| 摘要 |
A Mach airspeed indicator instrument has a pointer that is rotatable around an airspeed scale and a Mach scale, the Mach scale itself being rotated in response to altitude change. A marker can be rotated around the scales via a cam that is manually rotated by an external knob. Rotation of the Mach scale is coupled via two vertical links and a lateral arm to rotate a gear ring which carries a peg. When the gear ring reaches a certain position the peg contacts and displaces a similar peg which rotates the marker with the Mach scale. The Mach value at which this occurs is adjusted manually from outside the instrument by a knob. Twisting the knob causes a vertical displacement of a mounting bracket on which the lateral arm is pivotted. The lateral arm is fixed at the end coupled with the Mach scale so that it rotates about that end causing rotation of the gear ring without affecting the Mach scale.
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