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A pitch control system for a bulldozer having a bulldozer blade that is mounted to a blade linkage. The bulldozer blade is coupled to the blade linkage by a bearing that permits the right and left angling movement of the bulldozer blade and the forward and rearward pitch of the bulldozer blade relat

A pitch control system for a bulldozer having a bulldozer blade that is mounted to a blade linkage. The bulldozer blade is coupled to the blade linkage by a bearing that permits the right and left angling movement of the bulldozer blade and the forward and rearward pitch of the bulldozer blade relative to the blade linkage. An angling control valve hydraulically positions two hydraulic angling cylinders for angling the blade right and left relative to the blade linkage. A hydraulic dump valve is hydraulically positioned between the angling hydraulic control valve and the hydraulic angling cylinder, the hydraulic dump valve having a dump position and a checked position. A linear actuator in the form of a hydraulic pitch cylinder is operatively positioned between the blade linkage and the blade for selectively adjusting the pitch of the blade relative to the blade linkage. A pitch control valve is used to selectively position the pitch cylinder. The dump valve is shifted to its dump position whenever the pitch cylinder is extended or retracted thereby freeing the angling cylinders.

대표청구항 ▼

[ What is claimed is:] [1.]1. A bulldozer comprising,a supporting frame,ground engaging means for supporting and propelling the supporting frame;a blade linkage pivotally mounted to the supporting frame whereby the blade linkage can be raised and lowered relative to the supporting frame;a bulldozer

[ What is claimed is:] [1.]1. A bulldozer comprising,a supporting frame,ground engaging means for supporting and propelling the supporting frame;a blade linkage pivotally mounted to the supporting frame whereby the blade linkage can be raised and lowered relative to the supporting frame;a bulldozer blade is mounted to the blade linkage by a bearing which permits the bulldozer blade to pitch forwardly and rearwardly, and to be angled to the right and left relative to the blade linkage;a hydraulic angling cylinder operatively positioned between the blade linkage and the bulldozer blade for angling the bulldozer blade right and left;a hydraulic pitch cylinder operatively positioned between the blade linkage and the bulldozer blade for adjusting the pitch of the bulldozer blade relative to the blade linkage;a hydraulic circuit for actuating the hydraulic angling cylinder and the hydraulic pitch cylinder, the hydraulic circuit comprising an angling control valve for directing hydraulic fluid to and from the hydraulic angling cylinder and a pitch control valve for directing hydraulic fluid to and from the hydraulic pitch cylinder, a hydraulic dump valve having a dump position and a checked position is hydraulically positioned between the hydraulic angling cylinder and the angling control valve for releasing hydraulic fluid in the hydraulic angling cylinder when the hydraulic pitch cylinder is extended and retracted.