GB2252532A - Achieving paper tension at point of printing - Google Patents

Abstract

In a selective printer of the kind using continuous forms, wherein the web is fed by two paper tractors which have the point of printing located between them, a sensor determines whether an openable part of the machine housing has just been closed, and control circuitry manipulates the tractors so as to correctly tension the web at the point of printing in response to the act of closing the lid. As described, there is a single motor driving both tractors, and the tractor which is downstream of the point of printing (in the direction of paper movement during printing) is connected thereto via a clutch, so that the upstream tractor can be reversed without simultaneously reverse-driving the downstream tractor. When the control system detects the act of closing the lid of the casing, the motor is driven in reverse, whereby only the upstream tractor is reversed, thereby tensioning the web between the tractors. In order to reduce backlash, both tractors may be advanced by a predetermined amount after tensioning of the paper. The clutch may be a one-way spring clutch, or may be electrically operated or may be mechanically disengaged by coaction with the printhead carriage when the latter is deliberately traversed to its extreme marginal position. <IMAGE>

Description

PAPER FEEDER FOR FEEDING CONTINUOUS PAPER TO PRINTER The present invention relates to a paper feeder for feeding continuous paper to a printer, and particularly, to a paper feeder capable of removing the slack of the continuous paper in accordance with the opening and closing movement of the cover which covers the print mechanism.

A technique concerning a paper feeder which removes the slack of the continuous paper is disclosed in Japanese Laid-Open Patent Publication No. 2-131972. In the above technique, the pin tractor is forward rotated by a key operation of a forward feed switch after disposition of the continuous paper on the upstream pin tractor, so that the paper is fed. And then, the paper is set in the downstream pin tractor, and only the upstream pin tractor is reversely rotated by the key operation of reverse feed switch, so that a tension is applied to the continuous paper and the slack of the continuous paper is removed.

In the paper feeder as described above, the paper feed is started by a key operation or the like, and the slack of paper between the two tractors can be removed.

However, the above explained paper feeder requires a key operation in order to remove the slack of the paper, with concomitant problems including . cumbersome operation for an operator despite a more simplified operation compared to - conventional paper feeders.

Accordingly, such a constitution as to remove the slack of the paper without any cumbersome operation of a key operation for the operator has been demanded.

The present invention is made in consideration of the above explained demand, and an object of the present invention is to provide a paper feeder capable of automatically removing any slack in the continuous paper without any special key operation.

A further object of the present invention is to provide a paper feeder capable of removing any slack of the continuous paper easily and certainly by a simple operation.

Another object of the present invention is to provide a paper feeder capable of applying uniform tension to continuous paper without increasing a burden to the operator.

To achieve the above and other objects, there is provided, according to the present invention, a feeder for a printer, comprising: a platen disposed along the widthwise direction of a transportation path of a continuous web; two or more pin tractors having a plurality of movable pins, one pin tractor being arranged upstream and one pin tractor being arranged downstream of said platen on the transportation path, and capable of transporting the continuous web according to the movement of the pins upon engagement of the pins with feed holes formed on the continuous web; a drive source for providing driving rotation in forward and reverse direction; a transmission mechanism for transmitting the rotational drive of said drive source to said pin tractors; clutch means for controlling power transmission between said drive source and said downstream pin tractor;; a cover for opening and closing the printer to give access to the transportation path; detector means for detecting the closing of said cover; and control means which control the drive source on the basis of an output from said detector means upon closure of said cover, to rotate reversely, such that the continuous web is retracted by the upstream pin tractor, wherein the clutch is released when the reverse drive is applied, wherein the clutch does not transmit said reverse drive to the downstream tractor.

