JPS592624B2 - thermal recording printing unit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermal recording printing unit that produces visible dots on a heat-sensitive recording medium in response to input electrical pulses, and in particular to a thermal recording printing unit that produces visible dots on a heat-sensitive recording medium in response to input electrical pulses, and in particular, the invention relates to a thermal recording printing unit that produces visible dots on a heat-sensitive recording medium in response to input electrical pulses, and in particular to a thermal recording printing unit that produces visible dots on a heat-sensitive recording medium in response to input electrical pulses. , relates to a thermal recording type printing unit equipped with a print head having a printing surface formed on the terminal end face of the tapered corner.

In conventional thermal dot printers, 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 printers, if there is no relative movement between the recording medium and the print head during printing, there is no 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. Furthermore, the cooling time of the printing head that is heated during printing is relatively long, which limits high-speed printing. The object of the present invention is to provide a thermal recording printing unit which does not have the above-mentioned disadvantages and which ensures clear and undistorted printing.

To achieve this object, according to the invention, the printing unit comprises a printing head which is tapered at one end and forms a printing surface on the terminal end face of the tapered section, the printing surface being substantially rectangular in shape. , the long sides of this rectangle are arranged in a direction perpendicular to the direction of movement of the recording medium, so that a square dot is printed on the recording medium as a result of relative movement between the recording medium and the printing surface during printing. Means is provided for synchronizing the printing time and the relative movement speed.

Due to this structure, the printing surface (dot) is formed on the terminal end face of the tapered part b of the printing element, so the density of the current applied to the printing element increases rapidly as it reaches the printing surface. By rapidly heating up and cutting off the current supply, the printing surface cools quickly, thus allowing high speed printing.

Further, the printing surface has a rectangular shape, the long side of which is perpendicular to the traveling direction of the recording medium, and the short side thereof facing parallel to the traveling direction of the recording medium, so that the printing time of the hexagram D and the moving speed of the recording medium can be appropriately synchronized. Because of this, the printed dots are square, resulting in clear and consistent printing, which can be used for flying printing. Note that the printing surface is held in close contact with one surface of a thin conductive sheet, while the recording medium is moved over the other surface of the sheet.

The printing element is held in proper contact with the sheet by a novel spring arrangement. FIG. 1 shows one of the heating elements (printing elements) 1 of the invention used to generate the heat necessary to change the color of temperature recording 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 tapered part 2 which increases the current density at the end face 3, thereby limiting the heating point to a relatively small part of the element and facilitating rapid cooling of the end face. do. The shape of the terminal end face 3 is not square but rectangular (for example, 2×50 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 color change when the band 10 is heated in 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 network 27 is an ordinary read-only memory (hereinafter referred to as
20 (referred to as ROM) and printing heads 28, these heads are in contact with a grounded metal band. R
OM2O has many common input methods (computer,
The character code to be printed is supplied by any one of the bookkeeping machines, etc., the direction of which is indicated by the arrow to the left of ROM 2O. The circuitry for triggering drive network 27 does not form part of the present invention, and the description of this drive network in this specification is provided to disclose the mode to which the present invention is intended to utilize.

The characters supplied to ROM2O consist of parallel 6-bit codes. ROM 2O converts this code into a code corresponding to display according to a 5.times.7 bit matrix.

Further, the ROM 2O outputs character strings (COlvnn) according to the 5×7 type (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 (FIG. 1) in the print head. These output leads terminate in an electrode plate 5 drive network 27 which includes individual energizing 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.
Energizing circuit 26 for operating the printing unit of the invention
The details of one example are shown in FIG.

All seven energizing circuits 26 share a stable voltage generator 41 and a long term compensation network 40 (these 41.40 are not shown in FIG. 5).

