Earth working – Automatic power control – Draft responsive
Patent
1986-12-11
1989-07-18
Stouffer, Richard T.
Earth working
Automatic power control
Draft responsive
180197, 280408, 2804461, A01B 6311
Patent
active
048484814
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for preventing skidding of the drive wheels of a tractor on pneumatic tires and fitted with at least one hydraulic lifting device on which there is mounted an agricultural working tool buried in the ground, when the force for forward movement of the tractor is excessive. The invention relates to the tractor equipment for carrying out that process.
The search for increased agricultural productivity assumes inter alia that the areas of fields which are cultivated by a farmer are constantly increasing. That requires increases in tractor power in order to permit at the same time an increase in the speed of movement of the tractor and an increase in the operative forces for forward movement of the tractor, corresponding to the increase in the working width of the tools. The tools which put up the greatest resistance to forward movement are those which are intended to work the ground in respect of depth, plough shares, teeth of subsoil ploughs and stubble ploughs in particular. Those tools are arranged to stay at the desired working depth as a reaction to the resistance of the ground to the forward movement thereof. They can be generally denoted as being agricultural working tools which are buried in the ground.
It can be agreed that, all other things being equal, the resistance to forward movement is approximately proportional to the depth to which the tools are buried.
In order to achieve a good level of use of the tools, it is desirable for the force for forward movement of the tractor, which is a counterpart to the resistance to the forward movement of the tool, is controlled in such a way that it approaches the grip resultant of the driving wheels, while of course remaining lower than that level of grip. It will be clear that the degree of grip depends on the nature and the state of the ground, its consistency and its moisture content; it is also necessary to maintain a certain safety margin. It will also be recalled that the amount of grip may be increased by increasing the weight of the tractor, by using removable additional weighting members; however, ballasting of the tractor does not eliminate variations in grip which are due to the ground. Be that as it may, the irregularities in the resistance to forward movement of the tools which operate when buried in the ground are the major causes liable to cause skidding of the driving wheels, by virtue of the fact that they cannot be foreseen.
Conventionally, the tractor driver who finds or has a presentiment that his tool is digging in causes the tool to be raised in order to reduce the resistance to forward movement and to avoid skidding.
Tractors have been fitted with anti-skid devices which comprise, on the member coupling the tool to the tractor, a detector for detecting the traction force of the tool which is operating when buried in the ground. Lifting movement of the lifting device is controlled in dependence on the excess of the traction force with respect to a selected reference value in such a way that the tool is raised to a position in which its resistance to forward movement corresponds to the reference value. When subsequently the intrinsic resistance of the ground to forward movement of the tool is reduced, the tool can return to its normal working position, with the depth to which it is buried being regulated from the outset.
It will be appreciated that, if the work done by the tool is generally to be carried out at the set depth, automatically carrying the above-indicated procedure into effect requires the reference value in respect of the force for forward movement of the tractor to be regulated to a level sufficiently above the mean value of forward movement force in order for the tool to be raised only when the resistance to forward movement of the tool shows an abnormally high increase.
Now, as noted hereinbefore, the reference value is limited by the grip limit of the driving wheels, taking account of a safety margin. Thus, because of the effect of accumulative safety margins, it is necessary for the to
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patent: 3690395 (1972-09-01), Spiller et al.
patent: 4132273 (1979-01-01), Mortonson et al.
patent: 4186811 (1980-02-01), Bidon
patent: 4537260 (1985-08-01), Knepper
patent: 4549610 (1985-10-01), van der Lely
Bidon Jacques
Degraeve Francois
Bidon Jacques
Brown Charles A.
Brown Charles E.
Stouffer Richard T.
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