JPH0146415B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sheet clamping device for a printing device or a facsimile device, and specifically to a sheet clamping device for winding a sheet around a drum as a rotating body.

Various types of devices have already been proposed for winding and fixing sheets of paper, such as printing paper in printing machines, transmission originals and recording paper in facsimile machines, and paper-like photoreceptors in copying machines, around drums.
And some of them have been put into practical use.

As an example of the sheet clamp device described above, a printing device using an inkjet recording method will be described.

In FIG. 1, reference numeral 1 indicates a casing of the device, and inside this casing 1 there is a drum 2.
is rotatably supported by a support shaft 3. The drum 2 is provided with gripping claws 4, and a paper feeding device 5, a recording device 6, and a paper ejecting device 7 are arranged around the drum 2 in this order in the drum rotation direction.

The paper feeding device 5 consists of a loading table 8, a paper feeding roller 9, and a pair of delivery rollers 10. When the gripping claw 4 comes to the position shown by the broken line 4a, the paper feeding roller 9 and the delivery roller pair 10 are activated. The sheet begins to rotate, and is moved slightly faster than the circumferential speed of the drum 2, which rotates at approximately 30 rpm, and when it reaches the distant gripping claw, the sheet is moved through a suction hole drilled in the surface of the drum 2 by means not shown. At the same time, the gripping claws 4 grip the sheet. After the leading end of the sheet is brought into close contact with the drum surface over its entire length, the trailing end of the sheet is sucked by means not shown through a suction hole formed in the drum 2 surface.

The recording device 6 consists of an ink jet head 12 located close to the drum surface, a guide shaft 13, a drive shaft 14 consisting of a screw shaft, and a control device (not shown). The guide shaft 13 and the drive shaft 14 are both provided parallel to the support shaft 3 of the drum.
The ink jet head 12 is moved in the generatrix direction (sub-scanning direction) along the drum surface by a drive shaft 14 rotated by a drive motor 15. On the other hand, the drum 2 wrapped with the sheet is
In the figure, the inkjet head 12 rotates counterclockwise at approximately 1000 rpm, and the inkjet head 12 also relatively moves in the main scanning direction. The ink jet head 12 then jets minute ink droplets toward the drum surface (sheet surface) in response to a signal applied thereto to form a recorded image in dot matrix.

Note that the sheet wound around the drum 2 may be printed paper with nothing printed on it, or may be printed paper formed by printing a predetermined format in another format. good.

The paper discharge device 7 peels the printed sheet from the surface of the drum and discharges it.
It consists of a peeling roller 16 installed in such a way that it can come into contact with the drum surface, and a pair of discharge rollers 18 that send out the sheet peeled from the drum surface to a paper discharge table 17.

By the way, the sheet clamp device shown in the above-mentioned printing apparatus consists of a gripping claw that holds the leading edge of the sheet while sucking the leading edge and trailing edge of the sheet.
A separate peeling roller 16 is used to peel the sheet from the drum surface after printing is completed. According to this method, the peeling roller 16 must come into pressure contact with the drum surface at least after the sheet leading edge gripper 4 is released, which complicates the mechanism for ensuring accurate operation in a short time and causes the sheet to sag. Since this is a method in which the sheet is heated, there is a risk that the sheet may be contaminated or a jam may occur. Moreover, even though the sheet contamination is prevented, the mechanism becomes complicated and the cost increases. Other methods of sheet peeling include providing a sheet tip push-out claw that pushes out the back side of the sheet from inside the drum, or providing a mechanism that blows air to the sheet tip and removes the sheet from the claw. Both had complicated mechanisms, increased costs, and had problems with reliability.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and drawbacks, and to provide a sheet clamping device that has a simple configuration, does not contaminate the sheet, and can reliably separate the sheet from the drum surface.

These objects include a rotating body that can rotate at high and low speeds, a suction means provided on the rotating body that sucks flat sheets and settles the sheets when ejecting the sheets, and a suction means that holds the leading edge of the sheet in its mouth. A gripping claw is movably and swingably supported by a rotating body, and when the rotating body rotates at a low speed, the gripping claw is moved downstream in the rotational direction, and when the rotating body rotates at a high speed, the gripping claw is moved to the downstream side in the rotational direction. gripping pawl moving means for moving the sheet upstream in the rotational direction; when the rotary body rotates at a low speed, the leading edge of the sheet is released from the gripping pawl; when the rotary body rotates at a high speed, the sheet tip is released from the gripping pawl;
This is achieved by a sheet clamping device characterized in that it includes a gripper opening/closing means for causing the gripper to hold the leading edge of the sheet.

According to the present invention, when the rotary body shifts to low speed rotation during paper discharge after printing or recording, the gripping claw moving means moves the gripping claw downstream in the moving direction, and the gripping claw opening/closing means moves the gripping claw toward the leading edge of the sheet. Since the suction means also releases the sheet, the sheet can be peeled off from the drum surface without forming slack in the sheet that would contaminate the sheet. Moreover, since the configuration is extremely simple, there is no cost problem and reliability is improved.

The invention will now be explained in detail with reference to the illustrated embodiments. In FIG. 2, there are a plurality of suction holes 2 on the circumferential surface of the drum 2 along the generatrix (in a direction perpendicular to the plane of the paper).
0 is bored, and the leading end of the sheet S is suctioned by a known suction means that reaches a negative pressure generating position via a suction pipe 21. Generally, the leading edge position of the sheet S is determined by synchronizing the rotation of the pair of registration rollers 10 (see FIG. 1) with the rotational position of the drum 2. ) at a predetermined position on the downstream side,
A stopper 22 is arranged. stopper 2
2 is movable in and out of the drum surface and is biased in the direction of protrusion. As shown in the figure, the stopper 22 protrudes when the gripper is open, and when the gripper is closed, the stopper 22 easily sinks into the drum.

