High temperature slip-sealing grommet systems

An apparatus for sealing an end region of an elongate heating cable comprises:

• a housing of rigid material defining at least a first open end region leading to a fully-enclosed interior space, the open end region having a retaining shoulder and an interior wall surface,
• a back shim of rigid material having a back face retained by the retaining shoulder, having a front face forming an anvil surface, and defining a central opening sized to receive therethrough the end region,
• an elastomeric grommet having a flat face confronting the anvil surface, having a generally cone-shaped face axially opposite the flat face, and defining a central opening sized to receive therethrough the end region,
• a front shim of rigid material having a generally cup-shaped grommet-confronting face congruent with and confronting the generally cone-shaped face, having a generally flat spring-engaging face, and defining a central opening for receiving therethrough the end region,
• a compression spring for applying an axial sealing force to the front shim and defining an axial opening enabling the end region to pass therethrough, and,
• a pressure plate of rigid material releasably secured to said housing to close said open end region, the pressure plate including a spring base for the compression spring and defining an axial opening enabling the end region to pass therethrough,
• whereby the pressure plate, when secured to the housing, applies an axial force driving the front shim into the elastomeric grommet, and the axial force along with relative slippage between the generally cup-shaped grommet-confronting face and the generally cone-shaped face, causes the elastomeric grommet to compress and expand radially against the interior wall surface and an adjacent outer surface of the end region and to result in a radial seal against the outer jacket of the heating cable over high temperature operating cycles.

A kit of parts for assembly by a craft worker into a sealing system for sealing an end region of an elongate heating cable received through a central longitudinal opening, the kit of parts comprising:

• an enclosure body of molded plastic material defining at least a first open end region leading to a fully-enclosed interior space for the cable end, and defining a spring force stopping structure and an interior wall surface within the interior surface of said body,
• a pressure plate formed of rigid material releasably securable to the body to cover and close the open end region,
• attachment means for attaching the pressure plate to the open end region of the enclosure body during assembly of the kit to form the system,
• a compression spring for applying a longitudinal compression force along a force path between the pressure plate and the spring force stopping structure,
• a grommet within the force path and formed of elastomeric material having a tendency not to bond to material comprising an outer jacket of the heating cable and having at least one generally cone-shaped face, and
• a structural member within the force path and defining a cup-shaped face congruent with and confronting the generally cone-shaped face of the grommet for transferring the compression force to the generally cone-shaped face upon assembly of the kit to form the system, thereby forming a slip-surface between the member and the grommet and preventing the grommet from becoming bonded over a high temperature operating interval to the inside wall of the body and, when cooled, permitting the grommet to shrink longitudinally by slippage along the slip-surface formed at the cup-shaped surface, thereby maintaining a radial seal against the outer jacket of the electrical cable.