| 摘要 |
906,496. Automatic control systems. GRINNELL CORPORATION. March 26, 1959 [March 31, 1958], No. 10522/59. Class 38 (4). The orientation of a length of piping is maintained constant despite the effects of thermal expansion by automatically controlling an external force applied to the piping in dependence on change of orientation. In Fig. 1, a main steam pipe 10, leading from the superheater header 16 of a boiler 14, is branched and connected to a steam turbine 24 at points 26. To minimize the forces exerted at these connection points due to thermal expansion, any movement of a section 58 of one of the branches from a vertical position, corresponding to a zero force position when cold, causes operation of a two-way switch 56 to run a reversible electric motor 42 in the appropriate direction to restore the piping to a vertical position by adjustment of the force applied at point A. Cables attached at points 59, 60 move by different amounts when branch 58 leaves the vertical so that input shafts 74, 76, Fig. 6, of a differential gear are moved by or against the action of weights 98, 100 and contact 66 of the two-way switch 56 is operated relative to fixed contacts 62, 64. Suitable anchoring of pipe 10 by a pivoted hanger at 230 minimizes the effect of expansion vertically but a modification is described in which separate automatic control systems are employed to maintain constant the orientation of the pipe in each of three mutually perpendicular planes. Rigid links, pivoted levers, and segment gears may serve instead of cables to operate the twoway switch. Arrangements in which the pipe is so fitted that, without the automatic control system, it would be in the desired zero-force position at the working temperature or an intermediate temperature are described. Modifications in which, instead of comparing the movements at two points on the pipe, the movement of one point relative to a fixed point which may be on the turbine casing or on the end of a damped pendulum, are also described. |
