GB2167033A - Foraminous belt conveyor - Google Patents

Abstract

A foraminous endless bet (17) is trained over a set of pulleys so that it forms a first reach and a second reach which is twisted through 180 degrees. One side of the first reach is adjacent to a suction chamber (16) and the other side of the first reach attracts particles of tobacco which form a growing tobacco stream. The 180-degree twist of the second reach enables the belt to relieve itself of minute solid particles which adhere to the other side of its first reach because the other side of the first reach becomes the one side of such reach during next travel along the stream building zone and so forth. Moreover, the twist contributes to more uniform wear upon the belt and imparts to the belt superior pulley-tracking properties. <IMAGE>

Description

SPECIFICATION Foraminous belt conveyor The present invention relates to conveyors in general, and more particularly to improvements in conveyors of the type wherein an endless belt is trained over two or more pulleys or otherwise configurated guide means. Still more particularly, the invention relates to improvements in belt conveyors of the type wherein the belt is foraminous, either entirely or in part, and is or can be utilized for the transport of particulate material in tobacco processing plants.

In many presently known tobacco processing plants, the machines which are used for the making of continuous fillers of tobacco and/or filter material employ an endless belt conveyor having an elongated lower reach which travels below a suction chamber and is disposed at a level above a duct serving to supply particles of tobacco or other fibrous material. The thus supplied material gathers at the underside of the lower reach and forms a growing stream which is thereupon trimmed, draped into a web of cigarette paper or other suitable wrapping material, converted into a continuous rod wherein the wrapping material forms a tube around a fibrous filler, and subdivided into rod-like sections of unit length or multiple unit length.The duct receives tobacco shreds or otherwise configurated particles of fibrous material from a suitable distributor serving to facilitate the formation of a continuous and highly homogeneous stream which is ready to be trimmed and thereupon wrapped or to be wrapped without any trimming.

The material which is fed to the underside of the lower reach of the just discussed endless foraminous belt often contains small or extremely small particles of tobacco dust, other minute particulate materials or both. Such particles settle in the holes, pores or interstices of the belt and can (and often do) greatly affect its permeability. This exerts an immediate adverse influence upon the quality of the stream which grows at the underside of the lower reach of the belt because the latter is incapable of adequately retaining and compacting a requisite quantity of tobacco shreds if its permeability has decreased as a result of the accumulation of dust therein.

Attempts to avoid any, or any appreciable, changes in the permeability of the tobacco transporting belt include the provision of a discrete cleaning device which is adjacent to a second reach of the belt, i.e., to a reach other than that on which the rising particles of tobacco gather to form a continuous stream. The cleaning device can comprise a vacuum cleaner which draws contaminants from the holes, pores or interstices of the endless belt at a location other than that where the belt is in contact with the conveyed particulate material.

The provision of a discrete cleaning device contributes to the space requirements (bulk) as well as to the initial and maintenance cost of the machine.

Moreover, the wear upon the endless belt which accumulates the stream of tobacco particles in a cigarette rod making machine is not uniform so that the belt must be replaced at rather frequent intervals even though certain portions thereof could stand additional periods of use.

One feature of the invention resides in the provision of a conveyor, particularly for the transport of particulate material in a tobacco processing plant.

The conveyor comprises an endless foraminous belt and guide means over which the belt is trained. The belt has a material-transporting first reach and an elongated second reach, and that portion of the belt which forms the second reach is twisted through substantially 180 degrees about an axis which extends longitudinally of the second reach.This ensures that, when the belt is driven in a selected direction, successive increments thereof are inverted in the region of the second reach so that, if a current of air or another gaseous fluid is caused to pass through the first reach in a given direction, such fluid passes from one side to the other side of any given increment of the belt during a first travel of such increment along the path which is defined by the first reach and that the fluid passes from the other side to the one side of such increment when the latter again travels along the path which is defined by the first reach.

