Fail-safe pressure sensing device

Claim 1

A FAIL-SAFE PRESSURE SENSING DEVICE COMPRISING: (A) AN OUTER CASING HAVING PARALLEL OPPOSED END PLATES, (B) AN INWARDLY EXTENDING PRIMARY BELLOWS SECURED TO EACH END PLATE, (C) AN INWARDLY EXTENDING SECONDARY BELLOWS SECURED TO EACH END PLATE AND ARRANGED TO SURROUND THE ASSOCIATED INWARDLY EXTENDING PRIMARY BELLOWS, (D) A PAIR OF PARALLEL OPPOSED INNER PLATES WITHIN SAID OUTER CASING AND SPACED THEREFROM, (E) EACH INNER PLATE SECURED TO THE COMMON INWARDLY EXTENDING ENDS OF THE PRIMARY BELLOWS AND THE ASSOCIATED SECONDARY BELLOWS TO SEAL SAID PRIMARY BELLOWS WITHIN SAID SECONDARY BELLOWS, (F) ACTUATING MEANS PIVOTALLY MOUNTED AND CONNECTED TO SAID INNER PLATES FOR MOVEMENT IN RESPONSE TO EXPANSION AND CONTRACTION OF SAID PRIMARY BELLOWS, (G) MEANS CONNECTING AT LEAST ONE OF SAID PRIMARY BELLOWS TO A SOURCE OF FLUID PRESSURE, (H) AND MEANS SEPARATE FROM SAID OUTER CASING FOR INTERCONNECTING SAID SECONDARY BELLOWS TO EQUALIZE THE INTERNAL PRESSURE OF SAID BELLOWS WHEREBY THE LEAK AGE FROM EITHER OF SAID PRIMARY BELLOWS WILL BE INTO AN ASSOCIATED ONE OF SAID SECONDARY BELLOWS WHICH IS TRANSMITTED AS INTERNAL PRESSURE TO THE OTHER SECONDARY BELLOWS.