JPH0121810Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a locking mechanism for a tractor used in a paper feeding device such as a line printer.

FIG. 1 shows an example of a conventional tractor lock mechanism. The tractor 1 has a belt having a plurality of sprocket pins 2, and the sprocket pins 2 are engaged with sprocket holes of continuous paper (not shown).
Continuous paper is conveyed by rotating a belt. The tractor 1 is supported by a drive shaft 3 and a guide shaft 4, and has a structure that allows it to move left and right depending on the width of continuous paper. A lock lever 5 is provided to fix the tractor 1 at a position suitable for the width of the continuous paper. The lock lever 5, together with an eccentric wheel 6, is rotatably attached to a shaft protruding from the tractor 1 with a fixing screw 7, and the eccentric wheel 6 is always pressed against the guide shaft 4 by a spring 8. is fixed. By moving the lock lever 5 in a direction in which the eccentric wheel 6 moves away from the guide shaft 4, the tractor 1 can be moved.

In a locking mechanism that aims for such a wedge effect, the locking force is significantly different when the lock lever 5 is gradually released from the open state and when the hand is released all at once. The problem is that the tractor 1 moves, resulting in poor printing, and in the latter case, the eccentric wheel 6 gets stuck in the guide shaft 4, and a considerable amount of force is required to release the lock next time. In addition, the surface of the eccentric wheel 6 needs to be in good condition so that the guide shaft 4 is not scratched and the movement of the tractor 1 becomes difficult, and care must be taken so that the eccentric wheel 6 does not hit diagonally. There are also problems.

FIG. 2 shows another conventional example. When locking the tractor 1, tighten the lock screw 9 and lock the guide shaft 4.
Press it to secure it. To release the lock, rotate the lock screw 9 in the opposite direction. However, in this mechanism, since it is not known how much to tighten the lock screw 9, the lock screw 9 tends to be tightened more tightly than necessary. As a result, when an attempt is made to move the tractor 1, the lock screw 9 may be so tight that the tractor 1 cannot be moved. In addition, if the lock screw 9 is forgotten to be tightened or if it is loosely tightened, the tractor 1 may move due to vibrations, causing a serious accident such as printing defects.

An object of the present invention is to eliminate the above-described drawbacks of the prior art and to provide a locking mechanism that can easily and reliably lock a tractor at any position depending on the width of continuous paper.

This invention focuses on the fact that when a force is applied to a torsion spring in the opposite direction to the torsional direction, its inner diameter expands and returns to its original diameter when the force is released. The relationship between the outside diameter of the guide shaft, the inside diameter of the torsion spring, and the locking lever has been devised so that the inside diameter of the torsion spring can be made larger than the outside diameter of the guide shaft when moving the tractor. be.

FIG. 3 is a diagram showing an embodiment of the tractor lock mechanism of the present invention, and FIG. 4 is an enlarged view of the main parts thereof.
The tractor 21 includes a sprocket pin 22 that engages with the sprocket hole of the paper to convey the paper, a belt 23 that has a plurality of sprocket pins 22 on its outer periphery, and a belt 23 that presses the continuous paper from above and attaches the sprocket pin 22 to the sprocket pin 22. Tractor cover 2 for engagement
4. It is equipped with a lock lever 25, a torsion spring 26, etc. for locking the tractor 21 in any position. As shown in FIG.
The tractor 21 has a semi-cylindrical portion that fits into the semi-cylindrical portion, and both sides of the semi-cylindrical portion in the axial direction are rotatably supported by the side walls of the main body of the tractor 21. Further, the inner diameter of the torsion spring 26 is set to be smaller than the outer diameter of the guide shaft 4, and both ends of the torsion spring 26 are attached by means such as insertion into slits or the like provided in the lock lever 25 and the main body of the tractor 21. Therefore, the torsion spring 26 is fitted onto the guide shaft 4 with its inner diameter expanded.

In the tractor 21 configured as described above,
When the tractor 21 is to be positioned and locked according to the width of the continuous paper, the lock lever 25 is first rotated in the direction of arrow A. As a result, the inner diameter of the torsion spring 26 becomes larger than the outer diameter of the guide shaft 4,
The guide shaft 4 can be moved along the axial direction, and the tractor 21 can be moved by the lock lever 25. When the position of the tractor 21 is determined and locked, the torsion spring 26 attempts to return to the inner diameter set slightly smaller than the outer diameter of the guide shaft 4 by releasing the lock lever 25. As a result, the torsion spring 26 is attached to the guide shaft 4 and the tractor 2
1 will be locked.

According to the present invention, the locking by the lock lever remains constant regardless of the strength of the operator's force, so it is easy to release the lock, and since it is a self-locking mechanism, it eliminates loosening due to vibration etc. or carelessness such as forgetting to tighten. be able to. In addition, since the tractor can be moved using the lock lever, it can be operated with one hand, resulting in improved operability.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an example of a conventional tractor lock mechanism, Fig. 2 is a sectional view showing another example of the conventional tractor lock mechanism, and Fig. 3 is a perspective view showing an embodiment of the tractor lock mechanism of the present invention. Figure 4 is the third
FIG. 3 is an enlarged perspective view of the locking mechanism shown in FIG. In the figure, 1 and 21 are tractors, 2 and 22 are sprocket pins, 3 is a drive shaft, 4 is a guide shaft,
5 and 25 are lock levers, 6 is an eccentric wheel, 7 is a fixing screw, 8 is a spring, 9 is a lock screw, 10 is a nut, 23 is a belt, 24 is a tractor cover,
26 is a torsion spring.

Claims (1)

[Scope of utility model registration request] a drive shaft and a guide shaft provided in parallel; a tractor driven by the drive shaft and movable along the guide shaft;
A torsion spring whose inner diameter is set to be smaller than the outside diameter of the guide shaft, a semi-cylindrical part that fits into the guide shaft and extends in the axial direction so as to accommodate the torsion spring at the lower end, and an upper end that projects upward from the tractor body. and a lock lever having a lever part, both ends of the torsion spring are attached to the lock lever and the tractor body, and a semi-cylindrical part of the lock lever is rotatably attached to the tractor body, and the lock lever locks and unlocks the tractor. A tractor lock mechanism characterized by allowing the tractor to be moved.