Coupling assembly and friction shoe therefor

Abstract

A coupling assembly which includes an inflatable annular tube, a plurality of friction shoes removably attached to the tube so that the shoes move radially as the tube is inflated and deflated. The shoes include a friction pad bonded to one side of a backing plate and a driving bar also made of friction material bonded to the other side of the backing plate and joined together in a unitary structure. The driving bars fit into grooves formed in the tube to improve torque transfer between the shoes and the tube.

I claim: 
     
       1. In a friction coupling assembly, the combination of an inflatable fluid extensible annular tube; a plurality of friction shoes; means for removably attaching said shoes to a circumferential surface of said tube so that said shoes move radially with the tube as the tube is inflated and deflated; said tube having a plurality of circumferentially spaced transversely extending grooves; each of said friction shoes comprising a backing plate, a pad made of friction material secured to one side of said backing plate, and a driving bar also made of said friction material extending transversely of said plate, said friction material extending through at least one hole in said backing plate and secured to the side of said backing plate opposite from said pad whereby the driving bar of each friction shoe is positioned in a groove of said tube, said bars and grooves having cross sectional shapes which precisely fit each other, said backing plate, pad and driving bar being integrally joined together into a unitary structure by the friction material forming said pad and bar to improve the torque transfer between the shoes and said tube. 
     
     
       2. A friction coupling assembly as claimed in claim 1 in which said bars in cross section have sides which converge in a direction away from said backing plate, said sides connected by an arcuate portion. 
     
     
       3. A friction coupling assembly as claimed in claim 1 in which the ends of said backing plate extend at an angle to the body of said backing plate to thereby form a transverse angled flange at each end of said plate, to additionally improve the torque transfer between the shoes and said tube. 
     
     
       4. In a friction coupling assembly as claimed in claim 3 in which the friction material of said pad extends beyond the ends of the transverse flanges of said backing plate, to maximize friction pad area and minimize exposure of said tube to heat generated at the friction interface area. 
     
     
       5. A friction coupling assembly as claimed in claim 1 in which the grooves in said tube form intervening lugs, a transfer hole in each lug and means extending through said holes for connecting said shoes to said tube. 
     
     
       6. A friction coupling assembly as claimed in claim 5 in which the ends of each pad and backing plate extend at least in part into alternate grooves of said tube. .Iadd. 
     
     
       7.  A friction shoe for use in a friction coupling which includes an input member, an output member and a fluid inflatable annular tube element having a portion thereof which moves radially to couple and decouple the input and output members, said friction shoe comprising a backing plate having an opening therein, a pad made of friction material secured to one side of said backing plate, a driving bar made of the friction material and disposed on a side of said backing plate opposite from said pad, said friction material extending through said opening in said backing plate and overlying the side of said backing plate opposite from said pad, said pad, driving bar and friction material extending through said opening in said backing plate being formed as one piece to join together said backing plate, pad and driving bar as a unitary structure, said friction shoe having means for use in attaching said friction shoe to the portion of the tube element which moves radially to enable said friction shoe to be attached to the tube element with said driving bar positioned to facilitate torque transfer between said friction shoe and the tube element. .Iaddend. .Iadd.8. A friction shoe as set forth in claim 7 wherein said means for use in attaching said friction shoe to the tube element includes a plurality of openings adapted to be aligned with openings in the portion of the tube element which moves radially to enable fasteners to be inserted in an axial direction into the openings in said friction shoe and the portion of the tube element which moves radially to thereby interconnect said friction shoe and tube element. .Iaddend. .Iadd.9. A friction shoe as set forth in claim 7 wherein said backing plate has an arcuate main section having an outer side surface which is engageable with the annular tube element and an inner side surface which is connected to said pad, said driving bar being disposed in engagement with said outer side surface of said main section of said backing plate and having a longitudinal axis which extends parallel to an axis of curvature of said arcuate main section of said backing plate. .Iaddend. .Iadd.10. A friction shoe as set forth in claim 7 wherein said backing plate has an arcuate main section having an outer side surface which is engageable with the annular tube element and an inner side surface which is connected to said pad, said backing plate having first and second end portions which project transversely from said main section of said backing plate to enable said end portions to engage the transverse grooves disposed in the portion of the tube element which moves radially to further facilitate the transfer of torque between said friction shoe and the tube element when said friction shoe is attached to the tube element. .Iaddend. .Iadd.11. A friction shoe as set forth in claim 10 wherein the friction material of said pad extends beyond opposite ends of said main section of said backing plate and is positionable in the same transverse grooves disposed in the tube element as said end portions of said backing plate. .Iaddend. .Iadd.12. A friction shoe assembly as set forth in claim 7 wherein said backing plate has an arcuate main section which is engageable with the annular tube element, said backing plate having arcuate edge portions, said driving bar extending between said arcuate edge portions of said backing plate and having a longitudinal axis which extends parallel to an axis of curvature of said arcuate main section of said backing plate. .Iaddend. .Iadd.13. A friction shoe as set forth in claim 12 wherein said driving bar projects radially from said arcuate main section of said backing plate for a distance which is greater than the thickness of said pad of friction material. .Iaddend. .Iadd.14. A friction shoe for use in a friction coupling which includes an input member, an output member and a fluid inflatable annular tube element having a portion thereof which moves radially to couple and decouple the input and output members, said friction shoe comprising a backing plate having an opening therein, a pad made of friction material secured to one side of said backing plate, a driving bar made of the friction material and disposed on a side of said backing plate opposite from said pad, said friction material extending through said opening in said backing plate, said friction material which forms said driving bar overlying an area on the side of said backing plate opposite from said pad which is greater than the area of the opening in said backing plate through which said friction material extends, said pad, driving bar and friction material extending through said opening in said backing plate being formed at one piece to join together said backing plate, pad and driving bar as a unitary structure, said friction shoe having means for use in attaching said friction shoe to the portion of the tube element which moves radially with said driving bar positioned to facilitate torque transfer between said friction shoe and the tube element. .Iaddend.