Abstract:
A sprocket for an endless conveyor is disclosed having a plurality of fluid outlet passages arranged radially between the center of the sprocket and its outer circumferential surface. The outlet passages are positioned along the length of the sprocket in a helical path and are in fluid communication with an annular fluid conduit extending lengthwise along the center of the sprocket. A fluid inlet connected to the conduit supplies fluid under pressure to the conduit, the fluid spraying radially outwardly through the outlet passages to impinge on the inside surface of the endless conveyor and remove any accumulated debris. Nozzles are positioned within the outlet passages to control the fluid spray.

Description:
RELATED APPLICATION 
     This application is based on and claims the benefit of prior filed co-pending provisional patent Application No. 60/200,793, filed Apr. 28, 2000. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to sprockets used with endless conveyors, and especially to sprockets which are adapted to clean the conveyor when in operation. 
     BACKGROUND OF THE INVENTION 
     Conveyors comprising sprocket driven endless belts are used in a wide spectrum of industrial applications to transport items being manufactured or processed from point to point. The items being transported may leak or ooze liquids of varying viscosity, or shed dust, dirt, particles or debris which can accumulate on the belt and foul the conveyor. 
     This problem is especially acute in meat processing equipment where cuts of meat are transported on conveyors between processing stations and ooze blood, deposit viscous or congealed fat, cartilage, muscle, and other animal carcase liquids and debris onto the belt. Such organic matter cannot be allowed to accumulate on the conveyor because it quickly decays and presents a health hazard, rendering the conveyor unusable to transport meat for human consumption. 
     While it is a relatively simple matter to wash the outside surface of the conveyor on which the meat is supported to remove any accumulated organic matter, the various liquids and soft debris tend to work their way into and through crevasses, joints, hinges, interfaces and openings in the belt and a substantial amount of unwanted organic matter thereby accumulates on the inside surface of the belt and on the drive components such as the drive sprockets, idler sprockets and support rollers. Generally, the inside surface of the belt and the drive components are not easily accessible for cleaning, requiring that the conveyor be regularly shut down and maybe even partially disassembled to effect a thorough cleaning and removal of the accumulated organic matter. 
     There is clearly a need for a conveyor wherein the inside surface can be easily and regularly cleaned to remove unwanted debris, liquids, dust and dirt, especially when such debris comprises organic matter which can decay and foul the conveyor. 
     SUMMARY AND OBJECTS OF THE INVENTION 
     The invention concerns an endless conveyor for transporting items and is particularly suited (although not limited) to use in the meat processing industry. Preferably the conveyor comprises at least two rotatably mounted sprockets having respective axes of rotation parallel to one another and arranged in spaced relation along a path oriented perpendicularly to the axes. An endless belt is carried by the sprockets along the path, the endless belt having an outwardly facing surface for supporting the items, such as cuts of meat, and an inwardly facing surface opposite the outwardly facing surface. The inwardly facing surface engages the sprockets. 
     Preferably, at least one of the sprockets comprises an elongated body having an outer surface for support of the inwardly facing surface of the belt. A fluid conduit extends lengthwise within the body from one end. The one sprocket has a pair of supports for rotatably mounting the body, one of the supports having a fluid inlet communicating with the fluid conduit. A plurality of outlet passages extend from the fluid conduit and terminate in apertures in the outer surface of the body. The inlet passage supplies fluid under pressure to the fluid conduit and the fluid, preferably a cleaning liquid, flows outwardly through the outlet passages and the apertures onto the inwardly facing surface of the endless belt where it cleans that surface. 
     Preferably, the length of the one sprocket is substantially equal to the width of the belt, and the fluid conduit extends from the one end substantially to the other end of the body. This configuration allows the outlet passages and the apertures to be positioned in spaced relation lengthwise along the body, thus, ensuring that the entire width of the belt is subjected to the cleaning spray of fluid flowing out of the apertures. 
     While the sprocket may be used with almost any type of conveyor, it is especially effective when used with an endless belt which comprises a plurality of segments arranged side by side. The segments are hingedly connected to one another allowing them to pivot relative to each other when traversing around a sprocket. Because of the many hinges and joints required to ensure flexibility such belts have a marked tendency to accumulate debris on their inside surface as well as other normally inaccessible places such as in the joints between the segments. Cleaning sprockets as described above are particularly suited for use with segmented hinged belts and provide a convenient way to keep the entire belt clean without the need to bring the conveyor out of service for routine cleaning. 
     The sprocket spraying the fluid can be positioned anywhere along the belt path where it can engage the belt&#39;s inwardly facing surface to effectively clean the belt. For example, the sprocket could take the form of a support roller having a smooth outer cylindrical surface and be positioned somewhere between the ends of the belt. Preferably, the sprocket is a driver or an idler positioned at an end of the belt run where the belt segments pivot relatively to one another as they traverse the sprocket and transition to the return leg of their path. 
