Abstract:
The invention relates to a chain link for a power transmission chain, at least partly embodied from a composition containing at least: a. a recyclable raw material, b. a material for binding said recyclable raw material and c. optional adjuncts and additives. In comparison to conventional chain links, the above chain link can be produced in a more environmentally-friendly and economical manner with a saving of non-recyclable raw materials, such as for example crude oil whilst retaining similar or adequate functional properties in comparison with conventional chain links for power transmission chains.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Not Applicable. 
   INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC/REFERENCE TO A “MICROFICHE APPENDIX” 
   Not Applicable. 
   BACKGROUND OF THE INVENTION 
   The invention pertains to a chain link in a power transmission chain, a method for production of such a chain, as well as a power transmission chain. 
   The prior art knows a number of chain links for power transmission chains having a wide variety of shapes, and produced from a wide variety of materials. For example, chain links made from plastic, metal or a combination of plastic and metal are known. It is also already known to combine different plastics in a chain link. For example, DE 38 06 400 C2 discloses a power transmission chain in which two adjacent chain links are made from different thermoplastics. Wear by friction between two adjacent chain links is supposed to be reduced by this. 
   In all previously known chain links for power transmission chains, however, there is a disposal problem after the lifetime of the chain link is surpassed. Both the plastics and metals are generally resistant to decay and must be processed, for example, the plastics are cleaned, ground and melted. In addition, all previously used plastics are based on processing of hydrocarbons that are generally produced from petroleum. As is known, petroleum is available to only a limited extent so that sustainable management is necessary with this raw material. 
   SUMMARY OF THE INVENTION 
   With this as the point of departure, the task of the invention is to furnish a chain link for a power transmission chain that has functional properties similar to ordinary chain links, but is simple to dispose of and can be produced in an environmentally safe fashion, as well as a method for production of such a chain link. Another task of the invention is to furnish a corresponding power chain. 
   This task is solved according to the invention by a chain link formed of a composition having a recyclable raw material and a building material. The invention is also directed to a method for production of a chain link or parts of a chain link including the steps of binding a recyclable raw material with a binder to form a chain link composition and forming a chain link from the chain link composition. The invention is also directed to a power transmission chain having at least one chain link formed of a composition of recyclable raw material and a binding material. Additional advantageous embodiments and variants of the chain link and methods for forming chain links are included below. 
   A chain link according to the invention is made at least partly from a composition containing at least one recyclable raw material, a material that binds this recyclable raw material, as well as optionally auxiliaries and/or additives. 
   Thus, 50 to 95 weight % of the composition, for example, consists of the recyclable raw material, 5 to 40 weight % of the composition consists of a material that binds this recyclable raw material, and 0 to 10 weight % consists of auxiliaries and additives. However, other compositions with weight percentages deviating significantly from this area are also possible and according to the invention. One such chain link that largely consists of a recyclable raw material has some decided advantages in comparison to ordinary chain links, for example, made of plastic. On the one hand, it is much more cost-effective in production than during the use of a plastic of similar quality, and, on the other hand, has a much better ecological balance than a plastic. In addition, after surpassing the lifetime of the chain link, it is much easier to dispose of it in an environmentally safer fashion. For example, incineration with advantageous use of the heat output of the chain link is possible. Since most of the chain link consists of a biodegradable material, very rapid decay of the chain link can be achieved by an appropriate method, for example, in a composting installation. 
   Precisely in times of disappearing raw materials, especially among fossil fuels, like petroleum, it is extremely important to manufacture products that have the best possible ecological balance in order to sustainably manage the limited raw material reserves. For this reason it is advantageous in mass-produced products, such as chain links for power transmission chains, to make them with the same and/or sufficiently good material properties from recyclable raw materials. 
   According to a preferred variant, the chain link consists of a composition of recyclable raw material and a material that binds this with a weight ratio in the range from 3/2 to 19/1, especially 17/3. The weight ratio of 17/3, in particular, has proven advantageous, since most of the composition here consists of the recyclable raw material, i.e., a good ecological balance is present, in which the small fraction of material that binds the recyclable material is large enough so that all the important material properties for operation of a power transmission chain are achieved. 
