Various chemicals are used in farming today to improve productivity and yield. Such chemicals can take either liquid or granular form, and can comprise fertilizers, pesticides, or insecticides which tend to be relatively expensive and must be applied at the proper rate to achieve the intended purposes without undue waste of the chemical and/or lost productivity and yield.
Various liquid chemical applicators or sprayers have been available heretofore. Such sprayers generally incorporate a large tank connected by suitable lines and pumps to nozzles or spray heads mounted along a transverse tool bar. The chemical concentrate is first mixed in the proper ratio with water in the tank on a batch basis after which the sprayer is driven or towed across the field to effect application by means of spraying. Application at the proper rate depends upon proper coordination of the spray rate of chemical mixture and the speed of the applicator.
Although the chemical sprayers of the prior art have been generally satisfactory, they have not been without drawbacks. The primary drawback is the need to carefully coordinate the speed of the sprayer and the spray rate to achieve the proper application. Although electronic monitors are available for helping the driver to coordinate the speed and flow rate, such devices tend to be complicated and expensive, and so this is typically done by the operator on a trial-and-error basis. If the sprayer is driven or towed too fast, this results in under-application of the chemical, resulting in leftover chemical mixture which most often goes to waste because it cannot be stored or used. Re-spraying is impractical. Conversely, driving or towing the sprayer too slowly causes over-application and thus early runout of chemical, resulting in lost time and more expense in returning to refill the tank with water and chemical concentrate. These difficulties of course lend uncertainty to the amount of chemical to be purchased for use, and thus excess chemical concentrate is often unnecessarily purchased.
Another drawback to the chemical sprayers of the prior art has been the manner in which the spray heads or nozzles are supported and maintained at an effective distance above the ground or plants as the sprayer is driven or towed across the field. It will be appreciated that farm fields can be rough and uneven, and that such sprayers are subject to bumps and shocks which affect the spacing for proper application. Mounting the spray heads or nozzles on rigid tool bars does not compensate for unevenness of the fields. Shock absorber systems can be adapted to such sprayers, but these tend to be relatively complicated and expensive, and they may not effectively maintain the proper spacing over bumps as well as depressions.
Yet another drawback to the prior devices is that once the liquid and chemical concentrate are mixed in the tank, neither the mixture ratio nor the type chemical being applied can then be readily changed. Changeover from one chemical to another is time-consuming and expensive, and usually cannot be done in the field. It is impractical to store unused chemical mixture particularly from one planting season to the next. Also, such mixture is at least mildly toxic and should be disposed of in an environmentally-safe manner, but often has not been done so for reasons of expedience.
There is thus a need for an improved chemical sprayer which automatically compensates for speed to avoid the guesswork in achieving proper application, and which stores the chemical concentrate and water in separate tanks for mixture as needed during application so that any excess concentrate is not diluted and can thus be stored for use later.