JPS6344830Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic brush developing device for an electrophotographic copying machine.

A magnetic brush developing device has a magnet fixedly disposed within a rotationally driven non-magnetic sleeve, and magnetic developer is attracted to the circumferential surface of the sleeve to form a spike, thereby sweeping a photoreceptor. However, the amount of developer adsorbed onto the sleeve must be regulated to a constant amount since it affects the image density. This regulation is performed by a doctor placed opposite the circumferential surface of the sleeve with a predetermined gap in between.The gap is 0.2 to 1 mm when using a one-component developer, and 1 to 1 mm when using a two-component developer. Since it is 3mm, it is easy to get clogged with foreign matter. Further, when the toner aggregates, clogging also occurs, resulting in white streaks in the copied image.

The present invention aims to solve the above-mentioned problems, and the figure shows an embodiment thereof.

In FIGS. 1 and 2, 1 is a belt-shaped photoreceptor, and a pulley 2 rotates in the direction of arrow A.
and are driven in the same direction. A sleeve 3 is installed at the bottom of the developing tank 4 and rotates in the direction of arrow B while being adjacent to the photoreceptor 1. A magnet 5 is fixedly arranged inside the doctor 3 so as not to rotate. The developer 6 in the developing tank 4 is attracted by the magnet 5 and adheres to the circumferential surface of the sleeve 3, moves as the magnet 5 rotates, and sweeps the photoreceptor 1 as a magnetic brush 7. Reference numeral 8 denotes a doctor, which is fixed to the wall of the developing tank 4 and whose leading edge faces the circumferential surface of the sleeve 3 via a gap G.

Although the above is a conventional configuration, a wiper 9 is provided in the present invention. wiper 9
is provided with a tongue-like portion 9a inserted into the gap G between the sleeve 3 and the doctor 8, a feed screw 10 is screwed into the base of the tongue-like portion 9a, and a guide rail 1
1 is engaged. The feed screw 10 and the guide rail 11 are arranged parallel to the axis of the sleeve 3.

The wiper 9 is normally located at the end of the sleeve 3 as shown in FIG. Move along 8. At this time, if the gap G is clogged, the tongue-shaped portion 9a of the wiper 9 removes it. In this way, when the wiper 9 reaches the other end of the sleeve 3, it waits there again. Next time, feed screw 10
By reversing , it moves in the opposite direction to the above. The wiper 9 is moved between copy cycles, but the frequency does not have to be every copy cycle.

Note that in the above embodiment, the guide rail 11
A second feed screw may be provided instead. Of course, both feed screws drive the wiper 9 in the same direction and at the same speed.

FIG. 3 shows a second embodiment. In this example the wiper 9 is driven by a wire 12. The wire 12 is endlessly looped around pulleys 13 installed at both ends of the sleeve 3 and driven via a bevel gear 14. wire 12
One of the two intersection parts of the wiper 9 and the wiper 9 is fixed to each other, and the other part allows the wire 12 to pass loosely through a through hole provided in the wiper 9. The engagement relationship between the through hole and the wire 12 acts to guide the wiper 9 while maintaining its posture.

As described above, the present invention provides a wiper that is movable along the gap between the sleeve and the doctor, and is driven between copy cycles, so that it is possible to remove clogging that occurs in the gap. This can prevent white streaks from appearing in the copied image.

[Brief explanation of the drawing]

FIG. 1 is a side view of the first embodiment of the present invention, FIG. 2 is a front view thereof, and FIG. 3 is a side view of the second embodiment. 3...Sleeve, 8...Doctor, 9...Wiper, 10...Feed screw, 12...Wire.

Claims (1)

[Scope of utility model registration request] A magnetic brush developing device for an electrophotographic copying machine, characterized in that a wiper movable along the sleeve and the doctor is interposed in the gap between the sleeve and the doctor, and the wiper is driven between copy cycles.