| 摘要 |
A typical door closer has a cylinder in which a piston reciprocates to compress a spring. An assistor for such a closer has a cylindrical shell fastened to one end of and continuing the cylinder. The shell has a barrier wall at one end adjacent the cylinder, a partition wall dividing the shell into a booser compartment and a main compartment, and a head wall at the other end. Air under regulated pressure is supplied to the main compartment, wherein the air presses a main plunger tube, extending through the partition wall, against a booster plunger having a rod extending through the barrier wall and abutting the piston. A port in the plunger tube receives air from the main compartment through the tube. In some plunger tube positions the port is blocked by the partition wall and in other plunger tube positions opens into the first compartment. A check valve when open allows air flow from the booster compartment to the main compartment. Air under regulated pressure is supplied to the main plunger throughout the whole piston stroke and is supplied to the booster plunger during only part of the piston stroke. The applied air pressure is regulated to be slightly less than an amount necessary to compress the spring and move the door unaided.
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