According to a paper feeder thus constructed, the clutch means is released on the basis of the output from the detector means upon the opening or closure of the cover. Consequently, the power is transmitted to the upstream pin tractor while not to the downstream pin tractor. In this state, the rotational drive in the reverse direction is applied to the pin tractors so that the paper is retracted. Since the power cannot be transmitted to the downstream pin tractor, the downstream pin tractor is not rotated till the application of tension to the paper. Upon application of the tension to the paper, the downstream pin tractor is also driven. In this stage, the rotation is stopped and the clutch means is engaged so that the paper is stretched across both pin tractors without any slack.

According to the present invention as apparent from the above description, the slack of the paper can be automatically removed in association with the opening/closing of the cover in setting the paper, thereby exhibiting an excellent effect not to force an extra operation such as a key operation on an operator.

The invention will be further described by way of non-limitative example with reference to the accompanying drawings in which: Fig. 1 is a partially broken cross-sectional view of a paper feeder in a first preferred embodiment; Fig. 2 is a partially broken cross-sectional view of each pin tractor with a pin belt in the paper feeder; Fig. 3 is a front view showing a downstream tractor unit of the paper feeder; Fig. 4 is a side view showing the downstream tractor unit of the paper feeder; Fig. 5 is a partially broken cross-sectional view showing tractor gears of the paper feeder; Fig. 6 is a block diagram of a circuit for controlling the paper feeder; Fig. 7 is a flowchart illustrating the contents of the control; Fig. 8 is an exploded perspective view showing the principal parts of a paper feeder in a second embodiment;; Fig. 9 is a longitudinal cross-sectional view showing the periphery of the connector member of the paper feeder; Fig. 10 is a block diagram of a circuit showing the drive mechanism of a carriage; Fig. 11 is a flowchart illustrating the control of the paper feeder; Fig. 12 is a side view of the paper feeder of the Fig. 8 embodiment.

Fig. 13 is a top view of the carriage of the Fiq. 8 embodiment.

Preferred embodiments according to the present invention will be explained hereunder with reference to the drawings.

First of all, a first embodiment will be described referring to the drawings.

As shown in Figs. 1 and 2, in a printer case 1, a platen 2 is rotatably supported by a platen shaft 3 on the transportation path of continuous paper web P in the widthwise direction of the paper P. At one end of the platen shaft 3 is fixed a platen gear 4. A paper guide plate 6 with a plurality of paper press rollers 5 rotatably supported thereon is arranged under the platen 2. A printing head 7 capable of reciprocating along the platen 2 is disposed in front of the platen 2. A cover 50 for opening and closing the upper portion of the printing head 7, a switch 51 for detecting the open or closed state of the cover 50 and a paper bail 52 are also provided.

A downstream tractor unit 8 is arranged downstream of the platen 2 on the transportation path of the continuous paper web P. As shown in Figs. 1 through 5, the tractor unit 8 comprises a pair of side plates 9 detachably attached at the right and left ends of the platen shaft 3, a transmission shaft 10 and guide shaft 11, both extending parallel to the platen 2 between both side plates 9. A pair of right and left downstream pin tractors 12 are supported on both shafts 10 and 11 for movable adjustment in the widthwise direction of the continuous paper P, and a paper rest 13 (Fig. 3) supported on both shafts 10 and 11 between both pin tractors 12.

As illustrated in Figs. 1 and 4, attachment recesses 9a, engaged with both ends of the platen shaft 3, are formed in a part of each side plate 9. Inside each side plate 9, an engagement lever 14 is disposed to pivot about a spindle 14a. A tension spring 15 is engaged at one end to the engagement lever 14 and at the other end to frame 9. A hook 14b is disposed at the tip end of lever 14 and is engaged with an engagement pin 16 disposed in the printer case 1 by the spring force from spring 15. To remove the downstream tractor unit 8 from the printer, the engagement lever 14 is turned against the spring force of the tension spring 15 so that the hook 14b is disengaged from the engagement pin 16, thereby allowing the recesses 9a to be moved out of engagement with the platen shaft.

