Spraying Machinery

SPRAYING MACHINERY. The discovery that certain substances in weak solutions or emulsions or in the form of powder could be used to combat many insect and fungus pests of farm, garden and orchard crops and also some weeds led to the development of mechanical devices for spraying the liquids or dusting the powders over the stems and foliage of plants and trees. The name sprayer is usually applied to the machines which distribute liquids and that of duster to those used for distributing powders, though the two types are also referred to as wet and dry sprayers respectively.

Sprayers utilize pressure to force the liquid through a specially constructed nozzle which splits it up into very fine particles or spray. These machines differ according to (a) the complexity of the mechanism ; (b) the kind of power by which they are operated; (c) the method of transport adopted, and (d) the diversity of their accessories. Before dealing with the main types of sprayers it may be as well to describe the various accessories. Nozzles are of two principal types : one produces a jet in the form of a hollow cone and the other a fan-shaped jet—the latter is becoming obsolete. There are, however, many variations and each manufacturer has practically developed a distinct nozzle. The cone-shaped jet is produced by forcing the liquid into a small chamber at a tangent and then through a small hole. If the hole is very small a spring-loaded pin is provided for cleaning the outlet, should it become choked. In some sprayers apertures of different sizes may be fitted so that sprays of varying degrees of fineness may be used. The fan-shaped jet is produced by f orc ing the liquid against a lip, the fineness of the spray depending on the width of the exit aperture. Lances are hollow tubes or rods, to which the nozzles are attached and are used to bring the spray close to the plant or tree and usually have rubber connec tions so that they can be operated in any direction. Spray guns are used in place of lances on powerful machines. They enable the spray to be adjusted by turning a handle which alters the pressure. By using these devices it is possible to spray foliage on the ground and then by increasing the pressure to spray the tops of trees. Spray booms which consist of pipes carrying nozzles at intervals are attached to the machine (which is carried on wheels or a cart) and are used for spraying such field crops as potatoes, and such weeds as charlock. For hops the spray booms are ar ranged more or less vertically, and the machine is drawn be tween the rows. Mixers, stirrers or agitators are often fitted to sprayers in order to ensure the liquid being as uniform as possible; these devices usually operate automatically when the machine is in use. Stop-cocks or cut-offs are used for stopping the flow of liquid at the discretion of the operator.

Manual Sprayers.—The simplest form of sprayer consists of a hand pump with a suitable nozzle, attached to or used in con junction with an ordinary bucket. Another simple type is the knapsack sprayer which, as its name implies, is carried on the back of the operator. This type may make use either of a direct pump or of an air-pump and compressed air chamber for the purpose of projecting the liquid. If the latter device is employed,

a number of preliminary strokes of the air-pump are required before spraying in order to produce the necessary pressure. In either case the machine embodies a container for the liquid (usually 2 or 3 gallons) a lance and nozzle. Larger machines are carried on a wheeled framework or in a cart.

Power Sprayers.

There are two kinds of sprayers operated by power, namely, those which are driven from the transport wheels and those driven by engines mounted on the same frame work. The first type are used mainly for agricultural crops for which they are very suitable, whilst the latter type are more suit able for spraying large orchards. In both cases it is usual to employ horses for hauling the machines, though sprayers which are both propelled and operated by internal combustion engines are being used in America, where large orchards or plantations have to be treated. The essential components of these machines do not differ in principle from those described above. For spray ing tall trees a special type of nozzle is sometimes employed. which is so constructed that the liquid is carried in an unbroken stream to the requisite height before it dissolves into spray: high pressure and considerable power are required to operate machines when using these nozzles, the largest engines developing 6o h.p. Stationary spray plants are used to some extent in the United States, especially in the apple regions of the State of Washington. Such a plant consists of a spray tank, a pump, a gas engine or electric motor, and a pipe line equipped with faucets.

Dusting

machines may be classified in a similar way to sprayers but very few accessories are necessary and generally speaking the machines are of simpler construction: an air blast, produced by means of a fan or bellows, is used to blow the dust into a discharge pipe which may be fitted with a mouthpiece shaped like a funnel or a special spreading device. Mechanical devices are also employed to ensure regular feeding of the powder to the air blast. Manual dusters are similar in size and capacity to the manual sprayers and have a restricted useful ness. For farm work power machines are commonly used, par ticularly in the cotton fields of America. Like sprayers, these machines may be operated from the travelling wheel or driven by an internal combustion engine varying in size from i to 5 h.p. or so. For dusting large areas, aeroplanes have been used, and where large, uniform areas of a single crop require to be treated and the climatic conditions are suitable, the method may be re garded as established. (B. J. 0.; H. G. R.) SPREE (spa), a river of Prussia, 227 m. in length, rising in Saxony, close to the Bohemian frontier, and flowing north past Bautzen, Spremberg and Kottbus, dividing between the first two towns for a time into two arms. Below Kottbus the river splits into a network of channels in the peculiar marshy region known as the Spreewald, then passes Fiirstenwalde and Kopenick, threads Berlin in several arms and joins the Havel at Spandau. Over ioo m. of it are navigable and it is connected with neighbouring rivers by canals.