JPS61132365A - Back-tensioning device for rolled form sheet - Google Patents

Abstract

PURPOSE:To prevent an ink sheet from sagging, by providing a roller pressed against an outer peripheral surface of a holder through a shaft body and a means for restricting rotation of the roller when a torsion spring is twisted to a predetermined extent. CONSTITUTION:When a transferring action is performed after an upper frame 1 is closed, the shaft body 17 comes into contact with a stopper 22 on being oscillated by a predetermined amount, and is prevented from coming closer to the protective plate 14, whereby the pressing force of the roller 16 against the outer peripheral surface of the protective plate 14 is weakened, and a restoring force of the torsion spring 21 exerted on the holder 6 is restricted. Thus, during the transferring action, the resisting force exerted on the holder 6 is adjusted, and the sheet 4 is back-tensioned to such an extent as not to obstruct a paying-out operation. Even after the transferring action is finished and payout of the sheet 4 is topped, the spring 21 remains twisted to a certain extent, and the roller 16 remains pressed against the outer peripheral surface of the protective plate 14, so that the sheet 4 is maintained in the state of being back- tensioned. Accordingly, the sheet 4 is securely prevented from sagging, even in a stand-by state.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is applicable to various image forming applications such as thermal printers using rolled thermal sheets, facsimile machines using rolled thermal paper, and copying machines using rolled copying paper. The present invention relates to an improvement in a device for applying pack tension to the roll sheet.

(Prior Art) Conventionally, as shown in Japanese Unexamined Patent Publication No. 58-53454, in the above-mentioned image forming apparatus, a braking member is brought into pressure contact with the outer periphery of a rotating flange of a holder holding a rolled sheet. Accordingly, an apparatus is known that applies pack tension when feeding a rolled sheet. However, with such devices, pack tension is only applied during sheet feeding operation, so
In the Samurai, when the L sheet or holder is moved, for example, when removing a jam (paper jam) or inspecting, there remains a risk that the sheet may become loose, causing wrinkles.

(Objective of the Invention) In view of the above circumstances, the present invention is capable of applying pack tension not only during the feeding operation of a rolled sheet, but also during the waiting period, thereby preventing slack in the ink sheet. To provide a pack tension applying device that can reliably prevent the occurrence of pack tension and can also adjust the pack tension so that it does not become excessively large during sheet feeding.

(Structure of the Invention) The present invention provides an image forming apparatus in which a holder for holding a rolled sheet is rotatably attached to a machine body, in which a roller for applying pack tension is rotatably attached to the machine body via a shaft body, and a torsion spring that is installed so as to be in pressure contact with the outer peripheral surface of the holder, and that twists when the roller rotates to apply a restoring force in a direction opposite to the rotational direction of the roller;
A suppressing means is provided for suppressing the restoring force transmitted from the torsion spring to the holder via the roller when the roller rotates until the torsion spring is twisted by a predetermined amount.

(Embodiment) FIG. 1 shows a schematic structure of a thermal printer as an example of an image forming apparatus equipped with a back tension applying device of the present invention. In the embodiment shown in this figure, the body of the thermal printer is divided into an upper frame 1 and a lower frame 2,
Both frames 1.2 are connected via a pivot 3 at the rear end, so that they can be opened and opened about the pivot. A holder 6 for holding a roll 5 of an ink sheet 4 as a rolled sheet is rotatably attached to the lower frame 2 near the pivot 3. A removing device 7 is provided, and a thermal head 8 and a separating roller 9 are arranged between these devices. On the other hand, inside the upper frame 1, the holder 6 is
(Nermal Head 8)
A guide mechanism 10 consisting of a roller or the like, and a platen roller 11 facing the multi-head 8 are provided, and a paper feed cassette 12 and a paper discharge tray 13 are provided above the guide mechanism 10.

The holder 6 is equipped with a pair of left and right protection plates 14, and a boss part protruding from the center of the inner surface of each protection plate 14 is fitted into both ends of the paper tube of the ink sheet roll 5, so that the ink sheet can be The roll 5 is held between protective plates 14 from both sides.

A rotary shaft 15 protruding outward from the protection plate 14 is supported by the lower frame 2.

Further, on the upper frame 1, there are rollers 16 for applying pack tension which are positioned above each protection plate 14 of the holder 6, and rollers 16 which are disposed parallel to the rotation stroke 15 of the boulder 6. A shaft 17 that is rotatably held at an eccentric position, an elongated hole 18 that supports this shaft 17 so as to be swingable within a predetermined range, and a shaft 17 that swings V! A tension spring 20 that urges one end of the enclosure and a screw spring 21 that provides restoring force when the roller 16 rotates are provided.On the other hand, the lower frame 2 is provided with the upper frame 1. A stopper 22 is provided which limits the swinging range of the shaft 17 by υ1 when the shaft body 17 is engaged. These components constitute a back tension applying device.

