Pumps and pump-heads comprising internal pressure-absorbing member

1. 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.

2. The pump of claim 1 , wherein the pressure-absorbing member further exhibits a volumetric expansion when subjected to a pressure decrease, in the liquid contacting the pressure-absorbing member, accompanying melting of the aqueous liquid in the pump housing.

3. The pump of claim 1 , wherein the movable pumping member comprises a rotatable pumping member.

4. The pump of claim 3 , wherein the rotatable pumping member comprises at least one gear.

5. The pump of claim 1 , wherein the movable pumping member comprises at least one piston.

6. The pump of claim 1 , wherein the at least one pressure-absorbing member comprises a unit of a closed-cell foam material.

7. The pump of claim 1 , further comprising at least one interior non-wearing location in the magnet cup, wherein the pressure-absorbing member is located at the non-wearing location.

8. The pump of claim 1 , further comprising at least one sensor in fluid communication with the liquid in the pump housing, wherein the at least one pressure-absorbing member is situated, in the pump housing, adjacent the sensor and in fluid communication with the liquid in the pump housing.

9. A gear pump-head, comprising:

a pump housing defining a gear cavity, at least one inlet hydraulically coupled to the gear cavity, at least one outlet hydraulically coupled to the gear cavity, and a cup-housing in hydraulic communication with the gear cavity, the pump housing being substantially primed with an aqueous liquid, and the cup-housing including at least one interior non-wearing location that contacts the aqueous liquid in the pump housing;

at least a driving gear and a driven gear enmeshed with each other in the gear cavity;

a permanent magnet situated in the cup-housing and being coupled to the driving gear in the gear cavity;

a magnet driver located outside the cup-housing and being magnetically coupled through the cup-housing to the magnet to rotate the magnet in the cup-housing and thus rotate the gears in the gear cavity; and

a first pressure-absorbing member located inside the cup-housing at the non-wearing location and contacting the aqueous liquid, the first pressure-absorbing member having a high-pressure compliant property so as to exhibit a volumetric compression when subjected to a relatively high pressure accompanying freeze-expansion of the aqueous liquid contacting the pressure-absorbing member while not exhibiting volumetric compression when subjected to a pressure increase less than the relatively high pressure, the volumetric compression being sufficient to offset at least a portion of the freeze-expansion sufficient to prevent the freeze-expansion from damaging the pump housing.

10. The gear pump-head of claim 9 , further comprising:

at least one sensor in fluid communication with the aqueous liquid in the pump housing; and

a second pressure-absorbing member situated, in the pump housing, adjacent the sensor.

11. The gear pump-head of claim 9 , wherein the first pressure-absorbing member is a unit of a closed-cell foam material.

12. A hydraulic circuit, comprising:

a pump;

a source of aqueous liquid hydraulically connected upstream of the pump; and

a liquid-discharge port hydraulically connected downstream of the pump;

the pump comprising (a) 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; (b) 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; (c) 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; (d) 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 (e) 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.

13. The hydraulic circuit of claim 12 , wherein the pump is a gear pump.

14. The hydraulic circuit of claim 12 , wherein the pump is a piston pump.

15. The hydraulic circuit of claim 12 , further comprising at least one sensor coupled to the pump housing and sufficiently near the pressure-absorbing member to experience hydraulic pressure experienced by the pressure-absorbing member.

16. A magnetically driven pump-head, comprising:

permanent-magnet means;

pump-member means;

housing means defining pump-cavity means, for enclosing said pump-member means, and magnet-enclosure means for enclosing said permanent-magnet means, said housing means including inlet means and outlet means, the inlet means being for introducing an aqueous liquid to the pump cavity;

said pump-member means being movable in and relative to said pump-cavity means for urging flow of the aqueous liquid, introduced by the inlet means, through said pump-cavity means substantially primed with the aqueous liquid, the outlet means being for conducting aqueous liquid, urged by motion of the pump-member means, from said pump-cavity means;

said permanent-magnet means being rotatable, when urged by a corresponding moving magnetic field produced outside said housing means, in said magnet-enclosure means and being coupled to said pump-member means to cause said pump-member means to cause said pump-member means to urge flow of the aqueous liquid through said housing means from said inlet means to said outlet means; and

pressure-absorbing means, located at a non-wearing surface in said magnet-enclosure means so as to be contacted by the aqueous liquid, for attenuating a relatively high-magnitude pressure change of the aqueous liquid in said housing means accompanying freeze of the aqueous liquid in said housing means while not attenuating pressure changes of relatively low magnitude compared to the relatively high magnitude.

17. The pump-head of claim 16 , wherein said pressure-absorbing means comprises compliant member means configured at least to compress upon experiencing a pressure increase, without experiencing significant saturation by the liquid.

18. The pump-head of claim 17 , wherein said compliant member means is further configured to expand upon experiencing a pressure decrease, without experiencing significant saturation by the liquid.

19. The pump-head of claim 16 , wherein said pump-member means comprises a driving gear and a driven gear meshed with the driving gear.

20. The pump-head of claim 16 , further comprising driving means for imparting motion of the pump-member means in the pump cavity means.

21. The pump-head of claim 20 , further comprising external stator means for producing the moving magnetic field.