GB2129175A - Draughting machine - Google Patents

Abstract

A draughting system which is able to directly produce hard copy in response to control by a draughtsman as well as remembering what is drawn. Manual erasing can be effected on hard copy with parallel erasing in the memory. <IMAGE>

Description

SPECIFICATION Draughting machine This invention relates to draughting machines such as are used in engineering, architectural or cartographical drawing offices.

United Kingdom patent specification disclosed a semi automatic draughting machine which relies upon a conductive stylus and support surface for defining position of a drawing instrument. Such a machine is inherently inaccurate when utilised for large and complicated drawings.

Another form of draughting machine employs a visual display unit (VDU) upon which various lines and shapes can be displayed by appropriate selection of programme by an operator.

Unfortunately, such a system does not enable the display of the total contents of a very large drawing at full scale, (because of VDU size), although, of course, parts of the drawing can be selected and displayed with magnification. Also, the display is not a hard copy, so that a separate printer has to be utilised in order for a normal drawing to be produced.

An object of the present invention is to seek to provide an improved draughting system which enables the draughtsman to work directly and accurately on a full size normal drawing and enables immediate hard copy to be produced.

According to the present invention, a draughting system comprises: drawings means for drawing a desired shape or alphanumeric text directly on hard copy recording means, and control means which generates control signal for controlling the drawing means to draw any desired shape and alphanumeric text In accordance with instructions received from an operator, or stored within the control means, the control means containing a memory for storing the control signals.

Preferably, the means for drawing comprises a standard pen, which may draw upon paper or up foil.

Conveniently, the control signals are convertible into positional coordinate format.

The control signals may control stepper motors to move the drawing means. The drawing means may be moved rapidly by a draughtsman for coarse positioning, such as by use of a joystick arrangement.

Reference is directed firstly to Figure 1, in which a pen unit 1 is shown mounted on a rail 2.

Motion of the pen unit 1 along the rail 2 provides movement of the pen in the direction of the Y axis as may be seen from the Figures. The pen unit 1 can carry a number of pens, in this case two pens as indicated by sockets 3 and 4. The rail 2 is secured to a slidable mounting 5 which slides along a second rail 6. Movement of the mounting 5 5 along the rail 6 enables the plotter to be given a degree of freedom in the X direction as indicated in the Figures. Limit switches 7 and 8 are provided at opposite ends of the rail 2 to prevent overtravel of the unit 1. Limit switches 9 and 10 are provided at opposite ends of the rails 6 to prevent overtravel of the mounting 5. The rails 2 and 3 are disposed over a normal draughtsman's board 12. A fullsized AO drawing paper or foil 13 can be disposed on the board 12.

A A visual display unit 14 is part of an assembly 1 5 secured to the bottom right of the drawing board. The assembly 15 also contains a controlled keyboard 16 and a joystick 17.

Reference is now directed to Figure 2.

Operation of the draughting machine is made possible by a micro-computer 20. The microcomputer 20 can derive control signals which derive from storage means, such as a floppy disc stored in a unit 21, a magnetic card stored in a magnetic card reader 22 or from information received via a gate 23 and a controller 24 from an operator controlled joystick 25 or keyboard 26.

Also, data from which control signals may be prepared can be derived from an external terminal 27. Control signals derived by the micro-computer 20 are fed to the controller 24, which operates a driver 28 for the visual display unit 14 and also operates a delayed pulse generator 29 for operating the pen unit 1 in "thick" or "thin" format and also drives stepper motors 30 and 31 for moving the pen unit in the Y-direction and the assembly 5 in the X-direction. Movement of the pen unit and assembly 5 is effected by the stepper motor via gears and wiring (not shown). The rail 6 6 is traversed in the X-direction by the assembly 5 drawn by a flexible wire cable. The cable is wound on to a motor driven grooved pulley mounted near one end of the rail, and looped over a second pulley at the other.The rail 2 is secured at right angles to assembly 5 and provides the track for the 2 pen unit 1 which travels in the Y-direction.

