String doffer mechanism

Abstract: A mechanism for removal of contaminants from a stream of material has a plurality of rotatable hollow cylindrical doffer elements (11) each having flights (12) supplied with cleaning means (13) thereon mounted substantially parallel to one another within a frame (10). The doffer elements are each mounted on blocks (22, 24; 26, 28) on the frame. The blocks are provided with a number of mounting holes (23) whereby the vertical elevation of the doffer elements (11) with respect to the frame may be varied. The blocks are mounted to the frame by T-shaped bolts (37) the heads of which are slidable in a T-shaped groove (27) on the frame whereby the position of each doffer element on the frame may be adjusted.

Description: This invention relates to a string doffer mechanism for removal and separation of undesirable objects such as string and dirt from a material, such as tobacco, before end products can be made from the material. It is known that foreign objects, such as dirt and portions of string by which the tobacco leaves are tied together during curing, may be separated and removed from tobacco during preliminary processing by the use of a mechanism consisting of a series of elongated roller elements mounted side-by-side in an open frame or bed. Such a mechanism is disclosed in Caudill U.S. Patent 4, 809,716. In such a mechanism the tobacco is transferred across a series of rotating rollers, or "doffer elements", which are covered by cleaning elements such as brushes. Alternatively, the cleaning elements may be a material containing densely packed resilient hook members, such as Velcro®. The contaminants contained in the tobacco become entwined in the rotating brushes or the Velcro attached to the individual doffer elements. After travelling over the last rotating doffer element, the tobacco is transferred to a separate device, such as a conveyor, and moved to other locations for further processing or storage. To remove effectively the contaminants from the tobacco, the cleaning brushes or the Velcro must frequently be cleaned of contaminants and periodically replaced. For example, where Velcro® is employed as the cleaning means, as contaminants become trapped on the cleaning surface, the effectiveness of the cleaning surface is reduced. To "reactivate" the cleaning surface, the trapped contaminants must be removed. Additionally, various portions of the mechanism, such as the doffer elements, require maintenance at unpredictable times. Cleaning, replacement, and maintenance require that the mechanism be inoperable and result in system down time. Maintenance of the mechanism and doffer elements that requires removal of the doffer elements is complicated by the fact that the doffer elements disclosed in the prior art each weighs a great deal. The maintenance or replacement of doffer elements or other components of the mechanism often require disassembling the entire drive mechanism, resulting in further system down time and labor expenses. It is known that different varieties and grades of tobacco leaf contain different amounts and different size contaminants, and consist of different tobacco particle sizes. Furthermore, the manner in which the tobacco is packaged, transferred, or stored effects the amount, type and size of foreign objects which may contaminate the tobacco. For instance, tobacco leaves which are transferred in bags made of burlap contain pieces of fibers from the burlap, while tobacco leaves which are tied together with string are contaminated with pieces of string which may be larger than burlap fibers. It is has also been found that variable spacings between the doffer elements provide optimal cleaning for tobacco known to contain certain types of contaminants. Furthermore, different grades of tobacco, which are of differing densities, require different operating parameters in order to be properly cleaned. For example, testing on Bright tobacco has revealed that a 2-inch horizontal gap between all doffer elements results in optimal separation. Elevation changes between doffer elements are not necessary for Bright tobacco. Testing on Bright has also indicated that up to 50% of entrained contaminants can be removed when the doffer elements are rotated at a speed of 150 rpm and the tobacco feed rate is 8,000 pounds per hour. Testing on Burley tobacco indicates that optimum operating conditions include horizontal gaps of 3-inches between doffer elements, doffer element rotational speeds of 150 rpm and tobacco feed rate of 8,000 pounds per hour. It has also been concluded that for Oriental tobacco, the optimum set up is a 1.5-inch gap between successive doffer elements, doffer element speed of 150 rpm and tobacco feed rate of 8,000 pounds per hour. It has been found that for both Burley and Oriental tobacco, as well as for Bright tobacco, that the doffer elements should be fixed in the same plane in order the achieve optimal separation. Although testing on Bright, Burley and Oriental tobaccos