Patent Publication Number: US-2022212875-A1

Title: Modular conveyor belt having alternating drive surfaces

Description:
The present invention relates to a modular conveyor belt according to the preamble of claim  1 . 
     Whenever objects have to be transported over comparatively short distances, and in particular within a production site, modular conveyor belts are a suitable and commonly used tool. Depending on the actual application the modular conveyor belt is used for, the modular conveyor belt must comply with varying requirements. 
     In particular, modular conveyor belts that are used in food industry have to be easily cleanable. Further, the material of the modular conveyor belt should not contaminate foodstuff in any way. Therefore, in food industry plastic conveyor belts are widely used. Contrary to metal conveyor belts, they do not corrode, are lightweight and are easy to clean. For easier scalability, quite often modular plastic conveyor belts are used that are made up of moulded plastic belt modules that can be arranged side-by-side in rows of selectable width. A series of spaced apart link ends arranged at the leading and trailing edges (sides) of the modules include aligned openings to accommodate a pivot rod. The link ends along one side of a row of belt modules are interconnected with the link ends of an adjacent row of belt modules. A pivot rod journaled in the aligned openings of connected modules forms a hinge between adjacent rows. Rows of belt modules are then connected together to form an endless conveyor belt capable of articulating about a drive sprocket. If the length of the modular conveyor belt exceeds a certain size, quite often conveyor rollers or supporting slides are used to support the modular conveyor belt. Such conveyor rollers can be either rolling passively (essentially being driven by the modular conveyor belt), or they can be active, meaning that they actively drive the modular conveyor belt. In the latter case, typically sprockets are used. 
     Furthermore, in food industry, solid or flat-top modular plastic conveyor belts are frequently used for meat, fish, or other products that drip or tend to drop crumbs or particles. The top of such belts can present a smooth, flat surface with very small gaps at the proximity region between two adjacent belt modules. Thanks to the usual design with link ends that comprise pivot rod openings and pivot rods that are arranged through such pivot rod openings, it is possible to bend the modular conveyor belt around sprockets, in particular around end-sited sprockets, so that an endless belt can be formed. In such regions where adjacent belt modules are tilted with respect to each other, gaps are normally opened between two adjacent belt modules. This makes it possible to clean the gaps between the adjacent belt modules, in particular link ends, which is particularly important in the food industry. Steam or hot water, which may include cleaning agents and disinfectants, can be used for such cleaning purposes. 
     In some cases, the modular conveyor belts need to have comparatively small belt modules and small pitches, in particular pitches of 2.54 cm (1 inch) or smaller. This brings up problems with the driving of the modular conveyor belt, because the driving teeth of a drive sprocket cannot be made too thin, otherwise they break easily. In order to be still able to use teeth which are thick enough to not break, a conveyor design has been found where the teeth of a drive sprocket contact only every second belt module row. Such a design is, however, somewhat problematic, because only a limited number of belt modules have to relay the driving force of the drive sprocket to the remaining belt modules of the modular conveyor belt. This can cause stability problems and a significantly increased wear of the modular conveyor belt. To minimise these problems, adjacent belt modules of adjacent rows of belt modules are connected by intercalating link ends provided over their whole lengths. A disadvantage is that the cleaning of such belt modules is somewhat cumbersome. 
     U.S. Pat. No. 4,556,142 A discloses another conveyor with a modular conveyor belt, where drive sprockets having two parallel series of teeth engage alternately drive surfaces on first rows of belt modules and drive surfaces on second rows of belt modules, wherein the first rows of belt modules and the second rows of belt modules are alternately interlinked with each other. The disclosed modular conveyor belt is prone to agglomeration of dirt or bacteria and cumbersome to clean. 
     There is a need for modular conveyor belts, in particular modular conveyor belts having comparatively small belt modules and small pitches, in particular pitches of 2.54 cm (1 inch) or smaller, which are better cleanable and/or less prone to contamination. 
     The present invention meets the above-described need by providing a modular conveyor belt according to independent claim  1  and a conveyor comprising such a modular conveyor belt according to independent claim  13 . Particularly advantageous embodiments of the invention result from the dependent claims. 
