JPH0347508B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a document table drive device for an electrophotographic copying machine, and more particularly to a document table drive device that moves a document table using a rack and a drive pinion.

Conventionally, most of the document table drives in electrophotographic copying machines with a movable document table have been performed using wires and pulleys, but wires and pulleys require a large amount of space and are not suitable for downsizing copiers. Ta. Furthermore, during assembly, wire hanging requires manual labor and wire tension adjustment is also required, making it unsuitable for automatic assembly. Therefore, a rack and pinion type document table drive system, which has a rack on the document table and a pinion to drive the document table, has been considered, and some of them have already been commercialized. The rack and pinion document table drive system requires only a small space, but
It is difficult to maintain an appropriate distance between the rack and pinion, and if they are too far apart or too close together, a lot of vibration will be applied to the document table, causing image blur. Furthermore, even if you improve the accuracy of each part and set the distance between the rack and pinions appropriately, if the document table moves and the center of gravity of the document table moves away from the main body, the document table may tilt and the distance between the rack and pinions may change. . Furthermore, there is a limit to increasing the precision of each component, and it is extremely difficult to maintain an appropriate distance between the rack and pinions without adjustment.

FIGS. 1 and 2 schematically show how a conventional rack 2 and pinion 3 mesh. 1 is a document table to which a rack is fixed, and 4 is a rotating shaft of a pinion. Since the meshing of the rack and pinion is determined by the relative positional relationship between the two, the explanation here will be based on the assumption that the rack is in the correct position and the error occurs on the pinion side. In FIG. 1, the normal meshing relationship between the rack and pinion is when the center of the pinion, where the respective pitch lines 2p and 3p coincide, is located on n. The gap between the rack and pinion in this state is called backlash. Therefore, the fact that the pitch lines 2p and 3p do not match and deviate from each other means that the backlash changes. However, in reality, the pitch line changes due to the machining and assembly of the rack and pinion, as well as changes over time such as wear, resulting in errors a and b in the vertical direction of the center of the pinion.

The purpose of the present invention is to eliminate the drawbacks of the above-mentioned prior art,
To provide a document table driving device in which the distance between a rack and a pinion is always kept constant while the document table is being driven, and the backlash does not change. This is intended to prevent vibrations during movement of the document table.

The structure of the present invention that achieves the above object includes: a document table on which a document is placed; a rack provided on the document table; a drive pinion that rotates while meshing with the rack to move the document table; a first abutting member provided in parallel with the rack; and a first abutting member that rotates integrally with the drive pinion, and
The document table drive device is characterized in that it has a second protrusion that abuts against the abutment member of the document table and holds the rack at a predetermined position with respect to the drive pinion.

Furthermore, a document table on which a document is placed, a rack provided on the document table, a first abutting member provided on the rack parallel to and integrally with the rack, and meshing with the rack. a drive pinion that rotates together with the drive pinion and moves the document table; and a drive pinion that rotates integrally with the drive pinion and moves the document table;
a second abutment member that abuts against the abutment member to hold the rack in a predetermined position with respect to the drive pinion; and support means that elastically supports the rack with respect to the document table. 1 is a document table driving device characterized by having the following features.

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

FIG. 3 is a sectional view of the document table driving device according to the first embodiment, viewed from the document table moving direction. A rack 2 is fixed to the lower part of the document table 1 or the document table support plate, and the rack 2 is meshed with a pinion 3 that is rotationally driven.

The rack 2 is integrally provided with a first abutting member 2a having the same height as the pitch 2p of the rack. The second abutting member 3a is a roller having the same outer diameter as the pitch 3p of the pinion 3, and the pinion drive shaft 4
It is rotatably mounted on the top. Therefore, when the first and second abutting members are in contact with each other, the pitches 2p and 3p match, and the backlash can be kept constant, thereby preventing vibrations during movement of the document table.

However, as mentioned above, in some cases, pinion 3 may be damaged due to insufficient precision in machining or assembly.
may vary a and b with respect to the central axis n.
In such a case, if the central axis n shifts upward by an amount a, even if the backlash can be maintained, the document table 1 will be lifted accordingly, and the document will be out of focus. On the other hand, when it shifts downward by b, the first abutting member 2a and the second abutting member 3
a will move away, and the crash will become larger.