The gripper claw 4 has a plurality of pairs of claw portions 4a and base portions 4b substantially integrally formed on a common base shaft 4c, and has one of a plurality of holes 20 bored in the circumferential surface of the drum 2 along the generatrix. A pair of claw portions 4a and base portions 4b are arranged in correspondence with each other.

Flanges 23 are attached to both ends of the drum 2.
The flange 23 has elongated holes 24 formed at positions facing each other.
The elongated hole 24 serves as a guide means that constitutes a gripping claw opening/closing means together with a gripping claw moving means to be described later.
The end portion of the base shaft 4c of the gripper claw 4 is loosely fitted, and the gripper claw 4 is oriented obliquely toward the center of the drum as it advances in the rotation direction A.

The length position of the elongated hole 24 is defined as the tip of the sheet where the claw portion 4a is attracted to the suction hole 20 when the base shaft 4a contacts the elongated hole end 24a on the flow side (right side in the figure) in the drum rotation direction. This is the position where the base shaft 4c can be sufficiently pressed down, and conversely, when the base shaft 4c comes into contact with the elongated hole end 24b on the downstream side (left side in the figure) in the drum rotation direction,
The free end of the claw portion 4a is set at a position where the leading edge of the sheet can be sufficiently opened.

The gripping claw moving means 25 is. Mainly lever 2
6. It consists of a plumb weight 27 and a spring 28. One end of the lever 26 is fixed to the end of the base shaft 4c, and the other end is fixed to a weight 27 having an appropriate weight. The base shaft 4c moves into the elongated hole 24,
In addition, the vertical plumb 27 is arranged so that the claw portion 4a swings about the base shaft 4c and does not interfere with the action of opening and closing the seat.
can move within a hole 29 formed in the drum flange 23. spring 28
has both ends locked at appropriate locations on the lever 26 and the flange 23, and the base shaft 4c is connected to the flat elongated hole end 2.
It is biased in a direction to bring it into contact with 4b. The strength of the spring 28 is such that, for example, in the position shown in FIG.
At a high speed of 1000 rpm, the centrifugal force acting on the weight 27 cannot be resisted, and the base shaft 4c is brought into contact with the long hole end 24a on the opposite side, and the lever is moved clockwise (in the figure) with the base shaft 4c as the center. The strength is set so that the claw portion 4a can reliably grip the leading edge of the sheet by swinging it in the direction of arrow B).

With the above configuration, during low speed rotation, the elongated hole 24 retreats to the lower left 24b in the figure due to the action of the spring 28, and further swings counterclockwise around the base shaft 4c, and the claw portion 4a is opened. become a state. Therefore, in this state, the leading end of the sheet is exposed from the gripping claws 4. Therefore, when discharging a sheet, if only the suction of the suction hole 20 is released, the sheet is smoothly peeled off and discharged by the stiffness of the sheet and its own weight. There is no need to shift the leading edge of the sheet or push out the sheet from inside the drum.

When the drum shifts to high-speed rotation, first, the centrifugal force of the entire gripping claw moving means 25 overcomes the force of the spring 28, and the base shaft 4c moves to the upper right side of the long hole 24a, and then rotates clockwise around the base shaft 4c. This will force the tip of the sheet to press down. It is important to appropriately select the ratio between the centrifugal force of the entire gripper moving means and the centrifugal force of the weight so that the order of movement is not reversed.

Another embodiment of the invention is shown in FIG. This embodiment is a suitable example when the above-mentioned ratio cannot be properly obtained due to structural reasons. That is, when the end of the lever 26A to which the weight 27 is fixed is extended and the gripper claw 4 is in the open state, the lever stopper 30 is moved to the flange 23 (FIG. 2) so as to come into contact with the extended part 26Aa. It is located in The contact surface D of this lever stopper 30 is parallel to the direction C of the elongated hole 24.

Therefore, the rotational speed of the drum 2 changes from low speed to high speed, and first, the base shaft 4c moves to the upper right side 24a of the long hole under the guidance of the long hole 24 and lever stopper 30. During this time, the weight side end (extension 26Aa) of the lever 26a is in contact with the lever stopper 30, so it cannot swing. As you move further, when the gripping claw reaches the position where it grips the leading edge of the sheet,
Since the extension 26Aa separates from the lever stopper 30, the lever 26A swings.

In this way, the order of movement and rocking of the gripping claw moving means is never reversed. The effect in this case is exactly the same as in the previous embodiment.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of the configuration of an inkjet recording device as an example of the device to which the present invention is applied, and FIG.
The figure is a partially cutaway partial view showing one embodiment of the invention, and FIG. 3 is a partially schematic configuration diagram showing another embodiment of the invention. 2... Drum, 4... Grip claw, 4c... Base shaft, 20... Suction hole, 24... Long hole, 25... Grip claw moving means, 26... Lever, 27... Weight, 28... spring.

Claims (1)

[Claims] 1. A rotating body capable of rotating at high and low speeds; a suction means provided on the rotating body to suck a flat sheet and release the sheet when ejecting the sheet; and a suction means provided on the rotating body to grip the leading edge of the sheet. When the movably and swingably supported gripping claw and the rotating body rotate at a low speed, the gripping claw is moved downstream in the rotational direction, and when the rotating body rotates at a high speed,
a gripping claw moving means for moving the gripping claw upstream in the rotational direction; A gripper opening/closing means is provided for causing the gripper to grip the leading edge of the sheet, and when the rotating body rotates at low speed, the gripping grip moves downstream in the rotational direction, and then releases the leading edge of the sheet, and when rotating at high speed, the gripping gripr moves in the rotational direction. A sheet clamp device that grips the leading edge of the sheet after moving upstream.