JPH0259775B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a retraction mechanism for a print head included in a printer such as a serial printer.

In serial printers, the print head is usually pressed against the platen with a constant pressure.
When setting paper or starting a new line, the print head must be separated from the platen. Therefore, the print head has a structure that allows it to take a position pressed against the platen, that is, an approach position, and a position that is separated from the platen, that is, an escape position. In order to move the print head, it is necessary to provide a retraction mechanism for the print head.

[Conventional technology]

Conventionally, the print head has a structure in which the movement of the approach escape shaft is used to take the approach position and the escape position, and this movement of the print head is used to connect and disconnect the rotational drive system of the ribbon take-up shaft. .

An example of such a print head retraction mechanism is shown in FIG. The figure shows a side view of the evacuation mechanism and the main parts around it. 1 is the platen, 2 is the shaft,
Reference numeral 3 denotes a print head that can swing freely as shown by arrow A around the shaft 2 and also move freely in the longitudinal direction of the platen 1. Reference numeral 4 denotes an approach escape that can be moved up and down as shown by arrow B by external power from a drive source (not shown). A shaft 5 is a fixed member such as a carrier frame that is movable in the longitudinal direction of the platen 1 together with the print head 3, and 6 is a fixed member that is interposed in tension between the fixed member 5 and the print head 3 to move the print head 3 to the platen 1. 7 is a ribbon winding shaft for the thermal transfer ribbon used for printing by the printing head 3; 8 is a clutch provided on the ribbon winding shaft 7; 9 is engaged with the clutch 8; Clutch 10 is a pinion which integrally includes the clutch 9 and is movable up and down as shown by arrow C and rotatable as shown by arrow D; 11 is a rack provided at a fixed position that meshes with the pinion 10; A circumferential groove is provided between the clutch 9 and the pinion 10, 13 is a support shaft, and 14 is swingable about the support shaft 13 as shown by arrow E, and the free end is engaged with the circumferential groove 12. 15 represents a spring interposed in tension between the actuator 14 and the print head 3, respectively.

When printing, approach escape shaft 4
takes the raised position as shown in FIG. Clutch 9 because I take it
and clutch 8 are engaged. Therefore, as the pinion 10 moves along the rack 11 as the print head 3 moves in the longitudinal direction of the platen 1, the rotation of the pinion 10 is transmitted to the ribbon take-up shaft 7 via the clutches 9 and 8. Therefore, winding of the ribbon (not shown) is performed, so that the ribbon can be used uniformly over its entire length.

At the time of escape, the approach escape shaft 4 takes the lowered position and pushes down the print head 3, so the print head 3 moves away from the platen 1 and takes the escape position, and the actuator 14
is pressed down, so that clutch 9 separates from clutch 8, and the drive for feeding the ribbon is cut off. Therefore, there is no risk of the ribbon being unnecessarily fed or being rewound when the print head 3 returns to the beginning of the line at line feed.

[Problem that the invention seeks to solve]

In the structure described above, during the operation of moving the approach escape shaft 4 from the raised position to the lowered position in order to move the print head 3 from the approach position to the escape position, the drive source of the approach escape shaft 4 is It is necessary to generate a force to push down both the spring 6 for generating head pressure and the spring 15 for engaging and disengaging the clutches 8 and 9. Moreover, the approach escape shaft 4 always moves in both directions during a long stroke from when the shaft 4 contacts the print head 3, that is, when the print head 3 starts moving, until the print head 3 is retracted and the clutch 9 is released. Since the approach escape shaft 4 is loaded by the springs 6 and 15, there is a problem in that the drive source for the approach escape shaft 4 requires a large amount of power.

[Means for solving problems]

The present invention provides a print head evacuation mechanism that solves the above problems and requires only a small power source. a print head actuating member movable between a first position for placing the print head in an approach position and a second position for placing the print head in an escape position; a resilient means interposed between the printing head and the printing head to bias the printing head in a direction toward the platen; the print head actuating member engages the print head between the second position and the print head actuating member engages the print head between the first position and the third position; This is accomplished by a printing head retraction mechanism characterized by comprising an engaging member that releases the mated state.

