| CPC B63G 8/22 (2013.01) [F04B 19/22 (2013.01); F04B 23/06 (2013.01)] | 25 Claims |

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1. A pump including:
a. a pump body;
b. at least one inlet;
c. at least one outlet;
d. a fluid path between the at least one inlet and the at least one outlet;
e. at least one piston arrangement disposed in the fluid path and configured to pump fluid from the at least one inlet through the fluid path to the at least one outlet, the at least one piston arrangement including:
i. a piston chamber;
ii. an inlet valve;
iii. an outlet valve;
iv. a piston disposed to move within the piston chamber, the piston including a first outer end surface at a first end of the piston and a second outer end surface at a second end of the piston;
v. a piston drive for driving the piston within the piston chamber, the piston drive operatively attached to the first end of the piston;
f. wherein at least one of the first outer end surface and the second outer end surface of the piston are exposed to an ambient pressure; and
g. wherein a surface area of the first outer end surface is smaller than a surface area of the second outer end surface such that an ambient pressure force on the second end is greater than an ambient pressure force on the first end.
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