JPS6348780B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sheet clamp device for winding and fixing a sheet-shaped body around a drum.

As a device for winding a sheet material onto a drum,
For example, there are master sheet mounting devices in offset printing machines, transmission document and recording paper mounting devices in facsimile machines, and sheet-like photoreceptor mounting devices in copying machines, and various types of these have already been proposed and put into practical use. has been done.

All of the conventional seat clamp systems are so-called mechanical systems that involve complex combinations of cams, levers, and the like. Therefore, the mechanism becomes very complicated, and the parts constituting the mechanism are required to have high precision, resulting in a disadvantage that the cost is inevitably high. In addition to the above-mentioned problem of high costs, the large number of parts also complicates the operation of the mechanism, making it more likely to cause clamping errors, sheets to come off the drum, and sheet jams due to this. However, there were some drawbacks that made it difficult to call this a highly reliable seat clamp device.

The present invention has been made in view of the above, and includes:
By minimizing the number of parts that require mechanical operation, in other words, by minimizing the number of component parts, the above-mentioned drawbacks are eliminated, and the structure is simple and inexpensive, and the seat is highly reliable. The purpose is to provide a clamping device.

The object of the present invention is to provide a sheet clamping device that clamps a sheet to a drum by pressing the sheet edge against the drum surface using sheet gripping claws provided parallel to the axis of the drum. a sheet gripping claw that has an opening habit of and a suction means connected to the suction hole, and the suction means sucks air from the suction hole to attract both the sheet gripping claw and the sheet to the drum surface. This is achieved by a sheet clamping device.

According to the present invention, the mechanical mechanism for opening and closing the sheet gripping pawl, which requires the most delicate and reliable operation in a sheet clamping device, is eliminated, and the opening and closing operations of the sheet gripping pawl are performed by an air suction method. Therefore, it is possible to provide a device with a small number of parts, in other words, a seat clamp device with a simple structure, low cost, and high reliability of the seat clamp.

In other words, the feature of the present invention is that air is sucked from inside the drum to attract and adhere the sheet to the drum surface, and the sheet gripper is also sucked with air to close the gripper and press the edge of the sheet. That's what I did.

Hereinafter, the present invention will be explained in detail with reference to illustrated embodiments. Before proceeding with the explanation, the term "sheet" used in the following explanation refers to a sheet-like material such as a master sheet in an offset printing machine, a transmission original or recording paper in a facsimile machine, and a sheet-like photoreceptor in a copying machine. It also includes.

First, a printing apparatus using an inkjet recording method will be described as an example of a type of apparatus that winds and fixes a sheet around a drum.

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 sheet gripping claws 4, which will be described in detail later. 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 accordance with the rotation system of the drum.

The paper feeding device 5 is a well-known suction cup type automatic paper feeding device, and is composed of a suction cup 8, a feed roller 9, an idle roll 10, and a sheet mounting table 11. The suction cup 8 has a home position indicated by a chain line 8A, and when feeding paper, moves from the chain line position to the solid line position, sucks the sheet S at the solid line position, and then returns to the chain line position again. Suction cup 8
The mechanism and suction means for causing the above operation to be performed are not shown. When the suction cup 8 attracts the sheet S and returns to the position indicated by the chain line, the idle roller 10 is separated from the feed roller 9 to a position not shown, and after the suction cup 8 comes to the position indicated by the chain line, the idle roller 10 is moved to the position shown in the figure at an appropriate timing. The sheet S is returned to the position shown in FIG. When the feed roller 9 rotates in synchronization with the position of the sheet gripping claw 4 of the drum 2 which is rotating at a relatively low speed, the sheet S is fed toward the drum 2.
Its tip is inserted between the open sheet gripping claw 4 and the surface of the drum 2. Thereafter, the sheet gripping claws 4 are closed by means not shown, and the clamping of the leading end of the sheet is completed. The sheet whose leading end is clamped is brought into close contact with the drum surface over its entire length, and then its trailing end is clamped by a trailing end clamping means (not shown).

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 inkjet head 12 is driven by a drive motor 1.
The drum is moved along the surface of the drum in the generatrix direction (sub-scanning direction) by a drive shaft 14 rotated by the drive shaft 5 . On the other hand, the drum 2 wrapped with the sheet
Since the inkjet head 12 rotates in the direction of the arrow, 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) in response to a signal applied thereto to form a recorded image in the form of a dot matrix.