[Effect]

In the above print head retraction mechanism, when the print head actuating member assumes the first position, the print head is located at the approach position, and the engagement state between the print head actuating member and the print head by the engagement member is released. Therefore, the printing head is pressed against the platen with a predetermined head pressure by the urging force of the resilient means. In this way, when the resilient means generates head pressure, there is no problem whether the third position of the printing head actuating member is located anywhere between the first position and the second position. It can be brought sufficiently close to the first position. Thus, during approach or escape, the printhead actuation member engages the engagement member while the printhead actuation member moves between the third and second positions, ie, for a majority of the total stroke of the printhead actuation member. Since it is integrated with the print head by the action of , no load is applied to the driving source of the print head actuating member by the above-mentioned resilient means. In addition, since the print head moves from the escape position to the approach position, the load of the above-mentioned resilient means is applied to the drive source of the print head actuating member during the portion of the stroke of the print head actuating member from the third position to the first position. , this part is the third part as mentioned above.
It can be made sufficiently short by moving the position closer to the first position. In this way, in the approach/escape motion of the print head, the load is applied only near the end of the motion by the elastic means, so the power source for the print head operating member can be a small power source. .

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a perspective view of essential parts of an embodiment of the present invention. 2 to 4 are side views of the portion of FIG. 1 showing different operating states. Note that the same parts are denoted by the same reference numerals throughout all the figures including the above-mentioned FIG. 7. In the figure, reference numeral 16 denotes a lever that is an example of a lever used as a print head moving member. The lever 16 is swingably supported by a shaft 2 that is common to the print head 3, and a resilient means of the present invention is provided between the tip of the lever 16 and the tip of a lever portion 17 provided on the print head 3. A spring 18 is interposed in tension. A pin 19 protrudes from the intermediate portion of the lever 16, and the lever 16 is swing-driven by a drive source (not shown) via the pin 19, so that the lever 16 can be moved between the first position F shown in FIG. A second position G shown in FIG. 4 and a third position H shown in FIG. 3 can be taken. As the drive source for the lever 16, one using a magnet, one using a cam driven by a motor, etc. can be used. The lever portion 17 of the print head 3 has a pin 20 protruding therefrom, which is the engaging means of the present invention, at a position where it comes into contact with the lever 16 which is in the third position H. Therefore, when the lever 16 assumes the first position F in FIG. 2, the print head 3 assumes the approach position J due to the biasing force of the spring 18. Also, in Figure 4, lever 1
6 assumes the second position G, the print head 3
The escape position K is taken by being pushed by the lever 16 via the lever 0. Reference numeral 21 indicates a micro switch for detecting the state of the print head 3, and 22 indicates another lever portion provided on the print head 3. The lever section 22 of the print head 3 and the microswitch 21 are in such a positional relationship that the lever section 22 pushes down the microswitch 21 when the print head 3 takes the escape position shown in FIG.

5 and 6 are plan views showing different operating states of portions of FIG. 1 that are different from those shown in FIGS. 2 to 4. FIG. Referring mainly to FIGS. 1, 5 and 6, 23 is a rack installed parallel to the platen 1, 24 to 27
28 is a ribbon winding shaft for the thermal transfer ribbon rotated by the gear 27, 29 is a bracket that can freely swing around the ribbon winding shaft 28, and 30 is a bracket. the central shaft of the gear 26 attached to 29;
31 is a fixed member such as a carrier frame, 32 is a spring interposed in tension between the bracket 29 and the fixed member 31, 33 is a central shaft, and 34 is swingably supported by the central shaft 33 and has brackets at both ends. 29 and an actuator engaging the lever portion 17 of the print head 3; 35 a spring interposed in tension between the actuator 34 and the bracket 29 to ensure that the bracket 29 follows the movement of the actuator 34; show.

Next, the operation of the print head retraction mechanism of this embodiment will be explained. When the lever 16 takes the first position F shown in FIG. 2, the print head 3 takes the approach position J, and the gear 26 moves to the position shown in FIG. Take the meshing position L with the gear 25 shown in FIG. Therefore, as the print head 3 moves in the longitudinal direction of the platen 1, the gears 24-27
When the ribbon moves along the rack 23, the rotation of the gear 24 passes through the gears 25 to 27 to the ribbon winding shaft 28.
Since the winding is transmitted to the ribbon, winding of the ribbon (not shown) takes place, so that the ribbon can be used uniformly over its entire length. Also approach position J
The printing head 3, which has a fixed position, is pressed against the platen 1 with a predetermined head pressure based on a spring 18.

