JP4262114B2 - Printing device - Google Patents

Description

  The present invention relates to a medium transport mechanism such as a printing apparatus.

  In general, in a medium transport mechanism such as a printing apparatus, two transport roller pairs for transporting a medium are arranged in front and rear positions of a print head for recording such as printing, so that a medium of a certain length such as a cut sheet is transported. In this case, a mechanism is adopted in which the inserted medium is carried by the front conveying roller pair while being conveyed and printed by the print head, and then is conveyed by the rear conveying roller.

Also, when transporting continuous media such as continuous paper, to prevent the occurrence of undulation or skew of the media due to variations in the transport amount of the tractor that feeds the continuous media and the transport amount of each transport roller, The printing head performs printing or the like while the medium is transported by the tractor with the roller set in a separated state, and passes through the separated front conveying roller and reaches the rear conveying roller, and the rear conveying roller bites the medium. There is a technique (for example, refer to Patent Document 1).
JP-A-10-279130

  However, in the conventional medium transport mechanism, until the continuous medium is transported by the tractor and the front end of the medium reaches the rear transport roller pair, it is transported only by the transport force of the tractor. As a result, there is a problem that the line feed pitch is not constant. Also, when printing is performed on the trailing edge of the medium when the continuous medium runs out, if the trailing edge of the medium leaves the tractor, it is conveyed only by the rear conveying roller. As a result, there was a problem that the line feed pitch was not constant.

The present invention adopts the following configuration in order to solve the above problems. In other words, the first conveying unit provided in the medium conveying path and driven to convey the medium, an upper rear roller that is rotationally driven, and a lower rear roller that is pressed against the upper rear roller , the first conveying unit on the medium conveying path. A second transport unit that transports the medium, and a second transport unit that is disposed downstream of the second transport unit on the medium transport path. , A third transport unit that transports the medium by a transport amount larger than that of the first transport unit, and a print provided between the second transport unit and the third transport unit in the medium transport path. A head, a platen provided opposite to the print head, and a spring for pressing the lower rear roller against the upper rear roller, and the first conveying means and the second conveying means, A conveyance path formed by the second conveyance unit and the third conveyance unit is bent, and the spring and the first conveyance unit are configured by the second conveyance unit and the third conveyance unit. The spring is pushed down by a tension acting on the medium when the medium is conveyed by the first conveying means and the third conveying means, The upper rear roller and the lower rear roller are separated from each other.

According to the above invention, the medium transporting device includes the first transporting unit that is provided in the medium transporting path and transports the medium, the upper rear roller that is rotationally driven , and the lower rear roller that is pressed against the upper rear roller. A second conveying unit that conveys the medium, and further downstream of the first conveying unit on the path than the second conveying unit on the medium conveying path. A third conveying means that is provided and driven to convey the medium by a larger conveyance amount than the first conveying means; and the second conveying means and the third conveying means in the medium conveying path. A print head provided between the print head, a platen provided opposite to the print head, and a spring for pressing the lower rear roller against the upper rear roller; A conveying path composed of the second conveying means, and a conveying path composed of the second conveying means and the third conveying means are bent, and the spring and the first conveying means are coupled with the second conveying means. The spring is provided below a conveyance path including the third conveyance unit, and the spring is pushed down by a tension acting on the medium when the medium is conveyed by the first conveyance unit and the third conveyance unit. In addition, since the upper rear roller and the lower rear roller are separated from each other, a constant conveying force can be obtained even when processing such as printing on a front end portion and a rear end portion of a fixed length medium or a continuous medium is performed. As a result, when processing such as printing, the medium can be conveyed at a constant pitch, so that high-quality recording or the like can be performed.

  Embodiments according to the present invention will be described below in detail with reference to the drawings, using a widely used impact printer as an example. In addition, the same code | symbol is attached | subjected to the element which is common in drawing.

  In the medium transport mechanism of the first embodiment, one roller of the transport roller pair arranged on the tractor side is pressed against the other roller side by a spring, and the roller pressed by the spring is separated from the other roller by the tension of the medium. It is what you do.

