Background of the invention
Field of the invention:
[0001] The present invention relates to an improvement in a printer of the type which makes
use of a heat transfer film.
.Description of the prior art:
[0002] Printers making use of heat transfer films have been known. (US-A-3855448) These
known printers, however, involved a problem that the construction of the printer is
complicated due to the separate. provision of the driving mechanism for reciprocatingly
driving a carriage and the driving mechanism for rolling up the heat transfer film
on the carriage.
Summary of the invention
Object of the invention:
[0003] Accordingly, it is a primary object of the invention to provide a printer in which
the driving mechanism for reciprocatingly driving a carriage and the driving mechanism
for rolling up the heat transfer film are united to simplify the construction of the
printer as a whole.
Brief summary of the invention:
[0004] To this end, according to the invention, there is provided a printer having a carriage
adapted to be moved reciprocatingly, a thermal head mounted on the carriage, a heat
transfer film on the carriage, a driving belt for reciprocatingly driving the carriage,
two pulleys between which the driving belt is stretched, and a film roll-up mechanism
for rolling up the film after use, wherein the improvement comprises that the carriage
is fixed to the driving belt at one side of a line interconnecting the pulleys while
the film roll-up mechanism is engaged to the belt at the other side of the line, and
driving means is provided for driving one of the pulleys.
[0005] This printer has a highly simplified construction because the reciprocatory driving
of the carriage and the rolling up of the heat transfer film after use are conducted
by a common driving mechanism.
Brief description of the drawings
[0006]
Fig. 1 is a perspective view of a printer in accordance with the invention;
Figs. 2 to 5, 8 and 9 are sectional views and perspective views showing the practical
arrangement of various mechanical parts of the printer;
Figs. 6 and 7 are sectional view and a plan view of the cassette portion of the printer;
Figs. 10 and 11 are a perspective view and a sectional view of a paper guiding section;
and
Fig. 12 is an illustration showing how the head, the carriage and the heat transfer
film are related to one another.
Description of the preferred embodiments
[0007] A preferred embodiment of the invention applied to a heat transfer type printer will
be described hereunder with reference to the accompanying drawings.
[0008] Referring to the drawings, the printer of the invention has a housing constituted
by an upper case 1 and a lower case 2. The upper case 1 has a lid 3 covering the mechanical
portion 7 of the printer. A paper discharging portion is constituted by a platen 4
and rollers 5 associated with the platen 4.
[0009] Namely, the mechanical portion 7 of the printer includes various machine parts such
as shafts 8 and 9, gear 10 and the platen 4 provided with a platen knob 11. A carriage
12 shown in Fig. 4 is supported by the shafts 8 and 9 for horizontal sliding movement
along these shafts. A thermal head 14 is mounted on the carriage together with a cassette
portion accommodating a heat transfer film.
[0010] The carriage 12 is fixed to one side of a timing belt, and is adapted to be moved
horizontally by means of the timing belt which is stretched between a pulley 17 mounted
on the end of the shaft of a pulse motor 16 and an idle pulley 18 of a belt stretching
mechanism 19. The other side of the timing belt 15 is utilized for rotating the heat
transfer film. The platen 4 is adapted to be rotated by a second pulse motor 20 through
a gear 10. The platen 14 is also rotatable manually through the platen knob 11 independently
of the motor 20.
[0011] A reference numeral 21 designates a release lever which is adapted to release the
pressing force exerted by the pressing rollers on the lower side of the platen 4.
A reference numeral 23 designates a separator having functions such as the separation
of the sheets continuously fed to and discharged from the printer, holding of the
single sheets and so on. The electric power supply to the electric parts such as the
thermal head carried by the carriage 12 is conducted through a flat cable 24. Reference
numerals 25 and 26 denote, respectively, a transformer and a power switch.
[0012] Fig. 2 shows the construction of the frame portion. Numerals 30 and 31 denote side
plates having an identical construction. A bottom plate 32 is provided at its both
ends with projections 33, 34 and 35. These projections are adapted to be fitted in
corresponding apertures formed in the side plates 30 and 31 and caulked to these side
plates to thereby form a frame.
