JPH03138246A - Sheet feed device - Google Patents

Abstract

PURPOSE:To prevent a record sheet from staining by a sheet feed roller due to a worn roller while the record sheet is on standby by decreasing the contact pressure of the sheet feed roller in closing a shutter to make the record sheet on standby temporarily more than in opening it. CONSTITUTION:While a shutter 8 is in a closed condition and a record sheet is on standby, a load applying member 11 is placed on the upper end of a rising piece 8a in the shutter 8, so the load applied to the shaft of a driven roller 7b is relieved. As a result, concerns such as wear of the sheet feed roller and dirtiness of the record sheet is eliminated. Since the whole load is applied to the shaft of the driven roller 7b through the load applying member 11 by a spring 12 when the shutter 8 is opened by the second sheet feed signal, the contact pressure between the driven roller 7a and the driven roller 7b increases, thus the record sheet being fed completely.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a paper feeding device suitable for image recording devices and the like.

(Prior art) In image recording devices such as electrophotographic copying machines and printers that record images using an electrophotographic process, an electrostatic latent image formed on a rotating photoreceptor drum is developed and then transferred to recording paper. At this time, the recording paper pulled out from the cassette is stopped in the middle of -, H so that the leading edge of the recording paper coincides with the leading edge of the =T visual image formed on the photoreceptor drum L, and is kept on standby.
The paper is re-fed toward the transfer position at a predetermined timing in synchronization with the rotation of the photosensitive drum.

In conventional image recording apparatuses, the recording paper is temporarily placed on standby in front of the transfer position.

A set of rollers or shutters called a registration roller are used. Registration rollers are normally stopped and
The leading edge of the recording paper is placed in a standby state against this roller, and then rotated by a refeed command to send the recording paper forward.

On the other hand, the shutter moves in and out of the recording paper conveyance path, and when the shutter or the conveyance path is out, the leading edge of the recording paper hits the shutter and is stopped, and when the shutter is retracted, the recording paper is moved forward by the paper feed roller. Sent out. A solenoid is used to move the shutter in and out.

By the way, this type of paper feeding device with one shutter type is r,
Many printers are designed to record paper using the paper feed mode, or because it is difficult to match the timing of manual paper feed and the timing of image formation with the manual paper feed mode, the L paper feed sensor detects when the recording paper has been manually fed. Since image formation is started after detection, the recording paper is held by the shutter for a long time. During this waiting period, the paper feed roller rotates while applying a moderate amount of pressure to the recording paper and slipping, which causes problems such as i'iJt and staining of the recording paper due to roller marks.

(3?Another purpose and structure) The present invention has been made in view of the following two points.The present invention aims to prevent wear and tear of rollers and staining of recording paper during standby, and to achieve this purpose. Therefore, when the shutter is closed, the pressing force of the paper feed roller is made smaller than when the shutter is open.

(Example) The present invention will be explained below based on the drawings.

FIG. 1 shows the main parts of a paper feeding device of an image recording apparatus according to the present invention. In the figure, l is a photosensitive drum that forms a static latent image, 2 is a transfer pole, and 10 is a separation pole. . Charging electrodes, developing devices, cleaning devices, etc. necessary for normal electrophotographic processes are omitted.

Reference numeral 11 denotes a cassette in which a large number of recording sheets P are stored, and a moon-shaped roller 5 is provided at the top of the cassette 11 to feed out the uppermost recording sheet.
a second paper feed roller 12, a second paper feed roller 13, and a shutter 1 immediately downstream thereof for stopping and waiting the recording paper.
4 is provided. A paper feed sensor 15 is located immediately upstream of the second paper feed roller 13 and detects the presence or absence of recording paper.

When the half-moon roller 5 rotates in synchronization with the recording operation, the topmost recording paper P stored in the cassette 11 is fed out, and when the leading edge reaches the first paper feed roller 12, this first one is fed out. The paper is conveyed by one paper feed roller 12 . When the leading edge of the recording paper is caught on the second paper feeding roller 13 and hits the shutter 14, the recording paper stops and enters a standby state.