Long term compensation circuit 40 (this consists of resistor 42 and capacitor 4
3) is connected to transistor 44.
Transistor 44 is connected to transistor 44 via resistor 46.
Connect to? Switching is performed by a dot command signal from the ROM 2O. The output of transistor 44 is connected to a short-term compensation network 47, which is connected to ground via resistor 5L52. Short-term compensation network 47 includes resistors 48, 49 and capacitor 50. Power stage 54 is a conventional amplifier that receives the output of network 47, appropriately amplifies the received output, and then provides the amplified output to the printing element via resistor 58. This power amplification stage 54 includes an n-p-n type transistor 5 connected as a cathode follower.
5 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 unit 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 energizing circuit 2 in FIG.
6) 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. Short-term compensation network 47 ensures that individual printing elements 28 (FIG. 5) do 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, 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 shorter elapsed time between the two pulses. From the above arrangement, it can be seen that the amount of energizing current passing through amplifier 54 depends on the energizing frequency of the print head as a whole and the individual printing elements. FIG. 7 shows an actual printing unit according to the invention, including a housing 61 and a support plate 62, on which a printed circuit 63 consisting of seven conductive paths is provided.
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.

Resistive element 64 is aligned such that termination end faces 65 lie in the same plane and is embedded within an insulating plastic block except for termination end faces 65.

FIG. 8 shows another embodiment of a thermal recording printhead comprising a rigid housing made of three elements 71, 72, 73. The element 71 consists of an insulating body, one side of which has a groove and the opposite side a flat projection of the same size as the groove.

Element 72 consists of an insulating body of the same size as element 71 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. Element 73 with good thermal conductivity can accommodate metal bands J and V in its group 76. The group of elements 71 , 72 and the group of projections 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 7S. 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 printing head (FIG. 2) are such as to accommodate the operation of the unit.

Thickness 0.2m, width 1.5mm, length 15mw! Good results have been obtained by using a graphite resistive element having dimensions of 1.0 and 90.degree. The edges of this V-shaped end should be beveled and the printing surface (terminating end face) should be flat and have an area of 0.01 md. For a printing speed of 200 characters per minute, the required thermal power should be 8 Watts for 0.3 milliseconds, and this power should be 2.5 Am for 0.3 milliseconds.
given by a current pulse of p. This power has a thickness of 20
Produces good printing on thermal paper through micron steel metal band.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of one embodiment of the printing head of the printing unit of the present invention. FIG. 2 is a perspective view of a group of resistive elements insulated 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 a paper feeding device used in the present invention. FIG. 5 is a block diagram of the system used to drive the print head. FIG. 6 is a block diagram of the operating circuit of the printing element used in the unit of the invention. FIG. 7 shows an embodiment of the thermal recording printing unit of the present invention having convergent resistive elements. FIG. 8 shows another embodiment of a printing unit with convergent resistive elements.
1: heating element, 2: tapered portion, 3. End end surface, 10: metal band, 12: spring, 28: printing head, 36: paper,
65: terminal part, 67: spring, 71, 72, 73: element,
7JMeF metal band, 78: Resistance element, 80: Spring.

Claims (1)

[Scope of Claims] 1. A thermal recording printing unit comprising a plurality of printing elements arranged side by side in a row and each connected to an electrical energy source, one end surface of each printing element being connected to an electrical energy source. said thermal recording printing unit comprising a printing surface, the printing surfaces of each of said printing elements being located in a common plane, each said printing element comprising a substantially rectangular plate of resistive material; one end of the plate-shaped body is tapered, the printed surface is formed on the tip end face of the tapered part, and a conductor for supplying electrical energy is connected to the other end of the plate-shaped body,
a conductor band disposed in contact with the printed surface of the printing element, an electrical circuit for passing an electric current from the conductor to the conductor band through the resistive material body; forming a substantially rectangular shape, each printing element being arranged such that the long side of the rectangle is perpendicular to the direction of relative movement between the printing unit and the thermal paper, and the rectangular shaped printing surface of each printing element an electrical circuit is provided for synchronizing the speed of the relative movement between the printing unit and the thermal paper and the operating time of each printing element to cause the printing of substantially square dots on the thermal paper during each printing operation; A thermal recording type printing unit characterized in that printing is performed by bringing the thermal paper into contact with the printing surface with the conductor band sandwiched therebetween. 2. The thermal recording printing unit according to claim 1, further comprising a spring that holds each of the printing elements in contact with the conductor band.