US3908191A

US3908191A - Apparatus for electrostatic printing with movable electrodes

Info

Publication number: US3908191A
Application number: US406705A
Authority: US
Inventors: Gabor Forgo; Erwin Meyer; Karl Moser
Original assignee: Zellweger Uster AG
Current assignee: Zellweger Uster AG
Priority date: 1971-08-16
Filing date: 1973-10-15
Publication date: 1975-09-23
Anticipated expiration: 1992-09-23

Abstract

An apparatus for producing printed images by electrostatic printing techniques, comprising an electrode arrangement and a counterelectrode for forming a latent electrostatic charge image at a carrier disposed between said electrode arrangement and said counterelectrode, and means provided for one of said electrodes for enabling relative movement in alternate directions with movement components essentially parallel to the plane of the carrier between the electrode arrangement responsible for producing the latent electrostatic charge image and the carrier intended to receive the latent electrostatic charge image.

Description

United States Patent n 1 Forgo et 31.

( 1 3,908,191 1 Sept. 23, 1975 APPARATUS FOR ELECTROSTATIC PRINTING WITH MOVABLE ELECTRODES Inventors: Gabor Fargo; Erwin Meyer; Karl Moser, all of Zurich, Switzerland Zellweger Uster AG, Uster, Switzerland Filed: Oct. 15, 1973 Appl. No.: 406,705

Related US. Application Data Division of Ser. No. 272,067,1uly 14, 1972, Pat. No. 3,875,320.

Assignee:

Foreign Application Priority Data Aug. 16, 1971 Switzerland 12104/71 US. Cl. 346/74 ES; 178/66 A; 346/74 .1 Int. Cl. G03G 15/048 Field of Search 346/74 ES, 74 E, 74 MD;

References Cited UNITED STATES PATENTS 11/1963 Morley 346/74 MD 2/1972 Stringer et al 346/74 ES 3,686,678 8/1972 Robbins et a1. 346/74 ES 3,717,880 2/1973 Howell 346/74 ES 3,787,722 1/1974 Hatsell 346/74 ES OTHER PUB LlCATlONS IBM Tech. Disc. Bull., Vol. 13, No. 10, p. 3117, March 1, 1971, Contact Electrostatic Printing, McCurry.

Primary Examiner-Bernard Konick Assistant Examiner-Jay P. Lucas Attorney, Agent, or Firm-Werner W. Kleeman [57] ABSTRACT An apparatus for producing printed images by electrostatic printing techniques, comprising an electrode arrangement and a counterelectrode for forming a latent electrostatic charge image at a carrier disposed between said electrode arrangement and said counterelectrode, and means provided for one of said electrodes for enabling relative movement in alternate directions with movement components essentially parallel to the plane of the carrier between the electrode arrangement responsible for producing the latent electrostatic charge image and the carrier intended to receive the latent electrostatic charge image.

23 Claims, 7 Drawing Figures US Patent Sept. 23,1975 Sheet 1 of 5 3,908,191

Fig.1

US Patent Sept. 23,1975 Sheet 2 015 3,908,191

Fig. 4

US Patent Sept. 23,1975 Sheet 4 of5 3,908,191

US Patent Sept. 23,1975 Sheet 5 of5 3,908,191

APPARATUS FOR ELECTROSTATIC PRINTING WITH MOVABLE ELECTRODES CROSS-REFERENCE TO RELATED CASE This is a divisional application of our commonly assigned United States application Ser. No. 272,067, filed July I4, 1972, now US. Pat. No. 3,875,320, granted Apr. 1, 1975.

BACKGROUND OF THE INVENTION The present invention relates to a new and improved apparatus for electrostatic printing.

The invention is particularly concerned with a process for electrostatic printing in which a latent electro-' static charge image is produced at a carrier having a very high-ohmic layer by a discharge process from an electrode arrangement neighboring the carrier, wherein the electrostatic charge image subsequently is developed according to known techniques. These procedures are known and equipment for the performance thereof have been also described in publications. Although such known techniques are extremely outstanding as concerns the speed of their capability of producing the printed image and also as concerns their speed as concerns the variation possibilities of the printed images produced thereby, as such techniques are employed in different fields of application, such as for instance the conversion of digital computer output signals into clear text and the like, still they are nonetheless not suitable for the production of certain type of printed images. In particular, they are not suitable for instance for the production of printed images wherein the line traces or surface elements thereof, depending upon the configuration of the printed image, are disposed close to one another in such a manner that no gaps or spaces appear therebetween. This situation arises, for instance, in the case of code or coded images, hereinafter simply referred to as code images, as such are employed for example for marking articles, especially articles of sale.

Such code images which, for instance, can be in the form of a beam code, a checkerboard-like code pattern, a ring structure or the like, are read-out for evaluation purposes by means of a photoelectric reader. The thus obtained electrical pulse sequence or train then corresponds to the sequence oflight and dark locations of the scanned code image. Since the light spot employed for photoelectric scanning must possess very small dimensions, for instance fractions of a millimeter, in order to realize high definition or resolution, the aforementioned gaps or spaces between successive black code elements at the code image can produce erroneous pulse sequences. In order to prevent such type defective pulses or erroneous pulse gaps at the pulse train of the photoelectric reader it is necessary that the line traces or surface elements of the code image to be read-out closely follow one another. This is not so in the case of known electrostatic printing equipment destined for alpha-numerical characters.

