EP0040879A2 - Matrix printer with automatic print-head adjustment - Google Patents

Abstract

Matrix printer with a print head which can be displaced in the line direction along a paper guide and in which there are a number of printing elements which have a first printing position for printing from left to right and a second printing position for printing from right to left. The print head with its print elements is automatically shifted from one print position to the other print position by a change in the movement pulse of the print head each time the print head reverses movement by means of a position change member that is relatively displaceable with respect to the print head.

The matrix printer described is used, among other things, in office computers.

Description

The invention relates to a matrix printer with a combination of a carriage and a print head located thereon that can be moved back and forth along a paper guide and has a first printing position for printing character elements when moving from left to right and a second printing position for printing character elements when moving right to left, wherein the drawing elements of a certain print element in the print head, which are printed on the paper when the print head moves to the right, with respect to the drawing elements of this same print element which are printed on the paper when the print head moves to the left, in are shifted vertically over a distance that is part of the vertical distance between two successive print elements in the print head.

In a matrix printer of the type specified at the beginning of US Pat. No. 4,086,997, the height of the print head in relation to the paper guide is set by exciting an electromagnet, the armature of which is connected via a lever to an eccentric which is connected to a part of the longitudinal guide of the car works together. The printhead is adjusted in height by rotating the printhead around an axis parallel to the line direction. Since the height of the print head can be set optionally, there is a choice between characters whose composite elements (dot imprints) are relatively far apart, and characters whose composite elements are relatively close to one another or even overlap.

However, for many applications it is necessary that the composite elements of the printed character always are relatively close together or overlap. This is the case, for example, in so-called text processing devices. Although an electromagnetic height adjustment of the printhead could be used in such applications, such a height adjustment is relatively expensive because it offers more than is required, ie the optional adjustment.

The invention has for its object to provide a matrix printer of the type mentioned, with which characters can be printed completely automatically in a simple manner, the composite elements of which are relatively close to one another, for which a relatively small number of printing elements is also used.

This object is achieved with a matrix printer according to the invention in that the combination of the carriage and the print head is provided with a chamber in which there is a position change element which is relatively displaceable with respect to this combination by a change in the movement pulse of the print head and thus the Bring printhead to one print position before the pulse change and to the other print position after the pulse change.

Since a change in the movement impulse (product of mass and speed vector) of the print head always occurs in the area at the beginning or at the end of a line, an automatic height adjustment of the print head is obtained without having to use relatively expensive means such as electromagnets. In this area, the reversal of movement of the print head can also be used in order to achieve a relative displacement of the position change element. In general it can be said that the distance in which the height adjustment takes place can lie either before or after the reversal point or on both sides of the reversal point (in terms of time). It is particularly simple and advantageous to essentially or largely reverse the movement even for the height adjustment to be used without using certain inertial forces on the position changing element. In this case, the change in the movement impulse is given by the change in direction of the speed vector.

In a special embodiment of a matrix printer. According to the invention, the position changing member forms the coupling between a friction plate which can be displaced via a guide wall delimiting the chamber and the print head. The use of a separate friction plate as a coupling offers the advantage that different forms of the position change elements can be used with constant friction conditions between the friction plate and the guide wall, because the friction element is, as it were, normalized. It is also possible to obtain a precisely determined coefficient of friction for a relatively long time through the choice of material for the friction plate. The friction plate can also be used to determine the magnitude of the relative movement that the position changing member performs with respect to the print head.

A further special embodiment of a matrix printer according to the invention is characterized in that the chamber is located in the carriage and the guide wall delimiting the chamber is part of a fixedly arranged guide profile extending parallel to the line direction and the print head with the carriage with respect to the guide profile from the first and second pressure state and vice versa is rotatable about an axis of rotation which is perpendicular to the line direction. Since the carriage can be rotated with the print head, the existing guide profile of the carriage can be used to guide the rotary movement.

An embodiment of the invention is explained below with reference to the drawing.