(Constitution)
FIG. 1 shows the configuration of the medium transport mechanism of the first embodiment, FIG. 2 shows a perspective view of the medium transport mechanism, and FIG. 3 shows an enlarged view of the main part of the invention. First, as shown in FIGS. 1 and 2, the medium transport mechanism of the first embodiment includes a print head 1 that performs printing, and an upper rear roller 2a and a lower rear roller 2b that are transport rollers disposed at front and rear positions of the print head 1. The upper front roller 3a, the lower front roller 3b, the tractor 6 for conveying the continuous paper 13, the platen 7 disposed facing the print head 1, the upper rear sheet guide 8 for guiding the conveyance of the printing paper, and the upper front sheet guide. 9, a lower sheet guide 10 and a spring 11 for supporting the lower rear roller 2b.

  Hereinafter, for convenience, the upper rear roller 2a and the lower rear roller 2b are referred to as “rear roller pair 2”, and the upper front roller 3a and the lower front roller 3b are referred to as “front roller pair 3”.

  The upper rear roller 2a, the upper front roller 3a, and the lower front roller 3b are configured to be rotationally driven by a gear or the like (not shown), and the lower rear roller 2b is pressed by a spring 11 as shown in FIGS. It is composed of a pinch roller pressed by Nr. Further, in order to prevent looseness of the continuous paper 13, the transport amount of the front roller pair 3 is set to be larger than the transport amount of the tractor 6.

  Then, as shown in FIG. 3, the lower sheet guide 10 interferes with a triangle having a contact point a between the print head 1 and the platen 7, a contact point b of the rear roller pair 2, and a contact point c of the paper discharge end of the tractor 6 as three apexes. It has a shape that does not.

  If the conveying force obtained by the pair of front rollers 3 is Ff and the pressing force Nr of the spring for giving the conveying force to the lower rear roller 2b, these relationships are as shown in FIG. That is, when the contact point that contacts the continuous paper 13 first when the lower rear roller 2b is pushed up by the spring 11 is the contact point b ′, the pressing direction of the continuous paper 13 formed at the contact point b ′ and the spring 11, that is, the vertical direction, is Since the angle is θ, a force of Ff cos θ is applied as a force for pushing down the lower rear roller 2b by the conveyance force Ff of the continuous paper 13.

  Since the mechanical relationship in which this force and the force supported by the spring 11 balance is Nr = Ff cos θ, the lower rear roller 2b is pushed down by the sheet tension generated by the conveying force of the continuous sheet 13 as will be described later. Nr = α * Ff cos θ, and the α coefficient is 1 or less. According to experiments, the α coefficient is preferably 0.6 to 0.7.

(Operation)
With the above configuration, the medium transport mechanism according to the first exemplary embodiment operates as follows.

(In the case of cut paper)
First, as shown in FIG. 5, when the cut sheet 12 is conveyed, the cut sheet 12 inserted from the direction of the arrow B on the right side of the figure is held by the front roller pair 3 and conveyed, and the print head 1 Printing is started by the platen 7. The cut sheet 12 conveyed to the rear roller pair 2 by the conveying force Ff of the front roller pair 3 and reaching the rear roller pair 2 is combined with the rear roller pair 2 to which the conveying force Fr is applied by the spring 11 and the front roller pair 3. The leading edge of the cut sheet 12 is discharged in the direction of arrow B ′ on the left side of the figure.

(For continuous paper)
When the continuous paper 13 is transported, the continuous paper 13 set on the tractor 6 is transported to the rear roller pair 2 by the transport force Ft of the tractor 6 in the direction of arrow A and reaches the rear roller pair 2 as shown in FIG. Then, the leading edge of the sheet is caught in the rear roller pair 2 and conveyed to the position of the print head 1, printing is started by the print head and the platen 7, and conveyed to the front roller pair 3. The conveyance force of the continuous paper 13 during this period is conveyed by the conveyance force Fr applied to the lower rear roller 2b by the conveyance force Ft of the tractor 6 and the spring 11, that is, Ft + Fr.

  Then, as shown in FIG. 7, the continuous paper 13 that has reached the front roller pair 3 is bitten by the front roller pair 3 and conveyed by the conveying force Ff. At this time, tension is generated in the continuous paper 13 by the paper discharge end (contact c in FIG. 3) of the tractor 6 and the conveying force Ff of the front roller pair 3, and the lower rear roller 2b pushed up by the spring 11 is used as the lower sheet guide. It is pushed down to the 10 position.

