DE4240803C2 - Device for controlling a reciprocable carriage which carries a print and / or read head - Google Patents

Description

The invention relates to a Device for controlling a reciprocable Carriage that has a printhead and / or a read head carries according to claim 1 or 3.

It is known to determine the position of a moving printhead or reading head, especially in an office device, within a Print line to generate measurement signals that trigger a print or Read process can be used. Here one moves with the Printhead carriage along permanently connected optical position encoder a ruler that runs parallel to the side walls of the printer Platen is cocked. The ruler has a narrow tolerance division of 0.2 mm. The digitized signals from the optical position transmitter are 90 degrees out of phase with each other by position increments and To be able to derive reversals of direction.

These linear scanning signals are combined in one application-specific control electronics circuit Print command control, positioning and speed control processed (PKI Technical Notice 3/1989, pages 28 to 30).

To control the position of a printhead has also been used up to now a clock disc detects the position of the driving electric motor, with disadvantages of the mechanical games in the drive systems of Toothed belt, spindle or gear are connected. For timing belts that form a vibration-sensitive mass-spring system adverse vibrations. The timing disk encoder is also used in a printer only indirectly detects the position of the print head and controlled, with a simple improvement in accuracy and Resolution is only possible to a limited extent and is very time-consuming to achieve would.

A known from DE-OS 25 12 349 Path sensor for a clock control of a non-mechanical printer used. A beam of light must already be available for other purposes stand. The course of the light in a cracked mark translucent rod is only considered as far as the translucent Rod is made of a translucent plastic. The arrangement of the translucent rod is there parallel to the line direction Record carrier.

From JP-61-263 779 (A) a mechanical printer is known from which is a light source together with the printhead is movable. The light emitted is by the Hole pattern of a fixed ruler.

The principle of redirection from radial to an elongated light guide EP 0 480 512 A1 describes detectors that strike and are arranged on both ends known. This will be a fluorescent optical fiber used which receives evaluation light and generates fluorescent light, which then travels through the length of the fiber and at one or both ends the same is received.

The invention is based, which resulting from vibration-sensitive components and empty games Avoid disadvantages and create a system that works with one the smallest possible, cost-saving number of components and one uncomplicated construction. This object is achieved according to the invention with the characteristics of claims 1 and 3 solved.

The advantages achieved with the invention are in particular that an exact result is achieved in digitally processable form, being a small number of cost-saving components and a uncomplicated construction with considerable space saving and low Manufacturing costs can be achieved.

An advantageous embodiment of the invention is in claim 2 specified.

Embodiments of the invention are shown in the drawing and are described in more detail below. Show it

Fig. 1, the Inventive principle in conjunction with a print head,

Fig. 2 is a block diagram of an optical sensor,

Fig. 3 is a side view of the light source optical fiber print head unit,

Fig. 4 shows a cross section through a circular light waveguide with an integrated splitter means,

FIG. 5a is a longitudinal section through the same arrangement with two photodetectors,

Fig. 5b is a graph of the resultant average output currents,

Fig. 6a shows an alternative embodiment of the optical fiber splitter device and

Fig. 6b to FIG. 8a resulting output current history.

The perspective view according to FIG. 1 shows the optical positioning system. A light source 1 consists, for example, of a light-emitting diode, a laser diode or a small incandescent lamp, the light of which - suitably focussed - is thrown via a light beam 4 onto an optical waveguide 5 in addition to a print head 2 (reading head) which prints a receipt 3 . It goes without saying that the light beam 4 can also be deflected via mirrors or prisms or can be brought to the optical waveguide 5 by means of a (more or less long) optical waveguide. Furthermore, a divider device 6 is assigned to the optical waveguide 5 , which consists of translucent and opaque subregions, which are usually equidistant, either applied directly to the optical waveguide 5 , which, for. B. can be done by screen printing or is arranged as a separate component directly in front of the optical fiber 5 parallel to the optical fiber 5 . The optical waveguide 5 is suitably doped with fluorescent dye molecules, which generate the optical measurement signals to be evaluated and transmit them by total reflection, preferably along a movement axis 10 in the direction of two photodetectors 7 and 9 . Against sources of interference are the photodetectors 7 and 9 with suitable optical filters 8, the narrow-permeable in the regions of the fluorescence wavelength, but particularly in the region of the exciting light source impermeable, is provided and a is the optical waveguide 5 is applied, if necessary directly on the ends. 5