SUMMARY OF THE INVENTION Accordingly, it is a primary object of the present invention to provide a new and improved apparatus for electrostatic printing in which the drawbacks of the state-of-the-art proposals no longer occur and wherein it is possible to carry out printing of the surface cle' merits or the like of the printed image in a manner such that they follow one another in succession without intermediately disposed gaps or spaces.

Yet a further significant object of the present invention relates to an improved apparatus for electrostatic printing allowing for the production of clearly discernible electrostatic printed images in a highly reliable, accurate and efficient manner, so that read-out of such images is possible without error.

Now in order to implement these and still further objects of the invention, which will become more readily apparent as the description proceeds, the process of this development for the production of printed images according to electrostatic printing techniques is manifested by the features that at least during a portion of the time-span when there is formed at a carrier a latent electrostatic charge image by virtue of an electrical discharge operation emanating from an electrode arrangement, there is carried out between the electrode arrangement and the carrier relative movement in alternate directions with movement components essentially parallel to the plane of the carrier.

As already indicated above, the invention of this disclosure is particularly concerned with an improved apparatus for the performance of the aforementioned process and which is generally manifested by the features that there is provided a guide arrangement for the aforementioned electrode arrangement and/or the aforesaid carrier or the counterelectrode serving as its support, this guide arrangement allowing for a relative movement in alternate directions with movement components substantially parallel to the plane of the carrier between the electrode arrangement responsible for the production of the latent electrostatic charge image and the carrier provided for the reception of such latent electrostatic charge image.

The invention is also concerned with products, and particularly labels produced in accordance with the aforementioned process, and the use of the thus produced label products for marking articles, especially articles of sale.

The terms *carrier" or label" as used in the context of this disclosure, are not to be considered in a limiting sense, and in fact are intended to conveniently denote almost any type of printable matter suitable for the purposes of the invention at which an image can be formed by electrostatic printing. Similarly, the term article of sale is used broadly to cover not only articles which are actually sold, but any type of article, whether sold or not, and intended to be identified by such label.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be better understood and objects other than those set forth above, will become apparent when consideration is given to the following detailed description thereof. Such description makes reference to the annexed drawings wherein:

FIG. 1 is a schematic electrical circuit diagram of a first exemplary embodiment of the invention;

FIG. 2 illustrates a code image in the form of a beam code;

FIG. 3 illustrates a code image having a checkerboard-like pattern;

FIG. 4 illustrates a code image in the form of a ring structure;

FIG. 5 illustrates details of the mechanical construction of an embodiment of the invention in side elevation;

FIG. 6 illustrates in plan view portions of the arrangement of FIG. and

FIG. 7 schematically illustrates an embodiment of electrostatic apparatus in its entirety.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Prior to describing the exemplary embodiments of the invention on the basis of the drawings, there will initially be considered more fully the basic principles of this developement.

In the practice of the present invention there is initially produced by an electrical discharge a latent electrostatic charge image which corresponds to the printed image to be produced, this electrostatic charge image being subsequently developed, for instance dry developed by means of a so-called magnetic brush for the application of a toner. What is considered to constitute a novel aspect as concerns the present invention relates to the particular manner of producing the latent electrostatic charge image. Such latent electrostatic charge image is produced as a consequence of a discharge phenomenon which occurs between an electrode arrangement and a counterelectrode at a carrier, e.g., a label having a relatively high-ohmic layer and which is arranged in the space or region between the aforementioned electrode arrangement and counterelectrode. A discussion of the general technique of producing such electrostatic images can be found, for instance, in the publication known as Taschenbuch der Nachrichtenverarbeitung, Karl Steinbuch, Second Edition, 1967, Springer Publishers of Berlin/Heidelberg- /New York, Library of Congress Catalogue Card No. 67-2l079, pages 696 et seq, FIGS. 5.7/5 and associated text.

By means ofa selector, the different individual electrodes of the electrode arrangement have applied thereto different potential so that there can be produced at a neighboring carrier a latent electrostatic charge image possessing a predetermined structure corresponding to the electrode arrangement and the voltage applied thereto.

The electrode arrangement and the individual electrodes thereof responsible for the production of a charge image of a predetermined configuration and which are to have the voltage applied thereto are connected with one pole of a voltage source through the agency of an external current circuit which contains the selector (discussed in the aforementioned publication) for the electrostatic charge image to be produced. The counterelectrode is correspondingly connected with the other pole of the voltage source. Depending upon the desired polarity of the electrostatic charge image to be produced which, in turn, is dependent upon the polarity of the subsequently employed developer, the electrode arrangement is connected with the positive or negative pole of the voltage source. There can be employed a purely direct-current voltage or a pulsating direct-current voltage. The amplitude of such voltage preferably amounts to about 450 to 1000 volts.

For current limiting purposes after initiating the discharge operation it is advantageous to design the external current circuit leading to the electrodes so as to be relatively high-ohmic. A resistance value in the order of about 1,000 kiloohms has produced good results. Those individual electrodes of the electrode arrangement from which no discharge occurs to the carrier and through such to the counterelectrode, for the purposes of producing a certain charge image of a prescribed configuration, are advantageously galvanically connected with a point of considerably lower potential that the remaining individual electrodes furnished with voltage. They are preferably galvanically connected with the counterelectrode. This galvanic coupling can be thus advantageously selected to be very-high ohmic, for instance resistance values in the order of magnitude of approximately lO megohms to megohms have produced good results.