  Then, since the rear roller pair 2 is in the separated state, its conveying force Fr becomes “0”, and the continuous paper 13 is conveyed by the conveying force Ft of the tractor 6 and the conveying force Ff of the front roller pair 3. During printing of each line, the driving of the tractor 6 and the front roller pair 3 is stopped, but the continuous paper 13 is fixed by the paper discharge end (contact c in FIG. 3) of the tractor 6 and the front roller pair 3, so that the fixed sheet 13 is constant. Is maintained stably at a position balanced with the pushing force of the spring 11 to the lower rear roller 2b.

  Then, as shown in FIG. 8, when the continuous paper 13 runs out and the trailing edge of the continuous paper 13 is removed from the tractor 6, the tension of the continuous paper 13 becomes "0", and the lower rear roller 2b is pushed up by the spring 11 and is again transported. Since Fr is given, it is transported by the transport force Ff + Fr and discharged in the direction of the arrow A ′ on the right side of the figure.

  As described above, the medium transport mechanism of Embodiment 1 can obtain a stable transport force as follows.

  (1) In the case of single sheet conveyance, the conveyance force of the front roller pair 3 and the conveyance force of the rear roller pair 2, that is, Ff + Fr is obtained.

  (2) When the continuous paper is conveyed, until the leading edge of the continuous paper reaches the front roller pair 3, the conveyance force of the tractor 6 and the conveyance force of the rear roller pair 2, that is, Ft + Fr are obtained.

  (3) After the leading edge of the continuous paper reaches the front roller pair 3, the lower rear roller 2b is pushed down by the tension of the paper, so that the conveying force of the tractor 6 and the conveying force of the front roller pair 3, that is, Ft + Ff are obtained.

  (4) When the trailing edge of the continuous sheet comes off the tractor 6, the tension of the sheet is lost, and the lower rear roller 2b is pushed up again by the spring 11. Therefore, the conveying force of the front roller pair 3 and the conveying force of the rear roller pair 2, that is, Ff + Fr Can be obtained.

(Effect of Example 1)
As described above, according to the medium transport mechanism of the first embodiment, even when the cut sheet is transported, even when the continuous paper is transported, the leading edge and the trailing edge are constant. Since the conveying force can be obtained, high-quality printing can be performed at a constant pitch.

  Further, since the rear roller 2 pair is separated by the tension of the paper, a mechanism component such as a change lever for separating the roller pair and a position sensor and a control circuit for controlling the mechanism are not required, so that an economic effect can be obtained. .

  In the medium transport mechanism of the second embodiment, one roller of the pair of transport rollers arranged on the tractor side and the sheet guide holding the roller are pressed against the other roller side by a spring and pressed by the spring by the tension of the medium. This roller is separated from the other roller.

(Constitution)
The configuration of the medium transport mechanism of the second embodiment is mainly different in the configurations of the lower rear seat guide 14 and the spring 15 as shown in the top and bottom perspective views of FIGS. 9 and 10 and the configuration diagram of the spring of FIG. Since other configurations are the same as those of the first embodiment shown in FIG. 1, detailed description thereof is omitted for the sake of brevity.

  In the medium transport mechanism of the second embodiment, an opening is provided around the position of the lower rear roller 2b of the lower sheet guide 10, and a plurality of lower rear sheet guides 14 having a support shaft 14 'are provided in the opening, and the support shaft 14' is It is configured to be rotatably attached to a side frame of a medium transport mechanism (not shown).

  The lower rear roller 2b is rotatably attached to each lower rear sheet guide 14, and the lower rear roller 2b and the lower rear sheet guide 14 are configured to be pressed against the upper rear roller 2a side by a plurality of springs 15 with a pressing force Nr. Similar to the first embodiment, the conveying force Fr can be obtained by contacting the upper rear roller 2a and the lower rear roller 2b by the pressing force Nr.

  Here, as shown in the bottom view of FIG. 11, the spring 15 is divided into three parts, S1 part on both sides and S2 part on the center, and the rotating shaft of the lower rear roller 2b is pressed by the pressing force Nr1 by the S1 parts on both sides. The lower rear seat guide 14 is pressed with the pressing force Nr2 by the central S2 portion. Therefore, the spring 15 presses the lower rear roller 2b with Nr = Nr1 + Nr2.