As shown in Figs. 1 through 3, the downstream pin tractor 12 is provided with a tractor frame 17. The pin tractor 12 includes a drive pulley 18 and a driven pulley 19 rotated integrally with the transmission shaft 10. A pin belt 20 having a plurality of pins 20a is trained over the pulleys 18 and 19. As shown in Fig. 3, the pins 20a are engaged with feed holes Pa of the continuolls paper web P, and the continuous paper P is fed according to the circumferential movement of the pins 20a. In the tractor frame 17, a paper holding plate 21 is mounted in such a manner as to be switched from a lying position, as shown by solid lines in Fig. 1 to hold the continuous paper web P on the pint belt 20, to a standing position, as depicted by two dot chain lines in Fig. 1, in which the continuous paper web P is allowed to be placed on or removed from the pin belts 20.

A tractor gear 22 is attached at the end of the transmission shaft 10 outside one of the side plates 9. A one-way clutch 22a, for example, a spring clutch or the like, is disposed to allow the transmission shaft 10 to rotate forward, i.e., only in the direction indicated by an arrow A and to prevent it from being driven in reverse.

In addition, intermediate gears 23 rotatably supported on the side plates 9 are meshed with the corresponding tractor gears 22, and the tractor gears 22 are connected in engagement with the platen gears 4 via the intermediate gear 23. As shown in Figs. 3 and 5, each of the sets of gears 22, 23 and shafts 10, 11 are covered with covers 24 disposed outside both side plates 9.

Meanwhile, as illustrated in Figs. 1 and 2, an upstream tractor unit 25 is provided upstream -of the platen 2 on the transportation path of the continuous paper web P. The tractor unit 25 has a transmission shaft 26 and a guide shaft 27 both extending parallel to the platen 2 and rotatably supported on the printer case 1.

On both shafts 26, 27, a pair of right and left upstream pin tractors 28 capable of being adjusted movably in the widthwise direction of the continuous paper P are supported.

The upstream pin tractors 28 are constituted in the same manner as the downstream pin tractors 12.

Between a drive pulley 30 fitted around the transmission shaft 26 through a tractor frame 29, and a driven pulley 31 supported by the tractor frame 29 is crained a pin belt 32 having a plurality of pins 32a. Furthermore, a paper holding plate 33 is mounted for movement from a lying position to a standing position on the tractor frame 29.

As depicted in Fig. 1, a tractor gear 34 is fixed at the end of the transmission shaft 26 outside the upstream pin tractor 28. The tractor gear 34 is linked with the platen gear 4 via a pair of intermediate gears 35, 36 rotatably supported on the printer case 1. Motor gear 38 of reversible paper feed motor 37 is in engagement with the intermediate gear 35.

In this embodiment, a transmission mechanism constituted by the gears 4, 22, 23, and 34, 35 and 36 is driven by the paper feed motor 37, and transmits rotation to the upstream and downstream pin tractors 28, 12.

Subsequently, the electrical constitution of the paper feeder will be explained with reference to Fig. 6.

The paper feeder in this embodiment is provided with a microcomputer (hereinafter referred to as "MC") 41 as control means for controlling the operation of the paper feed motor 37. The MC 41 previously stores therein a control program of the paper feed motor 37. The MC 41 receives a forward rotation signal from a forward feed switch 42 activated for rotating the paper feed motor 37 forward via an input/output interface 43. Moreover, the MC 41 receives a signal from a detector switch 51 through the input/output interface 43.

Consequently, in setting the continuous paper P, when an operator activates the forward feed switch 42 in the engaged state of the feed holes Pa at the tip end of the continuous paper P with the pins 32a of the upstream pin tractor 28, the MC 41 receives the forward rotation signal to rotate the paper feed motor 37 forward by a predetermined amount on the basis of the signal so as to apply the predetermined amount of forward rotation to the continuous paper P. Therefore, the rotational movement is transmitted to the upstream and downstream pin tractors 28 and 12 via the gears 4, 22, 23 and 34 through 36, respectively, and then, the pins 32a, 20a of the pin tractors 28, 12 are moved forward so that the tip end of the paper can be fed forward from the upstream pin tractor 28 to the paper bail 52 via the space between the platen 2 and paper press roller 5.

