Abstract: A slack adjuster (500) is provided that is particularly advantageous for use in tensioning vehicular timing belts or chains. Adjuster (500) has substantially coaxially aligned status plunger (48), dynamic plunger (74), and sleeve (66). A first check valve (56) controls fluid flow between a first low pressure fluid reservoir or chamber (50) on plunger (48) and a second fluid chamber (84) in plunger (74). A second check valve (80) controls fluid flow between chamber (84) and a third fluid chamber in sleeve 66 includes a passageway (84) and also operates to prevent air from re-entering chamber (82) from passsageway (84).

Abstract: A resilient cage (100) is provided for retaining a check-valve (56) in registration with a passageway (54) through an end wall of the static plunger (48) for controlling fluid flow from a first fluid chamber (50) into a second fluid chamber (60). Static plunger (48) includes an annular groove (52) in its outer surface proximate the end wall and cage (100) includes a radially inwardly extending flange (6) that is adapted to extend into groove (52) and secure cage (100) in the manner of an end cap about the end of static plunger (48). Cage (100) also serves to retain static plunger (48) together with a dynamic plunger (28) containing chamber (60) against the force of a spring (64) tending to separate plungers (28 and 48) after assembly.

Abstract: A hydraulically operated chain or belt tensioner is provided which in a preferred embodiment (500) features a piston or dynamic plunger (56) slidably received within a bore (54) of a housing (52) that includes a fluid chamber (65) that is vented by at least one air vent (76) extending through housing (52) that is oriented relative bore (54) such that tensioner (500) can be rotated a predetermined angular amount alpha relative horizontal with vent (76) maintaining a slope (B) greater than zero enabling entrapped air to escape from chamber (64) and preventing a substantial amount of fluid to drain therefrom by gravity when unpressurized.