Enveloped stylus recorder
United States Patent [191 Silverberg [54] ENVELOPED STYLUS RECORDER [75] Inventor: Morton Silverberg, Rochester, NY. [73] Assignee: Xerox Corporation, Rochester, NY.  
 [22] Filed: Mar. 10, 1969 [21] Appl. No.: 805,768  
 [52] U.S. Cl. 346/74 ES, l0l/D1G. 13 [51] Int. Cl. G0ld 15/06 [58] Field of Search 346/74 ES, 74 MP; 197/1 [56] References Cited UNITED STATES PATENTS 3,308,473 3/l967 Sawazaki 346/74 Primary E.\&#39;aminerTerrell W. Fears Assistant Examiner-Jay P. Lucas Apr. 1, 1975 [57 ABSTRACT Electrographic recording apparatus utilizing a linear array of conductive styli which is moved in contact with an insulating recording medium along a path through a recording zone and to which are applied signals representative of information to be recorded in the form of latent electrostatic charge patterns. These latent patterns are rendered visible by the application thereto of electroscopic marking particles carried by a fibrous developer which is positioned parallel to and coextensive with the recording zone for rotation about an axis and into contact with the recording medium in the recording zone while the linear array is in motion during its recording cycle.  
 2 Claims, 4 Drawing Figures PATENIEDA 1 1975 3, 875.578  
 SHEEI 1 or 2 FIG.  
 &#39; INVENTOR. MORTON SILVERBERG ATTORNEY v Y owsm PATENTEDAPR 1 1975 3.87 5.578  
 SHEET 2 (IF 2 3 Q as 70 64 ea f 60 62 f g6 r ---DEcoDr-:R CHAR. GEN START STOP PRINTER FIG. 4  
 ENVELOPED STYLUS RECORDER This invention. relates generally to recording apparatus, and, specifically, to electrographic recorders or printers.  
  Electrography or electrographic recording involves placing an electrostatic charge pattern on an insulating recording medium using conductive electrically biased electrodes or styli and rendering these charges visible. In order to make the recording charge pattern discernible to a human agent electroscopic marking particles are caused to adhere to the pattern by electrostatic attraction. This process is conveniently referred to as developing the latent charge pattern. The marking particles, commonly referred to as toner, bear an electrostatic charge opposite in polarity to that of the charge pattern to be developed and hence the attractive force between the two.  
  One major problem area in utilizing electrography in a practical printer is the technique and apparatus for conveying toner to the recorded charge patterns in the development step. The problem is not just one of mechanical hardware that will perform this task satisfactorily but also one of being able to incorporate a developer assembly in an electrographic printer having a commercially acceptable design. This latter problem can be defined in one respect as maintaining the minimum possible distance between the recording zone and the station at which the recorded charge patterns are developed. The solution to this problem results in two significant advantages.  
  The first advantage would be the saving of recording medium which lies between the developing station and the recording zone. While in each recording period the savings may be small, a frequently used communications terminal would magnify the premium placed on such savings. In certain mobile printer applications, the monetary economics may not be as important as the space savings both from the aspect of storing received messages and the supply of recording medium.  
  A second advantage would be in the time elapsing between recording and development. The closer the recording zone is to the developer, the quicker the recorded information may be discerned and used.  
  Concomitant with substantially instantaneous development is the contamination of the recording styli with toner. However, the present invention minimizes this while achieving the aforementioned advantages.  
  Therefore, it is an object of the present invention to improve electrographic recording.  
  Another object of the present invention is to improve developing of electrographically recorded information.  
  A still further object of the present invention is to provide an improved electrographic recording apparatus which minimizes the recording medium consumption, the recording to developing delay, and styli contamination.  
 These and other objects which may become more apparent are accomplished in accordance with the principles of the present invention wherein moving recording styli are enveloped by a toner applicator during the recording process to instantaneously develop the information as it is recorded.  
  Other objects and features of the present invention as well as those specified above will be better appreciated when the following detailed description is read in connection with the appended drawings wherein FIG. 1 is a perspective view of an electrographic recorder in accordance with the principles of the present invention.  
  FIG. 2 is a cross-section view of the developing and recording zone of the present invention;  
  FIG. 3 is a top view of the stylus during simultaneous recording and developing with portions broken away; and,  
  FIG. 4 is a block diagram of a character generating circuit which may be employed with the recorder illustrated in FIG. 1.  
  Electrographymay be defined as the deposition of electrostatic charge on an insulating medium in a configuration corresponding to an electrode suitably biased. The electrode may be in contact with the medium which may be constituted by a plastic-coated, or predried paper, or any other dielectric sheet having a sufficiently high resistance to hold an electrostatic image.  