  Note that the relationship between the conveying force Ff generated by the front roller pair 3 and the pressing force Nr of the spring 15 is the same as that in the first embodiment, and therefore the description thereof is omitted for the sake of brevity.

(Operation)
With the above configuration, the medium transport mechanism according to the second exemplary embodiment operates as follows. Hereafter, each operation | movement is demonstrated in detail using the operation | movement explanatory drawing of FIG.12 and FIG.12.

(In the case of cut paper)
First, when the cut sheet 12 is conveyed, as shown in FIG. 12, the cut sheet 12 inserted from the direction of the arrow B on the right side of the figure is held and conveyed by the pair of front rollers 3, and the print head 1 Printing is started by the platen 7. The cut sheet 12 that is conveyed to the rear roller pair 2 by the conveying force Ff of the front roller pair 3 while being guided by the lower rear sheet guide 14 and reaches the rear roller pair 2 is given the conveying force Fr by the spring 15. The pair 2 and the front roller pair 3 are conveyed by the conveyance force Ff, and the leading edge of the cut sheet 12 is discharged in the direction of arrow B ′ on the left side of the figure.

(For continuous paper)
When the continuous paper 13 is transported, the continuous paper 13 set on the tractor 6 is transported to the rear roller pair 2 by the transport force of the tractor 6 in the direction of arrow A and reaches the rear roller pair 2 as shown in FIG. Then, the leading edge of the sheet is caught in the rear roller pair 2 and conveyed to the position of the print head 1, printing is started by the print head and the platen 7, and conveyed to the front roller pair 3. The conveyance force of the continuous paper 13 during this period is conveyed by the conveyance force Fr applied to the lower rear roller 2b by the conveyance force Ft of the tractor 6 and the spring 11, that is, Ft + Fr.

  Then, the continuous paper 13 reaching the front roller pair 3 is caught by the front roller pair 3 and conveyed by the conveying force Ff. At this time, similarly to the first embodiment, the lower rear roller 2b is pushed down by the tension of the sheet generated by the sheet discharge end (contact c in FIG. 3) of the tractor 6 and the conveying force Ff of the front roller pair 3, and the lower rear sheet that holds this. The guide 14 rotates downward with the support shaft 14 ′ as a fulcrum, and is pushed down to the position shown in FIG. 13, that is, the position of the lower sheet guide 10.

  Then, since the rear roller pair 2 is in the separated state, its conveying force Fr becomes “0”, and the continuous paper 13 is conveyed by the conveying force Ft of the tractor 6 and the conveying force Ff of the front roller pair 3. During printing of each line, the driving of the tractor 6 and the front roller pair 3 is stopped, but the continuous paper 13 is fixed by the paper discharge end (contact c in FIG. 3) of the tractor 6 and the front roller pair 3 so that a constant tension is applied. As in the first embodiment, it is maintained and stably held at a position balanced with the pushing force of the spring 11 to the lower rear roller 2b.

  When the continuous paper 13 is removed and the trailing edge of the continuous paper 13 is removed from the tractor 6, the tension of the paper 13 becomes "0", the lower rear roller 2b and the lower rear sheet guide 14 are pushed up by the spring 15, and the conveying force Fr is obtained again. Therefore, the continuous paper 13 is transported by the transport force Ff + Fr and discharged in the direction of the arrow A ′ on the right side of the figure.

  As described above, the medium transport mechanism of the second embodiment can obtain a stable transport force in the same manner as in the first embodiment in the case of single sheet transport or in each transport state of continuous paper transport.

(Effect of Example 2)
According to the medium transport mechanism of the second embodiment described above, since the lower rear roller 2b is provided in the lower rear sheet guide 14, in addition to the effects of the first embodiment, the leading edge of the sheet hangs around the lower rear roller 2b, jams, etc. Stable paper conveyance is possible without occurrence.

<< Other modifications >>
In addition to the examples described above, the same functions and effects as those of the present invention can be obtained in the following modified embodiments. That is,

  (1) In the above description of the embodiment, the lower roller on the rear roller side is pressed together with the spring or the sheet guide. However, when the position of the tractor 6 is arranged on the upper side, the upper rear roller 2a is moved to the spring. In the case where the position of the tractor 6 is provided on the front side, one of the front rollers may be pressed by a spring.

