GB1562852A

GB1562852A - Reproducing members for electrostatic reproduction

Info

Publication number: GB1562852A
Application number: GB4462877A
Authority: GB
Original assignee: HELL R DR ING GmbH
Current assignee: HELL R DR ING GmbH
Priority date: 1977-10-26
Filing date: 1977-10-26
Publication date: 1980-03-19

Description

(54) IMPROVEMENTS IN OR RELATING TO REPRODUCING MEMBERS FOR ELECTROSTATIC REPRODUCTION (71) We, DR.-ING. RUDOLF HELL GMBH, a German Body Corporate, of 1-3 Grenzstrasse, 2300 Kiel 14, German Federal Republic, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement:- The present invention relates to reproducing members for electrostatic reproduction, of the kind consisting of an electrode array, counterelectrodes associated with said electrode array and supply lines for the electrodes in which the electrode array consists of at least two mutually isolated rows of electrodes.

In facsimile copying, an original is scanned dot by dot and line by line in a scanning apparatus by an opto-electronic scanning member and information on the lightness or darkness of the dots is converted into an electrical image signal.

The original to be copied may be a printed or machine-written document, a hand-written text or a graphic representation.

In a reproducing apparatus the image signal controls a reproducing member which, in the case of electrostatic reproduction, consists of an electrode array and plurality of counterelectrodes. Between the electrode array and the counter-electrodes is moved a reproduction medium which is made up of a base layer of medium conductivity and a dielectric layer which is situated towards the electrode array.

The electrostatic reproduction takes place by transmitting point charges to the dielectric layer of the reproducing medium, the charges -being generated by c o r o n a discharge between an electrode and the associated counter-electrode.

On the reproducing medium is produced a pattern of electrostatic c h a r g e s which represents the information scanned from the original.

After being traced out, the latent pattern of charges is developed by applying toner material and is converted into a visible image, which is fixed by heat treatment for example.

When developed and fixed the reproduction medium forms the required copy of the original.

The electrode array of the reproducing member consists of a plurality of individual electrodes. In order to achieve high print density and high resolution in the reproduction, the construction provides for the individual electrodes to be arranged close together. At the same t i m e however an isolation interval must be observed so that the electrodes can be actuated selectively.

An electrode array of this nature preferably consists of two mutually isolated parallel rows of electrodes which extend for the entire width of the reproducing medium. The electrodes in one of the rows are arranged very precisely in the intervals between pairs of electrodes in the other row. It is necessary for the electrodes to be accurately positioned relative to one another in order when reproducing the copy to achieve a print which is of uniform density over areas and which is free from streaks and has clean outlines, that is to say a high standard of reproduction overall.

The counter-electrodes, which are arranged in a row, also extend for the entire width of reproduction. Each counter-electrode, is exactly correlated with a group of electrodes.

To produce the difference in potential required for corona discharge, the electrodes and counter-electrodes are connected to highvoltage generators. The production of the connections involved is a particular problem which exists when producing the reproducing member.

An electrode array in which the electrodes consist of individual wires embedded in sheets of synthetic resin has already been described in German Offenlegungsschrift No. 2 260227 a n d German Offenlegungsschrift No.

2261529.

In the case of this electrode array, each electrode has t o b e provided w i t h the appropriate supply lead by hand in a tedious and time-comsuming operation.

German Offenlegungsschrift No. 2 023 719 discloses a n electrode array i n which the electrodes have already been produced in the form of conductive tracks on both sides of an insulating sheet. The starting product is a so called double-sided sheet carrying conductors such as is used for printed circuits.

In the case of this electrode array the crucial disadvantage is once again that the supply leads have to be connected by hand.

Due to the large number of electrodes in an electrode array, the supply leads form a thick bundle of wires which takes up a great deal of space and is very difficult to form into shape.

Another disadvantage can be seen in the fact that with the proposed method of making connections between the electrodes and an actuating circuit, it is very time-consuming and complicated to replace the electrode array should this be necessary.

Similar problems exist with the counterelectrode arrangement.

It is an object of the invention to remove or minimise t h e disadvantages referred to above, and to provide an electrostatic reproducing member having an arrangement cf electrodes and counter-electrodes which is considerably simpIer and more economical to produce than heretofore.

