1. Field of the Invention
This invention relates to nozzles that disperse a fluid or fluids to a surface for cleaning, washing, blasting, or allied processes in which fluid impact with the surface is important. In addition, these nozzles have the ability to provide a spray over a large area with a liquid droplet size larger than conventional fantype nozzles having the same pressure and flow. Consequently, a spray over a large area with low overspray and atomization is obtained.
2. Description of Related Art
There has been long-term interest in the use of pressurized fluids to impact surfaces. An example of one such application of pressurized fluids is the use of pressurized water for cleaning and washing of cars, trucks, industrial equipment, floors, driveways, and buildings. In any cleaning operation there are three functions to be performed: (1) the application of water or water and chemicals to soak dirt and film on the surface to be cleaned (soaking function), (2) the removal of dirt and film by the impact of the water jet (removal function), and (3) the application of water for rinsing the cleaned surface (rinsing function).
For a given amount of water in a given volume, the relative relationships between water pressure, velocity, flow rate, and impact energy are proportional: the higher the pressure, the higher the velocity; the higher the velocity, the higher the flow rate; the higher the velocity and flow rate, the higher the impact energy. However, the impact energy actually generated depends on the area of the surface impacted. This relationship between the impact energy and the area to be cleaned may be termed the impact energy density. To achieve a higher impact energy density, either the velocity and flow rate must be increased or the area impacted must be decreased.
In the soaking and rinsing functions, the flow rate of water, and thus the velocity and water pressure, must be sufficiently large to apply the necessary amount of water to cover the surface to be cleaned and to do so in a given amount of time. Particularly for the rinsing function, there is a minimum flow rate that is efficient in terms of time and water usage. In addition, the water pressure must be sufficiently large to project the water to the surface to be cleaned at a high velocity so that the impact energy of the water will be sufficient to dislodge dirt and other particles to perform the removal function. For water usage to be the most economical, a balance between the flow rate and the impact energy just be achieved. This balance must also be taken into account for each of the three cleaning functions.
To produce the desired effects during the soaking and rinsing functions, it is desirable to spread the water or water and chemicals over a large area. One common means of producing a flow over a large area is by a fan-type nozzle. The fan-type nozzle uses a small opening to limit the flow rate and expand the jet over a large area. The small opening causes the jet to break up into small droplets. The velocity of these droplets decreases as they impact the air. This decreased velocity means that the fan-type jet has a low impact energy. Furthermore, because the fan-type jet is spread over a large area, the impact energy density is low.
To produce the desired effects during the removal function, it is desirable to impact the water or water and chemicals over a small area so that there is a high impact energy density. One means of producing a flow over a small area is by using a nozzle that generates a zero-degree jet. Such nozzles are well-known to the art. A zero-degree jet is a jet that does not expand radially with respect to the direction of travel as it is projected from the nozzle. Because the droplets in a zero-degree jet follow the same path, the effects of air drag are decreased and the jet retains much more of its initial velocity than does a fan-type jet. Thus, the impact energy of a zero-degree jet is larger than that of a fan-type jet for two reasons. First, in contrast to a fan-type jet, a zero-degree jet impacts a smaller area, and thus, the impact energy density of a zerodegree jet is larger than that of a fan-type jet. Second, because the aerodynamic drag affects the fantype jet more, the fan-type jet loses its momentum more drastically as a function of distance travelled. Consequently, the zero-degree jet produces a larger impact energy and a larger impact energy density than a fan-type jet.
Another use of pressurized fluids is the application of chemicals such as insecticides and herbicides to a selected area. In these applications, it is important to direct the chemicals to the target area with a minimum of direct overspray or atomization of liquid to avoid susceptibility to drift. Consequently, in addition to requiring high pressure (for distance) and low flow, this application requires large droplet size which is inconsistent with that provided by conventional fan-type nozzle configurations.