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.
Mechanism of Sprayer
Introduction
Mechanical Function
Appearance and Components
Conclusion