The cover 50 is opened after manual rotation of the platen 2, or after the further forward rotation to such an extent that the tip end of the continuous paper web P is set in the downstream pin tractor 12 by the forward feed switch 42, and the feed holes Pa at the tip end are engaged with the pins 20a of the downstream pin tractor 12. In this setting, since the continuous paper web P must be set with slack to lessen the possibility of disengagement of the pins 20a of the downstream pin tractor 12 from the feed holes Pa of the continuous paper web P, the continuous paper web P is set with a slight slack between the platen 2 and the downstream pin tractor 12.

After that, when the cover 50 is closed (in S1 in Fig. 7), the MC 41 drives to rotate the paper feed motor 37 forward on the basis of an output from the detector switch 51, for forward transportation of the continuous paper web P by a predetermined amount (in S2 in Fig. 7).

This first forward transportation ensures that the continuous paper P is not disengaged from the downstream pin tractors 12, when the web is moved in the reverse rotation, as described later, even if only a short portion of the continuous paper web P is engaged with the pin tractors 12 when the paper is placed in the downstream tractor unit. Subsequently, the MC 41 drives to rotate the paper feed motor 37 in reverse by a predetermined amount for retracting the continuous paper web P by the predetermined amount (in S3 in Fig. 7). Accordingly, rotational movement can be transmitted to the upstream pin tractors 28 via the gears 34, 35 and 38.At this time, the power transmission to the downstream pin tractors 12 can be cut off by the one-way clutch 22a so that only the pins 32a of the upstream pin tractors 28 can be moved in the reverse direction, and the continuous paper web P is retracted in the reverse direction from the downstream pin tractors 12 toward the upstream pin tractors 28 only by the upstream pin tractors 28. The retracted distance is such that the continuous paper web P is not disengaged from the downstream pin tractors 12 and that the upstream pin tractors 28, by reason of the retraction of the continuous paper P, are slightly rotated in the reverse direction. Preferably, the amount of retraction is larger than the transportation amount in the forward direction in S2. As a result, a tension is applied to the continuous paper P, thereby removing the slack of the paper P.

In this state, where the slack of the paper is removed as described above, the MC 41 drives to rotate the paper feed motor 37 forward by a predetermined amount again subsequently to the reverse rotation and stop the motor 37 (in S4 in Fig. 7), and further, waits for a print operation. Therefore, a backlash generated among the gears 4, 22, 23 and 34 through 36 can be eliminated, and the engagement of the feed holes Pa of the continuous paper P with the pins 32a, 20a can be secured.

In the embodiment explained above, a simple closing operation of the cover 50 enables the slack to be removed easily and certainly. The closing operation of the cover 50 has to be performed manually even in the conventional paper feeders, and it does not increase the burden to the operator. In addition, when the slack is removed from the paper, a uniform tension can be applied to the continuous paper web P by the drive force of the paper feed motor 37, thereby realizing smooth paper feed all the time.

Many other types of clutches can be used. For example, the one-way clutch 22a as the clutch means may be replaced with an electromagnetic clutch, which allows or inhibits the transmission shaft 10 of the downstream pin tractors 12 to be driven.

In this embodiment, the downstream tractor unit 8 is detachable, but it may be assembled inside the printer together with the upstream tractor unit. In this case, it is unnecessary that the distance between both pin tractor units is precisely adjusted to fit to the feed holes of the continuous paper, and moreover, differences caused by variations in the continuous paper web feeding mechanisms can be accommodated. Otherwise, part of the construction can be modified without departing from the scope of the invention.

Next, a second embodiment according to the present invention will be explained hereunder. The cover and detector means in the second embodiment is the same as those in the first embodiment, so the description thereof is omitted.

