Abstract:
A recording medium drive roller and a wrap roller are mounted to a cover for an electrographic printer and cooperate to enable the recording medium to be easily loaded into the printer when the cover is open, and to provide proper tension to the paper when the cover is closed to permit uniform and aligned feeding of the recording medium from the source during operation of the printer.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to an electrographic recorder cover assembly which includes a recording medium loading device, and particularly to a recording medium drive roller and wrap roller which cooperate to facilitate loading the recording medium into the electrographic printer. 
     2. Description of the Prior Art 
     In the past, loading of recording medium into an electrographic printer has generally been an awkward and cumbersome job which necessitated that the operator work and manipulate the recording medium in a blind area of the machine. Generally, the operator had to feed the recording medium between a number of rollers which he was required to manually hold out of the way of the recording medium. Frequently, the operator could never be sure that the recording medium was being fed between the rollers in a proper manner until he had completed the entire operation. Many times the loading operation was not successful and had to be repeated one or more times. Also, many of the recording medium loading devices known and used in the past did not provide that an even and constant force be exerted against the recording medium to insure that proper printing takes place thereon. The present invention is directed toward improving these operations. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a partial perspective view of an electrographic printer with the cover in the open position showing the printing station and the paper loading surface according to the principles of this invention; 
     FIG. 2 is a sectional view taken along line 2--2 of FIG. 1; and 
     FIG. 3 is a sectional view similar to FIG. 2 showing the cover of the electrographic printer in a closed and operative position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An electrographic printer 10 is shown in FIG. 1 which consists, essentially, of a main body or base portion 12 and a cover assembly 14. The cover assembly 14 is pivotally engaged to the main body portion 12 about an axis 16 and is pivotable thereabout from a first, or open, position to a second, or closed, position in readiness for printer operation. 
     A segment electrode assembly 18 is pivotally mounted in the cover member 14 about axis pin 20, as best seen in FIGS. 2 and 3, and is essentially comprised of a rigid mounting board 22, a printed circuit driver board 24 mounted thereto and a plurality of segment electrode units 26 which are engaged to the driver board 24 and extend outwardly thereform. The illustrated and disclosed segment electrode assembly of concurrently filed and copending patent application Ser. No. 673,029 entitled &#34;Electrographic Segment Electrode Clamping Assembly&#34; is satisfactory for application to the present embodiment. The segment electrode units each comprise a plurality of fingers which are thin and quite flexible. 
     When the cover 14 of the electrographic printer 10 is in an open position, as best seen in FIGS. 1 and 2, the segment electrode assembly 18, and specifically the driver board 24 of the segment electrode assembly 18, is held inward and, for example, against a stop surface 27 of a recessed plate 28 which is dictated by the force from a spring 30 extending from a mount 31 on the board 22 to a complementing mount 32 on the inside surface 33 of the cover 14. The plurality of segment electrode fingers 26 are, thus, disposed in a protective recessed area 34. 
     A pair of cover latch members 36 protrude upwardly from surface 38 of the main body portion 12 of the printer 10 and, as the cover member 14 is pivoted toward its closed position in the direction of curved arrows 35, each protruding latch member 36 passes through an accommodating slot-shaped aperture 40 formed in a face plate 41 at the underside of the cover member 14. Once each latch member 36 is through its respective slot the cover assembly 14 is locked and the segment electrode assembly 18 is set in place so that the printing operation may take place. 
     Mounted behind the cover plate 41 and within the cover member 14, is the rigid mounting board 22 which has at least one threaded adjusting screw affixed thereto in such a manner that the head 44 of the screw 42 engages the latch member 36 when the cover 14 is in the closed position. A lock nut 46 is affixed to the screw 42 so that once the segment electrode assembly 18 is disposed before a stylus board 48 the distance between the screw head 44 and the latch member 36 can be set by locking the nut 46. With the adjustment set, the rounded top portion 39 of latch member 36 engages the mounting board 22 before the cover member 14 is fully closed. The force of the latch member 36 against the screw head 44 overcomes the tension exerted by spring 30 and causes the entire segment electrode assembly 18 to pivot about axis pin 20 toward the facing surface 38 of the main body portion 12. 
     It is obvious that the segment electrode fingers 26 do not make direct contact with the stylus board 48 when the printing process is taking place. A length of recording paper 50 is distributed from a paper storage bin over the selectively energized stylus at the surface 49 of the stylus board 48. When the cover 14 is closed, the paper 50 is engaged between the segment fingers 26 and the stylus board 48. 
