Bellows arrangement providing failure protection

Claim 1

PRESSURE SENSING APPARATUS COMPRISING: A FIRST BELLOWS INTERIORLY EXPOSED TO THE PRESSURE TO BE SENSED; OUTPUT MEANS CONNECTED TO SAID FIRST BELLOWS AND MOVABLE IN A FIRST AND A SECOND DIRECTION; SAID FIRST BELLOWS BEING OPERATIVE TO MOVE SAID OUTPUT MEANS IN SAID FIRST DIRECTION WHEN THE PRESSURE TO BE SENSED IS INCREASING AND BEING OPERATIVE TO MOVE SAID OUTPUT MEANS IN SAID SECOND DIRECTION WHEN THE PRESSURE TO BE SENSED IS DECREASING; A SECOND BELLOWS HAVING AN EFFECTIVE SURFACE AREA SUBSTANTIALLY EQUAL TO THAT OF SAID FIRST BELLOWS AND BEING CONNECTED TO SAID OUTPUT MEANS; MEANS OPERATIVE ON FAILURE OF SAID FIRST BELLOWS TO COMMUNICATE SAID SENSED PRESSURE TO SAID SECOND BELLOWS; SAID SECOND BELLOWS ARRANGED WITH RESPECT TO SAID OUTPUT MEANS TO MOVE SAID OUTPUT MEANS IN SAID FIRST DIRECTION WITH INCREASING SENSED PRESSURE AND IN SAID SECOND DIRECTION WITH DECREASING SENSED PRESSURE WHEN SAID FIRST BELLOWS HAS FAILED.