Cylinder for mastic gun - has sealing ring on piston which moves in tapered recess of piston skirt

摘要

The cylinder, or cartridge, (1) foe mastic has a bore (12) in which a piston (6) is slidable to expel the mastic. The skirt of the piston, towards the head, has a tapered recess which forms an annular space (15) with the bore (12). A sealing ring (19) is located in the recess to form a seal with the bore (12). As the piston is moved, the ring rides along the recess, increasing its interference and the tightness of the seal. When the sealing ring is at the maximum dia. portion of the recess it is under a compression of from 0 to 20% pref. 10%.