     In loading paper 50, as in the embodiment illustrated, the cover 14 is opened and a sufficient supply of paper is placed in the storage bin. The paper supply may be either in roll form or in Z-fold form. When the paper supply is depleted, new paper is inserted and a length of the recording paper 50 is drawn up out of the storage bin, while the cover is open, between the cover latch members 36 across the conductive styli surface 49 of stylus board 48 and up to the area where a paper drive roller 52 and a wrap roller 54 contact each other, as best seen in FIGS. 2 and 3. The paper 50 is substantially aligned by positioning the paper at the line of contact between the drive roller 52 and the wrap roller 54. When the paper 50 has been aligned, the drive roller 52 is energized momentarily by the operator through a switch and electrical stepper motor until such a time that the paper 50 is caused to pass between the two rollers. When the paper 50 is fully disposed between the drive roller 52 and the wrap roller 54, the cover 14 can then be closed. 
     It will be noted that when the cover 14 is in the up position, as best seen in FIG. 2, and the paper 50 is initially mildly urged between the drive roller 52 and the wrap roller 54 to touch both of the rollers just at their point of contact. Afterwards, but during the loading process, it is driven farther between the rollers. The paper is thereafter exited from slot 55 of cover 14. The paper 50 is initially engaged about the drive roller 52 for a surface angle of approximately 30° . Thereafter, when the cover 14 is rotated to its closed position, as best seen in FIG. 3, the paper 50 is caused to wrap around the drive roller 52, because of the action of the wrap roller 54, to engage a surface angle of approximately 120 degrees. By having the paper 50 in contact with the drive roller 52 for an arc of approximately 120 degrees, the drive roller 52 is able to exert an even force on the paper 50 while not overriding any other recording medium alignment device, such as the one illustrated in U.S. patent application Ser. No.  625,995 
     The wrap roller 54 is supported by the cover 14 in such a way that it is free to move and stay in contact with the drive roller, or the paper therebetween, and find its own centering point while cooperatively operating with the drive roller 52. The wrap roller 54, for instance, may be mounted to a pair of bearing assemblies 56 which in turn would mount at each end to a typical ramp structure 58, formed as part of the cover 14 and which act as bearing surfaces. A pair of springs 60, one of which is shown, extend between a mount 62 on the cover and a stub shaft 64 of the bearing assembly 56 concentric with the wrap roller 54. The wrap roller 54, in this configuration rotates very little on the ramp, or bearing, surface 58 for rotation is designed to occur about the bearings 56. The ramp surface 58 allows the wrap roller 54 to move toward or away from the drive roller 52 and, therefore variations between the concentricity of rollers, 52 and 54 and paper thickness is compensated for automatically. The spring 60, in cooperation with the wrap roller 54, exerts tension on the paper 50 which cooperatively operates to tension and aid in aligning the recording paper with a recording medium system such as is described in U.S. patent application Ser. No. 625,995. Also, the spring tensioned wrap roller 54 contributes greatly toward making the system extremely easy to operate. The operator, as explained earlier, merely inserts the paper 50 between the rollers 52 and 54 and then energizes the drive roller 52 until the paper 50 is drawn between them. The cover 14 is then closed and the process of electrographic printing can take place. 
     For safety of operation as well as for other obvious reasons, the cover 14 should not be opened while the printing process is taking place. A suitable electrical interlock and a latching means, as disclosed herein, for instance, can readily be provided. For example, each of the protruding latch members 36 may have a hooked portion 37 formed thereon which are received in complementing openings 66 of catch member 68 of the cover 14. The catch members 68, for example, may be affixed to the cover member 14 at a pivotable connection 70. Suitable apparatus, such as a typical spring 72, may be used to bias the catch member 68 so that it remains engaged to the hooked portion 37 of the protruding member 36 when the cover 14 is closed. Buttons 74, only one of which is typically illustrated, are arranged to cooperate between the exterior surface 15 of the cover member 14 and the catch member 68. By pushing the buttons 74, the force of each spring 72 is overcome and the catch member 68 is caused to pivot at the pivotable connection 70, thereby releasing it from the hooked portion 37 of the protruding member 36. The cover 14 can then be opened. In the disclosed configuration the cover 14 can only be opened by design and not by accident. A spring such as spring 30, or other suitable means, can be mounted to the electrographic printer base 12, or to the cover 14 thereof so that when the buttons 74 are pressed to release latch 68, the cover is forced upwardly a small amount. This aids the operator in opening the cover to load or inspect the printer. 
     An electrical switch, not shown, could, for instance, be incorporated into the cover 14 to cooperate with the catch member 68 so that when the catch member is released from the hooked portion 37 of the protruding member 36, all high voltage electrical energy is shut off to operational apparatus inside the cover. Any potential for injury, which could be caused to a person who accidentally contacts some electrical area, is thereby eliminated. Such an interlock prevents electrical energy from being supplied to the assembly within the cover 14 unless the cover is closed. consequently, the possibility of a person receiving an electrical shock is greatly reduced. 
     A preferred embodiment of the invention, has been shown and described, but it should be obvious to any skilled in the art that various modifications and/or changes can be made thereto without departing from the spirit or scope of the invention as claimed therein.