GB2168291A - Printer paper handling system - Google Patents

Abstract

A printer comprises a roller platen 11, a printhead carried on a traversable carriage, a paper bail assembly 51, an overcentre spring device for maintaining the bail assembly in either a platen-engaging or a retracted position, and a drive motor 41 for driving the printhead along a line of print. When it is required to insert a new sheet of paper or a continuous form of stationery, the carriage is driven to an extreme position beyond the end of the print line where a cam 83 is engaged by fixed surface 87 to cause rotation of the cam and pivoting of the bail assembly to the retracted position. A second surface engages the cam on the return motion to restore the bail against the paper. <IMAGE>

Description

GB 2 168 291 A 1

SPECIFICATION

Printer paper handling system The present invention relates to a paper and forms 5 handling system for a printer and more particularly 70 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 10 implementthe paper handling mechanism of a 75 printersothat both cutsheet and continuousforms can be handled, itwas necessaryto completely removethe continuousforms paperfrom thetractors typically utilized to feed such paperwhile printing 15 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 20 intervention was particu la rly wasteful in the context of an office environment where frequent changeovers between continuous paper and cut sheet are typical in the dailyflow of work.

Among the several objects of the present 25 invention, may be noted the provision of a forms and 90 paper handling system for a printerwhich permits continuous formsto be held ready while printing takes place on cut sheet paper; the provision of such a system in which cut sheets may be simplyfed to a 30 roller plaien 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 35 which is highly reliable; the provision of such a system which is userfriendly; 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 40 hereinafter.

The present invention is a forms handling system for a printer comprising a horizontal roller platen, a transversable printhead and carriage assemblyfor printing along a print line extending along said 45 platen on paperoverlying said platen, meansfor 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 50 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 meansfor 55 maintaining the bail assembly stably in eitherthe retracted orthe 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 60 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.

65 An embodiment of the present invention will now 130 be described, by way of example, with reference to the accompanying drawings, in which:Fig. 1 is a perspective drawing of a printer mechanism constructed in accordance with the present invention viewed from above and f rom the right front corner; Fig. 2 is a perspective drawing of the mechanism of Fig. 1 viewed from above and from the right rear corner showing forms tractors used in the mechanism; Fig. 3 is a side view from the right showing a leveroperating clutch mechanism for selectively disengaging the forms tractors; Fig. 4 is an exploded view of a portion of the 80 mechanism showing a cam which operates a paper bail; and Fig. 5 is atopviewof a portion of the mechanism illustrating the interaction of thecam with a fixture on the print head carriage.

Corresponding reference characters indicate corresponding parts th roug hout the several views of the drawings.

Referring nowto Fig. 1, there is indicated by reference character 11 a conventional roller platen, i.e., a platen of thetype conventionally employed in typewriters. Platen 11 is driven,through a train of gears 1315from 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 Fig. 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 33 100 provides an endless ribbon, a portion of which 35 extends along the platen. Thus, by appropriate energizing of the printhead 25, printed characters may beformed on a piece of paper overlying the platen 11. Preferably, the printhead carries a rotary 105 ribbon shifter37 forvertically positioning the ribbon, e.g., to select different colou red stripesthereon.

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 110 gearing 43 and an endless cogged belt 45 which passes over pulleys 47 adjacent each of the ends of th guides 31. Coordination of the operations of the several motors and the dot-matrix printhead is preferably controlled by a dedicated microprocessor/ 115 firmware system as is conventional in the present state of the art.

Paperfollowing 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).

120 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 thatthe bail assembly is 125 stably held in either of two positions, an engage position in which the rollers are pressed againstthe platen 11 and a disengaged position in which the rollers are swung back awayfrom the platen, e.g., for initially inserting a new sheet of paper.

In normal printing, the printhead carriage 27 GB 2 168 291 A 2 traverses most but not all of the travel diptance accommodated by the guides 31. In accordance with another aspect of the invention, the carriage can be traversed, by the motor 41 under microprocessor 5 control, to an extreme right hand position where a fixture 81 carried by the carriage can engage a Cshaped 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 10 84 and carries a pin 85 which extends through the end plate of the printerframe and engages a slot 87 in one of the arms 59 which hold the bail rod 51.

As may be seen from Fig. 5, motion of the carriage 27 towards its extreme right hand position will 15 cause a surface 87 on the fixture 81 to engage a mating surface 89 on the cam 83 thereby causing a counterclockwise 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 20 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 25 from its right hand extreme position, a second, pinlike, 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 30 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 35 though the carriage moves further to 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 40 whenever it is appropriate for the operator to insert a new piece of cut paper orto 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 45 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 50 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 55 disclosed herein.

Referring nowto Fig. 2,which showsthe 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.

60 The guide bar 67 is essentially a stationary guide 125 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 shaft 65 carries a spur gear 65 67. An idler gear 69 is mounted on a carrier plate 71 130 which is pivoted around the axis of shaft 65, i.e., its pivot is concentricwith the gear 67. Further, the gear 69 is meshed and engages with the gear 67.

A manually operated lever 73 is pivotally mounted 70 on the end frame piece 19 and is biased towards either of two stable positions by an overcentre 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 75 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 various gear ratios being 80 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 6f contact with the gear 14 so that the tractors 61 and 63 are free of the platen driving system. This arrangement is illustrated in 85 greater detail in Fig. 3. If desired, a solenoid might operate the lever or an electrically operated clutch might be employed.

In addition to moving the gear 69 out of engagement with the drive train gear 14, operation 90 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 system, which coordinates the operation of the overall printer system.

Reference is made to our copending application No. 8516053 from which this application has been divided and which discloses and claims a forms handling system as disclosed herein.

Claims (2)

100 CLAIMS

1. A forms handling system for a printer comprising a horizontal roller platen, a transversable printhead and carriage assembly 105 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 115 which the rollers are in contact with said platen, over-centre spring means for maintaining the bail assembly stably in either the retracted orthe operative position, and a cam for driving said arms between said 120 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.

2. A forms handling system as claimed in claim 1, in which said cam comprises a C-shaped rocker cam, said cam having first and second surfaces which engage corresponding first and second GB 2 168 291 A 3 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.

Printed for Her Majesty's Stationery Office by Courier Press, Leamington Spa. 6/1986. Demand No. 8817356.

Published by the Patent Office, 25 Southampton Buildings, London, WC2A 1AY, from which copies may be obtained.