Earth working – Towed scraper with ground support wheels
Reexamination Certificate
1998-10-16
2001-03-27
Pezzuto, Robert E. (Department: 3671)
Earth working
Towed scraper with ground support wheels
Reexamination Certificate
active
06206106
ABSTRACT:
TECHNICAL FIELD
This invention relates to a grader of a type used to grade surfaces such as gravel or unmade roads.
It is well known to have specialist graders which have a single large blade which is supported between front and rear wheels to effect grading of roads.
Such a device is implicitly large and therefore expensive and is necessarily so in order to provide sufficient force to support the blade when cutting or shifting substantially embedded rocks or substantial quantities of earth during a grading process. Further, in order not to unduly damage the blade or the support equipment the grading speed is usually kept to a very slow speed (perhaps 3 or 4 kph.)
In accord with this invention it has been discovered that there can be a different approach to grading which allows for the grader to be made of somewhat lighter construction and to also be able to be pulled by a more conventional road vehicle without unnecessarily stressing such vehicles in the event that the grader should strike very heavy loads or even obstacles.
An object of this invention then is to provide a grader which allows for a construction that is somewhat lighter than conventional graders and which will also allow for conventional road vehicles in many instances to effect pulling of the grader and that will facilitate faster grading speeds than have hitherto been considered possible.
BRIEF SUMMARY OF THE INVENTION
According to one form of this invention there is provided a grader having at least two grader blades, each blade being positioned to effect grading of a part only of a being graded surface, each blade being supported by a respective leg for each blade each of which is joined to a support frame by a pivot connection, the position of the blade being maintained in a forward most position by an hydraulic ram the pressure of which is governed by hydraulic pressure of fluid within the ram which fluid is hydraulically connected for each of the rams to an accumulator so that the hydraulic pressure in the ram is substantially the pressure within the accumulator.
With this arrangement, when an obstacle or heavy load is encountered, then because the pressure in the hydraulic ram is implicitly averaged with the pressure of the accumulator, then the increasing pressure on the blade will be met by an increasing pressure by the blade as it swings rearwardly but not a pressure that increases directly proportionally with the length of travel of the ram. This means that the pressure that might be set at 1200 psi with the blade at a forward most position might rise only a further 20 psi with some 3-4 inches rearward movement of the blade. As a result then, the extra strain on the blade and the supporting leg and draft frame will not be excessive and furthermore in further preferred arrangements the movement of the blade can be arranged to be a clearing motion so as to reduce an abutting shape of the blade.
In preference, each hydraulic ram is coupled to the same accumulator.
In preference, the legs are each supported by a draft frame the height of which is changeable by change of pressure within an hydraulic ram extending between parts of the frame, and where the fluid in the hydraulic ram is coupled to the said hydraulic accumulator.
In preference, each blade is supported so as to be, when in its forward most position, entirely rearward of a vertical plane passing through the axis of the pivot support for the leg supporting that blade, so that rearward pivoting of the leg about its respective pivot will result in only rearward and upward motion of the blade relative to the pivot axis.
In preference there is provided a grader including a hitch point on the draft frame, a ground engaging wheel or wheels supporting and defining at least in part the height of the draft frame with respect to the ground, a plurality of grader blades each independently supported so as to present, in a staggered alignment, a grading face each with a lowermost grading edge, each of the blades being supported so as to assume at least two positions relative to the draft frame, a first of these being a grading position, and a second of these being a release position, the release position being achieved when pressure against the blade is in excess of a selected level, and means to lift or lower the blades collectively in the event the grading pressure against two or more of the blades collectively is above a selected pressure.
In preference, each of the blades is supported by a pivotal connection to the draft frame, and the blade is maintained in position by an hydraulic ram.
In preference, the means to lift or lower the blades collectively in the event the grading pressure against two or more blades is outside a selected range of pressures, includes a hydraulic ram, and a linkage arranged so that in one position of the draft frame hydraulic ram, the draft frame is supported in a higher position relative to the hitch point and the ground engaging wheels as compared to alternate position.
In preference, the pressure in each of the hydraulic rams supporting each of the blades is coupled to a common plenum accumulator.
In preference each hydraulic ram is also coupled to the draft frame hydraulic ram such that when additional pressure against the blades is effected with respect to the said hydraulic rams, then there is additional pressure being forced into the draft frame hydraulic ram.
One of the advantages of the arrangement having the above features is that by having individual blades which are aligned in staggered fashion so that any individual blade engages only part of the surface to be graded, is that in the event that one blade strikes a rock, then the all up weight and therefore inertia available to resist a quick release of that blade from a grading position to a release position, is somewhat smaller than would be the case if there was one big single blade.
Further, while one blade releases, the other blades continue to grade at a lower level therefore at least continuing to provide an effective grading effect even though a single stone has not been shifted.
However, when two or more blades start to encounter rocks very much at the same time or encounter an amount of earth that means large stresses are starting to occur, then there is the effect that this will result in additional pressure from the several hydraulic rams being pushed into a release position which in turn then will raise the pressure in a draft frame hydraulic ram which then in turn will collectively lift all of the blades to a higher position at least until the substantial load is lessened.
In a practical example, it has been found that a grader having these features can be used behind a four wheel drive motor vehicle and can be used as a grader without unduly stressing the hitch and other parts of the motor vehicle even though it is being pulled at a quite substantial speed of perhaps anything from 10 to 15 kph. What this means is that the station owner wishes to, they can hitch such a grader behind their conventional four wheel drive Toyota or Land Cruiser and use the grader when proceeding along otherwise unmade tracks or low priority roads at a relatively high speed at least for grading purposes.
The mechanism describes which-is that there are these individual blades each able to be individually released but if there is a collective pressure which is higher than normal, then there is this automatic lifting all of which occurs without the direct or manual intervention of the person dragging the grader.
REFERENCES:
patent: 3642074 (1972-02-01), Geurts
patent: 4364191 (1982-12-01), Cazes
patent: 5562365 (1996-10-01), Berrange
patent: 5921010 (1999-07-01), Schulte et al.
Pezzuto Robert E.
Quarles & Brady LLP
Savannah Forestry Equipment, LLC
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