Control of the selector for the selective coupling of each of the individual electrodes of the electrode arrangement with the voltage source or power supply can be undertaken both manually, for instance by actuating push button switches, as well as also with the aid of known electronic switching circuit arrangements.

Hence, it is possible for instance to introduce a pulse sequence characterizing certain data or information to be represented in the form of a printed image, into a shift register having a suitable number of counting stages. Following the input of the complete pulse sequence or train into the shift register, there then appear at transverse outputs of the individual shift register stages logical signals, by means of which it is possible in each instance to actuate a switch, for instance designed as a Reed relay, associated with one of the relevant stages of the shift register and the associated individual electrode of the electrode arrangement. In this way there can be produced a latent electrostatic charge image which corresponds to the aforementioned pulse sequence and the information to be expressed thereby. Following development of such electrostatic charge image, there is obtained in the aforementioned manner a code image characterizing such information. Such has been discussed more fully in, and circuitry suitable for this purpose has been disclosed in, the commonly assigned, copending United States application, Ser. No. 272,111, filed July I7, 1972, now abandoned, entitled Method For Marking Articles Of Sale And Apparatus For The Performance Of The Aforesaid Method", to which reference may be readily had.

Now with the benefit of the foregoing background in mind, and turning attention initially to the arrangement of FIG. 1, there is shown therein a principal electrical circuit diagram of a first exemplary embodiment. An electrode arrangement 1 possesses N-number of individual electrodes E, E individually connected in insulated fashion to a base plate 2. Leading from each individual electrode E, E is a conductor L, L to each pole of a switch S, S The relevant other pole of each such switch is connected to a conductor 3 which leads via a resistor 4 to a pole 5, for instance the negative pole of a suitable voltage source 6. This voltage source 6 has a terminal voltage U of, for instance, 750 volts direct-current. The other pole 7, in this instance the positive pole, of such voltage source 6, is connected through the agency of a conductor 8 with a counterelectrode 9 spaced at a distance d from the electrode arrangement 1. In the intermediate space d between the pair of

electrodes

1 and 9 i.e, the electrode arrangement I and the counterelectrode 9 there is located a carrier 10 for reception of the latent electrostatic charge image. Carrier 10 is advantageously snugly or tightly disposed upon the counterelectrode 9. Electrode arrangement I is mounted in a guide arrangement which has not been particularly illustrated in FIG. I, but will be discussed more fully hereinafter in connection with FIGS. 5 and 6, and in such a manner that it can be displaced parallel to the plane of the carrier 10.

The switches S, S can be manually actuated by push buttons or keys or, as already mentioned, there can be provided for this purpose for instance Reed relays or the like which can be controlled by means of an electronic control circuit. These switches S, 8,, together with a possibly provided control circuit form a selector circuit for the selection of the individual electrodes of the electrode arrangement to which voltage is to be applied for producing a certain configuration of the electrostatic charge image. In this regard refer ence is again made to our aforementioned copending US. application Ser. No. 272,l l I, now abandoned, filed July I7, 1972.

Now during the production of special printed images, especially coded images, according to the described procedures, certain difficulties arise.

In order to better understand the invention, there will now hereinafter be explained the particular problems which should be solved during the printing of such code images or characters. FIGS. 2, 3 and 4 illustrate therein different exemplary types of code images as such can be employed for instance for the marking of different types of articles or objects. FIG. 2 shows a beam-type code, FIG. 3 a checkerboard type code image, and FIG. 4 a code image having a ring structure, for instance formed of a series of concentric rings or otherwise. Of course, other configurations of the code images can be obviously employed without departing in any manner from the scope and teachings of the invention. By means of these code images it is possible to portray significant information, such as for instance the article number of the relevant goods, the price and other sales data in binary fashion. A black surface element, that is to say, a beam, square or ring, can for instance portray the binary value I and a white surface element of similar configuration can signify the binary value 0. It is possible for both black and white surface elements to directly follow one another. For the automatic electrooptical reading of such coded images, a light beam is delivered in known manner parallel to or in the indicated direction of the arrow or arrows across the code image and the periodically reflected light is converted by a photoelectric transducer into a sequence of electrical pulsesv The technique of reading-out the code characters or coded markings constitutes subject matter of other applications assigned to this assignee and is not necessary for the understanding of the underlying concepts of this development and therefore will not be considered in any greater detail herein.

Yet is is to be mentioned that for the purpose of avoiding erroneous reading or read-out results, it is necessary that between directly following or successive black surface elements, in other words, for instance directly successively following black surface elements which represent a binary value 1, there does not occur any white gaps or spaces since such could at least briefly simulate a binary value 0. This problem does not arise in alpha-numerical representations because in that situation the individual characters are anyway separated from one another by a more or less wide gap.

The individual electrodes E, E (FIG. 1) of the electrode arrangement I required for producing one of the aforementioned code images or its surface element respectively, considering the normally small spacing d, of, for instance, several tenths of a millimeter between such individual electrodes E, E, of the electrode arrangement l and the carrier 10, according to experience which has been gained with the known prior art equipment must be chosen to be approximately of the same size as the surface element of the latent electrostatic charge image which is to be produced and the code image which should be recognized following development thereof. If it is desired to be able to use all of the surface elements of the code character in a random sequence, thus for instance the binary character sequence 0000 or ill] or 010] or lOlO or Ol l0 or lOOl then it should be apparent that at least for part of the aforementioned situations there must be produced in direct succession black surface elements, but for another part of the aforementioned situations there must be produced at the same location different characters, in other words black or white characters. Since for initiating the discharge required for the formation of the electrostatic charge image only those individual electrodes which are associated with the black surface elements of the code image are to be connected with the voltage power source, it should be recognized that between the individual electrodes E, E there must be provided an insulation which is sufficient for the full voltage, for instance approximately 750 volts. Since, however, according to what has been previously stated the individual electrodes are to be chosen to be approximately of the same size as the surface elements of the electrostatic charge image to be produced or the code image respectively, it should be apparent that in order to apply a sufficient insulation between the individual electrodes there is just not available the necessary space.