has indicated that change in the elevation of the doffer elements relative to the frame are not prerequisite to successful operation of the mechanism, elevational changes may be useful when other grades of tobacco or other materials must be cleaned of contaminants. The agitation caused by placing one or more doffer elements at a different elevation from the remaining doffer elements may be necessary for cleaning certain materials. Therefore, it can be seen that the mechanism's operating conditions must be adjustable in order to obtain optimal separation and removal of contaminants from different varieties of tobacco, as well as from other materials. With respect to mechanisms used at present it is not possible to attain the optimal operating conditions as the adjustability of most of the operating conditions is limited. Existing mechanisms have a fixed number of doffer elements arranged at fixed horizontal gaps and vertical elevations. Their operating conditions either cannot be varied at all, or require large amounts of down time to adjust conditions for cleaning different types and grades of tobacco. US-A-973,228 discloses a tobacco cleaning machine in which tobacco passes through pairs of opposed rotating brushes. US-A-4,809,716 discloses a conventional string doffer in which a plurality of doffer elements are arranged in a frame. US-A-4,102,502 discloses a bed of rollers used to separate platelets from mined ore; and DE-A-2504875 discloses a further example of a tobacco cleaning machine. The present invention aims to overcome the limitations of the prior art described above and to provide a doffer mechanism and doffer elements which may be adjusted to the optimum operating conditions for the material being processed. It is a further aim of the present invention to provide an improved doffer mechanism for removing and separating contaminants and other objects from tobacco. According to the invention there is provided a doffer mechanism for removing contaminants from a stream of material, comprising a frame having at least two oppositely disposed sides, a plurality of doffer elements, each doffer element having two ends and an axis of rotation passing through the two ends, means for mounting the two ends of each of the doffer elements to opposite sides of the frame at positions along the sides of the frame, such that the doffer elements are mounted in a row across the frame and the axes of rotation of the plurality of doffer elements are substantially parallel, means for rotating the plurality of doffer elements about their respective axis of rotation, and means for adjusting the elevation above or below the frame of at least one of the doffer elements. The invention also provides a doffer mechanism for removing contaminants from a stream of material, comprising a frame having at least two oppositely disposed sides, a plurality of doffer elements, each doffer element having two ends and an axis of rotation passing through the two ends, means for mounting the two ends of each of the doffer elements to opposite sides of the frame at positions along the sides of the frame, such that the doffer elements are mounted in a row across the frame and the axes of rotation of the plurality of doffer elements are substantially parallel, means for rotating the plurality of doffer elements about their respective axis of rotation, and means for selectively adjusting the positions along the sides of the frame at which the ends of at least one doffer element are mounted to the frame. Embodiments of the invention have the advantage that variation in the operating conditions of the mechanism is possible. An embodiment of the invention permits for easy adjustment of the gap between successive doffer elements and easy adjustment of the elevation of individual doffer elements relative to the frame to optimize tobacco surface contact with the doffer cleaning means for various types and grades of tobacco. The frames of the mechanism of a preferred embodiment of the present invention may also be installed at an upwardly inclined angle if operating conditions so dictate. Preferred embodiments of the present invention may have the advantage of requiring a reduced system down time for cleaning and maintenance of the doffer mechanism and doffer elements. Preferred embodiments of the invention may also have the advantage of having lightweight doffer elements and a doffer mechanism which allows for easy removal of the doffer elements for maintenance as well as replacement of cleaning elements attached to the doffer elements. Preferred embodiments of the invention have the advantage of an improved drive design which may facilitate the aforementioned adjustments, cleaning, maintenance and replacement of the doffer elements and the cleaning means attached to the doffer elements. In a preferred embodiment of the invention, a doffer mechanism for the removal of contaminants from tobacco includes a plurality of doffer elements mounted parallel to one another within a frame, each