Patent Abstract:
The invention relates to a method for producing a plastic chain link, which has interspaced plates ( 10, 11 ) as well as lower and upper cross-connecting elements ( 15 ) that connect said plates, whereby at least one cross-connecting element is connected to one of the plates ( 10 ) in an articulated manner. According to the invention, at least one of the plates is firstly produced followed by the production of at least one of the cross-connecting elements while simultaneously forming a joint connection between one of the plates and one of the cross-connecting elements.

Full Description:
The present invention relates to a method for producing a chain link, and particularly to a chain link for a power transfer chain. 
   A chain link for a power transfer chain is known from DE 43 13 075 A1, which has two opposite link plates spaced apart from each other. The link plates are connected by a crosspiece. The crosspiece and link plates can be connected by releasable hinges that can be locked together. For this purpose, the crosspiece according to DE 43 13 075 A1 has shoulders on both sides that are connected to pivots with a round cross-section. The link plates have slits to accommodate the shoulders. In the region of the slits, the side plates have recesses for locking the combination and guiding of the pivots. By this configuration of the hinges, pivoting of the crosspiece by 180° is made possible, so that the crosspiece can be brought into any position. 
   Another variant of a chain link for a power transfer chain is known from DE 33 18 565 C2. The chain link has two opposite link plates at a spacing from each other, which are connected via a closing shackle. The closing shackle is connected to a link plate with a releasable hinge and can be locked to the other link plate with an elastic hook. DE 33 18 565 C2 proposes, for configuration of the hinge, that it consist of an exposed link axis formed in the free edge of a side plate, with a round cross-section flattened perpendicular to the link plate and rounded narrow sides, and of partially circular recesses provided with undercuts, formed in the end of the closing shackle. This closing shackle can be mounted on the axis and pivoted in the direction toward the opposite link plate, and then tightened to the link axis by force-fitting and shape-mating. This type of closing shackle can be pivoted on one side. 
   A plastic chain link for a power transfer chain is known from WO 95/28273. The chain link is formed by two spaced plates. These are connected by an upper and lower crosspiece. One of the crosspieces is articulated with a plate. This crosspiece is connected to the plate unreleasably. To form the link connection, the individual parts of the chain link are initially prepared. The crosspiece has a link head, from which a first tab and a second fork tab extend in fork-like fashion. The fork-like tabs run essentially parallel to each other on their insides. The link head with the molded-on tabs has a groove that corresponds to the peripheral cross-section of a pin. To form the link connection, the link head is joined to the tabs and pins, by means of an attachment tool with a mating shape. Force on the attachment tool and, optionally under the influence of heat, the tabs are deformed so that their ends are moved toward each other. In this way, enclosure of the pin by the tabs is achieved. The tabs are then deformed relative to each other, so that they come in contact and finally are joined to each other. The pin is fully enclosed by the link head with this connection. 
   SUMMARY OF THE INVENTION 
   The present invention provides an easier method for assembling link plates and crosspieces with a fewer number of parts The invention also provides a chain link having at least one crosspiece connected unreleasably to a plate. 
   The method according to the invention for producing a plastic chain link having spaced plates and lower and upper crosspieces connecting them is characterized by the fact that at least one crosspiece is articulated with one of the plates, during which at least one of the plates is formed, and then at least one of the crosspieces is formed during simultaneous formation of a link connection between one the plates and one of the crosspieces. 
   The present invention&#39;s configuration of the crosspiece does not require the tabs used in WO 95/28273 thereby eliminating additional steps necessary to deform the tabs and form the link connection. The method according to the present invention can be executed with simple tools. 
   In the present invention, a plate can be formed with a link axis during formation of the crosspiece by a peripheral angle greater than 80°. Plates having a link axis are known per se. The essential design of the plates can therefore be used to implement the assembly procedure according to the present invention. No fundamental change in design of the plate is therefore required in order to execute the method according to the invention. Also, the link axis is preferably formed in a recess. 