The indicated in Fig. 1 divider means 6 is shown in FIG. 5a, in one embodiment as a mask 6 a in front of the optical fiber 5, in which a number of light-transmitting areas by slots 22 which allow the passage of the excitation light, and a plurality of opaque areas by means of Web 23 are attached between the slots 22 for blocking the light beam 4 . Suitable widths of slot-bar arrangements also result from FIG. 8a. They allow the detailed determination not only of the position of the printhead 2 but also of the direction of movement of the printhead-light source arrangement up to the detection of boundary or initial conditions.

As shown in FIG. 1, the arrangement of the light beam 4 can take place opposite to the direction of action of the printing elements of the print head 2 on the surface 11 of the document 3 .

According to FIG. 2, a block diagram of the optical fibers 5 of the light source 1 is in the form of opposite and the latter, together with the printing head 2 shown movable, wherein the optical fiber 5, the optical filter 8 and the photodetector are assigned. 7 Drive electronics 17 are connected to the print head 2 and a supply 19 for the light source and evaluation electronics 20 are connected to the light source 1 . The photodetector 7 works here with a mirror 21 to increase the intensity. The dividing device 6 is connected between the light beam 4 and the optical waveguide 5 .

As shown in FIG. 2, one end 5 a can be closed off by mirror 21 , which either forms its own component or is applied directly to end 5 a of optical waveguide 5 . This plane mirror reflects the fluorescent light back into the optical waveguide 5 at the same angle of reflection as the angle of incidence of the fluorescence falling on it; thus this light is effectively guided within the permissible angle for total reflection within the optical waveguide 5 , brought to the photodetector 7 and thus contributes to increasing the intensity of the measurement signal to be evaluated - with negligible attenuation within the optical waveguide 5 up to a factor of 2.

FIG. 3 shows a side view with a section through the light source 1 , the divider device 6 , here as a mask 6 a in front of the optical waveguide 5 and thus represents an independent component. Furthermore, a drive 12 of the print head 2 is shown above the line 11 .

According to Fig. 4 shows a further alternative of a splitting means 4 is shown as part of the optical fiber 5 itself, that is integrated in the same. This arrangement consists of two sections, an inner core 5 b, the fluorescent optical waveguide 5 made of glass or plastic with a suitable refractive index n1, which is chosen so that this refractive index is greater than a refractive index n2 of the surrounding tubular carrier substance (outer optical fiber 5 c) for the divider device 6 . The divider 6 can also be made of glass or plastic, the actual divider 6 mechanically, for. B. can be introduced by scoring, cutting, milling, etc. Other methods for producing the divider device 6 are printing, in particular screen printing, with a rectangular cross section of the optical waveguide divider device 6 being more suitable. Thermal processes and laser processing allow particularly fine structures, comparable to those by etching or photographic methods, provided that the appropriate material is used, being carried out directly by exposure, development and fixing on the outer divider device 6 or subsequently as a film strip or scales printed on a film can be applied. For this purpose, the material is selected accordingly, restrictions being imposed only by the refractive index.

Divider devices 6 , which are present as a negative in a matrix, ie with a raised structure, appear particularly suitable for series production where there is supposed to be a recess in the divider device 6 itself. The Fig. 5a shows such an embodiment. Here is in the negative form z. B. by injection molding process, material with the refractive index n2, for example PMMA (polymethyl methacrylate), is first introduced for the dividing device 6 , then the dye molecules 28, which are uniformly present in suitable plastic with n1 greater than n2. The arrangement can not only have round, as shown in Fig. 4, but also other cross sections, in particular rectangular (polygonal).

Fig. 5a shows a linear dividing means 6 according to the invention having a structure in which the surface with such a dividing means 6 and the fluorescent optical fiber 5 is present according to the shape described above as a single component.

The operation of the thus constructed linear portions device 6 is shown in detail in Figures 5a and will be described in more detail below. Once the light from the light source 1, which is focused in accordance with incident on the dividing means 6, it always occurs in the core 5 b of the optical fiber 5 when it falls through the slots 22 almost undisturbed. Here the light falls through the raised surface of the outer jacket. This incoming light is absorbed by the dye molecules 28 in the optical waveguide 5 , as a result of which the dye molecules in turn fluoresce immediately.