The belt preferably comprises a splice and then constitutes a converted band of finite length with two end portions one of which is twisted through 180 degrees relative to the other end portion. The splice connects the two end portions of the band to each other.

The conveyor preferably further comprises means for establishing a pressure differential between the opposite sides of the first reach so as to induce a flow of air or another gaseous fluid from one side to the other side of the first reach. The means for establishing such pressure differential can comprise means (e.g., a suction chamber for maintaining the pressure at the other side of the first reach below atmospheric pressure while the other side of the first reach is maintained at or above atmospheric pressure. The one side of the first reach can face downwardly so that the material (e.g., tobacco shreds) which is transported by the first reach of the endless belt extends downwardly from the one side of the first reach. The second reach of the belt can be located at a level above the first reach.

The second reach preferably includes a first section which is disposed in a first plane, a second section which is remote from the first section and is located in or close to the first plane, and a third section between the first and second sections. The guide means preferably defines for the third section a nip located in a second plane which is at least substantially normal to the first plane. To this end, the guide means can comprise two rotary elements (e.g., two idler rollers) which define the nip.

One of the reaches (e.g., the first reach) can be longer than the other reach. The guide means can be designed to provide three or more reaches.

Another feature of the invention resides in the provision of a novel article of manufacture which includes an elongated foraminous band having first and second end portions and a splice which connects the end portions to each other end-to-end or side-by-side (i.e., the end portions can overlie each other or they may merely abut each other).

One of the end portions is twisted through 180 degrees relative to the other. In other words, prior to splicing the two end portions to each other, one of these end portions is twisted through 180 degrees so that the resulting endless belt is not a simple closed loop but rather a closed loop wherein a portion is twisted through 180 degrees. In many instances, the width of the band is or can be at least substantially constant.

The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims. The improved conveyor itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain specific embodiments with reference to the accompanying drawing.

Figure 1 is a somewhat schematic perspective view of a cigarette rod making machine wherein the improved conveyor can be used to accumulate and transport a stream of comminuted tobacco particles; Figure 2 is an enlarged front elevational view of a detail in the machine of Figure 1, showing the first and second reaches of the endless belt which forms part of the improved conveyor; Figure 3 is a perspective view of the twisted second reach of the endless belt; and Figure 4 is a fragmentary plan view of a second conveyor.

Referring first to Figure 1, there is shown a cigarette rod making machine of the type known as PROTOS (manufactured and sold by the assignee of the present application) The machine comprises a distributor including a first magazine 2 which receives batches of shredded andxor otherwise comminuted tobacco particles in response to repeated opening of a pivotable gate 1 at the discharge end of a pneumatic or otherwise constructed conveyor system (not shown) serving to deliver particulate material from a main source of supply. A rollershaped transfer element 3 is provided to deliver particulate material from the first magazine 2 into a second magazine 4 adjacent the upwardly advancing stretch of an endless belt conveyor 5 having pockets (not specifically shown) serving to dump equal or substantially equal portions of particulate material into an upright duct 6.A carded drum 7 withdraws particulate material from the lower end of the duct 6 and cooperates with a picker roller 8 which expels particulate material from the carding of the drum 6 and onto the upper reach of an apron conveyor 9 which is driven at a constant speed. The conveyor 9 accumulates a homogeneous carpet of particulate material and its discharge end propels successive increments of the carpet against a curtain of compressed air issuing from a battery of orifices in a classifying device 11. The heavier particles (such as fragments of tobacco ribs or the like) penetrate across the curtain and enter a collecting receptacle (not shown) but the lighter particles (primarily shreds of tobacco leaf laminae) are deflected by the curtain of air into a funnel 14 which is defined by a driven carded drum 12 and a suitable curved guide wall 13.The drum 12 propels the satisfactory particles of tobacco upwardly into a duct 16 wherein the particles ascend toward and are attracted to the underside of the lower reach 43 (Figure 3) of an endless foraminous belt 17 forming part of the improved belt conveyor The upper side of the lower reach 43 of the belt 17 is adjacent to the at least partially open underside of a suction chamber 18 which forms part of the means for establishing a pressure differential between the upper side and the underside of the reach 43. The chamber 18 evacuates air at the upper side of the lower reach 43 so that the underside of this reach attracts the particles which ascend in the duct 16 and the underside accumulates a growing tobacco stream.

