Abstract:
An oil-free chain that includes excellent lubricating properties, and satisfactorily maintains the lubricating properties even in high temperature atmosphere and dust particle atmosphere so that a stable lubrication effect can be maintained for a long period of time. The chain is a bush chain having a pair of inner plates into which the opposite ends of a bush are fitted, and a pair of outer plates which mount the opposite ends of a pair of pins. The pins are rotatably fit-inserted into the bushes of adjoining outer link plates. The inner and outer plates are connected in alternation to form the roller chain in which a roller is rotatably mounted on the outer surface of each bush. A sliding member formed of a 100% graphite sheet is provided between the bush and the pin and/or between the bush and the roller.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates to an oil-free chain used in a power transmission mechanism, a transfer mechanism and the like, and more specifically relates to an oil-free chain provided with a sliding member between a bush and a pin and/or between a bush and a roller. 
       BACKGROUND OF THE INVENTION 
       [0002]    As an oil-free chain used in a power transmission mechanism, a transfer mechanism and the like, there have been chains in which using an oil-containing sintered bush as a bush fitted to inner plates impregnating lubricating oil is supplied between a bush and a pin, and in which an O-ring is disposed between an inner plate and an outer plate to seal the gap between a bush and a pin whereby the leakage of lubricating oil such as encapsulated grease or the like is prevented and infusion of foreign materials from outside is also prevented. 
         [0003]    Further, as a sliding material excellent in lubricating properties a metallic or resin slide bearing containing a solid lubricant such as graphite, molybdenum disulfide, polytetrafluoroethylene or the like is provided on an inner surface of a roller fitted on a bush so that wear between an outer circumferential surface of the bush and an inner circumferential surface of the roller is reduced (see Japanese Laid-Open Patent Publication No. Hei 11-351338). 
       PROBLEMS TO BE SOLVED BY THE INVENTION 
       [0004]    However, there are problems that in the oil-free chain using the above-mentioned impregnating sintered bush since impregnated lubricating oil is oozed out more than required due to an atmospheric temperature or frictional heat and an amount of retained oil is small, a stable lubrication effect cannot be maintained for a long period of time and that in the oil-free chain in which an O-ring is disposed between an inner plate and an outer plate, since filled lubricating oil is a little, the chain is liable to deteriorate due to friction heat and a stable lubrication effect cannot be also maintained for a long period of time. And there are problems that since these chains use lubricating oil, they cannot be used in such a high temperature atmosphere as at 450 to 600 degrees C. particularly and when this chain is used in an atmosphere of dust particles the lubricating oil is absorbed into the dust particles whereby the service life of an oil-free chain is more shortened. 
         [0005]    Further, since a solid lubricant-containing sliding member has a small amount of a solid lubricant as in an oil-containing sintered bush, the service life of an oil-free chain is short, and particularly there is a problem that a resin sliding member cannot be used at high temperature so that a use temperature is restricted. 
       SUMMARY OF THE INVENTION 
       [0006]    Accordingly, the object of the present invention is to solve the above-mentioned prior art problems or to provide an oil-free chain that includes excellent lubricating properties, and satisfactorily maintains the lubricating properties even in high temperature atmosphere and dust particle atmosphere so that a stable lubrication effect can be maintained for a long period of time. 
         [0007]    The invention solves the above-described problems by that, in a solid lubrication oil-free chain in which a pair of inner plates into which both ends of a bush are fitted and a pair of outer plates into which both ends of a pin rotatably fit-inserted into said bush are fitted are alternately connected in a large number, a sliding member formed of a 100% graphite sheet is provided between said bush and said pin. Here the “graphite” in the present invention means a natural graphite, an artificial graphite or the mixture thereof. 
         [0008]    A feature of the invention solves the above-described problems by providing that said sliding member is pressurized onto an inner surface of said bush or an outer surface of said pin; 
         [0009]    Another feature of the invention solves the above-described problems by providing a concavity, which locks said sliding member, on the inner surface of said bush or the outer surface of said pin. 
         [0010]    Another feature of the invention solves the above-described problems by disposing an O-ring between said outer plate and said bush or said inner plate. 
