How A Spray Bottle Works?
- t12machinedesign
- Aug 8, 2021
- 6 min read
We use spray bottles in our everyday lives without realising their mechanisms most of the time. Spray bottles are an advantageous machine type and a great example of the basics of plumbing. Many of us only know that these work on a principle that involves pressure differences, but we hope that you’ll have a better and greater understanding of its working. After going through this report
Working Principle:
The principle of the spray bottle is to form a high-pressure system in the bottle, and the liquid in the bottle is sprayed out in the form of extremely fine water particles with a higher pressure drop. This is called a reciprocating pump system. Even the human heart works with the same principle. When it dilates, low-pressure blood enters the heart through a one-way valve. And when the heart contracts, the high-pressure blood is pumped back through another check valve to the body. We’ll see how the high pressure is created inside and why the fluid rises in the next section.
Parts and Mechanism:
A spray-bottle head is composed of simply a few components. In simple terms, it has a trigger lever, piston, spring, cylinder, pump, thin plastic tube, bottle and two one-way valves. It features a lever that activates a tiny pump. This pump is connected to a tube made of plastic that pulls the fluid (cleaning fluid in this case) from the reservoir's bottom. It pushes a tiny hole at a pump's muzzle to drive this liquid down a tight barrel. The nozzle, or hole, focuses the fluid into a concentrated stream.
Pump
In this design, the fluid pump is the only complicated part, and it will be as basic as possible. A piston, contained inside a cylinder, is the most crucial moving element. There's a tiny spring within the cylinder. You pull back the trigger and press the piston in the cylinder to run the pump. The piston moves compress the spring such that the piston is pushed out of the cylinders when you release the trigger. The whole pump cycle is formed from these two piston strokes, in the cylinders and out again.
The downstroke, which pushes the piston inwards, reduces the cylinder area, throwing the fluid out. The start, which pushes the piston out of the spring, widens the cylindrical region and pumps fluid in it. You must suck the fluid within the spray container from the bottom reservoir and push it out by the barrel above. The pump must only drive the fluid up; it should not force this fluid back into the reservoir to have the whole fluid flowing across the barrel. In simple words, the fluid just has to flow in one direction via the pump.
One-way Valve:
This device used for this mechanism is referred to as a one-way valve. The pumping system in this spray bottle features two one-way valves. One of them is between the reservoir and the pump, and the other is between the nozzle and the pump. The valve between the pump and the reservoir typically consists of a little rubber ball, which carefully lies within a small seal. The sides of the seal are cornered to prevent the ball from falling. Depending on the design, this ball is held against the seal either by gravity or a tiny spring to stop the water path while not being pumped.
When the trigger is released, i.e. when the piston travels out, the expanding region of the cylinder draws up the underneath fluid and pulls the ball out of the slot. The liquid flows from the reservoir since the ball is raised. But when the trigger is pressed, the flowing fluid's outward force pushes the ball into the seal, closing the entrance into the storage cell. The pressurised fluid will thus only be forced into the barrel.
The one-way valve between the pump and the nozzle in a spray mechanism is some kind of a cup that fits on the outer end of the barrel. The internal pump pressure holds the cup against the barrel on the upstroke so that air can not flow through the pump. At the bottom, the fluid getting pulled out raises the cup slightly from the barrel and goes out through the nozzle. Without the second one-way valve, the pump mechanism can't take fluid from the reservoir since it wouldn't suck (no drop in air pressure). The air pressure in the pump would not be reduced by up stroking; it will just pull in more air to balance out the pressures.
First-time Usage:
You have to press the trigger a few times for the cleaning fluid to spray when using a spray bottle for the first time. Two things cause this delay:
The gun is initially set for a downstroke, not an upstroke. That means before you start pumping, the piston is not present inside the cylinder. Only air is in the cylinder chamber when the trigger is initially pulled back and the piston pushes in. To draw fluid from the reservoir, the piston must move.
The pump begins to suck the cleaning liquid from the reservoir with the first upstroke. However, it also sucks in the air already present in the plastic tube that connects to the reservoir. You need to push this air through the pump mechanism before you can spray the cleaning fluids. This could take a few up and down strokes.
How are all the parts connected?
Mechanical Parts are many a times connected by screws, bolts and rivets, or by adhesives.
But there’s an other way where the parts can fit with each other just by interlocking. In the spray bottle we considered for assessing, neither screws nor adhesives were used.
The bottle was connected to the cap using a simple threaded fastener. The others parts are fitted to each other by interlocking, so that a part cannot move at all, or only move in the desired direction due to the interlocking.
Materials Used:
Most of the parts in the spray bottle are made of plastics derived from polyesters and polyolefins (like PET). The spring used is made of metal, primarily stainless steel. The body of the bottle can be made of aluminium or glass. But these materials are only used in cases when plastic containers cannot be used to store the solutions or as a fashion. The household spray bottles are all plastic, though. The ball in the one-way valve is usually made of chrome-plated steel, chrome-plated brass, rubber, stainless steel or PVC.
So as we can see, more than 95% of a spray bottle is made of materials derived from plastic. We only found the spring and the small sphere in the one-way valve to be made of items other than plastics.
The main reasons for so much usage of plastic is:
Durable
Lightweight
Cheap
Strong
Waterproof
Easily moldable
Easy manufacturing
Problems:
The materials used in spray bottles are generally not recyclable. Though much research and effort has been put into recycling plastics, there isn’t a permanent solution for it yet.
As a source on blog.repurpose.global has said “Just like producing virgin plastics, recycling plastics have the same threshold for emitting noxious gases into the atmosphere. In 2017 China announced that it no longer wanted to be everyone's “garbage dump,” as it recycled 50% of the planet's plastic products” which emitted huge amounts of toxic gases.
Many household cleaning products come in spray bottles, but the bottles are often designed in such a way to make it difficult to access the last bit of product. Not only that, but the nozzle can clog and the spray mechanism itself can simply stop working. These problems should be simple to rectify so you don't have to buy a new bottle of product, and you can save the empty bottle to use again.
The plastic tube connected to the sprayer is designed to reach to the bottom of the bottle, but it often curls up, and the end protrudes from the liquid in the bottle when the level is low.
Solutions:
One of the solutions will be to use spout pouches instead of plastic containers. Though spout pouches are also not entirely recyclable, they offer many eco-friendly benefits, for example they have only 10% carbon footprint.
Instead of using plastics derived from polyolefins and polyesters, using Polylactide acid (PLA) saves two thirds the energy required to make traditional plastics. PLA looks and behaves like polyethylene and polypropylene and is widely used for food containers and other plastic items. PLA also produces almost 70 percent less greenhouse gases when it breaks down in landfill sites.
Though usage of bioplastics might not be right for each fluid in a spray bottle, but can be used if compatible with.
References:
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