  This type of recording medium designed by reference numeral 2 is shown in FIGS. 1 and 2 as supported in a recording zone generally by a backing electrode or support member 4 which holds the recording medium against contact by an electrographic stylus array 6 as it traverses the recording zone.  
  The electrographic stylus array 6 is not shown in detail and may consist of a flat, resilient body of insulative material such as Mylar with a plurality of etched electrically conductive electrodes on one side thereof insulated from one another. This array may be mounted in or on insulative support 8 through which electrical conductors may be provided to supply electrical recording signals individually to each stylus. These electrical conductors may terminate at any suitable place on the carriage assembly in the form of a socket or other type of electrical connection to facilitate connection to a source of recording signals such as a character generator. FIG. 2 illustrates such a place indicated by reference numeral 9.  
  The approach described is well known in producing alphanumeric recordings where each symbol or character is composed of selected areas from a matrix of areas. For example, a five by seven matrix may be employed while a larger matrix may also be useful depend- I ing upon the quality of recorded symbols desired.  
  Movement of the stylus array is provided by a suitable motor 10 which may be a constant drive motor. The motor has its force selectively coupled to shaft 12 and to drive pulley l4 affixed thereto by suitable clutch means not shown in detail which is selectively engaged or disengaged by appropriate signals. The origin of these signals will be described in more detail hereinafter.  
  A clock spring motor may be associated with shaft 12 which is wound during the motion of this shaft 12 in a direction such as to move the stylus array from left to right as FIG. 1 is viewed. The purpose of this clock motor is to return the stylus from the right side of the recording medium 2 to the left side thereof after a leftto-right or recording traversal has been completed. As will be described in more detail hereinafter, this is a conventional technique for performing the carriage return function in the recorder. The drive pulley l4 frictionally engages a cable 16 which is supported by idler pulleysl8 and 20 to translate the driving force of the motor 10 to the stylus support 8. To further stabilize the stylus support during its traversal of the recording medium 2, there may be provided appropriate guide shafts 22 and 24 which pass through the carrige assembly 26 to which is secured the stylus support 8. As shown through the broken away portions of FIG. 1, the carriage assembly 26 is attached to opposite ends of the cable 16 and is slidably mounted on guide shafts 22 and 24 so as to maintain the relative position of the stylus array 6 relative to the recording medium 2 during recording.  
  During operation the stylus array is driven from left to right across the recording medium 2 during the application of suitable recording signals to the styli themselves. During the movement of the stylus array a predetermined amount referred to as a character space, a character is recorded on the electrographic recording medium 2 in the form of a latent electrostatic charge pattern. The recording medium 2 may be stationary in the recording zone during the left-to-right traversal of the stylus array, during which an entire line of characters may be recorded. At the terminal point of this stylus movement, a suitable microswitch or other means may be actuated by the presence of the carriage assembly 26 to actuate the aforementioned clutch associated with motor to disengage shaft 12 from this motor. The clock motor previously referred to may then unwind expending its stored energy to the carriage assembly 26 to return to its initial left margin position. The actuation of the switch which effects the carriage return may also be utilized appropriately for advancing the recording medium 2 by means of a drive roller 28.  
  The alphanumeric shaped electrostatic charge patterns recorded by the traversing stylus are rendered visible by depositing electroscopic marking particles or toner on these patterns. This is accomplished substantially at the time of recording in accordance with the principles of the present invention by the rotation of a developing applicator generally referred to by reference numeral 30 so as to envelop the stylus array as it is recording.  
  As shown in FIGS. 1 and 2, applicator 30 includes an applying member 32 mounted on a support 34 which in turn is affixed to a shaft 36. The applying member 32 is shown to have a cylindrical developing surface 37 which extends between the left and right portions of the recording zone.  
  Surface 37 may be loaded with conventional electroscopic marking particles, commonly referred to as toner, through the use of a donor roller 38. It is shown only schematically in the drawings since it per se forms no part of the present invention which is compatible with many donor systems.  
  The developing surface 37 has as its center of radius the shaft 36 which supports the applicator 30 for rotation during the development cycle. The necessary rotative force applied to shaft 36 is provided ultimately from a suitable motor 40 having a drive .shaft 42 coupled via a conventional clutch 44 to a drive pulley 46 affixed to a shaft 48. A timing belt 50 is entrained on the drive pulley 46 and pulley 52 to which is affixed the drive shaft 36 of the applicator 30. By properly engaging the clutch 44, the applicator may be rotated in the direction of the arrows so as to move the developing surface 37 around the stylus array 6 and into contact with the recording medium 2 at the recording zone. This is shown with reference to the broken line 54 which illustrates the volume developed or swept out by the applicators rotation.  
