Patent ID: 8323008

Claim:
A pump for pumping an aqueous liquid, comprising: a pump housing defining a pump cavity, at least one inlet, at least one outlet, and a magnet cup, the pump housing contacting aqueous liquid in the pump housing whenever the pump housing is substantially primed with the liquid; a movable pumping member situated in the pump cavity, the pumping member, when driven to move, urging flow of the aqueous liquid from the inlet through the pump cavity and magnet cup to the outlet; a permanent magnet situated in the magnet cup, the magnet being rotatable in the magnet cup and being coupled to the movable pumping member in the pump housing; a magnet driver located outside the magnet cup, the magnet driver being magnetically coupled through the magnet cup to the magnet to rotate the magnet in the magnet cup and thus move the pumping member in the pump cavity; and at least one pressure-absorbing member located inside the magnet cup, the pressure-absorbing member contacting the aqueous liquid and having a high-pressure compliant property so as to exhibit a volumetric compression when subjected to a pressure increase having a relatively high magnitude resulting from freeze-expansion of the aqueous liquid in the pump housing while not exhibiting volumetric compression when subjected to pressure increases having magnitude less than the relatively high magnitude, the volumetric compression occurring during freeze-expansion being sufficient to alleviate the relatively high-magnitude pressure increase and prevent freeze-damage to the pump housing.