Device for indicating a predetermined fluid pressure differential

Claim 1

A SIGNAL DEVICE FOR INDICATING A PRESSURE DIFFERENTIAL BETWEEN TWO FLUID-PRESSURE CONDUITS, SAID DEVICE COMPRISING: A CNDUCTIVE BLOCK HAVING A HOLE OPENING AT OPPOSITE SIDES OF SAID BLOCK, SAID HOLE HAVING A CENTRAL PORTION OF REDUCED DIAMETER; DETECTOR MEANS MOUNTED IN SAID BLOCK WITH A PORTION THEREOF HAVING FREEDOM OF MOVEMENT WITH RESPECT THERETO ALONG THE AXIS OF SAID HOLE, SAID DETECTOR MEANS PROJECTING LATERALLY INTO THE SAID CENTRAL PORTION; PISTON MEANS SLIDABLY MOUNTED IN SAID CENTRAL PORTION, AND HAVING PORTIONS ON OPPOSITE SIDES OF SAID DETECTOR MEANS, SAID PISTON MEANS BEING IN SEPARABLE SECTIONS INCLUDING SECTIONS DISPOSED AT EACH OF THE OPPOSITE ENDS OF SAID CENTRAL HOLE PORTION AND HAVING A PART THEREOF FREELY SLIDABLE WITHIN SAID CENTRAL PORTION, AND ALSO HAVING A DEFORMABLE FLANGE OF GREATEER INITIAL DIAMETER THAN THAT OF SAID CENTRAL PORTION NORMALLY DISPOSED BEYOND THE END OF SAID CENTRAL PORTION, SAID FLANGE BEING RECEIVABLE IN SAID CENTRAL PORTION UNDER A FORCE REPRESENTING A PREDETERMINED PRESSURE DIFFERENTIAL AT OPPOSITE ENDS OF SAID HOLE; AND BARRIER MEANS INSERTABLE IN SAID BLOCK AFTER SAID PISTON MEANS SECTIONS TO LIMIT THE MOVEMENT THEREOF IN SAID HOLE.