Safety seal for pressurized system

Claim 1

Safety means for a pressurized material dispensing system, having an inlet member for addition of dispensable material to the dispensing system, and a closure member sealingly seated on the inlet member, characterized in that pressure dependent means, exposed to interior pressure of the pressurized system and inaccessible from outside the pressurized system when the closure member is seated on the inlet member, prevents unseating of the closure member from the inlet member, when the system is in a state of pressurization above a pre-determined level; and wherein depressurization of the system to the pre-determined level deactivates the pressure dependent means whereby the closure member may be unseated from the inlet member for the introduction of additional dispensable material, wherein (i) the closure member is seated on the inlet member with a rotary engagement and with an interface being formed therebetween, and wherein the pressure dependent means comprises a resilient element positioned adjacent the interface between the closure and inlet members and in the path of a pressure outlet to the exterior of the system; whereby under internal pressurization, above the pre-determined level, the resilient element is urged, by a pressure differential between the interior and exterior of the system, against surfaces of both the inlet and closure members across the interface therebetween, whereby the resilient element seals the pressure outlet, preventing unwanted depressurization of the system, and simultaneously locks the inlet and closure members into a substantially fixed relative position; and wherein de-pressurization below the pre-determined level causes the resilient element to relax away from locking the inlet and closure members whereby the closure member can be unseated; (ii) the resilient element locks the inlet and closure members into the substantially fixed relative position by a combination of compressive and frictional forces supported by the interior pressure of the system above the pre-determined level; (iii) the closure member is unseated from the inlet member in an axial movement direction relative to the rotary engagement, and wherein the resilient element moves to a position whereby it impedes the axial movement, at internal pressurization above the pre-determined level; (iv) at least one of the surfaces of the closure and inlet members, against which the resilient member is urged, is roughened to enhance the frictional forces; (v) the closure member comprises a plug having external threads adapted to be threadingly engaged with internal threads of the inlet member for the sealing seating and rotary engagement and wherein the closure member has a central hollow therein, characterized in that the central hollow extends beyond the area of threaded engagement between the threads of the inlet and closure members, relative to the interior of the pressurized system, with walls of the extended portion of the central hollow being apertured with a plurality of pressure outlet vents extending therethrough; the closure member further having a circumferential groove on its exterior wall, with the circumferential groove being aligned with the outer ends of the pressure outlet vents; wherein the resilient element comprises a resilient band adapted to be seated and substantially completely retained within the circumferential groove, whereby under the internal pressurization above a pre-determined level, the resilient band is urged out of the circumferential groove into frictional engagement against surfaces of the inlet and closure members to provide the locking in the substantially fixed relative position.