Buffering device for the operating mechanism of a switchgear, and method of lubrication thereof

A buffering device employed in an operating mechanism whereby opening/closing action of a switchgear is performed by reciprocal drive of a moving body including an electrical contact between open and closed positions, for reducing the speed of said moving body in a vicinity of termination of an action of a switchgear, said buffering device comprising:

• (1) an external cylinder and internal cylinder that are provided on a same central axis;
• (2) a first piston arranged within said internal cylinder, freely slidably arranged on said same central axis;
• (3) a second piston respectively arranged within said external cylinder freely slidably arranged on said same central axis;
• (4) a piston rod freely slidably arranged with respect to said first piston and said second piston;
• (5) a packing fixed in said second piston in a sliding portion of said external cylinder and said piston rod;
• (6) a first return spring seat that is fitted at an end of said piston rod, in order to restrict a range of movement of said first piston;
• (7) a first return spring that is arranged between an end of said internal cylinder and said first return spring seat;
• (8) a second return spring seat that is fixed on said same central axis within said external cylinder;
• (9) a second return spring that is arranged between said second piston and said second return spring seat;
• (10) an oil return path that is formed between said piston rod and said first return spring seat and one end of which is opened/closed by sliding action of said first piston;
• (11) a plurality of through-holes formed in an axial direction in said internal cylinder;
• (12) a plug having a packing, that is fixed at an end of said internal cylinder;
• (13) a high-pressure chamber formed by a space defined by said external cylinder, said internal cylinder, said plug, said second piston and said piston rod, said plug being linked with a drive portion of said operating mechanism;
• (14) a deaerated operating fluid that is sealed in said high-pressure chamber, constructed in such a way that braking force is generated by compression of said operating fluid by said piston rod being forced into said high-pressure chamber on drive of said operating mechanism.