   According to another advantageous embodiment, the chain link has at least one, preferably each, of the following of properties:
         a) A tensile strength according to DIN 53455 of at least 20 N/mm 2 , preferably at least 25 N/mm 2  and especially in the range of 30 to 200 N/mm 2 ,   b) an elongation at tear according to DIN 53455 of at least 0.5%, preferably at least 0.8%,   c) a tensile modulus of elasticity according to DIN 53455 of at least 4000 N/mm 2 , preferably at least 5000 N/mm 2 ,   d) a bending strength according to DIN 53432 of at least 40 N/mm 2 , preferably at least 100 N/mm 2  and especially in the range from 100 to 200 N/mm 2 ,   e) an edge fiber elongation according to DIN 53452 of about 2%,   f) a bending modulus of elasticity according to DIN 53452 of at least 3000 N/mm 2 , preferably of at least 3500 N/mm 2 ,   g) an impact strength according to DIN 53453 of at least 4 k J/m 2 , preferably at least 6 kJ/m 2 ,   h) a notched impact strength according to DIN 53453 of at least 2.5 kJ/m 2 ,   i) an indentation hardness according to DIN 53456 of at least 50 N/mm 2 , preferably at least 150 N/mm 2 , especially in the range from 180 to 250 N/mm 2 ,   j) a density according to DIN 53479 of at least 1.2 g/cm 3 , especially at least 1.35 g/cm 3 ,   k) an impact tensile strength according to DIN 53448 of about 15 kJ/mm 2 .       

   Each of the aforementioned properties represents a variant according to the invention. Each possible combination of one or more of the properties marked with the letters a) to k) also represents a preferred embodiment of the invention. When different properties are combined, combinations of two to eleven properties are possible and according to the invention.
         In another advantageous embodiment, the chain link is produced from a composition in which the recyclable raw material is a polysaccharide, preferably cellulose. In this context other particularly preferred recyclable raw materials are a material from the group wood, flax, hemp, straw, wool, sisal, cotton, linen, hay, rice husks, bamboo, papyrus, reed, cork, or similar materials or mixtures of at least two of them. All of these are recyclable raw materials that are often also present as waste products in production processes for other products. Thus far, disposal of these waste products has been costly or even environmentally damaging. Each of these fiber-containing or fibrous materials can be used to produce chain links. Thus, it is possible to use wastes from the wood industry or also the clothing industry, from the food industry or other industries expediently and ecologically acceptably. Because of this, the ecological balance of the employed materials is further improved and sustainable management of the raw materials is possible. The available limited resources of hydrocarbons are also spared by this.       

   According to another advantageous embodiment of the chain link, the binding material is a polymer, preferably an elastomer. Thermoplastic elastomers can be used here and polymers from the group of amide, ester, olefin, styrene or urethane elastomers are worthwhile. It is also possible to use mixtures of several polymers from one or more of these groups. 
   According to another preferred variant of the chain link, the binding material is a polyhydrocarbon, preferably a polyolefin, preferably polyethylene or polypropylene, especially polypropylene. Polypropylene offers the advantage that it is very easy to process, on the one hand, and readily degradable, on the other. 
   According to still another advantageous embodiment of the chain link, the composition has at least one auxiliary or additive so that the flash point of the chain link is above 150° C., preferably above 200° C. and especially above 250° C. This permits the use of a chain link according to the invention both under severe stress that accompanies relatively significant heating of the chain link, for example, in spaces with explosion hazard. 
   According to still another advantageous embodiment of the chain link, the composition contains at least one auxiliary or additive so that the ignition point of the chain link lies above 250° C., preferably above 350° C., and especially about 400° C. This is also advantageous during operation of a power transmission chain with such chain links under particularly stressful use conditions or also in spaces with explosion hazard. 
   The added auxiliaries or additives can be used not only to change the ignition and/or flash point, but additives and auxiliaries that produce an improvement in frictional wear can be used. Carbon black, for example, would be worthwhile here. In addition, dyes can be added in order to alter the optical appearance of the power transmission chain and adapt it to certain conditions. In addition, antioxidants can be added, which increase the lifetime of the chain links. Another improvement in lifetime can be achieved, for example, by adding stabilizers. Lubricants can also be added, which shorten the cycle times in the production of these chain links, or also produce better and smoother rolling behavior of the chain links when they form a power transmission chain. Fillers that advantageously influence density and bearing capacity of the chain links are also possible. A variety of additional auxiliaries and additives is also possible and according to the invention. 
