JPS6395960A - Heat-sensitive printer - Google Patents

Abstract

(57) [Abstract] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to thermal printers, and more particularly to thermal printers having improved temperature control means and thus capable of high speed printing.

BACKGROUND OF THE INVENTION A thermal printer is a device that can print marks such as characters, bar codes, etc. on thermal printing media, such as thermal paper. Printing is accomplished by raising the temperature of the thermal paper above a threshold or conversion temperature at which the coating on the paper undergoes a chemical change and changes color. Typically, the temperature of the paper is increased using a thermal printing head that includes one or more resistive printing elements supported on a ceramic material and held in contact with the thermal paper. The shape of each printing element defines a portion of the character (or the entire character) that is printed.

It is important that thermal printers be able to precisely control the area of the thermal paper that is heated above the conversion temperature.

This control includes providing uniform pressure between the printing element and the thermal paper, controlling the exposure time or amount of heat applied to print each character portion, and keeping the printing element below the conversion temperature. This is accomplished by holding the thermal paper in place after each heat application until it cools down. Conventionally, uniform pressure between the printing element and the thermal paper is achieved by using a printhead support that rigidly supports the thermal printing head and a printhead support that is supported in opposing relation to the printing head and in contact with the thermal printing element. This was accomplished by providing a resilient and uniformly biased pressure member. Control of exposure and cooling times has been accomplished by electronic mechanisms such as those disclosed in US Pat. No. 4,391,535.

In a typical thermal printer, the printhead is supported by a printhead support that has the desired thermal capacity and is capable of transferring sufficient heat from the printhead to maintain the printhead at a reference temperature below the conversion temperature. be done. In the printing process, the thermal paper is moved to a desired position and stopped, and power is applied to the selected printing elements for a preset exposure time. The exposure time is sufficient to raise the temperature of only those areas of the thermal paper that are in uniform contact with the thermal printing elements from the reference temperature to the conversion temperature or above. After each power supply, the printhead supports 1~ rapidly cool the printhead and printing elements to a reference temperature. When the print head reaches the reference temperature, the thermal paper is moved to the position of the next character portion to be printed and the above process is repeated.

SUMMARY OF THE INVENTION A conversion cycle consists of a period of heating the printing element and then cooling the printing element below the conversion temperature. To obtain high printing speeds, this conversion cycle must be kept to a minimum. The electrical energy input to the thermal printing element during the heating cycle is dissipated in three areas: the energy required for the chemical heat exposure reaction, the energy lost in the thermal paper, and the energy lost through the print head. .

It has been found that approximately 80% of the input power is lost through the printhead, and this large amount of power must be handled by the heat transfer technology. Prior art techniques for removing heat from the print head and maintaining it at a reference temperature include
It includes free convection from the extended surface with air as the conducting medium and forced convection from the extended surface, also with air as the conducting medium. The above air conduction technology has been found to be effective in setting an upper limit on the printing speed of previous thermal printers.

A partial problem with air induction is that the temperature difference between the print element's surroundings is typically only 20°C, and the temperature gradient is insufficient to provide effective air cooling.

The present invention provides a thermal printer including heat pipe means thermally connected to a print head. In this configuration, the heat pipe means is incorporated within the printhead support assembly. With this arrangement, the heat pipe means thermally connects to the print head without compromising the rigidity and adjustability of the print head support. The heat pipe means thus serve to control the temperature of the print head without reducing the extent to which the printing elements can maintain uniform contact with the thermal paper.

In a preferred embodiment, the present invention provides a thermal printer that exposes a thermal print medium to heat to heat it and thus print on the thermal medium. A thermal printer consists of a print head that includes a metal part, a substrate in contact with the metal part, and a thermal printing element supported by the substrate. Means is provided for supporting the thermal printing medium in contact with the printing element. The thermal printer further includes heat pipe means having an evaporator section and a condenser section, the evaporator section being thermally connected to the metal section of the print head.

