Pitch control system

Details Pitch control system Pitch control system

2000-03-02

2001-08-14

Pezzuto, Robert E. (Department: 3671)

Earth working

Mounting for pushed tool at end of motor vehicle

Transversely mounted blade

C172S826000

Reexamination Certificate

active

06273198

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention is directed to a bulldozer having an electrically operated pitch control system wherein the hydraulic angling cylinders are automatically coupled to tank when the hydraulic pitch cylinder is extended or retracted.
2. Description of the Prior Art
Both wheeled and tracked tractors may be provided with a forwardly mounted bulldozer blade for pushing dirt and other material. Typically the blade is coupled to a blade linkage which in turn is coupled to the frame of the tractor. The blade linkage is pivotally coupled to the tractor. Hydraulic raise and lower cylinders extend between the blade linkage and the supporting frame of the tractor for raising and lowering the blade. The blade itself is coupled to the linkage by a spherical bearing. The bulldozer blade, in turn, can be angled to the right and left relative to the linkage by hydraulic angling cylinders. By angling the blade dirt and other material is deposited on a selected side of the tractor.
The fore and aft pitch of some bulldozer blades can also be adjusted. It is desirable to adjust the pitch of the blade for different operations and conditions. On utility bulldozers, the assignee of the present patent application has provided specialized three hole pinning links to adjust the pitch position or three different pitch links for three different pitch positions, see U.S. Pat. No. 5,507,352. The pitch of the bulldozer blade is adjusted by moving the top portion of the blade forward and backward relative to a lower spherical bearing. In addition, hydraulic cylinders have also been proposed to adjust blade pitch, see U.S. Pat. No. 3,900,073.
SUMMARY
It is an object of the present invention to provide a pitch control system for a bulldozer blade that can be easily operated from the operators station and which releases the hydraulic angling cylinders when pitch is being adjusted.
A bulldozer is provided with a supporting frame and ground engaging means for supporting and propelling the frame. The ground engaging means may either be wheels or tracks. A blade linkage is pivotally coupled to the frame and is provided with two hydraulic raise and lower cylinders for raising and lowering the linkage relative to the frame. A bulldozer blade is mounted to the front of the linkage by a spherical bearing. Two double acting hydraulic cylinders are used to angle the blade to the right and left relative to the linkage. A longitudinally extending double acting hydraulic pitch cylinder is positioned between the linkage and blade for adjusting the pitch of the blade relative to the linkage.
The pitch of the bulldozer blade is controlled by a three position rocker switch located in the operator station of the vehicle. The rocker switch selectively positions a three position pitch control valve. The pitch control valve is a solenoid actuated valve having a second extension solenoid and a third retraction solenoid. The rocker switch and the pitch control valve are normally biased into their second neutral positions. The hydraulic angling system comprises an angling control valve and hydraulic angling cylinders. A two position hydraulic dump valve having a dump position and a check position is hydraulically positioned between the angling control valve and the hydraulic angling cylinders. The dump valve is normally biased into its checked position, but is shifted into its dump position when a first solenoid is energized. Whenever the rocker switch is activated to extend the hydraulic pitch cylinder the second extension solenoid is energized to shift the pitch control valve and the first solenoid of the dump valve is also energized shifting the dump valve into its dump position. Whenever the rocker switch is activated to retract the hydraulic pitch cylinder the third retraction solenoid is energized to shift the pitch control valve and the first solenoid of the dump valve is also energized shifting the dump valve into its dump position. Therefore whenever the hydraulic pitch cylinder is extended or retracted the dump valve is shifted to its dump position so that the angling cylinders do not interfere with the pitch adjustment.


REFERENCES:
patent: 3900073 (1975-08-01), Crum
patent: 4962816 (1990-10-01), Imon et al.
patent: 5069296 (1991-12-01), Horsch
patent: 5507352 (1996-04-01), Frisbee et al.
patent: 5682955 (1997-11-01), Groth et al.
patent: 5901793 (1999-05-01), Frisbee
John Deere Dubuque Works Operator's Manual entitled “450G, 550G, and 650G Torque Converter and Direct Drive Crawler Dozers”, OMT159724 Issue B6, cover and pages 35-1 thru 35-6, printed in the U.S.A., (Jan. 1993).

Affiliated with

Also associated with

Rating

Pitch control system does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Pitch control system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pitch control system will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2468114