Note that the sheet clamped to the drum 2 may be ordinary recording paper (printed paper) without any printing or writing, or may be a sheet made by printing a predetermined format in another format. The recording paper (printing paper) may also be used.

The paper ejecting device 7 peels the printed sheet from the drum surface and ejects it, and includes a peeling roller 16 installed on the drum 2 so as to be able to freely peel the sheet, and a sheet ejecting table 17 for removing the sheet peeled from the drum surface. It consists of a pair of discharge rollers 18 for sending out the paper to.

Now, a device for clamping a sheet onto the drum 2 as described above will be described with reference to an embodiment.

In FIGS. 2 to 7, a cylindrical drum 2
0 has a pair of flanges 21, 21 fitted and fixed to both ends thereof. A groove 22 is formed on the circumferential surface of the drum 20 in the generatrix direction. In this groove 22, there is a central portion 2 of the support body 24 of the sheet gripping claw 23.
4a has entered (see Figures 13 and 14).

The sheet gripping pawl 23 is made of a thin elastic plate such as a leaf spring, and is curved in the width direction to be approximately the same as the circumference of the drum 20. On one side of the sheet gripping claw 23, there is a stopper 25 formed by bending inward and against which the leading edge of the sheet collides.
is provided, and the other side edge is attached to the support body 24 with a screw 26.
Fixed by

On the other hand, in the drum 20, notches 27, 27 are formed at both ends of the groove 22, and the support body 2
Both ends 24b of No. 4 have entered (the sixth
12 to 14). Both ends 24b, 24b of the support body 24 are fixed by screws 29 to one end of a pivot shaft 28 rotatably mounted on the flange 21. Flange 21 of pivot 28
One end of a lever 30 (only one of which is shown in FIG. 2) is fixed to the externally projecting end of the lever.

One end of a spring 31 is locked to the free end of the lever 30, giving the sheet gripping pawl 23 a tendency to open. Spring 3
The other end of 1 is a short shaft 32 fixed to the flange 21.
It is locked to. The spring 31 is a relatively weak spring, and has the strength necessary to open the sheet gripping claw 23, as shown in FIG. The opening angle of the sheet gripping pawl 23 is regulated by one side edge of the lever 30 coming into contact with a stopper 33, as shown in FIG.

Further, the flange 21 is provided with a long hole 34, as only one of which is shown in FIGS. 2 and 3. The free end of the lever 30 has the long hole 34
A weight 35 is fixedly inserted through the inside of the drum. This weight 35 is connected to the drum 2 which will be described later.
When the drum rotates at high speed, it moves away from the center of the drum due to centrifugal force, and urges the sheet gripping pawl 23 in a direction to close it.

The drum 20 has an air suction hole 36, a stopper entry hole 37, and a suction pipe attachment hole 38 arranged in a row along the groove 22 in the portion held by the sheet gripping claw 23, which pass through the inside and outside of the drum. There is. As clearly shown in FIG. 6, these holes are provided in positions covered by the sheet gripping claws 23, and one of them, the stopper entry hole 37, has the stopper 25 of the sheet gripping claw 23 inserted therein. .

Inside the drum 20, along the row of holes,
A suction pipe 39 is provided (see FIG. 7).
This suction pipe 39 is fixed to a pipe holder 40. As shown in FIGS. 7 and 14, this pipe holder 40 is attached to the drum 20 by a screw 41 inserted into the suction pipe attachment hole 38.
is fixed to the inner peripheral surface of the Therefore, the suction pipe attachment hole 38 is closed with the screw 41. Further, the stopper entrance hole 37 is closed by a pipe holder 40 (see FIG. 13).

On the other hand, the air suction hole 36 is
As shown in FIG. 2, the pipe holder 40 and the suction pipe 39 are connected to the suction pipe 39 through communication holes 40a and 39a provided in the suction pipe 39, respectively.

One end 39b of the suction pipe 39 is connected to an air passage 42 formed in the flange 21, as shown in FIGS. 5 and 7, and the other end 39c is closed with a plug 43 as shown in FIG. has been done. In addition, in FIG. 5, the direction of the flange is changed for convenience of illustration.

