GB2162795A - Printer paper handling system - Google Patents

Abstract

A paper and forms handling system operates in conjunction with a printer of the type which employs a horizontal roller platen (11) and a transversable printhead means for printing on paper overlying the platen. Guide means are provided for guiding a cut sheet from above tangentially into contact with the rear of the platen while a pair of tractor assemblies (61 and 63) are provided to feed continuous edge-perforated paper tangentially into contact with the bottom of the platen. A motor is provided for driving the platen in rotation to drive paper past the printhead. A lever operated clutch means (67, 73) operates, in a first position, for driving the tractor assemblies from the motor means synchronously with the platen and, in a second position, releases the tractor assemblies from the platen drive means. Accordingly, continuous forms can be held ready in the tractors while printing takes place on cut sheet paper. A bail assembly Figures 4 and 5, holding paper onto the platen near the print line is biased stably in either operative or retracted position by an over-center spring. <IMAGE>

Description

SPECIFICATION Printer paper handling system The present invention relates to a paper and forms handling system for a printer and more particularly to such a system which permits continuous forms to be held ready in the printer even while printing takes place on cut sheet paper.

While it has previously been proposed to implement the paper handling mechanism of a printer so that both cut sheet and continuous forms can be handled, it was necessary to completely remove the continuous forms paper from the tractors typically utilized to feed such paper while printing was being accomplished on individual cut sheets. As is understood, the necessity of completely removing the continuous form paper before printing on cut sheets requires substantial operator intervention at each changeover. Such time consuming operator intervention was particularly wasteful in the context of an office environment where frequent change-overs between continuous paper and cut sheet are typical in the daily flow of work.

Among the several objects of the present invention, may be noted the provision of a forms and paper handling system for a printer which permits continuous forms to be held ready while printing takes place on cut sheet paper; the provision of such a system in which cut sheets may be simply fed to a roller platen in the manner of a conventional typewriter; the provision of such a system in which edge-perforated continuous form paper may be fed by conventional tractor assemblies which engage the edge perforations; the provision of such a system which is highly reliable; the provision of such a system which is user friendly; and the provision of such a system which is of relatively simple and inexpensive construction. Other objects and features will be in part apparent and in part pointed out hereinafter.

The present invention is a forms handling system for a printer comprising a horizontal roller platen, at the front side of said platen, traversable print head means for printing on paper overlying said platen guide, means for guiding a cut sheet from above tangentially into contact with the rear of said platen, means for feeding continuous form paper tangentially into contact with the bottom of said platen, motor means for driving said platen in rotation for feeding paper past said print head, and clutch means operative in a first state for driving said feeding means from said motor means synchronously with said platen and, in a second state, releasing said feeding means from said platen drive means, whereby continuous forms can be held ready in said tractor means while printing takes place on cut sheet paper.

An embodiment of the present invention will now be described, by way of example, with refer- -ence to the accompanying drawings, in which: Figure 1 is a perspective drawing of a printer mechanism constructed in accordance with the present invention viewed from above and from the right front corner; Figure 2 is a perspective drawing of the mechanism of Figure 1 viewed from above and from the right rear corner showing forms tractors used in the mechanism; Figure 3 is a side view from the right showing a lever-operating clutch mechanism for selectively disengaging the forms tractors; Figure 4 is an exploded view of a portion of the mechanism showing a cam which operates a paper bail; and Figure 5 is a top view of a portion of the mechanism illustrating the interaction of the cam with a fixture on the print head carriage.

Corresponding reference characters indicate corresponding parts throughout the several views of the drawings.

Referring now to Figure 1, there is indicated by reference character 11 a conventional roller platen, i.e., a platen of the type conventionally employed in typewriters. Platen 11 is driven, through a train of gears 13-15 from a pinion gear 17 mounted on the shaft of a stepper motor, the stepper motor being behind an end frame piece 19 of the overall printer assembly and thus not visible in Figure 1.

A conventional dot matrix printhead 25, e.g., of the pin or needle type, is mounted on a carriage assembly 27 riding on guides 31 so as to be traversable along the platen 11. A ribbon cartridge 33 provides an endless ribbon, a portion of which 35 extends along the platen. Thus, by appropriate energizing of the printhead 25, printed characters may be formed on a piece of paper overlying the platen 11. Preferably, the printhead carries a rotary ribbon shifter 37 for vertically positioning the ribbon, e.g., to select different coloured stripes thereon.

Traversing of the carriage 27 with the printhead 25 is performed by means of a servo motor 41 which is coupled to the carriage 27 by means of intermediate gearing 43 and an endless clogged belt 45 which passes over pulleys 47 adjacent each of the ends of the guides 31. Coordination of the operations of the several motors and the dot-matrix printhead is preferably controlled by a dedicated micrp-processor/firmwa re system as is conventional in the present state of the art.

Paper following the rotary platen 11 is held against the platen by a bail assembly 51, as well as fixed rollers beneath and behind the platen (not shown). The bail assembly 51 comprises three roller assemblies 53-55 carried on a rod 57 which is in turn mounted on a pair of pivoted arms 58 and 59. The arms 58 and 59 are each biased by an over-centre spring arrangement 61 so that the bail assembly is stably held in either of two positions, an engage position in which the rollers are pressed against the platen 11 and a disengaged position in which the rollers are swung back away from the platen, e.g., for initially inserting a new sheet of paper.

In normal printing, the printhead carriage 27 traverses most but not all of the travel distance accommodated by the guides 31. In accordance with another aspect of the invention, the carriage can be traversed, by the motor 41 under microproces sor control, to an extreme right hand position where a fixture 81 carried by the carriage can engage a C-shaped cam member 83 which is pivotally mounted on a bracket 84 supported on the printer end frame 19. The cam 83 is pivotally mounted on the bracket 84 and carries a pin 85 which extends through the end plate of the printer frame and engages a slot 87 in one of the arms 59 which hold the bail rod 51.

