Belt conveyor system comprising a mesh belt and a sheet conveyor system for conveying sheets in a reprographic apparatus

Abstract

Belt conveyor system comprising: an endless mesh belt, the belt having a mesh structure and having edge areas at the lateral sides, a drive mechanism drivable by a drive motor to rotate the belt, and a steering roller for steering the lateral position of the belt, wherein an edge area comprises a band running substantially parallel to the lateral sides, the band comprising an elastic filler being provided inside the mesh structure, the elastic filler being discernible from the mesh structure, and wherein the belt conveyor system further comprises a band position detector for detecting the lateral position of the band.

Claims

1. A belt conveyor system comprising: an endless mesh belt, the belt having a mesh structure and having edge areas at the lateral sides; a drive mechanism drivable by a drive motor to rotate the belt; and a steering roller supporting the belt and arranged for steering the lateral position of the belt, wherein an edge area comprises a band running substantially parallel to the lateral sides, the band comprising an elastic filler being provided inside the mesh structure, the elastic filler being discernible from the mesh structure, and wherein the belt conveyor system further comprises a band position detector for detecting the lateral position of the band.

2. The belt conveyor system according to claim 1, wherein the filler is substantially opaque and the band position detector comprises a light source and a light detector positioned on opposing sides of the band and wherein depending on the lateral position of the belt light from the light source is substantially blocked or not by the band.

3. The belt conveyor system according to claim 1, wherein the band position detector comprises a light source and a light detector positioned on the same side of the band and wherein depending on the lateral position of the belt light from the light source is substantially reflected to the light detector.

4. The belt conveyor system according to claim 3, wherein: the filler is substantially reflective, or the filler is substantially non-reflective and a substantially reflective surface is provided at the side of the mesh opposite the light detector.

5. The belt conveyor system according to claim 2, wherein the light detector comprises an array of light sensitive elements positioned along at least part of a lateral axis of the belt.

6. The belt conveyor system according to claim 1, wherein the filler material does not extend outside the mesh structure.

7. The belt conveyor system according to claim 1, further comprising a suction plate disposed along at least part of the surface of the belt and comprising a suction area provided with suction holes, and wherein the edge area comprising the band does not overlap with the suction area.

8. The belt conveyor system according to claim 1, wherein both edge areas comprise a band.

9. The belt conveyor system according to claim 8 wherein the two bands are positioned substantially symmetrical in the belt.

10. The belt conveyor system according to claim 1, wherein the filler comprises rubber.

11. The belt conveyor system according to claim 1, wherein the belt is seamless.

12. The belt conveyor system according to claim 1, specifically arranged for conveying sheets of registration media in a reprographic apparatus.

13. A reprographic apparatus comprising the belt conveyor system according to claim 12.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying schematical drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

(2) FIG. 1 is a diagram of an embodiment of a belt conveyor system according to the present invention;

(3) FIG. 2 is a diagram of an embodiment of a belt for use in the belt conveyor system of FIG. 1;

(4) FIG. 3 is a diagram of a detail of an edge of the belt of FIG. 2;

(5) FIG. 4 is a diagram of an embodiment of a band position detector for use in the belt conveyor system of FIG. 1; and

(6) FIGS. 5A-D and 6A-C are diagrams showing various configurations of band position detectors for use in the belt conveyor system of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS

(7) The present invention will now be described with reference to the accompanying drawings, wherein the same reference numerals have been used to identify the same or similar elements throughout the several views.

(8) In one embodiment a belt conveyor system 100 (FIG. 1) comprises a conveyor belt 110. The belt 110 is endless in the sense that it does not have a leading edge, nor a trailing edge. An endless belt may be formed by welding the leading edge and the trailing edge together resulting in a seam running over the width of the belt at the location where the leading and trailing edges have been welded together. In general the properties of the belt at the seam differ from the properties of the belt at other locations, for example, the belt thickness may be different due to overlap of the leading and trailing edges, and the stiffness of the belt may be different due to this same overlap, but also as a result of the welding process.

(9) In sheet conveyor systems seamless belts 110 are preferred. Seamless belts are less subject to out-of-plane buckling. There is no danger of sheets being located on the seam, which increases sheet holding and reduces print defects. Furthermore, belt conveyor systems with seamless belts are less susceptible to wear.