The surplus of tobacco in the fully grown stream is removed by a suitable trimming or equalizing device 19 and the thus equalized stream is deposited on the upper side of a continuous web 21 of cigarette paper or other suitable wrapping material supplied by an expiring reel 22 and passing through an imprinting mechanism 23 serving to provide spaced-apart portions of the web 21 with one or more trademarks, the brand name of the manufacturer, the name of the manufacturer and or other information.The web 21 is advanced by an endless belt conveyor 24 which draws successive increments of the web 22, as well as successive increments of the trimmed tobacco strearn, through a wrapping mechanism 26 wherein the web 21 is partly draped around the tobacco stream but one of its marginal portions extends tangentially of the partially draped stream and into the range of a paster (not shown) whereupon the thus coated marginal portion is caused to overlie the other marginal portion and to form therewith a seam which extends in parallelism with the axis of the resulting continuous cigarette rod 28.The seam is dried by a tandem sealer 27 and successive increments of the cigarette rod 28 advance through a monitoring device 29 which ascertains the density of the filler in the rod 28 and regulates the operation of the trimming device 19 so as to ensure that the density of successive increments of the filler in the rod 28 at least approximates an optimum value. The monitoring device 29 is followed by a cutoff 31 which subdivides the rod 28 into sections 32 of two times unit length. Successive sections 32 are engaged by successive orbiting arms 33 of a transfer unit 34 which deposits the sections into successive flutes of a drum-shaped row forming conveyor 36 in a filter tipping machine 37. The conveyor 36 delivers the thus obtained row of discrete sections 32 into successive flutes of a second drum-shaped conveyor 38 cooperating with a suitable (preferably disc-shaped) knife which subdivides each section 32 into two plain cigarettes of unit length.

Endless belt conveyors 39 and 41 are provided to deliver the trimmed-off surplus tobacco from the equalizing device 19 into a third magazine 42 which is disposed below the magazine 4 and which delivers particles of returned tobacco to the aforementioned pockets of the conveyor 5. A distributor which is suitable for use in the cigarette rod making machine of Figure 1 is disclosed, for example, in commonly owned U.S. Pat. no. 4, 185,644 granted January 29, 1980 to Heitmann et al.

Figure 3 shows in greater detail the guide means over which the belt 17 is trained so as to have the aforementioned lower reach or first reach 43 as well as two additional reaches 51 and 51a. The reach 43 advances in the direction of arrow 44 in a channel 61 which forms part of the suction chamber 18 and receives fragments of tobacco from the duct 16. Such fragments rise in the direction of the arrow 43 and adhere to the underside of the lower reach 43 because the pressure at the upper side of the lower reach is below atmospheric pressure.

The stream building zone is located at a level above the upper end of the duct 16 and the underside of the lower reach 43 transports successive increments of the fully grown tobacco stream past the rotating member or members of the trimming or equalizing device 19. The transfer of successive increments of the trimmed tobacco stream from the underside of the lower reach 43 onto the web 21 (not shown in Figure 3) takes place in the region of a pulley 48 forming part of guide means for the belt 17. The belt 17 is further trained over the rollers 49a, 49b, 49c of an advancing or driving unit 49 which causes the belt to advance in the direction of arrow 44. The roller 49a of the unit 49 is driven by the prime mover of the cigarette rod making machine.The second reach 51 of the belt 17 extends between the roller 49c and a pulley 52 which is urged in a direction to the right, as viewed in Figure 3, by the piston rod of a fluid-operated tensioning motor 59 so that the belt 17 is maintained under requisite tensional stress. The guide means further comprises two additional pulleys 53 and 54 which are disposed at the respective ends of the additional reaches 51a of the belt 17. The major part of the guide means for the belt 17 can be installed in the interior of the suction chamber 18.

