Spacer bead geometry for controlled sealing stability

摘要

A shaped bead structure provides a bottom sealing periphery adjacent a non-bonding portion which may include an upper portion which may provide upper envelope stability and may but will preferably not bond to the glass envelope. The provision of a section of the glass envelope free of bonding above the lower peripheral sealing provides a leveraged stability to the upper portion of the glass envelope, and provides an annular space to prevent vertical spreading of a wetted glass envelope sealing zone with respect to a significant length of the glass envelope leaving it in tact and enabling it to “break” any vertically extending wetted interface and thus disrupt distortion forces. The use of two or more structures to provide a significant annular area of non-contact with the annular envelope can help to provide a structure which is not complex and easy to manufacture. Where two of the bead sections are stacked with the portions which are displaced significantly peripherally inwardly adjacent each other, an annular space is formed.