  Applying member 32 may be made comprised of a great number of materials, some fibrous ones of which for illustrative purposes are specified in U.S. Pat. No. 3,251,706 which issued to L. E. Walkup, May 17, 1966, which is assigned to the same assignee as the instant application. One example which works well is natural rabbit fur. Of course, the developing portion 32 of the applicator 30 should preferrably be of a material resilient enough to permit movement of the stylus support 8 through it as the applicator rotates without excessive drag.  
  Toner is loaded onto the applying surface of applicator 30 via donor roller 38 and clings thereto by triboelectric attraction to be conveyed during the rotation of the applicator to the recording zone. At the recording zone the toner is attracted by and deposited on the latent electrostatic charge patterns placed on the recording medium 2 by the action of the stylus array in cooperation with the recording signals.  
  As the applicator 30 moves toward its developing position, which can be considered as that position when its applying surface 37 is in contact with the recording medium in the recording zone, it is continually loaded by the donor roller 38. The phenomenon of loading is such that unless the applicator is deficient in electroscopic marking particles no particles will be loaded onto it by the donor roller 38. Therefore, the problem of excess toner on the applicator 30 is eliminated.  
  FIGS. 1 and 2 show the position of applicator 30 in a non-developing position, or what may be referred to as a viewing position. Since the non-developing surface of the applicator 30 is substantially planar and passes through the axis of the shaft 36, a viewer may directly&#39; see the recording zone without any portion of the applying member 32 obstructing his line of vision.  
  To insure uniform quality in the recorded characters, it is preferable that the backing support 4 be such as to provide a substantially flat surface at the recording zone upon which the recording medium may rest. Therefore, the latent electrostatic charge patterns recorded on the medium 2 by the moving styli can be considered to lie in a predetermined plane which is, in effect, a function of the position and configuration of the backing support 4. Hence, if this support 4 is substantially flat, all the electrostatic charge patterns recorded during one traversal of the carriage assembly 26 will lie in the same plane. Consequently, the viewing angle may be defined by an imaginary line (broken line 56in FIG. 2) passing through the plane of the recording zone which is, in effect, the plane occupied by the last recorded symbols on the medium 2 and which is substantially perpendicular to the direction of traversal of the stylus array 6 and a line (broken line 58 in FIG. 2) extending from the lower extremity of a recorded character in the recording zone and passes in close proximity to the upper most portion of applicator 30 in its viewing position. Stated another way, this second line 58 starts at the lower edge of the recording zone and extends over the top of the applicator 30 and as close to it as it can be and still remain straight.  
  Subsequent to development, the toner may be fixed to the recording medium in any of several conventional manners. For example, recording medium support and guide member 39 may house a platen fuser employing a resistance heating coil over which the medium is moved. Flash fusing or fixing may also be used to render the development images permanent.  
  With the mechanical structure of the recorder and the developing system described, one possible way of controlling this recorder and developing system will be explained with reference to the block schematic of FIG. 4. What has been described as the recorder or printer is represented basically by the suitably labelled block 60. The input to the printer. 60 originates, for example, from any source of binary code representative of alpha-numeric information to be recorded which is supplied to the circuit of FIG. 4 at input terminal 62.  
  Such a code, such as used in the American Standard Code for Information Interchange, is provided to the input of a conventional decoder circuit 64 which decodes the binary code to generate a character pulse on one of a series of parallel outputs indicative of the alphanumeric symbol to be recorded. Output conductor 66 is intended to represent a number of outputs each of which would correspond to a separate alphanumeric character. These outputs collectively provide one input to a character generator 68 which may take various conventional forms.  
  As an example only, generator 68 may consist of a diode matrix having a number of character select input wires which corresponds to the outputs of the decoder circuit 64. These wires are selectively coupled to readout wires via diodes which are forward biased when their respective character select wire is energized. Another form which the character generator may take is a magnetic core matrix, having five columns and seven rows, wherein a particular character select wire associated with one of the outputs 66 intertwines an appropriate pattern of magnetic cores corresponding to the alphanumeric symbol to be recorded. The character generator as well as the other parts of the block diagram of FIG. 4 are not intended to form a particular part of the present invention per se and therefore are shown schematically only since other well known conventional circuits may be used to provide their functions.  
