| 摘要 |
A unidirectional drive assembly that is operable to rotate an indicating pointer in an up-scale direction responsive to rotation of an input drive gear wheel in either a forward or a reverse direction. The assembly is characterized by having an idler gear shift assembly coaxially mounted in nesting relationship with a ratio gear assembly in a compact arrangement between supporting members of a frame assembly, in combination with a register indicator gear assembly and an idler gear rotatably mounted in continuous meshing engagement with a gear in the register indicator gear assembly. The idler gear shift assembly is operable to selectively move either a first or a second idler gear into meshing engagement respectively with either the gear on the register indicator gear assembly or with the idler gear continuously meshed therewith. The idler shift assembly performs its shifting operation responsive to reversal of the direction of rotation of the ratio gear assembly, thereby to cause the register indicator gear assembly to drive a register indicator in an up-scale direction regardless of the direction of rotation of the ratio gear assembly which is directly responsive to the direction of rotation of an input gear wheel driven by a meter gear train on which the unidirectional drive assembly is mounted. |