     The core of the invention lies in the following: A modular conveyor belt comprises a plurality of first rows of one or more belt modules and a plurality of second rows of one or more belt modules. Each belt module comprises at least two link sections and the first rows and the second rows are alternately interlinked with each other by intercalating link sections of adjacent belt modules of adjacent first and second rows. Each of the first rows comprises a first drive surface for receiving a force-transmitting surface of a first series of force-transmitting surfaces of a drive sprocket, the first drive surfaces of the first rows being arranged along a first line in a direction of belt travel. Each of the second rows comprises a second drive surface for receiving a force-transmitting surface of a second series of force-transmitting surfaces of the drive sprocket or a further drive sprocket, the second drive surfaces of the second rows being arranged along a second line in the direction of belt travel. The first line and the second line are offset with respect to each other. At least one of the belt modules of one of the first rows comprises a first middle section between two link sections, which has a first flat top surface and is arranged adjacent to a second middle section between two link sections of an adjacent belt module of one of the adjacent second rows having a second flat top surface. The first flat top surface and the second flat top surface have a different width in the direction of belt travel at least in adjacent zones and the first and second middle sections are devoid of linking means. 
     By providing a first line of first drive surfaces on the first rows of one or more belt modules and a second line of second drive surfaces on the second rows of one or more belt modules, the driving force of the at least one drive sprocket can be transmitted to each row of one or more belt modules. This allows to design the drive surfaces of the belt modules, the force-transmitting surfaces of the drive sprocket(s) and the connections between adjacent belt modules of adjacent rows smaller and less robust than in case where the driving force of the at least one drive sprocket is transmitted to only every alternate row of belt modules. It is to be noted that a less robust design usually implies that the respective components can be reduced in size and/or can be produced of less robust material and/or with thinner material layers. 
     Due to the offset with respect to each other of the first line of first drive surfaces and the second line of second drive surfaces (in the width direction of the modular conveyor belt, perpendicular to the direction of belt travel), more space is available for the arrangement of the drive surfaces in successive first and second rows of one or more belt modules. The offset is preferably comparatively small, preferably no unused drive surface is placed between those two lines of drive surfaces. Instead of two lines of drive surfaces, a larger number like three, four, five or six lines of drive surfaces can be foreseen. Those lines may be arranged as blocks of preferably neighbouring (adjacently placed) lines of drive surfaces. Of course, a plurality of such blocks can be used as well. In particular, those blocks can be spaced at a certain distance from each other. As an example, if a belt module comprises two (or possibly more) link sections, a plurality or each of the link sections may be provided with a block of drive surfaces, being part of a block of lines of drive surfaces seen over a plurality of rows of one or more belt modules. 
     The fact that at least one of the belt modules of one of the first rows comprises a first middle section between two link sections, which has a first flat top surface and is arranged adjacent to a second middle section between two link sections of an adjacent belt module of one of the adjacent second rows having a second flat top surface, wherein the first flat top surface and the second flat top surface have a different width in the direction of belt travel at least in adjacent zones, allows to arrange the middle sections of adjacent belt modules in a space-saving manner, and nevertheless to provide an essentially closed combined flat top surface, if desired. In particular the middle sections are thus better cleanable and less prone to contamination. 
     The fact that the first and second middle sections are devoid of linking means makes them better cleanable and less prone to contamination. 
     Preferably, the second rows of one or more belt modules are devoid of first drive surfaces and/or the first rows of one or more belt modules are devoid of second drive surfaces. Because the second rows do not need first drive surfaces and the first rows do not need second drive surfaces, it is advantageous to avoid such unnecessary drive surfaces. This simplifies the design and makes the belt modules better cleanable and less prone to contamination. 