FIG. 4 shows a second embodiment of the invention.

In FIG. 4, a gap 5 is formed between the rack 2 provided with the first abutting member 2a and the document table 1.
The rack 2 itself can be elastically deformed via spacers (not shown) at both longitudinal ends of the rack. The gap 5 at the time of setting should be set to the expected error in the distance between the rack 2 and the pinion 3, that is, at least a+b as shown in FIG. 1, for example. However, in the operating state where the rack and pinion are engaged, the gap is reduced by b because they are engaged with each other with some pressure. With this structure, even if the pinion moves upward by a distance a, the rack moves upward accordingly, so that the first abutting member and the second abutting member are in contact with each other. Also,
Even if the pinion 3 moves downward, the rack 2 is originally compressed upward by b, so this gap is restored, the rack 2 follows the pinion 3 and moves downward, and the first thrust The abutting member 2a and the second abutting member 3a can always be kept in contact with each other. As described above, in this embodiment as well, the backlash of the rack and pinion does not change during movement of the document table, and vibration can be prevented.

FIG. 5 further shows a third embodiment, in which an elastic member 6 such as a leaf spring or anti-vibration rubber is provided along the rack in the space shown in FIG. 4. Therefore, all of the elasticity is provided by the elastic member, which not only prevents vibrations during movement of the document table but also reduces deformation of the rack, thereby reducing fatigue due to repeated deformation.

Note that FIG. 6 is a sectional view of the document table viewed from the moving direction of the document table, and FIG. 7 is a side view of the document table. The document placing glass 7 is supported by the document table 1 and reciprocates with respect to the copying machine main body 8 in a direction perpendicular to the plane of the drawing. The document table driving device having a rack and pinion according to the present invention is provided on the document table.

FIG. 7 is a side view of the fourth embodiment.

A document table 1 and a rack 2 are supported by spacers 9 at both ends to form a gap 10, and a leaf spring 11 is provided in the gap 10 so that the rack 2 is elastically deformed.

As explained above, by providing an appropriate space between the document table and the rack and interposing elastic means that meet the conditions, it is possible to always maintain appropriate backlash between the rack and pinion. Therefore, the movement of the original platen is made smooth, which has the effect of obtaining beautiful images during copying. In addition, due to the appropriate elasticity of the rack, the document table does not float, which is another factor contributing to the creation of more beautiful images. It also has the function of absorbing errors caused by the expected part precision assembly accuracy, and has the effect of enabling assembly work without adjustment.

As explained above, in the present invention, the distance between the rack and pinion is always kept constant while the document table is being driven, and the backlash is always maintained appropriately.

This prevents vibrations during movement of the document table and makes the movement smooth.

[Brief explanation of drawings]

1 and 2 show the state of engagement between a conventional rack and pinion, the former being a side view and the latter a front view. FIG. 3 shows a first embodiment of the present invention, which is a front sectional view of the document table drive device, FIG. 4 shows a second embodiment of the invention, and FIG. 5 shows a third embodiment of the invention. 6 is a cross-sectional view of the document table seen from the moving direction of the document table according to the present invention, and FIG. 7 is a side view of a document table driving device showing a fourth embodiment. DESCRIPTION OF SYMBOLS 1... Original table, 2... Rack, 2a... First abutting member, 3... Pinion (drive pinion),
3a... second abutment member, 4... drive shaft, 6
...Elastic member (elastic means).

Claims (1)

[Scope of Claims] 1. A document table on which a document is placed; a rack provided on the document table; a drive pinion that rotates while meshing with the rack to move the document table; and a rack provided on the document table. a first abutting member provided in parallel; a first abutting member that rotates integrally with the drive pinion;
a second abutment member that abuts against the abutment member to hold the rack in a predetermined position with respect to the drive pinion. 2. A document table on which a document is placed; a rack provided on the document table; a first abutting member provided on the rack parallel to and integrally with the rack; and a first abutment member that is engaged with and rotates with the rack. a drive pinion that moves the document table; and a drive pinion that rotates integrally with the drive pinion and that moves the document table.
a second abutment member that abuts against the abutment member to hold the rack in a predetermined position with respect to the drive pinion; and support means that elastically supports the rack with respect to the document table. What is claimed is: 1. A document table drive device comprising: