JPS592625B2 - thermal recording printing machine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a thermal recording print head that prints visible dots on a heat-sensitive recording medium in response to input electric pulses, a support that supports the recording medium, and a printing The present invention relates to a thermal recording printing machine comprising means for relative movement of a recording medium and a print head during operation.

In particular, the invention provides that the print head comprises a plurality of printing elements that are individually energized during each printing operation to print individual print dots on the recording medium, each printing element having a rectangular printing surface. Regarding printing presses. In conventional thermal recording printing machines, the printing dots forming the printing surface of the printing element are provided on a support plate, and the printing surface has a circular or square shape.

In such conventional printing machines, if the printing is such that there is no relative movement between the recording medium and the print head during printing, there is a problem because the printing dots print circular or square dots on the recording medium. However, in the case of fly fern printing where the recording medium does not stop after each printing operation, oval or rectangular dots are printed on the recording medium due to relative movement between the recording medium and the printed dots. ,
The disadvantages were that the printed characters were unclear and the shapes of the letters were distorted. The object of the present invention is to provide a thermal recording printing machine which does not have the above-mentioned drawbacks and which ensures clear and undistorted printing.

To achieve this objective, according to the invention, the printing head of a printing press consists of a plurality of printing elements connected to a source of electrical energy and individually activated for a predetermined time during each printing operation, each of which The printing element has end faces constituting printing surfaces that are heated during activation and are located adjacent to a common electrode, each printing surface having a rectangular shape, the long sides of which are connected to the recording medium and the printing head. located perpendicularly to the direction of relative movement with the short side parallel to the direction of relative movement,
The active time of the printing elements and the relative movement are synchronized to print square dots on the recording medium with a rectangular printing surface.

Because of this configuration, if the printing machine of the present invention is used, it is possible to print clearly and without any distortion of characters.

FIG. 1 shows one of the heating elements (printing elements) 1 used to generate the heat necessary to change the color of thermal paper (not shown).

These elements are made of resistive material so that they heat up in response to the electric current. The element has a taper 2 which increases the current density at the end face 3, thereby confining the heating point to a relatively small part of the element and facilitating rapid dissolution of the end face. . The shape of the terminal end face 3 is not square but rectangular (for example, 2wn x 50 microns). The fact that the length of the end face is greater than its width means that instead of an elongated marking as would occur if the end face were square and circular (due to the effect of the relative movement of the recording paper and the head). , square marking (
Allows the use of flying printing (printing where the paper does not stop for each printing operation) which results in printing (commonly referred to as "dots"). As shown in FIG. 2, the elements 1 have different lengths to allow electrical connections 6 to the conductive portions 4. The elements are wrapped in an insulating material (eg, plastic) and separated from each other by thin insulating sheets. The end face is not enclosed by a plastic case 7, so that it can make electrical contact with the metal band 10 (FIG. 3).

A group of printed elements or electrode plates is placed in the cavity 9 of the container 8, and a spring 12 presses the electrode plates against the metal band 10. The paper is passed over the outer surface of the band 10 and the paper undergoes a corresponding change when the band 10 is heated within the isolated area.
The plastic case 7 is held in the cavity by a rod 13 which holds the block 11 in place. FIG. 4 shows a simplified roller arrangement for driving thermal paper 36 past the writing electrode plate.

Drive roller 37 and corresponding roller 38 pull paper 36 through drum 39. There is a printing head below the drum 39, and between the printing head and the drum 39 there is a band 10 (third
figure. (not shown in Figure 4). FIG. 5 shows a typical electrode plate drive mechanism for print head 28.

The electrode plate drive line 27 is an ordinary read-only memory (hereinafter referred to as
20 (referred to as ROM) and a printing head 28, which contacts a grounded metal band.
ROM 2O is supplied with the character code to be printed by any one of a number of common manual means (computer, bookkeeping machine, etc.), the method of supply being indicated by the arrow to the left of ROM 2O. The circuitry for triggering drive network 27 does not form part of the invention, and the description of this drive network in this specification is provided to disclose the mode to which the invention is intended to utilize.

The characters supplied to ROM2O consist of parallel 6-bit codes, which ROM2O converts into codes corresponding to display according to a 5.times.7 dot matrix.

Further, the ROM 2O outputs character columns (COlumn) according to the 5×7 format (FOrmat) via the trigger circuit 22.
controlled by a channel for controlling the continuous printing of.

These channels represent the output of scanning network 21. Trigger circuit 22 activates oscillator 23.

The output pulses of the oscillator are fed to a ring counter 24 consisting of seven bistable elements (this counter is of the type described on page 205 of "Digital Computers" by R. K. Richert). Each bit is shifted through ring counter 24 to energize each of the five output channels. These channels are connected to gate 29. The seventh stage of ring counter 24 is connected to a stop circuit 30 which is connected to oscillator 23 . The stop circuit 30 stops the oscillator 23 in response to the output signal of the seventh bistable element. The oscillator 23 is also connected to a regulating circuit 25 (which consists of a monostable multivibrator), which controls the period of activation of the gate 29.

The output of ROM 2O consists of seven output leads corresponding to the number of resistive or heating elements 1 (FIG. 1) in the print head. These output leads terminate in electrode plate drive network 27, which includes individual energization circuits 26.

Energization circuit 26 amplifies the power of the signal to a magnitude sufficient to print the signal on the paper during the printing operation. Each auxiliary circuit 2
6 is a resistance element 1 in contact with a metal band 10 (FIG. 3)
It is connected to a printing device having a head 28 consisting of.
The details of one example of the energizing circuit 3 for operating the printing press of the present invention are shown in FIG.

All seven energizing circuits 26 share a stable voltage generator 41 and a long term compensation network (41, 40 not shown in FIG. 5).

Long term compensation circuit 40 (this consists of resistor 42 and capacitor 4
3 and 3) are connected to transistors 4 and 4. Transistor 44 is connected to transistor 4 via resistor 46.
Switching is performed by a dot command signal from ROM 2O connected to 4. The output of transistor 44 is connected to a short-term compensation network 47 which is connected to ground via resistors 51 and 52. Short-term compensation network 47 has resistors 48 and 49
and a capacitor 50. The power stage 54 is the net 4
7, and after suitably amplifying the received output, provides the amplified output to the printing element via a resistor 58. The power amplification stage 54 includes an npn transistor 55 connected as a cathode follower and is controlled by a pair of Darlington connected transistors 56 and 57. The printing element is subjected to continuous heating and cooling cycles during operation.

If the same element is rapidly and continuously pulsed, it will not be given sufficient time to cool down. This results in a gradual overheating of the element, resulting in an increase in the density of the printed dots. To achieve uniform printing, the energizing current supplied to the printing element should be decreased as the energizing frequency (the frequency of use of the printing element) increases. For operation of the printing press of the invention, two compensation networks are provided which gradually reduce the energizing current as the energizing frequency increases.

FIG. 6 shows a long-term compensation network 40 and a short-term compensation network 47. As already mentioned, the generator 41 and the compensation network 40 are common to all auxiliary networks 26 (FIG. 5). When the printing press is used continuously, all printing heads (i.e. head 2 in FIG.
8) will start to overheat. To prevent this, a long term compensation network 40 is used to reduce the energizing current. If the printing press is not in use or if the printing elements are not activated rapidly, the capacitors 43 of the network 40 have time to fully charge. In this state, when transistor 44 is made conductive by ROM2O, a large pulse passes through transistor 44. However, within a short time, transistor 44 (or auxiliary circuit 3 in FIG.
) is re-energized, a somewhat weaker pulse than the previous one passes through transistor 44. The reason is that capacitor 43 has not been given time to fully recharge. This compensation network 40 ensures that all printing units do not overheat due to rapid printing operations. The short-term compensation network 47 is connected to the individual printing elements 2
8 (Figure 5) to ensure that it does not overheat.
The first pulse through transistor 44 passes through capacitor 50 as if it were a short circuit. However, the pulse charges capacitor 50. This capacitor immediately begins to discharge through resistors 49 and 48 and returns to normal state after a short time. However, if the second pulse passes through transistor 44 before capacitor 50 has a chance to discharge, then
The magnitude of this pulse is reduced by an amount corresponding to the shortness of the elapsed time between the two pulses. From the above configuration, amplifier 5
It can be seen that the amount of energizing current passed through 4 depends on the energizing frequency of the print head as a whole and the individual printing elements. FIG. 7 shows an actual printing head of a printing press according to the invention, comprising a housing 61 and a support plate 62, on which a printed circuit 8 consisting of seven conductive paths (
There are four paths on one side of this printed circuit and three paths on the other side).

