JPH023710B2 - - Google Patents

Description

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

As a device for winding a sheet material onto a drum,
For example, there are master sheet loading devices in offset printing machines, transmission original and recording paper loading devices in facsimile machines, sheet loading devices in copying machines, etc., and various types of these have already been proposed and put into practical use. ing.

Now, as an example of a conventional device for winding and fixing a sheet around a drum, 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 a sheet gripping claw 4 that constitutes a part of a sheet leading edge pressing device. 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 rotational direction of the drum.

The paper feeding device 5 is a well-known suction cup type automatic paper feeding device, and includes a suction cup 8, a feed roller 9, an idle roller 10, and a sheet mounting table 11.
The suction cup 8 has a home position indicated by a chain line 8, 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. A mechanism and suction means for causing the suction cup 8 to perform the above-mentioned operation 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. Then, 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, and its leading edge is opened. It is inserted between the 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, and its trailing end is clamped by a sheet trailing edge pressing device (not shown).

The recording device 6 includes 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, since the drum 2 wound with the sheet rotates in the direction of the arrow, the ink jet head 12 is relatively moved in the main scanning direction. Then, the inkjet head 12
The printer forms a recorded image in a dot matrix by ejecting minute ink droplets toward the drum surface (sheet) in response to a signal applied thereto.

Note that the sheet clamped to the drum 2 may be ordinary recording paper (printing paper) without any printing or writing, or may be a sheet created by printing a predetermined format in another format. It may be recording paper (printing paper) that is

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 come into contact with and separate from it, and a sheet ejecting table to remove the sheet peeled from the drum surface. 17.

Next, an example of a sheet clamp device applied to the printing apparatus will be described using FIG. 2.

In this figure, the sheet S is wrapped around the surface of the drum 2,
The leading edge of the sheet is held by the sheet leading edge pressing device 20.
In addition, the sheet rear end portions are shown being held down by the sheet rear end pressing device 21.
A single slit 2 is formed on the surface of the drum 2 in order to accommodate a support shaft that supports a sheet gripping claw, which will be described later.
2 are provided over the entire length of the drum 2, and a plurality of holes 23 are provided on the lag side of the slit 22 in the drum rotation direction.
are arranged at equal intervals along the entire length of the drum. Further, a recessed portion 24 is provided on the surface of the drum 2 on the advancing side of the slit 22 in the drum rotation direction, extending along the entire length of the drum.

The sheet leading edge pressing device 20 includes a sheet holding claw 4 that can press the leading edge of the sheet S against the surface of the drum 2.
Then, fix this sheet holding claw 4 to one end and open the hole 2.
a plurality of levers 26 arranged corresponding to 3;
This lever 26 is supported by a support shaft 27 which is rotatably supported by flanges on both sides of the drum 2, and one end of which is locked to the other end 26a of the lever at the farthest end. Except for the spring 29 whose other end is locked to a pin 28 planted on the outer surface and biases the flat sheet gripping claw 4 in a direction to press it against the drum surface, and the lever at the farthest end, the other levers are It consists of a plurality of substantially arc-shaped protruding members 30, one end of which is fixed to a substantially central portion between the pivot point 27 and the end portion 26a, and the other end of which faces the hole 23. This protruding member 30 is used to push up the sheet via a mechanism (not shown) and peel the sheet from the drum surface after printing is completed.

The sheet trailing edge pressing device 21 consists of an arm 31, a pressing roller 32, a spring 33, etc.
are attached to the drum shaft 3 via bearings 3A at their base ends on both sides of the drum 2, and their distal ends extend beyond the drum surface. A long hole 31B is bored at the tip of the arm 31, and a support shaft 32A of a presser roller 32 having a total length approximately equal to the drum is loosely fitted into the long hole 31B.
The presser roller 32 can escape from the recessed portion 24 and roll on the drum surface. Spring 3
3 is configured such that both ends thereof are engaged with a pin 34 and a support shaft 32A, respectively, which are implanted approximately in the center of the arm 31, so as to bias the flat pressing roller 32 in a direction to press it against the drum surface.

