Motor vehicles – Special driving device – Portable track
Reexamination Certificate
2000-03-20
2001-09-11
Hurley, Kevin (Department: 3619)
Motor vehicles
Special driving device
Portable track
C180S411000
Reexamination Certificate
active
06286615
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a heavy vehicle for breaking up ground provided with retracting and steering rear wheels.
It is known that for breaking up ground, specific heavy vehicles are used equipped with wheels or tracks depending on how they are implemented and provided with equipment suited to breaking up the actual ground.
Scarifiers are, for instance, known for this purpose that are heavy vehicles used to break up the bituminous surface covering road courses.
A scarifier fundamentally consists of a frame made of heavy-duty metal bodywork, provided with a ripper drum that is set against the ground to be broken up and is supported by a horizontal shaft around which it is rotated.
The frame, which is shaped to provide a driver's cab where the operator sits, is in turn supported by a pair of front drive wheels or tracks and a pair of rear wheels or tracks, either with drive or free, the latter being located next to the ripper drum. Traction systems, housed in an engine compartment formed out of the frame, set the ripper drum in rotation to break up the ground and the wheels or tracks to move the machine.
The rear wheels or tracks are connected to a sole-plate supported by a hydraulic cylinder that allows a vertical movement to adjust the depth the ripper drum penetrates into the ground while an articulation fixed to the frame and connected to the actual sole-plate allows one or both wheels or tracks to be set in a retracted position inside the frame.
The rear wheels or tracks when extracted from the frame, allow better weight distribution primarily during the machine's use, while the possibility of at least one wheel or one track retracting under the frame, allows the machine to be used for digging right up to the wall of the work area.
What's more the position of one or more of the rear wheels or tracks when retracted into the side of the machine, allows to reduce the machine's overall dimensions and aid road transport when it is moved from one work site to another. Known machines equipped with one or both rear wheels or tracks retractable are extended manually and therefore by operations that are awkward for the operator since, to carry them out he has to get down from the machine and go to one or both of its sides to shift the wheels or tracks.
As an alternative to manual retraction, the depositee of this invention has filed an Italian patent application having protocol number V198U000098 which describes a heavy vehicle for breaking up ground in which the changeover of one or both rear wheels or tracks from extracted to retracted into the frame and vice versa, as well as locking them in their final position, is achieved automatically by controls inside the driver's cab.
One limitation shown by the machine described in the aforementioned patent is that when the rear wheels or tracks are set in their retracted position inside the frame, when turning they scrape the ground with considerable resistance. This problem is particularly accentuated when the machine is fitted with tracks rather than wheels, because in this case the resistance while turning is even higher because of the greater surface area in contact with the ground.
SUMMARY OF THE INVENTION
This invention sets the scope of eliminating this inconvenience by producing a machine for breaking up ground provided with at least one rear steering wheel or track. An additional scope is that these steering wheels or tracks can also retract into the side of the machine.
Said scopes are achieved by producing a machine for breaking up ground that in accordance with the main claim comprising:
a frame supported by at least one pair of front wheels or tracks and by at least one pair of rear wheels or tracks;
at least one driver's cab being part of said frame;
means of breaking up the ground connected to said frame;
traction systems supported by said frame to rotate one or more of said wheels or said tracks;
wherein at least one of said rear wheels or said rear tracks has its horizontal axis belonging to a chassis being a integral part of said frame and having at least one first actuator that works with maneuvering systems accessible from said driver's cab to rotate said rear wheel or track around a vertical axis while turning the machine's front wheels.
According to a preferred form of execution the machine is a scarifier mounted on tracks where the two front tracks are both steering and two rear ones, one being fixed and one retractable and steering.
The means of turning the machine include first actuators that work with the rear wheel or track and second actuators that work with both front wheels or tracks, which consist of hydraulic cylinders supplied by slide valves. In particular the slide valve that operates the steering hydraulic cylinder of the rear track is controlled by solenoid valves, while the slide valve that supplies the hydraulic cylinder for steering the front tracks is controlled directly by the power steering connected to the steering column in the driver's cab. The operation of both hydraulic cylinders is interlinked by means of controls to co-ordinate turning, which include potentiometric position detectors or similar, cooperating mechanically with each hydraulic cylinder and electrically wired to an electronic control unit. This is also electrically wired to the solenoid valves that pilot the slide valves supplying the hydraulic cylinder steering the rear track and a position signal for the rear wheel or track when it is set in its retracted position inside the frame.
An advantage of the scarifier invention is that it is easier to drive above all during turning operations.
Another advantage is that the wear on the tracks is also reduced.
REFERENCES:
patent: 3664448 (1972-05-01), Hudis
patent: 3792745 (1974-02-01), Files
patent: 4029165 (1977-06-01), Miller et al.
patent: 4120507 (1978-10-01), Miller
patent: 4387814 (1983-06-01), Beduhn et al.
Dykema Gossett PLLC
Hurley Kevin
LandOfFree
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