Numerical control device including a thin type display unit and

Details Numerical control device including a thin type display unit and Numerical control device including a thin type display unit and

1997-02-14

1999-08-17

Grant, William

Boots, shoes, and leggings

36447401, G06F 1900

Patent

active

059402920

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a numerical control device, and in particular, to a type of numerical control device (hereinafter referred to as a CNC device) incorporating a small-sized computer.
2. Description of the Related Art
A display/operation unit in a machine tool including a CNC device is mounted on a machine operation panel disposed at the front of the machine, for the convenience of an operator's monitoring and operation. But, a CNC controller and a servo amplifier are mounted on a heavy-electrical panel of the machine, since they can not be located on any specific place and also their external dimensions are relatively large. Thus, the CNC controller is connected to the display/operation unit through a cable. A CRT display or a liquid crystal display (hereinafter referred to as LCD) is used as a display for the CNC display/operation unit. A disadvantage of the CRT display is that it occupies a large installation space due to its large depth, whereas the LCD can be made more compact due to its smaller depth.
In the case where a CRT display is used, it does not matter if a CNC controller and a CRT display are connected directly to each other by means of a long cable. By contrast, in the case of a LCD, it is impossible to directly connect a CNC controller and a LCD with a long cable, and a synchronizing circuit with respect to a liquid crystal control signal is indispensable, thereby giving rise to a problem of an increase in cost.
Signals for controlling a CRT display by a CNC controller may be a horizontal synchronizing signal, a vertical synchronizing signal, red, green and blue color signals, etc. The color signals are analog signals, and a brightness of the color signal is determined by a level (voltage level) of each color data. Thus, a slight change of the level during signal transmission would not affect the brightness of color signal that much. Further, if time lag of the color signal happens, as far as it is small, change in color is negligible and the color difference is hardly recognized by the human eye. Therefore, the color signal has a large allowable range with respect to the change in its level and time lag. Thus, in the case where the CNC controller and the CRT display are connected through a cable for transmitting an image control signal such as a color signal, if the length of the cable is within the dimensions of the machine (the length of such a cable is usually about 10 m or so), the change in the level or a time lag of the color signal caused during a transmission process through the cable does not bring about a change in brightness or color as much as human is capable of recognizing with his eyes. Thus, it is possible to directly connect the CNC controller with the CRT display through a cable.
Meanwhile, in the case of the LCD, a standard type LCD is capable of displaying 512 colors to 260 thousand colors. Such color signal, as it is a digital signal, requires signal lines of 3.times.3 (512 colors) to 6.times.3 (260 thousand colors), and further signal lines for liquid crystal control for horizontal and vertical synchronizing signals and so on. Since the color signal is a digital signal as described above, if an error occurs at a higher-order bit of the color signal (for example, if the bit is "0" when it has to be "1" or if the bit is "1" when it has to be "0"), brightness undergoes a change by 50%.
Moreover, in the LCD, a dot matrix is used for display, and a display ranging from 640.times.480 dots to 800.times.600 dots is currently possible. In order to display on a screen an image having no flicker, there is a need of displaying an image on a screen at a cycle of 60 to 80 times per second. For this reason, a transmission must be made with a clock of about 25 MHz (=(640+.alpha.).times.(480+.alpha.).times.60) to 40 MHz (=(800+.alpha.).times.(600+.alpha.).times.80)(where, .alpha. is a positive integer). Further, as display is done line by line, a sampling clock of 25 MHz to 40 MHz synchronous with a color signal is

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