Device for Adjusting Starting Position for Transfer-Type Electrophotographic Reproducing Apparatus Having Belt-Like Photosensitive Member

1. Field of the Invention

This invention relates to a device for adjusting the starting position of a belt-like photosensitive member for use in a transfer-type electrophotographic reproducing apparatus. More particularly, it relates to one in which the belt-like photosensitive member (hereinafter referred to as a photosensitive belt) has a joint portion, or seam, and is trained about rollers to form a photosensitive member unit, the unit being removably mounted in the main body of the reproducing apparatus.

2. Discussion of the Prior Art

In a transfer-type electrophotographic reproducing apparatus, the support of the photosensitive member is generally classified into the drum type and the belt type, either of which is adapted to be withdrawn from the main body of the reproducing apparatus for maintenance of the photosensitive member. If a photosensitive belt has a joint, i.e., is not seamless, then it is imperative to locate this joint at a particular position at the time of commencement of reproduction, so that the joint cannot be included in an image area. On the other hand, if a drum type photosensitive member has a joint (or discontinuity), proper positioning of the joint is achieved with ease by merely providing a positioning pin on the drum shaft.

A difficulty has been encountered with the belt-type photosensitive member in that withdrawal of a roller shaft from the main body of the reproducing apparatus is difficult from the viewpoint of the mechanism. For this reason, a device has been proposed, (for example, Utility Model Application No. 48-135,998 filed in Japan in 1973 by the assignee of this application) in which a photosensitive belt and a roller shaft are integrally formed into a photosensitive member unit, and this unit is removably mounted in the main body of the reproducing apparatus with a gear train serving as a drive source, which gear train is incorporated in the main body. In that device, the photosensitive belt is adjusted so as to locate its joint at a particular position beforehand while the unit is outside the reproducing apparatus and then the unit is set in place in the main body of the reproducing apparatus. Another difficulty has been encountered with that device, however, in that because the roller shaft must be connected to a drive source by way of gears, at the time of such connection it frequently arises that the position of the joint is not in accord with the position of a reproduction sequence controlling mechanism, resulting in the necessity to readjust the position of the joint.

The present invention is directed to avoiding the above-mentioned difficulties.

It is accordingly an object of the invention to provide an improved tranfer-type electrophotographic reproducing apparatus. The apparatus has an image-forming system, a photosensitive member unit mounted for withdrawal from and insertion into the apparatus, the unit containing a photosensitive belt having a seam and being trained about a plurality of rollers for rotation to at least one position in an area receiving an image from the image-forming system when reproduction is initiated, and a drive source adapted for engaging at least one of the rollers for providing the rotation, the engaging of the drive source with the one roller being conditionally enabled upon insertion of the unit into the apparatus and being disabled upon withdrawal therefrom. The improvement comprises combining the above apparatus with a device for adjusting a starting position of the belt, including a belt-position control member mounted in the unit for synchronous movement with the belt and adapted to occupy a discrete position with the seam located at a given position outside the image-receiving area, first means enabling the engaging of the drive source with the one roller in response to movement of the belt-position control member from the discrete position, means disabling the first enabling means when the control member is in the discrete position, second means enabling the engaging of the drive source with the one roller in response to initiated reproduction and means inhibiting the second enabling means, said last means being effective in the absence of the control member from the discrete position, whereby the seam is prevented from occupying the image area during reproduction and reproduction initiation is prevented when the seam is in the image area.

Description of an embodiment of the present invention will be given with reference to the accompanying drawing, in which:

FIG. 1 is an exploded perspective view of a device for adjusting a starting position according to the present invention; and

FIG. 2 is a circuit diagram.

Referring first to FIG. 1, a device for adjusting the starting position of a belt-like photosensitive member according to the present invention is generally composed of a photosensitive member unit 10, a drive source 30, a group of reproduction-controlling cams 40 and a clutch mechanism CL.

