JPH0468155B2 - - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION This invention relates to a ribbon back tension mechanism for a printing device.

Technical Background of the Invention and Problems Therewith In a printing device, when a printing ribbon or a collection ribbon is fed intermittently, the ribbon holder on the supply side rotates due to the tension of the ribbon, but the stopping position shifts due to rotational inertia, and as a result, the ribbon holder rotates due to the tension of the ribbon. Relax. The ribbon back tension mechanism is used to prevent this slack, and two conventional examples are shown in Figures 1 and 2, respectively.
As shown in the figure. The one shown in FIG. 1 is the first of these conventional examples. A collection ribbon 1 is pulled out from a ribbon holder 2, guided by a ribbon guide 3, and wound around a winding section 4. This winding section 4 is fixedly connected to a ratchet 5 which is rotated intermittently, and ratchet teeth 8 that mesh with each other are provided on the opposing surfaces of the ring 7 and the ribbon holder 2, which are biased in one direction by a spring 6. It is formed.

Therefore, when the ratchet 5 is turned to wind up the collection ribbon 1 on the winding section 4, the ribbon holder 2
and ring 7 rotate while stretching spring 6, and when the resistance force of spring 6 increases, ribbon holder 2 deviates in the sliding direction, slips ratchet teeth 8, and rotates ahead of ring 7. When ratchet 5 stops, collect ribbon 1
The tensile force is removed, and the ring 7 pulls back the ribbon holder 2 by the restoring force of the spring 6, applying back tension to the collection ribbon 1. However, since the ribbon holder 2 is intermittently displaced in the thrust direction, the ring 7 due to the force of the spring 6 depends on the timing when the ratchet teeth 8 engage.
This has the disadvantage that the torque transmitted from the ribbon holder to the ribbon holder 2 varies, and the tension and feed amount of the collection ribbon 1 are not constant.

Moreover, what is shown in FIG. 2 is a second conventional example different from the first conventional example shown in FIG. A mainspring 10 is pressed against the inner periphery of a holder 9 that holds an unused collection ribbon 1, and the inner end of the mainspring 10 is held to prevent friction between the ribbon holder 9 and the outer periphery of the mainspring 10 when the collection ribbon 1 is pulled out. The ribbon holder 9 deflects the mainspring 10 and rotates ahead of the mainspring 10 by slipping, and when the winding side ratchet 5 stops, the restoring force of the mainspring 10 pulls back the ribbon holder 2. There is. In this format, the first
Unlike the type shown in the figure, it is not based on the meshing of ratchet teeth, so there is no small variation in the transmitted torque, but the mainspring 10
It is difficult to maintain a constant frictional force between the inner circumference of the ribbon holder 9 and the inner circumference of the ribbon holder 9, making it impossible to produce large quantities of uniform products. The work of assembling the mating member in correspondence with the holding member on the other side is also troublesome, and has the drawback that the assembly work is difficult.

Purpose of the Invention The present invention was made in view of the above points, and an object of the present invention is to provide a ribbon back tension mechanism for a printing device that can apply a certain tension to the ribbon and simplify the assembly work. be.

SUMMARY OF THE INVENTION This invention elastically fits a diameter-reducing ring to the outer periphery of a ribbon holder that holds a ribbon wound on a winding section in a wound state, and the diameter-reducing ring is attached in one direction by a spring. When the ribbon is fed, the ribbon holder is rotated by the tension of the ribbon being pulled out. At this time, the diameter reduction ring follows the ribbon holder, but the rotation angle of the diameter reduction ring is regulated by a stopper, which causes the reduction to occur. When the diameter machine is slipped against the ribbon holder and ribbon feeding is interrupted, the spring's return force causes the diameter reduction ring and the ribbon holder held by the diameter reduction ring to rotate in the opposite direction, thereby applying back tension to the ribbon. At this time, the ribbon holder is held securely by the tightening force of the diameter-reducing ring, and the torque by the spring is reliably transmitted to the ribbon holder. Note that there is no variation in torque, the back tension to the ribbon is kept constant, and the ribbon tension and feeding amount can be kept constant.Moreover, unlike the second conventional example shown in Fig. Since the diameter-reducing ring is fitted onto the outer periphery of the ribbon holder, it is constructed so as to be easily assembled.

Embodiment of the Invention An embodiment of the invention will be described based on FIGS. 3 to 6. 11 is the carrier. This carrier 11 is slidably held by a carrier shaft 12 and a guide shaft 13 parallel to the platen. This carrier 11 holds a daisy wheel 15 held by a wheel holder 14 and a hammer mechanism 16. Further, a clamp 19 is attached to a ribbon base 17 attached to the carrier 11 for detachably holding a cassette case 18 containing a printing ribbon. Ribbon guides 20 are erected on both sides of the front of the ribbon base 17, and on the front right side of the ribbon base 17, a ratchet 21 that rotates intermittently and a take-up reel 22, which is a winding section, are coaxially connected. A ribbon holder 24 is arranged on the front left side of the ribbon base 17 to hold a collection ribbon 23 in the form of a roll. This ribbon holder 24 is rotatably held by a support piece 25 formed on the left side of the ribbon base 17 via a pin 26. Drum 27 formed on ribbon holder 24
A diameter-reducing ring 28 formed by bending a steel plate is elastically fitted into the ring. A spring 31 is tensioned between a protrusion 29 bent at one end of the diameter reducing ring 25 and a pin 30 erected on the support piece 25, and contacts the protrusion 29 to restrict the rotation range of the diameter reducing ring 28. Stopper 3
2 and 33 are integrally formed on the support piece 25. One stopper 32 is for regulating the maximum amount of deflection of the spring 31.

