Fluid handling – Self-proportioning or correlating systems – Self-proportioning flow systems
Patent
1994-08-10
1995-12-05
Nilson, Robert G.
Fluid handling
Self-proportioning or correlating systems
Self-proportioning flow systems
137117, 239126, 239127, G05D 1103
Patent
active
054720095
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a fluid regulator dividing the fluid flow from a pump into a nozzle part and a surplus part. The fluid regulator is mainly intended for regulating the spray capacity of a agricultural sprayer.
PRIOR ART
An agricultural sprayer comprises a spray ramp having a plurality of nozzles, supplying a composition to the soil to be treated. Such composition can be a fertilizer, herbicide, fungicide, insecticide etc.
The sprayer further comprises a tank for the composition, a pump delivering the composition to the nozzles and regulation valves for controlling the sprayer. The entire assembly is supported by a tractor and the pump is connected to the power outlet of the tractor.
The pump can be of the positive displacement pump type, in which the output is proportional to the speed of the power output and essentially independent of pressure. In this case it is possible to have the ramp nozzles outputting a constant dosage per square meter of soil by allowing the output from the nozzles to become proportional to the power output of the tractor and thus the speed of the tractor.
Such a system is shown in the French Patent Specification No. FR-A-2 334 277. The system comprises a fluid flow divider for dividing the fluid flow from the pump into a first flow to the ramp nozzles and a second flow back to the tank. The flow divider is able to divide the flow very carefully so that a predetermined proportion of the total flow is delivered to the ramp nozzles. However, if some of the ramp nozzles are closed, the flow divider must be readjusted so that the remaining nozzles do not receive an increased amount of the composition.
Another example is shown in German Offenlegungsschrift DE-C1-33 32 189 comprising an adjustable flow control valve and an adjustable return valve. The return valve is combined with a pressure relief valve for avoiding any excessive pressure.
The most common system used on the market today is a pressure regulator comprising an adjustable spring loaded cone throttling against a valve seat for returning a portion of the flow to the tank. In principal, it operates as an adjustable overflow valve and return to the tank the fluid, which does not pass to the spray ramp.
In principle, since the pressure relief valve maintains the output pressure constant to the ramp, the output from each nozzles should be independent of the number of nozzles connected in the ramp, but in practice it is very difficult to manufacture a pressure relief valve which is insensitive to fluid flow. Thus, if some of the nozzles are closed, the output from the remaining nozzles will increase.
A common solution to this problem is to use shut-of valves of the alternating type for each section of the ramp to be controlled. These valves pass the fluid to the respective ramp parts or, alternatively, in return to the tank via suitable throttle valves. With throttle valves properly adjusted, the system operates well. However, the system is complicated with many hoses and valves.
Alternatively, the pump can be of the centrifugal type pump in which the pressure is essentially proportional to the square of the speed of the power output. The output pressure from the pump is throttled by a throttle valve so that the output flow from the ramp nozzles is constant. Also this system is sensitive to partial closure of the ramp nozzles.
There is also a system having a regulator valve, which throttles the pump flow and thus builds up a pressure drop. The pressure drop controls in turn a regulation piston, which controls the return opening. Also this system is unduly complicated and service demanding.
The regulation can also take place with a control computer. However, this is an expensive solution.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a fluid regulator for the above-mentioned agricultural sprayer, which can be used irrespective of what type of pump that is used and still provide an output flow which is essentially proportional to the power output of the tractor.
Anot
REFERENCES:
patent: 2266921 (1941-12-01), Trautman
patent: 2844159 (1958-07-01), Trethewey
patent: 3924650 (1975-12-01), Parquet
patent: 4877057 (1989-10-01), Christensen
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