Wax shell imitation candle with improved resistance to cracking
An imitation candle having an exterior wax shell and an interior illumination source is structured to reduce cracking of the exterior wax shell by incorporating a bonding layer into a central cavity in the shell between the interior illumination source and the wax shell. The bonding layer terminates well spaced from terminal edges of the shell to transfer stress between the illumination source and the shell caused by differing coefficients of thermal expansion to points removed from edges of the shell to retard crack genesis.
1. An imitation candle comprising:
a wax shell having an interior central cavity defined by an interior surface of the wax shell;
an insert having a different thermal coefficient of expansion than the wax shell, the insert being positioned in the interior central cavity to leave a gap between the insert and the interior wall of the interior central cavity; and
a wax bonding layer disposed in a portion of the gap between the insert and the interior surface of the wax shell to positionally retain the insert in the wax shell while relieving and redirecting stress stemming from differential expansion and contraction of the insert and the wax shell due to changes in temperature.
2. An imitation candle as set forth in claim 1 , further comprising:
the wax bonding layer being formed from a pour of molten wax into a previously cast and hardened wax shell and placement of the insert into the molten wax to force the molten wax to spread around and conform to the insert between the insert and interior surface before hardening into the bonding layer.
3. An imitation candle as set forth in claim 2 , further comprising:
such portion of the gap not filled by the wax bonding layer being filled with air.
4. An imitation candle as set forth in claim 3 , wherein the interior central cavity and the gap extend into the wax shell from an open end of the wax shell.
5. An imitation candle as set forth in claim 4 , further comprising:
the insert providing a source of artificial illumination.
6. An imitation candle as set forth in claim 3 , further comprising:
a plurality of edges between surfaces of the shell exhibiting substantial angles of intersection being rounded.
7. A process for making an imitation candle comprising the steps of:
casting a shell from molten wax;
forming a central cavity from a bottom surface of the shell into the interior of the shell;
after hardening of the shell making a second pouring of wax into the central cavity with the shell inverted, the second casting comprising a substantially reduced quantity of wax; and
inserting a module into the central cavity with the shell still inverted and the second pour of wax still molten to displace the molten wax of the second pouring to form a bonding layer between the module and the shell upon cooling of the wax, the combined volume of the module and the wax from the second pouring being substantially less than that required to fill the central cavity.
8. The process as claimed in claim 7 , further comprising the step of:
leaving a wax free gap between a portion of the module and the interior surface of the central cavity.