The pen unit is driven by a second wire cable attached to a similar grooved pulley and motor assembly secured to the assembly 5.

In operation, coarse positioning of the pen unit 1 is controlled by the joystick 25, fine positioning and accurate draughting work in metric units is controlled by a push button array on the keyboard 26, permitting alpha numeric and "command" information to be an input. The "commands" include the following: line between any two points, line of selected length and angle to a datum, offset point at selected distance and angled to a datum, circle, arc, alpha numeric printing and electrical circuit symbols.

Other facilities include a "record-playback" facility, permitting drawn shapes to be stored in memory in the micro-computer 20, or recorded on magnetic cards in the reader 24 to be "played back" at a choice of scale at any desired point and orientation. The drawn shape can also be mirror imaged about the X or Y axes.

Both mechanical and electrical design work may be drawn, on ordinary draughting paper, using combinations of the commands defining the standard geometric shapes; and alpha numeric scripts may be printed using the keyboard characters. The visual display unit enables, where necessary, the designer to verify data prior to printing on the drawing. Likewise, pen coordinates can be brought up on the display unit when required.

In more detail, the joystick control 25 permits the pen unit 2 to travel in one of eight possible directions, corresponding to the fourcardinal directions, north, south, east and west and the intermediate positions. Two speeds are provided, determined by the deflection of the joystick, but variations in speed can be provided by the microcomputer when required. Initial deflection of the joystick generates a slow traverse speed of .4mm per second, further deflection increases the speed to 1 7mm per second.

In its normal draughting mode, the machine plots to the same dimension as those which have been input. However, means is provided whereby the machine can be set to plot at dimensions differing from those which have been input. To employ this facility an operator merely has to select an appropriate key on the keyboard 26.

When a line is drawn, the operator merely has to input any two pairs of coordinates and press an appropriate key to have the line drawn. The line can be rotated by a selection of appropriate keys.

All commands which cause lines, symbols and script to be drawn are sequentially numbered and the number is stored in the micro-computer with the command. Provision is made for groups of work lines to be identified by a single number in cases where often used items or patterns are described and where changes are rarely made, for example a drawing of a hexagonal nut. In normal operation, all workline commands will be stored sequentially in memory in the micro-computer 20.

A warning signal is generated and displayed on the visual display unit when the capacity is ten worklines short of full, at which stage further operation is inhibited by the machine. Three options are available to the operator to make use of information in memory:~ (i) to make a peromanent record "on the magnetic card, floppy disc or terminal", (ii) to play back on to the draughting surface, and (iii) to erase chosen workline commands.

If the operator chooses to erase lines which have been entered into the memory, then he simply performs a parallel operation of physically erasing the line on the paper or foil 13. Once a drawing has been stored in the memory, then when the draughting machine has been actuated by the keyboard, the micro-computer controls the controller to cause the drawing to be drawn. The memory may derive from a drawing which has previously been drawn by the draughtsman on a previous occasion.

It is to be noted, that the operator causes a drawing to be effected on a piece of paper or foil so that hard copy is made by the operator when he is drawing. Also, a large size of drawing is seen all at once. Further, the machine is accurately controlled, even over a large drawing area.

From the above description, it can be seen that an improved draughting machine is provided.

Claims (5)

1. A draughting system comprising: drawing means for drawing a desired shape or alphanumeric text directly on hard copy recording means, and control means which generates control signal for controlling the drawing means to draw any desired shape or alphanumeric text in accordance with instructions received from an operator, or stored within the control means containing a memory for storing the control signals.

2. A draughting system as claimed in claim 1, in which the means for drawing comprises a standard pen which may draw upon paper or upon foil.

3. A draughting system as claimed in claim 1, in which the control signals are convertible into positional coordinate format.

4. A draughting system as claimed in claim 1 , in which the control signals control stepper motors to move the drawing means.

5. A draughting system as claimed in claim 1 in which the drawing means is moved rapidly by a draughtsman for coarse positioning, such as by use of a joystick arrangement.