EP0495411B1

EP0495411B1 - Paper clamping mechanism

Info

Publication number: EP0495411B1
Application number: EP19920100357
Authority: EP
Inventors: Kwang-Ho Dongshin Apt. Ro; Moon-Bae Ingye Apt. Park
Original assignee: Samsung Electronics Co Ltd
Current assignee: Samsung Electronics Co Ltd
Priority date: 1991-01-12
Filing date: 1992-01-10
Publication date: 1996-09-11
Anticipated expiration: 2012-01-10
Also published as: DE69213484T2; EP0495411A2; DE69213484D1; EP0495411A3

Description

The present invention relates to an apparatus for holding a paper in a video printer, and more particularly to a paper clamping mechanism according to the preamble part of claim 1.
Generally a video printer is introduced for printing a picture recorded by acquiring a video signal momentarily and the picture to be reproduced on a monitor through a recording device such as a still camera. There is disclosed a method of heat conductive sublimation for sublimating each of three colors of yellow(Y), magenta(M) and cyan(C) successively, which enables a gradation of the color to be expressed freely, thus expressing all kinds of colors of the video signal.
With reference to Fig.1, the video printer comprises an ink ribbon 16 applied with a dye of three colors Y, M and C consecutively, a heat sensitive record paper 15, and a thermal printing head (T.P.H.) 10 which is pressed against a platen drum 1 selectively.
If the platen drum 1 rotates after fixing the record paper 15 on its side surface, the record paper 15 and the ink ribbon 16 advance at the speed of the platen drum 1. Each of dyes Y, M and C is sublimated by the heat of the T.P.H. 10, and is absorbed on the record paper 15. Various rates of the absorbed dyes Y, M and C make various synthesized colors with different gradation so that the printing of all kinds of colors is possible.
In the operation as described as above, a device for fixing the record paper on the platen drum of the video printer is required because the platen drum rotates three times for complete printing onto the record paper.
As shown in Fig.2, there is disclosed a holder for fixing the record paper on the platen drum, wherein the holder 23 is installed around a shaft 13 of the platen drum 1 and set by a spring 6, and a clamp bracket 22 actuates a side end of the holder 23 so as to let the holder fix or release the record paper.
The holder 23 is pushed by the clamp bracket 22 rotating anti-clockwise and is lifted from the surface of the platen drum 1 so as to receive the record paper. By returning the clamp bracket 22, the holder 23 is released to its original position by a restoring force of the spring 6 so as to fix the record paper 15 by pressing.
The T.P.H. 10 is lifted at a predetermined position of the circumference of the platen drum 1 so as to provide an opening for passing the holder 23 when the platen drum 1 rotates. The T.P.H. 10 generates heat during the pressing of the ribbon just after passing the holder through the opening, transcribing the dyes on the ribbon to the heat sensitive record paper.
By repeating the above operation, the three colors of Y, M and C are printed. Thereafter, an arm end of the clamp bracket 22 pushes the holder 23 by rotating anti-clockwise, releasing a forefront tip of the printed record paper and discharging the printed record paper. At this time, the T.P.H. should press the record paper, because in case of the T.P.H. being detached from the record paper, the friction force is not supplied to the record paper and though the ribbon advances, the ribbon is damaged.
Accordingly it is required for advancing a black portion of the ribbon to provide an additional length of the ribbon even after printing the three colors completely. And it takes more time for the platen drum to rotate once more in addition to an actual printing time. So it results in wasting of printing time and material.
From EP-A-272 802, a printer is known comprising a bracket which is formed with a generally circular internal camtrack which cooperates with a twin-lobed cam fixed for rotation with a shaft in an axial position.
From EP-A-403 775, a printer is known having a platen and a clamper wherein the clamper may be lifted from the platen when a pin comes into direct contact with a movable hook. In order to discharge the paper, the platen moves in an opposite direction as during paper feeding.
Furthermore, in this document, a printer is disclosed having a swinging arm for engagement at its top or bottom part with a clamper pin. In the charging state, the swinging arm is moved in one direction and in the discharge state, the swinging arm is moved in an opposite direction.
The object of the present invention is to provide a paper clamping mechanism which is simple in its structure and provides for a reduction of printing time in a color video printer.
This object is solved by a clamping mechanism having the features of claim 1.
Preferred embodiments of the inventive clamping mechanism are subject to various dependent claims.
These and other features of the invention will be understood from the following description of illustrative embodiment, with reference to the drawings, in which:

Fig.1 is a schematic diagram of a video printer;
Fig.2 is a schematic diagram of a conventional paper holder of a video printer;
Fig.3 is an exploded view of a paper holder of the inventive video printer;
Fig.4 is an exploded view of a heat sensitive recording head of the inventive video printer; and
Fig.5 is an operation diagram of a paper holder of the inventive video printer.

