Shielded plot sprayer

Details Shielded plot sprayer Shielded plot sprayer

2002-03-29

2004-03-02

Hwu, Davis (Department: 3752)

Fluid sprinkling, spraying, and diffusing

With mobile tank-type supply means

Vehicle drawn or carried

C239S146000, C239S170000, C239S164000, C239S750000, C239S751000

Reexamination Certificate

active

06698668

ABSTRACT:

FIELD OF THE INVENTION
This invention generally relates to agricultural field spraying equipment, and more particularly to a plot sprayer useful in field research relating to biological effectiveness of agricultural chemicals on crops and weeds.
BACKGROUND OF THE INVENTION
Agricultural chemicals, including pesticides, plant growth regulators, foliar fertilizers, desiccants and the like, are typically applied to plants or soil by spraying using various types and designs of mobile spraying equipment. The agricultural chemicals are normally diluted, dissolved or dispersed in a suitable liquid carrier, most commonly water, to form a composition that is suitable for spraying and is referred to herein as a “spray composition”. The application rate of a sprayed chemical can be metered by controlling four factors: the rate of travel of the spraying equipment over the ground, the rate at which the spray solution is dispensed, the width of the swath being sprayed, and the concentration of the chemical in the spray solution.
Rate of travel of the spraying equipment, expressed, for example, in meters per second (m/s), is dictated by forward speed during spraying, whether motion is imparted by human power, as in the case of hand-held or backpack-mounted spraying equipment, or by mechanical power, as in the case of tractor-mounted spray equipment or purpose-built motorized spray rigs.
Rate of dispensing, or output, of the spray solution, expressed, for example, in liters per second (l/s), is dictated by several factors: the number of simultaneously operating spray nozzles, the configuration, in particular the size of the orifice of each nozzle, the propulsion force applied (normally provided by hydraulic pressure), and the rheological properties of the spray solution, especially its viscosity. The term “nozzle” in the present context is to be understood to apply to any atomization means having the function of a nozzle. Similarly, the term “orifice” in the present context is to be understood to apply to the feature or part of any atomization means having the same function as the orifice of a nozzle.
Spray swath width, expressed, for example, in meters (m), is dictated by the number of nozzles arranged on a boom disposed perpendicularly to the direction of travel of the spray equipment, the distance between nozzles, the angular width of the conical or fan-shaped spray pattern generated by the orifice of each nozzle, the degree of overlap of adjacent spray patterns, and the height of the nozzles above the ground or plant target.
Concentration of the chemical in the spray solution, expressed for example in grams/liter (g/l), is controlled by the operator during preparation of the spray solution, most commonly by mixing a measured amount of a concentrate formulation having a known concentration of the chemical in a measured volume of water.
Chemical application rate is the product of the above parameters and can be expressed as
R=OC/TW
where R is chemical application rate, O is spray solution output, C is concentration of chemical in the spray solution, T is speed of forward travel and W is swath width. When T is expressed in m/s, W in m, O in 1/s and C in g/l, R is given in grams per square meter (g/m
2
).
Modern spray equipment can generally be fairly precisely calibrated with respect to the above parameters to deliver a desired chemical application rate. Under ideal weather conditions, such calibration leads to an actual application rate which is more or less constant and reproducible and which varies little (typically +/−10% or less) from the desired rate.
However, weather conditions are seldom ideal. In particular, wind, even a light wind, disturbs the spray pattern sufficiently to compromise accuracy and precision of a well calibrated sprayer. When wind speed and direction vary constantly, a condition known as turbulence, this problem is still more acute. Turbulent air movement frequently occurs near ground level even when air movement a few meters above ground is non-turbulent. This turbulence is often further aggravated by motion of the spray equipment.
An additional source of variation in application rate, even when a sprayer is perfectly calibrated, is vertical movement or oscillation of the spray boom or nozzle caused by travel over an irregular ground surface by a wheeled vehicle carrying the spraying equipment. Such vertical movement can be a problem also with hand-held spray equipment even when operated by an experienced technician walking on level ground. As the spray boom or nozzle is raised or lowered, spray swath width and the degree of overlap of adjacent spray patterns vary, resulting in irregularities in deposition of the spray composition.
Yet another problem is disturbance of soil or plants immediately before, during or immediately after spraying by the moving wheels of a vehicle or the walking feet of an operator carrying the spraying equipment. Such disturbance can take the form, for example, of local compaction of the surface layers of soil, leading to variation in the effectiveness of soil-applied chemicals. Disturbance of plants can affect their biological response to an applied chemical as well as result in accidental transfer of an applied chemical to other plants.
A particularly high degree of accuracy, precision and reproducibility is required when the chemical application is for research purposes. Agricultural researchers must be able to precisely evaluate the effects of particular rates of a chemical on crop and/or weed plants occupying a particular area of a field demarcated for such evaluation. Such a demarcated area is referred to herein as a plot. Typically, researchers compare the performance of plants in a sprayed plot to that in a nearby or adjacent unsprayed control plot. Generally, several different chemical treatments are compared, each treatment being applied to a different plot. It is important, therefore, that the chemical is precisely dispensed only on the intended plot, and uniformly within that plot, with little or no wind-assisted drift of the spray solution on to adjacent plots.
The occurrence of wind is, in most climates, very frequent. If spraying has to be restricted to periods of relative calm, the number of plots that can be sprayed in a season is limited. Research productivity suffers as spray operators are often unable to apply chemicals at the optimum time, because of windy weather. Thus, a need exists in the art for a spraying apparatus which is able to accurately dispense a chemical within a plot with minimum effects from wind and turbulence. Such an apparatus would greatly improve research productivity as well as accuracy.
As spraying can seldom wait until conditions are absolutely calm, researchers have to some extent adapted their procedures to allow for at least a light wind. For example, it is common to leave buffer strips between plots to avoid wind-assisted drift from one plot contaminating adjacent plots. The need for buffer strips increases the amount of land needed for field testing of agricultural chemicals, or reduces the number of treatments that can be accommodated in a single experiment. As the experimental area becomes larger, variability in soil and plant conditions increases, tending to reduce the precision of the experiment. A further benefit of a windproof spraying apparatus would therefore be to reduce the amount of land required for a field experiment and thereby to improve the precision of such an experiment.
Previous attempts to provide spraying equipment with wind protection have involved partially or totally surrounding a spray boom, or individual spray nozzles on a boom, with a shield or skirt which is carried on the boom. Shielded sprayers of this type do reduce wind-assisted drift of spray solution, and can also be used to protect plants sensitive to a chemical from spray application of the chemical close to such plants (for example, in selective application of a herbicide to weeds between the rows of a crop). However, a new problem is introduced which is of particular relevance in resea

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