Abstract: Friction plates for a friction type coupling device for displaying a function of braking, holding, accelerating or decelerating by depressing and contacting one friction member against the other friction member of a friction type coupling device composed of two friction plates one fabricated of metals or non-metallic materials or inorganic material. One friction plate has a friction portion which is selectively depressed against the other friction plate and a remaining non-contacting portion. The friction portion is formed as a plurality of protrusions by cutting away, by engraving a plurality of grooves, by cutting away non-contacting portions or by positively forming a plurality of protrusions on the surface of the friction plate.

Abstract: In a conventional frictional force transmitting device used in a vacuum, a problem has arisen when the device performs a sliding action over a certain distance, that is, its frictional force suddenly drops, which makes it impossible for the device to fulfill a desired function of braking. The above-mentioned problem in the frictional force transmitting device used in a vacuum for performing the function of braking, transmitting a frictional force, and effecting acceleration or deceleration, can be solved by improving the device, that is, by means of making its two opposing frictional elements so as to be selectively pressed against each other, in which one of the frictional elements is made of metal or of non-metallic materials and the other made of organic frictional materials, wherein the one of the frictional element made of metal or nonmetallic materials has surface roughness coarser than 3 microns in maximum height(Rmax) and is coarser than the other made of organic frictional materials.