At the time of escape, the lever 16 starts swinging clockwise in FIG. 2 and first assumes the third position H shown in FIG. 3, so that the lever 16 engages with the pin of the print head 3. The movement of the lever 16 from the first position F to the third position H is facilitated by the urging force of the spring 18. When the lever 16 further swings clockwise, the print head 3 swings together with the lever 16 via the pin 20, and in FIG. 4, the lever 16 assumes the second position G and the print head 3 escapes. Take position K. At this time, print head 3
The contact point of the micro switch 21 is made by the lever part 22, and according to the signal based on this,
The drive source of the lever 16 stops pushing down the lever 16. The lever 16 is in the third position as described above.
While moving from the position to the second position, the spring 18
The force is not applied to the power source of the lever 16 at all.

Just before the end of the escape operation shown in FIG. 4, the lever portion 17 of the print head 3 pushes down the actuator 34, causing the bracket 29 to rotate counterclockwise in FIG. 5 against the biasing force of the spring 32. , Therefore, since the gear 26 assumes the non-meshing position M where it is disengaged from the gear 25 (Fig. 6),
Even if the gear 24 rotates due to the rack 23, the gear 2
6, 27 and the ribbon winding shaft 28 do not rotate. Therefore, there is no risk that the ribbon will be unnecessarily wound up when the print head escapes, or that the ribbon will be rewound due to the print head changeover operation.

When approaching, the pin 19 of the lever 16 is pushed up by a drive source (not shown), so that the lever 1
6 rotates counterclockwise from the second position G in FIG. 4, through the third position H in FIG. 3, to the first position F in FIG. At the initial stage of the operation of the lever 16, the movement of the lever 16 is assisted by the spring 32. Furthermore, since the lever portion 17 of the print head 3 rotates counterclockwise together with the lever 16, the actuator 34 and the bracket 29 are allowed to return to their original positions based on the biasing force of the spring 32, and therefore the gear 26 is Return to the meshing position L in Figure 5. Also, the lever 16 is in the third position H in FIG.
At this point, the print head 3 hits the platen 1 and stops rotating counterclockwise, and when the lever 16 further rotates counterclockwise, the lever 16 separates from the pin 20 of the print head 3. When the lever 16 reaches the first position F in FIG. 2, the drive source for the lever 16 stops pushing up the lever 16. The printing head 3 is again pressed against the platen 1 by head pressure based on the biasing force of the spring 18 in FIG.

As explained above, in the print head retraction mechanism of this embodiment, the drive source of the lever 16, which is the print head operating member, includes a spring 32 for disconnecting the ribbon winding drive system just before the end of the operation at the escape position. The lever 16 is only subjected to a load based on the biasing force of the spring 18 and the non-force of the spring 18 for head pressure just before the end of the approach operation, and the load is short and small, and therefore a small power is required as a drive source for the lever 16. can be used. Moreover, since the ribbon winding drive can be switched in accordance with the print head retraction mechanism, there is no need for a separate power source for switching the ribbon drive, and the ribbon can be taken up from the print head and its retraction mechanism. The entire structure including the drive switching mechanism can be made smaller in diameter and lighter in weight.

〔Effect of the invention〕

As explained above, according to the present invention, the drive source for the print head actuating member in the print head retraction mechanism can be of low power, so the retraction mechanism including the drive source and the power transmission mechanism The entire print head can be made smaller and lighter, which can save energy and contribute to reducing the cost of the printer to which the print head is applied.

[Brief explanation of drawings]

FIG. 1 is a perspective view of essential parts showing one embodiment of the print head retraction mechanism of the present invention, and each of the figures from FIG. 2 to FIG. 4 is a side view showing the portion shown in FIG. 1 in different operating states. 5 and 6 are plan views showing other parts of FIG. 1 in different operating states, and FIG. 7 is a side view of essential parts showing a conventional print head retraction mechanism. 1...Platen, 2...Shaft, 3...Printing head, 16...Lever, 17, 22...Lever portion, 18...Spring, 19, 20...Pin,
21...Micro switch, 23...Rack, 2
4, 25, 26, 27... Gear, 28... Ribbon winding shaft, 29... Bracket, 30, 33...
... Central shaft, 31 ... Fixing member, 32 ... Spring, 34 ... Actuator, 35 ... Spring.

Claims (1)

[Claims] 1. In a printer having a print head that is movable with respect to the platen between an approach position and an escape position, a first position for placing the print head in the approach position and a second position for placing the print head in the escape position. a print head actuating member movable between the print head actuating member; a resilient means interposed between the print head actuating member and the head for biasing the print head toward the platen; The print head actuating member and the print head are brought into engagement between the second position and a third position, which is moved a certain distance from the first position toward the second position, and the print head actuating member is moved to the first position. and an engagement member for disengaging the print head from the print head operating member between the print head and the third position.