Seven elongated flat resistive elements 64 are present perpendicular to the plane of the support plate 62.

The end portion of each resistive element is coated with a thin layer of copper and welded to a corresponding conductive path. A terminal end face 65 of the tapered portion of each resistive element 64 is substantially flat and is held firmly in contact with band 66 by the action of spring 67. Resistance element 6
4 are aligned so that the terminal end faces 65 lie in the same plane and are embedded in an insulating plastic block except for the terminal end faces 65.

FIG. 8 shows another embodiment of the thermal recording printing head of the printing press of the present invention, which includes a rigid housing made of three elements 71, 72, 73. The element 71 consists of an insulating body,
One side of the body has a groove and the opposite side has a flat projection of the same size as the groove.

Element 72 consists of an insulating body of the same dimensions as element T1 and has corresponding grooves and projections so that one element can accommodate the projections of the other element. Element 72 is element 7
It has a protrusion 74 that can fit into the groove 75 of No. 3. The element 73 with good thermal conductivity can accommodate the metal band n in its groove 76. The grooves of elements 71, 72 and the grooves of protrusion 74 accommodate seven flat resistive elements 78.

An insulating plate 81 is placed between the exposed edge of element 78 and the wall of groove 75 of element 73. Spring 80 ensures that each individual element 78 remains in firm contact with the metal band.
This spring is placed in the groove of the element 71 in the clamp 7
Placed within 9. It is important that the elements 78 remain in firm contact with the metal bands to avoid creating contact resistance between these elements and the bands.

It is the electrical resistance of element 78 that determines the heat generated, not the contact resistance between element 78 and the band. This is important because contact resistance is difficult to control. The dimensions of the print head (Fig. 2) are 0.2 mm thick.
Good results are obtained by using a graphite resistor element having dimensions of Tfr1n1 width 1.5 m and length 15 m, and having a V-shaped end bent at an angle of 901 degrees.

The edges of this V-shaped end should be beveled and the printing surface (terminal end face) should be flat and have an area of 0.01 Tfrit. For a printing speed of 200 characters per minute, the required thermal power should be 8 watts for 0.3 milliseconds, and this power is provided by a 2.5 Amp current pulse lasting 0.3 milliseconds. This power produces good printing on thermal paper through a 20 micron thick steel metal band.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an embodiment of a portion of a printing head of a printing press according to the invention. FIG. 2 is a perspective view of two groups of resistive elements isolated from each other and embedded within an insulating epoxy plastic block. FIG. 3 is a perspective view of a hollow parallelepiped support for a printing block. FIG. 4 is a simplified perspective view of the paper supply device. FIG. 5 is a block diagram of the system used to drive the printing head of the printing press of the present invention. FIG. 6 is a block diagram of the operating circuit of the printing element. FIG. 7 shows an embodiment of a thermal recording printing head of a printing press according to the invention having convergent resistive elements. FIG. 8 shows another embodiment of a print head with convergent resistive elements. DESCRIPTION OF SYMBOLS 1...Heating element, 2...Tapered part, 3...Terminal end face, 10...Metal band, 12...Spring, 26 ... Energizing circuit, 28 ... Printing head, 36 ... Paper, 65 ... Termination section,
67... Spring, 71, 72, 73...
Element, 77...Metal band, 78...
Resistance element, 80... Spring.

Claims (1)

[Claims] 1 a printing head having a plurality of printing elements arranged in a row and connected to a source of electrical energy and individually selectively activated for a predetermined time during each printing operation; and a thermal sensitive material to be printed by this printing head. a support 39 for supporting a heat-sensitive paper; and a device 3 for continuously moving the heat-sensitive paper in a predetermined direction relative to the print head during each printing operation;
7 and 38, each of said printed elements comprising a member of a resistive material connected at one end to a conductor constituting an electrode connected to a source of electrical energy and having a printed surface at the other end, each of said printed elements having a common is in contact with a conductive band constituting a counter electrode of said printed surface, said printed surface exhibiting a substantially rectangular shape, the long sides of said rectangle oriented substantially perpendicular to said direction of said relative movement; A thermal recording printing machine characterized in that it is provided with an electrical circuit for synchronizing the speed of movement and the operating time of each printing element to print substantially square dots on heat-sensitive paper.