Drawing apparatus having fixing member for clamping material...

Printing – Flexible-sheet-securing devices

Reexamination Certificate

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Details

C101S477000, C101S463100

Reexamination Certificate

active

06334392

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a drawing apparatus for fixing a sheet-shaped recording material to an outer peripheral surface of a drum to draw an image on the recording material.
2. Description of the Background Art
Drawing apparatuses have been used for drawing images upon irradiation of various types of photosensitive materials with light. In a drum-type drawing apparatus, a photosensitive material is mounted on a recording drum which is rotatable in a primary scanning direction, and a recording head comprising a laser diode and the like moves in a secondary scanning direction parallel to a rotary shaft of the recording drum to draw an image on the photosensitive material.
FIG. 34
is a schematic perspective view of a recording drum in a conventional drawing apparatus. A plate
160
made of aluminum serving as a photosensitive material is mounted on a recording drum
150
shown in
FIG. 34. A
front end clamp
170
for fixing one end of the plate
160
and a rear end clamp
180
for fixing the other end of the plate
160
are attached to an outer peripheral surface of the recording drum
150
. The rear end clamp
180
contains a magnet, and is fixed by a magnetic force to a position, on the outer peripheral surface of the recording drum
150
, corresponding to the size of the plate
160
.
The recording drum
150
having the plate
160
attached thereto is rotated at relatively low speed around a rotary shaft
190
, so that an image is drawn on the surface of the plate
160
.
In recent years, a request to improve the efficiency of processing for drawing an image on the plate
160
has been made. In order to improve the efficiency of the drawing processing, the recording drum
150
having the plate
160
attached thereto must be rotated at high speed.
However, the rear end clamp
180
is fixed to the recording drum
150
by the magnetic force. When the recording drum
150
is rotated at high speed, therefore, the rear end clamp
180
moves on the outer peripheral surface of the recording drum
150
or is detached from the recording drum
150
, so that the plate
160
fixed to the recording drum
150
may be shifted in position and detached. Therefore, the recording drum
150
cannot be rotated at high speed.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a drawing apparatus capable of reliably fixing a sheet-shaped recording material of arbitrary size to an outer peripheral surface of a cylindrical drum.
Another object of the present invention is to provide a drawing apparatus capable of uniformly bringing a sheet-shaped recording material into close contact with an outer peripheral surface of a cylindrical drum.
A drawing apparatus according to one aspect of the present invention for drawing an image on a sheet-shaped recording material comprises a cylindrical drum having a rotary shaft and an outer peripheral surface and having a groove extending in the circumferential direction provided on the outer peripheral surface, a rotation driving device for rotating the drum around the rotary shaft, a fixing member provided so as to be attachable and detachable to or from the groove of the drum and so as to be movable along the groove for fixing the recording material to the outer peripheral surface of the drum, and a drawing unit for drawing an image on the recording material fixed on the outer peripheral surface of the drum, the fixing member comprising a main body member having one side part for pressing one end of the recording material against the outer peripheral surface of the drum, an engaging member provided so as to project on the side of the lower surface of the main body member and engaged with the inside of the groove of the drum, and urging means for urging the other side part of the main body member in the direction away from the outer peripheral surface of the drum.
In the drawing apparatus, the fixing member is provided so as to be attachable and detachable to or from the groove of the cylindrical drum and so as to be movable along the groove. The sheet-shaped recording material is mounted on the outer peripheral surface of the drum, and is fixed by the fixing member.
The engaging member provided in the main body member of the fixing member is engaged with the inside of the groove of the drum, thereby making it possible to fix the fixing member to the drum. The one end of the recording material is interposed between the one side part of the main body member and the outer peripheral surface of the drum, and the other end of the main body member is urged in the direction away from the outer peripheral surface of the drum by the urging means. Thus, the one end of the recording material is pressed against the outer peripheral surface of the drum by the one side part of the main body member. In this state, the drum having the recording material fixed thereto can be rotated around the rotary shaft by the rotation driving device.
The engaging member can be released from the groove of the drum by releasing the engagement of the engaging member provided in the fixing member. Thus, the fixing member can be moved in the circumferential direction along the groove on the outer peripheral surface of the drum. Consequently, the recording material of arbitrary size can be reliably fixed to the outer peripheral surface of the drum.
It is preferable that the length of the one side part of the main body member which is determined on the basis of the engaging member in the circumferential direction of the drum is smaller than the length of the other side part of the main body member.
In this case, at the time of rotation of the drum, centrifugal forces are exerted, respectively, on the one side part and the other side part of the fixing member. Since the length of the one side part of the main body member is smaller than the length of the other side part of the main body member, a rotation moment generated by the one side part of the main body member centered around the engaging member is smaller than a rotation moment generated by the other side part of the main body member, so that a force is exerted in the direction in which the other side part of the main body member separates from the outer peripheral surface of the drum. As a result, the one end of the recording material is firmly pressed against the outer peripheral surface of the drum by the one side part of the main body member.
The higher the rotational speed of the drum is, the larger the force to separate the other end of the main body member from the outer peripheral surface is, and the larger a force for the one side part of the main body member to press the one end of the recording material against the other peripheral surface of the drum is. Even when the drum is rotated at high speed, therefore, the recording material on the outer peripheral surface of the drum is not shifted in position and detached.
A weight may be provided in the other side part of the main body member. In this case, at the time of rotation of the drum, a centrifugal force is exerted on the weight provided in the other side part of the main body member, and a force is exerted in the direction in which the other side part of the main body member separates from the outer peripheral surface of the drum. As a result, the one end of the recording material is firmly pressed against the outer peripheral surface of the drum by the one side part of the main body member.
The higher the rotational speed of the drum is, the larger the centrifugal force exerted on the weight on the other side part of the main body member is, and the larger the force for the one side part of the main body member to press the one end of the recording material against the outer peripheral surface of the drum is. Even when the drum is rotated at high speed, therefore, the recording material on the outer peripheral surface of the drum is not shifted in position and detached.
The urging means may comprise a spring provided between a lower surface of the other side part of the main body member and the

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