   According to another advantageous embodiment of the present invention that one plate can initially be formed with at least one link mount extending in the longitudinal direction of the plate. This link mount is preferably partially circular in cross-section, so that at least one link pivot can be formed in the link mount during formation of the crosspiece. The materials from which the plates or crosspieces are preferably made are chosen so that they do not prevent pivoting movement relative to each other. This expedient ensures that a pivoting movement of the crosspiece relative to the plate is made possible. 
   According to another advantageous embodiment of the present invention, it is proposed that the plate have a partially circular link mount in cross-section, whose peripheral angle is greater than 180° and less than 360°. In particular, it is proposed that the peripheral angle be about 270°. 
   According to another advantageous embodiment of the present invention, it is suggested that the plate have opposite link mounts, in which one link pivot each is formed during formation of the crosspiece. 
   To reduce the number of parts to be handled for a chain link, according to another advantageous variant of the invention, it is proposed that the plates and one crosspiece be formed as a one-piece, U-shaped part. 
   To reduce production costs and design expense of a chain link, it is proposed that the plates and/or crosspieces be designed to be substantially the same shape and dimensions. 
   Production of a chain link preferably occurs by forming at least one crosspiece according to the two-component injection molding method, with simultaneous formation of the link connection between one of the plates and one of the crosspieces. The two-component injection molding method can therefore be conducted in a single machine. 
   According to another advantageous variant of the present invention, it is proposed that the plates and/or at least one crosspiece be formed at least partially from different plastics. The plates and optionally one crosspiece preferably consist of a plastic chosen from the group of polyamides. To increase the stability of the plates and optionally of the U-shaped part, it is proposed that they be produced from polyamides provided with fiberglass reinforcement. 
   The plates and optionally the crosspiece can preferably be made from the plastic chosen from the group of polyacetals. The plastic, in particular, is POM here. 
   According to another aspect of the present invention, a plastic chain link is for a power transfer chain is provided having spaced plates and lower and upper crosspieces connecting them, in which at least one crosspiece is articulated with one of the plates, one section of the crosspiece seamlessly enclosing a link axis formed on the plate. By this expedient, the crosspiece is unreleasably joined to the plate. Owing to the fact that the plate and the crosspiece are seamlessly joined to each other, higher forces can act on the crosspiece without loosening of the crosspiece from the plate. The chain link according to the invention is particularly suited for the formation of a power transfer chain with very small chain links. 
   According to another advantageous design of a plastic chain link, it is proposed that at least one section of a crosspiece be formed with one of the plates during simultaneous formation of a link connection. 
   The section of a crosspiece preferably encloses a link axis of the plate over a peripheral angle greater than 180°. 
   According to another advantageous variant of the chain link, it is preferred that one plate have at least one link mount extending in the longitudinal direction of the plate, into which a link pivot extends, which is formed during formation of the crosspiece. 
   In particular, it is proposed that the chain link be formed of the plate having two opposite link mounts. A link pivot extends into each of the link mounts, the link pivots being formed during formation of the crosspiece. 
   The chain link is preferably formed by a crosspiece that is articulated with one of the plates. This plate is connected to the second plate via another crosspiece, in which the plates and the crosspiece form a U-shaped component. 
   According to another advantageous design of the chain link, it is proposed that at least one crosspiece be formed according to the two-component injection molding method, with simultaneous formation of the link connection between one of the plates and one of the crosspieces. 
   According to another embodiment of a chain link in accordance with the present invention, it is proposed that the plates and at least one crosspiece be formed at least partially from different plastics. In particular, it is proposed that the plates and optionally one crosspiece be formed from a plastic chosen from the group of polyamides. 
   According to another embodiment of a chain link in accordance with the present invention, the plates and optionally one crosspiece are formed from a plastic chosen from the group of polyacetals. 
