EP0201109A1

EP0201109A1 - A sheet turning conveyor

Info

Publication number: EP0201109A1
Application number: EP19860106443
Authority: EP
Inventors: Masanori Katayama; Kenjiro Tanabe; Masao Fukushima; Takeshi Sugata
Original assignee: Dainippon Screen Manufacturing Co Ltd
Current assignee: Dainippon Screen Manufacturing Co Ltd
Priority date: 1985-05-10
Filing date: 1986-05-12
Publication date: 1986-11-12
Also published as: EP0201109B1; DE3665229D1

Abstract

A sheet turning conveyor includes a rotary suction drum (26) which comprises suction surfaces (29) and circumferential recesses receiving belts (27), the suction surfaces and the belt surfaces being flush with each other so as to be complementary to the entire drum surface. Each of the suction surfaces is formed with a series of pores (31) arranged along the circumference of the drum and at least two adjacent pores of the suction surface are connected by a groove which allows air to pass between the connected pores.

Description

THE PRESENT INVENTION relates to a sheet turning conveyor adapted for use in combination with an electro-photographic copying machine, and more particularly, a sheet turning conveyor for such use whereby the direction of movement of a sheet material, such as paper, is turned. Whilst its direction of movement is being changed the sheet is effectively held on the conveyor by means of suction.
Sheet turning conveyors employing a rotary suction drum are well known. The suction drum is provided with a number of pores through which a negative pressure produced inside the drum acts so that a differential pressure is produced between outside and inside the drum.
However, the known rotary suction drum has a major disadvantage in that the sheet is suddenly released from the drum surface under inadequate distribution of the suction force. This is caused by the fact that the sheet is quite likely to be placed on the surface of the suction drum with its advancing edge portion positioned between adjacent pores of the drum surface. At such a place no suction is exerted on a loading portion of the sheet, thereby causing it to peel off the drum surface. This is likely to bring about troubles in conveying the sheet.
In addition, the known rotary suction drum is rotated by means of a driving roller through a belt. In other words, the drive is imparted to the suction drum through an intermediate means, such as a driving roller and a belt. When the suction force is moderate, no problem arises, but when it is fairly large, the sucking force tends to act as a brake on the transferring sheet at the moment when it is released from the drum surface. This results in the inefficient conveyance of the sheet.
The present invention aims to solve the problems pointed out with respect to the known sheet turning conveyor, and has for its object to provide a sheet turning conveyor in which the sheet is securely held on the drum surface even when it is placed out of registry with the pores.
Accordingly the present invention provides a sheet turning conveyor including a rotary suction drum which comprises suction surfaces and circumferential recesses for receiving conveying belts on which the sheet travels, in which conveyor the suction surfaces and the belt surfaces are flush with each other, each of the suction surfaces includes pores arranged around the circumference of the drum, and at least two adjacent pores of a suction surface are connected by a suction groove allowing air to communicate between the connected pores.
In order that the invention may be readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a perspective view showing a sheet turning conveyor embodying the present invention;
Figure 2 is a perspective view showing an electro-photographic copying machine incorporating the sheet turning conveyor of Figure I;
Figure 3 is a cross-sectional view taken along the line III-III in Figure 2;
Figure 4 is a fragmentary view on a larger scale showing the portion indicated by (IV) in Figure 3; and
Figure 5 is a front view showing a modified suction drum for a sheet turning conveyor embodying the present invention.

As shown in Figures 2 and 3, an exemplary electro-photographic copying machine comprises a centrally located control panel I, an original scanning section 2 to the left of the panel I, and an image recording section 3 to the right of the panel I. An original to be copied is placed on a plate 4, the original being fed into the scanning section 2 in which the transferring original is exposed to light and received by a receiver 5. The image in the original is projected onto a sensitive drum 7 by means of an optical system 6, thereby producing an electrostatic image thereon. The latent image is rendered visible by a toner supplied by a toner developing unit 8 and the resulting toner image is recorded on a record paper which is then fed to a receiving plate 9.
Figure 3 schematically shows the internal structure of the image recording section 3, the detailed description of which will be given below:

Distributed around the sensitive drum 7 are an electrifier 10, a deelectrifier 11, an exposing section 12, the toner developing unit 8, a paper supplying section 13, a toner transfer unit 14, a paper separating unit 15, a second deelectrifier 16 for deelectrifying the entire surface of the sensitive drum 7, and a cleaning unit 17.