     In an advantageous embodiment of the modular conveyor belt according to the invention, the link sections comprise a first plurality of link ends extending in a direction of belt travel and having a pivot rod opening disposed therein in a direction substantially perpendicular to the direction of belt travel, and a second plurality of link ends extending in a direction opposite to the direction of belt travel and having a pivot rod opening disposed therein in a direction substantially perpendicular to the direction of belt travel, the first plurality of link ends of one of the link sections and the second plurality of link ends of an adjacent link section of an adjacent belt module being intercalated and hingedly connected by at least one pivot rod disposed through at least some of the pivot rod openings. 
     The hingedly connecting of link sections of adjacent belt modules by intercalating link ends and pivot rods is easy to realise. Moreover, using such a design makes the modular conveyor belt compatible with present designs of modular conveyor belts. Therefore, the modular conveyor belt can be used in combination with present apparatuses with minor modifications, or even without any modification at all. 
     Advantageously, the distance between two successive first drive surfaces along the first line in the direction of belt travel is equal to the distance between two successive second drive surfaces along the second line in the direction of belt travel, and preferably the first drive surfaces and the second drive surfaces are offset in the direction of belt travel with respect to each other by a half of this distance. With such a design, a particularly advantageous distribution of the introduced forces can be realised. Such a design is also advantageous for geometrical reasons and can easily be realised, for example with two different sets of belt modules or even with a single set of belt modules comprising first and second drive surfaces. 
     In a preferred embodiment, at least one of the first drive surfaces and/or the second drive surfaces is formed by a bordering wall of an indentation on a bottom side of one of the belt modules and/or by an end surface of one of the link ends. This is easily realisable and allows to reduce the amount of material used for the belt modules and/or to use elements of the belt module that have to be provided anyhow (albeit it may be necessary to adapt the respective element to serve as a drive surface). 
     Preferably, adjacent first and second middle sections of adjacent belt modules have complementary first and second flat top surfaces so as to form an essentially closed combined flat top surface when the adjacent belt modules are arranged in a substantially straight line. This makes the belt modules less prone to contamination, in particular their bottom sides. 
     In an advantageous embodiment, the belt modules of the first rows and of the second rows are identical, but the belt modules of the second rows are turned by 180° with respect to the belt modules of the first rows. In this way, a single type of belt modules is sufficient, which may facilitate production and maintenance of the modular conveyor belt. In particular, only a single type of spare belt modules has to be stored. 
     In an alternative advantageous embodiment, the belt modules of the first rows and of the second rows are of a different design. For example, a second middle section may be wider in the direction of belt travel than a first middle section. Such a design might prove to be advantageous as well, since the individual belt modules may be designed less complex and/or may be optimised for a certain functionality of the modular conveyor belt. 
     In a preferred embodiment of the modular conveyor belt according to the invention, between a belt module of one of the first rows and an adjacent belt module of one of the adjacent second rows a gap is formed which broadens towards the bottom of the modular conveyor belt. With such a design, it is possible to further improve the cleanability of the modular conveyor belt, in particular when using impinging fluid jets for cleaning, due to the fluid guiding effect of the gap. Namely, impinging fluid can be directed in a way that cleaning of a proximity region (gap region between two adjacent belt modules) can be improved. This may be particularly the case for the region of the middle sections. 
     Advantageously, the belt modules are designed and arranged such that the gap is essentially closed at a top surface of the modular conveyor belt when the adjacent belt modules of the first and second rows are aligned along a substantially straight line and such that the gap is open at the top surface of the modular conveyor belt when the adjacent belt modules of the first and second rows are tilted with respect to each other. In this way, it is less likely that any goods (or parts thereof) that are to be transported by the modular conveyor belt can get stuck between adjacent belt modules or may even pass through between two adjacent belt modules (and consequently get lost). Nevertheless, it is still possible to provide a very effective cleaning possibility in certain areas, in particular in areas where the modular conveyor belt runs over a drive sprocket or idler and is returned. 
     In a preferred embodiment, at least one of the belt modules of the modular conveyor belt comprises on its bottom side at least one fluid guiding structure designed and arranged so as to deflect a fluid jet impinging on the bottom side and guide the deflected fluid jet towards one of the adjacent belt modules of one of the adjacent rows. 
