This invention is an improvement of the thermal release plug disclosed in copending patent application Ser. No. 727,881 filed Sept. 29, 1976 which was formed under similar conditions but did not utilize a high melting temperature plug member in the well in addition to the low melting temperature metal. Without a plug member the aperture at the bottom of the well had to be kept small because the sealant metal became highly fluid under the production temperatures and as a result could not be retained in the well if the opening were too large. When a large area vent was required a plurality of wells having openings which in the aggregate equaled the required area had to be formed. Attempts to use a high melting point plug sealed in the well by a low melting metal resulted in unreliable release plugs because under the furnace brazing temperature and atmosphere conditions the plug member became bonded directly to the well surface in some instances. The present invention solves this problem by using standoff means in the well to hold a circular plug member away from the well walls except at the points where the standoff means contact the plug member. The remaining peripheral portion of the circular plug not in contact with the standoff means is spaced from the well wall by a gap which is sufficiently narrow to prevent the metal sealant from flowing through the gap during production yet because of its length provides a total area that is comparatively large. Also, if any bonding occurs between the circular plug member and the well it is limited to a minimum number of points and thus does not drastically interfere with the reliable release of the plug.
The invention including the above mentioned features and advantages will be understood best if the written description is read with reference to the accompanying drawings.