JPS5820797B2 - Japanese crested beetle - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to non-impact printing units, and more particularly to thermal recording printing units that produce visible dots on a heat-sensitive recording medium in response to input electrical pulses.

a plurality of thermal printing elements connected to a common voltage source and adapted to be individually heated for predetermined times during a printing operation; and an actuating unit for individually heating the thermal printing elements. In a thermal recording type printing unit equipped with a thermal recording type printing unit, there is a problem in that the density of dots formed on thermal paper becomes uneven due to differences in the frequency of use between individual printing elements or fluctuations in the usage rate of the entire printing element over time. There is.

It is therefore an object of the present invention to provide a thermal recording printing unit which does not have the above-mentioned drawbacks and ensures uniform printing.

To achieve this objective, according to the invention a circuit with a long-term compensation network and a short-term compensation network is used.

The long-term compensation network adjusts the electrical energy for heating the printing elements according to the utilization of the entire printing element rather than the individual thermal printing elements, and is charged by the voltage source mentioned above and supplies electrical energy to the operating unit mentioned above. It has a capacitor to supply it.

If the energy delivered to the printing elements through the actuating unit when the total printing element usage is high is the same as the energy delivered to the printing elements when the usage is low, the printing elements will overheat.

When the usage rate of all printed elements is high for the above capacitor,
Because its stored charge is less, relatively less electrical energy is supplied to the printing element.

Overheating is therefore prevented and the formation of too dark dots is also prevented.

On the other hand, the short-term compensation network is for each thermal printing element and has the function of adjusting the electrical energy to be supplied depending on the frequency of use of each thermal printing element.

This short-term compensation network is provided within the individual operating units,
It is connected to the long term compensation network via a switch.

The short-term compensation network has a second capacitor connected in parallel with the resistor.

Therefore, if a dot command pulse is input to the switch when the thermal printing element is used infrequently, the electrical energy from the long-term compensation network will short-circuit the second capacitor of the short-term compensation network, resulting in a relatively large amount of electrical energy. A pulse is provided to the printing element.

However, when the thermal printing element is used more frequently, the second capacitor is constantly charged, so the electrical pulse from the long-term compensation network cannot pass through the second capacitor, but is attenuated because it passes through the resistor. , relatively small pulses of electrical energy are provided to the printing element.

As a result, dots with uniform density can be formed regardless of the frequency of use of individual thermal printing elements.

The invention will now be described in detail with reference to the drawings. FIG. 1 shows one of the printing elements 1 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 taper 2 which increases the current density at the end face 3, thereby confining the heating to a relatively small part of the element and facilitating rapid cooling of the end face.

The shape of the terminal end face 3 is not square but rectangular (for example, 2
M x 50 microns).

The fact that the length of the end face is greater than its width means that instead of the elongated marking that would occur if the end face were square or circular (due to the effects of the relative movement of the recording paper and the printing unit), Flying printing (printing where the paper does not stop between each printing motion) which produces a square marking (commonly called a single dot)
is allowed to be used.

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 terminal 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 printing elements is placed in a cavity 9 of a container 8 and a spring 1
2 presses the printing element 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 within 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 printing elements.

, a drive roller 37 and a corresponding roller 38 pull the paper 36 through a drum 39. Below the drum 39 there is a print head, between the print head and the drum 39 there is a band 10 (third
figure.

(not shown in Figure 4).

FIG. 5 shows a typical print element actuation mechanism for print head 28. FIG.

A print element activation network 27 is connected between a conventional read-only memory (hereinafter referred to as ROM) 20 and print heads 28, which contacts a grounded metal band.

The ROM 20 has many common input means (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 the ROM 20.

The characters supplied to the ROM 20 consist of parallel 6-bit codes, and the R,0M 20 converts this code into a code corresponding to display according to a 5.times.7 dot matrix.

Further, the ROM 20 is configured to read characters (colu-mn) according to a 5x7 format via a trigger circuit 22.
) to control continuous printing.

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 in R. K. Richard, "Digital Computer", page 205).

Each bit softs in ring counter 24 to energize each of the five output channels.

These channels are connected to gate 29.

The seventh stage of the ring counter 24 is the oscillator 23
It is connected to a stop circuit 30 connected to.

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 (consisting of a monostable multi-by-break), which controls the period of activation of the gate 29.

The output of the R,0M20 consists of seven output leads corresponding to the number of resistive or heating elements (FIG. 1) in the printhead.

These output leads terminate in a print element activation 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 energizing circuit 26 is connected to a printing device having a head 28 consisting of a printing element 1 in contact with a metal band 10 (FIG. 3).

According to the present invention, a circuit for forming uniform marking points is provided in the sixth embodiment.
This will be explained with reference to the figures.

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). ) is connected to transistor 44 .

Transistor 44 is connected to transistor 44 via resistor 46.
Switching is performed by a dot command signal from the ROM 20 connected to the ROM 20.