     Since fluid jets are frequently used for cleaning purposes in combination with modular conveyor belts, in particular in food industry, those fluid jets can be directed towards portions of the modular conveyor belt that are particularly prone to agglomeration of dirt or bacteria and/or that are problematic to be reached by a fluid jet that comes directly out of a fluid nozzle (no direct line-of-sight), when using at least one fluid guiding structure. A fluid jet that comes out of a nozzle can be directed to the fluid guiding structures of the modular conveyor belt and is then deflected or redirected by the fluid guiding structures into a different direction (as compared to the original direction of the fluid jet). In particular, the deflected fluid jet is guided into a direction, in particular towards the adjacent belt modules of one of the adjacent rows, where a cleaning action of the fluid jet is particularly desirable. This can be an area that can hardly be reached by a directly impinging fluid jet; an area that needs a particularly thorough cleaning; an area, where a cleaning process is more effective, if the fluid jet impinges in a certain direction (for example because particles will be washed out of the modular belt); and the like. 
     For example, the fluid guiding structure can be shaped in a way that the aiming point/outflow direction, towards which the fluid jet is directed or guided, remains more or less constant during a forward movement of the modular conveyor belt in its moving direction or direction of belt travel (at least when being at certain repetitively occurring positions). However, additionally or alternatively, the fluid guiding structure can be designed in a way that the aiming point and/or direction, where the impinging fluid jet is directed to, varies during the forward movement of the modular conveyor belt. The impinging fluid jet can impinge in a direction that is essentially perpendicular to the respective bottom surface of the belt module, or can be tilted with respect to the belt module, for example at an angle of up to 10°, 20°, 30°, 40° or 50° (with respect to the perpendicular direction). The fluid guiding structure can be shaped in a way that the cross section of the impinging fluid jet remains more or less unaltered. Additionally or alternatively, the cross section of the impinging fluid jet can be influenced by the fluid guiding structure as well. 
     A region, where two adjacent belt modules of the first and second row of one or more belt modules come close to each other (and possibly may touch each other, at least at certain positions during a movement cycle of the modular conveyor belt), may be called a proximity region. It is to be noted that such a proximity region typically necessitates a thorough cleaning, since in these regions the top surface of the modular conveyor belt, onto which goods are placed, is interrupted by a small gap. As an example, if foodstuff is transported, any fluid that flows out of the goods will usually flow through the small gap between two adjacent belt modules. Therefore, thorough cleaning of the respective region is important. 
     Another region that is somehow problematic with respect to cleaning considerations is the region of the link ends. This is not only because portions of the link ends are arranged in the proximity region, but also because in the link end region, the design of the modular conveyor belt is typically relatively complicated (at least on the bottom side of the belt modules) and typically has some regions that are hard to reach from the outside. Quite often there will be areas that cannot be reached by a line-of-sight axis from the outside and are therefore problematic to clean with directly impinging fluid jets. Only for completion, it should be noted that the fluid jet can for example contain water (in particular water at an elevated temperature and/or water containing some cleansing additive and/or some disinfectant). However, the advantages of the presently proposed modular conveyor belt can be achieved with essentially all kinds of fluid. When talking about fluid jets, certainly a different shape of a water stream can be chosen as well. As an example, some kind of a water curtain can be used as well. 
     Advantageously, at least one of the fluid guiding structures comprises an outwardly fan-shaped portion designed and arranged so as to direct and spread an impinging fluid jet towards one of the adjacent belt modules of one of the adjacent rows. With such a design, it is possible to direct the fluid towards a comparatively large portion of the modular conveyor belt, while still using a comparatively small fluid jet. Furthermore, it is possible to split up the fluid jet into a plurality of fluid jets (where the resulting fluid jets need not necessarily be separate from each other; i.e. some kind of a fluid curtain might be created). In this way, it is particularly simple to clean the side surfaces of the link ends, in particular of link ends that have a pivot rod opening. In particular, a contact region between a pivot rod opening of a link end and a pivot rod can be cleaned more easily using such a design. 