     To function effectively as a driver, it is preferable that the sprocket have a plurality of teeth spaced circumferentially around the body projecting radially outwardly to engage the inwardly facing surface of the belt. The belt preferably has a plurality of mating teeth projecting from its inwardly facing surface. The mating teeth on the belt interengage the teeth projecting from the body and allow the sprocket to turn without slipping relatively to the belt and impart the force to the belt necessary to drive it. To accommodate the belt at the end of the run and provide a smooth transition around the sprocket, the tips of the teeth intersect a common imaginary cylindrical support surface which envelops the sprocket. 
     To ensure that the spray covers the entire inwardly facing surface of the belt, the apertures are arranged in a row extending in a helix lengthwise along and around the cylindrical support surface. The helix arrangement helps to distribute the fluid spray evenly across the width of the belt and ensures that the belt is receiving a continuous spray of fluid across its width and not an intermittent burst, as would occur if the apertures were arranged in a straight line along the sprocket&#39;s length. 
     When the sprocket has teeth to engage the belt, it is preferable to position the apertures in between the teeth, thus, allowing the spray to clean the teeth as well as the belt. Furthermore the region in between the teeth normally does not come into contact with the belt, thus, allowing a continuous spray to be emitted from the apertures under a constant pressure. If the apertures were periodically blocked by contact with the belt, as they might be if located elsewhere on the sprocket, it would cause repeated pressure surges within the fluid conduit, changing the spray pattern and placing unnecessary stress on the various fluid handling components. 
     To more effectively control the fluid spray, it is preferable to fit nozzles within the apertures. Nozzles can be used to point the spray in a particular direction onto the belt, for example, perpendicularly or relatively tangentially to the inwardly facing surface. Nozzles can also be used to increase the impact force of the fluid stream by directing it into a jet to effectively dislodge stubborn particles or into a diffuse spray to envelop the entire inwardly facing belt surface as required for a particular application. Preferably, the nozzles are oriented substantially radially with respect to the long axis of the body. 
     It is an object of the invention to provide an endless conveyor wherein the inside surface can be easily and regularly cleaned. 
     It is another object of the invention to provide an endless conveyor which does not require disassembly to effect cleaning. 
     It is yet another object of the invention to provide a sprocket for a conveyor through which a fluid can be sprayed onto the inside surface of the conveyor to effect cleaning. 
     These and other objects of the invention will become apparent from a consideration of the following drawings and detailed description of the preferred embodiment. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of an endless conveyor according to the invention; 
     FIG. 2 is a perspective view of a sprocket according to the invention shown in FIG. 1; 
     FIG. 3 is sectional view taken along line  3 — 3  in FIG. 2; 
     FIG. 4 is a cross-sectional view taken along line  4 — 4  of FIG. 2; 
     FIG. 5 is a partial cross-sectional view of the sprocket shown in FIG. 2; 
     FIG. 6 is a cross-sectional view of an alternate embodiment of the sprocket shown in FIG. 2; and 
     FIG. 7 is a cross-sectional view of another alternate embodiment of the sprocket shown in FIG.  2 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows an endless conveyor  10  according to the invention, the conveyor having an endless belt  12  suspended between two rotatably mounted sprockets  14  and  16 . Belt  12  has an outwardly facing surface  18  on which the items to be transported by the belt are supported and an inwardly facing surface  20  opposite the surface  18  and engaging sprockets  14  and  16 . Belt  12  is preferably made of a plurality of segments  22  arranged side by side and hingedly connected to one another by hinge pins  24  allowing segments  22  to pivot relative to one another when traversing around sprockets  14 ,  14   b  and  16  as shown at positions  26  in FIG.  1 . Preferably, segments  22  have mating teeth  28  projecting from the inwardly facing surface  20  to engage teeth on sprockets  14 ,  14   b  and  16  described below. As noted above, sprocket  14  could be an idler sprocket, a driver sprocket, a support roller such as  14   a  in FIG. 1, positioned to engage inwardly facing surface  20  of belt  12  at intermediate points along its run or a belt tensioning sprocket  14   b  positioned at a loop of belt  12  to interact with a pair of tensioning rollers  27  to facilitate tensioning of the belt. 
     FIG. 2 shows a detailed perspective view of sprocket  14  which preferably comprises an elongated body  30  having an outer surface  32  for support of inwardly facing surface  20  of belt  12 . Surface  32  may be a cylindrical surface as seen at  14   a  in FIGS. 1 and 6 where the sprocket frictionally engages the inwardly facing surface  20  to provide support of the belt along its run. However, when used as an idler or a driven sprocket surface  32  is preferably formed by a plurality of teeth  34 , the tips  36  of the teeth being coincident with an imaginary cylindrical surface  31  enveloping the sprocket (shown in dashed line in FIG.  4 ). Teeth  34  are sized and shaped to engage mating teeth  28  on the inwardly facing surface  20  of belt  12  and permit the sprocket to rotate without slipping relatively to the belt. This is most efficient when the sprocket is used as a driver but is also useful when the sprocket is an idler or a support roller as it ensures that the sprocket rotates whenever the belt rotates, the significance of which is explained below. 
     As shown in FIG. 3, a fluid conduit  38  extends lengthwise within the elongated body  30  from one end  40  and preferably substantially to the other end  42 . As best shown in FIG. 4, a plurality of outlet passages  44  extend from the fluid conduit  38  and terminate in apertures  46  in an outer surface  47  of the body  30 . 
