Patent ID: 7121355

Claim:
A bulldozer with a blade pitch control system, comprising: a crawler-tractor; a ground-engaging blade coupled to the crawler-tractor and configured to raise and lower with respect to the crawler-tractor; at least one hydraulic lift cylinder configured to position the blade; a blade position sensor configured to provide a signal indicative of a position of the blade; an electronic controller coupled to the blade position sensor and to the at least one lift cylinder to (1) continuously adjust the blade with respect to the crawler-tractor when the crawler-tractor pitches forward, in response to the signal indicative of a position of the blade and (2) continuously adjust the blade with respect to the crawler-tractor when the crawler-tractor pitches backward, in response to the signal indicative of a position of the blade, the controller is configured to continuously adjust the blade in response to a difference between the signal indicative of the target blade position and the signal indicative of the blade, wherein the signal indicative of a position of the blade indicates a rate of changes of an angle of the blade that is perpendicular to a generally horizontal and laterally-extending axis; two horizontally disposed arms pivotally coupled to the left and right sides of the crawler-tractor, said arms supporting the blade; and an operator input device coupled to the controller, the input device including a member manually operable to transmit a signal indicative of a target blade position to the controller, the operator input device is further configured to generate the signal indicative of the target blade position in a first mode of operation and to generate a signal indicative of a desired rate of blade lifting in a second mode of operation, wherein the controller has a feedback control loop configured to continuously adjust the blade to the target blade position.