• Fig. 1 eine Vorderansicht eines Matrixdruckers nach der Erfindung zum Teil im Schnitt,
• Fig. 2 eine Seitenansicht bzw. einen Schnitt entlang der Linie II-II des Matrixdruckers nach Fig. 1,
• Fig. 3 eine Draufsicht auf den Matrixdrucker nach Fig. 1,
• Fig. 4 in der Vergrößerung das Stellungswechselorgan, das im Matrixdrucker nach Fig. 1,2 und 3 verwendet ist,
• Fig. 5 in der Vergrößerung ein alternatives Stellungswechselorgan, das in einem erfindungsgemäßen Matrixdrucker verwendbar ist.

Show it

• Fig. 1 is a front view of a matrix printer partly in section according to the invention,
• 2 is a side view or a section along the line II-II of the matrix printer of FIG. 1,
• 3 is a top view of the matrix printer of FIG. 1;
• 4 is an enlargement of the position change element used in the matrix printer according to FIGS. 1, 2 and 3,
• Fig. 5 in the enlargement of an alternative position change organ that can be used in a matrix printer according to the invention.

The matrix printer shown in FIGS. 1, 2 and 3 contains a printhead 3, mounted on a carriage 1, of a type known per se with six electromagnetically displaceable printing pens, the printing ends 5 of which for writing lie on a vertical line. The pressure pins are guided in a bearing 7 near their printing ends 5. The print head 3 is attached to the carriage 1 with the aid of a wire bracket 9 known per se. By means of a pull cable 11 driven by a motor, the carriage 1 can be moved back and forth along a paper guide 13 via a fixedly arranged guide profile 15 which extends parallel to the line direction. The guide profile 15 is U-shaped in cross section (see Fig. 2) and serves as a guide for the carriage 1, which consists of two snap-in parts, i.e. a front part 17 and a rear part 19. The snap connections are located at the reference numbers 21 and 23 (FIGS. 1 and 2). Further similar snap connections between parts 17 and 19 of the carriage 1 are not given for the sake of simplicity.

The carriage 1 is along the guide profile 15 by means of a number of sliding plates 25, 27, 29, 31, 33, 35, 37, 38 and a friction plate 39 out. As explained in more detail below, considerations regarding friction apply to the sliding plates 25 ... 38 differently than with regard to the friction plate 39. Both the sliding plates 25 ... 38 and the friction plate 39 are located in chambers of the carriage 1. The chambers of the sliding plates 25 ... 37 are not designated with reference numerals for the sake of simplicity. The friction plate 39 is located in a particularly marked chamber 41, which is explained in more detail below. All sliding plates 25 ... 38 are arranged with some play in the relevant chambers in order to allow a slight relative movement between the plates and the carriage 1. To achieve the relative movement, the sliding plates 25, 29, 31, 33, 35 and 37 can also be tilted by hemispherical cams 43, 45, 47, 48, 49 and 51, respectively, which are formed in the walls of the relevant chambers. The slide plate 27 is held against the guide profile 15 with a helical spring 53 (FIG. 2). This prevents static over-determination in a direction perpendicular to the row direction. For further reasons to be explained in more detail, the slide plate 38 is also held pressed against the guide profile 15 with a helical spring 55. The sliding plates 25 ... 38 and the friction plate 39 ensure the guidance of the carriage 1 on the guide profile 15. The carriage 1 is dimensioned such that there is clearance around the guide profile 15 between the carriage and the guide profile.

The carriage 1 is rotatable about a horizontal axis 57 (see FIG. 3) perpendicular to the line direction. This axis of rotation 57 runs through the point of contact of the cam 48 with the slide plate 35 and thus perpendicular to the plane of the paper in FIG. 1. Together with the carriage 1, the print head 3 can therefore also be rotated about the axis of rotation 57. The rotation of the combination of the carriage 1 and the print head 3 is carried out by a position changing member, which in the in Fig. 1, 2,3 and 4 shown embodiment is designed as a circular cylindrical roller 59 which can roll and / or slide over the friction plate 39, which can slide again over the guide profile 15. The roller 59, like the friction plate 39, is located in the chamber 41, the upper side 60 of the guide profile 15 forming a boundary. In the chamber 41 there is also a plate 63 which is arranged at an angle α with the row direction 61 and which can be tilted about a rib 64 in the wall of the chamber 41 (FIG. 2). The roller 59 can roll and / or slide over the surface of the plate 63 facing the friction plate 39. The axis of the roller 59 runs perpendicular to the line direction. In the position shown in FIG. 4, the roller 59 lies against a first boundary wall 65 of the chamber 41, while the carriage 1 is moved in the direction of the arrow 67 via the guide profile 15. A parallel second boundary wall 69 lies opposite the first boundary wall 65. Under the circumstances described, the friction plate 39 bears against a third boundary wall 71, which lies opposite a fourth boundary wall 73.