         [0011]    The invention solves the above-described problems in a chain in which a pair of inner plates into which both ends of a bush are fitted and a pair of outer plates into which both ends of a pin are fit, so that the pins may rotate in said bushes to interconnect the inner and outer links in alternation, and a roller is rotatable on an outer surface of said bush, a sliding member formed of a 100% graphite sheet is provided between said bush and said roller. 
         [0012]    The solid lubrication oil-free chain according to another feature of the invention provides that the graphite sliding member has a density of 1.0 g/cm 3  or more. 
         [0013]    The solid lubrication oil-free chain according to another feature of the invention provides that the graphite sliding member is formed into a cylindrical shape by previously compressing a graphite sheet. 
       EFFECTS OF THE INVENTION 
       [0014]    Since in a solid lubrication oil-free chain, a sliding member is provided between a bush and a pin or between a bush and a roller, sliding wear between the bush and pin or between the bush and roller, which are brought into sliding contact with each other, can be prevented. Further the illustrated embodiments of the invention exhibit peculiar effects. 
         [0015]    Namely, since a sliding member provided between the bush and pin or between the bush and roller is formed of a 100% graphite sheet excellent in lubricating properties, a lubricating action is sufficiently exhibited on the entire sliding surface and the lubrication properties are enhanced so that an oil-free operation for a long period of time can be attained. Further, even in such a high temperature atmosphere as 450 to 650 degrees C. the oil-free chain does not lose the lubricating properties and even in a dust particle atmosphere, it exhibits a lubrication effect without absorbing the dust particles. And since the sliding member is formed of a graphite sheet, the handling of the sliding sheet is easy and it can be easily provided between the bush and pin or between the bush and roller. 
         [0016]    Further, when the sliding member is pressurized onto an inner surface of the bush or an outer surface of the pin, the oil-free chain is densified and is increased in lubrication performance, so that the service life of the oil-free chain can be more improved. Further, since the bush and the pin or roller in the solid lubrication oil-free chain can be produced in the same manner as in prior chains, the chain assembly operation for the present invention can be performed without increasing steps. 
         [0017]    Further, when a concavity, which locks the sliding member, is formed on the inner surface of the bush or the outer surface of the pin, the pulling out of the sliding member can be prevented during the assembly of the chain so that the productivity of the chain can be enhanced. 
         [0018]    Further, when an O-ring is disposed between the outer plate and the bush or inner plate or between the roller and the inner plate, the infusion of foreign materials from outside can be prevented, and even if the sliding member wears, the leakage of wear powder is prevented so that lubrication effects are maintained. Particularly, when an O-ring accommodating concavity such as a recess or the like is provided on an inner surface of an end portion of the bush or roller so that a part of the O-ring protrudes from an end surface of the bush or roller, excessive deformation of the O-ring due to compression of the O-ring between the bush and the outer plate or between the roller and the inner plate is prevented so that the service life of the chain can be improved. Further, when an end portion of the bush protrudes from the inner plate and an O-ring is disposed between the inner plate and the outer plate in such a manner that the O-ring surrounds the outer circumferential surface of this protruded portion, since a part of the O-ring is protruded, the same effect as in the O-ring accommodating concavity can be obtained. 
         [0019]    It has been found that if the sliding member has a density of 1.0 g/cm 3  or more, the lubrication performance is remarkably improved so that the service life of the oil-free chain can be more improved. 
         [0020]    If the sliding member is formed into a cylindrical shape by previously compressing the graphite sheet, the density is enhanced and the lubrication effect is improved. Also, the sliding member can be easily attached to a bush or a roller whereby the assembly efficiency of the chain can be improved. 
       BEST MODE FOR CARRYING OUT THE INVENTION 
       [0021]    In a bush chain in which a number of a pair of inner plates in which both ends of a bush are respectively fitted and a number of a pair of outer plates in which both ends of a pin rotatably fit-inserted into said bush are respectively fitted are alternately connected to each other, and in a roller chain in which a roller is rotatably fit-inserted onto an outer surface of the bush, if the solid lubrication oil-free chain according to the present invention includes excellent lubricating properties and excellently maintains lubrication performance even in a high temperature atmosphere and a dust particle atmosphere a sliding member so that stable lubrication effects can be maintained for a long period of time by providing a sliding member formed of a 100% graphite sheet between the bush and pin or between the bush and roller, any concrete embodiments of the oil-free chain may be used. 