(10) Seamless belts may be manufactured by weaving tube-like forms and cutting the tube in a plane perpendicular to the longitudinal axis. Alternatively, an endless belt may be formed by taking a rectangular shaped mesh and welding two opposing sides together thereby forming a loop.

(11) The belt 110 is a mesh belt comprising a woven fabric. In this specific embodiment the mesh is woven from threads with a thickness of approximately 0.22 mm and with a thread density of 12 threads per cm. One particular belt has a length of 1911 mm, a width of 420 mm, and a thickness is 0.5 mm. The threads comprise polyphenylene sulphide (PPS). Such a mesh belt has proven to be suitable for a sheet conveyor system in a reprographic apparatus. Alternatively, polyester may be used although PPS is preferred as the latter material is self-extinguishing.

(12) The belt 110 is held under tension in a four roller configuration, namely a first roller 122, a steering roller 124, a tension roller 126, and a drive roller 128. The steering roller 124 is a pivoting steering roller that moves the belt in a lateral direction by using the helix principle. The tension roller 126 is movable in the direction of at the one hand the steering roller 124 and the drive roller 128 and at the other hand away from these rollers. By moving the tension roller 126 and adjusting the distance to the drive roller 128 and the steering roller 124, the tension of the belt can be controlled. The drive roller 128 is driven by a motor (not depicted) and makes the conveyor belt run in an operational direction depicted by arrow 112.

(13) The mesh belt runs over a vacuum box 130. During operation a partial vacuum exists in the vacuum box 130. The surface of the vacuum box 130 facing the mesh belt 110 (called the suction plate) is perforated. Due to the partial vacuum, sheets on the belt 110 are held against the belt 110 between the first roller 122 and the drive roller 128 and move together with the belt 110 in the direction of the arrow 112. The suction plate comprises ABS with a Teflon coating. In combination with a mesh belt 110 comprising threads of PPS a low friction between suction plate and mesh belt 110 is obtained.

(14) The vacuum box 130 is sub-divided in three vacuum chambers 132, 134, and 136. The suction plate of the vacuum chamber 132 is designed to have a high air flow in order to reliably receive sheets from a preceding sheet transportation unit, especially in the case of short sheets. When a sheet is in the vicinity of the belt 110 in the area of the vacuum chamber 132 it is forced towards the belt 110 by the high air flow. The vacuum chamber 134 is held on a moderate partial vacuum to prevent cockling of the sheet and ensure a reliable transport of the sheet. The vacuum chamber 136 is designed similar like vacuum chamber 132. A high pressure ensures reliable delivery of especially short sheets to the next sheet transportation unit.

(15) The use of a mesh belt 110 ensures a better spreading of the partial vacuum underneath the sheets compared to perforated foil belts. Furthermore, a mesh belt 110 does not suffer from the problems of misalignment between the perforations in the perforated foil belt and the perforations in the suction plate, which systems comprising a perforated foil belt attempt to mitigate by milling grooves in the suction plate to distribute the partial vacuum.

(16) FIG. 2 shows a top view of the belt 110. The mesh belt 110 comprises a mesh structure. The mesh structure comprises a woven fabric. The majority of the belt 110, specifically the central area 114 (relative to the lateral direction) of the mesh structure has an open structure. This causes the vacuum to be substantially evenly distributed underneath a sheet being held on top of the belt. Due to this open structure it is not necessary for the suction plate of the vacuum box 130 to have a milled structure for distributing the partial vacuum as is necessary with perforated foil belts. As the dominant air restriction is in the suction plate and not in the belt 110, there is little friction between the belt 110 and the suction plate in the areas where no sheets are present. The edge areas of the belt 110 are each provided with a band 116. This band comprises of a non-transparent, flexible filler material that is provided inside the mesh structure.

(17) FIG. 3 shows a detail of the edge area of the belt 110. The mesh belt 110 comprises a weft 113 and warps 115. At the edge a filler material 117 has been provided in the mesh structure. The filler material 117 is made of a non-transparent, flexible material, such as rubber. For example, rubber granulate welded together. In image reproducing apparatuses, such as copiers and printers, a granulate may be disadvantageous though due to pollution of the apparatus by detached granulates. This may be solved by using smearing or injecting latex into the mesh structure, scraping off the superfluous latex, and vulcanising the latex. Other elastomers are suitable too though.

(18) The edge of the mesh belt (to the left of the band of filler material 117, has been cut using ultrasonic cutting techniques. The advantage of using ultrasonic cutting is that the warps 115 are welded together in the cutting process preventing unravelling of the mesh structure.

