Blade-type chain tensioner

Abstract

A blade-type tensioner for chain drives which is suitable for use as a tensioner of the timing chain of a motor vehicle engine. The present invention is a chain tensioner particularly suited for use in confined spaces having a blade spring element mechanically interlocked with a plastic shoe. The shoe may be of rigid filled nylon and engages the chain to be tensioned. The spring element is interlocked to the plastic shoe by having ends inserted into grooves formed in the opposite ends of the shoe. The shoe is rotatably fixed to a base by way of a pin. The groove at the fixed end of the shoe extends towards the tip of the fixed end of the shoe past the pin attachment point. The groove at the free end of the shoe extends toward the tip of the free end of the shoe past the point at which the free end of the shoe bears upon a sliding surface formed on the base.

What is claimed is:  
     
         1 . A blade tensioner comprising: 
 a base having a face;    an arcuately shaped shoe having a first side with a face for sliding engagement with an associated chain, said shoe having a fixed end, said fixed end being fixed to and rotatable around a pin fixed on said base and said shoe having a free end opposite said fixed end, said free end of said shoe being in sliding contact with said face formed on said base;    a blade spring provided along said shoe on an opposite side of said shoe, said blade spring having end portions, said end portions of said blade spring being inserted into grooves formed respectively at said fixed end and said free end of said shoe, said groove of said fixed end of said shoe extending toward a tip of said fixed end beyond said pin, at least one of said grooves of said shoe having a relief channel formed therein effective to reduce contact between said blade spring end and said shoe.    
     
     
         2 . The blade tensioner of  claim 1 , wherein said groove of said fixed end of said shoe extends beyond a line (E) drawn perpendicular to said face of said shoe through the center of said pin.  
     
     
         3 . The blade tensioner of  claim 2 , wherein said blade spring contacts an end of said groove of said fixed end of said shoe at a point toward said tip of said fixed end beyond said pin.  
     
     
         4 . The blade tensioner of  claim 3 , wherein said relief channel extends in a direction transverse to the longitudinal axis of said shoe.  
     
     
         5 . The blade tensioner of  claim 4 , wherein a guide is provided on the slide face of said base adjacent to said free end of said shoe to guide the travel of the free end of said shoe.  
     
     
         6 . The blade tensioner of  claim 5 , wherein said guide is provided with a pair of elements, said elements being located on opposite edges of said slide face, each of said elements of said guide having a convex curved face adjacent said edges of said free end of said shoe.  
     
     
         7 . The blade tensioner of  claim 6 , wherein a concave opening extending in a direction transverse to the longitudinal axis of said shoe is formed on said fixed end and said free end.  
     
     
         8 . The blade tensioner of  claim 7 , wherein said concave opening is filled with fiber-reinforced plastics.  
     
     
         9 . The blade tensioner of  claim 1 , wherein said groove of said free end of said shoe extends toward said tip of said free end beyond a contact point between said free end and said slide face.  
     
     
         10 . The blade tensioner of  claim 9 , wherein said groove of said free end of said shoe extends toward said tip of said free end beyond a line (F) drawn perpendicular to said face of said shoe through said contact point.  
     
     
         11 . The blade tensioner of  claim 10 , wherein said blade spring contacts said groove of said free end of said shoe at a point toward said tip of said free end beyond said contact point between said free end and said slide face.  
     
     
         12 . The blade tensioner of  claim 11 , wherein said fixed end and said free end each have a channel formed therein adjacent said blade spring ends, said channel extending in a direction transverse to the longitudinal axis of said shoe.  
     
     
         13 . The blade tensioner of  claim 12 , wherein a guide is provided on the slide face of said base adjacent to said free end of said shoe to guide the travel of the free end of said shoe.  
     
     
         14 . The blade tensioner of  claim 13 , wherein said guide is provided with a pair of elements, said elements being located on opposite edges of said free end of said shoe, each of said elements having a convex curved face adjacent said edges of said free end of said shoe.  
     
     
         15 . The blade tensioner of  claim 14 , wherein a concave opening extending in a direction transverse to the longitudinal axis of said shoe is formed on said fixed end and said free end.  
     
     
         16 . The blade tensioner of  claim 15 , wherein said concave opening is filled with fiber-reinforced plastics.  
     
     
         17 . A blade tensioner comprising: 
 a base having a face;    an arcuately shaped shoe having a first side with a face for sliding engagement with an associated chain, said shoe having a fixed end, said shoe fixed end being fixed to and rotatable around a pin fixed on said base and said shoe having a free end opposite said shoe fixed end, said shoe free end being in sliding contact with said face formed on said base;    a blade spring provided along said shoe on an opposite side of said shoe, said blade spring having end portions, said blade spring end portions being inserted into at least a first groove formed at said fixed end and a second groove formed at said shoe free end, a portion of said first groove disposed between said pin and a tip of said fixed end, at least one of said grooves having means for reducing contact between said blade spring end and said shoe, said contact reducing means disposed in said groove relative to said blade spring end effective to reduce wear of said groove by said blade spring end.    
     
     
         18 . The blade tensioner of  claim 17 , wherein the contact reducing means are disposed in the first and second grooves.  
     
     
         19 . The blade tensioner of  claim 17 , wherein the contact reducing means are effective to reduce deterioration of the tension applied to said associated chain by said tensioner due to interference between said spring end and said shoe.  
     
     
         20 . A method of providing a blade tensioner, the method comprising: 
 providing a base having a face;    providing an arcuately shaped shoe having a first side with a face for sliding engagement with an associated chain, said shoe having a fixed end, said shoe fixed end being fixed to and rotatable around a pin fixed on said base and said shoe having a free end opposite said fixed end, said shoe free end being in sliding contact with said face formed on said base;    providing a blade spring along said shoe on an opposite side of said shoe, said blade spring having end portions;    inserting said blade spring end portions into a first groove formed at said shoe fixed end and a second groove formed at said shoe free end, said first groove having a portion disposed between said pin and a tip of said fixed end; and    forming a relief channel in at least one of said grooves, said relief channel disposed in said groove relative to said blade spring end effective to reduce contact between said blade spring end and said shoe to reduce wear of said groove by said blade spring end.    
     
     
         21 . A blade tensioner comprising: 
 a base having a face;    an arcuately shaped shoe having a first side with a face for sliding engagement with an associated chain, said shoe having a fixed end, said fixed end being fixed to and rotatable around a pin fixed on said base and said shoe having a free end opposite said fixed end, said free end of said shoe being in sliding contact with said face formed on said base;    a blade spring provided along said shoe on an opposite side of said shoe, said blade spring having end portions, a first of said blade spring end portions being inserted partially into a first groove formed at said shoe fixed end, said first groove having a terminus spaced from the tip of said shoe, a second of said blade spring ends inserted into a second groove formed at said shoe free end, the tip of said first blade spring end spaced from said first groove terminus, said first groove having a portion disposed between the tip of said shoe fixed end and said pin effective to reduce the degree of opening of said first groove during deformation of said shoe to reduce change of a contact point between said first groove and said spring end.    
     
     
         22 . The tensioner of  claim 20 , wherein said portion of said first groove disposed between said tip of said fixed end and said pin is effective to reduce deterioration of the tensioning of said associated chain by said tensioner.