This invention relates to toner recovery devices for electrostatic copying machines, particularly, to apparatus for supplying toner recovered from the surface of a photosensitive body to a developing device.
In an electrostatic copying machine, the toner remaining on the surface of a photosensitive drum after the transcription step is recovered in general and supplied again to a developing device in an effort to economize on toner. In many cases, an auger formed of an elastic material such as a plastic material or rubber is used as the means for transferring the recovered toner. For example, a container receiving the recovered toner houses a first auger which transfers the recovered toner toward one edge of the photosensitive drum. Naturally, the axis of the first auger is parallel with the axis of the drum. Also, a second auger housed in a duct further transfers the toner to a toner supplying device which supplies toner to the developing device. What should be noted is that the axis of the second auger is inevitably rendered perpendicular to the axis of the first auger by the relative locations of the toner container and the toner supplying device. It follows that, if the driving means of the photosensitive drum is utilized for driving the second auger for the purpose of cost reduction, it is necessary to provide a special transmission mechanism between the first and second augers, failing to achieve a satisfactory cost reduction.
In order to avoid using the transmission mechanism, it has been proposed to use a sharply bent single auger formed of an elastic material in place of the first and second augers mentioned above. In this case, however, the outer surface of the auger is brought into contact with the inner surface of the duct housing the auger, because of the elasticity of the auger. Naturally, to the toner held between the auger and the duct is compacted, resulting in formation of toner particles too large to be used again as the developing agent.
Incidentally, it is a matter of high importance to transfer the recovered toner from the toner container to the toner supplying device efficiently in order to enable the cleaning means, e.g., fur brush, to recover efficiently the toner remaining on the photosensitive drum.