| 摘要 |
A two-component sealing ring, e.g. for pistons and cylinders, comprises an inner portion of uniform rectangular section and an outer portion also of uniform rectangular section, on of these is of a urethane of high tensile strength (at least 350 kg/cm2) and abrasion resistance, while the other is of a urethane of low compressive deformation (less than 2% in 22 hours at 70 degrees C). Preferably the ratio of the thicknesses of the low-deformation portion (14) to the high-strength portion (12) is approx 3:1. The high-strength portion (12) may be on the inner side and the low-deformation portion (14) on the outer side, e.g. for a cylinder ring, or vice versa, e.g. for a piston ring. By obtaining a direct balance between wear resistance and strength on the one hand and low deformation on the other hand, good sealing combined with long life is obtained. The high-strength portion is of urethane comprising 100 parts CYANAPRENE A-9 and of 11.3 parts CYANASET M. (In an example this gives a maximum tensile strength of 455 kg/cm2). The low-deformation part comprises a urethane consisting of 100 parts CYANAPRENE A-8, of 4.80 parts ISONOL 93 and of 2.34 parts of CYANASET M. (In an example, this gives a pressure deformation in 22 hours at 70 degrees C and for 25% compression of 0.1%. The two components are made by introducing the required quantity of a first component into a mould and centrifuging it or produce the outer layer until it has set, then the required quantity for the inner layer is introduced and similarly centrifuged until it has set. |
