JPH022711B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention reliably protects the thermal recording head from abnormally high temperatures by attaching a temperature fuse having predetermined fusing characteristics to the heat sink provided in the thermal recording head. This invention relates to a heat-sensitive recording head protection device.

Generally, in a thermal recording head, a plurality of (for example, 2048) thermal recording elements, which are heating resistors, are arranged in a row, and when performing thermal recording, the thermal recording elements are selected according to the recorded information. It is now driven by heat generation. When a pulse current is applied to a heat-sensitive recording element selected according to recording information, the heat-sensitive recording element generates heat, and this heat causes the heat-sensitive recording paper to develop color and perform heat-sensitive recording. be. By the way, heat-sensitive recording heads must be protected from abnormally high temperatures in order to maintain their service life, but the reality is that sufficient protection measures have not been taken in the past.
Conventionally, the temperature of the thermal recording head is detected directly or indirectly using a thermistor, etc., and if the detected temperature is within a certain temperature range, the protection circuit applies an applied current or voltage depending on the temperature. or by controlling the magnitude of the applied pulse width.
This prevents uneven recording density in thermal recording and prevents the thermal recording head from becoming abnormally high temperature. Although these protective measures are effective to some extent, they are not enough to protect against extremely abnormal high temperatures. It is not. This is because the thermal recording element may be continuously driven to generate heat depending on the failure that occurs in the protection circuit itself or in the drive circuit section between the protection circuit and the thermal recording element. In such a case, the heat-sensitive recording head will not be able to be reliably protected because the temperature will be so high that it will cause smoke and abnormal odor from the thermal recording paper and cause deformation of plastic parts due to the heat. In particular, thermal recording type facsimile machines that have become popular in recent years and are capable of automatic reception are powered on and can be operated at all times, even on holidays or late at night, when unattended, so such abnormalities can occur. It is essential to protect not only the thermal recording head, which is more expensive than high temperatures, but also the entire facsimile apparatus and building.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermal recording head protection device that can reliably protect a thermal recording head from abnormally high temperatures that cause smoke, strange odors, and thermal deformation.

For this purpose, the present invention focuses on the fact that the thermal recording head is equipped with a heat sink for dissipating the heat generated by the thermal recording element into the air, and thermally connects a fuse that melts at a predetermined temperature. A suitable number of fuses are installed in a connected state, and the power supply to the thermal recording head is cut off at least when one of the fuses is blown by heat from the heat sink.

Hereinafter, the present invention will be explained with reference to the accompanying drawings.

The attached diagram shows the main circuit configuration of an example of the protection device according to the present invention. According to this, fuses 2 and 3 having predetermined fusing characteristics are attached to the heat sink 1 described above so as to receive heat from the heat sink 1 well and to be easily removable and replaceable. Generally, the number and mounting position of fuses are determined appropriately,
A number of about 2 or 3 is sufficient.

On the other hand, power for the entire apparatus including the thermal recording head can be obtained by inserting the plug 11 into an outlet. The AC power from the plug 11 is supplied to various power circuits (not shown) after passing through a fuse 10 and relay contacts 6 and 7 in the power on/off control circuit 5. Therefore, if the relay contacts 6 and 7 are controlled to open not only when the power switch 4 is opened but also when at least one of the fuses 2 and 3 is blown, the intended purpose can be achieved. This is what will be achieved. In this example, as shown in the figure, the AC power supplied through the fuse 10 is stepped down by the transformer 9 and is then used as the excitation power source for the relay coil 8, so that the excitation control of the relay coil 8 is ultimately controlled. This is done by a power switch 4 and fuses 2 and 3 which are connected in series to a relay coil 8.

Under normal conditions, neither of the fuses 2 and 3 are blown, so closing the power switch 4 will energize the relay coil 8, which will close the relay contacts 6 and 7. Therefore, various power sources are supplied to the entire device. However, if the temperature of the thermal recording head and therefore of the heat sink 1 rises to a predetermined temperature for some reason in such a state, at least one of the fuses 2 and 3 will melt. be. If either fuse 2 or 3 blows, the relay coil 8 will be de-energized even if the power switch 4 is closed, and by opening the relay contacts 6 and 7, the thermal recording head will be Since the power is cut off instantly, the thermal recording head is reliably protected from abnormally high temperatures. This prevents fumes and abnormal odors from the recording paper and the like existing near the thermal recording head, as well as deformation of plastic parts and the like due to heat. Note that the excitation power source for the relay coil 8 may be a control DC power source, and the insertion positions of the relay contacts 6 and 7 are not limited to the illustrated positions.

As explained above, the present invention includes attaching a suitable number of fuses having predetermined fusing characteristics to a heat sink provided in a thermal recording head in a thermally coupled state, and when any one of the fuses blows out. The recording head is configured to at least cut off the power supply to the thermal recording head. Therefore, the present invention has the effect of simply and easily protecting the heat-sensitive recording head from abnormally high temperatures.

[Brief explanation of drawings]

The figure is a diagram showing a main circuit configuration in an example including a protection device according to the present invention. 1... Heat sink (equipped in the thermal recording head), 2, 3... Fuse, 4... Power switch, 5... Power on/off control circuit, 6, 7...
...Relay contact, 8...Relay coil, 9...(Step-down) transformer.

[Claims]

1 Platen bearings are inserted into both ends of a platen shaft inserted into the platen and rotatably hold the platen, and the platen bearing includes a chord surface part and a flange part cut out parallel to the platen axis direction, Two fixing ribs are formed on the outer periphery of the flange portion, and a side plate portion of the mechanism support body that supports the platen via the platen bearing has a platen bearing hole having a notch portion into which the chordal surface portion of the platen bearing is inserted. and a notch portion of a cantilevered structure that engages with the one fixing rib to stop the rotation of the platen bearing near the platen bearing hole, and a positioning rib that the other fixing rib abuts on the mechanism support. The platen support is characterized in that the free end of the notch part is deformable by operating with a finger or the like, and the deformation makes it possible to release the engagement between the one fixing rib and the notch part. Device.