doffer element having cleaning flights located thereon. The doffer elements are rotated about their axes in the same direction and are driven by a continuous chain which allows for easy individual adjustment of the gap between doffers. Preferably, the elevation of one or more doffer elements above or below the frame may be readily and easily adjusted. In one preferred embodiment of the invention, a pair of frames is provided, each frame having a plurality of doffer elements. The pair of frames is connected to one another by a subframe such that each frame can be pivoted from a first, substantially horizontal position during which the doffer elements in that frame are operable, to a second, substantially upright position during which the doffer elements in that frame can be cleaned. Further preferred embodiments of the invention may comprise a pair of frames which remain unconnected and a flop or pantleg gate. In these embodiments, the gate can be used to direct the flow of the material to be cleaned to one frame while the other frame is idle and can be cleaned. In these embodiments, the frames can be located parallel to one another or can be oppositely inclined from one another. Preferably the doffer elements are hollow and generally tubular in shape and have a cleaning surface affixed at various locations. A drive assembly for driving the doffer elements within the frame is also provided. The drive assembly comprises a continuous chain, a drive means such as a motor, a plurality of doffer sprockets attached to the doffer elements and a plurality of idler sprockets. The doffer sprockets engage the exterior side of the chain such that the doffer elements may be removed for cleaning and maintenance without disrupting the path of the chain. Embodiments of the invention will now be described by way of example, and with reference to the accompanying drawings, in which: Figure 1 is a cross sectional view of a doffer element used in conjunction with the mechanism embodying the present invention. Figure 1(a) is an end-perspective view of a doffer element used in conjunction with the mechanism embodying the present invention, illustrating the cleaning means. Figure 2 is a longitudinal sectional view of a doffer element embodying one aspect of the present invention, illustrating the shafts which connect the element to the frame assembly. Figure 3 is a top view of the frame containing the doffer elements mounted parallel to one another. Figure 4 is a drive side view of the frame and drive means embodying the present invention. FIG. 5 is a sectional view of a T-slot bolt, a portion of an adjustable slider block and a portion of the frame. FIG. 6 illustrates the adjustable slider blocks located on the following side of the mechanism that are used in conjunction with vertically adjustable doffer elements. FIG. 7 is a side view of the block of FIG. 6. FIG. 8 illustrates the adjustable slider blocks located on the driving side of the mechanism that are used in conjunction with vertically adjustable doffer elements. FIG. 9 is a side view of the block of FIG. 8. FIG. 10 illustrates the blocks located on the following side of the mechanism that are used in conjunction with stationary doffer elements. FIG. 11 is a side view of the block of FIG. 10. FIG. 12 illustrates the blocks located on the driving side of the mechanism that are used in conjunction with stationary doffer elements. FIG. 13 is a side view of the block of FIG. 12. FIG. 14 is a diagrammatic end view of a further embodiment of the invention illustrating the "flop" arrangement of the frames. FIG. 14A is a top view of the embodiment shown in FIG. 14, with the doffers not shown for clarity. FIGS. 15-17 are diagrammatic side views of other embodiments of the invention. The rotatable doffer elements of the present invention will now be described in detail. As shown in Figs. 1 and 2, rotatable doffer elements 11 each include a hollow metal tube 17. The ends of doffer elements 11 are affixed to hollow metal shafts 16 and 18 by means of circular metal plates 20 located at each end of tube 17. Plates 20 are affixed to tube 17 by means of screws or a weld or any other means generally known in the art. Plate 20 supports the tube 17 and provides a means for affixing the shafts 16 and 18. Doffer sprocket 19 is affixed to shaft 18 so that rotation of doffer sprocket 19 will cause doffer element 11 to rotate about its longitudinal axis. As further discussed below, hollow tube 17 of each doffer element 11 is preferably 37-1/2 inches long and is preferably 4 inches in diameter. The design of these doffer elements differs from other rotatable elements which are comprised of substantially solid metal. Thus, the doffer elements embodying the present invention weigh much less than those currently in use, while providing the required structural integrity and durability required of string doffer mechanisms. Flights 12 are attached along the length of the outer surface of the tube 17. Preferably, flights 12 are