The photosensitive member unit 10 comprises a drive roller 13 and two driven rollers 14, 15 rotatably mounted on opposing side frames (not shown) which frames are mounted in the main body (also not shown) in a manner to be withdrawn therefrom (along slide rails, say), and a photosensitive belt 11 is trained about the above-mentioned drive and driven rollers, the roller axes being positioned in parallel, triangular relation to one another. Photosensitive belt 11 is rotated in the direction of the arrow shown at the right in FIG. 1, by virtue of perforations provided along each longitudinal edge 12 of the belt, which perforations are maintained in engagement with pins 16 provided at each side of drive roller 13. A mechanical clutch 18a, b comprises a pin 18a attached radially near one end of shaft 17 extending coaxially from drive roller 13. Pin 18a is adapted to disconnectably engage with a lateral projection (shown, but not numbered) on a disc 18b mounted on the end of a shaft driven by a main motor 31 (forming part of drive source 30 to be described later), so that the photosensitive member unit 10 may be set in or removed from the main body of the reproducing apparatus.

A gear 19 is mounted on extension shaft 17 in meshing relation with a gear 20 rotatably mounted in the side frame of the unit and being provided with cams 21 and 22 rigidly affixed thereto. Cam 21 has four projections or lobes 21a, 21b, 21c and 21d (not visible in FIG. 1), and cam 22 has three projections or lobes 22a, 22b and 22c. shown at 23 and 24 are respective microswitches opened and closed by cams 21 and 22, hereinafter referred to as the belt-position-adjusting cams. Both cams 21 and 22 are so arranged that projections 21a and 22a take the same angular position on the circumference of the respective cam. The number of projections 21a to 21d and 22a to 22c of the respective cams accords with the number of copies of the corresponding size which are obtainable from the entire usable surface of photosensitive belt 11. For example, in case A-4 size copy paper is being used, four sheets of copy are obtained from the photosensitive belt length, whereas three sheets of copy are obtained in the case of B-4 size copy paper, as shown respectively by the outlines in a one-dot chain line and in a two-dot chain line in FIG. 1.

First and second electromagnetic clutches CL1 and CL2 are mounted on a motor shaft 32 projecting from each side of the main motor 31 incorporated in the main body.

An array of reproduction-controlling cams 40 consists of a group of A-4 size reproduction-controlling cams 41 connected to main motor 31 through the intermediary of the second electromagnetic clutch CL2, and a group of B-4 size reproduction-controlling cams 49 connected therewith by the intermediary of reduction gears 47 and 48. Each group of reproduction-controlling cams comprises a reproduction-starting-position defining cam 42 (or 50) and a plurality of cams 44a to 44N (or 52a to 52N) which activate reproducing elements such as exposure and charging elements in response to the movement of belt 11, the cam lobes actuating respective microswitches 44, 46a to 46N and 51, 54a to 54N, thereby establishing a starting position on belt 11 and a commencement of reproduction condition for the cams.

Additionally, there are provided (only the first device being shown) a charger 55 on the upper portion of belt 11 toward the rear of unit 10, exposure means above belt 11 toward the front of unit 10, a developing device in the vicinity of drive roller 13, a transfer station adjacent belt 11 in the vicinity of driven roller 14, and a cleaning station below belt 11 near roller 15, all of which are secured to the main body of the reproducing apparatus in the positions described, so that one cycle of the reproducing process may be completed through one cycle of rotation of belt 11. Thus, for obtaining two sheets of copy through a continuous reproduction, belt 11 effects one and one-fourth rotation for A-4 size (or one and one-third rotation for the larger size copy).

The group of reproduction-controlling cams 41 effect one cycle of rotation during one-fourth rotation of belt 11, whereas the group of cams 49 undergo one cycle of rotation during one-third rotation of belt 11 because of the reduction gears 47, 48.

In FIG. 1, a joint A in belt 11 is shown behind charger 55 (in terms of the direction of the arrow) at a position which is an initial one, i.e., prior to commencement of reproduction. With joint A maintained in that position, projections 21a and 22a of belt-position-adjusting cams 21 and 22 are set at a position such that they actuate their respective microswitches 23 and 24.