Moreover, even if for instance there is required and used an insulation of, for instance, only 0.2 millimeters, then still such results in the fact that between the surface elements of the electrostatic charge image gaps or spaces would appear which, after developing of the code image would produce white gaps or spaces between directly successively following black surface elements. These white gaps or spaces could, however, render questionable the reliable electro-optical read-out of the code image.

Now according to an advantageous manifestation of the invention and for the purpose of overcoming the aforementioned problem, the electrode arrangement 1 is formed of individual electrodes E, E which possess a considerably smaller dimension in the read-out direction or read-out directions of the code image produced thereby than the surface elements of the electrostatic charge image or code image which is to be produced by such electrode arrangement. The width of the indiviudal e ectrodes can thus, for instance, amount to approximately one-half or one-third of the surface ele ment at the charge image or code image which is produced by the individual electrodes. Now in order to be able to obtain surface elements of the full width at the charge or code image, notwithstanding the use of such small individual electrodes, it is contemplated to carry out a desired displacement, for instance between the electrode arrangement 1 and the carrier 10 for the latent electrostatic charge image, at least during a portion of the time when such charge image is produced, and this displacement is undertaken essentially in the direction of the desired increase in size of the relevant surface element. Moreover. this displacement is advantageously undertaken in alternate directions. This displacement movement can, for instance, be carried out in the form of a to-and-fro movement if it is desired to form a code image of the type depicted in FIG. 2. In the event it is desired to form a code image of the type depicted in FIG. 3 and if such code image is read-out in the lengthwise and transverse directions, then, there is employed a lengthwise and transverse displacement during the production of the charge image. n the other hand, if it is desired to produce a code image of the type depicted in FIG. 4, then it is advantageous to perform an eccentric circular movement in order that the rings are increased in size to the full desired size or width at each location. Preferably, there is not only employed a single to-and-fro movement or circular movement during production of the charge image, rather the relative movement which is carried out between the electrode arrangement and the carrier is repeated a number of times. The amplitude of the aforementioned relative movements can be advantageously selected so as to be even slightly larger than is absolutely necessary for producing the full nominal surface element width. By virtue of this feature it is possible to realize a slight overlapping of neighboring black surface elements, so that possible tolerances of the apparatus and/or those of the discharge operations can be compensated.

Since what is significant is the relative movement between the electrode arrangement and the carrier for the charge image or counterelectrode the apparatus and carrying out this technique can be designed, for in stance, such that the carrier is stationary and only the electrode arrangement I is displaced or vice versa, or in fact both the electrode arrangement and the carrier for the charge image can be displaced.

Owing to the aforementioned measures there is not only brought about a widening of the surface elements, but even more so the uniformity of the charge distribution within the individual surface elements of the charge image is considerably improved. In this way there is achieved the effect that the code image obtained after developing the charge image possesses a considerably better blackening of the surface elements than would have been possible without the aforementioned relative movement between the electrode arrangement and the carrier. This is of particular importance for the purpose of producing code images, since a uniform blackening of the black surface elements provides an improvement in the read-out integrity of the code image.

In FIG. 5 there is disclosed in side elevational view the mechanical construction of an exemplary embodiment of the invention, and in FIG. 6 there is disclosed in plan view portions of the arrangement of FIG. 5. In all figures corresponding components have been designated by the same reference characters.

A shaft or axle 13 is rotatably mounted at a carrier 12 which is rigidly secured to the entire frame or housing of the apparatus. The shaft 13 carries a belt pulley or pulley disk 29. Pulley disk 29 can be driven by means of a schematically indicated belt 30, and thus, shaft I3 can be rotatably driven by means of a drive motor 32 with the aid of the pulley disk 31 seated upon drive shaft 32A. The belt 30 drivingly connects pulley disk 29 with the pulley disk 31.

Additionally, a holder mechanism, generally indicated by reference character 22, for the electrode ar rangement 1 (FIG. 1) is secured to shaft 13. Opposite the electrode arrangement I there is located at a certain spacing d the counterelectrode 9. Through this space or gap which possesses the height d there may be continuously or intermittently drawn. by means of suitable feed mechanism and particularly shown in FIG. 5 but like the feed mechanism 122 of FIG. 7 to be discussed later, the carrier 10 for the latent charge image which is to be imprinted thereat. The counterelectrode 9 is advantageously provided with bores 23 which are connected via a pipe conduit 24 with a suitable controllable vacuum device 240 or other source of negative pressure for instance. In this way, and during the production of the electrostatic charge image, and owing to the action of the vacuum acting at the underside of the carrier 10, this carrier 10 is fixedly retained in its momentary position against the counterelectrode 9. With this exemplary embodiment given purely by way of illustration. both the carrier 12 as well as the counterelectrode 9 are rigidly connected in position at the entire frame or chassis of the apparatus. Further, if desired, a suitable carrier hold-down mechanism, such as the schematically illustrated electromagnetically actuated clamping mechanism 250 can be provided, as indicated in FIG. 5.