The reference character 57 denotes the outlet of the suction chamber 16; such outlet is connected to the intake of a blower, a pump or another suitable suction generating device, not shown.

In accordance with a feature of the invention, and as can be readily seen in Figure 2, the reach 51 of the belt 17 is twisted through 180 degrees about an axis which is parallel to the longitudinal direction of this reach. In other words, the reach 51 comprises a first section 51A which is adjacent to the roller 49c and is disposed in a first plane (tangential to the roller 49a), a second section 51B which is adjacent to the pulley 52 and is also disposed in or very close to the aforementioned first plane, and a third or intermediate section 51C disposed in a second plane making an angle of 90 degrees with the first plane. An important advantage of the feature that the reach 51 is twisted through 180 degrees is that successive increments of the growing tobacco stream at the underside of the reach 43 are formed on and adhere to opposite sides of the belt 17.Thus, the upper side of the lower reach 43 becomes the underside when it reenters the channel 61, it again becomes the upper side when it enters the channel 61 again, and so forth. Therefore, the chamber 16 first draws air through the belt 17 in a first direction, thereupon in a second direction counter to the first direction, and so forth (actually, the direction of air flow through the lower reach 43 remains unchanged but the orientation of the belt portion which constitutes the lower reach 43 changes at regular intervals when the belt 17 is in motion). This renders it possible to achieve a highly satisfactory self-cleaning action because the chamber 18 can extract tobacco dust and other minute particulate material out of the interstices of the belt 17 from the opposite sides of the belt.Thus, if certain minute particles cannot be readily extracted in a first direction (i.e., from one side of the lower reach 43), they are more likely to be readily extractible in a second direction counter to the first direction. It has been found that the self-cleaning action of the belt 17 is surprisingly satisfactory and complete. i.e., the belt is totally relieved of embedded solid particulate material at frequent intervals, normally at intervals the duration of which matches that period of time which it required by an increment of the belt 17 to travel from the pulley 48 at the left-hand end of the chamber 18, as viewed in Figure 3, and back to the same pulley 48.During such period of time, both sides of the belt portion forming the lower reach 43 have faced the interior of the suction chamber 18 so that the particulate material can he readily extracted therefrom to ieave the chamber 18 via outlet 57 and to be collected by a suitable sieve, not shown, before it could reach the suction generating device.

Another important advantage of the improved belt conveyor is that the wear upon the belt 17 is much more uniform than in heretofore known belt conveyors. This is also due to the fact that the reach 51 of the belt 17 is twisted through 180 degrees. Uniform wear necessarily entails a longer useful life of the belt; this is particularly important and desirable in a modern cigarette maker which can turn out up to and in excess of 8000 cigarettes per minute, i.e., even very short-lasting interruptions in operation of such a machine (e.g., for the purpose of inspecting or replacing the belt 17) would result in very substantial losses in output.

Figure 3 shows that the reach 51 where the belt 17 is twisted through 180 degrees is located downstream of the advancing means 49 and upstream of the tensioning pulley 53. However, it is equally possible to twist the belt 17 in the reach 51a (as indicated in Figure 3 by broken lines) or to twist the belt in the reach 51b. In fact, if one desires a very pronounced cleaning action, each of the reaches 51, 51a, 51b can be formed by a belt portion which is twisted through 180 degrees, i.e., the belt 18 can include an odd number of twisted portions and such number can exceed one.

As a rule, the belt 17 is made of a finite length of filamentary synthetic plastic material. One end por tion 17a of the belt 17 is butt-welded to the other end portion 17b, and such one end portion 17a is twisted through 180 degrees prior to welding. The width of the resulting splice 17c (indicated in Figure 2 by broken lines) need not exceed a relatively small fraction of one centimeter (e.g., it can be in the range of 2mm) so that eventual changes in the permeability of the splice 17c between the end portions 17a, 17b are of no consequence insofar as the ability of the belt 17 to attract tobacco particles is concerned. It is also possible to secure the end portions 17a, 17b to each other by means of a suitable adhesive.