   According to another advantageous embodiment of the chain link, it can be coated with at least one material. This coating can be applied according to the invention only to parts or individual partial regions of the chain link. Because of this, the parts that are particularly stressed during rolling of the chain links on each other or on the sliding surfaces of a corresponding guide channel for power transmission chains are improved with reference to their wear behavior. It is also possible to coat the top of the chain links of the lower strand of a power transmission chain with a relatively hard material, while the chain links of the upper strand of a power transmission chain rolling on it can be coated with a relatively soft material, or vice versa. This has the result that the abrasion behavior, on the one hand, and therefore wear of the chain is reduced, but at the same time noise development during rolling of the chain can be substantially reduced. 
   According to still another advantageous variant of the chain link, at least one part of the chain link is made from a material differing from the composition of a recyclable raw material, a material that binds this recyclable raw material, and optionally auxiliaries and additives. Formation of at least part of the chain link from metal is particularly advantageous here. This permits the use of reinforcement structures made of metal that positively influence the stability and lifetime of the chain link, or also formation of particularly stressed parts of the chain link from metal or a harder plastic. 
   According to another inventive idea, a method for production of at least a part of a chain link of a power transmission chain is proposed in which the at least one part made from a material containing a recyclable raw material and a material that binds it and optionally auxiliaries or additives is injection molded or extruded. 
   This type of method offers the advantage that a chain link produced by this method exhibits improved ecological balance in comparison with ordinary chain links. In addition, this method is advantageous from the standpoint of sustainable management, in which the ultimate resources of non-recyclable raw materials, for example, petroleum, are spared. The use of additives or auxiliaries is also advantageously possible. Significant properties of parts of a chain link can be altered with them. 
   Standard dies can be used for injection molding or extrusion, but it is also possible to use special dies, as proposed, for example, in DE 199 34 871 A1. 
   The recyclable raw material, for example, is a polysaccharide, preferably cellulose. Such cellulose is obtained, for example, from wood, flax, hemp, straw, wool, sisal, cotton, linen, hay, rice husks, bamboo, papyrus, reed, cork, or similar materials, as well as from mixtures of at least two of these materials. All these materials are frequently present as waste products from production processes for other products. For example, wood wastes occur in the furniture industry, and linen, wool or cotton wastes in the clothing industry. It is therefore advantageously possible to employ these wastes in an environmentally safe and acceptable fashion. 
   Ecologically acceptable use of products whose lifetime has elapsed can also be accomplished, using products from such compositions. For example, the raw materials present in furniture items can be acceptably used in this way. Use of old clothing, carpets, etc., for production of parts of chain links of power transmission chains is also possible. The fibers so recovered are processed with a material that binds the recyclable material. Polymers, preferably elastomers can be used here. The use of a polyhydrocarbon, preferably a polyolefin, preferably polyethylene or polypropylene, especially polypropylene, is also possible. Polypropylene offers the advantage that it is easy to process and is degradable. 
   In addition, to produce chain links from a composition consisting of a recyclable raw material and a material that binds it, as well as optionally auxiliaries and additives, the same dies, for example for injection molding or extrusion, can be used that are also used for normal plastics. Consequently, it is not necessary to incur costs for creation of new dies or refitting of existing dies. 
   It is also advantageous that not only chain links can be produced from at least one recyclable raw material and a material that binds it in the same machine, but, as required, chain links can also be produced from normal plastics, for example, polyamide. 
   During admixing of at least one corresponding additive or auxiliary, it is possible to produce chain links or parts of chain links whose flash point lies about 150° C., preferably above 200° C. and especially above 250° C. This permits the use of such chain links even under special circumstances, for example, in spaces with explosion hazard. 
   By supplying at least one auxiliary or additive, it is also possible to alter the composition so that the ignition point of the chain link or part of a chain link lies above 250° C., preferably above 350° C., especially above 400° C. This is a requirement for use of such chain links, for example, in spaces with explosion hazard. 