Accordingly the present invention consists in a reproducing member for electrostatic reproduction of the kind described comprising: a carrier having at least two carrier sheets, which are arranged one above the other opposite the counter-electrodes and to one side of each of which the electrodes are applied and to the other side of each of which the supply lines a r e applied, both the electrodes and the supply lines being in the form of conductive tracks, said electrodes being connected to their associated supply lines through the carrier sheet; an insulating layer arranged between said carrier sheets and connected thereto, and cover sheets connected to the outer faces of the carrier sheets.

In order that the invention may be more clearly understood, reference will now be made to the accompanying drawings which illustrate certain embodiments thereof by way of example and in which: Figure 1 shows the general construction of a facsimile reproducing apparatus having an electrostatic reproducing member, Figure 2 shows an embodiment of the carrier sheets, Figure 3 shows the construction of an electrode array, and Figure 4 s h o w s a counter-electrode arrangement.

Referring now to the drawings, Figure 1 is a perspective view showing the general construction of a facsimile reproducing apparatus having an electrostatic reproducing member.

A reproducing medium 1 moves in the direction of an arrow 2 between a fixed electrode array 3 and counter-electrodes 4 opposed thereto. The reproducing medium 1 consists of a base layer of medium conductivity and dielectric layer to store point charges which in use is oriented so that it faces the electrode array 3. The advancing movement of the reproduction member 1 is produced by pairs of rollers 5 and 6. One of the rollers is driven by a motor 7. The electrode array 3 contains two rows of electrodes 8 and 9 which extend for the entire width of the reproducing medium and which are separated from one another by an insulating layer 10.

To achieve at reproduction a print of uniform density the electrodes in one of the rows are exactly aligned with the intervals between pairs of electrodes in the other row.

The working surface of each electrode is preferable square.

In a practical embodiment the reproducing medium 1 is 216 mm wide. With the standard number of eight electrodes per mm of reproduction width (proposed CCITT standard), the total number of electrodes is 1728, the electrodes being distributed evenly between the two rows of electrodes 8 and 9.

The counter-electrodes 4 likewise extend for the entire width of the reproducing medium 1. The contact face of a counterelectrode 4 is so shaped that it touches the reproducing medium 1 at two points and forms a cavity where the rows of electrodes 8 and 9 of the electrode array 3 are situated.

The electrostatic reproduction is made by transferring point charges to the dielectric layer of the reproducing medium 1. The point charges are produced by corona discharge caused by a high difference of potential between an electrode 11 and an associated counter-electrode 4.

To reproduce a line extending transversely to the direction of advance of the reproducing medium 1, selected electrodes in one row are actuated first, and then the corresponding electrodes in the other row when the charges already transferred for the line are situated along the other row.

A plurality of high-voltage amplifiers in a high-voltage generator 12 produce the high voltage required to initiate the corona discharge, these voltages being fed to the electrode array 3 along multiple lines 13 and to the counter-electrodes 4 along multiple lines 14. So that the number of high-voltage amplifiers used may be less than the total number of electrodes in the electrode array 3, the electrodes are actuated by means of a control matrix using the coincidence principle, which is described in detail in German Offenlegungsschrift No. 2 162 629 and German Offenlegungsschrift No. 1 946 815.

For this purpose the rows of electrodes 8 and 9 are divided up into m adjoining groups, each group consisting of n electrodes which are numbered serially from 1 to n. Electrodes having the same number are connected to respective high-voltage amplifiers via the control matrix, which is not seen in Figure 1, as a result of which the number of highvoltage amplifiers required is reduced from m X n to n.

The high-voltage amplifiers are selected during reproduction by means of control signals which are generated in a computer 16 by series/parallel conversion of a digital image signal which is transmitted by a scanning apparatus (not shown) along a line 15.

In what follows the construction of the electrode array 3 and of the counterelectrodes 4 will be described in detail.