         [0022]    Namely, the chain used in the present invention may be a bush chain or a roller chain and when a roller chain is used, a sliding member or sliding members may be attached between a roller and a bush and/or between a bush and a pin. 
         [0023]    If the sliding member is formed of a graphite sheet of 100% graphite that is a 100% natural graphite, 100% artificial graphite or a 100% mixture thereof and can be provided between a pin and a bush or between a bush and a roller, any shape of the sliding member may be used. However, the sliding member is preferably formed into a cylindrical shape by previously compressing a graphite sheet or by pressurizing a graphite sheet onto inner surfaces of the bush and roller or outer surfaces of the pin and bush. Thus in a case where the sliding member is formed by pressurization, it is preferable to provide a concavity into which the graphite sheet is displaced to be locked, or which exhibits an anchoring effect, on the inner surfaces of the bush and roller or the outer surfaces of the pin and bush, which function as formation surfaces of the sliding member. 
         [0024]    Examples of the present invention will be described with reference to drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]      FIG. 1  is a perspective view of a solid lubrication oil-free chain embodying the present invention, showing parts thereof in an assembly view; 
           [0026]      FIG. 2  is an enlarged cross-sectional view taken on the line A-A of  FIG. 1 ; 
           [0027]      FIG. 2(   a ) is an enlargement of the area encircled in  FIG. 2 ; 
           [0028]      FIG. 3  is an explanatory view of the steps in manufacturing a sliding member in one embodiment of the present invention. 
           [0029]      FIGS. 4 and 4(   a ) are views similar to  FIGS. 2 and 2(   a ) showing a second embodiment of the present invention. 
           [0030]      FIG. 5  is an explanatory view of manufacturing a sliding member in an embodiment of the present invention; 
           [0031]      FIGS. 6(   a ),  6 ( b ) and  6 ( c ) are perspective views, with portions broken away, of different bushes made in accordance with the present invention; and 
           [0032]      FIG. 7  is a wear gradient graph showing the relationship between the density of a graphite sheet and the wear loss. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0033]    In a solid lubrication oil-free chain  100  according to Example 1, as shown in  FIGS. 1 and 2 , a pair of inner plates  112 ,  112  are disposed in spaced parallel relation. Bushes  111  with interior and exterior cylindrical surfaces have their opposite ends fitted into the inner plates  112 , In addition, a large number of pairs of outer plates  114 , 114  alternately connect with a like number of pairs of the inner plates, each pair of outer plates having a pair of pin members  113  connecting the plates and rotatable in the interior surfaces of the bushes  111  which are mounted in the two adjoining inner plates. 
         [0034]    A roller member  116  is rotatable on the exterior cylindrical surfaces of each of the bushes  111 , whereby the bushes  111  may rotate on the exterior of the pin member  113  and in the interior of the roller members  116 . An O-ring  117  surrounds the pin  113 . 
         [0035]    This O-ring  117  is attached to a recess  111   a  formed on an inner surface of an end portion of the bush  111  as shown in an enlarged view of  FIG. 2   a  in such a manner that a part of the O-ring  117  is protruded from an end surface of the bush  111 . And the compression ratio of the O-ring is set to 20 to 30% or less so that a damage of the O-ring due to an excessive deformation is prevented. 
         [0036]    It is noted that as shown in an enlarged view of  FIG. 2   b , an end portion of the bush  111  protrudes from the inner plate  112  so that the O-ring  117   b  may be disposed between the inner plate  112  and the outer plate  114  in such a manner that the O-ring surrounds an outer circumferential surface of the protruded portion  111   b . In this case, a part of the O-ring  117   b  is protruded from an end surface of the bush  111  and a damage of the O-ring can be prevented as in the case where the O-ring  117  is attached to the recess  111   a.    
         [0037]    The relationship between the density of the graphite sheet and the wear elongation of the chain, is shown in  FIG. 7  as a wear gradient graph, a wear loss is rapidly lowered from a graphite sheet density of about 0.7 g/cm 3  and the wear gradient becomes gentle from 1.0 g/cm 3 . Thus the density of the graphite sheet is preferably 1.0 g/cm 3  or more. 
         [0038]      FIG. 7  has the abscissa as the density (g/cm 3 ) of the graphite sheet and the ordinate as the wear gradient. The wear gradient is represented by wear elongation per unit slide number (mm/n, n means a slide number). 