Specifically, this back tension applying device is shown in FIGS. 2 to 5. In other words, the elongated holes 18 are formed in the both side plates of the upper frame 1 in the front-rear direction, and both ends of the shaft body 17 are inserted into the elongated holes 18 in a state in which they are prevented from rotating. The shaft body 17 is swingable within. The rollers 16 are located near both ends of the shaft 17, and the centers 01, 0 of the roller 16 and the shaft 17 are
2 is rotatably mounted eccentrically.

The roller 16 has an outer periphery made of rubber or the like.
II It is made of a material with low resistance and high resistance. Further, the tension spring 20 is attached between one bottle protruding from the side plate of the upper frame 1 and the shaft body 17.
The shaft body 17 is urged toward the front end side of the elongated hole 18 by this. When the upper frame 1 is closed, the C roller 16 contacts the outer periphery of the protective plate 14 of the holder 6 during closing, and as the upper frame 1 is further closed, the shaft 17 is guided into the elongated hole 18. By shifting toward the rear end,
The formation direction and formation range of the elongated hole 18 are determined so that the roller 16 moves in the ink sheet rewinding direction while coming into pressure contact with the outer periphery of the protection plate 14.

In addition, as a member that urges the roller 16 in a certain direction,
- Note: Instead of the tension spring 20, a compression spring, an air cushion cylinder, etc. that presses the roller 16 from the opposite direction may be used. Instead of a hole, a groove, frame, etc. may be used.

Further, the torsion spring 21 is formed of a coil spring, is arranged on the outer periphery of the shaft body 17, and has one end fixed to the shaft body 17 and the other end fixed to the roller 16, respectively. When the upper frame 1 is closed, the rotation of the roller 16 is controlled by the screw spring 21 so that a portion of the outer periphery of the roller 16 having a large distance from the shaft body 17 comes into contact with the outer periphery of the protection plate 14.
regulated by.

Further, the stopper 22 is provided to protrude upward from both side plates of the lower frame 2, and when the upper frame 1 is closed to the lower frame 2, the stopper 22 is located on the side of the elongated hole 18. It is arranged to face the shaft body 17 front and rear. As described above, when the shaft 17 swings as the roller 16 held at an eccentric position by the shaft 17 rotates during sheet feeding, the shaft 17 is moved at a minimum distance from the holder 6. Before approaching the shaft body 17, the stopper 22
The position of the stopper 22 is set so as to abut the shaft body 17 and prevent the shaft body 17 from approaching the holder 6 any further. In this way, a suppressing means for appropriately suppressing the restoring force acting on the holder 6 from the torsion spring 21 via the roller 16 is constructed.

The operation of this pack tension applying device will be explained next.

According to the structure shown in the figure, when the upper frame 1 is open, the rollers 16 are separated from the holder 6, but when the upper frame 1 is closed, the rollers 16 are moved away from the protective plate 1 of the holder 6.
Press against the outer circumferential surface of the In this case, as mentioned above, the elongated hole 18
If the tension spring 20 is provided, the ink sheet 4 can be automatically tensioned at this time. That is, during the closing movement of the upper frame 1, the roller 16 for applying pack tension contacts the outer periphery of the protective plate 14 of the holder 6 during the closing movement, and then this roller 16 moves along the outer periphery of the protective plate 14. As shown by arrow A in FIG. 4, the ink sheet is moved in the unwinding direction (clockwise in this figure). At this time, the roller 16 is pressed against the outer peripheral surface of the protection plate 14 by the tension spring 20, and the roller 16 and the protection plate 14 are pressed against each other.
When the roller 16 tries to rotate in the direction of arrow B, a restoring force is applied from the screw spring 21, so that the holder 6 moves in the direction of arrow C, that is, in the direction in which the ink sheet 4 is rewound. Rotate.

Therefore, the ink sheet 4 is pulled and slack is removed.

When the transfer operation is performed after the upper frame 1 is closed, as shown in FIG. 5, as the ink sheet 4 is fed out and the holder 6 rotates in the direction of the arrow (counterclockwise in this figure), The first coke 16 rotates in the direction of arrow B (clockwise), and the restoring force of the screw spring 21 corresponding to the amount of rotation acts on the holder 6 as a resistance force via the roller 16.

