Abstract:
A chain link for a curved conveyor chain, the chain link comprising a base body and a bolt, the base body having an articulation section and a fork section and a carrier means for carrying material that is to be conveyed, the bolt being elongated and designed in a circular cylindrical manner in at least one central section. In the articulation section, a bolt opening is provided through which the bolt can pass and can rotate relative to at least two axes. The fork section has an articulation recess for receiving the articulation section of an adjoining identical chain link, the fork section having two opposite bolt recesses which can receive the opposite ends of the bolt of the adjoining chain link. The articulation and fork sections of two adjoining, identical chain links are maintained at a distance by two slide sections.

Description:
This application is a 35 U.S.C. §371 National Stage Application of PCT/EP2012/065636, filed on Aug. 10, 2012, which claims the benefit of priority to Serial No. DE 10 2011 112 396.6, filed on Sep. 3, 2011 in Germany, the disclosures of which are incorporated herein by reference in their entirety. 
     BACKGROUND 
     The disclosure relates to a chain link for a curved conveyor chain. 
     DE 100 27 229 A1 discloses a chain link for a curved conveyor chain. According to  FIGS. 1 and 2 , the chain link comprises a main body and a pin (not shown). The main body, which in this case is integral, comprises an articulation section  10  and a fork section  11 . A driver means in the form of a flat supporting surface  3 , by means of which material (not shown) to be conveyed can be taken along by friction, is provided on the upper side of the main body. Other driver means, e.g. catches, fins or brushes projecting vertically from the supporting surface, are also known as substitutes for the flat supporting surface. A multi-part main body is often provided in combination with the last-mentioned driver means. 
     The pin is of elongate design, being of circular cylindrical design over the entire length. In the articulation section a pin opening  9  is provided through which the pin passes in a manner which allows it to rotate relative to two axes. Here, the pin opening is configured similarly to  FIG. 4  in EP 0 569 071 B2, i.e. the entire pin opening is provided fully in the main body, having a minimum cross-sectional area in the center, which widens toward the two orifices, ensuring that the pin has the desired ability for rotation. EP 1 311 446 B1 discloses an alternative articulation construction, in which the pin opening is intersected by a circular cylindrical aperture, in which a special articulation part is inserted. The articulation part in turn has an opening, which is matched to the pin. The last-mentioned design of articulation can transmit significantly higher tensile chain forces than that shown in DE 100 27 229 A1. 
     A fork recess  7  for accommodating the articulation section of an adjacent identical chain link is provided on the fork section in DE 100 27 229 A1. Two pin apertures in the form of circular cylindrical holes are furthermore provided in the fork section, serving to accommodate the pin of the adjacent chain link. A plurality of slide sections  4  made of fiber reinforced polytetrafluoroethylene (trade name “Teflon”) are furthermore provided on the main body, which is made of polyoxymethylene. The slide sections are intended to reduce the frictional forces imposed by the chain links on the chain guides. 
     The disadvantage of the chain link according to DE 100 27 229 A1 is that both the articulation section and the fork section are composed of the same material. During the operation of the conveyor chain, these materials rub directly against one another and produce squealing noises. This problem occurs especially with polyoxymethylene, the preferred material for the chain links of a conveyor chain. However, it can be observed in general that materials of the same kind, especially plastics, which rub against one another under load produce squealing noises owing to the stick-slip effect. One already known solution to this problem is to provide polyoxymethylene with various additives which improve its ability to slide. As a result, the tendency to generate noise is reduced. However, such materials are very expensive. 
     It is the object of the disclosure to reduce or completely avoid the above-described generation of noise in a low-cost manner. 
     SUMMARY 
     This object is achieved by arranging two slide sections opposite one another on the articulation section, wherein they surround the pin, wherein the main bodies of two adjacent identical chain links are held at a distance by the slide sections in such a way that the articulation and fork sections thereof touch only at the slide sections. 