   Additional details and advantages of the method and the chain link according to the invention are explained with reference to the practical examples depicted in the drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the drawings: 
       FIG. 1  is a schematic front view of a first example of a chain link in accordance with the present invention; 
       FIG. 2  is a cross-sectional view taken along line  2 - 2  of  FIG. 1 ; 
       FIG. 3  is a perspective view of a U-shaped chain link part in accordance with the present invention; 
       FIG. 4  is a in cross-sectional view of an example of a chain link taken along line  4 - 4  according to  FIG. 5 ; 
       FIG. 5  is a front view of a chain link in accordance with the present invention; 
       FIG. 6  is a perspective view of a partially constructed U-shaped chain link part of the chain link according to  FIG. 5 ; 
       FIG. 7  is a perspective view of a chain link according to  FIGS. 5 and 6  and having a crosspiece  35  added; 
       FIG. 8  is a perspective view of the present invention from the reverse side of  FIG. 7 ; 
       FIG. 9  is a perspective view from the bottom of the chain link according to  FIG. 8 ; 
       FIG. 10  is a side view of another plate of a chain link in accordance with the present invention; 
       FIG. 11  is a cross-sectional view taken along line  11 - 11  of  FIG. 10 ; and 
       FIG. 12  is a partial cross-sectional view of the plate in  FIG. 10 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 to 3  illustrate one embodiment of a chain link according to the present invention. 
   The link is provided for a power transfer chain that can include a number of such chain links. The chain link has two spaced plates  10 ,  11 . In the depicted example, the plates  10 ,  11  are joined by a lower rigid crosspiece  18 . Each plate  10 ,  11  has a hole  12  on one end region ( FIG. 3 ). A pivot  13  is provided in the opposite end region of the plates  10 ,  11 . For reference in the claims, plate  11  is the “first plate” and the plate  10  is the “second plate.” The holes  12  or pivots  13  of the chain plates  10 ,  11  are shaped and sized so that a pivot  13  can be inserted into the hole  12  of a link plate of an adjacent chain link, and several link plates can be joined together to form a strand. This design of a power transfer chain in known per se. 
   On an upper edge  17  of the plate  10  and across the longitudinal extent of the plate  10 , a recess  14  is provided. A link axis  16  is formed within the recess  14  of plate  10 . The link axis  16  has a circular cross-section, as is apparent from  FIG. 2 . 
   A crosspiece  15  is articulated with plate  1 .  FIG. 2  shows that a section of the crosspiece  15  surrounds the link axis  16  seamlessly. 
   The crosspiece  15  has a hook  19  on its free end. The hook  19  has a hook nose  23 , as well as a pin mount  24 . For reference in the claims, the first crosspiece is the lower or fixed crosspiece, the second crosspiece is the upper or articulated crosspiece. 
   An upper longitudinal edge  17  of the plate  11  and across the longitudinal extent of plate  11 , a hook mount  20  is provided. The hook mount  20 , as is particularly apparent from  FIG. 3 , has a pin  21  running in the longitudinal direction of the plate  11 . A protrusion  22  is provided in the outer wall of plate  11  ( FIG. 2 ). 
   The crosspiece  15  is pivotable around the link axis  16 . In the closed state of the chain link, the pin  21  engages in the pin mount  24  of the hook  19 . Beneath the pin  21 , the protrusion  22  cooperates with the hook nose  23 , so that the crosspiece  15  can be joined releasably to the plate  11 . The pin  21 , which engages in the closed state in pin mount  24 , prevents inadvertent opening of the crosspiece  16 , when plates  10 ,  11  are moved relative to each other. 
   The chain link depicted in  FIGS. 1 ,  2 , and  3  can be produced as follows: 
   The plates of the chain link are initially formed with plate  10  having a link axis  16 . The crosspiece  15  is then formed during simultaneous formation of a link connection between the plate  10  and the crosspiece  15 . 