When the drum 2 rotates at high speed with the illustrated sheet S wrapped around it and starts a printing operation, centrifugal force acts on each component of the sheet clamping device. Particularly, focusing on the sheet leading edge holding device, the sheet gripping pawl 4 and the protruding member 30 are fixed to the lever 26 disposed in the radial direction on the lagging side in the rotational direction of this lever. The centrifugal force acting on the protruding member 30 generates a force that tends to move the sheet gripping claw 4 outward from the center of the drum. Therefore, the pressing force exerted by the spring 29 on the leading edge of the sheet against the drum surface is reduced, causing the sheet to shift or come off.

As mentioned above, the conventional seat clamp method
All of them were so-called mechanical devices, consisting of complex combinations of cams, levers, etc. 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. Moreover, since the sheet clamp member is urged away from the drum surface (sheet) by the centrifugal force accompanying drum rotation, in order to prevent the resulting decrease in sheet clamping force, Mechanisms are becoming increasingly complex.

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 components, the above disadvantages can be eliminated, the structure can be simple and inexpensive, and the clamping force can be reduced during drum rotation. The object of the present invention is to provide a seat clamp device that does not weaken.

The object of the present invention is to provide a spindle which is pivotally connected to a flange of a drum around which a sheet is wound, a base end which is attached substantially integrally to the spindle, and a free end which is attached to the surface of the drum. The sheet clamping device is equipped with a sheet gripping claw that can be freely moved toward and away from the drum, and the weight is movable in one direction by centrifugal force caused by rotation of the drum, and the weight is connected to the support shaft. and a connecting means for rotating the support shaft in a direction in which the sheet gripping pawl cooperates with the drum surface to increase the force with which the sheet is gripped by movement of the weight. This is accomplished by a clamping device.

According to the present invention, in order to increase the force for gripping the sheet, a separate power source is not provided, and the centrifugal force acting on the weight as the drum rotates is utilized. In other words, it is possible to provide a sheet clamping device that has a simple structure, is low in cost, and whose clamping force does not weaken even while the drum is rotating.

In other words, the feature of the present invention is that the sheet gripping pawl, which grips the sheet in cooperation with the drum surface, is connected to the weight via a swingable support shaft, and the sheet gripping pawl that grips the sheet in cooperation with the drum surface is connected to the weight via a swingable support shaft, thereby reducing the weight caused by the centrifugal force caused by the rotation of the drum. By moving the weight, the sheet gripping pawl is rotated via the connecting means to increase the force for gripping the sheet.

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 master sheet in an offset printing machine, a transmission document or recording paper in a facsimile machine, a sheet-shaped photoreceptor in a copying machine, and other sheet-like materials. It also includes.

In FIG. 3, a single slit 22 is provided on the surface of the drum 2 over the entire axial length of the drum 2, and a support shaft 27 is disposed within the slit 22 and is rotatably attached to flanges on both sides of the drum 2. It is supported on. The free end 4a of the sheet gripping claw 4 is connected to the base end 4b so that it can freely approach and separate from the surface of the drum 2.
is attached to the support shaft 2 via an L-shaped bracket 41.
It is fixed to 7.

The end of the support shaft 27 protrudes outside the drum flange, and one end of the approximately L-shaped lever 42 is connected to the support shaft 2.
It is fixed to 7. A weight 43 is fixed to the other end of the lever 42. Since the weight 43 is located on the opposite side of the gripping claw 4 with respect to the support shaft 27, the weight of the weight 43 causes the support shaft 27 to rotate counterclockwise in the figure via the lever 42. Since the gripping claw 4 is separated from the surface of the drum 2, a spring 44 is attached to a pin 45 implanted approximately in the center of the lever 42 to prevent this and allow the flat gripping claw 4 to press against the drum surface. and a pin 46 installed on the outside of the drum flange.

With the above configuration, when the rotational speed of the drum 2 increases after the sheet is held in its mouth, the weight 43
Due to the centrifugal force acting on the drum, the weight 43 tends to move in the direction indicated by the arrow, and the gripping claw 4 can be pressed even more strongly against the drum surface via the lever 42. Since this pressing force is proportional to the square of the rotational speed, there is an advantage that the sheet clamping performance is further improved as the drum rotation speed increases.

