Present construction machines, such as wheel loaders, may utilize the neutralization of a hydrostatic transmission to assist in braking the machine and increasing the hydraulic power availability to an implement. An "inching valve" in fluid communication with the hydrostatic transmission may be used to bleed off a volume of hydraulic control fluid from the hydrostatic transmission which subsequently slows down the machine. Machine ground speed is thus controlled substantially independent of engine speed allowing for increased hydraulic power availability to the implement.
One such approach utilizes a conventional braking system to neutralize the hydrostatic transmission. An operator depresses a brake pedal a predetermined amount which, in turn, moves a piston within a brake cylinder to a position which allows a signal line to be fluidly connected to a tank. The fluid connection between the signal line and the tank creates a pressure drop in the signal line thus neutralizing the hydrostatic transmission. The neutralization of the hydrostatic transmission takes place by the continuous pressure applied to the brake pedal by the operator. The brake pedal is connected to the "inching valve" in such a manner so that the first several degrees of pedal rotation are limited to the neutralization of the hydrostatic transmission without the application of a plurality of brake pads used for actual braking of the machine. In order to achieve a set ground speed for the machine and power availability to the implement as occurs through the neutralization of the hydrostatic transmission, it may be more convenient for the operator to preselect a set ground speed without the direct application of the brake pedal. The brake pedal may be moved remotely through the first several degrees of rotation to eliminate the necessity for the operator's direct and continuous application of the brake pedal. Additionally, it is beneficial to recognize when the operator is actually using the brake pedal for stopping the machine. Therefore, it is advantageous to actuate a brake light signal only when pressure is directly applied to the brake pedal and not during the remote setting of the ground speed.
The present invention is directed to overcoming the problems as set forth above.
USPTO Backgrounds
USPTO Backgrounds