Orbital transmission with geared overdrive

Abstract

The transmission includes an orbital gear complex in combination with a variable hydraulic pump and motor. The input to the transmission is increased in speed by the orbital gearing such that, when the pump and motor are not operating, the orbiter is stationary, and the orbital gearing produces an overdrive condition. A gear reduction is accomplished by rotating the web with the web-rotating device, providing a high gear reduction. The pump and motor are preferably long-piston hydraulic machines with infinitely variable swash plates. The hydraulic machines preferably have wobblers stabilized by full gimbals and hold-down plates with elongated holes for the long pistons to eliminate possible impacts between the hold-down plates and the head ends of the long pistons when the swash-plates are at or near their maximum angle of inclination.

1 - 18 . (canceled) 
   
   
       19 . A hydraulic machine comprising:
 a housing;   a cylinder block formed within said housing and having a plurality of cylinders positioned circumferentially at a first radial distance about the rotational axis of a drive element;   a plurality of respective pistons reciprocally mounted in said cylinders, each piston comprising a piston body and a spherical head connected to the piston body by a narrowed neck and each respective cylinder having an open head portion beyond which each respective piston head extends at all times;   a split swash plate driven by said drive element and comprising:
 a variably-inclined rotor that rotates and nutates; and 
 a wobbler having a flat face that only nutates; 
 wherein the stroke of each piston varies in accordance with the inclination of said swash plate up to a predetermined maximum; and 
   a gimbal comprising an annular yoke connected to said housing by a first pair of gimbal pins spaced 180° apart and connected to said wobbler by a second pair of gimbal pins also spaced 180° apart, wherein each gimbal pin of said first pair lies 90° apart from each gimbal pin of said second pair.   
   
   
       20 . The hydraulic machine of  claim 19 , further comprising a respective sliding shoe pivotally and directly affixed to each piston head, each respective sliding shoe being maintained in direct sliding contact with said flat face during all relative motions between said piston and said flat face. 
   
   
       21 . The hydraulic machine of  claim 20 , further comprising a hold-down assembly for biasing each sliding shoe toward the flat face. 
   
   
       22 . The hydraulic machine of  claim 21 , wherein each piston body has an elongated axial cylindrical length sufficient to be supported within the respective cylinder to assure minimal lateral displacement of the piston head when the shoe is in relative sliding contact with the flat face at all times during the piston stroke. 
   
   
       23 . The hydraulic machine of  claim 19 , wherein said split swash plate further comprises bearings for supporting said wobbler on said rotor. 
   
   
       24 . The hydraulic machine of  claim 19 , further comprising:
 a respective lubricating channel formed in the cylindrical wall of each cylinder in the cylinder block for retaining pressurized fluid;   all of said respective lubricating channels being interconnected to form a continuous lubricating passageway in the cylinder block;   wherein pressurized fluid is retained in said continuous lubricating passageway by the substantial closure of each respective lubricating channel by the outer surface of the axially cylindrical body of each respective piston during the entire stroke of each piston, the only source of pressurized fluid received by the continuous lubricating passageway being a minimal flow between each respective cylindrical wall and the axial cylindrical body of each respective piston; and   wherein said continuous lubricating passageway is formed entirely within the cylinder block, transects each cylinder, and is centered circumferentially at substantially the same radial distance as the cylinders are centered about the rotational axis of said drive element.   
   
   
       25 . The hydraulic machine of  claim 21 , wherein said hold-down assembly comprises:
 a hold-down element having a plurality of respective openings, the boundary of each said respective opening being located in proximity to the narrowed neck of each respective piston; and   a respective washer fitted about the narrowed neck of each piston between the hold-down plate and the respective sliding shoe, each respective washer having an extension aligned cylindrically for circumferentially contacting each said respective sliding shoe;   wherein said washers are in sliding contact with said hold-down plate for movement relative thereto in response to the changing relative positions of the sliding shoes when the flat face is inclined relative to the rotational axis of said drive element.   
   
   
       26 . The hydraulic machine of  claim 25 , wherein the boundary of each respective opening in the hold-down plate is designed to be in contact with more than one-half of the outer circumference of each respective washer at all times during the relative movements. 
   
   
       27 . The hydraulic machine of  claim 25 , wherein said respective openings in the hold-down plate are elongated, said elongation being relatively larger the further each respective hole is positioned from said first pair of gimbal pins supporting said gimbal. 
   
   
       28 . The hydraulic machine of  claim 25  further comprising a minimal spring bias sufficient to maintain the effective sliding contact between each respective shoe and the flat face in the absence of hydraulic pressure at a valve end of each respective cylinder. 
   
   
       29 . The hydraulic machine of  claim 28 , wherein said minimal spring bias is provided by a plurality of springs, each spring being positioned respectively between the hold-down plate and one of the respective washers. 
   
   
       30 . A hydraulic machine comprising:
 a cylinder block having a plurality of cylinders formed in the cylinder block and positioned circumferentially at a first radial distance about the rotational axis of a drive element;   a plurality of respective pistons reciprocally mounted in the cylinders, each piston comprising a piston body and a spherical head connected to the piston body by a narrowed neck and each respective cylinder having an open head portion beyond which the piston head extends at all times;   a swash-plate having a flat face with an inclination relative to the rotational axis of the drive element, each piston head being maintained in effective sliding contact with the flat face during all relative motions between the pistons and the swash plate, a piston stroke being determined in accordance with the inclination of the swash plate and varying up to a predetermined maximum;   a respective sliding shoe pivotally affixed to each piston head and positioned to contact and slide over the flat face;   a hold-down element biased toward the sliding shoes and having a plurality of respective openings, one of said respective openings being located in proximity to the narrowed neck of each piston; and   a respective washer fitted about each narrowed neck between the hold-down plate and each sliding shoe, each washer comprising an extension aligned for contacting each respective sliding shoe;   wherein the washers are in sliding contact with the hold-down plate for movement relative thereto in response to the changing relative positions of the sliding shoes when the flat face of said rotor is inclined relative to the rotational axis of the drive element; and   wherein at least one of the respective openings has a non-circular shape.   
   
   
       31 . The hydraulic machine of  claim 30 , wherein the non-circular shape is slightly larger than the shape of the motion of the respective narrowed neck at a maximum inclination of the swash plate. 
   
   
       32 . The hydraulic machine of  claim 30 , wherein each extension is aligned cylindrically for circumferentially contacting each respective sliding shoe. 
   
   
       33 . The hydraulic machine of  claim 30 , wherein the boundary of each respective opening in the hold-down plate is designed to be in contact with more than one-half of the outer circumference of each respective washer at all times during the relative movements. 
   
   
       34 . The hydraulic machine of  claim 30  further comprising a coil spring positioned circumferentially about the rotational axis of the drive element at less than the first radial distance for biasing the hold-down plate against the washers. 
   
   
       35 . The hydraulic machine of  claim 30 , wherein the swash plate is contained in a swash plate housing and comprises a variably-inclined rotor that rotates and nutates and a wobbler having a flat face that only nutates, the hydraulic machine further comprising:
 a gimbal comprising an annular yoke connected to said housing by a first pair of gimbal pins spaced 180° apart and connected to said wobbler by a second pair of gimbal pins also spaced 180° apart, wherein each gimbal pin of said first pair lies 90° apart from each gimbal pin of said second pair.