Patent ID: 7713153

Claim:
An IVT machine ( 10 ), comprising: first and second input shafts; first and second drive wheels ( 14 ) which are rotatable at all times in the same direction by the input shafts ( 12 ); an output shaft ( 22 ); a ratio changing device ( 20 ), with ratio changing formations ( 24 ), the ratio changing device mounted coaxially on and rotatable with the output shaft ( 22 ); an endless belt ( 34 ) which passes over the drive wheels ( 14 ), and as an open loop over the ratio changing formations ( 24 ) which support the loop on the ratio changing device ( 20 ); a control means for causing the ratio changing formations ( 24 ) to vary ratios of rotation of the input shafts and the output shaft by increasing and decreasing the belt loop dimension about an axis of the output shaft; a belt guide means ( 26 ), over which belt guide means the belt ( 34 ) is movable, the belt guide means comprising two guide wheels spaced apart to provide a throat ( 30 ) through which throat the belt ( 34 ) enters and leaves the ratio changing device ( 20 ); a drive arrangement ( 32 ) located on and rotatable with the ratio changing device ( 20 ) for the transmission of drive power to the output shaft ( 22 ), the drive arrangement engaged with the belt ( 34 ) at a portion of the circumference of the loop on the device ( 20 ); a belt tensioning arrangement ( 16 ); a frame element ( 28 ) which carries the two guide wheels; and a frame member ( 40 ) which carries the output shaft ( 22 ), the ratio changing device ( 20 ), the input shafts, the belt tensioning arrangement, and the frame element ( 28 ), wherein, the control means is operable to cause movement of the frame element both towards and away from the ratio changing device ( 20 ) in incremental, indexed steps to follow an increase, and a decrease, in the belt loop dimension, as the ratios of rotation of the input shafts to rotation of the output shaft change, the belt tensioning arrangement comprises a tensioning wheel for tensioning the belt ( 34 ) and means ( 52 , 248 , 252 , 256 ) for biasing the tensioning wheel into engagement with the belt ( 34 ) between the two drive wheels, and a first one-way sprag clutch ( 262 ), an outer race of which carries the first drive wheel with an inner race fixed to the first input shaft, a second one-way sprag clutch ( 264 ), with an outer race fixed to the second drive wheel and an inner race fixed to the second input shaft, with the direction of rotation of the two sprag clutches the same and their locking directions being opposite to each other so that while power is transmitted in a first direction from the output shaft, the first sprag clutch ( 262 ) is locked and driving while the outer race of the second sprag clutch ( 264 ) is freewheeling and when power is transmitted to the output shaft in a second direction, opposite to the first direction, the second sprag clutch ( 264 ) is locked and driving while the outer race of the first sprag clutch ( 262 ) is freewheeling.