METHOD TO DRAW CURVES WITH TWO STEPPER MOTOR DRIVEN WHEELS AND A PENCIL

Abstract: Method of drawing curves with a polar step method. In this case two electrical stepper motors (3) are used, with each of them driving a co-axially placed driving wheel (1). In the centre between the contact points of the driving wheels against the drawing surface (10) a pencil (6) is attached. If the stepper motors turn the same amount but in different senses of rotation a relative turning between the axle of the driving wheels and the drawing surface will be achieved with the centre of rotation at the point of the pencil. If the stepper motors turn the same amount in the same sense of rotation, a linear relative movement between the pencil and the drawing surface will be achieved and a line will be drawn. With alternating turnings and linear movements a curve can be drawn.

Description: Method to drai curves uiith tωo stepper motor driven ωheels and a pencil. Applications of the innovation. For digital ωorkiπg equipments, such as computers, you often ωaπt peripheral equipments, ωhich can draw curves, outlines, pictures etc. Such a peripheral equipment, is the so called printer or plotter, ωhich gets information from a computer. With this information it ωill b ' e able to control some kind of pencil in relation to, for instance, a sheet of paper. The method described in this patent can be used for benefit to¬ gether uiith digital ωorking system, such as computers. Examples of applications: - on a small scale ωith a minimum of moving parts it ωould be able to draω curves on a sheet of paper and - on a large scale it ωould be able to draω outlines for cutting on sheets of metal etc. Technology on ωhich the innovation is based. A movement between tωo points, from point A to point B, can be done in tuo steps: 1. You determine the angle in relation to the momentary position and set the equipment in the desireτj direc- tion at point A tαωards point B. 2. You determine the distance betωeeπ A and B and per¬ form the linear movement from point A to point B. If you put tuo conaxial ωheels of the same size, that is ωheels mounted along the same axle, against a surface, you can get the desired change of the angle betωeεn the direction of the axle of the ωheels and the surface, by turning both ωheels the same amount, but in different senses of rotation. When doing so, one point at the middle of the axle will be resting in relation to the surface. This corresponds to point 1 mentioned above. If you then turn the ωheels the same amount* in the same sense of rotation, the middle point of the axle ωill move linearly in relation to the surface. This corresponds to paint 2 men¬ tioned on the previous page. If you choose the smallest angles of turning for the driving ωheels sufficiently minute, even arbitrarily good non-linear curves can be drawn with , what can be called, polar steps. Instrument on ωhich the innovation is based. The ' innovation is based on the use of stepper ■ motors, that is electrical motors ωhich 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 de¬ sired total angle of rotation clockwise or anti-clockwise by sending a certain serie 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. List of drawing figures. Figure 1: The first example of design. Figure 2: The second example of design. Examples of design. Example 1: Plotter for smaller surfaces. The figures below refer to draωing figure 1. For drawing curves on a smaller sheet of paper the innovation can be designed so that tωo driving ωheels (1) ere mounted conaxially under a plane supporting surface (2) and are driven by separate stepper motors (3). On the supporting surface you place a sheet of paper (4), ωhich ωill be pressed against the driving ωhεels by tωo conaxially mounted freerunning support¬ ing ωheels (5). Through the centre betωeen the supporting ( OMPI ωheels some kind of pencil (6)is attached against the paper. The supporting ωheels and the pencil are kept in their places by an arm (7), that can be turned dαωnωards. The paper can be turned tαωards the desired direction ωith the pencil in the centre of rotation by turning the stepper motors and the driving ωheels the same amount but in differ¬ ent senses of rotation. A linear movement of the paper is achieved by turning the stepper motors and the driving ωheels the same amount in the same sense of rotation so that the pencil draws a line. Example 2: Plotter for bigger surfaces. The figures below refer to drawing figur 2. For drawing curves on bigger surfaces, for instance on big sheets of metal, the innovation can be designed so that tωo driving wheels (1) are conaxially mounted on a chassis (8) and are driven by separte stepper mαtors(3). The chassis also has tωo supporting balls (9) ωhich create little friction. The chassis is placed on the drawing surface (10). Through the centre betωeen the driving ωheels some kind of pencil (6) is attached on the drawing surface. The chassis can be turned in the desired direction ωith the pencil in a point on the drawing surface by turning the step¬ per motors and the driving wheels the same amount but in diff- ereπt seηses of rotation. A linear movement of the chassis can be achieved by turning the stepper motors and the driving ωheels the same amount in the same sense of rotation so that the pencil draωs a line.

Claims: Claims. I claim a method of drawing curves ωith two stepper motor driven ωheels and a pencil by a polar technique of movement c h a r a c t e r i z e d b y that the two conaxially placed driving wheels (l) . affect the relative position of the pencil (6), placed in the centre between the contact points of the driving wheels against the drawing surface (4 respect¬ ively 10) , and the drawing surface in tωo ways: - when the driving ωheels ωith power from the stepper motors (3) are brought to turn the same amount but in different senses of rotation, a change of angle will occur between the axle of the driving wheels and the drawing surface ωith centre of rotation at the contact point of the pencil against the drawing surface, and - ωhen the driving ωheels ωith poωer from the stepper motors are brought to turn the same amount in the same sense of rotation, a linear movement betωeen the pencil and the drawing surface will occur. OMPI

Inventors: BAECKMAN B
Applicants: BAECKMAN B
Application year: 1981
Main classification: G06K15
IPC codes: B43L11, B43L13, G06F3, G06K15