hollow metal protuberances extending in a longitudinal direction along the tube 17. Most preferably flights 12 consist of six 1-inch square paddles welded to each doffer at equal distances about the circumference of tube 17. Attached to the top surface of flights 12 is cleaning means 13. Attachment of the cleaning means 13 may be by any known means such as by adhesive. Screwing the cleaning means 13 onto the flight 12 by providing several screw holes in the flight and cleaning means prevents lifting while allowing for easy removal and replacement of cleaning means 13 and is thus preferred. Preferably, cleaning means 13 consists of a hook material such as Velcro® and is attached only to the top surfaces of the flights. Most preferably, cleaning means 13 is white in color, thereby allowing for easy detection of contaminants which become entwined therein. Alternatively, all surfaces of flights 12 and all exposed surfaces of metal tube 17 may be covered with a cleaning means. However, because the tobacco tends to almost exclusively engage the top surfaces of the flights, covering only the top surfaces of the flights is preferred. Fig. 1(a) illustrates the preferred placement of cleaning means 13. Cleaning and replacement of the cleaning means is less expensive and time consuming when only the top surfaces of the flights are covered. Cleaning may be accomplished by hand using a spring steel curry comb and should be performed as often as possible to increase the efficiency of the mechanism. One embodiment of the mechanism consists of a single doffer unit. As can be seen from the top view shown in Fig. 3, the doffer unit consists of a frame 10 and doffer elements 11. Doffer elements 11 are generally cylindrical and rotate simultaneously in the direction of product flow. The number and size of doffer elements 11 is a matter of design choice. Preferably, each doffer element 11 has a maximum length of 37 1/2 inches and a diameter of approximately 4 inches. As shown in Figs. 3 and 4, (Fig. 4 being a side view), doffer elements 11 are attached to frame 10 via shafts 16 and 18 by means of blocks 22-28. Blocks 22-28 may be fixedly mounted to frame 10, as was conventionally done prior to the present invention. Alternatively, the blocks may be slidably mounted to frame 10, as will be described below. As shown in Figs. 6-13, bearing mounts 32 are attached to differing types of blocks 22-28, such as by bolts 35. Bearing mounts 32 support shafts 16 and 18 of doffer elements 11. The bearing mount and block design illustrated in Figs. 6-9 permits vertical or elevation adjustments to doffer elements 11. (As used in this sense, the terms "vertical" or "elevation" refer to the distance of the doffer element from an imaginary plane lying on the frame. Thus, if the frame is situated horizontally the "elevation" of the doffer element from the frame corresponds to its vertical distance from the frame.) Figs. 6 and 7 show adjustable block 22 that supports shaft 16. Adjustable block 22 is located on the side of the mechanism opposite the driving means for the doffer elements 11. Figs. 8 and 9 show drive side adjustable block 24 that supports shaft 18 and includes sprocket 34 that is rotatably affixed to block 24 using conventional means. Doffer sprocket 19 is also shown. Sprocket 34, which is shown in Fig. 8 and Fig. 3, is not shown in Fig. 9 for clarity. In this design, the blocks 22 and 24 are provided with a plurality of pairs of holes 23. By unbolting both bearing mounts 32 from blocks 22 and 24 and then moving bearing mounts 32 to another set of holes, the elevation of doffer element 11 relative to frame 10 can be adjusted. Preferably, the range of elevation adjustment is limited to two inches. The blocks shown in Figs. 6-9 can be adjusted to five different elevations. The bearing mount designs illustrated in Figs. 10-13 operate in the same manner as those illustrated in Figs. 6-9. However, because blocks 26 and 28 do not permit vertical adjustment to doffer elements 11, they contain only one pair of holes for receiving bearing mount 32 as opposed to the plurality of hole pairs contained in adjustable block 22 and drive side adjustable block 24. Figs. 10 and 11 show block 26 which supports shaft 16 in bearing mount 32. Block 26 is located on the side of the mechanism opposite the driving means for the doffer elements 11. Figs. 12 and 13 show drive side block 28 which supports drive shaft 18. Drive side block 28 includes sprocket 34 that is rotatably affixed to block 28 using conventional means. Doffer sprocket 19 is shown. Sprocket 34, which is shown in Fig. 12 and Fig. 3, is not shown in Fig. 13 for clarity. The means for attaching blocks 22-28 to frame 10 provides for continuously variable adjustment of the horizontal gap between successive doffer elements 11. As shown in Fig. 5, the frame 10 is provided with T-shaped groove 27 along the length of each of its sides. Blocks 22-28 can be slidably mounted to frame 10 by means of two T-bolt 37, the head of which fits