The paper supplying section 13 includes feed paths 19 and 20 which correspond to the respective rollers arranged so as to be in accord with the selected paper from rolls 18. The reference numeral 21 denotes a junction where the two paths 19, 20 meet. The reference numeral 22 denotes a manual paper supplying section. The paper is cut by means of a cutter unit 23 to a desired length.
The toner image is transferred to the record paper by means of the toner transfer unit 14, which paper is then subjected to suction on its back surface by the paper separating unit 15, thereby releasing it from the drum 7. Thereafter the paper is fed to a heat setting unit 25 by means of the turning conveyor 24. In this way the toner image is fixed on the paper and the paper is fed to the receiving plate 9.
The turning conveyor 24 includes belts 27 on which the paper travels and which run around a rotary drum, which is a member of the paper separating unit 15, and a suction drum 26. The direction of movement of the paper is turned as it advances by means of the turning conveyor 24, the paper being held on the surface of the drum 26 under suction as its direction movement is turned. The reference numeral 28 denotes a fan whereby the paper is pressed onto the surface of the belts 27 under air pressure.
As shown in Figures and 4, the suction drum 26 includes a plurality of circumferentially extending suction surfaces 29 separated by circumferential recesses in which the belts 27 are fitted in such a manner that the suction surfaces 29 and the belt surfaces are on the same level', as best shown in Figure 5. The suction surfaces each have a series of pores 31 through which suction is exerted on the paper placed on the drum by a negative pressure produced within the drum. In the embodiment shown in Figure I the pores 31 are arranged in two rows and spaced along the circumference at regular intervals. The adjacent pores 31 are conencted to each other by means of a suction groove 32 which is adapted to allow the suction force to communicate evenly between the connected pores. Thus the paper can be subject to an equally distributed suction force from below. This will be of particularly advantage when the paper is placed inappropriate with its advancing leading or top edge spaced away from the pores. The suction force exerted via the grooves 32 help to secure the paper adequately.
However, when the sucking force is excessively great, the paper will become difficult to release from the drum, which could result in inefficient conveyance of the paper. To avoid this difficulty a shaft of the suction drum 26 is provided at an end with a sprocket 34 with which a drive chain 35 is engaged. This chain 35 is connected to an electric motor 26 through a device which is constructed so that the suction drum 26 operates in synchronism with the sensitive drum 7.
The number of the rows of pores is not limited to two but can be more than that for some or all of the suction surfaces 29.
In the modified example shown in Figure 5 the grooves 32 interconnecting the pores are arranged differently and each groove is produced so as to connect staggered pores 31 in the two rows of pores in each suction surface 29. In addition, the adjacent suction surfaces 29 have the grooves 32 oppositely angled.
The features disclosed in the foregoing description, in the claims and/or in the accompanying drawings may, both separately and in any combination thereof, be material fo: realising the invention in diverse forms thereof.

Claims

I. A sheet turning conveyor including a rotary suction drum which comprises suction surfaces and circumferential recesses for receiving conveying belts on which the sheet travels, in which conveyor the suction surfaces and the belt surfaces are flush with each other, each of the suction surfaces includes pores arranged around the circumference of the drum, and at least two adjacent pores of a suction surface are connected by a suction groove allowing air to communicate between the connected pores.
2. A sheet turning conveyor according to claim 1, wherein suction grooves extend from one pore of the suction surface to another in a ring around the circumference of the drum surface.
3. A sheet turning conveyor according to claim I, wherein the suction surface has a pair of circumferential rows of pores and suction grooves interconnect staggered pores in the two rows.
4. A sheet turning conveyor according to claim 3, wherein adjacent suction surfaces hae oppositely angled suction grooves.
5. A sheet turning conveyor according to any one of claims I to 4, wherein the shaft of the suction drum is connected to a driving means so that the suction drum drives the conveying belts fitted in the circumferential recesses in the drum surface.
6. A sheet turning conveyor according to claim 5, wherein the shaft of the suction drum is connected to the driving means through an endless chain.
7. A sheet turning conveyor according to any preceding claim, wherein the suction surfaces and the belt receiving recesses are alternately disposed across the width of the drum surface.