granted april 28 1987 to tillmann et al for 34 door closer 34 the just discussed passage in the housing 10 contains a throttle valve which is adjacent the plug 13 and serves to restrict the flow of fluid in that portion of the passage which communicates with the chamber 22 during pivoting of the door panel to its closed position the head 19 of the piston 17 and the end wall 12 of the housing 10 define a second chamber 27 which contains a set of coil springs 25 e g of the type disclosed in u s pat no 4 658 468 which bias the head 19 in a direction toward the shaft 14 and ensure that the head 19 can damp the movement of the door panel to its open position the bias of the springs 25 is adjustable by a disc shaped retainer 26 which is adjacent the end wall 12 and is movable toward or away from this end wall by a mechanism similar to or identical with that disclosed in u s pat no 4 658 468 the pressure in the chamber 27 rises during movement of the door panel to its open position and the fluid which fills the chamber 27 is then free to escape into the compartment 22 by way of an axially parallel channel 28 in the housing 10 the illustrated channel 28 is an axially parallel blind bore which is machined into the housing 10 the open end of which is sealed by a plug 28a which communicates with the compartment.