The air passage 42 includes a groove 44 provided in the flange 21 and a rubber gasket 45 that closes the groove 44.
and a pressing plate 46. Holes 45a and 46a into which one end 39b of the suction pipe 39 fits are formed in the rubber packing 45 and the pressing plate 46, and these fitting portions are covered with a sheet member 47. The rubber packing 45 and the pressing plate 46 are fixed to the flange 21 with mounting screws 48. Note that in FIG. 5, holes 45b and 46b are provided in the rubber packing 45 and the press plate 46, respectively, but an embodiment in which the center of rotation of the flange is hollow to form an air passage as shown in FIG. In this case, it is assumed that the holes 45b and 46b are not formed.

As only one side of the flange 21 is shown in FIG. 7, a tube shaft portion 49 is formed on the flange 21, and a seal type bearing 50 is fitted into the shaft end. The bearing 50 is a bearing holder 50
A is fixedly supported by a stationary member 51 of the printing press body.

Therefore, the drum 20 is rotatably supported by the tube shaft portion 49 of the flange 21. This drum 20 is rotationally driven via a gear (not shown) fixed to the tube shaft portion 49.

What has been described above is a mechanism for clamping the leading end of the sheet (the operation will be described later), but in the illustrated embodiment, the trailing end of the sheet is also clamped by air suction.

As shown in FIG. 4, the drum 20 is provided with an air suction hole 52 for sucking the rear end of the sheet on the advancing side of the sheet leading edge clamping mechanism in the rotational direction. This suction hole 52 communicates with a suction pipe 53 arranged similarly to the suction pipe 39. This suction pipe 53 is connected to the air passage of the other flange 21.

As shown in FIGS. 2 and 19, one end of a vacuum hose 54 is connected to a bearing 50 that communicates with a suction hole 36 that suctions the leading end of the sheet, and a suction hole that suctions the rear end of the sheet. 5
One end of a vacuum hose 56 is connected to a bearing 55 (shown only in FIG. 19) that communicates with the vacuum hose 56.

The other ends of the vacuum hoses 54 and 56 are connected to the vacuum pump P, and each hose is provided with electromagnetic valves 57 and 58 for opening and closing air passages.

Further, near the drum 20, a sheet handling device 59 as shown in FIG. 23 is arranged.
The sheet handling device 59 includes a pivot shaft 60 rotatably supported on a stationary member (not shown), a pair of handling roller support arms 62 and 63 attached to the pivot shaft 60 via a leaf spring 61, and the support arms. 6
The drum 2 is rotatably supported by the drum 2 and 63.
0, a lever 65 whose base end is fixed to the pivot shaft 60, and this lever 65.
A spring 66 has one end engaged with the free end of the lever 65 and moves the handling roller 64 to the separated position as shown in FIG.
and a solenoid 68 connected via a solenoid 7.

As shown in FIG. 24, the handling roller 64 is normally provided with a spring 6 at a position away from the surface of the drum 20.
6, and when the solenoid 68 is energized during sheet clamping, which will be described later, it comes into pressure contact with the drum surface, as shown in FIG.

Now, the sheet clamping action of the device configured as above will be explained based on FIGS. 20 to 22.

For example, the drum 20 is 30 rpm when clamping the sheet.
It rotates at a low speed. Further, until the leading edge of the sheet is not fed between the sheet gripping claw 23 and the drum 20, both the electromagnetic valves 27 and 58 are closed. The sheet gripping claw 23 is connected to the suction hole 3
Since air suction from No. 6 is not done, No. 11
As shown in the figure, the stopper 25 is swung open by the action of the spring 31, and even in this state, a portion of the stopper 25 enters the stopper entry hole 37.

With the sheet gripping claw 23 open, the drum 2
0 rotates to the position shown in FIG. 20, the sheet feed roller pair 69 (first
The rollers (corresponding to rollers 9 and 10 in the figure) rotate and send out the sheet S that was being held between them toward the surface of the drum 20. Sheet feed roller pair 6
The sheet feeding speed by 9 is set slightly larger than the rotational speed of the drum 20, and the sheet feeding speed by the sheet S
The leading edge Sa is the stopper 2 of the sheet gripping claw 23.
5 (see Figure 6).

