[0001] The subject invention concerns a device in printers comprising a printing unit which
is arranged, by being pressed against a web, to apply print on said web. The device
likewise comprises means arranged to remove said printing unit from its print-application
position against the web for the purpose of allowing the web to be advanced to a fresh
print-application position.
[0002] A printing unit used in this context, i.e. in printers known as thermal-transfer
printers, in which print is transferred from a thermal-transfer ink ribbon to a web,
is pressed against the web by means of comperatively strong compression springs. As
soon as print has been applied on the web the printing unit may be lifted somewhat
away from the web to allow the latter to be advanced sufficiently far to allow new
print to be applied thereon. In accordance with prior-technology electro-magnets or
other mechanical devices are used which, considering the above-mentioned strong counteracting
compression springs, also have to be very powerful and thus expensive, heavy, and
bulky.
[0003] The subject invention provides a device which has a simple construction and therefore
is inexpensive. At the same time the function of the device is extremely reliable.
The features characterising this device appear from the appended claims.
[0004] The invention will be described in closer detail in the following with reference
to the accompanying drawings, wherein
Fig. 1 is a perspective view of a printer with a lateral wall removed,
Fig. 2 illustrates the device in accordance with the invention in a perspective view
on a larger scale, and
Fig. 3 illustrates on an even larger scale an eccenter member incorporated in the
device.
[0005] Fig. 1 illustrates a printer 1 including a printing web 2, an ink ribbon 3 and a
printer 4, the latter arranged to apply print to the web 2 via the ink ribbon 3. However,
the printer could equally well be of the kind known as a thermal-transfer printer
in which print is transferred to the web by means of a thermal-transfer ink ribbon.
[0006] Fig. 2 illustrates the printing unit 4 on a larger scale. The printing unit is of
an entirely prior art nature and therefore need not be described in any detail. The
web 2 and the ink ribbon 3 are carried through the printing unit 4 as illustrated
in Fig. 1 and the printing unit 4 is pressed against web and ribbon with a comperatively
large force in the direction of arrow 5 with the aid of compression springs, not illustrated
in the drawings.
[0007] In accordance with the invention the printing unit 4 is arranged to be pivoted counter
to the direction of arrow 5 about a shaft 6. One end of the latter fixedly supports
a lever 7. An eccenter member 9 abuts against that end 8 of the lever 7 that is opposite
to the attachment of said lever to the pivot shaft 6. In accordance with a further
characteristic feature of the invention the eccenter member consists of a roller bearing
comprising an inner carrier ring 10, an outer carrier ring 11, and rolling elements
12, i.e. bearing balls, positioned intermediate the rings. In other words, the roller
bearing could be an ordinary ball bearing.
[0008] The roller bearing is mounted eccentrically on a rotary shaft 13 to which the roller
bearing is fixedly mounted by means of its inner carrier ring 10 and which shaft thus
forms the output shaft of an electric motor 14. When the latter brings the rotary
shaft 13 to turn, the inner carrier ring 10 thus will co-rotate therewith whereas
the outer carrier ring instead will perform an orbiting movement, from a lowest position
to the highest position illustrated in dash- and -dot lines in Fig. 3. Because the
out carrier ring 11 abuts against the end 8 of the lever 7 the lever 7 will follow
the movements of the outer carrier ring 11 vertically. In consequence thereof, when
the eccenter member 9 moves to its lower position, the lever 7 will pivot the printing
unit 4, via the shaft 6, against the action of the downwardly directed spring action,
so as to form a gap allowing advancement of the ink ribbon 3 and the web 2. When the
eccenter member 9 is turned to its upper position, illustrated in dash- and -dot lines,
the printing unit 4 will again be forced downwards, thus bringing the lever 7, via
the shaft 6, to follow the eccenter member upwards to the upper position.
[0009] It is easy to synchronise the turning of the eccenter member 9 by means of the electric
motor 14 with the advancement of the web 2 and of the ribbon 3. Consequently, the
device in accordance with the invention is of a simple and reliable construction to
control and guide the printing unit 4 from its open position to its closed position
of application, and vice versa.
[0010] The invention is not limited to the embodiment illustrated but may be varied in several
ways within the scope of the appended claims. For instance, the eccenter member 9
may be formed by another type of roller bearing than a ball bearing.
1. A device in printers comprising a printing unit (4) which is arranged, by being pressed
against a web (2), to apply print on said web (2), and means arranged to remove said
printing unit from its print-application position against the web (2) for the purpose
of allowing the web (2) to be advanced to a fresh print-application position, characterized in that said printing-unit removal means comprise a pivot shaft (6) on which the printing
unit (4) is mounted for pivotal movements towards or away from its print-application
position against the web (2), and a lever (7) which is rigidly mounted on the pivot
shaft (6) and in contact with a rotary eccenter member (9) arranged, when turning
round, to pivot the lever (7), thus bringing the latter to turn the shaft (6) for
the purpose of pivoting the printing unit (4) away from the web (2).
2. A device as claimed in claim 1, characterized in that said eccenter member consists of a roller bearing (9) comprising an inner carrier
ring (10), and outer carrier ring (11), and rolling elements (12) positioned intermediate
said carrier rings, and that said roller bearing (9) is eccentrically mounted on the
rotary shaft (13) to which the inner carrier ring (10) of the roller bearing (9) is
fixedly secured.
