Patent Publication Number: US-2004058766-A1

Title: Sealed chain link assembly

Description:
CROSS REFERENCES TO RELATED APPLICATIONS  
     [0001] This application claims the priority benefit of U.S. Provisional Patent Application No. 60/412,593 filed on Sep. 20, 2002. 
    
    
     
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH  
       [0002] Not Applicable  
       BACKGROUND OF THE INVENTION  
       [0003] The field of invention is chain assemblies, and in particular sealed chain assemblies having molded chain links suitable for use in liquid environments, such as water and wastewater treatment applications.  
       [0004] Power transmission devices incorporate chains to transfer the rotational motion of a rotating shaft into linear motion which can be retransferred into rotational motion of a sprocket. These power transmission chains typically include outer links that are pivotally connected to center links to form a continuous chain assembly having articulated joints. The outer and center links are joined together by a pin which extends through a bushing and apertures formed in the outer and center links, such as disclosed in U.S. Pat. Nos. 2,389,874 and 5,269,729. The pin and links are freely movable relative to each other about the connection pivot axis to provide the articulated joint.  
       [0005] Dirt and other fine abrasive material often works its way into the articulated joints which contributes significantly to chain wear and premature failure. Especially in liquid environments, such as found in water ands wastewater treatment applications, the dirt and abrasive material work its way into the joint through passageways formed at the interface between the link assembly components, such as outer and center links, to contaminate the bushing.  
       [0006] Seals can be provided, such as disclosed in U.S. Pat. Nos. 2,389,874 and 5,269,729, between the outer and center links which inhibit the infiltration of abrasive materials into the articulated joint and retains lubricants in the bushing. These seals in combination with the outer and center links are difficult to assemble. Moreover, abrasive materials can still work their way into the joint through the aperture formed through the outer links for receiving the pin and/or a portion of the bushing. Even if abrasive material does not work its way into contact with the bushing, abrasive material between the freely rotating pin and the outer link can cause significant wear and premature failure.  
       [0007] In another chain assembly shown in U.S. Pat. No. 3,206,258, pairs of overlapping sidebars are provided which are pivotally joined together by a pin. A bushing is received in openings formed in each pair of the sidebars. The pin extends through the bushing to form an articulated joint that joins the pairs of sidebars together. A seal is provided at each end of the bushing which engages the bushing end and the pin to prevent dirt from passing between the pin and bushing. Unfortunately, the abrasive material can still contaminate moving interfaces between the freely rotating pin and apertures formed in the sidebars and the different pairs of sidebars. The relative movement of these components, in combination with the contaminating abrasive materials, can cause significant wear and premature failure. Accordingly, a need exists for an improved chain assembly.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008] The present invention provides a chain link assembly including a first link pivotally joined to a second link by a pin. The first link has a pair of first sidebars joined by a first barrel. Each first sidebar includes first and second ends joined by an inner surface and an outer surface. The first ends of each sidebar define coaxial first apertures coaxial with the first barrel, and the second ends define coaxial second apertures. A second link has a pair of second sidebars joined by a second barrel. Each second sidebar includes first and second ends joined by an inner surface and an outer surface. The second sidebar first ends define coaxial first apertures coaxial with the second barrel and the second apertures of the first link, and the second ends of the second sidebars define coaxial second apertures. A pin extends through the first apertures and first barrel of the second link and the second apertures of the first link to pivotally join the first link to the second link. In one embodiment, at least one of the links is formed from a single piece. In another embodiment, the pin is rotationally fixed relative to one of the links.  
       [0009] A general objective of the present invention is to provide a sealed chain assembly which is easily assembled. This objective is accomplished by providing a link formed from a single piece including sidebars joined by a barrel.  
       [0010] Another objective of the present invention is to provide a chain assembly having joined links that minimize passageways for contaminants between surfaces which move relative to each other. This objective is accomplished by preventing rotation of the pin connecting two links relative to one of the pins.  
       [0011] The foregoing and other objectives and advantages of the invention will appear from the following description. In the description, reference is made to the accompanying drawings which form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the invention. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0012]FIG. 1 is a perspective view of a partially assembled sealed chain assembly incorporating the present invention;  
     [0013]FIG. 2 is a top view of the chain assembly of FIG. 1;  
     [0014]FIG. 3 is a cross sectional view along line  3 - 3  of FIG. 1; and  
     [0015]FIG. 4 is a side view of an the assembled chain assembly of FIG. 1. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0016] As shown in FIGS.  1 - 4 , a plurality of overlapping chain links  12  are pivotally joined together to form a chain assembly  10 . Each link  12  is pivotally joined to an adjacent link  12  by a pin  16 . The pin  16  is fixed relative to one of the joined links  12  to prevent unnecessary relative movement between the pin  16  and one joined link  12  that can cause premature wear. Sealing members  18  interposed between the adjacent links  12  seal the interfaces between adjacent links  12  to protect the pin  16  from contamination.  
     [0017] Each link  12  includes a pair of spaced apart sidebars  20  joined at a first end  22  by a barrel  24 . Preferably, each link  12  is a single piece molded from a plastic material, such as acetal, polyethylene, polypropylene, nylon, and the like. Opposing second ends  26  of the sidebars  20  are spaced apart a distance sufficient to receive the first ends  22  of the adjacent link  12  therebetween. Advantageously, forming the sidebars  20  and barrel  24  as a single piece eliminates an interface between the barrel  24  and sidebars  20  which can be contaminated by abrasive material. Moreover, relative motion between the barrel  24  and sidebars  20  is also eliminated to prevent unnecessary wear therebetween.  