         [0039]    As shown in  FIG. 3 , a sliding member  115  is formed by compressing a low density 100% graphite sheet  115   a  to a high density graphite sheet  115   b , and molding in a cylindrical shape. The density of the compressed graphite sheet is 1.0 g/cm 3  and more. 
         [0040]    The sliding member  115  is attached to the inner surface of the bush  111  or the outer surface of the pin  113  before the assembly of chain or during assembly thereof. When a chain is assembled, it produces a solid lubrication oil-free chain  100  of the present invention in which the sliding member  115  is provided between the bush  111  and the pin  113 , 
         [0041]    In this manner since in the sliding member  115  in Example 1 a 100% graphite sheet excellent in a self lubricating property is used and is compressed to enhance the lubrication performance and the entire sliding surface of the bush or pin comes into contact with the graphite, the sliding wear is remarkably reduced so that a long service life of the chain can be attained. The O-ring disposed between the bush  111  and the outer plate  114  blocks the infusion of different materials between the bush  111  and pin  113  from outside so that the damage of the sliding member by different material can be prevented. And even if the sliding member wears since the scattering of wear powders having lubrication performance is prevented and the wear powders can be held between the bush  111  and pin  113  and near them, the lubrication effects can be maintained. 
         [0042]    It is noted that although Example 1 uses a roller chain, it can also be adapted to a bush chain having no roller. Further, the O-ring is not necessarily required. However, since, particularly in use of the chain at an ordinary temperature or in an intermediate temperature atmosphere where the O-ring does not deteriorate the lubrication effects can be maintained as described above, the O-ring is preferably used. 
         [0043]    Next, Example 2 of the present invention will be described with reference to  FIG. 4 . 
         [0044]    Since Example 2 of the present invention is differentiated from the solid lubrication oil-free chain  100  of Example 1 only in that a sliding member is attached between a roller and a bush and an O-ring is attached between the roller and an inner plate, and other concrete configurations in Example 2 are the same as in Example 1, the elements are identifies with the same members in Example 2 as in the solid lubrication oil-free chain  100  in Example 1, except that they are denoted by reference numerals of a  200  series. The parts of this embodiment which correspond to parts in the first embodiment have a reference numeral consisting of same numeral of the first embodiment plus 100. Overlapping descriptions of the members are omitted. 
         [0045]    In a solid lubrication oil-free chain  200  according to Example 2, as shown in  FIGS. 4 and 4(   a ), a pair of inner plates  212 ,  212  are disposed in spaced parallel relation. Bushes  211  with interior and exterior cylindrical surfaces have their opposite ends fitted into the inner plates  212 , In addition, a large number of pairs of outer plates  214 , 214  alternately connect with a like number of pairs of the inner plates. Each pair of outer plates  214  has a pair of pin members  213  connecting the plates and rotatable in the interior surfaces of the bushes  211  which are mounted in the two adjoining inner plates  212 . A roller  216  is rotatable on an outer surface of the bush  211 , and between the bush  211  and the pin  213  a sliding member  215  is provided. 
         [0046]    Further, between the roller  216  and the inner plate  212  is disposed an O-ring  217  in such a manner that the O-ring surrounds the bush  211 . 
         [0047]    This O-ring  217  is attached to a conical concavity  216   a  formed on an inner surface of an end portion of the roller  216  as shown in an enlarged view of  FIG. 4  in such a manner that a part of the O-ring  217  is protruded from an end surface of the roller  216 . And the compression ratio of the O-ring is set to 20 to 30% or less so that damage to the O-ring due to an excessive deformation is prevented. 
         [0048]    It is noted that although in Example 2 the O-ring  217  is attached to the conical concavity  216   a , after a recess is formed on an inner surface of an end portion of a roller and the conical concavity  216   a  may be mounted in this recess as in the O-ring  117  in Example 1. Alternatively, in the case of the O-ring  117  in Example 1, after forming a recess on an inner surface of an end portion of the bush  111 , the O-ring may be mounted in the concavity. 
         [0049]    The sliding member  215  in Example 2 is formed by compressing a 100% graphite sheet  115   a  in a cylindrical shape as in Example 1. The sliding member  215  is attached to an inner surface of the roller  216  or an outer surface of the bush  211  before the assembly of chain or during assembly thereof to assemble a chain whereby a solid lubrication oil-free chain  200  of the present invention in which the sliding member  215  is provided between the bush  211  and the roller  216  can be obtained. 