   The chain link depicted in  FIGS. 1 to 3  has a U-shaped chain link part formed from plates  10 ,  11  and crosspiece  18 , but this is not absolutely necessary. The crosspiece  18  can also be releasably joined to plates  10 ,  11 . 
   There is also the possibility of providing two crosspieces articulated with the plates  10 ,  11  on one of the two plates. These crosspieces can be connected to the opposite plate. There is also the possibility of forming the plate  11  with a crosspiece  15  that is articulated with plate  11 . 
     FIGS. 4 to 7  show another practical example of the chain link according to the invention. 
   The chain link depicted in  FIGS. 4 to 7  has a U-shaped chain link part. The chain link has two spaced plates  30 ,  31 . The plates  30 ,  31  are joined by a lower crosspiece  38 . 
   Each plate  30 ,  31  has a hole  32  in an end region of the plate. A pivot  33  is formed in the opposite end region. The hole  32  and pivot  33  of a chain link form can be joined to mating holes and pivots on adjacent links to form a power transfer chain. 
   The chain link in this embodiment has an upper crosspiece  35  articulated with plate  30 . For articulation, the plate  30  has link mounts  34 . These link mounts  34  are adjacent to an upper edge  37  as depicted, and are formed on the inside surface of plate  30 . The two link mounts  34  are spaced apart from each other.  FIG. 4  shows that in each link mount  34 , a link pivot  36  extends. The link pivots  36  are formed on crosspiece  35 . The crosspiece  35  is articulated with plate  30  by the link mount  34  and link pivot  36 .  FIGS. 4 ,  5 , and  7  show the chain link in the opened state. For closure of the chain link, the crosspiece  35  is pivoted in the direction of the opposite plate  31 . The pin  41 , formed in a hook mount  40  of the plate  31 , enters the pin mount  44  of the hook  39 , provided on the free end of the crosspiece  35 . During further movement of crosspiece  35  in the direction of plate  31 , the hook nose  43  locks behind the protrusion  42  formed on the plate  31 , so that the crosspiece  35  is locked to plate  31 . 
   Another practical example of the chain link according to the invention is shown in  FIGS. 8 and 9 . The essential design of the chain link depicted in  FIGS. 8 and 9  corresponds to the chain link shown in  FIGS. 4 to 7 . 
   The chain link depicted in  FIGS. 8 and 9  has two spaced plates  50 ,  51 . The plates  50 ,  51  are joined by a crosspiece  56 . Each plate  50 ,  51  has a hole  52  and a pivot  53 . The pivots  53  of the plates of an adjacent chain link enter the holes  52  of plates  50 ,  51 . A number of such chain links form a power transfer chain. 
   The chain link shown in  FIGS. 8 and 9  has a plate  51  that has a recess  54  in the upper longitudinal edge  57  as depicted, and in the longitudinal direction, as well as across the longitudinal direction of the plate. Opposite link mounts are formed in the side walls of the recess  54 . Link pivots extend into the link mounts, through which the crosspiece  55  is connected to pivot with the plate  51 . Formation of the link pivots, which is not shown in  FIGS. 8 and 9 , occurs during formation of the crosspiece  55 . 
     FIG. 10  shows a plate  70  of the chain link, in which the plate  70  has a hole  72  and a pivot  71 . Hole  72  and pivot  71  are formed on the opposite end regions of the plate  70 . A link mount  74  is formed in the edge  73  and in the longitudinal direction of the plate, as is particularly apparent from  FIG. 11 . 
   The link mount  74  has a partially circular cross-section.  FIG. 12  shows that a link pivot  76  is situated in the link mount  74 , which had been formed during production of the crosspiece  75 . The crosspiece  75  is pivotable by an angle of about 90°. A hook  77  is formed on the end of crosspiece  75  opposite link pivot  76 , which can be locked to an opposite link plate. Locking is preferably designed so that it is releasable. To improve rigidity of the crosspiece  75 , it can have a rib.

Technology Classification (CPC): 5