X-ray unit with time delay means to prevent actuation thereof until explosive air is purged from the housing

Claim 1

AN EXPLOSION-SAFE MOBILE X-RAY UNIT COMPRISING A HOUSING FOR LOCATION IN AN AREA IN WHICH THE SURROUNDING AIR MAY BE POTENTIALLY EXPOLSIVE, SPARK-PRODUCIBLE ELECTRICAL COMPONENTS DISPOSED IN SAID HOUSING, SAID HOUSING HAVING AIR VENTS THEREIN AND AN AIR INLET FOR ADMISSION OF EXPLOSION-SAFE AIR INTO SAID HOUSING FOR CIRCULATION THERETHROUGH TO SURROUND SAID SPARK-PRODUCIBLE ELECTRICAL COMPONENTS WITH SUCH AIR, AND SAFETY-PRODUCIBLE ELECTRICAL COMING PRESSURE RESPONSIVE MEANS AND TIME DELAY MEANS CONSTRUCTED AND ARRANGED TO ASSURE DE-ENERGIZATION OF SAID ELECTRICAL COMPONENTS UNLESS AIR PRESSURE WITHIN SAID HOUSIING IS GREATER THAN THAT AT THE EXTERIOR OF THE HOUSING AND UNTIL SUCH RELATIVELY-POSITIVE INTERNAL AIR PRESSURE HAS PERSISTED FOR A PERIOD OF TIME SUFFICIENT TO PURGE SAID HOUSING OF ANY POTENTIALLY EXPLOSIVE AIR.