The means for supporting the thermal print medium preferably includes a drive roller, and the thermal printer includes print head support means for supporting the print head such that the printing elements contact the thermal print medium and the print head supports the thermal print medium. The print head is movable to a printing position that urges it into contact with the drive roller. The printhead support means includes means for resiliently biasing the printhead into a printing position. The heat pipe means includes a metal plate in contact with the evaporator section, the plate having a flat support surface supported by a corresponding flat surface of the metal section of the print head.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, the present invention provides a thermal printer for printing characters (including bar codes) on label stock consisting of a plurality of labels removably adhered to a longitudinal backing strip. is described in relation to One label L and associated backing strip S are shown in the position just taken from a thermal printer. The components of the illustrated printer in FIG. 1 include a printing mechanism 12, a feed reel 14, a pick reel 16, and a fan 18. Printing mechanism 12 includes a print head 20 and drive rollers 22 . During printing, label stock moves from feed reel 14 to printing mechanism 12 and passes between print head 20 and drive rollers 22. Thermal printing elements associated with a print head (described in more detail below) selectively supply heat to the label to print characters thereon. In the unwinding mode of operation, the label L and backing strip S exit the thermal printer through a slot 24 formed in the front side of the panel 26. In the self-peel mode of operation, each label L is partially peeled from the backing strip S by the peel bin 25 as the label stock exits the printing mechanism;
passes through and is wound onto the pick-up reel 16, and only the label exits from the slot 24. The delivery mode of operation is shown in FIG.

The components of the thermal printer shown in FIG.
, the rear panel 28 , the inner bulkhead 30 and the outer wall 32 . Printing mechanism 12 is supported between partition wall 30 and exterior wall 32. The feed reel 14 and the pick-up reel 16 are supported only by the bulkhead 30. A fan 18 is formed within and supported by rear panel 28.

Feed reel 14 includes a shaft 34, a guide bin 36, a shoulder 38 and a bar 40. Shaft 34 and guide
Bin 3G extends laterally from shoulder 38 supported on bulkhead 30. A roll 42 of label strips 1 to 4 is supported on shaft 34 in an orientation to permit strip 44 to be unwound from the roll 42 from the top of the roll.

Roll 42 is attached to shaft 34 by shoulder 38 and bar 40.
constrained laterally at the top. Bar 40 is retained on shaft 34 and bin 36 by engagement between a circumferential groove on the shaft and guide bin and a downward facing slot in the bar. The shaft and guide bin each include a series of said grooves so that the bar 40 can be adjusted laterally relative to the shoulder 38;
It can be adapted to rolls of different widths.

Printing mechanism 12 is shown in more detail in FIGS. 2 and 3.

The printing mechanism includes the printhead 20 and drive roller 22 described above, between which a strip of label stock 44 passes. A drive roller is connected to a suitable source of rotational motion. The outer surface of the drive roller includes a resilient covering ring 23 that provides a frictional engagement between the drive roller and the strip 44. The strip 44 is connected to the guide plate 45 and the guide plate 45.
It is guided to the drive roller 22 by means including a bin 46 and a conventional tensioning mechanism 47.

The print head 20 includes a metal plate 50. It includes a ceramic substrate 52, a cover 54, and an electrical connector 56.

A plurality of thermal printing elements 48 are formed on the underside of substrate 52 at a location where the substrate is directly above and against drive roller 22 . A cover 54 is supported on the underside of the substrate 52 and surrounds printing element control circuitry 58 formed therein. The cover 54 includes a pair of screws 60 and a pair of spacers 6.
1 (only one spacer is shown) on the plate 50. Electrical signals for the control actions of print element control circuit 58 are provided via a ribbon cable 62 that passes through an opening 64 in septum 30. cable 62
terminates in an electrical connector 66 that matches the connector 56 that connects to the print element control circuitry.

Plays 1-50 are supported by a support assembly 70 which also functions to remove heat from the printhead, thus maintaining the printhead at a suitable reference temperature. Support assembly 70 includes heat pipe assembly 72, support blocks 74, 76, bracket 78 and shaft 80.
including. Shaft 80 is supported between bulkhead 30 and exterior wall 32. Bracket 78 has end portions 82,84 each containing a vertical slot 86,88 through which shaft 80 passes.
including. The end portions 82.84 also each have an overhang tab 90.
Contains 92. Tabs 90.92 are nuts 98.100 respectively
are used to support screws 94 and 96, respectively, which are tightened into position by screws 94 and 96, respectively. The lower ends of the screws 94, 96 contact the shaft 80, and the central portion of the shaft 80 contacts and is supported by a cylindrical projection 102 formed in the center of the bracket 78.

