How do soap bottle pumps work?
Hey friends, Happy Wednesday!
Let’s look at how shampoo bottle pumps work this week. I aim to write my newsletter issues in a way one can follow them while traveling on a bus, having a coffee, waiting for food, etc. Let's jump in!
The shampoo, moisturizer, and most of the products in our restrooms use the bottle pump. They work counterintuitively - pushing down on the pump forces the product to move upward.
How it works: 15-second answer
The shampoo bottle pump utilizes a piston mechanism. As the pump head ascends, it generates low pressure, drawing shampoo upward from the bottle like a straw. Conversely, when the pump is depressed, a ball prevents the shampoo from returning to the bottle. The depression unblocks a hole in the tube, enabling the liquid to be forced upward through the tube and be dispensed.
Answer to the question I posed last week
Last week, I asked how can one control a hot air balloon to move in different directions. Hot air balloon pilots use the knowledge of wind direction and speed at different heights to steer the balloon.
How does a bottle pump work?
I’m taking a bottle of shampoo as an example to explain further.
Components:
When you press the pump head of the bottle, you are pushing down the tube (marked in light blue).
This compresses a spring attached to the tube.
A ball (marked in dark red) is attached to the other end of the spring to block or allow the shampoo through the opening.
The piston (marked in red) forces the shampoo to enter the small circular hole on the tube (pointed in green) when the pump head is depressed. But the same hole is closed when the pump ascends. (see Figure 1)
Figure 1: Piston not blocking the hole on the tube when the pump head is depressed (LEFT); Piston blocking the hole when the pump head is back up at the normal state (RIGHT). Source: Branch Education
The red piston can slide a bit along the tube. This leeway is given so that the piston will block the hole when the pump is not pushed down. (as shown in Figure 1)
Working explained:
Case 1: Pump head moving upwards
The hole in the tube is blocked by the piston during this phase.
Consider drinking water through a straw. We create a low pressure within the straw by sucking the air away. The physics is very similar here. As the tube moves upwards, we give more space for the air molecules to occupy under the piston.
So there is a low pressure under the piston. This causes the product in the bottle reserve to enter the grey static tube due to the pressure difference as seen in the following gif.
Figure 2: Shampoo drawn upwards while the head pump moves upwards due to the low pressure created under the piston.
Case 2: Pump is depressed (pushed down)
Now, we have the shampoo under the piston. In this phase, the ball is pushed against the opening, preventing the shampoo from returning to the bottle.
As the pump is depressed, the hole in the tube is not blocked by the piston. This forces the liquid upward through the tube and is eventually dispensed through the nozzle for use as seen in the following gif.
Figure 3: Shampoo forced upward through the hole in the tube as the ball blocks it from returning to the bottle.
This is how a bottle pump works!
Task of the week
Open a bottle pump and look at this contraption when you get a chance. And let me know by replying to this email if you were able to relate to it. I'll show a real-life image of this in my next newsletter issue.
Tweet of the week
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Thank you for reading! And don’t forget to refer your friends to this newsletter if you are enjoying them. It’d be of great help.
Have an amazing rest of the week, and take care!
Until next to next Wednesday,
Chendur