Next, another embodiment of the present invention is shown in FIGS. 4 to 6. In this case, unlike the previous embodiment, the weight 50 is movably housed inside the drum 2. That is, in these figures,
A round rod-shaped weight 50 is arranged over approximately the entire length of the drum, and a support shaft 50A fixed to both ends thereof penetrates a long hole 51A formed in the drum flange 51 and projects to the outside of the flange 51. . This spindle 5
One end of the lever 52 is fixed to 0A, and the lever 52
The other end is fixed to the support shaft 27. Support shaft 27
are arranged in the slit 22, are rotatably supported by drum flanges on both sides, and are supported by a support shaft 27.
As in the previous embodiment, one side of the L-shaped base end 41a is fixed to the bracket 41, and the other side of the bracket 41 is fixed to the base end of the sheet gripping claw 53. In this embodiment, the sheet gripping claw 53 has a plurality of stoppers 53A bent toward the center of the drum at equal intervals over its entire length (see FIGS. 4 and 6). ). A hole 2A corresponding to the stopper 53A is formed on the surface of the drum 2 so that the stopper 53A can be accommodated and removed. This stopper 53A allows the leading ends of the sheets S to be aligned. Next, in order to prevent the sheet gripping pawl 53 from separating from the drum surface due to the weight of the weight 50, a spring is applied which gives the habit of pushing the flat lever 52 clockwise about the support shaft 27 in FIG. 54 is the locking portion 52
A and a locking portion 55 provided on the drum flange. Reference numeral 56 indicates a stopper that abuts against the lever 52 at the position shown in FIG. 6, where the sheet gripping claw 53 is separated from the drum surface by a mechanism not shown. With the structure described above, the function is basically the same as in the previous embodiment, but since the weight 50 is stored over the entire length of the drum, it is easy to increase the weight of the weight, and the seat clamp It has the advantage of increasing capacity.

Another embodiment of the invention is shown in FIG. That is, in all of the above-described embodiments, a lever is used as a connecting means for converting the movement of the weight into swinging of the sheet gripping claw, but in this case, the lever is used to swingably support the sheet gripping claw 53. A gear 27G is fixed to the end of the support shaft 27. The other gear 52G that engages with this gear 27G is the support shaft 5.
7, and the support shaft 57 is rotatably supported by the drum flange. A weight 50 is fixed to the other end of the lever 52, which has one end fixed to the gear 52G. According to this method, as the drum 2 rotates, the weight 50 moves counterclockwise in the figure around the support shaft 57, and the sheet gripping claw 53 moves in the figure by the engagement of the gears 52G and 27G. Since it rotates in a clockwise direction, the same effect as in the previous embodiment can be achieved.

Further, the application of the present invention is not limited to inkjet printing devices, but may be applied to any device to which a device for winding a sheet around a rotating drum can be applied.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing an inkjet printing device using a conventional sheet clamp device, FIG. 2 is a partially cutaway side view showing the sheet clamp device of the device, and FIG. 3 is a diagram showing an embodiment of the present invention. A partially sectional side view, FIGS. 4 and 5 are a partially sectional front view and a partially sectional plan view showing another embodiment of the present invention, and FIGS.
This figure is a partially sectional side view showing the above embodiment in a state separated from the drum surface, and FIG. 7 is a partially sectional side view showing still another embodiment of the present invention. 2...Drum, 4...Sheet gripping claw, 42...
Lever, 43... weight.

Claims (1)

[Claims] 1. A support shaft pivotally attached to the flange of the drum around which the sheet is wound, and a base end substantially integrally attached to the support shaft, and a free end movable toward and away from the surface of the drum. In a sheet clamping device equipped with a sheet gripping claw, a weight movable in one direction by centrifugal force accompanying rotation of the drum is connected to the support shaft, and the weight is connected to the support shaft. A sheet clamping device comprising a connecting means for rotating the support shaft in a direction in which the sheet gripping claw cooperates with the drum surface to increase the force of gripping the sheet by movement.