     When talking about a fan-shaped portion, this preferably relates to an arrangement where a circular jet with a comparatively small diameter is spread over a certain width (in particular in the widthwise direction of the modular conveyor belt), while its height remains comparatively small (for example about the same size like the original diameter of the impinging fluid jet). This can be reached by some kind of V-shaped channel, where the opening angle of the channel can be up to 10°, 20°, 30°, 40° or 50° (where a lower limit for the angle can be 0° or one of the previously mentioned angles). 
     Preferably, at least one of the fluid guiding structures is shaped without edges or corners. The avoidance of edges and corners, i.e. the use of rounded or arcuate shapes, results in a smoother deflection and guidance of an impinging fluid jet. Turbulences can be reduced. 
     In a preferred embodiment of the modular conveyor belt according to the invention, at least one of the fluid guiding structures has a channel-like design. Such a channel-like design makes it possible to deflect and guide the impinging fluid jet into the desired direction. 
     Preferably, at least one of the fluid guiding structures is arranged between two of the link ends of one of the belt modules. This makes it possible to easily deflect and guide the impinging fluid jet to side surfaces of both link ends and to the front surface and both side surfaces of an intercalating link end of an adjacent belt module of an adjacent row of one or more belt modules. 
     In an advantageous embodiment, at least one of the fluid guiding structures has a trough-like shape. Such a trough-like shape makes it easier to deflect and guide the impinging fluid jet to the front surface and both side surfaces of an intercalating link end of an adjacent belt module of an adjacent row of one or more belt modules. 
     It should be mentioned that in case a plurality of fluid guiding structures are used, those fluid guiding structures can have essentially the same design and/or can have different designs. Of course, it is possible to use a first fraction of the fluid guiding structures with a first design, while a second fraction of the fluid guiding structures can have a different design. The fractional shares may vary, as well as the number of different designs. 
     A conveyor according to the invention comprises a modular conveyor belt according to the invention as discussed above and at least one drive sprocket comprising a first series of force-transmitting surfaces for engaging the first drive surfaces of the first rows of one or more belt modules and a second series of force-transmitting surfaces for engaging the second drive surfaces of the second rows of one or more belt modules. 
     In an advantageous embodiment, the force-transmitting surfaces for engaging the first drive surfaces are provided on a first series of teeth of the at least one drive sprocket and the force-transmitting surfaces for engaging the second drive surfaces are provided on a second series of teeth of the at least one drive sprocket, wherein the first series of teeth and the second series of teeth are preferably arranged offset from each other in the direction of belt travel of the modular conveyor belt. 
     Advantageously, the first series of teeth and the second series of teeth are arranged adjacent to each other in a direction perpendicular to the direction of belt travel of the modular conveyor belt. 
     Furthermore, a fluid supply system with at least one fluid nozzle or orifice may be provided that may be arranged facing the bottom side of the modular conveyor belt and/or may be arranged in the vicinity of a drive sprocket and/or an idler. This way, it is easy to efficiently clean the modular conveyor belt. 
    
    
     
       Further advantages, features, and objects of the invention will be apparent from the following detailed description of two embodiments of a modular conveyor belt according to the invention in conjunction with the associated drawings, wherein the drawings show: 
         FIG. 1 —an arrangement of three adjacent belt modules of three adjacent rows according to a first embodiment of the modular conveyor belt in a bottom perspective view; 
         FIG. 2 —a first type of belt module of the modular conveyor belt of  FIG. 1  in a bottom view; 
         FIG. 3 —the first type of belt module shown in  FIG. 2  in a top view; 
         FIG. 4 —an enlarged bottom view of a link section and a portion of the middle section of the first type of belt module shown in  FIG. 2 ; 
         FIG. 5 —a second type of belt module of the modular conveyor belt of  FIG. 1  in a bottom view; 
         FIG. 6 —the second type of belt module shown in  FIG. 5  in a top view; 
         FIG. 7 —an enlarged bottom view of a link section and a portion of the middle section of the second type of belt module shown in  FIG. 5 ; 
         FIG. 8 —a side view of the arrangement of three adjacent belt modules of  FIG. 1 ; 
         FIG. 9 —a perspective view of the first embodiment of the modular conveyor belt of  FIG. 1  engaged with a drive sprocket; 
         FIG. 10 —the arrangement of  FIG. 9  in a side view; 
         FIG. 11 —the arrangement of  FIG. 9  in a plan view from inside the modular conveyor belt; 
         FIG. 12 —a belt module of a second embodiment of the modular conveyor belt in a bottom view; 
         FIG. 13 —the belt module shown in  FIG. 12  in a top view; and 
         FIG. 14 —an arrangement of belt modules according to  FIG. 12  in a way to form a modular conveyor belt. 
