Electrical generator or motor structure – Dynamoelectric – Linear
Reexamination Certificate
2000-09-29
2002-08-13
Ramirez, Nestor (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Linear
C310S020000
Reexamination Certificate
active
06433447
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a linear/rotary actuator, and more particularly to a linear/rotary actuator for actuating a machine or an equipment such as an arm of a robot, a nozzle for a winding machine or the like which carries out both linear motion and rotary motion.
Driving of a machine or an equipment such as, for example, an arm of a robot, a nozzle of a winding machine or the like often requires an actuator which is constructed so as to carry out linear motion and rotary motion not only individually (linear/rotary uniaxial motion) but concurrently (linear/rotary biaxial motion). Actuators for such biaxial motion include two types of actuators. One of them is a linear/rotary actuator of the type that simply an actuator for linear motion and that for rotary motion are combined with each other. More particularly, the actuator is so constructed that a rotary driving motor and a linear driving motor are independently arranged so as to transmit power through a complicated transmission mechanism to a single output shaft to carry out rotary/linear biaxial motion. The other actuator is a linear/rotary actuator of the type that a rotary driving motor and a linear driving motor are linearly arranged so as to directly carry out either rotary driving of an output shaft or linear driving thereof without using any complicated transmission mechanism. The actuator of the latter type is disclosed in, for example, Japanese Patent Application Laid-Open Publication No. 296308/1993, wherein two motors linearly arranged in juxtaposition to each other so as to define an axis of the actuator by cooperation with each other permit a single output shaft to carry out linear/rotary biaxial motion. Both former and latter linear/rotary actuators are disclosed in Japanese Patent,Application Laid-Open Publication No. 292343/1994.
The linear/rotary actuator disclosed in Japanese Patent Application Laid-Open Publication No. 292343/1994 is constructed in such a manner that a single output shaft is formed with both a ball screw and a spline. The ball screw and spline are driven either through a transmission mechanism or directly by means of both a rotary driving motor and a linear driving motor. Unfortunately, such construction of the linear/rotary actuator disclosed causes a problem that the output shaft carries out linear motion with rotation of a rotor of the rotary driving motor when a rotor of the linear driving motor is kept interrupted during rotary motion. In order to solve the problem, it is required to control the linear driving motor in coordination with the rotary driving motor during rotation thereof. This renders control of both rotary and linear driving motors highly troublesome and complicated and leads to both a failure in control and misregistration in control.
Also, the above-described latter linear/rotary actuator disclosed in Japanese Patent Application Laid-Open Publication No. 296308/1993 is so constructed that the single output shaft described above is adapted to carry out both rotary motion and linear motion and formed with a ball screw and a spline. The ball screw is threadedly engaged with a nut driven for rotation through the linear driving motor and the spline is linearly movably fitted in a groove of a shaft driven for rotation through the rotary driving motor. Driving of the linear driving motor rotates the nut, leading to linear motion of the output shaft, whereas driving of the rotary driving motor leads to rotation of the output shaft through the shaft. Such construction of the linear/rotary actuator permits it to be relatively simplified in structure and reduced in whole size. However, the linear/rotary actuator causes linear motion and rotary motion to be mechanically synchronized with each other, to thereby fail to individually carry out linear motion and rotary motion. For example, it fails in execution of only rotary motion, because the ball screw is rotated relatively to the nut, to thereby fail to rotate the output shaft while holding it against linear motion. Likewise, it fails to concurrently carry out both linear motion and rotary motion because it ensures linear motion in only one direction but causes a reduction in speed of linear motion in the other direction or fails in linear motion in the other direction. Such a restriction fails to permit the linear/rotary actuator to satisfactorily exhibit general-purpose properties.
In addition, the conventional linear/rotary actuator fails to optionally and positively carry out linear motion and rotary motion, leading to a failure to permit so-called box motion (linear motion, rotation, linear motion and rotation) as required in operation of a nozzle of a winding machine to be repeatedly executed at an increased speed.
SUMMARY OF THE INVENTION
The present invention has been made in view of the foregoing disadvantage of the prior art.
Accordingly, it is an object of the present invention to provide. a linear/rotary actuator which is capable of simply and positively attaining linear motion and rotary motion either concurrently or individually while arranging a rotary driving motor and a linear driving motor in a manner to be coaxial with each other.
It is another object of the present invention to provide a linear/rotary actuator which is capable of being constructed into a simplified and compact structure.
The present invention relates to an improvement in a linear/rotary actuator including a linear motor which is described in U.S. Pat. No. 6,081,051 (U.S. Ser. No. 09/212,030) assigned to the assignee, the disclosure of which is hereby incorporated by reference herein. Thus, in accordance with the present invention, a linear/rotary actuator is provided. The linear/rotary actuator includes a linear motor including a hollow linear shaft acting as a movable element and an output shaft formed on forward and rearward portions thereof with forward and rearward spline sections each having a predetermined length, respectively. The output shaft has an intermediate portion on which the forward and rearward spline sections are not formed. The intermediate portion of the output shaft is rotatably inserted through the linear shaft by means of an intermediate bearing structure. The linear/rotary actuator also includes a nut fitted on the forward spline section of the output shaft, a rotary driving motor for rotating the nut either directly or through a transmission mechanism, to thereby rotate the output shaft, and a rearward bearing structure including a fixed section having the rearward spline section fixed thereto. The rearward bearing structure supports the rearward spline section so as to permit sliding of the rearward spline section in an axial direction of the actuator and rotation of the output shaft. Arrangement of the rearward bearing structure permits the output shaft to be supported in a dual-support manner, to thereby significantly reduce generation of vibration. In order to rotate the output shaft through driving of the rotary driving motor, the output shaft is provided thereon with the front and rear spline sections and the nut fitted on the forward spline section is directly rotated, so that the output shaft may be rotated through the rotary driving motor. Alternatively, the nut may be rotated through a transmission mechanism to drive the output shaft through the rotary driving motor.
The term “spline section” referred to herein means a mechanism or structure which permits movement of a shaft in an axial direction thereof. The forward spline section described above is fitted thereon with a nut called a spline nut. The forward spline section keeps the shaft from being rotated when the spline nut is kept locked or fixed. When the nut is rotated due to application of force for rotation thereto while being kept unfixed, the forward spline section functions to transmit the force to the shaft. The rearward spline section formed on a rearward portion of the output shaft does not have any nut for transmission of force for rotation fitted thereon. The rearward spline section is fixed to the fixed sectio
Kitazawa Kazuyuki
Takeuchi Yutaka
Jones Judson H.
Ramirez Nestor
Rankin, Hill Porter & Clark LLP
Sanyo Denki Co. Ltd.
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