into T-shaped groove 27. When horizontal adjustment is desired, nut 36 of T-bolt 37 is loosened and block 22, 24, 26, or 28 is moved along the T-shaped groove located within frame 10 to its desired position. Then nut 36 of T-bolt 37 is re-tightened. Thus, blocks 22-28 and doffer elements 11 which are supported by blocks 22-28 can be positioned at any particular position along frame 10. Preferably, each block is fastened to frame 10 by two T-bolts 37 and two nuts 36. Preferably, each block 22-28 can be slid between 0 and 3 inches along the frame 10. As mentioned earlier, the doffer elements 11 are rotatable about their axes in bearings 32 which are mounted on frame 10 by blocks 22-28. Doffer sprockets 19 of doffer elements 11 are driven by a continuous chain 15, as illustrated in Fig. 4. For clarity, chain 15 is not illustrated in Fig. 3, which is a top view of frame 10 with doffer elements 11. Chain 15 is driven by drive motor/gear reducer 14 which is located on the feed end of the doffer unit. Chain 15 passes around guide sprockets 21 which are located beneath frame 10. Guide sprockets 21 aid in the maintenance of the proper amount of tension in chain 15. The path of chain 15 runs below the doffer sprockets 19 mounted on each shaft 18 and over idler sprockets 34 mounted to blocks 22-28 by means of idler sprocket bearings. Thus doffer sprockets 19 are located outside of the loop formed by continuous chain 15. This drive arrangement permits doffer elements 11 to be removed for maintenance or for horizontal or vertical adjustment without disturbing the path of chain 15. When removal or adjustment is desired, bearing mounts 32 are unbolted and doffer element 11 is lifted away from blocks 22, 24, 26, or 28. Alternatively, a tensioned belt can be substituted for chain 15, and the sprockets can be replaced with drums. Chain 15 and sprockets are preferred, however. In the preferred embodiment of the present invention, frame 10 supports nine doffer elements 11. It has been found that contaminant removal efficiency increases as the doffer element surface area increases due to improved tobacco distribution and contact with the cleaning means; therefore, it is advantageous to use a plurality of doffer elements. Preferably, the mechanism is provided with adjustable blocks 22 and drive side adjustable blocks 24 for adjusting the vertical elevation of doffer elements 11. Adjustable blocks 22 and drive side adjustable blocks are paired opposite one another along frame 10 only at specific locations. Blocks 22 and 24 are preferably installed at doffer element locations 4, 6 and 9, with location 1 at the feed end of the mechanism. The doffer mechanism embodying the present invention may have three separate designs: a right hand drive assembly, a left hand drive assembly, and a "flop" style assembly. The right hand and left hand drive assemblies consist of a single frame unit of doffers, as shown in Fig. 3. (Fig. 3 depicts the right hand drive assembly.) The single unit assemblies were created for low clearance installations. In order to suit the particular installation, these assemblies can have the drive assembly on the right or the left side. The flop style assembly, as illustrated in Fig. 14, is essentially a utilization of both the right hand assembly and the left hand assembly held together by subframe 33. Motor/gear reducers 14, which are not shown in Fig. 14 for clarity, are preferably located on the pivoting side of the frame 10. One side of each of the two frames 10 is attached to pivot means 39, which comprises stub shafts 39a, which are attached to the ends of frame 10, and bushing blocks 39b, which are attached to subframe 33. Pivot means 39 could also be any other pivoting arrangement known in the art. The flop assembly is preferred because the contaminant removal efficiency is much higher than for a single frame doffer unit. This is because the assembly can be cleaned more often without substantial down time. Operation of the flop assembly has shown that the doffer elements 11 can be regularly cleaned every 2-3 hours with minimum down time. As shown in Fig. 14, one doffer unit operates in a substantially horizontal position while the other doffer unit is cleaned or maintained in an upright position. Tilt bed motors 50 and gear boxes 51 are not shown in Fig. 14 for clarity. The top view of a frame 10 shown in Fig. 3 also shows stub shafts 39a. Also shown is motor/gear reducer 14, which is preferably positioned to counterbalance the weight of frame 10 and doffers 11 about pivot means 39. Fig. 14A shows a top view of frames 10a and 10b mounted on subframe 33. Doffer elements 11, mounting blocks 22-28, and the drive assembly are not shown. Bushing blocks 39b are attached to subframe 33 and support stub shafts 39a. Tilt bed motors 50 and conventional gear boxes 51 are also attached to subframe 33. Gear boxes 51, driven by motors 50, rotate stub shafts 39a to raise and lower frames 10a and 10b. In Fig. 14A, frame 10a is shown in the horizontal position, whereas frame 10b is shown in the upright or vertical position. In the flop assembly, doffer units may be alternatively brought into and out of engagement by means of tilt bed motors 50 which cause frames 10 to rotate about pivot means 39. Pivot means 39 may be of any type generally known in the art. Preferably, each unit is fully positively counterbalanced so that the mechanism's natural position is either up (the cleaning/maintenance position) or down (the operating position). The flop assembly is used in conjunction with a take away conveyor 41 located at the downstream end of the flop assembly for moving the cleaned tobacco on for further processing. Other embodiments of the present invention are illustrated in Figs. 15-17. As shown in Fig. 15, the mechanism may consist of a feed chute with a "pant leg" assembly 43 and opposing frames 10 containing rotating doffer elements 11. Thus, tobacco flows down one "leg" of chute 43, is processed through doffer elements 11 contained within one of the opposing frames 10 (not shown), and is moved on for further processing by conveyors 41. While tobacco is processed through one doffer unit, the other may be cleaned. Alternatively, Fig. 16 illustrates the same basic embodiment as shown in Fig. 15 with a single take away conveyor. In these two embodiments, the pant leg assembly is useful because it eliminates the need for a movable conveyor for dropping tobacco onto the middle of the first doffer element 11. Another alternative is illustrated in Fig. 17. In this assembly, doffer units, which are represented by doffers 11, are layered. This assembly makes use of a flop gate 45 and a drop chute 47. When the upper doffer unit is in use and the lower doffer unit is being cleaned, the flop gate 45 drops tobacco onto the upper doffer unit. After processing, tobacco travels through drop chute 47 onto take away conveyor 41. When the lower doffer unit is in use and upper doffer unit can be cleaned, flop gate 45 swings downwardly to deliver tobacco to the lower doffer unit. There is no need to use drop chute 47 as tobacco directly travels to take away conveyor 41. Although the preferred use of the mechanism of the present invention relates to the removal of contaminants from a uniform flow of tobacco fed through the doffer elements, it is not limited to the purification of tobacco. Many types of materials can be purified using doffer elements in any of the embodiments described above.

Claims: A doffer mechanism for removing contaminants from a stream of material, comprising a frame (10) having at least two oppositely disposed sides (10a, 10b), a plurality of doffer elements (11), each doffer element having two ends (16, 18) and an axis of rotation passing through the two ends, means (22, 24; 26, 28) for mounting the two ends of each of the doffer elements to opposite sides of the frame at positions along the sides of the frame, such that the doffer elements are mounted in a row across the frame and the axes of rotation of the plurality of doffer elements are substantially parallel, means (9, 34) for rotating the plurality of doffer elements about their respective axis of rotation, and means (23) for adjusting the elevation above or below the frame of at least one of the doffer elements (11). A doffer mechanism for removing contaminants from a stream of material, comprising a frame (10) having at least two oppositely disposed sides (10a, 10b), a plurality of doffer elements (11), each doffer element having two ends (16, 18) and an axis of rotation passing through the two ends, means (22, 24; 26, 28) for mounting the two ends of each of the doffer elements to opposite sides of the frame at positions along the sides of the frame, such that the doffer elements are mounted in a row across the frame and the axes of rotation of the plurality of doffer elements are substantially parallel, means (19, 34) for rotating the plurality of doffer elements about their respective axis of rotation, and by means (27, 36, 37) for selectively adjusting the positions along the sides of the frame at which the ends of at least one doffer element (11) are mounted to the frame. A doffer mechanism according to Claim 2, further comprising means (23) for adjusting the elevation above or below the frame of at least one of the doffer elements (11). A doffer mechanism according to Claim 1, 2 or 3, wherein the means for mounting the two ends of each of the doffer elements to the frame comprises a pair of blocks (22; 24; 26, 28) including bearing supports (32) which attach to opposite sides (10a, 10b) of the frame. A doffer mechanism according to Claim 4, wherein the means (23) for adjusting the elevation of the doffer elements comprising means for adjustably fastening the bearing mounts to the blocks in at least two configurations. A doffer mechanism according to Claim 5, wherein the means for fastening the bearing mounts to the blocks includes a plurality of holes (23) in the block, with a hole corresponding to each possible elevation