This timeline outlines the progressive simplification and refinement of the Slope Control four wheel drive zero radius turn tractor. The platform is a wheel vehicle so it could be used as a tractor, or mower or robot, or in automotive applications. The patents are use agnostic. It is a wheeled vehicle that can turn about a point within its own dimensions without skidding like a skid steer.
Slope Control LLC has built four prototypes of various sizes to validate the intellectual property outlined below.
US 7,597,160 B2 — Four wheel drive zero radius turn architecture
Two wheels can counter rotate under power when the steered wheels are turned sharply enough.
Steered wheels can turn about their vertical axes enough degrees that is already turned can be made in either direction.
The steered wheels are coordinated with Ackerman geometry, and the wheel speed of all four wheels, and their directions of rotation are controlled by controller.
First prototype which is a small electric model.
First tractor is a 100 horsepower machine that is compatible with high flow skid steer attachments, and can lift as much as a full size skid steer or compact track loader but is more stable than either, even at full turn.
US 8,292,769 B2 — Multiple ratio hybrid transmission
Infinitely variable speed transmission with stepless changes between fixed ratios including reverse.
Best of hydrostatic and gear transmissions but with the ability to do regeneration on machines equipped with batteries.
Batteries are not necessary but also allow supplemental torque while one of the fixed ratios is fully engaged.
US 8,662,212 B2 — One Pump + Four Over-Center Motors
Replaced four propel pumps with a single over-center pump and four variable, over-center motors at the wheels.
Motor displacement crossing zero enables counter-rotation and torque bias without flow dividers.
Simpler, lighter, and more efficient than the original design, 7,597,160 while preserving full hydrostatic control.
US 11,260,904 B2— Cross-Link Steering
180 degree rotation of a steered wheel without resorting to the use of a rotary actuator or cams or knuckles.
US 11,702,134 B2 — Steering Axle Drive Assembly
Introduced a control method for true zero-radius turns using alternating forward/reverse pulses and brake-steer sequencing.
This method enables conventional tractors with independent brakes on their large rear wheels, to be converted to zero radius turn machine if the steering axle is replaced, ideally with our steering axle, but hypothetically with caster wheels like on a zero radius turn
mower.
Can be integrated into other transmission and differential combinations but frequent, smooth and modulated reversing, with and geared neutral like a hydrostatic transmission is optimal.
US 12,208,846 B2 — Axle for steering and drive
Axle allows for zero radius turns with reversing, rather than caster type wheels which always roll forward relative to themselves. Caster wheels must turn 180 degrees for the machine to go in reverse, which is not practical for driven wheels or ones which carry much weight, or if the machine drives in reverse frequently.
Simplifies steering hardware while retaining zero radius turn four wheel drive, turning geometry.