(19) FIG. 4 shows a cross-sectional view of the belt 100 and the band position detector. The mesh structure comprises the weft 113 and the warps 115 (in FIG. 4 only a single warp 115 is visible due to the cross-sectional view). Due to the open structure of the mesh, the central area 114 (that is: the whole area between the two bands 116) is substantially transparent. However, in the edge areas the filler material 117 being non-transparent is substantially non-transparent. The band position detector comprises a light source 440. Light from the light source 440 propagates in different directions shown by the arrows 442 and 444. Due to the non-transparency of the filler material 117 and the dense packing of the granules, the band in the edge area 116 is substantially non-transparent and light in the direction of the arrow 442 is either reflected or absorbed and does not propagate through the filler material 117, while light travelling in the direction of arrow 444 propagates without being obstructed by the filler material 117.

(20) A light detector 450 comprises an array of light sensitive elements 452 (such as a linear CCD). It is provided at the opposite side of the belt 110 in order to detect where light is obstructed by the filler material 117. Light travelling in the direction of the arrows 442 is obstructed by the filler material 117. Consequently, the light sensitive elements 452 at the opposite side of the filler material 117 in the band sense a low level of light. Light travelling in the direction of arrow 444 is not obstructed by the filler material 117 and can reach the light sensitive elements 452. These light sensitive elements 452 will sense a high level of light. By comparing the light levels sensed by the lights sensitive elements 452, the band position detector is able to determine the position of the band above the light detector 450 and therewith the lateral position of the belt, as the areas of high and low light levels will move along the array in accordance with the lateral movement of the belt.

(21) By appropriately commanding the steering roller 124, the lateral position of the belt 110 may be controlled, for example by employing a traditional feedback controller.

(22) In a rather simple, alternative embodiment a light detector 450 with only a single light sensitive element 452 is used, for example in the position that is during normal operation at the opposite side of the band (with regard to the light source 440) such that the filler material 117 obstructs the light. When the belt 110 moves laterally, at some point the band is no longer above the light sensitive element 452, and the band position detector will detect that the band, and therewith the belt 110, has moved too far off in the lateral direction. Drawback of this embodiment is that the single light sensitive element 452 by itself is not able to detect if the lateral position of the belt 110 deviates in a negative or a positive direction.

(23) This disadvantage can be overcome by using at least two light detectors 450, or alternatively a single light detector 450 with two or more light sensitive elements 452. These two light detectors 450 may be positioned in various configurations, for example (FIGS. 5A-D and 6A-C): both behind the normal position of the band (with regard to the light source 440) such that both light detectors 450 normally detect a low light level (FIG. 5A), one behind the normal position of the band and one outside the normal band area, beyond the distal edge of the band (FIG. 5B), one outside the normal band area and inside the central area 114, and the other behind the normal position of the band (FIG. 5C), both outside the band area, one beyond the distal edge of the band, and one inside the central area 114 (FIG. 5D), and
in case both edge areas are provided with a band one light detector 450 for each band: both behind the normal position of their respective bands (FIG. 6A), both outside their respective band areas, beyond the respective distal edges of the band (FIG. 6B), and both outside their respective band areas and inside the central area 114 (FIG. 6C).

(24) Alternative methods for detecting the lateral position of the band is by making use of the reflectiveness or non-reflectiveness of the filler material 117 by placing the light detector 450 at the same side of the belt 110 as the light source 440. In such an embodiment the background of the belt 110 should distinguish from the filler material 117 by having the opposite property. As an alternative to a non-reflective background, no background may be present in the sense that opposite the position of the band there is no surface near the belt resulting in the light from the light source 440 dispersing into empty space if not reflected by the filler material 117.

(25) Furthermore, instead a combination (or combinations) of a light source 440 and multiple light sensitive elements 452, it is also possible to use multiple light sources 440 and a single light sensitive element 452 together with some features to distinguish between the light from the different light sources 440, such as logic to excite the light sources 440 at distinctive moments in time.

(26) Detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. In particular, features presented and described in separate dependent claims may be applied in combination and any advantageous combination of such claims is herewith disclosed.

(27) Further, the terms and phrases used herein are not intended to be limiting; but rather, to provide an understandable description of the invention. The terms a or an, as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language). The term coupled, as used herein, is defined as connected, although not necessarily directly.

(28) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.