After that, the shutter 1 is moved at a timing when the leading edge of the recording paper coincides with the leading edge of the visible image formed on the photoreceptor tram l.
4 is moved downward to open the conveyance path, and the recording paper is fed to the transfer section.

FIG. 2 shows the main parts of the paper feeding device according to this fi IJJ.

In the figure, 7 is a second paper feed roller, which consists of a drive roller 7a whose surface is made of rubber material and driven by a drive source (not shown), and a driven roller 7b made of resin and which rotates in pressure contact with this drive roller 7a. A downward force by a spring 12 is applied to the shaft of the driven roller 7b by a load applying member 11 made of metal or resin and rotatable about a shaft 10.

On the other hand, the shutter 8 is driven by a shaft 13 by a drive mechanism (not shown).
It is designed to be able to take two positions, a solid line position (shutter closed position) and a broken line position (shutter closed position), by rotating in the direction of the arrow about the fulcrum.

What is important here is that when the shutter 8 is in the closed position as shown in the figure, it rests on the tip of the load adding member 11 or the tip of the upright piece 8a of the shutter 8 at point A. The height of the rising piece 8a or the position of point A is set so that the pressing force between the driving roller 7a and the driven roller 7b by the load applying member 11 is slightly smaller than the pressing force at the shutter idle position l. There is. The degree to which the pressure force of the paper feed roller ruff when the shutter is closed is smaller than the pressure force when the shutter is open depends on factors such as the wear of the paper feed roller ruff caused by the recording paper when the shutter is closed and the degree of dirt on the recording paper caused by the paper feed roller ruff. It can be decided by experimental investigation.

In this way, when the shutter 8 is in the closed position t and the recording paper is waiting, the load applying member 11 is placed on the upper end of the rising piece 8a of the shutter 8, so that the load applied to the shaft of the driven roller 7b is relieved. As a result, the pressing force between the driving roller 7a and the driven roller 7b is weakened, and as a result, problems of wear and tear of the paper feed roller and staining of the recording paper are eliminated.

When the shutter 8 is opened in response to the paper refeeding signal, the entire load is applied to the shaft of the driven roller 7b by the spring 12 via the load applying member 11, so the pressing force between the driving roller 7a and the driven roller 7b increases. This ensures that the recording paper is fed.

In the above embodiment, in order to change the load applied to the driven roller 7b that constitutes one of the paper feed rollers, a configuration is adopted in which the load applying member 11 is placed on or removed from a part of the shutter 8. Such a configuration has the effect of simplifying the structure. However, in the present invention, it goes without saying that the shutter 8 may not be used and the load applied to the driven roller 7b may be independently changed using another configuration.

(Effects of the Invention) As explained above, in the present invention, when the shutter for temporarily holding the recording paper is closed, the pressing force of the paper feed roller is made smaller than when it is opened, so that the recording paper This eliminates the possibility of the recording paper being worn out by the paper feed roller or getting stained by the roller while it is on standby.

[Brief explanation of the drawing]

FIG. 1 is a transport route diagram of a paper feeding section of an image recording apparatus, and FIG. 2 is a schematic line ['2I] showing the main parts of the paper feeding device according to the present invention. l...Photosensitive drum, 4...Cassette, 5...Half-moon roller, 6...First paper feed roller, 7...Second paper feed roller, 8...Shutter, 117Jin addition Member, 12... spring

Claims (2)

[Claims] (1) A paper feed roller that feeds the recording paper to a transfer position, and a shutter that is provided immediately downstream of the paper feed roller and takes an open position that allows the recording paper to pass through and a closed position that prevents it from passing; A paper feeding device comprising a pressure bonding change means for reducing the recording paper pressing force of the paper feeding roller when the shutter is in the closed position compared to when the shutter is in the open position. (2) The pressing force changing means comprises a load applying member that applies pressure to the support shaft of the paper feed roller, and when the shutter is closed, a part of the load applying member rests on a part of the shutter. Paper feed device as described.