  Output 74 from the decoder 64 may represent a start command which is decoded by the decoder from the input codes received at terminal 62. This start indication may be used to operate a start-stop circuit 76 which may include a flip-flop to provide a start signal via output 78 to the printer 60. As an example, this start signal may be applied to the clutch associated with motor in FIG. I thereby coupling shaft 12 to the motor to commence the traversal of the recording stylus. Similarly, this same signal may be applied also to clutch 44 to initiate the constant rotation of applicator 30. Output 72 from the decoder may couple an appropriate decoded stop command to the start-stop circuit 76 which in effect would reset the flip-flop therein deenergizing the clutches formerly energized in the printer 60.  
  Output 71 from the decoder 64 simply provides a signal indicative of the fact that a binary code has been decoded in the decoder 64. In this manner, for each character entered at the terminal 62 which effects a decoding process in the decoder 64, an output signal will be generated on conductor 71. This effectively provides a control pulse to the character generator which may initiate, for example, in the case of a magnetic core matrix, a distributor circuit which would sequentially readout each column of the core matrix ata rate correlated to the speed of the styli movement. As each column is sampled by the distributor circuit, a group of parallel outputs would be energized depending on the cores set by the character select wire. The signals on these parallel outputs would be supplied to a suitably driver stage which would provide parallel recording signals to the styli in array 6 via output 70.  
  Conventional techniques may be used to conserve the developed information during the return of the stylus array to the left margin. Generally, this can be accomplished by slightly rotating shaft 22 and carriage assembly 26 about shaft 24 and away from the recording zone.  
  Referring now to FIG. 3 the recording zone is depicted at an instant during the recording and development cycle wherein the stylus array is totally enveloped by the developing portion 32 of applicator 30. The stylus support 8 and the stylus array are moving toward the top of the figure. As charge patterns are recorded on the recording medium 2 the applicator 30 substantially instantaneously develops these patterns by the deposition thereon of toner.  
  In addition, the applicator also serves to scavenge excessive toner which may have been deposited in the background areas where no electrostatic charges were placed.  
  As the applicator 30 rotates and envelops the record ing stylus, toner may be deposited on one of the styli if it is at that time carrying a recording potential. However, when that particular stylus is at a non-recording potential, this toner which is not then tightly adhering to the stylus is removed as the applicator envelops it. In this way, over a period of time the toner does not build up on the stylus array and decrease its efficiency. Utilization of an applicator such as illustrated in FIGS. 1 and 2 insures a certain degree of control over the toner to insure that stray toner which would contaminate other moving mechanisms in the general area of the developer is kept to a minimum.  
  A specific applicator configuration has been described in the embodiment of FIGS. 1 and 2. However, it can be appreciated that other configurations are possible within the inventive concept described herein. For example, the applicator may have a circular crosssection in addition to the alternative of a semi-circular or other type of partial circular cross-section.  
  In addition, while the present invention has been described in terms of a multi-stylus electrographic recorder, the concept of the present invention are equally applicable to a single recording electrode without departing from the true spirit of the invention.  
  Further, while FIG. 4 illustrates a system in which the applicator 30 continuously rotates at a constant rate, it should be realized that the applicator 30 may be selectively rotated in accordance with any desirable pattern or rate and still be compatible with the inventive concept described hereinabove.  
  Similarly, a reciprocating recording stylus assembly has been described for illustrative purposes only, and the present invention is not limited to this type of driving technique and is equally applicable to a cyclically driven recording element.  
  While the preferred embodiment has been described with a stylus array moving across a recording medium, the present inventive concept is also compatible with a fixed linear array of styli where the recording medium moves across and in contact therewith. In such a situation, the axis of the toner applicator may be substantially parallel with the array.  
  Furthermore, while a fibrous applicator has been alluded to in a conventional manner, a magnetic brush applicator is also considered fibrous and its utilization is possible in accordance with the principles of the present invention. lnsulative coated magnetic attractable marking particles could be used to avoid any electrical short circuits.  
  While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the true spirit and scope of the invention.  
 What is claimed is:  
 1. An electrographic recording apparatus comprising:  
 a. a recording head including a stylus electrode adapted to deposit electrostatic charges on a recording medium;  
 b. motive means for moving said recording head during a recording cycle;  
 0. signal means for applying recording signals to said recording head during said cycle;  
 (1. a fibrous applicator bearing electroscopic marking particles; and;  
 e. means for moving said fibrous applicator during said cycle into contact withsaid recording head and past two sides thereof. 7  
 2. Apparatus as defined in claim 1 wherein said means for moving said fibrous applicator acts repetitively during said cycle.