The sheet feeding action by the pair of sheet feeding rollers 69 will be explained. The pair of rollers 69 is provided with a clutch (not shown), and the action of this clutch causes the pair of rollers 69 to start rotating in synchronization with the position of the drum's claws. The clutch is connected and the roller pair 69 continues to feed the sheet until the leading edge of the sheet is gripped by the claws and suctioned, and the leading edge of the sheet reaches the next handling roller. Therefore, the drum linear speed and the roller pair 6 are required for the sheet whose tip is abutted against the claw.
The deflection is formed by the difference in linear velocity of 9.
Then, when the sheet gripping claw 23, in other words the leading edge of the sheet, reaches below the handling roller 64, the clutch is turned off and the driving force transmission to the roller pair 69 is cut off, and the roller pair 69 is no longer driven. After this, the roller pair 69 has its leading end clamped to the drum, and is pressed against the drum by a handling roller and rotated along with the advancing sheet.

Then, when the electromagnetic valve 57 (see FIG. 19) is operated at an appropriate timing after the sheet feed roller pair 69 starts rotating, the vacuum hose 52, the bearing 50, the tube shaft 49,
20 from the suction hole 36 via the air passage 42 and the suction pipe 39 (see FIG. 7).
Air is sucked in as shown.

By air suction from the suction hole 36, the sheet S (see FIG. 6), which is positioned so as to close approximately half of the opening of the hole 36, is first attracted to the hole 36, and then the sheet gripping claw 23 is attracted to the remaining opening of the suction hole 36. The sheet gripping pawl 23 is given the habit of opening in the opening direction by the spring 31 (see FIG. 11), but as mentioned above, this spring 31 is weak, and the sheet gripping pawl 23 is forced into the suction hole 36. It is easily adsorbed to the drum surface by air suction from the drum.

On the other hand, when the sheet is clamped, the handling roller 64 is in pressure contact with the surface of the drum 20, as shown by the solid line in FIG. Press. Then, as shown in FIG. 21, a drum 2 clamps the leading edge of the sheet S.
When the drum 0 rotates, the handling roller 64 presses and handles the sheet S to bring it into close contact with the drum surface. Then, as shown in FIG. 22, when the rear end Sb of the sheet S closes the suction hole 52 for the rear end clamp, the electromagnetic valve 58 (see FIG. 19) acts to remove air from the suction hole 52. Use suction to absorb the trailing edge of the sheet. Now the sheet is
The leading end is clamped by the suction hole 36 and the sheet gripping claw 23, and the rear end is clamped by the suction hole 52. In this case, the sheet S is tightly wound around the surface of the drum 20 while being handled by the handling roller 64.

After clamping the sheet, the drum 20 rotates at a high speed, for example, 1000 rpm, and the recording device 6 (see FIG. 1) prints on the sheet wound around the drum 20.

When the printing operation is finished and the drum rotates at a low speed again, and the end clamp section of the drum comes to the paper discharge device 7 (see Fig. 1), the electromagnetic valve 57 (see Fig. 19) is turned on. It is activated to stop air suction from the suction hole 36. As air suction from the suction hole 36 stops, the sheet gripping claw 23 swings due to the elasticity of the spring 31 (see FIG. 11).
The action of pressing the tip of the sheet can be released. At approximately the same time, the peeling roller 16 (first
(see figure) comes into pressure contact with the sheet on the drum 20, momentarily pulls out the sheet from the sheet gripping claw 23, and directs the sheet toward the pair of paper discharge rollers 18. Thereafter, the peeling roller 16 rotates to follow the rotating drum 20 through the sheet.

Further, it is not necessary to release the trailing end clamp of the sheet if the leading edge of the sheet is clamped by the paper ejecting roller pair 18, but preferably when the trailing end clamping portion of the drum 20 reaches the paper ejecting device portion. , the electromagnetic valve 58 is operated to stop air suction from the suction hole 52. This prevents the rear end of the sheet from accidentally moving up from the drum surface and hitting other mechanisms such as the ink jet head, thereby preventing damage to the sheet.

In the embodiment described above, the suction hole 36 formed in the drum 20 and the vacuum pump P as the suction means are connected to the tube shaft 4 provided in the flange 21.
9, and this tube shaft was used as the rotation center axis of the drum.Other examples of the connection means between the drum and the intake means and the drum drive mechanism will be described below. In addition, in the following description, the same reference numerals are attached to the members that have already been described.

In FIG. 15, the drum 20 is fixed to a drum support shaft 72 via a pair of flanges 70, 71, and the drum support shaft 72 has bearings 75, 76 mounted on immovable side plates 73, 74 of the printing device. It is rotatably supported through the Code 75a,
76a is a bearing holder.