     
    
    
     The following observations apply in respect of the description which follows: where, for the purpose of clarity of the drawings, reference signs are included in a Figure but are not mentioned in the directly associated part of the description, reference should be made to the explanation of those reference signs in the preceding or subsequent parts of the description. Conversely, to avoid overcomplication of the drawings, reference signs that are less relevant for immediate understanding are not included in all Figures. In that case, reference should be made to the other Figures. 
       FIG. 1  shows a bottom side  11  of a part of a modular conveyor belt  10  according to a first embodiment in a perspective view. Three adjacently arranged belt modules are shown, wherein a belt module  40  of one type is arranged between two belt modules  20  of a different type. Each belt module  20  comprises two link sections  21  and a first middle section  22  between the two link sections  21 , as can be better seen in  FIGS. 2 and 3 . The belt module  40  comprises two link sections  41  and a second middle section  22  between the two link sections  41 , as can be better seen in  FIGS. 5 and 6 . 
     Each belt module  20  forms a first row of one belt module, whereas the belt module  40  forms a second row of one belt module. The whole modular conveyor belt  10  comprises a plurality of first rows of one belt module  20  and a plurality of second rows of one belt module  40 , wherein the first rows and the second rows are alternately interlinked with each other by intercalating link sections  21 ,  41  of adjacent belt modules  20 ,  40  of adjacent first and second rows. 
     The first and second middle sections  22 ,  42  of the belt modules  20 ,  40  of the first and second rows are devoid of linking means. The first middle section  22  of the belt module  20  has a first flat top surface  220  and tapers to the bottom side  11 , as can be best seen in  FIGS. 2 to 4 and 9 . The second middle section  42  of the belt module  40  has a second flat top surface  420  and a plate-like shape with a concave channel-like recess  421  at the bottom side  11 , as can be best seen in  FIGS. 1, 5 to 7 and 9 . The first flat top surface  220  has a first width in the direction of belt travel, whereas the second flat top surface  420  has a second width in the direction of belt travel T, which is bigger than the first width. The first flat top surface  220  and the second flat top surface  420  are complementary so as to form an essentially closed combined flat top surface when the adjacent belt modules  20 ,  40  are arranged in a substantially straight line as shown in  FIG. 1 . 
     Regarding the link sections, it is to be noted that, as can be seen from  FIGS. 1 to 4 , each link section  21  comprises a first plurality of link ends  23  extending in a direction of belt travel T and a second plurality of link ends  29  extending in a direction opposite to the direction of belt travel T. The link ends  23  have each a pivot rod opening  24  disposed therein in a direction substantially perpendicular to the direction of belt travel T. The pivot rod openings  24  are aligned with each other, i.e. they form a line-of-sight tunnel. The link ends  29  have each a pivot rod opening  34  disposed therein in a direction substantially perpendicular to the direction of belt travel T. The pivot rod openings  34  are aligned with each other, i.e. they form a line-of-sight tunnel. 
     As can be seen from  FIGS. 1 and 5 to 7 , each link section  41  comprises a first plurality of link ends  43  extending in a direction of belt travel T and a second plurality of link ends  49  extending in a direction opposite to the direction of belt travel T. The link ends  43  have each a pivot rod opening  44  disposed therein in a direction substantially perpendicular to the direction of belt travel T. The pivot rod openings  44  are aligned with each other, i.e. they form a line-of-sight tunnel. The link ends  49  have each a pivot rod opening  54  disposed therein in a direction substantially perpendicular to the direction of belt travel T. The pivot rod openings  54  are aligned with each other, i.e. they form a line-of-sight tunnel. 
