JPS5839479A - Platen - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to high speed printer platens, and more particularly to type belt printer platens.

In current line impact printers with rotating type carriers, the back side of these type carriers is supported by a platen for impact by the printing hammer. The effects of forces that occur during the printing process cause material wear on both the platen and type carrier. Such wear always results in a deterioration of print quality.

In West German Patent No. 2753 132, a line printer is described in which a copper belt with types protruding from the plane is used as a type carrier. During the printing process, the type belt is supported on the back side of the belt by a bar that acts like a platen.

The wear on this bar caused by the movement of the steel belt and the forces imposed by the printing hammer is reduced by the use of a bearing material, specifically lead bronze, in the impact area of the platen. In a special embodiment, the body of the platen has multiple impact areas and only one of these impact areas is used at a time. however,
The use of such flat, flat platens results in poor print quality and t
ru.

In European Patent Application No. 80104963.6:
A rotating roller type platen is described and used in a type belt printer. This type belt is driven very slowly by a geared motor to prevent the rotating type belt from scratching the roller and to ensure that this roller is worn evenly over its outer circumference. .

However, a rather small roller diameter results in undesired abrasive and deforming effects on the type carrier, as will be explained in more detail.

In order to eliminate the inherent disadvantages of flat platens and cylindrical platens, it is an object of the present invention to provide an improved platen for achieving better print quality.

FIG. 1 is a partial cross-sectional view of a flat platen 1. FIG. The type belt 2 is used as a type carrier and raised characters 6 are formed from this type belt by etching. This type of belt (made of steel) moves perpendicularly out of this plane as it is pulled past the flat platen 1. The ink cloth 4 and the record carrier 5 are arranged in front of the type belt 2. When the printing printer 6 prints a character 6 on the type carrier belt 2 in the direction of the arrow, the type carrier belt 2 is pressed against the platen 1 for a short time. The use of flat platens has two significant drawbacks.

Specifically, in high speed printers, the air cushion between the type belt and the platen cannot dissipate quickly and sufficiently, resulting in the characters' being poorly printed.

Due to manufacturing tolerances and wear of the hammer, guide, and type section, the hammer surface does not completely strike the parallel flat platen, resulting in density variations in the printed characters.

(A flat platen, however, has the advantage that the least pressure per unit area is between the type belt and the platen.) On the other hand, a roller-type platen has the advantage that the much smaller radius of the printing roller is located between the type belt and the platen. It has the disadvantage that it only allows approximately linear contact between the roller and the roller, resulting in high printing tensions. High printing tensions lead to high wear and similar plastic deformation of the type carrier. The roller drives itself vertically into the type carrier, so that in the worst case the characters can fall out of the type carrier.

In order to eliminate the disadvantages of the flat grates and roller-shaped platens mentioned above (with relatively small roller diameters), the present invention provides an arcuate roller section in which a large radius of curvature is applied to the roller.

The result is a circular polygonal platen, hereinafter referred to as a CP platen. A partial cross-section of the graten is shown in FIG. This CP platen has four impact areas 8.9.1o and 11 and an axis 12 and rotates around this axis. As a result, different impact areas can be adjusted. This adjustment involves partially rotating the platen after one impact area is worn out so that a new impact area is positioned for the printing process. The individual impact areas are convex, the radius R associated with these arcs is much larger than the radius r associated with the imaginary cylinder platen, and the individual end points of the impact area 8.9.10 camber 11 are It is positioned on the virtual circumference of this platen.

Rotation of the platen may be accomplished with standard ratchet gears, either manually or automatically. FIG. 3 is a partial sectional view showing a specific embodiment of the female CP platen 16. As shown in FIG. The CP platen has an annular, laterally facing surface made of steel and has a front plate 19 mounted at each end of this surface. Each front plate has shaft hole 1
Seven rotatable shafts (not shown) extend through the shaft holes.

A flange permanently fixed to the rotatable shaft 1 is connected by screws or the like to a hole 18 in the front plate of the platen, so that the platen can be used in the event that a new impact area is not positioned for the printing process. If so, a force is applied so that it rotates with this axis. For example, the shaft is driven by a regular ratchet gear. To simplify the explanation, the individual impact surfaces are shown in 15-1 and 16-1.
Only two are shown and take the form designated platen bars 15 and '16. The bottom of such a platen bar has an essentially rectangular cross-section and its top is circularly shaped. In a specific embodiment, the radius R associated with this arc may be 150 mm (and the outer diameter of the cylinder may be approximately 25 mm). A recess 26 is milled into the cylinder ring and Into these recesses the bottoms of the platen bars are glued.These platen bars are advantageously made of a material that reduces the wear of the type belt passing through this platen.

Bronze for bearings has been very successful for this purpose, as explained in West German Patent No. 1 m', i No. 27 53 132. FIG. 4 is a perspective view of the CP platen 16 of FIG. 6 in accordance with the present invention. The drive shaft extending through the platen is shown as 20 and the platen bar as shown in FIG. 6 is shown as 15 and 16. Platen
The bar consists of a steel carrier 21 and a bearing material 22 in the impact area. For clarity and simplicity of explanation, illustration of the separate platen bar is omitted. The driving means for the rotating shaft 20, which has already been described, is also omitted.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a flat platen; FIG. 2 is a cross-sectional view of a platen of the present invention having a portion of the roller that is essentially roller-shaped and whose radius of curvature is much larger than the radius of a hypothetical cylindrical printing roller. , 2 and 6 are cross-sectional views of the platen of the present invention that can be adapted to a printer, and FIG. 4 is a perspective view of the platen of the present invention as shown in FIG. 6. 13...Platen, 15.16...Platen
Bar, 15-1.16-1...Impact area, 19...
...Front plate, 20...shaft.

Claims (1)

Claims: A platen rotatable about an axis with several impact surfaces, the impact surfaces having a radius of curvature, the radius of curvature being between the axis of rotation of the platen and the outer peripheral surface of the platen. A platen characterized in that the maximum distance between the platens is greater than the maximum distance between the platens.