In order to compensate for a lengthening of the path of the marginal portions of the belt 18 as a result of twisting of that portion of the belt which forms the reach 51, one or more pulleys andior rollers of the guide means for the belt can have a slightly, or even a pronouncedly, spherical shape.

A further important, desirable and advantageous feature of the improved belt conveyor will be readily appreciated by referring to Figure 4 which shows the structure of Figure 2 and some additional parts of the guide means. The roller 49c and pulley 52 have flanges 49cc and 52cc (not shown in Figure 2) to prevent lateral shifting of the corresponding portions of the belt 17. Such shifting is undesirable because the wear upon certain portions of the belt 17 is then more pronounced than upon the other portions of the belt. In fact, the flanges cannot prevent uneven wear upon the belt because, by preventing the belt from moving laterally in the regions of the respective rotary elements 49c and 52, the flanges come into contact with the adjacent marginal portions of the belt and such marginal portions are thus subjected to more pronounced wear.

It has been found that, quite surprisingly, twisting of the belt 17 through 180 degrees in the region of the reach 51 highly enhances the so-called tracking properties of the belt 17, i.e., the belt is much less likely to exhibit a tendency to move sideways and to leave its pulleys and'or rollers and or to bear against the flanges of such rotary elements with a pronounced force which could give rise to more rapid wear. The tracking properties of the belt 17 can be enhanced still further if the guide means comprises two rotary elements (149 and 149a in Figure 4) which define a nip 249 in the aforementioned second plane, i.e., in a plane which is normal to the common plane of the sections 51A, 51B shown in Figure 2. Moreover, the rotary elements 149, 149a can be used to shift the belt 17 in the direction of arrow A or B (both shown in Figure 4) by the simple expedient of shifting the common support 349 for the shafts of the rotary elements 149, 149a in the direction of the arrow A or B.

Claims (12)

1. A conveyor, particularly for the transport of particulate material in tobacco processing plants, comprising an endless foraminous belt; and guide means over which said belt is trained, said belt having a material-transporting first reach and an elongated second reach, that portion of said belt which forms said second reach being twisted through substantially 180 degrees about an axis which extends longitudinally of said second reach.

2. The conveyor of claim 1, wherein said belt has a splice and constitutes a converted band of finite length with two end portions one of which is twisted through 180 degrees with reference to the other thereof, said splice connecting said end portions to each other.

3. The conveyor of claim 1, further comprising means for establishing a pressure differential between the opposite sides of said first reach so as to induce a flow of air from one of said sides to the other of said sides.

4. The conveyor of claim 3, wherein said means for establishing a pressure differential comprises means for maintaining the pressure at the other side of said first reach below atmospheric pressure.

5. The conveyor of claim 4, wherein said one side of said first reach faces downwardly.

6. The conveyor of claim 1, wherein said second reach is located at a level above said first reach.

7. The conveyor of claim 1, wherein said second reach includes a first section disposed in a first plane, a second section remote from said first section and disposed in or close to said first plane, and a third section disposed between said first and second sections, said guide means defining a nip for a part of said third section, said nip being disposed in a second plane which is at least substantially normal to said first plane.

8. The conveyor of claim 7, wherein said guide means includes two rotary elements which define said nip.

9. The conveyor of claim 1, wherein one of said reaches is longer than the other of said reaches.

10. As a novel article of manufacture, an elongated foraminous band having first and second end portions, one of said end portions being turned through 180 degrees with reference to the other of said end portions, and a splice connecting said end portions to each other.

11. The article of claim 10, wherein the width of said band is at least substantially constant.

12. A conveyor, substantially as herein described with reference to the accompanying drawings.