| 摘要 |
Linear displacement optical transducers have a movable carriage supporting an optically encoded track which is movable along a cylinder supporting an optical read head. In the present invention, the transducer is sealed by a tubular flexible bellows which extends within the cylinder, is joined at one end to the carriage and at the other end to an open end of the cylinder. A compensation chamber is sealed to the outside of the cylinder to enclose a major part of the length of the bellows and forms a sliding seal with a push-rod coupled with the carriage. The bellows encloses a first volume of a dry inert gas within the cylinder to one side of the bellows and a second, similar volume of gas on the other side of the bellows and in the compensation chamber. Displacement of the carriage causes only a small change in pressure across the bellows which is accommodated by flexure. The compensation chamber isolates the bellows from atmospheric pressure change and ensures that temperature change affects both volumes equally, minimizing pressure difference across the bellows. |