   Individual or several properties of the chain link being produced can also be altered by producing the chain links with the use of auxiliaries or additives. For example, the abrasion behavior can be improved, for example, by adding carbon black. The color, density and sliding properties of the chain link can likewise be improved by adding dyes, fillers and lubricants. In addition, the lifetime of the chain link can be positively influenced by adding antioxidants or stabilizers. 
   It is also possible to coat the chain link with at least one material during the process for production of a chain link or part of a chain link. By coating, the chain links can also be used under circumstances in which they are exposed to aggressive media. Such coating is also sometimes possible so that particularly loaded region of the chain link are coated, or the entire chain link can be coated. Improvements in wear are advantageously produced in the chain link on this account, or a reduction of noise development during rolling of the chain. It is also possible for cost reasons to coat only the parts of the chain link that are affected by wear. 
   According to an advantageous embodiment of the method, a processing temperature lies in the range of 130 to 250° C., especially in the range from 160 to 195° C. According to still another advantageous embodiment of the method, a final pressure of at least 200 bar for at least 1 sec, preferably at least 300 bar for at least 1 sec, especially at least 350 bar for at least 1.5 sec can optionally be used. 
   According to still another advantageous embodiment of the method, at least one part of the chain link is formed from a material different from the composition of a recyclable raw material, a material that binds this recyclable raw material and optionally auxiliaries and additives. This advantageously permits the design of connectors or separation elements from other materials, for example, metals or ordinary plastics, depending on the area of use of the guide chain. The properties of the chain link being produced can therefore be adapted individually to the use circumstances and the demands on the chain link resulting from them. 
   According to still another advantageous embodiment of the method, at least one part of the chain link is formed from metal. This advantageously permits injection molding of reinforcement units, like metal grates with the composition according to the invention from a recyclable raw material, a material that binds it and optionally auxiliaries and additives that serve to reinforce the chain link and serve for long lifetime. It is also possible to form the parts of a chain link particularly affected by wear from metal, or also the regions on which particularly large forces act during operation of a power transmission change assembled from chain links. 
   A multi-component injection molding method is used for another advantageous embodiment of the method. This permits different parts of a chain link to be injection molded uniformly or in succession from different materials in an injection molding process. For example, it is possible to mold the plates of a chain link from a composition of recyclable raw material, binding material and optionally auxiliaries and additives, and to form at least one crosspiece from the usual plastics, for example, polyamide. It is also possible with a multi-component injection molding method to carry out coating of at least parts of the chain link in one working step. 
   Additional details and advantages of a chain link and method for production of a chain link according to the invention are explained by means of preferred practical examples depicted in the drawings, but the invention is not restricted to these. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  schematically depicts in a front view a first practical example of a chain link, 
       FIG. 2  depicts a section along line A-A of  FIG. 1 , 
       FIG. 3  depicts a U-shaped chain link part, 
       FIG. 4  depicts a core of an additional practical example of a chain link part, 
       FIG. 5  depicts a chain link part according to the invention with a core according to  FIG. 4 , 
       FIG. 6  depicts the chain link part according to the invention in a top view and in a section along center line A in  FIG. 5 , 
       FIG. 7  depicts the chain link part according to  FIG. 1  in a top view and in a section along line B-B in  FIG. 5 , 
       FIG. 8  depicts the chain link part according to  FIG. 4  in a side view from the left and in full section, and 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1 to 3  show a first practical example of a chain link according to the invention.  FIG. 3  schematically depicts a U-shaped chain link part in a perspective view. 
   The chain link is at least partially made from a composition that contains a recyclable raw material and a material that binds it. Auxiliaries and additives can optionally be added that improve certain properties of the chain link. For example, auxiliaries or additives that increase the flash point and/or ignition point of the chain link elements, or improve the wear behavior and reduce noise development during operation of a power transmission chain produced from these chain links can be added. 
   Wood is used in this practical example as recyclable raw material, but the use of flax, hemp, straw, wool, sisal, cotton, linen, hay, rice husks, bamboo, papyrus, reed, cork or similar materials or mixtures of at least two of them is also possible. The wood can be furnished in the form of sawdust, as small pellets or the like during production of the composition. Polypropylene is used in this practical example as the material that binds the wood fibers, but all thermoplastic elastomers can be used, for example, amide, ester, olefin, styrene or urethane polymers. The weight ratio of wood to polypropylene is 17/3 in the present example. 
