Turning – Lathe – With program control
Reexamination Certificate
2001-02-20
2003-10-21
Wellington, A. L. (Department: 3722)
Turning
Lathe
With program control
C082S121000
Reexamination Certificate
active
06634264
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an indexing device provided in a machine tool. More particularly, the present invention relates to a turret tool rest capable of selecting a desired tool from a plurality of tools mounted at regular circumferential intervals and locating the selected tool at a machining-work position by the indexed rotation of the turret tool rest.
BACKGROUND ART
In a field of machine tools, it is well-known that a turret tool rest capable of mounting a number of tools is used for facilitating the automation of the machining work and an increase in the machining speed, as well as for meeting a multi-item low-volume production. For example, a turret tool rest used in an automatically operated lathe is constituted by a tool slide disposed on a lathe bed at a position opposed to a rotary spindle, a tool rest body provided on the tool slide to be movable along a given coordinate axis, and a turret supported for rotation on the tool rest body and capable of respectively mounting various tools, such as cutting tools or drills, at a plurality of angularly-indexed positions around a rotation axis. In this regard, the automatically operated lathe described herein means any turning machine tools, such as NC lathes, capable of carrying out an automatic machining or turning operation.
In the turret tool rest, after the indexing rotation of the turret is performed, it is necessary to firmly secure the turret at an indexed position on the tool rest body during the machining of a workpiece with a selected tool. Accordingly, a mutually engageable and disengageable pair of engaging elements are generally disposed between the tool rest body and the turret. By mutually engaging/disengaging (or clamping/unclamping) the pair of engaging elements, it is possible to allow the indexing rotation of the turret or to locate and secure the turret at a desired indexed position.
A coupling unit in the form of an intermeshable pair of coupling members like a claw-clutch mechanism, each having a number of claws on one axial end surface, has been known as an engaging unit formed from abovementioned pair of engaging elements. In this type of engaging unit, the clamping/unclamping operation is generally performed by linearly displacing one engaging element provided for the turret in an axial direction relative to the other engaging element provided for the tool rest body by an exclusive clamp/unclamp drive mechanism.
An example of a tool selection procedure is described below. First, after a machining work on a workpiece by one tool has completed, the tool rest body is moved together with the turret on the tool slide, so as to shift a tool backward from a machining-work position to a tool-exchangeable position. Then, the turret-side engaging element is moved to be disengaged from the tool rest body-side engaging element by the clamp/unclamp drive mechanism, and, in this condition, the turret is rotated by another rotation drive source to perform an indexing rotation, so as to select a desired tool. Next, the turret-side engaging element is engaged with the tool rest body-side engaging element by the operation of the clamp/unclamp drive mechanism, so as to securely hold the selected tool at an indexed position. In this condition, the tool rest body is moved together with the turret on the tool slide, so as to feed the tool from the tool-exchangeable position to the machining-work position.
An automatically operated lathe, such as an NC lathe, includes a plurality of drive sources for respectively driving different objectives, such as a drive source for rotating a spindle, respective axial drive sources for feeding a tool, a drive source for opening/closing a spindle chuck, and so on. For these drive sources, servomotors have been generally used, particularly in portions (such as a spindle or a tool-feed) requiring a high-speed and high-precision response. In recent years, servomotors also tend to be used in portions wherein hydraulic or pneumatic actuators have been conventionally used, such as the chuck opening/closing drive source or the turret rotation drive source in the turret tool rest described above, because of the advantages of environmental sanitation and operational reliability in the servomotors.
In the above-described clamp/unclamp drive mechanism for the turret tool rest, however, electric-motorization has been delayed and hydraulic or pneumatic actuators are still used in most cases, due to, e.g., the fact that a required operation is a simple one for merely slightly displacing one of engaging elements in an axial direction. The hydraulic or pneumatic actuators generally possess problems such as the deterioration of working environment due to noise or atmospheric pollution, the rise of equipment cost, the enlargement of machine size, low precision of response, and so on. Particularly, when a hydraulic cylinder is used as the clamp/unclamp drive mechanism, the operation speed easily varies due to the change in temperature of hydraulic fluid, so that the time required for clamping/unclamping the engaging elements fluctuates, which results in difficulties in the stable control of sequential turret-indexing operations. Also, since the hydraulic cylinder itself constitutes a considerable heat source and a thermal expansion of peripheral machine components is caused which results in difficulties in obtaining a stable machining accuracy. Therefore, the electric-motorization of the clamp/unclamp drive mechanism of the turret tool rest has been also desired.
On the other hand, in the turret tool rest with an electrically motorized drive source, a servomotor as a turret rotation drive source is provided on the tool rest body, and, in the case where not only stationary tools such as a cutting tool but also rotary tools such as a drill can be mounted, another servomotor is also provided on the tool rest body for the rotary tools. Moreover, if a further servomotor is provided as a clamp/unclamp drive source on the tool rest body in response to the demand for the electric-motorization of the clamp/unclamp drive mechanism, a weight of the tool rest body, as one of moving elements along a given coordinate axis on the lathe bed, unduly increases, which may result in the lowering of response accuracy, and may cause the problems of the enlargement of entire machine dimensions, the rise of production and operating cost, and so on.
DISCLOSURE OF THE INVENTION
Accordingly, an object of the present invention is to provide a turret tool rest in which the electrical motorization of a clamp/unclamp drive mechanism capable of securely holding and releasing a turret at an indexed position on a tool rest body can be performed without incorporating an additional motor, so that several effects, such as the mitigation of noise or atmospheric pollution, the saving of energy consumption, the improvement of response accuracy, the reduction of production and operating cost, and so on, can be obtained, and that the further reduction of dimensions of a machine tool and the further improvement of performance thereof can be facilitated.
To achieve the above object, the present invention provides a turret tool rest, comprising a base; a tool rest body movably provided on the base; a turret rotatably supported on the tool rest body, the turret permitting desired tools to be individually mounted at predetermined angularly-indexed positions; an electric motor for rotationally driving the turret; a clutch unit arranged between the turret and the electric motor, the clutch unit operatively connecting the turret with the electric motor in a releasable manner; a drive mechanism for operating the clutch unit; an engaging unit arranged between the tool rest body and the turret, the engaging unit engaging the turret with the tool rest body in a disengageable manner; and a power transmission device arranged between the electric motor and the engaging unit, the power transmission device transmitting an output of the electric motor to the engaging unit so as to operate the engaging unit; wherein, when the engaging uni
Emura Tamotsu
Takeuchi Yoji
Citizen Watch Co. Ltd.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Walsh Brian D.
Wellington A. L.
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