Numerically controlled machine tool

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Patent

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Details

364184, 318565, G05B 1900, G05B 2300

Patent

active

047259590

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to improvement in or relating to a numerically controlled machine tool, and more particularly to a numerically controlled machine tool which enables the current position of its movable machine part to be correctly recognized on the side of a numerical controller at all times.


BACKGROUND ART

In recent years there has come into use an arrangement in which a counter is provided on the side of a machine tool for counting output detection signals from a position sensor and the current position (the coordinate value) of a movable machine part (a motor, for example) is obtained on the basis of the count value of the counter on the side of a numerical controller. The provision of such a counter on the side of the machine tool precludes the necessity of performing a zero return upon each turning-ON of the power source on the side of the numerical controller, but involves the necessity of providing a signal line for transmitting the count value of the counter to the numerical controller, posing a problem of increasing the number of signal lines between the machine tool and the numerical controller.
As a solution to this problem there has been proposed an arrangement in which a switching circuit actuable for selecting the detection signal of the position sensor and the count value of the counter is provided in the machine tool and the output of the switching circuit is transmitted to the numerical controller. With the provision of such a switching circuit, it is possible to transfer the detection signal of the position sensor and the count value of the counter through one signal line. However, when the machine tool is activated by some cause during the transfer of the count value of the counter to the numerical controller, there will be an error between the actual current position of the movable machine part and the current position of the movable machine part recognized on the side of the numerical controller.


DISCLOSURE OF THE INVENTION

The present invention offers a solution to the abovementioned problems, and has for its object to reduce the number of signal lines between the numerical controller and the machine tool and to enable the current position of the movable machine part to be correctly recognized on the side of the numerical controller at all times.
To obviate the above-described defects of the prior art, according to the present invention, in a numerically controlled machine tool which has, on the side of the machine tool, position sensing means for producing a detection signal upon each movement of the movable machine part by a predetermined amount and serial data generating means for generating serial data and in which the detection signal from the position sensor and the serial data are transmitted via a signal provided line to the numerical controller, there are provided, on the side of the machine tool, follow-up means for reproducing the detection signal from the position sensor during the transfer of the serial data, switching means for selectively sending the output signal of the follow-up means, the detection signal from the position sensor, and the serial data from the serial data generating means to the numerical controller via the same signal line, and control means for controlling the switching means to send the output signal of the follow-up means to the numerical controller immediately after the transfer of the serial data.
The number of signal lines between the machine tool and the numerical controller can be decreased because there is provided on the side of the machine tool the switching means for selectively transmitting the output signal of the follow-up means, the detection signal from the position sensor and the serial data from the serial data generating means to the numerical controller via the same signal line. Furthermore, since the follow-up means is provided for reproducing the detection signal output from the position sensor during the transfer of the serial data, even if the movable machine part should move during the tra

REFERENCES:
patent: 4549271 (1985-10-01), Nozawa et al.
patent: 4580085 (1986-04-01), Eto et al.
patent: 4602196 (1986-07-01), Matsui
patent: 4638421 (1987-01-01), Kimizuka et al.

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