         [0050]    Thus, since in the sliding member  215  in Example 2 the sliding wear between the bush  211  and the roller  216  can be remarkably reduced as in Example 1, the service life of the chain can be elongated. Further, the O-ring  217  disposed between the inner plate  212  and the roller  216  blocks the infusion of different materials between the bush  211  and roller  216  from outside as in Example 1 so that the lubrication effects can be maintained. 
         [0051]    It is noted that although in Example 2 the sliding member  215  is provided between the roller  216  and the bush  211 , it may be provided between the bush  211  and a pin  213 . Further, the O-ring is not necessarily required. However, since, particularly in use of the chain at an ordinary temperature or in an intermediate temperature atmosphere where the O-ring does not deteriorate, and the lubrication effects can be maintained as described above, the O-ring is preferable. 
         [0052]    The above-mentioned Examples 1 and 2 use sliding members  115  and  215  each obtained by previously compressing a graphite sheet in a cylindrical shape. However, Example 3 in which a graphite sheet is pressurized onto an inner surface of a bush, that is a sliding member is pressurized onto the inner surface of the bush will be described with reference to  FIGS. 5 and 6 . 
         [0053]    It is noted that since Example 3 is the same as the solid lubrication oil-free chain  100  of the above-mentioned Example 1 except that the sliding member is pressurized onto the inner surface of the bush, a bush  311  on whose inner surface the sliding member is pressurized will be described. 
         [0054]    The sliding member  315  of Example 3 is obtained by pressurizing a 100% graphite sheet onto an inner surface of a bush  311 , as shown in  FIG. 5 . In this case a cylindrical body  315   a  composed of a low density graphite sheet is disposed in the bush  311 . After that, a punch P 1  of a press machine P is press-fitted into the cylindrical body  315   a . Then the punch P 1  has such a clearance that this cylindrical body  315   a  has a required compression thickness. After the press-fitting, the cylindrical body  315   a  is compressed in the radial direction of the bush  311  so that a sliding member  315  is formed on the inner surface of the bush  311 . 
         [0055]    In this case concavities  320  are preferably provided on the inner surface of the bush  311  so that a part of pressurized graphite sheet is imbedded into the cavities and the body  315  is locked to the bush with an anchoring effect. 
         [0056]    This concavities  320  may have any shape if a part of the pressurized sliding member  315  is locked so that anchoring effect of the sliding member  315  can be exhibited. Various shapes of the concavities include a hemispherical concavity  320   a  having a circular opening as shown in  FIG. 6   a ; an axially extending grooved concavity  320   b  are shown in  FIG. 6   b ; concavities may be formed on the inner surface and the end surface of the bush  311  as shown at  320   c  in  FIG. 6   c ; and other configurations may be used. In place of the circular concavity  320   a  in  FIG. 6   a , a polygonal or oval concavity may be used. Further, instead of the open-ended grooved concavities  320   b  in  FIG. 6   b , blind grooves whose both ends are closed may be used, or even circumferential groves may be used. Alternatively, in place of the conical concavity  320   c  in the end of the bush  311  in  FIG. 6   c , a cylindrical recess may be used. 
         [0057]    It is noted that although in Example 2 a solid lubrication oil-free chain in which the sliding member  315  is pressurized onto the inner surface of the bush  311  has been described, the sliding member  115 ,  215  or  315  may be formed on the outer surface of a pin  113 ,  213  or  313  (not shown). Further, in the case where a sliding member  115 ,  215  or  315  is provided between the roller  112 ,  212  or  312  (not shown), and the bush  111 ,  211  or  311 , the sliding member may be formed on the inner surface of the roller and on the outer surface of the bush. 
         [0058]    As described above, since, in the solid lubrication oil-free chain according to the present invention, the sliding member provided between the bush and the pin or between the bush and the roller is formed of a 100% graphite sheet having excellent lubricating properties, the sliding wear between the bush and the pin or between the bush and the roller is remarkably suppressed and a stable lubrication effect is maintained for a long period of time. Particularly, the solid lubrication oil-free chain according to the present invention can excellently maintain the lubricating properties even in a high temperature atmosphere such as at 450 to 600 degrees C. or in a dust particle atmosphere. Thus the effects of the present invention are very great.