The output of transistor 44 is connected to a short-term compensation network 47, which is connected to ground via resistors 51,52.

Short-term compensation network 47 includes resistors 48, 49 and capacitors 50.

The power stage 54 is an ordinary amplifier that receives the output of the network 47, and after properly amplifying the received output, the power stage 54 is connected to the resistor 58.
provides the amplified output to the printing element via.

The power amplification stage 54 includes an n-p-n transistor 55 connected as a cathode follower, and a pair of Darlington-connected transistors 56 .
57.

The printing element is subjected to continuous heating and cooling cycles during operation.

If the same element is pulsed rapidly and continuously, the element will not be given sufficient time to cool down.

This results in a gradual overheating of the element.
This results in an increase in the density of printed dots.

For uniform printing, the energizing current supplied to the printing element should be decreased while the energizing frequency (the frequency at which the printing element operates) increases.

According to the invention, two compensation networks are provided which gradually reduce the energization current as the energization frequency increases.

FIG. 6 shows a long-term compensation network 40 and a short-term compensation network 47.

As mentioned above, the generator 41 and the compensation network 40 are connected to the entire auxiliary network 2.
6 (FIG. 5) is used continuously, all print heads (i.e., all of the heads 28 in FIG. 5) become overheated.

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 the printing elements are not activated suddenly, the capacitor 43 of the network 40 has time to fully charge.

In this state, when transistor 44 is made conductive by R,0M20, a large pulse passes through transistor 44.

However, within a short time, transistor 44 (or
If any one of the illustrated energization circuits 26 were to be energized again, a somewhat weaker pulse than the previous one would be applied to the transistor 44.
pass through.

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 resistor 49,48 and returns to normal state after a short time.

However, if a second pulse passes through transistor 44 before capacitor 50 has a chance to discharge, the magnitude of this pulse will be an amount corresponding to the shortness of the elapsed time between the two pulses. only decreases.

From the above arrangement, it can be seen that the amount of energizing current passed through amplifier 54 depends on the energizing frequency of the overall printhead and the individual printing elements.

FIG. 7 shows an actual printing unit including a housing 61 and a support plate 62, on which a printed circuit 63 consisting of seven conductive paths is provided (on one side of this printed circuit there are four paths, There are three paths on the curved surface).

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.

The resistive or printed element 64 is aligned such that the terminal end faces 65 are in the same plane and is embedded within a block of insulating plastic except for the terminal end faces 65.

FIG. 8 shows an alternative configuration 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 this groove.

Element 72 consists of an insulating body of the same dimensions as element T1 and is provided with corresponding grooves and protrusions so that one element can accommodate the protrusion of the other element.
It has a protrusion 74 that can fit into the groove 75.

The thermally conductive element 13 can accommodate a metal band 77 within its group 76 .

The groups of elements 71 and 72 and the groups of protrusions 74 are 7
It accommodates two 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 metal band 77.

This spring is placed in a group of elements 71 with a clamp T
Placed within 9.

It is not necessary for the elements 78 to maintain firm contact with the metal band to avoid creating contact resistance between these elements and the band.

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 it is difficult to control contact resistance.

The dimensions of the print head (FIG. 2) are such as to accommodate the operation of the unit.

Good results are obtained by using a graphite resistive element with dimensions of 0.2 m thick, 1.5 m wide and 15 m long, with V-shaped ends bent at an angle of 90°. .

The edges of this V-shaped end should be beveled and the printing surface should be flat and have an area of 0.01 M2.

The thermal power required for a printing speed of 200 characters per minute is 0.
3mi! There should be 8 watts per J second, and this power is provided by a 25 Amp current pulse lasting 0.3 milJ seconds.

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 a print head of a thermal recording printing unit. FIG. 2 is a perspective view of a group of printing elements insulated from each other and embedded within a block of insulating epoxy plastic. FIG. 3 is a perspective view of a hollow parallelepiped-shaped support for a printing blank. 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 printhead. FIG. 6 is a block diagram of an operating circuit of a printing element according to the present invention. FIG. 7 is a diagram showing an example of a configuration of a thermal recording type print head having convergent resistive elements. FIG. 8 is a diagram illustrating another configuration of a print head having convergent resistive elements. In FIG. 6, 40: long-term compensation network, 43: capacitor, 48: resistor, 47: short-term compensation network, 50: second capacitor.

Claims (1)

[Scope of Claims] 1. A plurality of thermal printing elements connected to a common voltage source and adapted to be individually heated for predetermined times during a printing operation; and an actuating unit for heating, the printing unit having a long-term compensation network, the long-term compensation network being charged by the voltage source and supplying energy to the actuating unit. a capacitor for supplying current, while the actuating unit has a short-term compensation network including a resistor connected in parallel with a second capacitor, the long-term compensation network and the short-term compensation network being connected to a switch. A printing unit characterized in that it is connected.