Pressure-balanced electric motor wheel drive for a pipeline tractor

Abstract

A self-propelled crawler/tractor apparatus is disclosed for traveling through a tubular pipeline while conducting pipeline wall inspection operations and/or towing gear for cleaning, maintenance and the like. The crawler/tractor apparatus is propelled by a plurality of radially positioned motorized traction wheels. Each motorized traction wheel includes a brushless DC electric motor along with clutch, gearbox and other mechanical drive components integrated into a compact self-contained motorized wheel assembly which is sealed and filled with an electrically non-conductive lubricating/cooling oil. The seal integrity at each wheel assembly is maintained against oil leakage and debris ingress by a pressure-balancing mechanism which matches internal oil pressure to the exterior ambient pressure present in the pipeline. The electric motor drive for each traction wheel is individually controlled via an onboard computer to provide a wide range of torque and wheel speeds.

1 . A self-propelled tractor device capable of traveling within a tubular pipeline, comprising:
 a cylindrical-shaped chassis portion;   a plurality of motorized drive wheels, each motorized drive wheel having a pair of side wall portions and an outer hub portion which together form a wheel housing and each drive wheel further including a brushless dc electric motor configured inside said wheel housing; and   a plurality of wheel support extension arms radially positioned around a central axis of the chassis portion, each wheel support extension arm being pivotally attached to the chassis at one end and having a motorized drive wheel attached at an opposite end, each wheel support extension arm having an associated mechanism attached between a portion of the support arm and the chassis for urging the motorized drive wheel end of the support arm away from the chassis for maintaining the motorized drive wheel in contact with an interior wall portion of said tubular pipeline.   
   
   
       2 . The tractor device of  claim 1  wherein a motor shaft portion of the electric motor serves as an axel of the motorized drive wheel, an armature portion of the electric motor being coupled to said motor shaft and a stator portion of the electric motor being fixedly attached to one or more drive wheel side wall portions, and wherein said motor shaft is supported at either end between the pair of drive wheel side wall portions via a set of motor shaft bearings. 
   
   
       3 . The tractor device of  claim 1  wherein the drive wheel housing is filled with a fluid and at least one side wall portion of the housing incorporates at least one pressure-balancing mechanism comprising a flexible membrane diaphragm. 
   
   
       4 . The tractor device of  claim 3  wherein the fluid is an electrically non-conductive lubricating oil. 
   
   
       5 . The tractor device of  claim 1  wherein said outer hub portion of the drive wheel housing is supported for rotation about said pair of drive wheel side wall portions via a crossed-roller bearing assembly. 
   
   
       6 . The tractor device of  claim 1  wherein said outer hub portion of the drive wheel housing includes an outer tire portion. 
   
   
       7 . The tractor device of  claim 1  wherein said motorized drive wheel includes a one-way Sprague-type clutch mechanism and a harmonic reduction drive gearbox. 
   
   
       8 . The tractor device of  claim 1  having at least six radially positioned drive wheel support extension arms, each drive wheel support extension arm supporting a motorized drive wheel assembly. 
   
   
       9 . The tractor device of  claim 1  wherein the chassis portion comprises a front chassis portion and a rear chassis portion, each chassis portion having at least six radially positioned drive wheel support extension arms supporting a motorized drive wheel assembly, and wherein drive wheel support extension arms attached to said rear chassis portion are angularly displaced with respect to drive wheel support extension arms attached to said front chassis portion. 
   
   
       10 . A self-contained motorized drive wheel for a pipeline tractor device, comprising:
 an oil-filled wheel motor housing containing a brushless dc electric motor and having at least one integral pressure-balancing mechanism, said housing comprising an outer cylindrical hub and tire assembly, a wheel left-side wall portion and a wheel right-side wall portion;   wherein the electric motor and other associated mechanical wheel drive components are maintained in an oil-bath within the oil-filled housing, and wherein pressure differences between the housing interior oil pressure and an exterior ambient pressure are reduced by the pressure-balancing mechanism.   
   
   
       11 . A drive wheel as set forth in  claim 10  wherein the pressure-balancing mechanism comprises a flexible membrane diaphragm fitted into a side wall potion of the wheel housing. 
   
   
       12 . A drive wheel as set forth in  claim 10  wherein the pressure-balancing mechanism comprises a pressure compensator device connected by a network of tubing to each oil-filled drive wheel. 
   
   
       13 . A drive wheel as set forth in  claim 10  wherein said associated mechanical wheel drive components include a one-way free-wheeling clutch mechanism and a harmonic reduction drive gearbox contained within the oil-filled wheel housing.