Travel speed limiting system for forklift trucks

In a powered vehicle using power for vehicle propulsion and for accomplishing non-propulsion work, a vehicle travel speed limiting system comprising:

• means for generating a rate of travel signal representing a travel speed of a vehicle;
• means for amplifying the rate of travel signal;
• means for comparing the amplified rate of travel signal to an overspeed limit value;
• means for generating a speed control signal when the rate of travel signal exceeds the overspeed limit value for a selected time period;
• and
• means for controlling vehicle power to limit vehicle travel speed only after the vehicle travel speed exceeds the overspeed limit value for the selected time period without restricting vehicle power for non-propulsion work before the vehicle travel speed has exceeded the overspeed limit value for the selected period of time.

A forklift truck comprising:

• a forklift load carriage;
• a forklift passenger compartment suspended on at least one wheel;
• means for providing power to move the forklift load carriage and to propel the forklift;
• a speed sensor that monitors a forklift passenger compartment travel speed and generates a rate of travel signal representing the travel speed of the forklift passenger compartment;
• and
• a speed limiter that inputs the rate of travel signal and outputs a speed control signal when the rate of travel signal exceeds an overspeed limit value for a selected time period, wherein the speed limiter controls forklift power to limit the travel speed of the forklift passenger compartment only after the travel speed exceeds the overspeed limit value for the selected time period without restricting power to move the forklift load carriage before the travel speed has exceeded the overspeed limit value for the selected period of time.

A speed limiting system for a vehicle comprising:

• a speed sensor that generates a rate of travel signal proportional to a travel speed of a vehicle;
• and
• a speed limiting controller having
• an overspeed comparator that inputs the rate of travel signal and outputs an overspeed signal when the rate of travel signal exceeds an overspeed limit value,
• a time delay element that inputs the overspeed signal and outputs a speed control signal if the overspeed signal continues to input the time delay element for a selected time period,
• a speed control relay that inputs the speed control signal,
• a warning comparator that inputs the rate of travel signal and outputs a warning signal when the rate of travel signal exceeds a warning limit value,
• a warning indicator that inputs the warning signal,
• a feedback element that inputs the speed control signal and outputs a swamping signal that inputs the overspeed comparator and the warning comparator, and causes the overspeed comparator to output the overspeed signal and the warning comparator to output the warning signal even after the rate of travel signal no longer exceeds the overspeed limit value, and
• a reset switch to manually reset the feedback element.