As shown in FIG. 8, in one flange 70, an air passage 42 is formed by a groove 70a, a rubber packing 45, and a pressing plate 46, similar to that shown in FIG. Further, in the embodiment described here, holes 45b and 46b into which the drum support shaft 72 is inserted are formed in the rubber packing 45 and the pressing plate 46, as shown in FIG.

The tube shaft 77 of the flange 70 is connected to the drum support shaft 72
After the fixing screw 7 is inserted into the first step 72a of the
8, it is fixed substantially integrally with the support shaft 72. Further, the first step portion 72a of the support shaft includes:
one end 72b reaches the air passage 42;
A groove 72c extending in the axial direction is formed. On the other hand, on the inner circumferential surface of the tube shaft 77, one end 77a is provided.
An axially extending groove 77b is formed which is connected to the air passage 42. The groove 72c and the groove 7
7b are positioned opposite to each other. A hole 77c passing through the inside and outside of the tube shaft 77 is bored at the other end of the groove 77b.

A pair of bearings 79 and 80 are fitted onto the outer periphery of the tube shaft 77 with the hole 77c interposed therebetween. The bearings 79, 80 are held in a bearing housing 81 having a joint 82. The bearings 79 and 80 are of the seal type, and the bearing housing 81
and tube axis 77 to form an annular space 83.

The joint 82 is connected to the vacuum pump P via the electromagnetic valve 57 by a vacuum hose (not shown). Therefore, drum 20
The suction hole 36 bored in the suction pipe 39, the air passage 42, the groove 72c and the groove 77b, and the annular space 8
3. Vacuum pump P (19th
(see figure).

Further, a threaded portion is formed at one end of the first step portion 72a of the drum support shaft 72, and the flange 70 is connected by a nut 84 screwed onto the threaded portion.
In Figure 8, it is pushed to the right. this nut 8
4, the pressure plate 46 and the step portion 72d of the support shaft
The sealing member 85 provided between the stepped portion 72d
The air passage 42 and the support shaft 7
Maintains airtightness between the two. Therefore, the screw 78 is tightened after the nut 84 is tightened.

The bearings 79, 80 are held in position so as not to rotate by a detent 86 that locks the joint 82.

On the other hand, the suction hole 52 that sucks the rear end of the sheet is also connected to the vacuum pump P in the same way as described above, but in this configuration, the electromagnetic valve provided between it and the vacuum pump P is 58 is the only difference, so the 15th
The same reference numerals are used in the figures.

In FIG. 15, the drum 20 has a support shaft 72
The spacer 8 is given a rightward movement habit by an elastic spring 88 wound around the left second step 72e, and the spacer 8 is fitted into the right second step 72e.
7 is positioned in contact with a bearing 76. On the right side of the support shaft 72 is a one-way clutch 9.
A gear 89 is provided via 2, and an encoder 91 is further connected to the shaft end via a joint 90.

The gear 89 rotates the drum at a relatively low speed (for example, 30 rpm) when winding the sheet and discharging the sheet, and is connected to a drive source of a printing device (not shown). The rotation of this gear 89 is
The rotation of the support shaft 72 is transmitted to the support shaft 72 via the one-way clutch 92, and the rotation of the support shaft 72 is not transmitted to the gear 89.

The encoder 91 is supported by a support plate 93, and according to the rotation of the support shaft 72, the encoder 91 determines the timing of the operation of the electromagnetic valves 57, 58 and other mechanisms that operate in accordance with the rotation of the drum.

On the other hand, in FIG. 15, a drum drive motor 95 is connected to the left end of the support shaft 72 via a joint 94. This motor 95 rotates the drum 20 at a relatively high speed (for example, 1000 rpm) during printing, and is substantially directly connected to the drum. The motor 95 is supported by a support plate 96 fixed to the side plate 73. In FIG. 15, reference numeral 95a represents a brake.

As shown in Fig. 15, a suction pipe is provided on the inner surface of the drum, and air is sucked from the partial concave part of the flange through the rotation center hollow part, and the non-rotating part covering the hollow part is connected to a vacuum pump. Since the drive motor and encoder can be directly connected to the support shaft of the drum, it is possible to drive the drum and generate signals with high precision.