     As shown in FIGS. 2 and 3, sprocket  14  has a pair of supports  48  and  50 , which extend from the ends of the sprocket allowing it to be rotatably mounted, for example in a pair of journal bearings (not shown). One of the supports, for example  48 , has a fluid inlet passage  52  extending through it and communicating with fluid conduit  38  by means of openings  54 . 
     Fluid, supplied under pressure to fluid inlet passage  52  through a suitable coupling (not shown) flows through the inlet passage into the fluid conduit  38 , through the outlet passages  44  and exits through apertures  46  where the spray contacts the inwardly facing surface  20  of belt  12  to dislodge any debris or residue which has formed on the surface. 
     To ensure that the belt receives the effect of the cleaning spray over the entire width, it is preferable that the width of the sprocket be substantially the same as the width of the belt and that the fluid conduit  38  extend substantially from one end of the sprocket  40  to the other end  42 . 
     Preferably, fluid outlet passages  44  are positioned in spaced relation lengthwise along body  30 , and more preferably, the outlet passages are arranged in a row extending in a helix lengthwise along and around the cylinder as shown in FIGS. 2 and 3. Arranging the outlet passages along the entire length ensures that the fluid and its cleansing action will be distributed over the entire width of the belt, and arranging the outlets in a helix ensures that the belt is receiving a continuous spray of fluid across its width and not an intermittent burst, as would occur if the apertures were arranged in a straight line along the sprocket&#39;s length. Sprocket teeth  34  engaging mating teeth  28  on belt  12  ensure that the sprocket rotates without slipping relatively to the belt and as the sprocket rotates it is constantly directing a different stream of fluid at a different portion of the belt for maximum cleaning coverage. 
     As a practical matter, the supports  48  and  50  may be mounted at the ends of a continuous axle  55  which extends entirely through the fluid conduit  38 . To seal the body  30  at the ends  40  and  42  where the axle emerges, each end of the axle is provided with a sealing flange  56  and  58 . Flanges  56  and  58  are sized to seat against respective sealing surfaces  60  and  61  arranged at each end of the body surrounding the fluid conduit  38 . One of the flanges, for example,  56 , is preferably permanently attached to the axle, the other flange  58  being removable and held in place by a nut  62  engaging threads  64  on the support  50 . The axle has a smaller diameter than the fluid conduit providing an annular space through which the fluid can flow the entire length of the conduit. When the axle  55  is inserted in the conduit  38 , sealing flange  56  is seated against sealing surface  60  at end  40  of the body, support  50  extends from fluid conduit  38  at end  42 , and sealing flange  58  is seated against sealing surface  61  at end  42 . Nut  62  engages threads  64  and is torqued to force the sealing flanges against the sealing surfaces to effect a fluid tight seal at each end of the body. O-rings  66  and  67  may also be used between the sealing flanges and the sealing surfaces to effect the seal. 
     As seen in FIG. 4, the outlet passages  44  are preferably radially oriented with respect to the outer surface  46  of the body  30 , although it is contemplated that other orientations would also be possible and practical under certain conditions. Preferably, the apertures  46  are located between teeth  34  in a region which faces hinge pins  24  (see FIG. 1) but does not contact the belt  12  directly. Thus, a continuous stream of fluid emerges from each of the apertures  44  regardless of the relative position of an aperture to the belt. This allows the sprocket to spray at a constant pressure and avoids pressure surges which might occur if a particular aperture were blocked by contact with the belt as it traverses the sprocket. 
     As shown in FIG. 5, nozzles  68  may be mounted within the fluid outlet passages  44  to control the stream of fluid from the outlet passages against the inwardly facing surface  20  of belt  12 . The nozzles can form the spray into any combination of configurations, from a concentrated jet hitting the belt with a high velocity to blast debris and residue from the belt, to a wide angle spray to soak the belt over a wide area. The nozzles can be permanently set to a particular spray regime or adjustable for maximum versatility. 
     An alternate embodiment for the arrangement of outlet passages  44  is shown in FIG.  7 . Instead of arranging one outlet passage at each particular cross-section along the length of body  30 , multiple outlet passages are arranged at each cross section, thereby providing a symmetrical radial spray of fluid to clean the belt  12  along the entire length of the sprocket  14 . 
     It is contemplated that the fluid to be sprayed from the sprocket may be a gas such as compressed air. Such a system would be practical, for example, if it is desired to prevent the accumulation of dust on the conveyor. For a conveyor used to transport cuts of meat where viscous organic matter and residue will accumulate on the belt, it is preferable that the sprocket spray a liquid such as water or a liquid detergent or other cleaning fluid to most effectively remove the organic matter from the belt. 
     Use of a sprocket cleaning belt according to the invention increases the efficiency of plant operations as the conveyors cleaned of debris and residue need not be taken out of service and disassembled to clean otherwise inaccessible regions such as the inwardly facing surface of the belt. The sprocket cleaning belt will also improve the sanitary condition of the conveyor as it ensures a thorough cleaning of the belt, which might not otherwise occur.