The patent is basically designed to alleviate the discomfort you sometimes feel when you move your wrist and your watch tightens. The technology allows for a band that could maintain a constant tension despite changing length. Not only would this increase comfort, it would also optimize the performance and function of the Apple Watch's sensors, which require to be in close proximity to your skin in order to work properly.

A watch band is disclosed. The watch band maintains a substantially constant tension throughout changes in its length while worn by a user. Such changes in length may occur automatically to accommodate changes in the size and circumference of a user's wrist as they move their wrist normally. By maintaining a constant tension, the watch band also maintains a constant force on the user's wrist, and causes a watch body attached to the watch band to also maintain a constant force on the user's wrist. This can increase a user's comfort, since the watch will not get tighter or constrict their wrist as they straighten and bend their wrist. It can also help optimize operation of any sensors in the watch band or watch body that benefit from being held against the user's wrist with a constant force, such as some physiological sensors.

An Apple patent published today has revealed how an Apple Watch band could be engineered to maintain constant tension around your wrist.

The band itself is based around mechanisms that can be moved between extended and non-extended positions, adjusting the size and tension of the band as you move your wrist. As AppleInsider notes:

According to the filing, the band could contain opposing spring segments at a pivot point, as part of a number of compliant mechanisms throughout the band itself. The segments are able to extend and contract between two positions, with the springs keeping the band at a desired level of tightness throughout its motions. In short, the mechanisms increase the length of the band when the wrist circumference increases during movement. When the wrist circumference shrinks down, the mechanisms revert back to their previous form.

Not only can the mechanisms be opened up simultaneously, they can also be manufactured to open sequentially, so that some parts of the strap would "stretch" before others, taking the pressure off more vulnerable parts of the band. Not only would this enable the watch to maintain tension, but Apple claims it could do so without the width of the band changing so as to stop the band thinning out as though it were being stretched.

Apple has previously tried to get Apple Watch users to wear their bands in a particular way to ensure that sensors give accurate readings, however perhaps a more long term solution would be to provide a band that can maintain a constant level of tension so that you know your sensor results are always consistent. Of course, a patent filing is no guarantee we'll ever see this product in the real world, but it's certainly an interesting idea!