   The chain link is proposed for a power transmission chain that can consist of a number of such chain links. Power transmission chains are used to guide lines or tubes, for example, for electricity, water, steam, etc. 
   The chain link has two plates  10 ,  11  spaced from each other. The plates  10 ,  11  are joined in the depicted practical example by means of a lower rigid crosspiece  18 . Each plate  10 ,  11  has a hole  12  on an end region. A pin  13  is provided in the opposite end region of the plate. The holes  12  and pins  13  of the chain plates  10 ,  11  are designed so that a pin  13  can be introduced to the hole  12  of a chain plate of an adjacent chain link so that several chain plates can be joined, forming a strand. 
   Starting from edge  17  of plate  10  and across the longitudinal extent of plate  10  a recess  14  is provided. A three-dimensionally designed articulation axis  16  is present with in recess  14 , forming a component of plate  10 . The articulation axis  16  has a circular cross-section, as is apparent from  FIG. 2 . 
   To improve the wear resistance or reduce noise development during operation of a chain formed from chain links, it is also possible according to the invention to coat the edge  17  of plate  10  and the corresponding edge of plate  11 . To achieve this, a lower support surface  25  and an upper support surface  26  can be molded onto the chain link. The upper support surface  26  is molded to a crosspiece  15 , while the lower support surface  25  is molded to the plates  10 ,  11 . It is possible according to the invention to form the support surfaces  25 ,  26  from materials other than the composition of a recyclable raw material, a binding material and optionally auxiliaries and additives. It is also possible according to the invention to coat the entire chain link in order to improve properties like lifetime and resistance to decay. 
   A crosspiece  15  is articulated with plate  10 . For example, this crosspiece  15  can also be formed from a material that does not correspond to the composition of a recyclable raw material and a material that binds it. For example, it is possible to make crosspiece  15  from plastic or also metal. By appropriate choice of materials, the chain link can be adapted to practically any conceivable requirement with reference to lifetime, price, etc.  FIG. 2  shows that a section of crosspiece  15  seamlessly surrounds the articulation axis  16 . 
   The crosspiece  15  has a hook  19  on its free end. Hook  19  has a hook tab  23  and a bolt mount  24 . 
   Starting from the longitudinal edge  17  of 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 bolt  21  running in the longitudinal direction of plate  11 . A protrusion  22  is provided in the outer wall of plate  11 . 
   The crosspiece  15  is pivotable around articulation axis  16 . In the closed state of the chain link, bolt  21  engages in bolt mount  24  of hook  19 . The protrusion  22 , which cooperates with hook tab  23 , is formed beneath bolt  21  so that the crosspiece  15  can be releasably joined to plate  11 . Bolt  21 , which engages in the bolt mount  24  in the closed state, prevents inadvertent opening of the crosspiece  15  when the plates  10 ,  11  are moved relative to each other. 
   The chain link depicted in  FIGS. 1 and 2  can be produced as follows: the plates  10 ,  11  of the chain link are first formed. They can be formed from the aforementioned composition, for example, injection molded. It is also possible to produce only one of the plates  10 ,  111  from the aforementioned composition and to form the other plate, for example, from plastic or at least partly from metal. 
   By using a multi-component injection molding method, it is possible to first mold the lower support surface  25 , optionally also from a different material, that advantageously improves the wear behavior and reduces noise development during operation of a power transmission chain made from such chain links. 
   At least plate  10  has an articulation axis  16 . Then crosspiece  15  is formed during simultaneous formation of an articulated connection between plate  10  and crosspiece  15 . In the material choice from crosspiece  15  it is also possible to use a different material than that for plates  10 ,  11  or also the same material. 
   For example, it is also conceivable to form crosspiece  15  from metal and the plates  10 ,  11  from the aforementioned composition. 
