Engine block heater assembly

Claim 1

AN ENGINE BLOCK HEATER ADAPTED TO BE MOUNTED WITHIN A FROST PLUG OPENING IN AN ENGINE BLOCK WALL, SAID HEATER COMPRISING A PLUG BODY OF WHICH A PART THEREOF IS SHAPED AND SIZED TO FIT SNUGLY IN SAID OPENING, STOP MEANS CARRIED BY SAID BODY TO PREVENT SAID PLUG BODY FROM PASSING COMPLETELY THROUGH SAID OPENING, SEALING MEANS CARRIED BY SAID PLUG BODY TO EFFECT A FLUID-TIGHT SEAL BETWEEN SAID PLUG BODY AND SAID ENGINE BLOCK WALL, AN ELECTRICAL HEATING ELEMENT CARRIED BY THE PLUG BODY AT THE OPPOSITE END FROM SAID STOP MEANS WHEREBY SAID HEATING ELEMENT IS POSITIONED WITHIN THE ENGINE BLOCK WHEN SAID BLOCK BODY IS MOUNTED IN SAID OPENING, TERMINAL MEANS ELECTRICALLY CONNECTED WITH SAID ENGINE BLOCK AND ACCESSIBLE FROM THE OUTSIDE OF SAID ENGINE BLOCK WHEREBY ELECTRICAL CONNECTION WITH AN OUTSIDE SOURCE OF ELECTRICAL POWER CAN BE EFFECTED, AND LOCKING MEANS CARRIED BY SAID PLUG BODY FOR RELEASABLY LOCKING SAID HEATER WITHIN SAID OPENING, SAID LOCKING MEANS COMPRISING AN EXPANSIBLE RING HAVING A DIAMETER IN ITS UNEXPANDED CONDITION WHICH IS LESS THAN THE DIAMETER OF SAID OPENING, RING CARRYING MEANS CARRIED BY SAID PLUG BODY AND EXTENDING INWARDLY OF SAID OPENING, SAID RING BEING SLIDABLY MOUNTED ON SAID RING CARRYING MEANS WITH THE AXIS OF SAID RING BEING CO-EXTENSIVE WITH THE AXIS OF SAID PLUG BODY, SAID RING CARRYING MEANS HAVING OUTER SURFACES WHICH ARE OUTWARDLY DIVERGENT TOWARDS SAID PLUG BODY, AND MEANS CARRIED BY SAID PLUG BODY AND OPERABLE FROM OUTSIDE SAID ENGINE BLOCK WALL FOR MOVING SAID RING TOWARDS SAID PLUG BODY ALONG SAID DIVERGENT SURFACES, SAID DIVERGENT SURFACES BEING DIMENSIONED TO CAUSE SAID RING TO EXPAND A SUFFICIENT DEGREE TO PREVENT WITHDRAWAL OF THE PLUG BODY FROM SAID OPENING.