[0013] The shaft 8 is held at its one end by an E-ring 36 and a fastener 37, and is incorporated
in a frame together with a carriage 12. Similarly, the shaft 9 is held on the side
plates 30 and 31 by means of an E-ring 36' and a fastener 37'. The pulley 18 is rotatably
held by the belt stretching mechanism 19, which in turn is held by means of a belt
stretcher mounting screw 38, retaining hole 39 and a biasing spring 40.
[0014] The carriage feeding pulse motor 16 is mounted on the motor base 45 through the intermediary
of a vibration-proof rubber 41. The paper feeding pulse motor 20 is held by the motor
base 45 together with a drive gear 42, intermediate gear 43 and a shaft 44. The motor
base is fixed to the side plate 31 by means of screws. The motors and the associated
parts in combination constitute a driving unit. A transformer support 46 is secured
also to the side plate 31 by means of screws.
[0015] Fig. 4 shows the portion around the carriage 12 of the printer in accordance with
the invention. The carriage 12 carries a cassette 13 loaded with a heat transfer film
50 to which a thermally-fusible ink has been applied. The thermal head 14 is rotatably
held around the shaft 51 through the intermediary of the supporting plate 52. The
arrangement is such that the thermal head presses the platen 4 through the medium
of the heat transfer film 50 and a print paper 53 so that the resistor mounted on
the head 14 produces heat to fuse the ink on the heat transfer film 50 to thereby
effect a printing on the print paper 53.
[0016] The movement of the timing belt 15 causes a rotation of a pulley 55 which is provided
at its one end with a gear 54. At the same time, the timing belt 15 drives at its
reverse side a pressing roller 56. On the other hand, a lever 57 provided at its one
end with a gear 59 is rotated through frictional engagement with a corrugated washer
58, and a gear 60 is rotated through the intermediary of the gear 54 to thereby roll
up the heat transfer film 50.
[0017] A control board unit 61 is held by the lower case 2 and is extractable rearwardly.
[0018] The copy paper 53 is fed by the frictional engagement between the pressing rollers
62, 62' and the platen 4. These pressing rollers 62, 62' are held resiliently by a
guide portion 64 through shafts 63, 63', and are fixed to a rotary shaft 65. A reference
numeral 66 designates a guide for the copy paper 53 and is adapted to prevent involvement
of the heat transfer film 50.
[0019] Fig. 5 illustrates the operation of the carriage 12. The arrangement is such that,
as the pulley 17 rotates, the belt 15 runs to make the carriage 12 run, while rotating
the pulleys 55 and 66.
[0020] In this state, a solenoid 68 is energized to attract its plunger 69 from the position
A' (broken line) to the position A (full line). Consequently, the head pressing lever
70 is rotated to push the head 14 through a retaining member 71, spring 72 and a pressing
lever 73.
[0021] On the other hand, the rotation of the pressing lever 70 releases the lever 57 so
that the latter is rotated through the friction engagement with the corrugated washer
58 to permit the gear 59 to conduct a transmission of rotation between the gears 54
and 60. A reference numeral 74 designates a transmission type photosensor adapted
to detect presence or absence of the heat transfer film 50 in the cassette 13.
[0022] Figs. 6 and 7 show the cassette 13 in section and in plan, respectively. An idle
roller 81 is resiliently pressed by a spring 82 onto a pinch roller 80 fixed to one
end of the shaft of the gear 60. The pinch roller 80 cooperate with the idle roller
81 to take-up the heat transfer film 50. A retaining portion 89 on the shaft end of
the roller 56 engages with the core 76 to roll up the film thus taken up. An idle
core 75 is adapted to be driven by the film which runs along the pinch rollers 78,
78', 79 and 79'.
[0023] Referring now to Fig. 8, the core 76 is adapted to be rotated only in the direction
for rolling up the film 50, through the rotation of the pulley 55 and the pulley 56.
The torque of the roller 56 rotates the shaft 86 through the intermediary of the spring
84 and the friction plate 85. However, the shaft 86 is provided with a ratchet 87
having teeth 87' which engages with an upper lid 88 of the carriage to allow the shaft
86 to rotate only in one direction. Therefore, the shaft 86 rotates only when the
core 76 rotates clockwisely as viewed in Fig. 7, so that the film 50 can be rolled
up on the core 76.
