Earth working – Automatic power control – Land leveller type
Patent
1990-02-26
1991-09-03
Taylor, Dennis L.
Earth working
Automatic power control
Land leveller type
172795, 172 1, 91447, 60494, E02F 385, E01H 600
Patent
active
050444468
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates at first to a device for constant pressure regulation of grader blades for the preparation of roadways. The invention has at first been developed for graders but can also e.g. be used for snow-ploughs and other devices doing road surface work or other surface work.
Consequently, the invention relates to the hydraulic system used to regulate grader blades and excavator blades on graders and other work machines used both for snow removing purposes and for construction work (compare the Swedish patent application 8402517-0).
The terminology used for workblades in relation to work machines are that the term "excavator blade" is used for processing and transport of masses and that the term "grader blade" is used as a definition of the workblade normally arranged under a grader and between its front and rear pair of wheels. The term "workblade" therefore comprises these two types of blades. Hereafter in the description the term "grader blade" is used as a definition of the workblade but naturally other types of workblades are included. Furthermore the term "cutting edge" is used for the outmost edge of a workblade.
BACKGROUND ART
The method of placing a road-grader blade against the roadway has almost been unchanged since road-grader blades for the first time were taken into use many centuries ago. The force used to press the cutting edge against the roadway has always been estimated by the operator without any special means of assistance. Consequently, the applied force differs a lot in magnitude in each specific case and was fully dependent of the actual operator's experience and skill. Consequently, the work carried out has been more dependent of the operator's experience and skill than of the hardness and the geometric profile of the foundation. Road work carried out has therefore varied a lot in quality. When the road-grader blade has been pressed towards the roadway with a force not big enough the result of the work carried out was of bad quality. When the road-grader blade has been pressed towards the roadway with a force too big, damages in the roadway have occured and also resulted in too quick wear of the cutting edge which caused enormous costs in changes.
THE PURPOSE OF THE INVENTION
The purpose with the present invention is to produce a method and a means possible provide constant pressure regulation of a road-grader blade so that the cutting edge is always pressed towards the roadway with optimum force related to each job opportunity independent of the operator's experience and skill. The device makes it possible to maintain a constant contact pressure between the cutting edge and the roadway also at variations in the hardness of the roadway, geometric shape and macrostructure. The device also maintains constant pressure when the road-grader blade is tilted or turned round its vertical axis and also in vertical curves.
Accordingly, the purpose of the invention is for example not to cut off the road surfaces or to damage pavements. Furthermore, the present invention provides a possibility to a larger extent than previous to predict when to exchange the cutting edge of a grader and so that the resources held by the stock of graders can be further optimized. The invention taken into practise by the hydraulic system described as follows, consequently gives constant contact force towards the roadway independent of the shape of the roadway. The contact force in the embodiment described is electrically operated from the drivers cab separately for each cylinder (first and second).
A further purpose with the invention is to solve the problems related to the difficulties that arose in the winter when a grader is going to cut the roadways and the pavements clean from snow and ice. It is then very difficult for the operator to adapt the vertical force of the road-grader blade, in other words the pressure of the road-grader blade towards the roadway so that the roadway and e.g. adjacent pavements are not scraped. Such damage causes great economic losses every
REFERENCES:
patent: 3635020 (1972-01-01), Mahlmann
patent: 3709103 (1973-01-01), Dukhovny et al.
patent: 3872670 (1975-03-01), Dezelan et al.
patent: 4024796 (1977-05-01), Theobald
patent: 4372193 (1983-02-01), Hall
patent: 4852660 (1989-08-01), Leidinger et al.
"Hydraulics. Theory and Applications," Robert Bosch GmbH, Jul. 1984, p. 235.
Hedberg Lars-Ake
Jonasson Karl-Jonas
Tiback Bo
Wallin Alf
Jeffrey L.
Maskin AB Tube
Taylor Dennis L.
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