| 摘要 |
Pointer zero adjustment in a pressure gauge is effected by means of a shaft (50) centrally extending laterally inward of the casing from a supportive centering flange (40) on the inside face of the crystal (10). A Bourdon tube (44) is radially coiled concealed from view through the crystal (10) about a pressure sealed rear portion of the shaft (50) to which it is rotationally secured. The pointer unit (42) is of a more or less U-shaped cross section with a tubular center (48) loosely supported on the shaft (50) juxtaposed to the crystal (10). The front pointer formation (42) simulates a conventional pointer appearance while its rear formation (52) is rotatably linked to the free end (56) of the Bourdon tube for incurring operational displacement therewith. On removing a detachable cover (37) from over an aperture (34) in the crystal coincidingly located opposite the shaft end thereat, access is provided for an external tool (78) to operationally engage a tool receiving hex socket (38) in the shaft end. Arcuately displacing the shaft (50) via the tool (78) calibrationally positions the pointer (42). By crystal (10) being of composition and thickness affording a spring rate of matched correlation to maximum anticipated inlet pressure, the crystal provides a secondary function for relieving overpressure. |