The basic materials for the electrode array 3 are carrier sheets 19 and 20 as shown in Figure 2 which consist of an insulating material. On the side of the carrier sheet 19 which is visible in Figure 2 is situated the row of electrodes 8 and on the other carrier sheet 20 the row of electrodes 9, both in the form of conductive tracks. To the sides of the conductor carrying sheets 19 and 20 which are not visible (for which reason they are shown in broken lines) are applied, also in the form of conductive tracks, respective control matrices for the coincidence actuation of the electrodes 11. The axes of electrodes 11 in one row are displaced relative to those in the other row by half the distance between two adjoining electrodes. The conductive tracks are preferably square in cross-section.The cross-sectional faces of the electrodes 11 which border on the longitudinal edges 21 of the carrier sheets 19 and 20 form what will subsequently be the working face of the electrode array 3.

In the embodiment selected each row of electrodes 8 and 9 consists of 864 individual electrodes. The length of a side of the square cross-sectional face of an electrode 11 is approximately 115 mm.

For the purposes of coincidence actuation, each row of electrodes 8 and 9 is divided up into 13+ groups, containing 64 or 32 electrodes as the case may be, and each group is divided up into two equal sub-goups. Within each group the electrodes are numbered serially from 1 to 64.

Because of the extremely small dimensions involved, the conductive tracks are only indicated schematically in Figure 2 and only three groups are shown in each row of electrodes and merely the first and last electrodes of each sub-group within a group.

The electrodes 11 are connected by conductive tracks 22 to similarly numbered contact spots 23 which form electrical connections through the carrier sheets 19 and 20 to the conductive tracks 24 of the control matrix, which extend in parallel, on the reverse sides of the carrier sheets 19 and 20.

The conductive tracks 24 of the control matrix terminate at four projections 25 from the carrier sheets 19 and 20 where they form contact terminals 26.

Figure 3 shows the construction of the electrode array 3. It consists of the two carrier sheets 19 and 20, provided with conductive tracks as shown in Figure 2, the sheets lying on top of one another in such a way that the rows of electrodes 8 and 9 are adjacent to one another. Between the carrier sheets 19 and 20 is situated an insulating film 28 for the two rows of electrodes 8 and 9 which sets the distance between them. Above and below the carrier sheets 19 and 20 are mounted cover sheets 29 and 30.

All the parts may for example be bonded together under pressure. The adhesive will also be present in the spaces between the electrodes, by which means they are insulated from one another. If adhesive is suitably applied between the carrier sheets 19 and 20, the insulating film may be dispensed with. The front edge of the electrode array 3 is ground to produce a smooth, rounded-off working face 31.

The size of the cover sheets 29 and 30 is such that the projections 25 protrude from the arrangement at the sides. Socket strips (not shown) which are situated on a wiring harness, when fitted to the contact terminals 26 of the plug-in strips 25 provide an advantageous way of forming a quickly made and released electrical connection between the electrodes and an actuating circuit.

In a preferred embodiment, the carrier sheets 19 and 20 consist of a flexible material such as a thin film of epoxy resin for example.

If this is the case the plug-in strips 25 of the electrode array 3 are able to bend and can be connected to a suitably arranged socket strip belong to the actuating stage without flexible leads.

It is of course also possible to place the carrier sheets 19 and 20 on top of one another in such a way that the conductive tracks of the control matrices are adjacent to one another. In this case the distance between the rows of electrodes 8 and 9 at the working face of the electrode array 3 will be determined by the thickness of the carrier sheets 19 and 20 and of the insulating layer.

Figure 4 shows a way of arranging the counter-electrodes involving a shaped carrier sheet 34 to which a row of counter-electrodes 4 is applied in the form of conductive tracks.

The conductive track forming a counterelectrode 4 consists of a contact area 35, a neck 36, a supported area 37 and a supply line 38 which, on a projection 39, is formed into a contact terminal 40. The contact area 35 of each of the counter-electrodes 4 is shaped so as to produce two areas of contact with the reproducing medium (not shown). Where the supported areas 37 are situated the carrier sheet 34 is secured to a mounting 41. Suitably shaped springs 42 are arranged between the mounting 41 and the carrier sheet 34 and these support each contact area 35 and ensure that the counter-electrodes 4 are applied resiliently to the reproducing medium.

We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art.