As may be seen from Figure 5, motion of the carriage 27 towards its extreme right hand position will cause a surface 87 on the fixture 81 to engage a mating surface 89 on the cam 83 thereby causing a counterclock-wise rotation of the cam as- seen from the top. As a result of this motion, the pin 85 will cause the bail assembly 51 to be pivoted back into a disengaged or spaced-back position from the platen 11. As indicated previously, this position is stably held due to the operation of the over centre spring 61.

On the other hand, when the carriage moves away from its right hand extreme position, a second, pin-like, contact surface 91 on the carriage fixture 81 will engage an opposing operative surface 93 on the cam 83, causing the cam to rotate clockwise as the carriage moves to the left. This clockwise motion of the cam 83 causes the pin 85 to pivot the bail arm structure 59 so that the bail is snapped back into operative position, i.e., with the rollers 53-55 biased against the rotary platen 11.

Again, this position is maintained by the over centre spring 61, even though the carriage moves further two the left, i.e., down the print line and completely out of engagement with the cam 83.

In operation, the microprocessor control system drives the carriage to the extreme right position whenever it is appropriate for the operator to insert a new piece of cut paper or to initiate feeding of the leading edge of continuous form paper-fed through the tractors 61 and 63. When the leading edge of the paper has been fed through the platen assembly and is above the level of the printhead and the bar 57, the printhead is moved to the left causing the bail to move forward in its operative position wherein the rollers 53-55 engage and hold the paper to the platen. Thus, the paper, particularly if it comprises multi-part forms, is not loose over the platen. As is understood by those skilled in the art, this clamping facilitates clear and efficient printing, particularly with a dot matrix impact printhead of the type contemplated in the printer of the type disclosed herein.

Referring now to Figure 2, which shows the back side of the printer mechanism, a pair of essentially conventional tractor assemblies 61 and 63 are slidably mounted on a pair of guide- bars 65 and 67.

The guide bar 67 is essentially a stationary guide while the bar 65 is grooved and can be selectively driven in rotation so as to couple a driving motion to the tractors in conventional fashion. For this purpose, the guide bar shaft85 carries a spur gear 67. An idler gear 69 is mounted on a carrier plate 71 which is pivoted around the axis of shaft 65, i.e., its pivot is concentric with the gear 67. Further, the gear 69 is meshed and engages with the gear 67.

A manually operated lever 73 is pivotally mounted on the end frame piece 19 and is biased towards either of two stable positions by an over centre spring 75. Lever 73 carries a lug 74 which rides in a slot 76 in plate 71 so that the plate can be moved or switched between two stable positions. In the first of these positions, the idler gear 69 is brought into engagement with the gear 14 which is part of the gear train driving the platen 11. In this position, the tractors 61 and 63 are thus driven in synchronism with the platen 11, the var ious gear ratios being selected so that the paper speed is the same past the tractors and past the platen. In the second position, the gear 69 is moved out of contact with the gear 14 so that the tractors 61 and 63 are free of the platen driving system. This arrangement is illustrated in greater detail in Figure 3. If desired, a solenoid-might-oper- ate the lever or an electrically operated clutch might be employed.

In addition to moving the gear 69 out of engage ment with the drive train gear 14, operation of the lever 73 also causes a tang 77 on the plate 71 to actuate a microswitch 79. Microswitch 79 signals the lever setting to the microprocessor control sys tem which coordinates the operation of the overall printer system.

Claims (5)

1. A forms handling system for a printer com prising a horizontal roller platen, at the front side of said platen, transversable print head means for printing on paper overlying said platen guide, means for guiding a cut sheet from above tan gentially into contact with the rear of said platen, means for feeding continuous form paper tan gentially into contact with the bottom of said platen, motor means for driving said platen in rotation for feeding paper past said print head, and clutch means operative in a first state for driving said feeding means from said motor means syn chronously with said platen and, in a second state, releasing said feeding means from said platen drive means, whereby continuous forms can be held ready in said tractor means while printing takes place on cut sheet paper.

2. A forms handling system as claimed in claim 1, in which said guiding means includes pressure rollers, said feeding means includes a pair of trac tor assemblies adapted to feed edge perforated pa per, and said clutch means comprises lever operable clutch means operative in a first position for driving said tractor means from said motor means synchronously with said platen and, in a second position, releasing said tractor means from said platen drive means, whereby continuous forms can be held ready in said tractor means while printing takes place on cut sheet paper.

3. A forms handling system for a printer com prising a horizontal roller platen, a transversable printhead and carriage assembly for printing along a print line extending along said platen on paper overlying said platen, means for selectively driving said printhead along a print line of preselected length and to an extreme position which is beyond one end of the print line, a bail assembly including a bar carrying a plurality of rollers for holding paper against said platen adjacent the print line, said bar being carried on a pair of pivoting arms for moving between a retracted position and an operative position in which the rollers are in contact with said platen, over-centre spring means for maintaining the bail assembly stably in either the retracted or the operative position, and a cam for driving said arms between said operative and retracted positions, said cam having surfaces which engage corresponding surfaces on said printhead carriage as said carriage approaches said extreme position, the arms being moved to the retracted position as the carriage approaches the extreme position and to the operative position as the carriage departs said extreme position.

4. A forms handling system as ciaimed in claim 3, in which said cam comprises a C-shaped rocker cam, said cam having first and second surfaces which engage corresponding first and second surfaces on said printhead carriage as said carriage approaches and departs said extreme positions respectively, the arms being moved to the retracted -position as the carriage approaches the extreme position and to the operative position as the carriage departs said extreme position.

5. A forms handling system substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.