1. Field of the Invention
This invention relates generally to spray devices for applying liquids to ground surfaces from a moving vehicle, and more particularly, the invention relates to an improved spray device for mounting upon a wheeled carrier for applying low volumes of agricultural chemicals such as pesticides and plant growth regulators in a manner to prevent dribble from the applicator and subsequent plant burn.
2. Discussion of the Prior Art
There are a number of known types of spray devices which are available for the ground application of various types of treatment liquids, such as herbicides, insecticides, fungicides, fertilizers, plant growth regulators and other agricultural chemicals. Most often, such applications are accomplished by the use of suitable spray nozzles which may be mounted upon vehicles through an intermediate boom or extension device. A chemical storage tank of suitable capacity is mounted upon the vehicle and is in fluid communication with the spray nozzles whereby the nozzles can be directed to apply the product upon either a generally horizontal spray target area, such as golf course turf or farm growing areas or on generally vertically extending target spray areas, for example, the shrubbery and other growth that can be present immediately adjacent to the lateral edges of vehicular highways.
One suitable spray device for this purpose has been developed by the present applicant and forms the subject matter of a copending patent application entitled "Ground Spray Applicator", filed July 15, 1986, Ser. No. 885,773, now U.S. Pat. No. 4,760,963.
The previously available agricultural spray devices, including the device described in the said copending patent application all generally exhibited a common problem in that the nozzles exhibited a tendency to drip or dribble during spraying whereby droplets or an accumulated amount of liquid chemical composition could be developed at the spray nozzles and could be dripped directly upon the ground surface, rather than be distributed as part of a uniform fine spray mist pattern. Normally speaking, when the spray target area comprised a relatively rough or unfinished area, for example the lateral edges of most highways, then the inherent dribble attendant with the spray equipment was either not noticeable or not of sufficient consequence to require any changes in the equipment. However, when the spray target area comprised an agriculturally improved and finished area, for example, the fairways and greens of a golf course, then such dribble was both noticeable and unacceptable. Prior workers in the art have become aware of the unacceptable nature of the spray dribble when the liquid chemical droplets settled to the ground. The droplets would then apply an increased concentration of liquid chemical product upon a greatly decreased agricultural surface than would normally be encountered when the material was delivered in the usual fine spray or mist configuration. Such chemical concentration could easily burn or otherwise damage the effected turf areas, thereby killing the grass in a highly visible manner that was entirely unacceptable and inexcusable.
Additionally, following completion of a spraying operation, the main chemical supply valve was then normally or electrically functioned to close the valve. The valve closure usually resulted in trapping a small quantity of liquid chemical in the hose or hoses intermediate the chemical storage tank and the spray nozzles. This trapped material could often escape through the nozzles to thereby fall upon the ground in concentrated form, to additionally cause unintentional grass burn. While such dribble or dripping could be considered to be inherent in the usual spray apparatus of the type currently available for agricultural chemical delivery, and even though there must be a small amount of liquid chemical inherently remaining in the hoses after shut off of the main supply valve, the need remains to find a simple solution to the dribble problem to prevent damage to finished grass areas.