The central shaft 102 of a platen 101 is rotatably supported in a printer unit 103 (see Fig. 13). At the end of the central shaft 102 is fitted a platen gear 104 (see Fig. 8) meshed with a motor gear 105 connected to a paper feed motor 150. In front of the platen 101, a carriage 140 is mounted on guide shafts 143, 145 for movement along the platen 101. The carriage 140 moves laterally along the platen 101 according to the drive of a carriage motor 164 described later. On the carriage 140 are disposed a printing head 106 and a ribbon cartridge 146. The printing head 106 is laterally moved along the longitudinal direction of the platen 101 together with the lateral movement of the carriage 140, thus performing the print operation.

Meanwhile, as shown in Fig. 12, a plurality of paper holding rollers 108 are rotatably supported by a paper guide plate 107 disposed under the platen 101.

Print paper 110 is inserted between the paper holding rollers 108 and the platen 101. At the right and left behind the platen 101 a pair of upstream pin tractors 111 for feeding the print paper 110 to the platen 101 are respectively provided upstream of the platen 101 on the transportation path of the continuous paper 110. Each of the upstream pin tractors 111 is supported by a square drive shaft 112 and a guide shaft 113 each extending in parallel along the platen 101 for positional adjustment in the widthwise direction of the print paper 110. A pin belt 116 is trained over a drive pulley 114 fitted around the drive shaft 112 and a driven pulley 115 spaced from the drive pulley 114. The pin belt 116 is rotated while the sprocket holes 117 (see Fig. 8) at both side edges of the print paper 110 are engaged with pins 116a formed on the pin belt 116, thereby feeding the print paper 110.

The upstream pin tractors 111 each having the above described constitution are driven by a known connection member such as a gear train and a timing belt (not shown) in association with the rotation of the platen 101.

Downstream pin tractors 120 for pulling the print paper 101 fed from the platen 101 are installed downstream of the platen 101 on the transportation path of the continuous paper web 110.

The downstream pin tractors 120 are supported by a drive shaft 122 and a guide shaft 123 each rotatably supported in the printer unit 103. In this embodiment, the drive shaft 122 is formed into a square shape, and a pair of drive pulleys 124 are fitted at the right and left around the drive shafts 122 (see Fig. 12). A pair of driven pulleys 125 are fitted at the right and left around the guide shaft 123, and pin belts 126 are trained on the driven pulleys 125 and the drive pulleys 124, respectively. The print paper 110 is pulled from the platen 101 by rotating the pin belts 126 on both sides while engaging the sprocket holes 117 formed at both side edges of the print paper 110 with pins 126a formed on the pin belts 126.The pair of right and left drive pulleys 124 and driven pulleys 125 are slidable in the axial direction of the drive shaft 122 and guide shaft 123, and the distance between the pin belts 126 on both sides can be adjusted to the width of the print paper 110 with the slide.

Next, a gear train 127 constituting the connection member for driving the downstream pin tractors 120 so constituted as described above will be explained with reference to Fig. 8.

The gear train 127 consists of the platen gear 104 rotated integrally with the platen 101, an intermediate gear 128 meshed with the platen gear 104, and a drive gear 129 meshed with the intermediate gear 128. In this case, the intermediate gear 128 is rotatably supported in a shaft 130 horizontally fixed to the printer unit 103 as shown in Fig. 9. The drive gear 129 is fitted on the drive shaft 122 slidably in the lateral direction. Since the drive shaft 122 is formed into a square shape having substantially the same size as that of the engagement hole 129a of the drive gear 129, the drive gear 129 is rotated integrally with the drive shaft 122, to thus rotate the pin belt 126. As depicted in Fig. 9, compression spring 132 is interposed between the drive gear 129 and a bearing 131, and the drive gear 129 is urged in the left by the resilient force.The left position of the drive gear 129 is restricted by a presser 153 formed in a fork lever 157 as a cut-off member described later, and the drive gear 129 is brought into mesh with the intermediate gear 128 in a position indicated by the solid line position in Fig. 9 (this state is hereinafter referred to as "a meshed state").

