Braking apparatus for door closer

Claim 1

In a door closer comprising a main shaft, a torsion spring, a rotor, a cylinder, a first pressure chamber and a second pressure chamber formed in said cylinder, and a check valve provided on a blade provided within said cylinder, wherein, when a door to which said closer is connected is opened, said torsion spring is subjected to torsion by said main shaft to thereby rotate said rotor so as to open said check valve to allow operating oil in said second pressure chamber to flow into said first pressure chamber through a first oil hole, and when said door is closed, said rotor and said main shaft are reversely rotated by a recovery force of said torsion spring to thereby close said door, a braking apparatus for said door closer comprising: a second and a third oil hole formed communicating with said second pressure chamber and said first pressure chamber, respectively; a communicating oil hole formed in a circumferential wall of said cylinder so as to communicate with said second and third oil holes; a slide valve slidably positioned in said communicating hole in the axial direction thereof and provided with a valve rod having a head portion and a braking valve portion which are formed at one end of said valve rod and a position corresponding to said third oil hole, respectively, so as to be tightly fit in said communicating hole; an elastic member urging said slide valve in the direction opposite to a flow direction of said operating oil when said door is closing so as to cause said slide valve to fit into said communicating hole; and an adjusting screw threadedly engaged in an opening portion of said communicating hole for positioning said slide valve in said axial direction.