     The first plurality of link ends  23 ,  43  of one of the link sections  21 ,  41  and the second plurality of link ends  29 ,  49  of an adjacent link section  21 ,  41  of an adjacent belt module  20 ,  40  are intercalated such that the respective pivot rod openings  24 ,  34 ,  44 ,  54  are aligned, i.e. form a line-of-sight tunnel, and hingedly connected by a pivot rod disposed through the aligned pivot rod openings  24 ,  34 ,  44 ,  54 . The intercalation of link ends  23 ,  29 ,  43 ,  49  is made possible by interspaces  25  between two link ends  23  or between two link ends  29 , which have a width which is bigger than the width of a link end  43  or  49 , and by interspaces  45  between two link ends  43  or between two link ends  49 , which have a width which is bigger than the width of a link end  23  or  29 . 
     Referring in particular to  FIGS. 2 and 4 , the belt modules  20  of the first rows comprise a plurality of indentations  30  on the bottom side of the link sections  21 , each indentation  30  being arranged in a region between a link end  23  and a link end  29 . A bordering wall of an indentation  30  forms a first drive surface  26  for receiving a force-transmitting surface  83  of a first series of force-transmitting surfaces  83  of a drive sprocket  80 , see  FIGS. 9 to 11 . 
     Referring in particular to  FIGS. 5 and 7 , the belt modules  40  of the second rows comprise a plurality of indentations  46  on the bottom side of the link sections  41 , each indentation  46  being arranged in a region between a link end  43  and a link end  49 . A bordering wall of an indentation  46  forms a second drive surface  48  for receiving a force-transmitting surface  84  of a second series of force-transmitting surfaces  84  of the drive sprocket  80 , see  FIGS. 9 to 11 . 
       FIGS. 9, 10 and 11  show the modular conveyor belt  10  in a situation, where it is engaged with the drive sprocket  80  used for driving the modular conveyor belt  10 .  FIG. 9  shows a perspective view of the situation,  FIG. 10  is a side view, and  FIG. 11  is a plan view from inside the modular conveyor belt. 
     As can be seen, the drive sprocket  80  comprises a first series of teeth  81  and a second series of teeth  82  that are arranged offset from each other in the direction of belt travel T of the modular conveyor belt  10  (rotation direction of the drive sprocket  80 ). The teeth  81  of the drive sprocket  80  engage into the indentations  30  of the belt modules  20  of the first rows, whereas the teeth  82  of the drive sprocket  80  engage into the indentations  46  of the belt modules  40  of the second rows. The force-transmitting surfaces  83  engaging the first drive surfaces  26  are provided on the first series of teeth  81  and the force-transmitting surfaces  84  engaging the second drive surfaces  48  are provided on the second series of teeth  82 . 
     It can be seen from  FIGS. 9, 10 and 11  that the first series of teeth  81  and the second series of teeth  82  of the drive sprocket  80  are slightly offset from each other in an axial direction  85  of the drive sprocket  80  (width direction of the modular conveyor belt  10 ). It follows that the first drive surfaces  26  of the first rows engaged by the first series of teeth  81  are arranged along a first line in a direction of belt travel T, the second drive surfaces  48  of the second rows engaged by the second series of teeth  82  are arranged along a second line in the direction of belt travel T, and the first line and the second line are offset with respect to each other. 
     Other advantageous features of the belt modules  20  and  40  are fluid guiding structures, which are best visible in  FIGS. 1, 4 and 7 . As can be seen there, the belt modules  20 ,  40  comprise on the bottom side a plurality of fluid guiding structures  27  and  47 , respectively, designed and arranged so as to deflect a fluid jet impinging on the bottom side and guide the deflected fluid jet towards one of the adjacent belt modules of one of the adjacent rows. Each fluid guiding structure  27 ,  47  comprises an outwardly fan-shaped portion, which is somewhat V-shaped, designed and arranged so as to direct and spread an impinging fluid jet towards one of the adjacent belt modules of one of the adjacent rows. The fluid guiding structures  27 ,  47  are arranged in the link sections  21 ,  41  between the link ends  23 ,  29 ,  43 ,  49  and the indentations  30 ,  46 . 