A modification which will be in the scope of invention which is not illustrated but easily deducible from Fig. 3 is mounting of the layers in the same sequence -as illustrated in Fig. 3, but with the difference that the carrier plates 19 and 20 bearing the electrodes 8 and 9 are respectively mounted in an inverse position so that the carrier plates 19 and 20 contact the layer 28.

WHAT WE CLAIM IS: 1. A reproducing member of the kind described, comprising: a carrier having at least two carrier sheets, which are arranged one above the other opposite the counterelectrodes and to one side of each of which the electrodes are applied and to the other side of each of which the supply lines are applied, both the electrodes and the supply lines being in the form of conductive tracks, said electrodes being connected to their associated supply lines through the carrier sheet; an insulating layer arranged between said carrier sheets and connected thereto, and cover sheets connected to the outer faces of the carrier sheets.

2. A reproducing member as claimed in claim 1, wherein the sides of the carrier sheets which carry the electrodes face one another.

3. A reproducing member as claimed in claim 1 or 2, wherein the carrier sheets, the insulating layer, and the cover sheets are connected together by bonding.

4. A reproducing member as claimed in claim 1, 2 or 3, wherein the spaces between the electrodes are filled with an insulating material.

5. A reproducing member as claimed in any of claims 1 to 4, wherein the connection between the electrodes and the associated supply lines is in the form of throughcontacts.

6. A reproducing member as claimed in any one of claims 1 to 5, wherein the carrier sheets have projections carrying the supply lines which protrude beyond the cover sheets.

7. A reproducing member as claimed in any of claims 1 to 6, wherein the supply lines on each carrier sheet are in the form of a control matrix for the coincidence actuation of the electrodes.

8. A reproducing member as claimed in any one of the preceding claims wherein the counter-electrodes are arranged in a row opposite the electrode array, and are applied to a carrier sheet in the form of conductive tracks.

9. A reproducing member as claimed in claim 8, wherein the conductive track of each counter-electrode consists of a contact area, a neck, a supported area and a supply line.

10. A reproducing member as claimed in claim 8 or 9, wherein the carrier sheet has a projection carrying the supply lines.

11. A reproducing member as claimed in claim 9 or 10, wherein the carrier sheet is connected to a mounting at the place where the supported areas of the counter-electrodes are situated.

12. A reproducing member as claimed in claim 9 or 11, wherein each contact area of the row of counter-electrodes is so shaped as to provide at least two areas of contact with a reproducing, medium which extends in the direction of the row.

13. A reproducing member as claimed in any of the preceding claims, wherein the carrier sheets consist of a flexible material.

14. A reproducing member as claimed in claims 9, 11, 12 or 13, wherein each contact area of the counter-electrodes is supported by a spring secured to the mounting.

15. A reproducing member as claimed in claim 6 or 10, the supply lines are in the form of contact terminals on the projections.

16. A reproducing member as claimed in claim 15, wherein the connection between the contact terminals and an actuating circuit is of plug-in form.

17. A reproducing member as claimed in claim 1, wherein the sides of the carrier sheets which carry the electrodes are remote from one another.

18. A reproducing member as claimed in claim 1, wherein the insulating layer is formed by a coating of adhesive.

19. A reproducing member substantially as hereinbefore described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. mounting 41 and the carrier sheet 34 and these support each contact area 35 and ensure that the counter-electrodes 4 are applied resiliently to the reproducing medium. We wish it to be understood that we do not desire to be limited to the exact details of construction shown and described, for obvious modifications will occur to a person skilled in the art. A modification which will be in the scope of invention which is not illustrated but easily deducible from Fig. 3 is mounting of the layers in the same sequence -as illustrated in Fig. 3, but with the difference that the carrier plates 19 and 20 bearing the electrodes 8 and 9 are respectively mounted in an inverse position so that the carrier plates 19 and 20 contact the layer 28. WHAT WE CLAIM IS:

1. A reproducing member of the kind described, comprising: a carrier having at least two carrier sheets, which are arranged one above the other opposite the counterelectrodes and to one side of each of which the electrodes are applied and to the other side of each of which the supply lines are applied, both the electrodes and the supply lines being in the form of conductive tracks, said electrodes being connected to their associated supply lines through the carrier sheet; an insulating layer arranged between said carrier sheets and connected thereto, and cover sheets connected to the outer faces of the carrier sheets.