Shortly before the carriage 1 reaches the point of reversal from a rightward movement into a leftward movement at the end of a printed line, the carriage 1 is braked strongly for a short time. The masses of the friction plate 39 and the roller 59 and the frictional forces on the friction plate 39 and on the roller 59 and the compressive force which the carriage 1 exerts on the roller 59 are such that the roller 59 rests against the second boundary wall 69 before the friction plate 39 abuts against the fourth boundary wall 73. Since the distance between the roller 59 and the second boundary wall 69 is greater than the distance between the friction plate 39 and the fourth boundary wall 73, this means that the roller 59 must roll and / or slide over the friction plate 39 for some time before one Sliding process between the friction plate 39 and the guide profile 15 occurs. This is done by choosing one relatively large coefficient of friction between the friction plate 39 and the guide profile 15 in relation to both the coefficient of friction between the roller 59 and the friction plate 39 and the coefficient of friction between the roller 59 and the plate 63 or the first boundary wall 65 and the second boundary wall 69 . The time at which the roller 59 and the friction plate 39 are put on can be either before or after the time of the reversal of movement, depending on the magnitude of the mass inertia forces concerned.

It is also possible, in an alternative embodiment, to brake the movement to the right over a relatively long time. The roller 59 and the friction plate 39 lie on the boundary walls 65 and 71 until the moment of reversal of movement. Only the left movement immediately after the reversal of movement of the carriage ensures that the boundary wall changes. Such a change is possible, for example, if the distance between the friction plate 39 and the fourth boundary wall 73 is greater than approximately twice the distance between the roller 59 and the second boundary wall 69.

By changing the arrangement of the roller 59 from the boundary wall 65 to the boundary wall 69, the carriage 1 rotates together with the print head 3 over a certain angle about the axis of rotation 57 (see FIGS. 1 and 3). This rotation causes the print head 3 to drop by a distance of 0.09 mm in the present case. The horizontal displacement of the printhead due to the rotation about the axis 57 is negligible and thus the resulting obliquity of the printed characters, because the distance between the axis 57 and the roller 59 is relatively large. After the print head 3 has descended by a vertical distance of 0.09 mm, it is then printed from right to left between the drawing elements, which move in the same from left to right Line was already printed. The vertical distance between these drawing elements was 0.18 mm.

It should be noted that the printhead 3 can also be equipped with several printhead columns. For example, printheads with two printhead columns are frequently used. These two printing pin columns can possibly be arranged offset from one another. In the case of offset printing pin columns, the vertical distance between the first printing pin from the first column and the first printing pin from the second column is often 0.18 mm, while the vertical distance between two successive printing pins in the same column of printing pins is 0.36 mm.

When the movement is reversed at the end of the carriage movement from right to left, the carriage 1 is raised with the print head 3 by the same distance by which the combination mentioned has decreased during the last movement reversal. Already when the car 1 is braked, the roller 59 moves from the second boundary wall 69 to the first boundary wall 65. The roller 59 abuts the boundary wall 65 before the friction plate 39 bears against the third boundary wall 71. The time of application can be either before or after the time of the reversal of movement depending on the magnitude of the inertial forces on the roller 59 or the friction plate 39. When utilizing the reversal of motion to bridge the remaining distance between the roller 59 and the boundary wall 65, the mass inertia effect must therefore never be so great that the roller 59 engages before the reversal of motion.

As with the reversal of movement on the right side, with reversal of movement on the left side, the braking of the car can be carried out over a relatively long time. In this alternative embodiment already mentioned, the change of the boundary wall becomes completely and directly after the movement reversal on the left side te causes.

