PURPOSE: To protect a pressure sensor from an excessively large differential pressure by such an arrangement wherein a by-pass is caused to open when a differential pressure exceeds a certain limit, and fluid at both sides of the pressure sensor is caused to interflow.
CONSTITUTION: When an opening inside the body 1 of a bypass 20 is caused to open to the right of an O ring 12 by a differential pressure exceeding a certain limit, fluid entering through an inlet 15 at the right hand side flows toward an inlet 16, and by this flow, the pressure of fluid at the right hand side falls, and on the contrary, the pressure of fluid at the left hand side rises, and the difference between the pressure of fluid at the left side and that of fluid at the right side of a movable element 11 equilibrates with the righting moment of bellows 13, 14 at such a position at which the O ring 12 causes the opening inside the body of the bypass 20 to slightly open to the right of the movable element 11, and even if the pressure of fluid at the right hand side rises further, the position of the movable element 11 is hardly varied, and consequently undue force will never be applied to the bellows 13, 14.
MITAKE MASARU
TOMIOKA SHINJIROU