   The lower support surface  25  and the upper support surface  26  in the multi-injection molding process are molded directly from a different material, for example from a plastic like polyamide. It is possible that the lower support surface  25  and the upper support surface  26  are molded from different materials. The wear behavior is improved. When chain links are combined into a power transmission chain, it is possible, during use of chain links with lower support surfaces from corresponding different materials for the upper and lower strand to reduce noise development during running of the power transmission chain. This is advantageously possible if chain links with a comparatively hard upper support surface  26  are used for the lower strand and chain links with a comparatively soft upper support surface  26  are used for the upper strand or vice versa. It is not only possible according to the invention to form the lower support surface  25  and the upper support surface  26  from plastic, but as an alternative and/or in addition, to also form them from metal. 
   The chain link depicted in  FIGS. 1 to 3  has a U-shaped chain link part formed by the plates  10 ,  11  and the crosspiece  18 . This is not absolutely necessary. The crosspiece  18  can also be releasably joined to plates  10 ,  11 . For the material choice in production of crosspiece  18  what was said concerning the material choice of crosspiece  15  applies. 
   There is also the possibility of providing two crosspieces articulated to the plate on one of the two plates. These crosspieces are then connectable to the opposite plate. There is also the possibility of forming plate  10  with a crosspiece  15  that is articulated with plate  11 . 
   In production of the individual parts of the chain link it is possible according to the invention to include additives in the composition that increase the flash point and ignition point or alter the color of the chain link. In addition, other additives or auxiliaries can be used for improved lifetime, for example, stabilizers or antioxidants. 
     FIG. 4  shows a core  101  for another practical example of a chain link. The core  101  consists of a composition of a recyclable raw material and a material binding this, but it can also be formed from metal. The core  101  is essentially plate-like. Core  101  has two articulation holes  102 ,  103  spaced from each other. The articulation hole  102  is enclosed by three arc-like recesses  107 , formed symmetrically to an imaginary circumference  113 . The imaginary circumference  113  is coaxial to articulation hole  102 . The articulation hole  103  is enclosed by three recesses  108  that are designed arc-like. The recesses  108  are symmetric to an imaginary circumference  113  that is coaxial to the articulation hole  103 . Core  101  is formed with mirror symmetry relative to the short center axis  116 . The longitudinal edges  117 ,  118  of core  101  trend essentially perpendicularly to the short center axis  116 . Holes  104  are formed at a spacing from each other on center axis  116 . In the region of longitudinal edges  117 ,  118 , additional holes  105  lying essentially on a line parallel to longitudinal edge  117  or  118  are formed. A hole  104  lies between two holes  105 . 
   A chain link part  109  with a core  101  is depicted in  FIG. 5 .  FIGS. 6 ,  7  and  8  show sectional views of the chain link part  109 . As is particularly apparent from  FIGS. 6 ,  7  and  8 , the core  101  of the chain link part  109  is fully enclosed by a core shell  110 . The core shell  110  consists of a plastic, but can also consist of a recyclable raw material, a material binding it and optionally auxiliaries and additives with a different composition in comparison with the composition of core  101 . It is also possible to form the core  101  from metal and the core shell from a recyclable raw material, a material binding it and optionally auxiliaries and additives in order to increase the strength of the chain link, for example. A corresponding design of the core shell  110  has the advantage that the chain links can be adapted to the corresponding use situation. If the core shell  110  is made of plastic, a chain link is obtained having the essential properties of an ordinary chain link, like abrasion and running noise, which, however, is much more environmentally friendly and can be produced much more cost-effectively in comparison to a pure plastic chain. 
   Core  101  can preferably be a structure, preferably a grid-like structure. There is also the possibility of forming the bolt and/or the bolt mounting element from a wear-resistant material, especially metal. The bolt and/or bolt mounting element is then enclosed by the recyclable raw material, the material binding it and optionally auxiliaries and additives. It is possible according to the invention to form any parts of the chain link from wear-resistant materials, especially metal, in which these parts can be molded on or subsequently applied. 
   The articulation holes  102 ,  103 , as well as the recesses  107 ,  108  of the chain link part  109  are free. Each hole  104 ,  105  is enclosed by a peripheral collar  111 . Each collar  111  limits a headspace  112  in which a screw head can be introduced. Collar  11  of the adjacent holes  105 ,  104 ,  105  is formed by a common extension  119 .