JPH02171298A - Drafting apparatus - Google Patents

Abstract

PURPOSE: To execute accurate drawing by a simple constitution by providing at least two magnetic field sensors which are juxtaposed in the longitudinal direction of a strip-shaped body constituted of a magnetized material and forming a length scale, and are fixed as scanning devices at the same height from a support surface of a drawing rail. CONSTITUTION: Magnetic field sensors are buried in a drawing rail 10 so that they pass sequentially a specified N pole of a strip-shaped body 7 and then an S pole adjacent thereto on the occasion when the rail is slid along a guide rib 3 of a drawing board. When the drawing rail 10 including a chip or module 20 is moved along the guide rib 3 of the drawing board 1, starting from a prescribed space between the N pole and the adjacent S pole in this strip-shaped body 7, an output voltage transition corresponding to the figure is obtained in an output of a bridge circuit. In this case, shifts of both curves U1 and U2 are given by a spatial distance between the magnetic field sensors 21 and 22 of the module or chip 20. The periods of the curves are at prescribed intervals and the curves have substantially-linear parts as shown by thick lines in the figure. Accordingly, the position of contact of the drawing rail 11 can be determined very accurately within the range of the prescribed space on the basis of these linear parts.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a drawing apparatus, and more particularly to a scanning/scale position control mechanism thereof.

BACKGROUND OF THE INVENTION In detail, the invention generally comprises a plate-like drafting table, a ruler element that can be guided and moved over the drawing table, and at least one sensor for scanning a length scale provided on the plate-like drafting table. and a length measuring device with a scanning device held on a ruler element.

A known drafting device of this type in the form of a carriage drafting machine (DE 2,915,422) is equipped with a photoelectric sensor on each carriage which scans a grid-like length scale provided on the associated running rail. has. Although this length measuring device can perform accurate length measurements, it is relatively expensive to manufacture. Especially because,
This is because the carriage and the running rail are moved relative to each other in a constant positional relationship with small tolerances, and the distance of the photoelectric sensor and the grid-like length scale remains unchanged during operation.

Moved when moving the ruler element on the drawing board.

It is also known to measure the displacement movement of a ruler element of a drafting machine by coupling a signal-generating rotating body to the ruler element, which generates a corresponding signal representing the length of the displacement movement of the ruler element on the basis of rotation ( West German Patent Publication No. 3.027.9
No. 31).

Problems to be Solved by the Invention However, in the former case, it is an object of the present invention to provide a simple, inexpensive, and accurate drafting device.

Since a precise and robust device structure is required to maintain a constant distance between the photoelectric sensor and the grid-like length scale, the manufacturing cost is inevitably high. In contrast, the latter case suffers from a relatively imprecise structure. In this case, because, on the one hand, slight displacement movements occur due to the unavoidable tolerances of the two mechanical parts, and on the other hand, it is not always guaranteed that no slippage will occur between the signal-generating rotary body and the drafting table. be.

Means and Effects for Solving the Problems The invention therefore provides that the drafting table is a drafting board, the ruler element consists of a drafting rail guided on one side, and that the length graduations alternate in the longitudinal direction of the strip. consisting of strips of N and S magnetized material, the strips being longitudinally juxtaposed and fixed at equal distances from the receiving surface of the drafting rail, each of which is one of the Wheatstone bridge circuits;
This problem is solved by a drafting device of the type mentioned at the outset, which is characterized in that it is provided with at least two magnetic field sensors arranged on one side.

In the case of the drafting device according to the invention, the drafting table consists of a drafting board and the ruler element consists of a drafting rail guided on one side by the drafting board. In the case of this type of structure, the distance from the drafting table to the drafting rail,
That is, if the distance from the length scale to the sensor changes 1, for example when optically scanning a length measuring device of the type mentioned above,
There is a risk that the changes described above may be interpreted as movements in the direction of the length scale, resulting in errors.

In contrast, in the drafting device according to the present invention, at least two magnetic fields are arranged in the longitudinal direction of the strip-shaped body made of magnetized material and forming a length scale, and fixed at the same height from the receiving surface of the drafting rail. A specially constructed scanning device equipped with a sensor is used. Therefore.

The at least two magnetic field sensors detect an equal change in magnetic field strength when the distance from the drawing rail to the drawing board changes. Since the two magnetic field sensors are placed on different sides of the Wheatstone bridge circuit, the above change in magnetic field strength will cause equal signal changes on the sides of the bridge circuit, i.e. the signal difference between the sides of the bridge circuit will be constant, so this signal change cannot be interpreted as a displacement movement along the length scale.

