Patent attributes
A rotatable module includes a pivotal shaft, a rotating washer, a stationary washer, a resilient member, and a fixing member. The rotating washer is rotatably sleeved on the pivotal shaft. The stationary washer is non-rotatably sleeved on the pivotal shaft. The fixing member prevents the above mentioned components from detaching from each other. The rotating washer and the stationary washer have an engaging surface and a resisting surface respectively. The engaging surface resists the resisting surface due to a force of the resilient member. The engaging surface forms a plurality of protrusions, and the resisting surface defines a plurality of grooves to engage with the protrusions. The resisting surface further defines at least one buffering portion adjacent to at least one of the grooves or in at least one of the grooves to receive material flowing from other portions adjacent to the at least one of groove.
