Ball seal for thermal sensor assembly of thermostatic expansion valve

A thermal sensor assembly for a thermostatic expansion valve, the thermal sensor assembly comprising:

• an enclosure forming an enclosed interior space containing a thermal sensing fluid, the bulb having a charge opening configured for charging the thermal sensing fluid into the enclosure;
• and
• a ball arranged in the charge opening and forming a seal that fluidly seals the thermal sensing fluid in the enclosed interior space of the enclosure;
• wherein the charge opening includes a tapered lead-in hole formed by a portion of the enclosure, the lead-in hole including a tapered surface that tapers radially inwardly as the tapered surface extends toward the enclosed interior space, the tapered surface sealingly engaging against the ball to form the seal,
• wherein a sealing interface of the ball forming a fluid seal between the enclosure at the charge opening and the ball is formed by a first material and a sealing surface layer located between a surface of the charge opening and the sealing interface is formed by a second material having a greater softness than the first material such that the sealing surface layer conforms to the sealing interface,
• wherein the sealing interface is formed by an outer surface of the ball, such that the sealing surface layer at the charge opening conforms to the outer surface of the ball, and
• wherein the enclosure includes a third material as a substrate layer for the sealing surface layer, the third material of the substrate layer being harder than the second material of the sealing surface layer to enhance a strength of the enclosure.

A thermal sensor assembly for a thermostatic expansion valve, the thermal sensor assembly comprising:

• an enclosure forming an enclosed interior space containing a thermal sensing fluid, the enclosure having a charge opening configured for charging the thermal sensing fluid into the enclosure;
• a ball arranged in the charge opening and forming a seal that fluidly seals the thermal sensing fluid in the enclosed interior space of the enclosure;
• and
• a cover attached to an exterior surface of the enclosure and configured to hold the ball in the charge opening to form the seal;
• wherein the cover is formed as a flat disc, and wherein the ball is sized to fit and seal in the charge opening such that the ball does not protrude beyond a flat of the disc.