Operation of the device for automatically adjusting the starting position of belt 11 will now be described in conjunction with the electric circuit shown in FIG. 2. The switch conditions shown in FIG. 2 correspond to the belt and cam positions shown in FIG. 1 and the case where the operator has selected B-4 size copies for production.

A switch 51 operated by cam 50 for use in establishing the starting position of a B-4 size reproduction is connected to the contacts NO of a normally-open switch 56. This latter switch is used in selecting the size of copying paper, i.e., either an A-4 size reproduction or a B-4 size reproduction. Conversely, a switch 44 operated by cam 42 for use in establishing the starting position of an A-4 size reproduction is connected to the normally-closed contact side NC of switch 56. The normally-open contact side NO of switch 51 is connected to a starting switch 23 establishing a starting position of belt 11 for each B-4 size reproduction, and the normally-open contact NO of switch 44 is connected to a starting switch 24 establishing a starting position on belt 11 for an A-4 size reproduction, while the normally-closed contacts NC of switches 44 and 51 are both connected to the second electromagnetic clutch CL2. The normally-open contact sides NO of starting switches 23 and 24 are both connected through a reproduction starting switch 57 to an input terminal 59 of a control circuit 58, and the normally-closed contact sides NC of starting switches 23 and 24 are connected to the first electromagnetic clutch CL1.

Shown at 60 is an output terminal of the control circuit 58, the output terminal being connected through diodes 61, 61' to the first and second electromagnetic clutches CL1 and CL2, respectively.

In operation, a power switch (not shown) is thrown to energize main motor 31 and other circuits in known fashion and, say, the selection switch 56 is set to the position for effecting an A-4 size reproduction (i.e., opposite to that shown in FIG. 2). At this time, if the group of cams 41 are not located at the starting position where projection 43 of starting-position-defining cam 42 is in engagement with switch 44 (i.e., if they are not located as shown in FIG. 1), this will cause electric current to flow through the normally-closed contact NC (switch 44 then being in the position opposite to that shown in FIG. 2) to activate the second electromagnetic clutch CL2, whereby drive from main motor 31 is transmitted to the group of cams 41, thereby rotating same. When the group of cams 41 assume the start position (that shown in FIG. 1), the projection 43 of starting-position-defining cam 42 pushes the actuator arm of start switch 44, whereby the normally-closed contact NC of switch 44 is opened, thereby interrupting electric current to the second electromagnetic clutch CL2, such that the group of cams 41 stop at that position.

On the other hand, if the seam A of sensitive belt 11 is not at the starting position, i.e., if the lobe 22a (or one of the other lobes 22b, c, d) of belt-position-adjusting cam 22 is not in engagement with starting switch 24, electric current will flow through the normally-closed contact side NC of switch 24 to the first electromagnetic clutch CL1, thereby causing main motor 31 to drive shaft 17 (through mechanical clutch 18a, b) whereby belt 11 is rotated. When belt 11 arrives at the starting position shown in FIG. 1, for example, then by virtue of gears 19, 20 the lobe 22a of belt-position-adjusting cam 22 simultaneously arrives at a point where it engages starting switch 24, with the result that normally-closed contact NC is opened to interrupt thereby the electric current to first electromagnetic clutch CL1, such that belt 11 stops at the starting position shown in FIG. 1.

At this time, both the group of cams 41 and also the belt 11 have assumed a starting position for an A-4 reproduction. If the reproduction starting switch 57 is then actuated, a signal is fed through the NO contacts of switches 44 and 24 -- recalling that for purposes of this description the operator was assumed to have selected A-4 reproduction size and thus switch 56 is in the position opposite to that shown in FIG. 2, i.e., the NC contacts are closed -- to the input terminal 59 of control circuit 58, thereby commencing reproduction.

