Infinitely variable differential hydrostatic transmission

A differential hydrostatic transmission, comprising:

• an outer case;
• an input shaft and an output shaft rotatably disposed in said case;
• a first unit having a plurality of first pistons respectively slidably disposed in a plurality of first piston chambers therein, said first unit being fixedly attached to said input shaft so as to rotate therewith;
• a second unit having a plurality of second pistons respectively slidably disposed in a plurality of second piston chambers therein, said second unit being fixedly attached to said input shaft so as to rotate therewith;
• a first swashplate means connected to said first pistons and to said output shaft for converting oscillatory motion of said first pistons to rotational movement of said output shaft and vice versa, said first swashplate means being disposed at an angle with respect to the longitudinal axis of said first pistons;
• a second swashplate means connected to said second pistons for converting rotational movement of said second unit into oscillatory motion of said first pistons and vice versa, said second swashplate being angularly adjustable from a first position to a second position and being rotatably fixed to said outer case;
• means for communicating said second piston chambers with said first piston chambers and vice versa such that fluid pumped from said first piston chambers flows into said second piston chambers and fluid from said second piston chambers flow into said first piston chambers wherein the output speed and output torque of said output shaft is controlled by adjusting the angular position of said second swashplate means between said first position and said second position so as to correspondingly adjust the fluid displacement of said second unit with respect to said first unit;
• means for controlling the angle of said second swashplate means to provide an infinite range of output shaft speeds and torques;
• wherein said second swashplate means comprises:
• an outer swashplate member pivotally secured to said outer case about a first axis so as to be pivotable from said first position to said second position;
• an inner swashplate member connected to each of said second pistons, said inner swashplate member having a pivot attaching means for connecting said second pistons thereto in such a manner as to allow said inner swashplate member to freely pivot in a sinusoidal manner with respect to said second pistons when said second pistons are oscillating;
• antifriction bearing means for allowing said inner swashplate member to rotate with respect to said outer swashplate member;
• wherein said inner swashplate member includes a plurality of spherical cavities disposed therein for respectively receiving an end of said second pistons and wherein said pivot attaching means comprises:
• a plurality of pairs of semispherical segments respectively disposed in said cavities in such a manner that the planar surfaces thereof oppose one another, one of said segments in each of said pairs having a through-hole;
• a plurality of end fittings respectively secured to the end of each of said second pistons, each of said fittings having an axial portion and a flat portion, said axial portion extending through said through-hole of said one segment, said flat portion being disposed between said opposing planar surfaces of said pair of segments;
• and
• antifriction sliding means disposed between said flat surface of each of said end fittings and said planar surface of the other of said segments in each of said pair of segments such that when said inner swashplate member is disposed at an angle with respect to said second pistons, any forces exerted by said inner swashplate member are aligned along the longitudinal axis of said second pistons.

A device for securing a plurality of pistons to a swashplate so as to convert oscillating motion of said pistons to rotary motion of an output shaft, comprising:

• an alignment collar fixedly attached to said output shaft so as to be rotatable therewith;
• an outer swashplate ring to which each of said pistons are attached, said outer swashplate ring having pivot attaching means for connecting said pistons to said outer swashplate ring in such a manner so as to allow said outer swashplate ring to freely pivot in a sinusoidal manner with respect to said pistons when said pistons are oscillating;
• antifriction bearing means for allowing said outer swashplate ring to rotate with respect to said alignment collar;
• wherein said outer swashplate ring includes a plurality of spherical cavities disposed therein for respectively receiving said pistons and wherein said pivot attaching means comprises:
• a plurality of pairs of semispherical segments respectively disposed in said cavities in such a manner that the planar surfaces thereof oppose one another, one of said segments in each of said pairs having a through-hole;
• a plurality of end fittings respectively secured to the end of each of said pistons, each of said fittings having an axial portion and a flat portion, said axial portion extending through said through-hole of said one segment, said flat portion being disposed between said opposing planar surfaces of said pair of segments;
• and
• antifriction sliding means disposed between said flat surface of each of said end fittings and said planar surface of the other of said segments in each of said pair of segments such that when said outer swashplate ring is disposed at an angle with respect to said pistons, any forces exerted by said outer swashplate ring are aligned along the longitudinal axis of said pistons.

An axial piston infinitely variable differential hydrostatic transmission comprising:

• an outer case torsionally coupled to the input power source;
• an input shaft, a plurality of separate transverse core barrel segments interconnected together along the axis of the input shaft to form a unitary cylinder barrel core structure, said input shaft being fixedly attached to said core structure, said core structure including first and second piston chambers, first and second pistons, valve means, flow passages, high and low pressure manifolds, and valve ports for a fixed displacement pump/motor unit and a variable displacement pump/motor unit;
• a first swashplate means maintained at a fixed angle with respect to the output shaft, said swashplate means having positive attachment means for positive attachment of the first pistons, to the first swashplate means of the fixed displacement pump/motor unit, said swashplate means thus providing the means to convert rotary motion of said output shaft with respect to the aforementioned unitary cylinder barrel core structure to axial oscillating motion of said first and second pistons and valving means and vice-versa, said first swashplate means also providing the means to positively maintain the desired position of the valve means of said fixed displacement pump/motor unit;
• a second swashplate means pivotally attached and rotatable fixed to the outer case, and said second swashplate means having positive attachment means for positive attachment of the second pistons to the second swashplate means of the variable displacement pump/motor unit, said second swashplate means thus providing the means to convert rotary motion of the unitary cylinder barrel core structure to axial oscillatory motion of said pistons and vice-versa, said second swashplate means also providing the means to positively maintain the desired position of the valve means of said variable displacement pump/motor unit, said second swashplate means also providing means to transmit to said outer case reaction forces to the torque generated by the variable displacement pump/motor unit;
• and
• a means for controlling the angular position of said second swashplate means such that the displacement of said variable displacement pump/motor unit may be varied to achieve a continuous range of input to output shaft speed ratios from reverse to direct drive.