Mechanism of Sprayer
Introduction
In this paper, I will introduce the sprayer’s mechanical functions, its appearance and its components. Most importantly, I will also describe in detail how the various components together make the sprayer spray.
Mechanical Function
The mechanical function of the sprayer is to spray a liquid. The sprayer used in agriculture has a big size and the typical liquids are fertilizers, herbicides and pesticides. In contrast, the hand-held sprayer with a small size is typically used to spray water to flowers or shampoo to hair. Apart from the main function as a device to spray liquid, sprayer can also be used as a container for liquid.
Appearance and Components
Figure 1 below are the two kinds of sprayers. The head of hand-held sprayer has a gun-like shape and the head of the sprayer used in agriculture look like a sword. Small-size bottle is used in hand-held sprayer and big-size backpack is used in the agriculture sprayer.
Hand-held sprayer
Sprayer used in agriculture
Figure 1. Sprayer Images
The prayer consists of sprayer head and bottle. There is nothing special about the bottle in the sprayer device, thus we focus on the prayer head components. The sprayer head is made of 5 main parts: trigger lever, pump tube, barrel and nozzle (Figure 2). The user can press the trigger lever to make the pump suck the liquid from the bottle through the tube and push the liquid through the barrel. In the end, the liquid sprays out of the nozzle in the form of tiny drops.
Figure 2. Components of sprayer head
The most complex component of the spray head is the pump. Two key parts of the pump are piston and spring as shown in Figure 2. When the user presses the trigger lever, the piston moves downward, pushes the spring and takes up the volume of the cylinder in which the spring resides. Then the liquid is forced out of the cylinder into the barrel instead of back to the bottle. To make this happen, there is a valve between the cylinder and the tube. This valve only allows the water move from tube to the cylinder and not the other way round. The valve is made up of a ball and a trapezoid as show in Figure 3. The ball is just below the spring. The trapezoid is wide in the above and narrow in the below. The narrow side is narrower than the ball, thus the ball can’t pass it. When the piston pushes down, the spring will press the ball down to the trapezoid and seal this narrow side. Thus, the liquid can’t be pushed into the tube and only goes up to the barrel.
Figure 3. Components of pump
When the user releases the trigger lever, the spring springs back and pushes the piston upward which increases the room of the cylinder and draws the liquid up. Because the air pressure in the cylinder decreases, it will draw the liquid up. The ball is also drawn a little up. Thus, the ball won’t prevent the liquid from passing. To make the low air pressure only draws the liquid up through the tube instead of drawing in the air through the nozzle, there is another valve between the nozzle and the barrel. This valve will prevent the air from passing through the nozzle when the piston moves upward.
When the sprayer is first used, there is usually no liquid sprayed out at the first round of push and release of trigger lever. Because at the first time, there is no liquid yet in the cylinder to be forced out when we press the trigger lever. Only when we release the trigger lever the first time, the liquid is drawn up from the bottle.
Conclusion
Figure 4. Process of sprayer working with various components.
The working process of sprayer can be summed up in Figure 4 above. The push of the trigger lever moves the piston downward and force the liquid in the cylinder out. Because of the valve which consists of ball and trapezoid won’t allow liquid to move downward through the tube. The liquid can only be pushed up to the barrel and spray out through the nozzle. The spring in the cylinder is compressed when the piston moves downward. When we release the trigger lever, It will try to restore its original shape and spring back which pushes the piston up. The expanding of the volume of the cylinder will lower the air pressure and draw the liquid up through the tube.