The fork lever 157 as the cut-off member for cutting off the meshed state between the drive gear 129 and intermediate gear 128 is rotatably supported on a support shaft 154 in a support table 103a of the printer unit 103 by the support shaft 154. A pin 155 is suspended at the end 156 of the fork lever 157 on the carriage 140 side. The pin 155 abuts against the carriage 140 when the carriage 140 is moved in the left to arrive at a predetermined position. The carriage 140 is further moved in the left beyond the predetermined position so that the pin 155 is moved in the left, thus turning the fork lever 157 clockwise on the support shaft 154.

Meanwhile, the presser 153 is suspended at the end 151 of the fork lever 157 on the drive gear 129 side. The presser 153 is moved in the right according to the clockwise turning of the fork lever 157. Consequently, the drive gear 129 is slid to the right against the spring 132 to release the meshed state of the intermediate gear 128, as illustrated by a two dot chain line position in Fig. 9.

When the drive gear 129 and the intermediate gear 128 are in the released state, rightward movement of the carriage 140 enables the fork lever 157 to turn counterclockwise and the presser 153 is moved in the left, so that the drive gear 129 slides to the left by the resilient force of the spring 132, thereby returning to the meshed state between the drive gear 129 and the intermediate gear 128.

In this embodiment, in order to facilitate the mesh and the release by the slide of the drive gear 129 and intermediate gear 128, both gears 129 and 128 are formed into tapered shapes as shown in Fig. 9, and moreover, the platen gear 104 and motor gear 105 are also formed into tapered shapes corresponding to the shapes of the gears 129, 128. The counterclockwise turning of the fork lever 157 is limited by a suitable member (not shown) within a position where the meshed state between the drive gear 129 and the intermediate gear 128 can be held by the presser 153.

At the upper surface of the downstream pin tractor 120 as shown in Fig. 8, a paper holding cover 137 for preventing the disengagement of the print paper 110 from the pin belt 126 is mounted openably with respect to the upper surface of the pin belt 126. (As to the left downstream pin tractor 120, the illustration of the paper holding cover 137 is omitted.) In the upstream pin tractors 111 illustrated in Fig. 12 are disposed paper holding covers (not shown) in the same manner as the downstream pin tractors 120.

Subsequently, the drive mechanism of the carriage 140 will be explained with reference to Fig. 10.

In Fig. 10, a CPU 162 is connected to a carriage driver 163 for driving the carriage motor 164 according to a command output from the CPU 162. The carriage motor 164 moves the carriage 140 laterally along the longitudinal direction of the platen 101 upon being driven by the carriage driver 163. In addition, a paper feed switch 170 is disposed on the upper surface or whole surface of the housing of the printer unit 103. The paper feed switch 170 is adapted to input a paper feed command to the CPU 162, and the CPU 162 outputs a drive command to a paper feed driver 171 according to the operation of the paper feed switch 170.The paper feed driver 171 is adapted to drive the paper feed motor 150 according to the command from the CPU 162, for rotating the platen 101 via the motor gear 105 and platen gear 104 in the direction indicated by an arrow in Fig. 12 upon drive of the paper feed motor 150. Simultaneously with the rotation of the platen 101, the CPU 162 rotates the drive shaft 122 connected to the platen 1 via the platen gear 104, intermediate gear 128 and drive gear 129, and the drive shaft 112 connected to the platen 101 through the suitable connector member such as a timing belt (not shown) in the direction indicated by arrows in Fig. 12, respectively.