     [0018] Each sidebar  20  includes a body  28  having the first and second ends  22 ,  26  joined by an inner surface  30  and an outer surface  32 . The inner surface  30  of one sidebar  20  faces the inner surface  30  of the other sidebar  20  of the link  12 . The first ends  22  of each sidebar  20  define first apertures  34  having a common first axis  36 . The barrel  24  joining the sidebars  20  is coaxial with the first apertures  34  for receiving the pin  16 . The second ends  26  of each sidebar of the link  12  define second apertures  38  having a common second axis  40  which is substantially parallel to the first axis  36 .  
     [0019] A pair of walls  42  proximal the edge of the second aperture  38  formed in each sidebar  20  extend axially away from the outer surface  32  of the sidebar  20  relative to the second aperture  38 . Each wall  42  engages the pin  16  joining the adjacent links  12  to prevent rotation of the pin  16  relative to the sidebar  20  from which the engaged walls  42  extend. Ribs  44  are provided to support the walls  42  against deformation caused by forces exerted on the walls  42  by the pin  16 .  
     [0020] The interface between joined links  12  is sealed by a sealing member  18  interposed between the sidebars  20  of adjacent links  12 . The sealing member  18  is received in an annular receptacle  46  formed in the sidebar outer surface  32  of each link sidebar  20 . The receptacle  46  surrounds the first aperture  34  formed through the sidebar  20 , and receives the sealing member  18  to seal the interface between the adjacent link sidebars  20 . Preferably, the annular receptacle  46  is radially spaced from the first aperture  34  to allow elongation of the first aperture  34  without disengaging the sealing member  18  from the adjacent link  12 . Although the receptacle  46  is shown to be formed in the outer surface  32  of one sidebar  20  surrounding the first aperture  34  of the sidebar  20 , the receptacle  46  can be formed in the inner surface  30  of the sidebar  20  surrounding the second aperture  38  without departing from the scope of the invention.  
     [0021] The sealing member  18  engages a substantially flat engagement surface  48  formed on the inner surface  30  of the adjacent link  12  facing the receptacle  46 . The engagement surface  48  surrounds the second aperture  38  of the adjacent link  12  for sealing engagement with the sealing member  18 . Advantageously, providing a substantially flat engagement surface  48  allows misalignment of the second apertures of the one link  12  with the first apertures  34  of the adjoining link  12  while maintaining the engagement of the sealing member  18  with the engagement surface  48 . Of course, if the receptacle  46  is formed in the inner surface  30  of the sidebar  20 , the engagement surface  48  is formed on the sidebar outer surface  32  of the adjacent link  12  facing the receptacle  47 .  
     [0022] The sealing member  18  is received in the receptacle  46  and sandwiched between the sidebars  20  of adjacent links  12  to seal the interface between adjacent links  12 . Preferably, the sealing member  18  is an  0 -ring formed from an elastomeric material, such as a thermoplastic, rubber, and the like. The sealing member  18  can be held in the receptacle  46  using a friction fit, adhesives, and the like. Alternatively, the sidebar  20  can be molded around the sealing member  18 , or the sealing member  18  can be molded into the receptacle  46 , to embed the sealing member  18  in the sidebar  20  and prevent separation of the sealing member  18  from the sidebar  20  to simplify assembly.  
     [0023] The pin  16  extends through the aligned first and second apertures  34 ,  38  of the joined links  12  and the barrel  24  joining the first apertures  34  to pivotally join the adjacent links  12 . The pin  16  is retained in the coaxial second apertures  38  by a friction fit that prevents easy removal of the pin  16  from the barrel  24 . Of course, other methods known in the art for retaining the pin  16  can be used, such as a cotter pin, retaining cap, snap fit, and the like, without departing from the scope of the invention.  
     [0024] The pin  16  includes a head  50  that slips between the walls  42  extending from the sidebar outer surface  32  proximal the second aperture  38 . The head  50  includes substantially flat surfaces  52  that engage the walls  42  to prevent rotation of the pin  16  relative to the link  12  from which the engaged walls  42  extend. Although a pin  16  having a head  50  with flat surfaces  52  engaging the walls  42  is disclosed, any structure known in the art can be provided to prevent rotation of the pin relative to one of the links, such as a tooth extending from one of the pin and the sidebar which extends into a notch formed in the other of the pin and sidebar, without departing from the scope of the invention. Advantageously, fixing the pin  16  relative to the second apertures  38  to prevent relative movement of the pin  16  and second apertures  38  minimizes the infiltration of contaminants through the interface between the pin  16  and second apertures  38 .  
     [0025] The chain assembly  10  is assembled by inserting the sealing member  18  into the receptacle  46 , and then aligning the first apertures  34  and barrel  24  of one chain link  12  with the second apertures  38  of a second chain link  12 . The pin  16  is then inserted through the aligned first and second apertures  34 ,  38  and barrel  24  to pivotally join the links  12  together.  
     [0026] In use, the sealing member  18  inhibits contaminants from working their way through the interface between sidebars  20  of adjacent links  12  and onto the pin  16  extending through the barrel  24 . The nonrotating pin  16  extending through the second apertures  38  sealingly engages the second apertures  38  to inhibit contaminants from working their way through the second aperture  38  and into the barrel  24 . Advantageously, radially spacing the sealing member  18  from the first aperture  34 , allows elongation of the first aperture  34  without breaking the seal formed by the sealing member  18  engaging the engagement surface  48 .  
     [0027] While there have been shown and described what is at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention defined by the appended claims.