     The fluid guiding structures  27 ,  47  have preferably an arcuate shape, so that a fluid jet that impinges in a direction approximately perpendicular to the bottom surface of the belt modules  20 ,  40  is redirected in a direction that is somewhat parallel to the moving direction of the modular conveyor belt  10  (or at a certain angle of maximal about 20°). 
     The fluid guiding structures  27 ,  47  are made with rounded or arcuate shapes, without edges or corners. They have a channel-like design for guiding the deflected fluid jet towards the adjacent belt module of the adjacent row. They also have a trough-like shape to deflect and guide the impinging fluid jet to the front surface and both side surfaces of the intercalating link end of the adjacent belt module. 
       FIG. 8  shows another important feature, namely that between a belt module  20  of one of the first rows and an adjacent belt module  40  of one of the adjacent second rows a gap  61  is formed which broadens towards the bottom  11  of the modular conveyor belt  10 . The belt modules  20 ,  40  are designed and arranged such that the gap  61  is essentially closed at a top surface  12  of the modular conveyor belt  10  when the adjacent belt modules  20 ,  40  of the first and second rows are aligned along a substantially straight line, as this is shown in  FIG. 8 , and such that the gap  61  is open at the top surface  12  when the adjacent belt modules  20 ,  40  of the first and second rows are tilted with respect to each other. 
       FIGS. 12 to 14  show a second embodiment of a modular conveyor belt  100  according to the invention. In contrast to the first embodiment of a modular conveyor belt  10 , employing two different types of belt modules  20 ,  40 , the modular conveyor belt  100  uses only one type of specially shaped belt modules  110 .  FIG. 12  shows such a belt module  110  in a bottom view, whereas  FIG. 13  shows the belt module  110  in a top view. 
     The belt module  110  has two distinct halves  111 ,  112 . The half  111  comprises a link section  121  and a middle section portion  122 . The half  112  comprises a link section  141  and a middle section portion  142 . The middle section portions  122  and  142  form together the middle section of the belt module  110 . 
     The design of the link section  121  comprising a first plurality of link ends  123 , a second plurality of link ends  129 , indentations  130  and drive surfaces  126 ,  128  and of the middle section portion  122  of the first half  111  (right side in  FIG. 12 ) of belt module  110  is similar to the design of the link sections  21  and the middle section  22  of the first type of belt module  20 , as shown in the  FIGS. 2 to 4 . The design of the link section  141  comprising a first plurality of link ends  143 , a second plurality of link ends  149 , indentations  140  and drive surfaces  146 ,  148  and of the middle section portion  142  of the second half  112  of belt module  110  (left side in  FIG. 12 ) is similar to the design of the link sections  41  and the middle section  42  of the second type of belt module  40 , as shown in  FIGS. 5 to 7 . 
       FIG. 14  shows the arrangement of several belt modules  110  in a way to form a modular conveyor belt  100 . For doing this, every second belt module  110  is turned around a centre axis by 180°. In this way, a plurality of first rows of one belt module  110  and a plurality of second rows of one belt module  110  is formed, wherein the belt modules  110  of the first rows and of the second rows are identical, but the belt modules of the second rows are turned by 180° with respect to the belt modules of the first rows. Similar to the first embodiment of a modular conveyor belt  10 , the belt modules  110  of the first rows and of the second rows are interlinked by pivot rods  150 . 
     An advantage of the design idea of a modular conveyor belt  100  according to the second embodiment is that only a single type of belt module  110  is necessary, so that storage of spare parts can be simplified. Further, only one set of tools for injection moulding moulds for manufacture of the belt modules  110  is necessary.