Accordingly, the pin belts 126, 116 are rotated in the directions indicated by arrows according to the rotation of the drive shafts 122, 112 in the direction indicated by the arrows, respectively, to transport the print paper set in the upstream pin tractors 111 and downstream pin tractors 120 from the upstream pin tractors 111 to the downstream pin tractors 120 through the platen 101.

Subsequently, the operation of the paper feed mechanism in the printer so constituted as described above will be explained referring to Fig. 11.

In setting the print paper 110, first of all, the print paper 110 is guided to the pin belts 116 of the upstream pin tractors 111, and the sprocket holes 117 are engaged with the pins 116a of the pin belts 116 (in Fig.

12). After both side edges of the print paper 110 are covered with the paper holding covers (not shown) mounted on the upstream pin tractors 111, the paper feed switch 170 is operated to drive the paper feed motor 150 so that the platen 101 and pin belts 126, 116 are rotated in the directions indicated by the arrows via the aforementioned gear train, respectively. The print paper 110 is fed to such an extent that the tip end thereof can be disposed in the downstream pin tractors 120 according to the rotation of the platen 101 and pin belts 126, 116 in the same manner as the first embodiment, and the operation of the paper feed switch 170 is completed to stop the drive of the paper feed motor 150. Next, the sprocket holes 117 of the print paper 110 are engaged with the pins 126a of the pin belts 126, to be thus covered with the paper holding covers 137.In this state, the drive gear 129 of the downstream pin tractors 120 is meshed with the intermediate gear 128 (indicated by a solid line in Fig. 9), and the fork lever 157 is located in a position indicated by a solid line in Fig. 13. Upon closure of a cover 182 shown in Fig. 11 and detection of the operation of a detector switch 180 by the CPU 162 (S21), the CPU 162 rotates the paper feed motor forward similarly to the case in the first embodiment, to secure the adequate amount of the paper to be engaged with the downstream pin tractors 120 (S22). Subsequently, the carriage 140 is moved in the left after right movement in the same way as a normal initialization, to be come into a halt in a home position at the left end (S23, S24).Together with the left movement of the carriage 140, a part of the carriage 140 abuts against the pin 155 formed in the fork lever 157 so that the fork lever 157 is turned clockwise on the support shaft 154. According to the clockwise turning of the fork lever 157, the presser 153 is also moved in the right to press the drive gear 129 in the right. Consequently, the drive gear 129 slides to the right against the spring 132, thus coming into a released state from the meshed state with the intermediate gear 128 (a state indicated by a two dot chain line in Fig. 9). In this stage, the drive gear 129 and drive shaft 122 are rotatable independently of the other gears 128, 104, 105 and the central shaft 102 of the platen 101. In this state, the paper feed motor is rotated reversely in the same manner as the first embodiment (S25), to thereby retract the continuous paper 110.

At this time, since the drive gear 129 is released from the intermediate gear 128, the downstream pin tractors 120 cannot be driven by the rotation of the platen 101.

However, once the slack in the web is taken up by the reverse rotation of the upstream pin tractor, the continued pull on the web from the reversely rotating upstream pin tractor causes the downstream pin tractor to be reversely rotated until the reverse drive of the upstream pin tractor is terminated. Accordingly, the slack of the print paper 110 can be removed similarly to the first embodiment. In this stage, the carriage 140 is moved slightly in the right so that the drive gear 129 is meshed with the intermediate gear 128 (S26). And then, the paper feed motor is slightly rotated forward (S27), thereby eliminating the forward backlash in the gear train in the same manner as the first embodiment.

Claims (19)

1. A feeder for a printer, comprising: a platen disposed along the widthwise direction of a transportation path of a continuous web; two or more pin tractors having a plurality of movable pins, one pin tractor being arranged upstream and one pin tractor being arranged downstream of said platen on the transportation path, and capable of transporting the continuous web according to the movement of the pins upon engagement of the pins with feed holes formed on the continuous web; a drive source for providing driving rotation in forward and reverse directions; a transmission mechanism for transmitting the rotational drive of said drive source to said pin tractors; clutch means for controlling power transmission between said drive source and said downstream pin tractor; a cover for opening and closing the printer to give access to the transportation path;; detector means for detecting the closing of said cover; and control means which control the drive source on the basis of an output from said detector means upon closure of said cover, to rotate reversely, such that the continuous web is retracted by the upstream pin tractor, wherein the clutch is released when the reverse drive is applied, wherein the clutch does not transmit said reverse drive to the downstream tractor.

