US 4,708,696 AGranted

Tensioner for toothed drive belts

AssigneeTsubakimoto Chain Co.

InventorsKazuo Kimura, Masao Maruyama

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Abstract

A tensioner for toothed belts comprises a hydraulic fluid filled cylinder having a piston with a rod projecting out of the cylinder and engaging a pivoted arm with a roller at one end for engaging the belt. A spring within the cylinder urges the rod in the projecting direction, and a check valve carried by the piston allows the rod to project rapidly to take up slack in the belt. Hydraulic fluid, however, flows through the small clearance between the piston and the cylinder wall as the rod retracts, and therefore limits the rate of retraction. A path is provided between seals surrounding the rod to route air directly to the reservoir so that it does not enter the fluid chambers within the cylinder. The piston material is chosen to expand more rapidly than the cylinder with increasing temperatures to reduce variations in leak-down time.

Claims21

Dependent claims

in which the second fluid passage allowing relatively restricted flow of hydraulic fluid from said other chamber to said one of said chambers is provided by a clearance between the piston and the cylindrical interior wall;
in which the check valve is carried by the piston;
and
in which the first fluid passage comprises a first part extending axially through the piston and a second part, communicating with the first part, said second part extending transversly through the rod.

1 more element

A tensioner for a toothed belt comprising means providing a cylindrical interior wall, a piston slidable within, and substantially conforming to, the cylindrical wall, a rod connected to the piston and extending, substantially along the axis of the interior wall, from the piston to the exterior of the interior wall providing means, packing means surrounding the rod and, with the cylindrical wall and piston, forming a substantially enclosed first chamber on one side of the piston, means cooperating with the interior wall providing means and the piston forming a substantially enclosed second chamber on the opposite side of the piston, hydraulic fluid substantially filling both chambers, a first fluid passage having one-way check valve means allowing flow of hydraulic fluid from one of the chambers to the other as the piston moves in a direction to decrease the volume of said one of the chambers, spring means urging the piston in said direction, means providing a second fluid passage allowing relatively restricted flow of hydraulic fluid from said other chamber to said one of said chambers as the piston moves in the opposite direction, said tensioner having a hydraulic fluid reservoir, the means providing a cylindrical interior wall having an exterior wall, a part of the exterior wall constituting a part of the boundary of the reservoir, and having a third fluid passage through said part of the wall providing fluid communication between said reservoir and said first chamber, said packing means comprising first and second packing elements axially spaced from each other, and a fourth fluid passage extending through said part of the wall from the space between the packing element to the reservoir, the reservoir being located above the rod, and the fourth fluid passage extending upwardly from the space between the packing elements to the reservoir whereby air drawn in along the surface of the rod toward the first chamber is carried upwardly into the reservoir and thereby prevented from entering the first chamber.

Dependencies are inferred from the claim text.