With reference to Fig.3, two clamp brackets 2 which are connected to both side ends of a holding bar 3 respectively, are installed on the top and bottom surface of a platen drum 1 so as to rotate around a hinge 4 formed in each clamp bracket 2. A protrusion or projecting pin 5 is projected from the outer surface of the clamp bracket 2 with being apart from the hinge 4. One terminal of a spring 6 is mounted on an inside surface of the clamp bracket 2, and the other terminal thereof is mounted on the bottom or top surface of the platen drum 1, so as to pull the holding bar 3 toward the platen drum 1 by its resilient force. Another protrusion or projecting pin 7 is formed near the spring 6 with opposing to the protrusion pin 5. Thus a flange 9 of a solenoid 8 is contactable with the protrusion pins 5 and 7.
With reference to Fig.4 and Figs.5A to 5H, T.P.H. 10 is positioned over the platen drum 1 and is connected to a roller 12 through a leaf spring 11 at the forefront of the T.P.H. 10. Middle portion of the clamp bracket is curved toward the holding bar to form a slide groove 14 between the curve of said middle portion and a shaft 13 of the platen drum 1. Thus, when the flange 9 of the solenoid 8 pushes the protrusion pins 5 and 7, the clamp bracket 2 moves around the shaft 13. A pair of discharging rollers 17 discharges a heat sensitive record paper 15, and a ribbon 16 is positioned between the T.P.H. 10 and the platen drum 1.
The operation of the present invention will be described as follows.
The record paper is transmitted through a guide passage and which is detected by a sensor (not shown). The flange 9 of the solenoid 8 pushes the protrusion pin 5 of the clamp bracket 2. So, the clamp bracket 2 is rotated anti-clockwise around the hinge 4 while the slide groove 14 moves around the shaft 13. Further, the holding bar 3 moves toward from the surface of the platen drum 1 to be apart from the circumference of the platen drum 1 as shown in Fig.5B.
As shown in Fig.5C, the clamp bracket 2 is rotated at the hinge 4 clockwise, returning to its original position by a resilient force of the spring 6, as soon as an electric source of the solenoid 8 is cut. Accordingly the forefront tip of the record paper 15 is fixed between the holding bar 3 and the platen drum 1. Accordingly the record paper 15 moves along the surface of the platen drum 1 according as the platen drum 1 rotates in order to print a given color.
As shown in Fig.5D, if the holding bar 3 along with the record paper 15 delivers to the position A, the T.P.H. 10 is lifted so as to pass the holding bar 3. The platen drum 1 rotates further until the holding bar 3 arrives at a point B. Thereafter as shown in Fig.5E, the roller 12 of the T.P.H. 10 presses the ribbon 16 on the record paper 15 to provide a friction force to the record paper 15. Thereby the printing operation is performed by heat generated from the T.P.H. 10. The above printing operation is as same as that of the conventional video printer. That is, during the holding bar 3 continues to rotate further from the point B, the T.P.H. 10 generates heat and sublimates a dye of Y color, printing the Y color on the record paper 15 as shown in Fig.5F.
When the holding bar 3 returns to the point A after completing the printing of Y color, as shown in Fig.5D, the T.P.H. 10 is lifted again for passing the holding bar 3. The platen drum 1 further rotates to deliver to the point B, and at this time the color M is printed on the record paper 15 by repeating the same operation as shown in Figs.5E and 5F.
When the holding bar 3 arrives at the point B after printing the color Y and M in the above operation, it rotates by the angle of 15° more after two and half revolutions, which is detected by the sensor. At this time, the platen drum stops rotating. Then the flange 9 of the solenoid 8 pushes the protrusion pin 7 of the clamp bracket 2 anti-clockwise so as to move the holding bar 3 from the point B to the direction of an arrow, the holder being apart from surface of the platen drum 1 as shown in Fig.5G, and the record paper 15 being lifted by its resilient force.
With reference to Fig.5H, when cutting an electric source of the solenoid 8, the holding bar 3 presses on the circumferential surface of the platen drum 1 by a restoring force of the spring 6, however the record paper being lifted above the holding bar at this time. Thereafter the platen drum 1 continues to rotate for printing the color C. The record paper in which only Y and M colors are printed is fixed on the platen drum safely by a friction force of the roller 12. The discharging roller 17 transmits the print-completed paper to a discharging tray right after printing completion.
In conclusion, the paper holder increases the printing speed by preventing the platen drum from rotating unnecessarily and prevents the waste of the ribbon by discharging the printed paper right after the completion of printing all colors.

Claims

A paper clamping mechanism for clamping a sheet of printing paper on a drum shaped platen of a printer comprising:
two clamp brackets (2) being connected to each other through a holding bar (3) for clamping said sheet of paper (15) on to the circumferential surface of said platen (1) whereby each clamp bracket being installed on the top or bottom surface of said platen (1) and being mounted rotatable around a hinge (4) formed in said clamp bracket (2);

a driving means (8,9) for actuating said clamp brackets (2) so that said holding bar (3) is movable in a position where it is spaced apart from the circumference of said platen (1);

a roller (12) installed on a thermal printing head (10) positioned in proximity of said circumference of said platen (1) for pressing a ribbon (16) to said sheet of paper (15); and

a spring means (6) for urging said holding bar (3) toward said platen (1) whereby said sheet of paper (15) is clamped on the platen (1),
characterized in that
each of said clamp brackets (2) has a curved groove (14) at a central position of the bracket and the hinge (4) is positioned outside a central portion for enabling an eccentric sliding of the bracket and in that

at least one bracket (2) has a pair of projecting pins (5,7) which are actuatable by driving means (8,9) whereby said first projecting pin (5) moves said holding bar upward upon actuation for the insertion of the sheet of paper (15) and said second projecting pin (7) moves said holding bar (3) upward upon actuation for the release of the clamped sheet of paper (15).
The mechanism according to claim 1, wherein said driving means comprises a solenoid (8).
The mechanism according to claim 1 or 2, characterized by further comprising a resilient rod (11) for connecting said roller (12) to said thermal printing head.