Geometrical instruments – Scriber – Straight-line
Patent
1982-01-26
1984-05-22
Little, Willis
Geometrical instruments
Scriber
Straight-line
33 27R, 33 32C, 33 32F, B43L 1300
Patent
active
044493010
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention is directed to a system for drawing curves with two stepper motor driven wheels and a pencil.
For digital working equipment, such as computers, peripheral equipment, which can draw curves, outlines, pictures etc. is often desired. Such an item of peripheral equipment is the printer or plotter which gets information from a computer. With this information it will be able to control some kind of pencil in relation to, for instance, a sheet of paper. The method described in this patent can be beneficially used with digital working systems such as computers. Examples of applications: curves on a sheet of paper and metal etc.
SUMMARY OF THE INVENTION
A movement between two points, from point A to point B, can be done in two steps: the equipment in the desired direction at point A towards point B. movement from point A to point B.
Two coaxial wheels of the same size, that is wheels mounted along the same axle, when placed against a surface, will produce the desired change of the angle between the direction of the axle of the wheels and the surface, if both wheels are rotated by the same amount, but in opposite directions. One point at the middle of the axle will be stationary in relation to the surface. This corresponds to step 1 mentioned above.
If the wheels are then rotated by the same amount in the same direction, the middle point of the axle will move linearly in relation to the surface. This corresponds to step 2 mentioned above.
If sufficiently minute angles of rotation for the driving wheels are chosen, even arbitrarily good non-linear curves can be drawn with, what can be called, polar steps.
The innovation is based on the use of stepper motors, that is electrical motors which by using pulses of current in a number of windings can make the axle turn a certain step of angle. With such electrical motors you consequently create a desired total angle of rotation clockwise or anti-clockwise by sending a certain series of pulses of current. These movements are reversible and any accumulation of error in the angle of setting will not occur, so the momentary error in the angle of setting has an upper limit depending on certain limitations specific to each type of stepper motor.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1: The first embodiment of the invention.
FIG. 2: The second embodiment of the invention.
DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS
The first preferred embodiment is a plotter for smaller surfaces.
The figures below refer to drawing FIG. 1. For drawing curves on a smaller sheet of paper the innovation can be designed so that two driving wheels (1) are mounted coaxially under a plane surrounding surface (2) and are driven by separate stepper motors (3). On the supporting surface you place a sheet of paper (4) which will be pressed against the driving wheels by two coaxially mounted freerunning supporting wheels (5). Through the centre between the supporting wheels some kind of pencil (6) is attached agains the paper. The supporting wheels and the pencil are kept in their places by an arm (7), that can be turned downwards.
The paper can be turned towards the desired direction with the pencil in the centre of rotation by turning the stepper motors and the driving wheels the same amount but in different senses of rotation.
A linear movement of the paper is achieved by turning the stepper motors and the driving wheels the same amount in the same sense of rotation so that the pencil draws a line.
The second preferred embodiment is a plotter for bigger surfaces.
The figures below refer to drawing FIG. 2. For drawing curves on bigger surfaces, for instance on big sheets of metal, the innovation can be designed so that two driving wheels (1) are coaxially mounted on a chassis (8) and are driven by separate stepper motors (3). The chassis also has two supporting balls (9) which create little friction. The chassis is placed on the drawing surface (10). Through the centre between the driving wheels some kind of pencil (6) is attached on the drawin
REFERENCES:
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patent: 874702 (1907-12-01), Patton
patent: 1537393 (1925-05-01), Walsh
patent: 2343035 (1944-02-01), Weihs
patent: 2392654 (1946-01-01), Fine
patent: 3516163 (1970-06-01), Hisserich
patent: 3726019 (1973-04-01), Adler
patent: 4130085 (1978-12-01), Hewitt
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