     This excludes the possibility that the identical materials of the articulation and fork sections will touch since they are held at a distance by the slide sections. As a result, squealing noises are excluded. As regards the driver means, the aim is likewise to ensure that they do not touch. Particularly in the case of driver means which project a long way from the articulation or fork section, such as catches, fins or brushes, contact cannot be completely excluded, at least on bends, however. However, such contact is harmless since such driver means are very flexible and consequently the frictional forces which occur in the event of contact are low. Accordingly, there is no risk of noise generation if the driver means touch. 
     As regards the spatial extent of the sections composed of a different material from the main body, it should be noted that these can, of course, be significantly larger than the slide sections per se. In particular, consideration may be given to the entire articulation section being composed of a different material from the fork section. In the context of the present application, the slide section should be taken to mean the region in which the articulation section and the fork section can enter into sliding contact during the operation of the conveyor chain. 
     Advantageous developments and improvements of the disclosure are indicated in the dependent claims. 
     The material of the main body and of the slide section can in each case be one of the materials polyoxymethylene (POM), polybutylene terephthalate (PBT), polyamide (PA), polypropylene (PP), polyethylene (PE), polybutylene succinate (PBS), polyvinylidene fluoride (PVDF), polycarbonate (PC) or polyethylene terephthalate (PET), wherein the main body is preferably composed of polyoxymethylene and the slide sections are preferably composed of polyamide. All the materials mentioned are suitable for the injection molding of plastics and offer sufficient strength and wear resistance for use in a conveyor chain link. The materials mentioned can be provided with additives and/or with fiber reinforcement. 
     The main body is preferably composed of polyoxymethylene. This material has the required mechanical properties for a conveyor chain link and, at the same time, is low-cost. Moreover, this material has long proven itself for this use. Tests by the applicant have shown that polyamide is particularly suitable as a material for the slide sections if the main body is composed of polyoxymethylene. 
     The articulation section can have a bearing aperture having a circular cylindrical inner circumferential surface, which intersects the pin opening, wherein an articulation part is provided with a bearing section, wherein the bearing section has a circular cylindrical outer circumferential surface and is accommodated rotatably in the bearing aperture, wherein the bearing section has a circular cylindrical first opening, which extends transversely to the circular cylindrical outer circumferential surface thereof, wherein the slide sections are formed integrally on the articulation part. The articulation part can be produced from a different material overall than the main body, thus enabling each part to be produced independently at low cost, preferably by the injection molding of plastics. At the same time, the chain link proposed can transmit particularly high tensile chain forces. 
     The slide sections can each have a second circular cylindrical opening, which is arranged in alignment with the first opening. The second opening allows the pin to be passed through to enable the latter to engage in the fork section of the adjacent chain link. Moreover, the position of the slide section in the gap between the articulation section and the slide section is defined in a reliable positive manner by the pin. For this purpose, the second opening is preferably matched to the pin with a small clearance. 
     Each slide section can be assigned a connecting section, which connects the slide section integrally to the bearing section, wherein the connecting section rests in a sliding manner on the articulation section of the main body or is arranged at a slight spacing with respect to said body. The bearing section of the articulation part is separated from the slide section by the articulation section over virtually its entire extent. By means of a connecting section which is arranged in the immediate vicinity of or in sliding contact with the articulation section, it is nevertheless possible to connect the slide section integrally to the bearing section. It should be noted here that, as proposed above, the bearing section can be secured in terms of position already by means of the pin. Thus, the connecting section primarily ensures that the slide section does not twist relative to the pin, and therefore a thin-walled connecting section is fully sufficient. 
     A recess having a convexly curved bottom surface can be provided between the connecting sections in the region of an end face of the bearing section, said recess extending transversely to the pin over the entire width of the bearing section. Said recess ensures that the engagement of a driving sprocket into the articulation section of the chain link is not obstructed by the connecting section. Consequently, power transmission from the driving sprocket takes place virtually exclusively between the articulation section and the teeth of the driving sprocket. Consequently, the articulation part cannot be damaged by the corresponding driving forces. 
