Thermal printing apparatus

Details Thermal printing apparatus Thermal printing apparatus

1999-02-23

2001-05-29

Le, N. (Department: 2861)

Incremental printing of symbolic information

Thermal marking apparatus or processes

Recording means engaging or holding means

C400S056000

Reexamination Certificate

active

06239825

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a thermal printing apparatus having a thermal head which is disposed at right angles to, and is arranged to be movable towards and away from, a medium which is to be printed while it is transported or fed in a predetermined feeding direction. It relates, in particular, to a thermal printing apparatus which is capable of printing on different thicknesses of media to be printed.
2. Description of the Related Art
There has conventionally been known a card printer, as a thermal printing apparatus, which has a thermal head movable towards and away from a medium to be printed while it is transported or fed in a predetermined feeding direction of the medium. In a thermal head of this thermal printing apparatus the heating elements are arranged at right angles to the direction of transporting the medium.
The card printer is a printing device for printing exclusively on a rigid card which is as thick as about 1 mm. On the other hand, the thermal printing apparatus is for printing characters, or the like, on different kinds of media such as plate-like media other than cards, or sheet-like media such as labelling sheets or the like. It is therefore necessary to print on media whose thicknesses vary, for example, from plates of about 3 mm thick to labelling sheets of about 0.1 mm thick.
FIG. 8
shows a printing region of a conventional thermal printing apparatus for printing on media of different thicknesses. A thermal head
50
of this thermal printing apparatus is disposed on a head angle member (or a thermal head holder)
53
at substantially the central portion thereof which is at a distance of 62 mm from a shaft
52
of the head angle member
53
. This head angle member
53
is pivotally or swingably supported at one end thereof on the shaft
52
. By the rotation of a cam
55
which comes into contact with the opposite end
54
of the head angle member
53
and the urging force of a spring
56
, the thermal head
50
is moved in a direction towards, and away from, a medium P to be printed.
However, when the thickness of the medium P changes, the position of the thermal head
50
also changes, and the position of the thermal head
50
varies as shown in FIG.
8
. If the thickness of the medium changes by 1 mm with this thermal printing apparatus, the head angle member
53
inclines about 0.9 degree. This inclination of the head angle member
53
leads to a change in the angle of contact of the thermal head with the medium to be printed. As a consequence, this conventional thermal printing apparatus has a disadvantage in that the printing quality becomes poor.
SUMMARY OF THE INVENTION
The present invention is a thermal printing apparatus having: a pair of transporting rollers for transporting a medium to be printed; a head angle member which holds a thermal head at right angles to a direction of transporting the medium transported by the pair of transporting rollers and which is pivotally supported at one end thereof; and head angle member pivoting means which pivots the head angle member so as to move the thermal head towards and away from the medium. The apparatus further comprises shaft moving means which moves a shaft for mounting thereon the head angle member depending on a thickness of the medium. Preferably, the pair of transporting rollers comprise a driving roller and a driven roller, and the shaft moving means moves the driven roller towards and away from the driving roller depending on a thickness of the medium. The thermal printing apparatus further comprises head pressure adjusting means which adjusts a head pressure of the thermal head based on an operation of the shaft moving means which is operated depending on the thickness of the medium.


REFERENCES:
patent: 4990003 (1991-02-01), Jingu et al.
patent: 5066152 (1991-11-01), Kuzuya et al.
patent: 5149210 (1992-09-01), Eriksson
patent: 5458423 (1995-10-01), Sims et al.
patent: 5556213 (1996-09-01), Kudo et al.
patent: 5-20893 (1993-03-01), None

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