It is now to be assumed that with the apparatus according to the embodiment under consideration, code images of the type depicted in FIG. 4 are to be printed. The individual electrodes E, E possess substantially semicircular-shaped configuration. They can be arranged for instance according to the technology of printed circuits, for example, upon an epoxy glass fiber plate. In order to increase the wear resistance they can be galvanically finished, for instance provided with a hard gold or rhodium coating.

The width of the individual ring-shaped electrodes E, E is selected in consideration of the required insulation therebetween, thus for instance amounts to only 0.2 millimeters, whereas the spacing to the neighboring individual electrodes for instance can amount to 0.8 millimeters. In order to increase or widen the surface elements of the electrostatic charge image and the code image formed following development of such electrostatic charge image, the electrode arrangement 1 has imparted thereto and through the agency of an eccentric mechanism to be considered shortly a substantially circular-shaped displacement movement in a plane which is disposed perpendicular to the shaft 13.

To this end the electrode arrangement I is secured to a guide element 25. This guide element 25 possesses a central bore 25A in which there is inserted a ball bearing 258. An eccentric pin 26A engagds with such ball bearing 258. The guide element 25 is secured against rotation about the shaft 13 in that two guide bolts 25C force fitted therewith engage with a respective bifurcated or fork-shaped stationary guide piece 27. The opening of the fork portion and the diameter of the guide bolts 25C are selected such that the guide piece 25 only carries out eccentric movements not however any rotation about the shaft 13. The eccentric pin 26A is part of an eccentric plate 26 which is adjustably mounted at a counterpiece 28 in transverse direction with respect to the shaft 13. This counterpiece 28 has a hub 28A which is secured to the lower end of the shaft I3.

With the shaft 13 rotating and depending upon the selected transverse displacement of the eccentric plate 26 at the counterpiece 28, the eccentric pin 26A carries out eccentric circular movements which are imparted via the guide piece 25 to the electrode arrangement 1 connected therewith.

Tests have further shown that through variation of the spacing d between the electrode arrangement 1 and the counterelectrode 9 or the carrier 10 for the latent electrostatic charge image located therebetween, there can be additionally realized an improved quality of the printed image. It may be assumed that this improvement is brought about by virtue of a uniform charge distribution within the line traces or surface elements of the latent electrostatic charge image.

Thus, FIG. 5 also shows for an additional exemplary embodiment an advantageous further design of the invention. According to the illustration of FIG. 6, the shaft 13 is not only mounted to be rotatable at the support or carrier 12 but can be also displaced in the direction of the double-headed arrow 11. The shaft 13 carries a flange 14 with a contact or running surface 14A. At both sides of the carrier or support 12 there is secured a respective bracket or support 15. Between both of these brackets 15 there is connected a shaft 16 (FIG. 6). A pivotal frame 17 is mounted for movement about this shaft 16, the pivotal frame 17 embodying both of the pivot arms 17A and 17B, a first connection piece 17C and a second connection piece 17D. Each of the pivotal arms 17A and 178 carries at its right-hand end a force fitted journal or

axle piece

17E and 17F upon which there is rotatably arranged a respective roller or roll 170 and 17H respectively.

Furthermore. at the carrier or support 12 there is secured an electromagnetic system 18 in such a manner that a traction or draw rod 19 comes to rest beneath the connection piece 17D. A coupling element 19A of the draw rod 19 is adjustably attached to this draw or traction rod 19. The coupling piece 19A engages at least partially about the second connection piece 17D of the pivotal frame 17. Upon excitation of the electromagnetic system 18, its traction rod 19 is retracted downwardly, so that the pivotal frame 17 lowers at the left side of the shaft 16, and at the right side thereof is raised. Owing to this movement, the rollers 176 and 17H press against the contact of running surface 14A of the flange 14. As a result, the shaft or axle 13 is displaced upwards. By means of a resilient element eg spring 20 arranged in guide housing 21 the shaft 13 is again lowered after switching-off deenergizing the electromagnetic system 18. Due to the action of the electromagnetic system and the spring 20, it is possible to thereby displace the shaft 13 in the direction of the double-headed arrow 11.

The arrangement is constructed such that at least during a portion of the time span during which the discharge operation occurs for the production of the latent electrostatic charge image at the carrier 10 the spacing d is changed. This can be realized in that there is undertaken a periodic excitation of the previously non-energized electromagnetic system 18 and a periodic non-energization of the previously energized electromagnetic system 18 during the time span in which the discharge operation between the electrode arrangement 1 and the carrier 10 and the counterelectrode 9 is to be maintained.

It would also be conceivable, however, instead of or in addition to the movement of the electrode arrangement 1, to move the carrier 10 and the counterelectrode 9 upon which the carrier 10 rests so as to realize the aforementioned change in spacing.

Now in FIG. 7 there has been schematically depicted the general overall arrangement of an electrostatic printing apparatus suitable for the practice of the invention and which has been conveniently designated in its entirety by reference character 100. This electrostatic printing apparatus is mounted upon a base plate 101. Base plate 101 carries the individual cooperating components of the equipment as will be more fully discussed hereinafter. Various ones of the individual components thereof are driven, for instance, through the agency ofa belt drive or a chain drive from a common drive motor M, as will also be explained hereinafter, and as indicated by the schematic drive connection lines 200 shown in the drawing.

