Most modern office chairs use hydraulics or &#;pneumatic&#; lift mechanisms that allow the user to move the chair up and down easily. This enables them to use the science of ergonomics.
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Ergonomics is a combination of disciplines such as anatomy, physiology, psychology and engineering. Essentially, it&#;s concerned with how people interact with their environment and the ways the environment can be changed to ensure safe and effective working practices. For example, ergonomics can be applied to physical objects such as chairs and desks, or it could be applied to a system, such as communications between different departments.
An ergonomic chair is designed specifically to support the body during long periods spent sitting. They have many features that are designed to improve posture and comfort and to help support the health of the user whilst they are working at a desk. These ergonomic chairs usually have mechanisms to help to adjust the seating positions quickly and easily &#; using hydraulics via a lever below the chair.
Hydraulics &#; and pneumatics &#; are the terms used for applications of fluid power. Hydraulics uses incompressible liquid metal (such as oil) to enable machinery movement, and pneumatics use an easily compressible gas such as air (or a pure gas) to enable the same functionality. Hydraulic systems can move heavy loads, however, pneumatic technology is cleaner, used for lighter loads (such as office chairs), and is both safer and easier to store. Both systems use the same technology, however, pneumatics are generally used for office chairs.
Pneumatic chairs are adjustable using a lever generally situated just below the seat. This lever moves the seat up and down in a fluid motion. But how does this work? There are quite a few components that are incorporated into a pneumatic chair! They are:
Gas cylinders, or pneumatic cylinders, are devices that take the pressured power of compressed gas and force it through a chamber which then moves a piston in the required location. This movement and force enable the office chairs&#; seats to rise or lower down. When the lever on the chair is pressed, the gas is pushed in and out of the chamber, facilitating this movement.
If an office chair is used every day and is quite old, the height adjustment might be the first thing to go. If your chair won&#;t go up or down, it is usually because of a faulty gas cylinder, or due to a lift mechanism that won&#;t work. Depending on how old the chair, you could either send it back to the manufacturer, fix it yourself or&#;
We have a fantastic range of office chairs. Whether you&#;re looking for leather office chairs, fabric office chairs or office chairs for under £100, you&#;ll find a host of chairs to suit you at Manutan UK.
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2 >06-18-, 09:53 PM LoveAlbuquerque
Location: Arlington, VA
721 posts, read 1,209,948 times
Reputation: 312
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I bought a wood swivel chair from Massachusetts about 20 years ago. It's a high-quality chair.
Recently I notice that I'm unable to raise the seat height.
I laid it down on the floor and was able to extend the length of the cylinder. See the first photo. However, when I put it upright, the seat sank to the original height. See the second photo.
I noticed that while there was a distance between the black cap and the lower hardware when laid flat, the cap moved down to rest on the lower hardware once in the upright position.
Anyone can advise what to do to keep the seat height without sinking?
06-19-, 09:09 AM K'ledgeBldr
Location: Johns Creek, GA
17,472 posts, read 66,010,995 times
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Turn the collar on the shaft- don&#;t turn the seat or base.
As it&#;s lying on it&#;s side, turning the collar CCW should raise the seat, CW should lower seat.
06-20-, 08:39 AM LoveAlbuquerque
Location: Arlington, VA
721 posts, read 1,209,948 times
Reputation: 312
Quote:
K'ledgeBldrOriginally Posted by
Turn the collar on the shaft- don&#;t turn the seat or base.
As it&#;s lying on it&#;s side, turning the collar CCW should raise the seat, CW should lower seat.
I'm able to adjust the seat height as it's lying on its side by moving the lower part (with the wood legs). Rotating the collar seems to have no bearing on seat height. As a matter of fact, the collar can move up and down the shaft without rotating. It can only be stopped by the metal washer. See the attached photos.However, when it's upright, the lower part (with the wood legs) goes up to meet the metal washer and the collar, causing the seat to sink.What stops the lower part (with the wood legs) to stay put? Could this be due to the damaged metal washer under the collar? It is not flat and is not easy to move along the shaft due to the uneven shape. Shall I replace the metal washer?
Attached Thumbnails
06-20-, 09:25 AM reed303
Location: OH>IL>CO>CT
7,514 posts, read 13,611,290 times
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If the collar can move up and down the shaft without turning, then it is just "decorative". The washer is what is controlling the height, and may look like it's damaged , but is made to "thread" up and down the shaft to control the height.
Try turning the washer towards the base for more height.
FWIW, most chairs of this type the collar and washer are one unit used to control height..
06-20-, 01:09 PM K'ledgeBldr
Location: Johns Creek, GA
17,472 posts, read 66,010,995 times
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Yep- what you're calling a "washer" is what controls the height adjustment. The collar and "washer" are usually one unit- making adjustment easy and not getting oily/greasy!
06-20-, 04:19 PM adjusterjack
Location: Phoenix, AZ
6,340 posts, read 4,894,516 times
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Quote:
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LoveAlbuquerqueOriginally Posted by
What stops the lower part (with the wood legs) to stay put? Could this be due to the damaged metal washer under the collar? It is not flat and is not easy to move along the shaft due to the uneven shape. Shall I replace the metal washer?
Yes.The washer is designed to turn in the threads of the shaft. Like a nut on a bolt.I can see daylight through the washer in one of the photos.That's likely the problem.If you can't find a washer that works you can probably rig something with a clamp that will hold the seat up.
06-28-, 08:49 AM LoveAlbuquerque
Location: Arlington, VA
721 posts, read 1,209,948 times
Reputation: 312
Quote:
adjusterjackOriginally Posted by
Yes.
The washer is designed to turn in the threads of the shaft. Like a nut on a bolt.
I can see daylight through the washer in one of the photos.
That's likely the problem.
If you can't find a washer that works you can probably rig something with a clamp that will hold the seat up.
I'm unable to find a replacement washer with a collar connected to it. Replacing the washer alone would not work, because when rotating the collar, the washer should be rotated as well (to control the seat height). I wish I had more knowledge of the inner workings of the washer and collar in order to fix the issue properly.As a workaround, I use a PVC pipe to increase the chair height by 2". See the attached photo. I put the PVC pipe under the metal washer (that is inside the collar). Since the height is now standard 18", there is no need to adjust the height.
Attached Thumbnails
06-28-, 12:15 PM K'ledgeBldr
Location: Johns Creek, GA
17,472 posts, read 66,010,995 times
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Quote:
LoveAlbuquerqueOriginally Posted by
As a workaround...
That some good "RE" right there!
06-28-, 04:28 PM LoveAlbuquerque
Location: Arlington, VA
721 posts, read 1,209,948 times
Reputation: 312
Quote:
K'ledgeBldrOriginally Posted by
That some good "RE" right there!
What do you mean by "RE"?
06-28-, 09:54 PM K'ledgeBldr
Location: Johns Creek, GA
17,472 posts, read 66,010,995 times
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Quote:
LoveAlbuquerqueOriginally Posted by
What do you mean by "RE"?
&#;Redneck Engineering&#;
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