GB2057359A - Matrix printer - Google Patents

Description

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GB 2 057 359 A

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SPECIFICATION Matrix printer

5 This invention relates to a matrix printer, namely a machine which prints characters by means of an array, such as a line, of needles or other impact members selectively displaceable to imprint upon a target sheet dots or other print marks in arrays which 10 constitute the required characters.

Commonly, the impact members are included in a print head and are arranged in a straight line, and in ■use the print head moves relative to the sheet in a direction transverse such line, in stepwise fashion. 15 At the stationary positions of the print head the impact members are actuated in accord with a predetermined programme to strike the sheet through an inked tape or ribbon. The pattern of dots thus printed after a compete traverse of the printing 20 head across the sheet usually constitutes a line of characters of which the maximum height corresponds to the length of the line array of impact members.

The quality of the characters printed by such a 25 machine is limited by the size of the impact area of the portions of the impact members which strike the sheet through the ribbon. As can be seen from Figure 1 of the accompanying drawings, in which figure a needle impact area 1 is shown superim-30 posed upon a serif 2 of a character 3, the fine details of character typographic structure are severely degraded upon reproduction using such machines.

The present invention aims to alleviate this limitation and accordingly provides a matrix printer 35 having a print head for movement in use, over a target surface and including an array of impart members which are selectively displaceable toward said target surface, and, in respect of each impact member a moveable strike member on a resilient 40 carrier for transmitting impact from said impact member to the target surface.

By this arrangement the impact areas of the strike members may be made much smaller than the impact areas of the impact members to permit 45 printing of finer seraphed and other stylised type faces.

" The resilient carriers are preferably leaf springs carrying the strike members, and respective anvil members at free end portions thereof the arrange-50 ment being such that the impact members are displaceable as aforesaid to strike the respective anvil members whereby the leaf springs will flex so as to displace the strike members from rest positions to strike the target surface, preferably through the 55 intermediary of an inked ribbon or other web, and thereafter reflex to withdraw the strike members toward their rest positions.

Preferably, the leaf springs project inwardly in a comb-like manner, interdigitated attheirfree ends, 60 from opposite sides of a substantially rectangular frame, with which they are integrally formed, so as to dispose the strike members in a row in register with the impact members.

An embodiment of the invention will now be 65 described by way of example with reference to the accompanying drawings, in which:

Figure 1 illustrates a disadvantage in character reproduction using matrix dot printers;

Figure 2 illustrates an impact assembly in a print head of a matrix printer according to the present invention, and

Figure 4 illustrates a leaf spring assembly for use in a matrix printer according to the present invention.

In Figure 2 reference numeral 5 designates the end portion of one of an array of axially displaceable impact members in the form of needles, this portion projecting outwardly of a print head body 4. It is this needle end which hitherto has struck the target sheet 6 through an inked ribbon 7 with an impact area 1 as in Figure 1. It has been proposed, to avoid the aforesaid limitations, merely to reduce the impact area to a smaller dot or other shape by shaping the projections 5. However, this would lead to increased wear of the impact projection if this were to be significantly reduced in area and would cause problems in manufacture as well as wear if the needle ends were shaped to give optimum results in type-face reproduction.

The impact assembly of Figure 2 therefore includes a leaf spring 8 which carries at or adjacent to its free end an anvil 9 to be struck by the needle 5, and on the opposite side, facing the ribbon 7, a strike member 10 shaped to present a striking surface of smaller or different shaped area than the impact area of projection 5 to strike the target sheet through ribbon 7. When the anvil 9 is struck, the spring 8 flexes and the strike member 10 advances towards the target sheet. After striking the sheet through the ribbon, the strike member 10 is withdrawn toward the rest position of Figure 2 by reflexing of the spring 8.

A plurality (for instance nine) of needles 4 are arranged in a straight line projecting normally to the plane of the drawing in Figure 2, each linearly displaceable in a direction parallel to arrow 11.