The roller 16 is held at an eccentric position by the shaft body 17, and initially the portion that is far away from the shaft body 17 is in pressure contact with the protection plate 14, so that the roller 16 is held on the protection plate 14.
As the shaft body 17 rotates while being in pressure contact with the boulder 6, the shaft body 17 gradually swings in a direction approaching the boulder 6, but when it swings a predetermined M, it comes into contact with the stopper 22, and the shaft body 1
7 is prevented from approaching the protection plate 14. Therefore,
When the roller 16 rotates to this state, the pressing force of the a-roller 16 against the outer peripheral surface of the protection plate 14 is weakened,
When the holder 6 continues to rotate, the roller 16 slips and does not rotate any further, and the restoring force of the screw spring 21 acting on the holder 6 is suppressed. In this way, during the transfer operation, the resistance force exerted by the roller 16 on the ink sheet 1 to the holder 6 rotating in the feeding direction is adjusted appropriately, and pack tension is applied to an extent that does not interfere with the feeding operation of the ink sheet 4. It will be done. Roughly speaking, even when the feeding of the ink sheet 4 is stopped after the transfer operation is completed, the torsion spring 21 is twisted to some extent and the roller 16 is in pressure contact with the outer peripheral surface of the protection plate 14. Due to the restoring force, the state in which pack tension is applied to the ink sheet 4 is maintained. Therefore, it is possible to reliably prevent the ink sheet 4 from becoming loose even during standby.

Note that the apparatus of the present invention is applicable not only to the thermal printer of the above embodiment, but also to various types of rolled thermal paper, such as facsimile machines that record by directly applying heat pulses to rolled thermal paper, and copying machines that use rolled copying paper. It is applicable to image forming apparatuses that use sheets.

Further, in addition to the structure shown in the above embodiment, as a suppressing means for suppressing the restoring force of the torsion spring 21 acting on the holder 6 from becoming excessive during sheet feeding in the apparatus of the present invention, for example, the outer circumference of the roller 16 may be used. A structure in which a part of the surface is formed of a material with low frictional resistance so that the roller 16 slips when this part comes into contact with the holder 6, or a movable structure that rotates when a certain amount of rotational force is applied. There is also a structure in which a member is provided on the shaft body 17 side and a screw spring 21 is attached between this movable member and the roller 16, so that when the amount of twist becomes large, the torsion spring 21 rotates together with the roller 16. Can be adopted.

In addition, in the above embodiment, the upper and lower frames 1 that can open and close the aircraft are
．． 2, and a roller 16 according to the opening and closing of the upper frame 1.
Although the roller 16 can be separated from and pressed against the holder 6, the machine body may have an integral structure, and the roller 16 is arranged so as to be pressed against the outer periphery of the holder 6 at least during sheet feeding and standby. That's fine.

(Effects of the Invention) As explained above, in the present invention, as the holder rotates when a rolled sheet is fed out, the roller for applying pack tension that comes into pressure contact with the holder rotates, and the restoring force of the torsion spring is accordingly applied to the holder. In addition, when the holder rotates and VcG exceeds VcG, the restoring force is kept at hjL so that the restoring force does not become excessive. It can give tension. In addition, even if the sheet feeding operation is stopped after the rollers have rotated, the restoring force of the torsion spring remains and pack tension is applied to the sheet, so it is possible to reliably prevent the sheet from loosening even during standby. It is.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of a thermal transfer recording machine equipped with the device of the present invention, FIG. 2 is a perspective view of the main parts, FIG. 3 is an enlarged cross-sectional plan view of the part constituting the pack tension applying device, FIG. FIG. 5 is a side view of the main parts showing the state when the upper frame is closed and during transfer. 1.2... Airframe (upper frame and lower frame), 3
... Pivot, 4... Ink sheet, 5... Ink sheet roll, 6... Holder, 16... Roller for applying pack tension, 17... Shaft, 18... Oblong hole , 21...Torsion spring, 22...Stopper.

Claims (1)

[Scope of Claims] 1. An image forming apparatus in which a holder for holding a rolled sheet is rotatably attached to a machine body, and a roller for applying back tension is rotatably attached to the machine body via a shaft, and the holder is rotatably attached to the machine body. A torsion spring is installed so as to be in pressure contact with the outer peripheral surface of the roller, and is twisted when the roller rotates to apply a restoring force in a direction opposite to the direction of rotation of the roller. 1. A device for applying back tension to a rolled sheet, comprising: a suppressing means for suppressing the restoring force caused by the torsion spring when the roller rotates to a state where the torsion spring is twisted by a predetermined amount. 2. The suppressing means includes holding the roller at an eccentric position on the shaft, attaching the shaft to the aircraft body in a swingable manner, and urging the shaft toward the holder using a biasing member. When the roller rotates while being in pressure contact with the outer peripheral surface of the holder, the shaft body swings accordingly, and when the shaft body swings, the shaft body approaches the minimum distance from the holder. 2. The device for applying back tension to a rolled sheet according to claim 1, further comprising a stopper that comes into contact with the shaft and prevents the shaft from approaching the holder.