When reproduction starts, electric current flows from the output terminal 60 of circuit 58 through the diodes 61, 61' to activate the first and second electromagnetic clutches CL1 and CL2, causing belt 11 and the groups of cams 41 and 49 to rotate. Since the selection switch 56 has been set for A-4 size reproduction, for purposes of this description, the control circuit 58 is activated (see FIG. 1) in known fashion according to the opening and closing of switches 46a to 44N in the group of cams 41, so that charging, exposure, developing and transfer signals are sequentially given to corresponding elements, reproduction thus being achieved.

Toward completion of reproduction, electric current flowing from output terminal 60 in control circuit 58 to the first and second electromagnetic clutches CL1 and CL2 is interrupted. Consequently, if cams 41 and belt 11 are not at a starting position, electric current flows through the copy-size selection switch 56 and the starting-position switches 44 and 51 to the first and second electromagnetic clutches CL1 and CL2. When belt 11 and the group of cams 41 come to a starting position, electric current to the first and second electromagnetic clutches CL1 and CL2 is cut off, thereby stopping belt 11 and cams 41 in those positions, as set forth in the foregoing. Thus, belt 11 and starting-position switches 44 and 51 remain in respective starting condition until a subsequent reproduction commences.

If selection switch 56 is set for selecting a B-4 size copy, reproduction is achieved through the same procedures as described.

In the above-described reproduction, because one cycle of the reproducing process is completed through one cycle of rotation of photosensitive belt 11, the joint A of belt 11 would have rotated through one and one-fourth rotation after two successive copyings of A-4 size. In order to effect a B-4 size reproduction at that time, the joint must be moved out of the B-4 imaging area it occupies, and accordingly reproduction of B-4 size is initiated only subsequent to rotation of joint A to the closest optimum position for B-4 size reproduction. The rotation is achieved by virtue of switch 23 being in normally-closed condition such that clutch CL1 is energized through the NO contacts of copy-size selection switch 56 and B-4 size reproduction-starting-position-defining switch 51 (condition as shown in FIG. 2). The NC contacts of switch 23 are in a condition opposite to that shown in FIG. 2 because belt 11 stopped at a position where A-4 cam 21 for adjusting the position of belt 11 was effecting control.

As is apparent from the foregoing, according to the present invention, the photosensitive belt 11 and groups of reproduction controlling cams 41, 49 are connected to the drive source 30 by means of separate clutches CL1, CL2. Even if photosensitive belt 11 and the groups of reproduction controlling cams 41, 49 are initially in an improper position, both are automatically shifted to a normal start position. Inasmuch as belt 11 is trained about the unit 10 with its joint A located at a starting position common to various size reproduction, which position is behind the charger 55 (when viewed as in FIG. 1), and the lobes 45a-45N of the element-operating cams 44a-44N, etc. aligned with each other assume a position to operate respective switches, even if there is a displacement in the relative positions of cams 41, 49 and belt 11 at the time when photosensitive unit 10 drivingly engages its mechanical clutch 18a, 18b, there is no necessity for manual re-adjustment of the position of belt 11 and cams 41, 49, unlike the conventional device. Furthermore, since belt 11 is trained about rollers 13-15 with unit 10 removed from the main body of the reproducing machine, this facilitates adjustment of the position of joint A and that of the respective reproduction-controlling cams 41, 49.

In the embodiment described, reproduction in the A-4 size and the B-4 size are exemplified. The device of the present invention is intended for a reproducing apparatus in which either A-4 size reproduction or B-4 size reproduction is effected. If the reproducing apparatus is of the type in which the sensitive belt stops at a given position for every cycle of reproduction (for example, in a position behind the charger), it suffices to provide only a single-sheet reproduction cam with a single lobe.

It should be understood that the embodiment described above is merely illustrative of the principles of the invention. Many modifications may be made without departure from the spirit and scope of the invention, e.g., the reproduction-controlling system could contain a shift register in place of some of the multiplicity of cams disclosed. Accordingly, the spirit and scope of the invention are as set forth in the following claims .