Patent ID: 7849875

Claim:
A surgical handpiece used to perform liquefaction during a cataract procedure, comprising: a hollow housing having a stem valve seat; a stopper configured to reciprocate within the hollow housing, the stopper comprising: a piston head, an extended stem coupled to the piston head; and a spring extending along the stem to engage the piston head to bias the piston head away from the stem valve seat so as to form a gap between the stem valve seat and the stem when a first pressure on the piston head provides an opposing force on the piston head that is less than a force provided on the piston head by the spring; wherein when a second pressure of pressurized pulses of heated fluid on the piston head provides an opposing force on the piston head that is greater than the force provided on the piston head by the spring, a length of the stem prevents flow of the pressurized pulses of heated fluid flowing along the stem from flowing past the stem valve seat before the stem seals against the stem valve seat; wherein an end of the stem that seals against the valve seat is rounded; wherein at least part of the rounded end of the stem is configured to extend past the stem valve seat when the piston head is biased against a side of the valve opposite the stem valve seat by the spring during the first pressure.