The equipment under consideration will be understood to embody a supply device 102 for the markers or carriers, for instance in the form of the labels 107A to be imprinted and carried by a carrier strip foil 107, also merely referred to as a carrier foil. The supply device 102 incorporates a supply roll 104 rotatably mounted upon a fixed shaft or axle 103. Supply roll 104 is braked by a suitable braking mechanism 105, for instance through the action of a spring-loaded braking roll 105a acting upon the periphery of supply roll 104, in such a manner that the carrier foil strip 107 which moves over and away from a deflecting roll 106 can be tautly withdrawn from the supply roll 104.

The carriers to be imprinted, for example the labels 107A, are applied to the carrier foil strip 107 at a certain spacing from one another. Carrier foil strip 107 may constitute an impregnated paper strip, a paper strip with a metallic coating applied thereto by vapor deposition or otherwise, or such carrier foil strip can comprise a metallic foil strip. These labels 107A may advantageously be equipped with a self-adhering layer or coating, as schematically indicated at 107', such that they adhere to the carrier foil strip 107 with just such intensity that they can be conveyed thereon through the printing apparatus without prematurely falling-off such carrier foil strip 107 during transport. Yet it would also be possible to employ a carrier foil strip which itself has an adhesive layer and at which there is adhesively applied the labels which themselves are not adhesive, it should be understood that the invention is not generally restricted to any specific type of carrier foil strip and electrostatically printable label, since the practice of the particular development of the invention disclosed herein affords the use of many different possibilities for such carrier foil strip and labels. By way of completeness it might be indicated that suitable constructional forms of carrier foil strips and markers (labels) to be imprinted adhering thereto have been disclosed, for instance, in the commonly assigned, United States application Ser. No. 225,l l l, filed Feb. 10, 1972, now abandoned, and entitled Laminated Papers", listing as the inventor Arnold Hofer, and also in the commonly assigned United States application, Ser. No. 263,671, filed June l6, I972, now abandoned, entitled Laminated Article" and listing as the inventor Walter Strohschneider to which reference can be readily had.

Irrespective of the type of carrier foil strip or label which is employed, the carrier foil strip 107 is then caused to travel through a suitable control mechanism 108 of a strip feed mechanism 122. Although the invention is not intended to be limited to any specific construction of control mechanism 108, it can for example contain means, such as photoelectric means 109, a light barrier for instance, acted upon by the labels 107A ad hering to the carrier foil strip 107. The labels 107A are either blank, that is non-printed, or they can already contain imprinted thereon a pre-printed text, common to all of the labels, for instance data pertaining to a company, or pre-printed subject matter for the data pattern or the like which later is to be electrostaticaily imprinted, Moreover, special markings of such pre printed matter or the edge of the labels themselves could be conceivably employed as criteria for triggering operation of the photoelectric means 109.

The feed mechanisms 122 may be controlled in any suitable manner such that, for instance, owing to the output signal of a conventional article weighing or balance device having an automatic data output, or a keyboard arrangement, it can be placed into operation, whereby it is subsequently again brought to standstill by the control mechanism 108 as soon as the next successive label at the carrier foil strip 107 has assumed the same position as the preceding label prior to plac ing into operation such feed mechanism. Details of a balance and keyboard arrangement for obtaining desired output signals have been disclosed in the aforementioned commonly assigned, United States application, Ser. No. 272,111, filed July 17, 1972, now abandoned, entitled Method For Marking Articles Of Sale And Apparatus For The Performance Of The Aforesaid Method, Thus, the balance and/or keyboard arrangement has been simply designated by reference character 210 and its connection line with the feed mechanism by reference character 220. As also disclosed in detail in such application the balance and/or keyboard arrangement 210 is connected with a suitable selector control circuit 230 for selectively controlling given electrodes of the electrostatic printer 112 in ac cordance with output signals from the unit 210 and characterizing significant information about the article to be marked, so as to produce a desired electrostatically charged image at the label. After departing from the control mechanism 108, the carrier foil strip 107 together with the thereon adhering labels 107A, travels over a further deflecting roll 110 through a slot 110a beneath a guide plate 111 of the electrostatic printer or printing mechanism 112. The construction and mode of operation of the electrostatic printer 112 has already been described in conjunction with FIGS. 1, and 6.

At this point it is mentioned that owing to stepwise actuation of the feed mechanism 122, a label 1078 which is in transit is brought into a predetermined position as a gap or slot 50 between the electrode arrangement 1 and the counterelectrode 9. By applying a suitable voltage, for instance 750 volts, between the components of the electrode arrangement 1 and the counterelectrode 9 an electrical discharge occurs therebetween, so that a latent electrostatic charge image is produced upon label 1078.

Now the feed mechanism 122 further advances the carrier foil strip 107, whereupon such travels over a sharp deflecting edge or turning location 113 and other further deflecting rolls 115, 116, 117, then about a feed roll 118 and a further deflecting roll 119. The indexing of the feed steps and the spacing of the individual labels 107A upon the carrier foil strip 107 are selected so as to be of a magnitude sufficient that, on the other hand,

the label which has now been provided with the latent electrostatic charge image, owing to its greater stiffness in contrast to the carrier foil strip 107, releases from such carrier foil strip at the edge 113 and, on the other hand, the next successive label at the carrier foil strip 107 then just assumes the prescribed position between the electrode arrangement 1 and the counterelectrode 9 as previously considered.