2. The feeder according to claim 1, wherein said control means controls said drive source to be rotated reversely in order to retract the continuous web to such an extent that the web is slightly rotated in the reverse direction without disengaging the continuous web from the downstream pin tractor, thereby applying a tension to the continuous web.

3. The web feeder according to claim 1, wherein said control means controls said drive source to rotate forward on the basis of an output from said detector means upon closure of said cover in order to transport the continuous web forward from the upstream pin tractor to the downstream pin tractor, prior to said reverse rotation, whereby the continuous web is not disengaged from the downstream pin tractor by said retraction of the continuous web.

4. The web feeder according to claim 3, wherein said control means causes said drive source to be rotated in reverse to retract the continuous web by a distance greater than the transportation amount in the forward direction, thereby applying a tension to the continuous web.

5. The web feeder according to any preceding claim, wherein said transmission mechanism comprises a plurality of gears.

6. The web feeder according to any preceding claim, wherein said control means causes said drive source to be rotated forward subsequent to the reverse rotation of said drive source and thereafter to be stopped, thereby lessening backlash among the plurality of gears and securing engagement of the feed holes of the continuous web with the pins.

7. A web feeder according to any preceding claim wherein the clutch is released when the reverse drive is applied.

8. A web feeder according to any preceding claim wherein the clutch does not transmit said reverse drive to the downstream tractor.

9. A web feeder according to any preceding claim wherein: the clutch means transmits power between said drive source and said downstream pin tractor when said drive source rotates in the forward direction and cuts off power transmission between said drive source and said downstream pin tractors when said drive source rotates in the reverse direction.

10. A web feeder according to any one of claims 1 to 7 further comprising: a carriage movable along said platen; and clutch control means; and wherein the clutch means is movable between a first position and a second position, for transmitting power from said drive source to said pin tractors when in the first position and for cutting off power transmission between said drive source and said downstream pin tractors when in the second position; the clutch control means moving said clutch means to the second position upon detection of the closure of said cover.

11. The web feeder according to claim 10, wherein said carriage is movable laterally along said platen, and said control means further controls said carriage to abut against the clutch control means to move said clutch means to the second position.

12. The web feeder according to claim 10 or 11 wherein the clutch and clutch control means comprise: a transmission member for transmitting power to said downstream pin tractor; an operating member pivotably supported on a support shaft fixed on the printer; and an urging means for urging said transmission member toward the first position.

13. The web feeder according to claim 12, wherein said carriage is movable to abut against a first end of said operating member, a second end of said operating member is arranged to engage said transmission member, and said transmission member and said operating member are movable to the second position against the urging force generated by said urging means.

14. The web feeder according to claim 12 or 13 wherein said operating member has pins suspended therefrom and said carriage abuts said pins and rotates said operating member when said carriage is moved to a home position at one end of the platen.

15. The web feeder according to claim 12, 13 or 14, wherein said transmission member comprises a gear, said operating member comprises a lever and said urging means comprises a spring.

16. The web feeder according to claim 15, wherein said gear is tapered, and operable to engage with a second tapered gear in the transmission mechanism when in the first position.

17. The web feeder according to claim 14, wherein said control means moves said carriage in a direction away from said home position, whereby said transmission member and said operating member are moved to the first position by the urging force of said urging means, after said carriage is moved away from its home position.

18. A web feeder constructed and arranged to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

19. A printer including a web feeder according to any one of the preceding claims.