[0024] It may appear possible to roll up the film 50 on the core 76, even if the pinch roller
80, idler 81 and the spring 82 are omitted. According to the invention, however, the
arrangement is such that the film 50 can be fed when the head 14 is under the pressure,
i.e. when the solenoid 68 is attracting its plunger as shown in Fig. 5A.
[0025] Figs. 10 and 11 show how the pressing rollers 62, 62' engage with the guide portion
64. It will be seen that the shafts 63 and 63' are retained at their both ends with
fasteners 90.
[0026] In operation, the control board unit 61 operates in accordance with the instructions
given by the host computer, and the carriage motor 16 and the solenoid 68 are energized.
Consequently, the plunger 69 of the solenoid is moved from the position shown by broken
line in Fig. 5 to a position shown by full line in the same Figure, so that the head
pressing lever 70 is rotated. Consequently, the head 14 is pressed through the retaining
piece 71, spring 72 and the pressing lever 73, to thereby press the heat transfer
film 50 to the platen 4 through the intermediary of the copy paper 60.
[0027] In this state, the electric power is supplied to the head 14 and also to the carriage
driving motor 16 so that the carriage 12 is driven through the belt 15. At the same
time, the thermal head 14 produces heat to melt the pigment ink on the surface of
the heat transfer film 50 to thereby commence the printing on the print paper 53 through
the transfer of the ink.
[0028] Then, the carriage 12 moves with the head 14 held in the pressing position from the
position A to the position B as shown in Fig. 12. The heat transfer film 50 usually
has a base made from a polyester film, which is adjacent to the head 14, and a pigment
ink is applied to one side of the film, which is adjacent to the copy paper. The head
makes the film contact with the copy paper. A wear resistant layer of a material such
as a nitrided tantalum is formed on the head surface by spattering to provide a smooth
surface. Therefore, the coefficient of friction p between the copy paper 53 and the
heat transfer film 50 is much greater than the coefficient of friction p' between
the heat transfer film 50 and the thermal head 14. As the head 14 moves while pressing
the platen 4, the head 14 slides on the surface of the heat transfer film 50 without
causing relative movement between the copy paper 53'and the heat transfer film 50.
Consequently, the core 75 is rotated so that the heat transfer film 50 is pulled out
by a length I' equal to the amount I of movement of the head 14 from the position
A to the position B.
[0029] Consequently, it is possible to be pulled out the heat transfer film by a movement
of the head 14 held in the pressing position, so that the mechanism for pulling the
heat transfer film 50 is simplified. Moreover, the transition of heat from the head
14 to the film 50 is facilitated because the head is always held in contact with the
heat transfer film unless the core 75 is locked or the heat transfer film 50 is ruptured.
[0030] On the other hand, referring to Figs. 5, 8 and 9, the roller 56 is rotated by the
running of the belt 15 so that the shaft 86 is rotated through the friction plate
85 and the ratchet 87 to frictionally drive the core 76 only in one direction. Furthermore,
the operation of the solenoid 68 causes the . lever 57 to rotate the intermediate
gear 60, so that the lever 57 and the pressing lever 70 are disengaged from each other
to cause a rotation of the roller 80. Consequently, the roller 80 takes up the film
50 by an amount equal to that pulled out from the core 75, and the taken-up film 50
is rolled up by the core 76.
[0031] Thus, according to the invention, the transfer film 50 is fed only when the carriage
12 is running and the solenoid 68 is energized so that the new portion of the heat
transfer film 50 is used and fed only during the printing which is conducted by the
head 14 pressed against the platen 4.
Effect of the invention
[0032] In the printer of the invention, the running belt is stretched between two pulleys.
The carriage is fixed to the belt at one side of the line interconnecting two pulleys,
while the film roll-up mechanism is engaged to the belt at the other side of the line.
As one of the pulleys is driven, both of the carriage and the film roll-up mechanism
are driven by a common driving source. Consequently, the construction of the printer
as a whole is very much simplified.