of a given doffer element, the doffer mechanism further comprising nuts and bolts for attaching the bearing mounts to the blocks. The doffer mechanism according to Claim 2, wherein the means for mounting the two ends of each of the doffer elements to the frame comprises a pair of blocks, and the means for selectively adjusting the positions along the sides of the frame comprises at least one T-shaped groove (24) in the frame that slidably engages the head of at least one substantially T-shaped bolt whereby the substantially T-shaped bolt (37) slidably mounts at least one block to the frame. A doffer mechanism according to any preceding claim, comprising a second frame of substantially the same size and shape as the first frame, and by means (44, 43; 45) for selectively directing the stream of material to a selected one of the frames of doffer elements for removal of contaminants from the stream by the doffer elements of a selected one of the frames. The doffer mechanism according to Claim 8, wherein the first and second frames comprise a pair of frames oppositely inclined with respect to one another. The doffer mechanism according to Claim 8, wherein the first and second frames are positioned parallel to one another. The doffer mechanism according to Claim 9, wherein the means for selectively directing the stream comprises a feed chute (43) having delivery ends located at a lower end of each inclined frame and means for changing the configuration of the feed chute to direct the flow of material from one of the frames to the other of the frames. The doffer mechanism according to Claim 10, wherein the means for selectively directing the stream comprises a pivotal delivery gate (45) movable between a first position in which it can feed material to the first frame and a second position in which it can feed material to the second frame. The doffer mechanism according to any preceding claim wherein the doffer elements each comprise a hollow tube (17) having two ends and a central longitudinal axis passing through each of the two ends, a pair of circular plates (20) affixed at the ends of the hollow tube, a shaft (16, 18) attached to each of the circular plates, each shaft having two ends such that the central longitudinal axis of the hollow tube passes through each of the two ends of each shaft, and means for affixing a cleaning surface to the doffer element. A doffer mechanism according to any preceding claim, wherein the doffer elements (11) are cylindrical hollow members (17). A doffer mechanism according to any preceding claim, wherein each of the doffer elements (11) has a surface and a plurality of elongated flights (12) extending the length of the surface. A doffer mechanism according to Claim 15, wherein each flight (12) comprises an elongated rectangular bar. A doffer mechanism according to Claim 16, wherein the rectangular bars are mounted equidistantly about the surface of the doffer elements. The doffer mechanism according to Claim 15, 16 or 17, wherein each of the flights (12) has an exposed surface and a cleaning means (13) attached to the exposed surface of each of the flights. The doffer mechanism according to Claim 18, wherein the cleaning means is a hooked material. The doffer mechanism according to Claim 4, wherein the means for rotating the doffer elements further comprises a plurality of doffer sprockets (19) attached to the one end of each of the doffer elements, a plurality of idler sprockets (34) attached to the blocks, and a motor driven continuous chain which engages both the idler sprockets and the doffer sprockets. The doffer mechanism according to any preceding claim, wherein the stream of material is tobacco leaves. A doffer mechanism according to any preceding claim, comprising a continuous chain, the chain having an inner surface and an outer surface; means for driving the continuous chain, each doffer element having a doffer sprocket (19) for converting the motion of the continuous chain into rotational motion from rotating the doffer element, at least one of the doffer sprockets being in contact with the outer surface of the continuous chain; and at least one idler sprocket (34) the idler sprocket contacting the inner surface of the continuous chain. A doffer mechanism according to any of claims 1 to 21, comprising a continuous belt, the belt having an inner surface and an outer surface; means for driving the belt; each doffer element having a doffer drum for converting the motion, of the continuous belt into rotational motion for rotating the doffer element, at least one of the doffer elements being in contact with the outer surface of the continuous belt; and at least one idler drum, the idler drum contacting the inner surface of the continuous belt.

Inventors: BOSWELL GEORGE S, GOMES JOAO C A, MACIEJCZYK JOSEPH P, BOSWELL, GEORGE S., GOMES, JOAO C.A., MACIEJCZYK, JOSEPH P.
Applicants: PHILIP MORRIS PROD, PHILIP MORRIS PRODUCTS INC.
Application year: 1991
Main classification: A24B3
IPC codes: A24B3, A24B1