     On the side facing the bearing section, the slide section can have a circular cylindrical first surface coaxial with the bearing section, which surface rests on a matching second surface on the articulation section. As a result, the slide section rests over the full surface on the articulation section and, at the same time, a desired rotatability between adjacent chain links is possible. During this process, sliding movements take place between the first and second surfaces. The ensuing wear is low by virtue of the full-surface contact. 
     The slide section can have a flat third surface on the side facing away from the bearing section, wherein the opposite fourth surface on the fork section is likewise of flat design. In relation to the fork section of the adjacent chain link, the slide section can and should rotate only relative to the center line of the pin. This movement is made possible by said flat third and fourth surfaces, and any other movement is excluded. The third and fourth surfaces are preferably arranged perpendicular to the center line of the circular cylindrical section of the pin. The spacing between the first and third surfaces determines the spacing between the articulation section and the fork section of two adjacent chain links. 
     A guide bevel can be arranged on the slide section, adjoining the third surface. The spacing of the third surface on the sliding part is at most slightly less than the spacing of the fourth surface on the fork section. The guide bevel proposed facilitates the introduction of the articulation section by means of the articulation part into the fork section of the adjacent chain link during the assembly of the conveyor chain. 
     The slide sections can also be connected securely to the articulation section or to the fork section. Here, consideration is given, in particular, to producing the corresponding main body by two-component injection molding. In this case, a first part comprising both slide sections is preferably produced by injection molding. This first part is placed in the second injection mold for the finished main body and is then overmolded with a viscous plastic composition. In this way, the slide sections are secured positively and permanently on the rest of the main body composed of a different material. However, it should be noted here that producing a chain link of this kind is more expensive than producing a chain link in which the slide sections are formed integrally on the articulation part. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The disclosure is explained in greater detail below by means of the attached drawings, in which: 
         FIG. 1  shows an exploded view of a chain link according to the disclosure; 
         FIG. 2  shows a perspective view from above of a conveyor chain consisting of chain links in accordance with  FIG. 1 ; 
         FIG. 3  shows a bottom view of a conveyor chain consisting of chain links in accordance with  FIG. 1 ; 
         FIG. 4  shows a side view of a driving sprocket which is in engagement with a conveyor chain consisting of chain links in accordance with  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an exploded view of a chain link  10  according to the disclosure. The chain link  10  comprises an integral main body  13  made of polyoxymethylene, an integral articulation part  60  made of polyamide, and a pin  80  made of steel. The main body  13  and the articulation part  60  are each produced by injection molding of plastics. 
     The main body  13 , which is mirror-symmetrical overall, comprises an articulation section  40 , a fork section  20  and a driver means  14 . The driver means is in the form of a flat plate, which defines a conveying plane  12 . The flat plate  14  is provided with teeth  15  pointing in the conveying direction  11 , with the result that the teeth  15  of adjacent main bodies  13  of a conveyor chain engage in one another to ensure that the material (not shown) to be conveyed is supported as far as possible over the full surface, even on bends. The flat plate  14  is arranged so close to the articulation section  40  and the fork section  20  that it contributes to the transmission of the tensile forces in the conveyor chain. 
     The fork section  20  comprises two fork arms  23 , which together delimit an articulation recess  21 , which is provided to accommodate the articulation section  40  of an adjacent identical chain link. The fork arms  23  project vertically from the flat plate  14  and are rounded  27  in a semicircle at their end face pointing in the conveying direction  11 . Arranged at the center of the rounding  27  is a pin aperture  22  in the form of a circular cylindrical opening, in which the pin  80  is accommodated with slight play. In this case, the pin  80  is of circular cylindrical design over its entire length, wherein it is provided at both ends with a flat end face  82 , which has a chamfer  83  at the edge. The fork arms  23  each have a substantially Z-shaped profile with a first and a third section  24 ;  26  which extend parallel to the conveying direction  11  of the conveyor chain, wherein the intervening second section  25  slopes relative to the conveying direction  11 . The fork arms  23  each have a substantially constant wall thickness to ensure that they are not distorted during injection molding. The height of the fork arms  23  is furthermore constant to ensure that the lower boundary surface of the main body  13  is substantially flat. Around the pin aperture  22 , the fork arm  23  is provided with a reinforcement  28  to ensure that the compressive stresses in the pin aperture  22  caused by chain tension do not become impermissibly large. A driving tongue  30  is arranged on both second sections  25  of the fork arms on the side remote from the flat plate  14 . The driving tongue  30  extends parallel to the flat plate  14  and transversely to the conveying direction  11 , and is rounded in a semicircle on its front face. The driving tongue  30  is intended for engagement with a driving sprocket (not shown), which deflects the conveyor chain in a plane parallel to the conveying plane  12 . 
