Differential pressure instrument

Claim 1

IN A DIFFERENTIAL PRESSURE INSTRUMENT, IN COMBINATION, A PAIR OF BOURDON TUBES, EACH HAVING A FREE MOVABLE END AND DISPOSED RELATIVE TO EACH OTHER SO THAT THEIR FREE ENDS ARE MOVABLE ALONG SPACED SUBSTANTIALLY PARALLEL PATHS, SAID DISPOSITION OF THE TUBES BEING SUCH THAT THEIR FREE ENDS MOVE RESPECTIVELY IN OPPOSITE DIRECTIONS WHEN THE PRESSURE IN BOTH TUBES INCREASES RELATIVE TO THE PRESSURE OUTSIDE THEM AND WHEN THE PRESSURE IN BOTH TUBES DECREASES RELATIVE TO THE PRESSURE OUTSIDE THEM, LINKING MEANS EXTENDING CROSSWISE OF THE PATHS AND PIVOTALLY CONNECTED AT ITS ENDS RESPECTIVELY TO THE FREE ENDS OF THE TUBES FOR LINKING SAID ENDS OF THE TUBES, SAID LINKING MEANS INCLUDING TWO FLEXURES RESPECTIVELY CONNECTED TO THE FREE ENDS OF THE TUBE AND TO THE ENDS OF THE LINKING MEANS AND CONSTITUTING THE AFORESAID PIVOTAL CONNECTION OF THE LINKING MEANS TO THE TUBE ENDS, EACH OF THE TUBES BEING ARRANGED SO THAT THE PATH OF MOVEMENT OF ITS FREE END IS A SUBSTANTIALLY STRAIGHT LINE,AND EACH OF THE FLEXURES COMPRISING A SPRING STRIP LYING IN THE SUBSTANTIALLY STRAIGHT LINE PATH OF THE TUBE END TO WHICH SUCH FLEXURE IS CONNECTED, AND MEANS COMPRISING A MOVABLE ELEMENT CONNECTED TO THE LINKING MEANS AT A LOCALITY INTERMEDIATE SAID ENDS OF THE LINKING MEANS FOR DISPLACEMENT BY SAID LINKING MEANS UPON DISPLACEMENT OF ONE OF SAID TUBE ENDS DIFFERENTIALLY RELATIVE TO THE OTHER, TO MOVE SAID ELEMENT ONLY IN ACCORDANCE WITH THE CHANGE OF THE PRESSURE IN THE INTERIOR OF ONE TUBE RELATIVE TO THE PRESSURE IN THE INTERIOR OF THE OTHER TUBE.