Figure 3 illustrates a leaf spring assembly 12 including a plurality (nine, where nine needles are used) of leaf springs 8, one for each needle 4. The leaf springs are formed integrally with, and project generally inwardly in comb-like mannerfrom opposite sides of a rectangular frame 14. The springs are independently flexible and are interdigitated at their free ends so that their end portions, carrying anvils 9 and strike members 10 align (along line X-X transverse the elongate axes of the leaf springs) with the needles 4.

The spring assembly may be made from materials such as a sheet of nickel beryllium copper or pen steel, either the anvils and strike members being electrolytically deposited thereon in a suitable wearing material, such as hard nickel or the entire spring, striking and anvil members being photo-etched from a single sheet of the aforementioned materials with the striking and anvil surfaces plated with a suitable hard wearing material such as chromium. The sizes and shapes of the striking surfaces of the print members 10 are selected to achieve the required character detail formation. They may simply form smaller dots than before, or may comprise thin bars.

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GB 2 057 359 A

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In the case where the print head includes two parallel rows of needles, the leaf spring assembly will include a suitable arrangement of leaf springs to provide resilient mounting fortwo corresponding 5 rows of anvils and strike members. The strike members of one such row may have strike surfaces comprising thin horizontal bars while those of the other row have strike surfaces comprising thin vertical bars. This would permit the formation of fine 10 horizontal and vertical character strokes and serifs.

The leaf spring assembly is readily detachable from the print head and replaceable when the strike surfaces become worn, and/orto permit change of typeface.

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Claims (12)

1. - A matrix printer having a print head for movement in use, over a target surface and includ-20 ing an array of impact members which are selectively displaceable toward said target surface, and, in respect of each impact member a moveable strike member on a resilient carrier for transmitting impact from said impact member to the target surface. 25

2. A matrix printer according to claim 1 wherein each strike member has a strike surface to strike the target surface, over an area which is smaller than and/or differently shaped the area of an impact surface of the respective impact member. 30

3. A matrix printer according to claim 1 or claim 2 wherein each resilient carrier carries an anvil member, and is so positioned that the respective impact member is displaceable as aforesaid to strike said anvil member whereby the carrier will flex so as to 35 displace the strike member from a rest position to strike the target surface, and thereafter reflex to withdraw the strike membertoward said rest position.

4. A matrix printer according to any preceding 40 claim wherein each resilient carrier is a leaf spring.

5. A matrix printer according to claim 4 wherein the strike members are carried at terminal portions of the respective leaf springs.

6. A matrix printer according to claim 5 wherein 45 the leaf springs project generally inwardly of a frame member, the said terminal portions and strike members being disposed in an array corresponding to and registering with the array of impact members.

7. A matrix printer according to any preceding 50 claim wherein the impact members are arranged in at least one row.

8. A matrix printer according to claim 6 and claim 7 wherein said frame is rectangular and said leaf springs project as combs from a pair of opposite

55 sides of the frame to interdigitate the terminal portions whereby the strike members are disposed in a row which is substantially parallel to and central between said pair of opposite sides of said frame.

9. A matrix printer according to any of claims 6 to 60 8 wherein the leaf springs are formed integrally with said frame.

10. A matrix printer according to any preceding claim wherein the strike members are formed upon the respective resilient carriers by electrodeposition.

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11. A matrix printer according to any preceding claim and including means for positioning an inked web between the strike members and the target surface, so that the target surface will be struck by the displaced strike members through the intermedi-70 ary of the inked web and will thereby be imprinted to the shapes, dimensions and arrangements of the displaced strike members.

12. A matrix printer having a print head substantially as hereinbefore described with reference to 75 and as illustrated in Figures 2 and 3 of the accompanying drawings.

Printed for Her Majesty's Stationery Office by Croydon Printing Company Limited, Croydon, Surrey, 1981.

Published by Hie Patent Office, 25 Southampton Buildings, London, WC2A 1AY, from which copies may be obtained.