     The fork arms  23  merge integrally into the articulation section  40 . The articulation section  40  has a second surface  43 , which is of circular cylindrical design and is aligned perpendicularly to the conveying plane  12 . A fifth surface  44  is furthermore provided, said surface being of circular cylindrical design and extending parallel to the conveying plane  12 . The circle radii of the second and fifth surfaces  43 ;  44  are the same, and therefore the intersecting edges  46  thereof intersect at an angle of 90°. A bearing aperture  41  having a circular cylindrical inner circumferential surface is provided concentrically with the fourth surface, said aperture being in the form of a blind hole, with the result that it does not pierce the flat plate  14 . Arranged transversely to the bearing aperture  41  is a pin opening  42 , which passes through the entire articulation section  40 , intersecting the bearing opening  41 . The pin opening  42  is traversed by the pin  80 , wherein the pin  80  is rotatable relative to the center line of the bearing aperture  41 . The pin opening  42  is therefore in the form of an elongate hole which extends parallel to the conveying plane  12  in order to allow said rotatability. 
     The articulation part  60  is of mirror-symmetrical design and comprises a bearing section  61 , two slide sections  64  and two connecting sections  72 , which connect the associated slide section  64  to the bearing section  61 . The bearing section  61  is in the form of a circular cylinder, which is provided on its free end with a flat end face  62  and a chamfer  63 , wherein the bearing aperture  41  is matched to this shape substantially without play. At the opposite end, the connecting sections  72  are connected integrally to the bearing section  61 . The connecting sections  72  are substantially in the form of a flat rectangular plate, projecting perpendicularly from the bearing section  61 . The connecting sections  72  make sliding contact with the articulation section  40  or are arranged with a slight clearance relative to the latter. Provided between the connecting sections  72  is a recess  70 , which has a convexly curved bottom surface  71  that extends transversely to the pin  80  over the entire width of the bearing section  61 . The radius of curvature of said bottom surface  71  is the same as the radius of curvature of the fifth surface  44 , wherein said surfaces  71 ;  44  merge into one another without kinks and offsets as long as the conveyor chain is aligned straight. 
     The slide sections  64  are formed integrally with the associated connecting section  72  and project perpendicularly from the latter. The first surface  67  on the slide section, which faces the bearing section  61 , is of circular cylindrical design and formed concentrically with the bearing section  61  and rests substantially without a gap and in a slidable manner on the articulation section  40  at the second surface  43 , with the result that the articulation part  60  is rotatable in relation to the main body  13  relative to the center line of the bearing section  61 . On the side facing away from the bearing section  61 , the slide section  64  is provided with a flat third surface  68  which extends transversely to the conveying plane  12 . The third surface  68  rests on the fork arms  23  of the fork section  20  at a flat fourth surface  29 , with the result that the articulation part  60  can rotate relative to the associated fork section  20  only about the center line of the pin  80 . On both sides of the third surface  68  in the conveying direction  11 , a guide bevel  69  is provided on the slide section  64 . 
     The bearing section  61  is provided with a first circular cylindrical opening  65 , which extends transversely to the circular cylindrical outer circumferential surface thereof, wherein the two cylinder axes intersect. A second circular cylindrical opening  66  is arranged in alignment with the first opening  65  in each of the slide sections  64 . The pin  80  is accommodated with an interference fit in the first opening  65  and with slight play in the second opening  66 , and thus the slide section  64  surrounds the pin  80 . 