Delays due to the lifespan of the excited dye molecules (typically in the nanosecond range), scattering in the optical waveguide 5 (less than nanoseconds) and due to the propagation speed of the light (also in the nanosecond range) can be neglected in the applications here (typical time resolution in the microsecond range).

However, with strong attenuation of a plastic optical waveguide 5, the dependence of the amount of light registered on the photodetector 7 on the distance of the incident light or the light source / printhead arrangement, on the coordinate X in FIG. 5b, can be considerable. It is therefore better in such cases to mount the photodetectors 7 and 9 on both ends of the optical waveguide 5 , although in most applications a photodetector 7 is sufficient.

The light signals can of course be guided at both ends through further flexible optical fibers or fiber bundles to a common photodetector 7 .

However, if the arrangement shown in FIG. 5a is selected, then according to FIG. 5b, after addition 25 of the averaged output signals 26 and 27 of both photodetectors 7 and 9, an approximately constant signal 25 is obtained, regardless of the respective scanning position X.

It goes without saying for the person skilled in the art that, of course, with sufficiently large attenuation of the optical waveguide 5, the scanning position itself can be determined from the difference between the two photodetector signals and / or the output signals 26 and 27 , which is in principle independent of a dividing device 6 .

Finally, from the increase or decrease in the output signals 26 and 27, a conclusion can be drawn about a movement in one of the two possible directions of movement of the print head 2 .

A divider device 6 according to FIGS. 6a and 6b serves the same purpose. Here, the slots 22 of the shape shown are introduced into the dividing device 6 . In such a case, the scanning light profile 29 of the light source 1 has the profile shape shown in broken lines in the plane of the dividing device 6 . A simple diaphragm and a cylindrical lens 31 in front of the light source 1 serve this purpose. In such a case, an output signal 30 of the photodetectors 7 or 9 runs at the output signal level 30 a shown in the lower part of FIG. 6 b, the output level 6 c initially being maximum and then falling approximately to half the value (stage 6 b), if the printhead 2 with the light source 1 runs from left to right over the divider device 6 - and only half the amplitude followed by the full amplitude, occurs when the printhead 2 with the light source 1 moves from right to left along the divider device 6 .

In summary, it can be stated that by using the simplest linear divider devices 6 according to the invention, the position determination and control of print heads or read / write heads in printers or similar office equipment can be manufactured with a simple construction, few components and low manufacturing costs compared to the advantages described the known facilities.

Claims (5)

1. Device for controlling a reciprocating carriage, which carries a printhead and / or a reading head, with an optically scanned scale and a receiver for the measurement signal, which in an evaluation electronics for controlling the drive movement of a carriage motor and / or the actuation of the pressure elements can be entered,

• a light source can be moved together with the carriage for the print head or the read head,
• the light source is directed perpendicular to the axis of movement of the slide,
• focused light beams by means of deflection means consisting of an optical waveguide with a dividing device, along the movement axis of which can be reflected onto at least one photodetector, the output signals of which can be switched to evaluation electronics,

characterized,

• - That the divider device ( 6 ) consisting of a mask ( 6 a) has a slot shape provided with one or more steps ( 6 b), which is opposite a slot width ( 6 d) superior light source profile ( 4 a), so that the output signal ( 30 ) is also present in steps.

2. Device according to claim 1, characterized in

• - That the divider device ( 6 ) is applied to one of the polygon surfaces of an optical waveguide ( 5 ) with a polygonal cross section.

3. Device for controlling a reciprocable carriage, which carries a printhead and / or a reading head, with an optically scanned scale and a receiver for the measurement signal, which in evaluation electronics for controlling the drive movement of a carriage motor and / or the actuation of the pressure elements can be entered,

• a light source can be moved together with the carriage for the print head or the read head,
• the light source is directed perpendicular to the axis of movement of the slide,
• focused light beams by means of a deflection means consisting of an optical waveguide with a splitting device, along the movement axis of which are reflectable onto at least one photodetector, the output signals of which can be switched to evaluation electronics,

characterized,

• - That the optical waveguide ( 5 ) alternately in succession from doped discs made of fluorescent material and undoped discs, ie axially composed of crystal-clear material.