For the magnetic field sensor, four identical magnetic field sensors are integrated to form a Wheatstone bridge circuit, and two Particularly suitable is a device in the form of a module (for example K M Z IOA from Balbo) which can be installed on a drafting rail so that the magnetic field sensors are arranged longitudinally in a strip of magnetized material.

The strip of magnetized material can be embedded in the drawing board, with the top surface of the strip flush with the surface of the drawing board, and this is preferred.

In order to keep variations in the spacing between the magnetic field sensor and the strip of magnetized material as small as possible during operation, the strip can be arranged adjacent to the guide of the drafting rail.

The invention will now be described in detail with reference to the drawings, which schematically show embodiments.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The illustrated drawing board 1 is essentially of a conventional construction, with four guide ribs 3.4.5 for guiding the drawing rail 10.
．． 6 on four sides. A conventional clamping rail 2 for fixing drafting material (paper) extends parallel to the guide ribs 3. The above-mentioned clamp rail 2 and guide rib 3 are installed on the drawing board.
Embedded between the two is a band-like body 7 made of a material alternately magnetized to N (positive) and S (negative) and exhibiting the functions described below.

One end of the drafting rail 10 has two corresponding guide ribs (e.g.
Guide ribs 15,16 are provided for sliding the drafting rail 10 along the guide ribs 3) of the drafting board 1. A housing 11 is fixed to the end surface of the drafting rail 10, which is provided with guide ribs 15.1B, and is capable of receiving a clamping device (not shown) customary for drafting rails of this type.

Furthermore, the housing 11 has two display devices 12 (e.g. LC
D display) and an operating knob 13, 14, which in particular makes it possible to zero-set the display.

The drafting rail has an exposed lower surface in the area of the housing 11, and is positioned directly above the strip 7 when the drafting rail 1O engages with the guide rib 3 of the drafting board 1, as shown in FIG. A scanning device in the form of a module or chip 20 is provided.

The chip 20 forming the scanning device is manufactured by, for example, Valbo (
Valvo GIIlbll) model K M Z IO
A chip with four magnetic field sensors 21, 22, 23, 24, located in the same plane and connected to form a Wheatstone bridge. including. In this case, 2
Two magnetic field sensors 21,22 are each located in each branch (Zvelg) of the bridge. That is, magnetic field sensor 21 is in the branch containing magnetic field sensor 23 and magnetic field sensor 22 is in the branch containing magnetic field sensor 24. The magnetic field sensors 21,22 are arranged side by side equidistant from the lower edge of the module or chip 20 (FIG. 4). This module or chip 20 has its lower edge (FIG. 4) located on the underside of the drafting rail 10, and has two magnetic field sensors 21.
22 are located side by side in the longitudinal direction of the strip 7, that is, when sliding the rA diagram rail 10 along the guide rib 3 of the drawing board 1, the 2 Next, it is embedded in the drafting rail 10 so as to pass through the adjacent S pole.

In the strip 7 of FIG. 2, starting from a predetermined distance (for example 2.5 m+a) between the north pole and the adjacent south pole, the drafting rail 10 containing the chip or module 20 is moved along the guide rib of the drafting board 1. If you move along 3.

At the output of the bridge circuit (FIG. 4), an output voltage profile corresponding to FIG. 5 is obtained. In this case, the deviation of the two curves U, U2 in FIG. 5 is given by the spatial distance of the magnetic field sensors 21, 22 of the module or chip 20. The period of the curve is a predetermined interval (2.51111 in this case) and 1
The curve has a substantially straight portion as shown by the thick line in FIG. in this case.

Magnetic field sensor 21 related to the strip 7 embedded in the drawing board 1
．． At each position of 22, any one curve (Ul, U
2) It is known that at least one straight line section exists. Therefore, if the above straight line section is divided into steps of equal size in the direction of the amplitude V, based on this straight line section, 2.5 mm
The relevant position of the module or chip 20 can be determined very precisely within the range of 2.5 mm.
The position of the drafting rail 11 can be determined extremely accurately within each range of . For example, assuming that the evaluable straight line portion of one curve extends over an amplitude range of 2■, and dividing the above amplitude range into 80 steps, +2.5
When covering a range of mm, more than 5 steps per 1710 mm are obtained, thus the strip 7
High accuracy can be achieved in determining the position of the drafting rail 10 within each range of 2 and 5 mm.