The label provided with the latent electrostatic charge image and which has been released from the carrier foil strip 107, has been conveniently designated by reference character 107C. A movable element or member 114, for instance or intermittently or periodically rotating arm, a roller or equivalent device, and which receives at its end face of surface 114A the released label 107C, is located in the neighborhood of the sharp deflecting edge 113, ie at the location where the label 107C is released from the carrier foil strip 107. In order to insure for proper transfer of the label it is possible to provide. for instance, a roller formed of insulating material and which presses with a slight pressure against the aforementioned end surface 114A. This end surface 114A or the entire movable element 114 is preferably fabricated from a material, for instance TEFLON or the like to which the self-adhering labels 107C do not adhere too strongly.

The latent electrostatic change image applied to the labels 107C by means of the electrostatic printer or printing mechanism 112, are later developed in a suitable developer or developing device 130. The developer includes a so-called magnetic brush 131. The magnetic brush 131 contains numerous static electrically charged tones particles, the polarity of which is chosen to be opposite to the polarity of the latent electrostatic charge image. During the advancing movement of the labels 107C during the rotation of the movable element 114, toner particles from the magnetic brush 131 are attracted by the charged locations of the electrostatic charge image 05 that there appears a visible image. The developer may be for example of the type disclosed in the commonly assigned, copending United States application, Ser. No. 268,783, filed July 3, I972, now US. Pat. No. 3,783,828, granted Jan. 8, 1974, and entitled Apparatus For Developing Latent Electrostatic Charge Images" and to which reference may be readily had.

Preferably the side of face of the label 107C impinged with the latent electrostatic charge image as it moves from the electrostatic printer 112 to the developer 130 is temporarily subjected to the action of a corona discharge from a corona discharge device having an electrode 151, this corona discharge having a polarity opposite to the polarity of the electrode arrangement 1. As a result, the parts of the label which should remain white are charged opposite to the polarity of the electrostatic charge image. Although this charge is weaker than the charge at the latent electrostatic image this still insures that there will occur a repulsion of the charge toner particles from the locations of the label which should remain white. Owing to these measures the contrast of the electrostatically produced printing image is considerably improved. Techniques and equipment for improving the contrast of the electrostatically produced printing image forms subject matter of the commonly assigned, copending United States application, Ser. No. 272,064, filed July 14, 1972, now abandoned, and entitled Method And Apparatus For lmproving The Contrast During Electrostatic Printing".

lt is advantageous to deliver the developed image to a suitable fixing mechanism or fixer 132 in order that the image composed or relatively weakly adhering toner particles becomes wear or abrasion resistant. Such fixer 132 can be realized, for instance, by means of an infrared radiation device.

During further movement of the movable element 114 the label 107C adhering thereto, the electrostatic charge image of which has now been fixed, is delivered to an opening 125 of the electrostatic printing apparatus 100. The finished labels 107C can be removed at that location from such electrostatic printing apparatus 100. It is also advantageous at this location to allow a suitable stripper or gripper mechanism, for instance in the form of a fork-like stripper 125a or the like, to act beneath the finished label 107C in order to facilitate removal of such label.

The carrier foil strip 107 which has been freed from the labels leaves the feed mechanism 122 through a channel or groove arrangement 123. This carrier foil strip 107 can be collected for instance at a receptacle or container 124 mounted at the outer wall of the housing of the electrostatic printing apparatus 100. It is however also possible to deliver the carrier foil strip 107 via the channel arrangement 123 to a wind-up mechanism so that such carrier foil strip can be again re-used. This can be advantageous if there is employed as the material for the carrier foil strip, for instance, a metallic foil or a metallized paper strip, the costs of which are significant, so that reuse is warranted.

The motor M arranged at the base plate 101 drives through the agency of chains or belt means and the like the strip feeder or feed mechanism 122 and the movable element 114. This drive motor M can be also used for driving the developer 130. The temporary connection of such system components with the drive motor M can occur in conventional manner by means of suitable electromagnetic coupling means, the excitation of which, for instance. can be controlled in any suitable way, as for instance through the use of a cam disk in a well known manner.

While there is shown and described present preferred embodiments of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims. ACCORD- lNGLY.

What is claimed is:

I. An apparatus for producing printed images on a carrier by electrostatic printing techniques. comprising:

an electrode arrangement including a plurality of electrode elements each having a predetermined size for forming a latent electrostatic charge image on a carrier;

a counterelectrode arranged in confronting relation and spaced from said electrode arrangement for receiving, between said counterelectrode and said electrode arrangement, a carrier adapted to receive a latent electrostatic charge image;

means for applying a constant voltage between selective ones of said plurality ofclectrode elements and said counterelectrode to form a latent electrostatic charge image on a carrier positioned therebetween; and

means for producing on the carrier a latent electrostatic charge image of a size larger than the predetermined size of said electrode elements, said image-producing means including means for moving said carrier and said electrode arrangement relatively of each other in alternate directions during the application of said constant voltage between the selected electrode elements and the counterelectrode.

2. The apparatus as defined in claim 1, wherein said moving means incorporates a guide member for the electrode arrangement and means mounting said guide member to be displaceable in a plane substantially parallel to the carrier.

3. The apparatus as defined in claim 1, wherein said moving means includes a guide piece for supporting the electrode arrangement, and an eccentric plate having an eccentric pin engaging with said guide piece.