In the example shown in FIG. 15, the gear 89 rotates the drum 20 at a low speed when the sheet is clamped, and the motor 95 rotates the drum 20 at a high speed during the printing operation after clamping.
Suction hole 3 for clamping the front and rear ends of the sheet
Air suction from the encoder 91
The actuation timing of electromagnetic valves 57 and 58 is controlled based on signals from. In addition, the suction hole 36,
The operation timing of 52 is the same as in the embodiment described above.

In the embodiment shown in FIG. 15, means for connecting the suction holes 36 and 52 for sucking the leading and trailing ends of the sheet to the outside are provided at both ends of the drum. It can be provided at the end.

9 and 10, the drum support shaft 72 has a flange 70A having a tube shaft portion 77A that is longer than the tube shaft portion 77 shown in FIG.
After being tightened with screws 78, they are substantially integrally fixed. Note that the air passage that connects to the suction hole 36 that suctions the leading edge of the sheet is the same as that shown in FIG. The air passage will be explained.

In addition to the groove 70a forming a part of the air passage 42, the flange 70A is provided with a groove 70aA forming a part of another air passage 42A. These two grooves are each airtightly covered with a packing 45A and a pressing plate 46A.

A spacer 97 is placed between the tube shaft portion 77A and the bearing 79, and a pair of bearings 80 are attached to the tube shaft portion 77A.
A, 79A is arranged. Both of these bearings are of the seal type, and are held in a bearing housing 81A to form an annular space 83A between them. This annular space 83A
One end of the joint 82A is opened.
The joint 82A is held by a detent 86A.

On the other hand, one end 77 is provided on the inner peripheral surface of the tube shaft portion 77A.
A groove 77bA is formed with aA located in the air passage 42A and a hole 77cA bored at the other end communicating with the annular space 83A. Further, the support shaft 72 has a groove 77bA facing the groove 77bA.
A groove 72cA is formed with one end 72bA located in the air passage 42A.

The joint 82 is connected to a solenoid valve 57 (see FIG. 19) that substantially controls the driving of the sheet end clamp, and the joint 82A is connected to a solenoid valve 58.

When the drum 20 rotates, the flange 70A and the support shaft 72 rotate as one, and the holes 77c and 7 are connected to the suction holes 36 and 52, respectively.
7cA is always in communication with the annular spaces 83 and 83A.

As described above, as shown in FIG. 9, when the airtight connection means for the rotating part and the non-rotating part are arranged together at one end of the drum, the vacuum pump P (19th
This makes it easier to install the vacuum hose (see figure), and is also advantageous in terms of space.

In addition, in FIG. 9, the suction hole 36 and the same 52
are provided with a phase of 180 degrees in the circumferential direction of the drum 20, and the air passages connected to these are also arranged accordingly, but this is for illustration purposes only, and the positions of both holes are different from each other. Of course, they may be positioned as shown in FIG.

As already mentioned, the present invention is characterized in that the sheet gripper and the sheet are both attracted to the drum surface by air suction from the suction holes provided in the drum. An example of the relative positions of the suction holes, the sheet gripping claws, and the sheet is shown in FIG. It's becoming like that.

Another embodiment of the present invention will be described with reference to FIGS. 16 to 18, in which holes for adsorbing the sheet and the sheet gripper are formed in correspondence with each other.

A sheet suction hole 36A is provided in the portion of the drum 20 that is held down by the sheet gripping claw 23 for sucking the sheet S whose leading edge Sa is brought into contact with the stopper 25.
and a gripping claw suction hole 36B for sucking the sheet gripping claw 23. Each of the suction holes 36A, 36B communicates with a suction pipe 39, as shown in FIGS. 17 and 18.

Then, with the sheet gripping claw 23 open (see FIG. 11), the sheet S is fed between the claw and the drum, and after its leading edge Sa abuts against the stopper 25, the suction pipe 39 is opened. When the suction force of the vacuum pump P (see FIG. 19) acts through the suction holes 36A and 36B, air is suctioned from both the suction holes 36A and 36B. At this time, a spring force (see spring 31 in FIG. 11) is applied to the sheet gripping pawl 23 to cause it to open.
The leading end of the free sheet S is attracted to the suction hole 36A before the sheet gripping claws.
When the suction hole 36A is closed by the sheet, the amount of air suction from the other suction hole 36B increases substantially, and the sheet gripping claw 23 is attracted to this hole 36B against the spring force.