That is, when the drawing rail 10 is moved along the guide rib 3 of the drawing board 1, the magnetic sensors 21 and 22 are used.

On the one hand, one can count the number of 2.5 mm ranges (spacings) between adjacent N and S poles that have been passed by counting the zero point crossings of the curve of FIG. Due to the above-mentioned division in the direction, it has not been completely passed through (
position within a range (interval) of 2.5 mm (during the passage) can be determined accurately, i.e. the overall distance traveled by the drafting rail 10 from one position to another can thus be determined accurately. be able to.

If the distance between the magnetic field sensor 21, 22 and the strip 7 changes during the above displacement movement of the drafting rail 10,
The magnetic field strength detected by the magnetic field sensor decreases, ie the amplitude of the curve in FIG. 5 decreases, without the position and course of the curve changing.

An amplitude change of this kind is therefore recognized as a two-space change and cannot be interpreted as a movement of the drafting rail lO along the guide rib 3.

Furthermore, when using a drafting rail, it must be known in which direction the changes along the guide rib 3 of the drafting rail 10 are made. Therefore, as shown in FIG.
A supplementary rectangular wave transition is obtained from the curves U, , U2 in the figure. In this case, the flank of the rectangular wave curve in the upper graph of FIG. 6 indicates whether the amplitude of the two curves U1 is greater or smaller than the amplitude of the curve U2, while the flank curve of another rectangular wave curve in the lower graph is: It indicates whether the arithmetic mean value of the amplitudes of both curves U, , U2 at one position within a range of 2.5 mm is smaller or larger than 172 of the maximum amplitude of one curve.

The direction of movement of the drafting rail 10 along the guide rib 3 (ie upwards or downwards in FIG. 1) can be determined by the above-mentioned rectangular wave profile. in this case.

Each time the test passes through the 2.5+am range, does the flank of the rectangular wavy line in FIG. 6, which indicates that the amplitude of the curve U1 becomes larger than the amplitude of the curve U2, pass?

First, it is confirmed whether the flank of the rectangular wavy line in the lower graph of FIG. 6, which indicates that the average value of the amplitudes of both songs tlilU+ and U* has become smaller than 1/2 of the maximum amplitude, has been passed. If the first flank listed is passed first, then
In the graph of Figure 5.6 it means that a movement has taken place from left to right, whereas otherwise it means that a movement has taken place in the opposite direction.

Of course, other flanks of the rectangular wavy line shown in the graph of FIG. 6 can also be used to determine the direction profile.

[Brief explanation of the drawing]

1 is a plan view of a drawing board with a drawing rail; FIG. 2 is a perspective view of a strip of material alternately magnetized to N and S; FIG. FIG. 4 is a partial cross-sectional view taken along - The figure is a graph showing the transition of the signal voltage obtained by both magnetic field sensors when moving along a strip made of magnetized material. It was done. It is a graph showing the signal transition for determining the movement direction of the drafting rail. Fig, 2 1... Drafting table, 7... Length scale (band-shaped body)
. 10... Ruler element (drafting rail).

Claims (1)

[Claims] 1) A plate-like drafting table, a ruler element that can be guided and moved over the drawing table, and at least one sensor that scans a length scale provided on the plate-like drafting table, and the ruler element has and a length-measuring device with a held scanning device, in which the drawing table is a drawing board (1), the ruler element (10) consists of a drawing rail (10) guided on one side, and the drawing table comprises a drawing rail (10) guided on one side, The graduations are composed of strips (7) made of material magnetized to N and S, alternately in the longitudinal direction of the strips (7), juxtaposed in the longitudinal direction of the strips (7), and arranged on the drafting rail (10).
Drafting device, characterized in that it is provided with at least two magnetic field sensors (21, 22) which are fixed at equal distances from the receiving surface of the Wheatstone bridge circuit (21, 22) and are each arranged in one branch of the Wheatstone bridge circuit. 2) Four magnetic field sensors (21, 22, 23, 24) where the two magnetic field sensors (21, 22) are in the same plane and are connected to form a Wheatstone bridge circuit.
2. Drafting device according to claim 1, characterized in that it is part of a module (20) comprising: 3) The drawing device according to claim 1 or 2, characterized in that the strip is embedded in the drawing board (1). 4) According to one of claims 1 to 3, the strip is arranged adjacent to a guide (3) for a drafting rail configured on the drafting board (1). drafting equipment.