4. The apparatus as defined in claim 3, further including a shaft for said electrode arrangement. at least one guide belt and at least one bifurcated guide element for hindering rotational movement of the guide piece about said shaft.

5. The apparatus as defined in claim 1, further including a shaft, a drive motor and a pulley belt system including a pulley belt and belt pulley means for driving said shaft.

6. The apparatus as defined in claim 5, wherein said moving means includes a counterpiece secured to said shaft, an eccentric plate having an eccentric pin displaceably secured to said counterpiece.

7. The apparatus as defined in claim 6, wherein said moving means further includes a guide piece with which engages said eccentric pin, said electrode arrangement being connected with said guide piece.

8. The apparatus as defined in claim 5, further including axially displaceable mounting means for said shaft.

9. The apparatus as defined in claim 8, further including a flange secured to said shaft, a support, an electromagnetic system secured to said support, a pivotal frame having a connection piece, said electromagnetic system having a traction rod engaging by means ofa coupling element said connection piece of said pivotal frame in such a manner that upon excitation of the electromagnetic system said shaft is axially displaced via said pivotal frame and said flange.

10. The apparatus as defined in claim 9, further including spring means for returning the shaft into its original position after deenergization of the electromagnetic system.

ll. The apparatus as defined in claim I, wherein said counterelectrode is provided with bore means, a vacuum device and conduit means for connecting said bore means with said vacuum device.

12. The apparatus as defined in claim 1, further including an electromagnetically actuated clamping mechanism for the carrier for the latent electrostatic charge image.

13. The apparatus as defined in claim 1, further including a developer for the electrostatic charge image at the carrier, said developer having magnetic brush means.

14. The apparatus as defined in claim I, further including a feed mechanism for controlling passage of a carrier foil strip with carriers adhering thereto through an electrostatic printer containing said electrode arrangement and counterelectrode.

15. The apparatus as defined in claim 1, further including means for moving the carrier along a predetermined path of travel, a corona discharge device effective along said path of travel of the carrier.

16. The apparatus as defined in claim 15, wherein the polarity of the latent electrostatic charge image and the corona discharge device differ from one another.

17. The apparatus as defined in claim 1, further including a developer for developing the latent electrostatic charge image formed at a carrier, and a movable element for moving such carrier with the latent electrostatic charge image into and out of the operable region of the developer.

18. The apparatus as defined in claim 1, further in cluding a corona discharge device, and a movable element by means of which the carrier can be brought into and out of the operable region of said corona discharge device.

19. The apparatus as defined in claim 1, further including a fixer for fixing a developed electrostatic charge image at the carrier, and a movable element for bringing the carrier with the developed electrostatic charge image into and out of the operable zone of the fixer.

20. The apparatus as defined in claim 1, wherein the apparatus possesses an opening for the removal of the carriers, and a movable element for delivering a carrier to the region of said opening.

21. The apparatus as defined in claim 20, further including mechanism for lifting the carrier with the electrostatically produced printed image off the movable element.

22. The apparatus as defined in claim 1, further including means defining a station for receiving a carrier foil strip for transporting the carrier after such carrier foil strip has been freed of the carriers previously adhering thereto.

23. The apparatus as defined in claim 1, further in cluding means defining a sharp edge over which moves a carrier foil strip for the support of the carriers adhering thereto, said sharp edge serving for the detachment of a carrier provided with a latent electrostatic charge image from such carrier foil strip.

Claims

1. An apparatus for producing printed images on a carrier by electrostatic printing techniques, comprising: an electrode arrangement including a plurality of electrode elements each having a predetermined size for forming a latent electrostatic charge image on a carrier; a counterelectrode arranged in confronting relation and spaced from said electrode arrangement for receiving, between said counterelectrode and said electrode arrangement, a carrier adapted to receive a latent electrostatic charge image; means for applying a constant voltage between selective ones of said plurality of electrode elements and said counterelectrode to form a latent electrostatic charge image on a carrier positioned therebetween; and means for producing on the carrier a latent electrostatic charge image of a size larger than the predetermined size of said electrode elements, said image-producing means including means for moving said carrier and said electrode arrangement relatively of each other in alternate directions during the application of said constant voltage between the selected electrode elements and the counterelectrode.

4. The apparatus as defined in claim 3, further including a shaft for said electrode arrangement, at least one guide belt and at least one bifurcated guide element for hindering rotational movement of the guide piece about said shaft.

9. The apparatus as defined in claim 8, further including a flange secured to said shaft, a support, an electromagnetic system secured to said support, a pivotal frame having a connection piece, said electromagnetic system having a traction rod engaging by means of a coupling element said connection piece of said pivotal frame in such a manner that upon excitation of the electromagnetic system said shaft is axially displaced via said pivotal frame and said flange.

11. The apparatus as defined in claim 1, wherein said counterelectrode is provided with bore means, a vacuum device, and conduit means for connecting said bore means with said vacuum device.

14. The apparatus as defined in claim 1, further including a feed mechanism for controlling passage of a carrier foil strip with carriers adhering thereto through an electrostatic printer containing said electrode arrangement and counterelectrode.

18. The apparatus as defined in claim 1, further including a corona discharge device, and a movable element by means of which the carrier can be brought into and out of the operable region of said corona discharge device.

23. The apparatus as defined in claim 1, further including means defining a sharp edge over which moves a carrier foil strip for the support of the carriers adhering thereto, said sharp edge serving for the detachment of a carrier provided with a latent electrostatic charge image from such carrier foil strip.