Thus, the screws 94,96 and the projections 102 support the bracket 78 for pivoting movement about the shaft 80.

Furthermore, by adjusting the position of screws 94 and 96, the bracket (
Therefore, the horizontal orientation (of the printing element) can be precisely controlled;
Uniform contact between the printing element and the label L can be guaranteed.

Heat pipe assembly 72 includes heat pipe 110. 112
and plate 114. Heat pipe 110. 1
12 is an evaporator portion 116. 118 and capacitor portion 120. 122 respectively. The evaporator section 116° 118 is in the form of a flat tube, and the plate 114
firmly held on the upper surface of the Plate 114 thermally connects the evaporator section to plate 50 of print head 20 while minimizing lateral thermal gradients within the print head that result in lateral print variations. Capacitor part 120
．． 122 each include a bundle of heat fins spaced parallel to each other. The heat pipes are spaced apart from each other and the condenser section 12
0. A small gap exists between 122 and 122. Fan 18 (
1) is supported at approximately the same level as the condenser sections 120, 122 to allow air to flow through the condenser sections to enhance the cooling effect.

The heat pipe assembly is supported by brackets 78 via support blocks 74,76. The lower front surface of plate 114 includes a downwardly projecting step 124 on which plate 50 is retained. The rear end of the plate 114 has a spring 126. 128 from the bar 130.

Meanwhile, the bar 130 is supported between the partition wall 30 and the outer wall 32. The spring tends to rotate support assembly 70 counterclockwise about shaft 80, thus biasing the print head downwardly into the printing position shown in FIG. 2, where the printing elements contact strip 44 and print. The head resiliently biases the strip 44 against the drive roller 22. This configuration ensures the desired degree of pressure of the printing elements on the label and of the slips 1-44 on the drive roller 22. Roll 42 of label stock (first
) is first loaded into a thermal printer, the support assembly 70 and the print head 20 are able to rotate clockwise relative to each other against the force of the springs 126, 128, creating a gap between the print head and the drive roller. strip 44
Allows you to insert .

It can be seen from the above description that the heat pipe means form an integral part of the support assembly 70.

According to this configuration, the heat pipe means is in intimate thermal contact with the print head without compromising the rigidity and adjustability of the print head provided by the support assembly. functions to control printhead temperature without reducing the extent to which the printing elements can maintain uniform contact with the thermal print media.

Although the preferred embodiments of the invention have been illustrated and described, those skilled in the art will recognize that various modifications may be made thereto. Therefore, the invention is not limited to the particular embodiments illustrated and described, but rather is determined by the scope of the appended claims.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway perspective view of a thermal printer according to the present invention, FIG. 2 is a side view showing a printing mechanism of the thermal printer of FIG. 1, and FIG. 3 is an exploded perspective view of the printing mechanism.

Claims (4)

[Claims] (1) A thermal printer that heats a thermal printing medium by exposing it to heat and thus prints on the thermal printing medium, the printer comprising a metal part having a flat surface, a substrate in contact with the metal part, and a support on the substrate. a printhead comprising: a thermal printing element configured to contact the thermal printing medium; a means for supporting the thermal printing medium in contact with the printing element; an evaporator portion; A thermal printer comprising: a heat pipe assembly including a metal plate and a capacitor portion, the metal plate being supported on a flat surface of the metal portion of the printhead. (2) the means for supporting the thermal print media includes rollers, and the thermal printer further includes support means for supporting a heat pipe assembly and a printhead;
The print head and heat pipe assembly are movable as a unit relative to the printing position, where the printing elements contact the thermal print medium and the print head urges the thermal print medium into contact with the rollers. A thermal printer according to claim (1). (3) The support means includes means for resiliently biasing the heat pipe assembly in a predetermined direction and thus resiliently biasing the print head toward the printing position. Thermal printers listed in section. (4) The support means includes a shaft and bracket means supported on the shaft for pivoting movement about the shaft, wherein the metal plate of the heat pipe assembly is supported on the bracket means. The thermal printer described in (3).