5 consists of a rod 75 with rounded ends 77 and 79. The rod 75 forms the coupling between the carriage 1 and the friction plate 39. For this purpose, the carriage 1 and the friction plate 39 with bearing recesses 81 and 83 equipped. In the situation shown in Fig. 5, the distance a between the end 85 of the friction plate 39 and the fourth boundary wall 73 of the chamber 41 is so large that after the reversal of movement from the direction of movement of the carriage 1, which is indicated by the arrow 67, the Bearing recess 83, seen in the vertical direction, lies below the bearing recess 81, the rod 75 being in the vertical position. The friction plate 39 are met in the embodiment of Figure 5 thus not only the function of a sliding element with a precisely determined Reibungsver _-. Hold, but further serves as a limiter of the Kippwine kels (3 of the Kippstabs 75. The change of the boundary wall by the friction plate 39 can again exclusively by the reversal of movement or by a combination of the effect of the inertial force which is exerted on the friction plate 39 and the rod 75 when the carriage 1 is braked and the reversal of movement. The boundary wall can even be changed completely before the time of the reversal of movement if the braking of the carriage 1 is effected in a sufficiently short time, when the rod 75 is tilted by the angle β from the position shown in FIG. 5, the combination of the carriage 1 and the print head 3 is rotated counter-clockwise about the axis of rotation 57 through such an angle that the mentioned combination ho again by 0.09 mm in the vertical direction is pressed. The displacement of the combination in the horizontal direction is negligibly small due to the relatively large distance between the axis of rotation 57 and the bearing recess 81.

It should be noted that there is a possibility of tipping angle ß of the rod 75 can not be determined indirectly by the stroke that the friction plate 39 can perform with respect to the carriage 1, but in a direct manner. In this case, the first boundary wall 65 and the second boundary wall 69 are provided with mutually opposite lugs, against which the rod 75 can rest.

Although in the described embodiment of the matrix printer the chamber 41 is completely in the carriage 1, it is possible to use a chamber which is partly in the carriage 1 and partly in the print head 3. The friction plate 39 is in the carriage 1, while the inclined plate 63 is in the print head 3. The height adjustment is carried out by a relative movement of the print head 3 with respect to the carriage 1. It should also be mentioned that the print head 3 can contain printing elements of various types which are suitable for matrix printing. For example, there is the possibility that the printing elements consist of electrodes for electrostatic printing or of ink tubes that send ink drops to the data carrier.

Finally, it should be noted that position change elements can also be used on both sides of the print head. The axis of rotation 57 does not exist. Such an embodiment offers the advantage that the carriage 1 can be made narrower.

Claims (5)

1. Matrix printer having a along a paper guide back and _{'reciprocable} combination of a carriage and a printing head thereon, a first printing position for printing character elements during a movement from left to right and a second printing position for printing character elements during a movement from the right to the left, with the drawing elements of a certain print element in the print head which are printed on the paper when the print head is moved to the right, with respect to the drawing elements of this same print element which are printed on the paper when the print head is moved to the left, in a vertical direction Direction shifted over a distance which is a part of the vertical distance between two successive printing elements in the printhead, characterized in that the combination of the carriage and the printhead is provided with a chamber in which there is a position changing element, which is in relation to these Combination by a change in the movement pulse of the print head is relatively displaceable and thus moves the print head to one print position before the pulse change and to the other print position after the pulse change. 2. A matrix printer according to claim 1, characterized in that the position changing member forms the coupling between a friction plate displaceable via a guide wall delimiting the chamber and the print head. 3. A matrix printer according to claim 2, characterized in that the position changing member is one over the friction plate and one opposite it in the chamber, with respect to the line direction and the friction plate obliquely arranged surface is rollable circular cylinder which in the first pressure position rests on a first boundary wall of the chamber and in the second pressure position on a second boundary wall of the chamber opposite the first boundary wall, the two boundary walls and the axis of the circular cylinder running parallel to one another. 4. A matrix printer according to claim 2, characterized in that the position changing member is a tilting rod which is supported at one end in the carriage and at the other end in the friction plate, the tilting angle of the tilting rod being determined by approaches for the friction plate located in the chamber is. 5. A matrix printer according to claim 1, characterized in that the chamber is in the carriage, that the guide wall delimiting the chamber is part of a fixedly arranged guide profile extending parallel to the line direction and the print head with the carriage with respect to the guide profile from first to the second printing position and vice versa about an axis of rotation which is perpendicular to the line direction.

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