In the embodiment shown in FIG. 16, the suction hole for sucking the sheet and the suction hole for sucking the sheet gripper are provided separately, so that the leading edge of the sheet can be clamped more reliably. You can expect it. Note that, in FIG. 16, a hole for attaching a suction pipe (see reference numeral 38 in FIG. 6) is not shown.

In the embodiment shown above, in order to clamp the leading edge and the trailing edge of the sheet, a suction hole for sucking the leading edge of the sheet and the sheet gripping claw, and a suction hole for sucking the trailing edge of the sheet are provided. An example has been described in which the suction pipe 39 and the suction pipe 53 (see FIG. 4) are arranged inside the drum in order to independently connect the hole and the pump. If such a configuration is adopted,
Although the suction force on the leading and trailing ends of the sheet can be made to act strongly on each other, the present invention is not limited to this, and the suction pipes 39 and 53 are eliminated, the drum itself is configured airtight, and the interior of the drum is By applying a negative pressure to the sheet, there is a device that attracts not only the sheet but also the sheet gripping claw.

By applying negative pressure inside the drum to close the sheet gripping pawl, a mechanical element for closing the sheet gripping pawl is omitted, and a sheet clamping device having a simple structure and reliable operation can be obtained.

Further, although the printing apparatus shown in FIG. 1 clamps the leading and trailing ends of the sheet first, there are some apparatuses in which it is sufficient to clamp only the leading edge of the sheet. Of course, it can also be applied to devices.

As described above, according to the apparatus of the present invention, which sucks air through the suction hole provided in the drum and attracts both the sheet gripping claw and the sheet to the drum surface to clamp the sheet to the drum, the sheet gripping claw is Since a mechanical structure for closing is not used, the number of parts is reduced and costs are kept down, and the simple structure provides stable operation, so that the sheet can be reliably clamped.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a printing device employing an inkjet recording method as an example of a device to which the present invention is applied, FIG. 2 is a perspective view showing an embodiment of the present invention, and FIG. Left side view of Fig. 2, No. 4
Figure 5 is a cross-sectional view of the same, Figure 5 is an exploded perspective view of the main part showing the configuration of the air passage connecting the suction hole and the intake means,
The figure is a plan view of the main part of Fig. 2, Fig. 7 is a vertical cross-sectional view showing an example of a method of connecting the suction hole and the suction means, and Fig. 8 is a longitudinal cross-sectional view showing another example of the method of connecting the suction hole and the suction means. 9 is a longitudinal sectional view showing still another example of the same as the above, FIG. 10 is a perspective view of the main part of the example shown in FIG. 9, and FIG. 11 is a part showing the sheet gripping claw in an open state. A broken side view, FIG. 12 is a sectional view taken along the line A-A in FIG. 6, and FIG. 13 is a sectional view taken along the line B-B in FIG.
4 is a sectional view taken along the line CC in FIG. 6, FIG. 15 is a sectional view showing an example of a drum drive mechanism, FIG. 16 is a plan view of main parts showing another example of the present invention, and FIG. 1st
6, FIG. 18 is a sectional view taken along line E-E in FIG. 16, FIG. 19 is a line diagram showing an example of the air flow path between the drum and the intake means, and FIG. FIGS. 22 to 22 are partially cutaway side views illustrating the sheet clamping operation, FIG. 23 is a sectional view showing an example of a sheet handling device, and FIG. 24 is a sectional view thereof. 20...drum, 21...flange, 23...
Sheet gripping claw, 36, 36A... Sheet suction hole, 36B... Sheet gripping claw suction hole, 53...
Suction hole, 57, 58...electromagnetic valve, 39...suction pipe, P...pump.

Claims (1)

[Scope of Claims] 1. In a sheet clamping device that clamps a sheet to a drum by pressing the edge of the sheet against the drum surface using sheet gripping claws provided parallel to the axis of the drum, A suction hole provided in the drum in the portion held by the sheet gripping pawl including the sheet end, which is a plurality of holes that communicate the inside and outside of the drum, and which is provided with a sheet gripping pawl that has an opening habit. and a suction means connected to the suction hole, and the suction means sucks air from the suction hole to attract both the sheet gripping claw and the sheet to the drum surface. Seat clamp device.