Exhaust muffler filter

Claim 1

AN EXHAUST MUFFLER FILTER FOR INTERNAL COMBUSTION ENGINES COMPRISING, OPEN-ENDED INNER AND OUTER METAL SHELLS IN SUBSTANTIALLY CONCENTRIC RELATION, SAID SHELL BEING RADIALLY SPACED WITH A LONGITUDINAL PASSAGE THEREBYTWEEN, THE OUTER SHELL BEIN SUBSTANTIALLY IMPERFORATE AND THE INNER SHELL EING PERFORATE, END WALLS IN SAID OUTER SHELL TO CLOSE THE ENDS THEREOF, THE INNER SHELL BEING SHORTER IN LENGTH THAN THE OUTER SHELL WITH THE ENDS OF THE INNER SHELL ADJACENT TO AND SPACED FROM THE END WALLS, AN INLET DUCT EXTENDING THROUGH ONE END WALL AND AN OUTLET DUCT EXTENDING THROUGH THE OTHER END WALL, MEANS ON INNER ENDS OF THE INLET AND OUTLET DUCTS SUPPORTING THE INNER SHELL, A FIBROUS FILTER MEDIA FILLING SAID INNER SHELL BETWEEN SAID INLET AND OUTLET DUCTS WHEREBY EXHAUST GASES MOVING FROM THE INLET DUCT TO THE OUTLET DUCT NORMALLY PASS THROUGH SAID FILTER MEDIA, SAID INLET AND OUTLET DUCTS HAVING APERTURES THEREIN BETWEEN THE ENDS OF THE INNER SHELL AND THE END WALLS OF THE OUTER SHELL, AND VALVE MEMBERS ON THE INLET DUCT FOR SAID APERTURES THEREIN AND BIASED INTO APERTURE CLOSING POSITION FOR NORMALLY CLOSING SAID APERTURES AGAINST NORMAL OPERATING PRESSURES IN THE INLET DUCT, SAID VALVE MEMBERS BEING OPENED IN RESPONSE TO INCREASE OF PRESSURE IN THE INLET DUCTS RESULTING FROM INCREASE OF RESISTANCE TO FLOW THROUGH THE FILTER MEDIA AND THEREBY PERMITTING FLOW OF EXHAUST FROM THE INLET DUCT THROUGH THE PASSAGE BETWEEN THE INNER AND OUTER SHELLS TO THE OUTLET DUCT BYPASSING THE FILTER MEDIA IN THE INNER SHELL.