In such a configuration, the diameter-reducing ring 28 is reduced in diameter by its own elasticity and is attached to the drum 2 of the ribbon holder 24.
Press 7. Now turn the ratchet 21 to remove the collect ribbon 23 held in the ribbon holder 24.
is wound onto the take-up reel 22, but at this time, as shown in FIG. When pulled, the diameter reducing ring 28 comes into contact with the stopper 32 and stops. At this position, the deformation of the spring 31 is at its maximum, and the reduced diameter ring 28 slips against the drum 27 while receiving the biasing force of the spring 31.

When the ribbon feed is interrupted by stopping the ratchet 21, the diameter reducing ring 28 elastically holds the ribbon holder 24 by its own elasticity, and the spring 31
Due to the force, the collection ribbon 23 is rotated back by a rotation angle corresponding to the slack. What is shown in FIG. 6 shows the state of maximum return rotation, in which it has returned in the direction of arrow B and has come into contact with the stopper 33. Therefore, when ribbon feeding is interrupted by stopping the ratchet 21, the ribbon holder 24 is rotated back from the state shown in FIG. 5 to the state shown in FIG. 6, but the state shown in FIG. The collection ribbon 23 does not reach this point, but on the way there, the collection ribbon 23 becomes tensed and comes to a state where it is given back tension, thereby coming to a halt in the middle. In this way, when ribbon feeding is interrupted, the diameter reducing ring 2
8 is rotated by the force of the spring 31, but since the diameter-reducing ring 28 securely holds the ribbon holder 24 and transmits the torque from the spring 31 to the ribbon holder 24, even if the slack generated in the collection ribbon 23 fluctuates, The back tension applied to the collection ribbon 23 is always constant, and the amount of feed of the collection ribbon 23 can be made uniform. The assembly work of fitting the diameter-reducing ring 28 to the drum 77 and adjusting the spring 31 can also be easily performed.

The stopper 33 may be omitted since it requires a considerably strong force to reverse the take-up reel 22 by the back tension of the collection ribbon 23. Further, as shown in FIG. 7, a reduced diameter ring 35 may be used, which is formed by winding a steel wire into a coil and forming a hook 34 on one end of which the spring 31 is hooked. Thereby, the ribbon holder 24 can be tightened with strong force.

Effects of the Invention Since the present invention is constructed as described above, when ribbon feeding is interrupted, the reduced diameter ring is returned to the return direction by the force of the spring, but at this time, there is no variation in the transmitted torque, and the torque by the spring is It is possible to efficiently transmit the back tension to the ribbon holder and keep the tension and feeding amount of the ribbon constant, and furthermore, since the diameter reducing ring fits on the outer periphery of the ribbon holder, This has the advantage that the assembly work can be easily performed.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing one conventional example, Fig. 2 is a partial perspective view showing another conventional example, Fig. 3 is a plan view showing one embodiment of the present invention, and Fig. 4 is its main components. FIG. 5 and FIG. 6 are side views showing the operation of the diameter-reducing ring with a portion thereof in cross section, and FIG. 7 is a perspective view showing a modification of the diameter-reducing ring. 22... Winding reel (winding section), 23... Collection ribbon (ribbon), 24... Ribbon holder,
28... Reduced diameter ring, 31... Spring, 32...
Stoppa, 35...reduced ring.

Claims (1)

[Scope of Claims] 1. A ribbon holder is rotatably provided to hold the ribbon that is pulled by a winding section and sequentially pulled out to the front of the recording paper, and the outer circumference of the ribbon holder is elastically reduced in diameter to a predetermined value. A diameter-reducing ring is provided to hold the ribbon with pressure, and one end of a spring is fixed to a part of the outer periphery of the diameter-reducing ring, so that the spring rotates the ribbon in a direction opposite to the direction of rotation of the ribbon holder caused by the tension of the ribbon. A stopper is provided that biases the diameter reducing ring in the circumferential direction and restricts the rotation angle of the diameter reducing ring in a direction that resists the biasing force of the spring. By regulating the rotation angle of the diameter reducing ring and slipping against the diameter reducing ring, the ribbon holder is rotated in the moving direction of the ribbon, and a certain back tension is applied to the ribbon when the winding section is stopped. 1. A ribbon back tension mechanism for a printing device, characterized in that said diameter reducing ring is rotated back to a position where tension is applied by the biasing force of said spring. 2. A ribbon back tension mechanism for a printing device according to claim 1, wherein the diameter-reducing ring is formed by bending a metal plate. 3. A ribbon back tension mechanism for a printing device according to claim 1, characterized in that a wire is wound into a coil to form a reduced diameter ring.