
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Reciprocating
C310S047000
Reexamination Certificate
active
06259175
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to linear actuators that are adapted to cause linear reciprocating movement of a workpiece along a desired path. In particular, this invention relates to an improved structure for such a linear actuator that is relatively compact in size, inexpensive in construction, and yet which is capable of handling relatively heavy loads.
A linear actuator is a device which is used to cause linear movement, typically reciprocating linear movement, of a workpiece along a desired path of movement. A typical linear actuator includes an electric motor having a rotatable output shaft. The output shaft of the electric motor is connected through a gear train to a nut and lead screw mechanism. Rotation of the output shaft of the electric motor causes corresponding rotation of the lead screw. The nut has an opening formed therethrough having an internal thread. The lead screw extends through the opening and has an external thread formed which cooperates with the internal thread formed on the nut. The nut is mounted on the lead screw in such a manner as to be restrained from rotating with the lead screw when the lead screw rotates. As a result, rotation of the lead screw causes linear movement of the nut axially along the lead screw. The direction of such axial movement of the nut (and the workpiece connected thereto) is dependent upon the direction of rotation of the lead screw.
Linear actuators are widely used in a variety of applications ranging from small to heavy loads. To accommodate heavy loads, known linear actuator structures have been formed from relatively large and heavy metallic components. Consequently, linear actuator structures currently in use are relatively heavy and expensive. Thus, it would be desirable to provide an improved linear actuator structure which is relatively lightweight and inexpensive to produce, and yet which is capable of handling heavy loads.
SUMMARY OF THE INVENTION
This invention relates to an improved structure for a linear actuator including a hollow housing that protectively encloses most of the components thereof to prevent the entry of dirt, water, and other contaminants from the environment. The housing of the linear actuator is formed from a first portion and a second portion that are secured together to form a hollow enclosure. The mating edges of the first and second portions of the housing can be formed in having a conventional tongue-and-groove structure and is preferably sealed to prevent the entry of dirt, water, and other contaminants within the housing. The first and second portions of the housing may initially be formed having an elongated tube portion of predetermined length. Depending upon the specific application for the linear actuator, the first and second portions can be cut to desired shorter lengths prior to assembly of the various components of the linear actuator. The first portion of the housing is formed to support all of the components of the linear actuator therein, while the second portion of the housing functions to retain such components in the first portion of the housing. After the assembly of the first and second portions of the housing, an end cap is secured to the end of the elongated tube portion to close the housing. The linear actuator includes a motor that operates through a clutch assembly to selectively rotate a screw. The clutch assembly limits the amount of torque that can be transmitted from the motor to the screw assembly. A nut is mounted on the screw assembly for linear movement in response to rotation of the screw assembly. An extension tube is crimped onto the nut for effecting linear movement of a workpiece. The structure of the nut is designed to facilitate an improved crimping connection between the nut and the extension tube. A dynamic braking circuit is provided to minimize coasting movement of the nut and the extension tube after motor has been turned off.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.
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Alfano Don C.
Andrews Ronald D.
Hallet Joel M.
Newport Samuel O.
Plunkett Larry E.
Dana Corporation
Jones Judson H.
MacMillan Sobanski & Todd LLC
Ramirez Nestor
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