  (2) In the above description of the embodiment, it has been described that the paper roller is pushed down together with the spring or the sheet guide by the tension of the paper and the conveying roller pair is separated, but for example, a medium detection sensor is provided around the front roller pair 3 and the front. It is also possible to detect that the paper is caught in the roller pair 3 and to separate the conveying roller pair by using a separate driving source or using the tension of the paper.

  (3) In the above description of the embodiment, the medium transport mechanism in which printing is performed by the print head 1 and the platen 7 has been described. However, recording such as electrophotographic or inkjet printing, magnetic recording, or magnetic reading is described. It goes without saying that the present invention can be applied even when performing the above.

  (4) In the above description of the embodiments, the springs 11 and 15 have been described as plate-like shapes as shown in FIGS. 1 and 11, but the shape may be arbitrary as long as a constant pressing force is generated. Moreover, although the attachment position of the springs 11 and 15 was demonstrated to attach to the lower sheet | seat guide 10, it may be a fixed position and you may make it attach to places, such as an apparatus frame.

  (5) In the above description of the embodiment, considering the fact that the sheet is conveyed obliquely, etc., a plurality of rear rollers 2b, springs 11, springs 15, and lower rear sheet guides 14 are provided, and each is described as an independent configuration. In order to prioritize the economic effect and reduce the number of parts, it may be arbitrarily integrated.

  As described above, the present invention can be widely used in medium handling apparatuses that use a medium of a certain length or a continuous medium, such as various printing apparatuses, a copying machine, and the like.

3 is a configuration diagram of a medium transport mechanism according to Embodiment 1. FIG. 3 is a perspective view of a medium transport mechanism according to Embodiment 1. FIG. FIG. 3 is an enlarged view of a rear roller portion according to the first embodiment. 6 is a diagram illustrating a relationship between a continuous paper conveyance force and a spring pressing force according to the first exemplary embodiment. FIG. FIG. 6 is an operation explanatory diagram of the medium transport mechanism according to the first embodiment. FIG. 6 is an operation explanatory diagram of the medium transport mechanism according to the first embodiment. FIG. 6 is an operation explanatory diagram of the medium transport mechanism according to the first embodiment. FIG. 6 is an operation explanatory diagram of the medium transport mechanism according to the first embodiment. 6 is a top perspective view of a medium transport mechanism according to Embodiment 2. FIG. 6 is a bottom perspective view of a medium transport mechanism according to Embodiment 2. FIG. FIG. 6 is a configuration diagram around a spring according to a second embodiment. FIG. 10 is an operation explanatory diagram of the medium transport mechanism according to the second embodiment. FIG. 10 is an operation explanatory diagram of the medium transport mechanism according to the second embodiment.

Explanation of symbols

1 Print Head 2a Upper Rear Roller 2b Lower Rear Roller 2 Rear Roller Pair 3a Upper Front Roller 3b Lower Front Roller 3 Front Roller Pair 6 Tractor 7 Platen 11, 15 Spring 12 Cut Sheet 13 Continuous Paper 14 Lower Rear Sheet Guide

Claims (5)

A first conveying means provided in the medium conveying path to drive and convey the medium;
A second rear roller configured to be provided on the downstream side of the medium conveying direction with respect to the first conveying unit on the medium conveying path and convey the medium; A third conveying unit that is provided on the downstream side in the medium conveying direction with respect to the conveying unit and the second conveying unit on the medium conveying path and drives the medium by a larger conveying amount than the first conveying unit. When,
A print head provided between the second conveying means and the third conveying means in the medium conveying path;
A platen provided to face the print head;
A spring for pressing the lower rear roller against the upper rear roller is disposed,
The conveyance path composed of the first conveyance means and the second conveyance means, and the conveyance path composed of the second conveyance means and the third conveyance means are bent, and the spring and the first The conveying means is provided below a conveying path composed of the second conveying means and the third conveying means,
The spring is pushed down by a tension acting on the medium when the medium is conveyed by the first conveying means and the third conveying means, and separates the upper rear roller and the lower rear roller. Printing device to do.   The printing apparatus according to claim 1, further comprising a guide portion to which the lower rear roller is rotatably attached.   The printing apparatus according to claim 1, wherein the first transport unit is a tractor.   The printing apparatus according to claim 1, wherein the third transport unit is a roller pair. The printing apparatus according to claim 1, wherein the medium is continuous paper.

Images