       FIG. 2  shows a perspective view of a conveyor chain consisting of chain links  10  as shown in  FIG. 1  from above. The conveyor chain is shown in a position as on a bend. The driver means  14  in the form of the flat plates form a conveying plane  12  insofar as the entire conveyor chain is moved in a plane. The teeth  15  of the flat plates  14  engage in one another, thus ensuring support for the material (not shown) to be conveyed substantially over the full surface, especially on the outside of the bend. Here, the bend radius is bounded at the bottom by the abutting flat plates  14  or teeth  15  on the inside of the bend, the conveyor line generally being designed in such a way that such contact does not take place. 
     The fork arms  23  of the fork section are arranged in such a way that they can likewise assume the function of a tooth of the flat plate  14 , wherein teeth of the kind present on the chain link according to EP 1 311 446 B1,for example, have been omitted between the fork arms  23 . Instead, the spacing between the flat plates of the adjacent chain links  10  has been made as small as possible at this point. 
       FIG. 3  shows a bottom view of a conveyor chain consisting of chain links  10  as shown in  FIG. 1 . It can be seen that the pin  80  is accommodated between the fork arms  23  of the fork section. Attention should furthermore be drawn to the sixth surface  45 , which is arranged between the fork arms  23 , wherein the sixth surface  45  lies on a common circular cylinder with the fifth surface  44 , said cylinder being arranged parallel to the conveying plane. Attention should furthermore be drawn to the chamfers  16  on the underside of the flat plate  14 . As can be seen in  FIG. 4 , the cross-sectional shape of the chamfer  16  is equidistant from the fifth surface  44  on the articulation section of the adjacent chain link  10 , with a small clearance, with the result that the clearance of the flat plates  14  in this region is small. The alignment of the articulation parts  60  relative to the fork arms  23  on a bend can furthermore be seen in  FIG. 3 . In particular, attention should be drawn to the fact that the third  68  and the fourth surface  29  touch. 
       FIG. 4  shows a side view of a driving sprocket  90 , which is in engagement with a conveyor chain consisting of chain links  10  in accordance with  FIG. 1 . Here, the conveyor chain is shown in longitudinal section. The conveyor chain is set in motion by means of the driving sprocket  90 . The driving sprocket  90  is provided, for example, with a hexagon socket  92 , by means of which it can be brought into positive rotary driving connection with an electric motor (not shown). In this case, the teeth  91  of the driving sprocket  90  engage with slight backlash between the third sections (No.  26 ;  FIG. 1 ) of the fork arms of the chain link  10 , resting against the sixth surface  45 . If the conveyor chain is to be driven in the opposite direction, the symmetrical teeth  91  of the driving sprocket  90  engage on the fifth surface  44  of the articulation section. The already discussed recess  70  between the connecting sections of the articulation part  60  is required to ensure that the articulation part  60  does not hinder the reversal of the direction of movement of the conveyor chain. 
     LIST OF REFERENCE SIGNS 
     
         
           10  chain link 
           11  conveying direction 
           12  conveying plane 
           13  main body 
           14  driver means or flat plate 
           15  tooth of the flat plate 
           16  chamfer 
           20  fork section 
           21  articulation recess 
           22  pin aperture 
           23  fork arm 
           24  first section of the fork arm 
           25  second section of the fork arm 
           26  third section of the fork arm 
           27  rounding of the fork arm 
           28  reinforcement 
           29  fourth surface 
           30  driving tongue 
           40  articulation section 
           41  bearing aperture 
           42  pin opening 
           43  second surface 
           44  fifth surface 
           45  sixth surface 
           46  intersecting edge 
           60  articulation part 
           61  bearing section 
           62  end face 
           63  chamfer 
           64  slide section 
           65  first opening 
           66  second opening 
           67  first surface 
           68  third surface 
           69  guide bevel 
           70  recess of the articulation part 
           71  bottom surface 
           72  connecting section 
           80  pin 
           81  central section of the pin 
           82  end face of the pin 
           83  chamfer of the pin 
           90  driving sprocket 
           91  tooth of the driving sprocket 
           92  hexagon socket