Translating cavity valve

1. A valve assembly, comprising:

a valve body comprising a flow bore extending along a flow bore axis and an opening extending through the valve body along a longitudinal axis that is substantially perpendicular to the flow bore axis;

a valve member arranged within the opening, the valve member being movable, along the longitudinal axis, between an open position and a closed position;

an upper seal positioned within a top seal orifice formed in the valve member, the upper seal positioned to seal against at least a first portion of the valve body; and

a lower seal positioned within a bottom seal orifice formed in the valve member, the lower seal positioned to seal against at least a second portion of the valve body, wherein both the upper seal and the lower seal travel with the valve member as the valve member moves between the open position and the closed position, the upper seal and the lower seal defining a cavity that maintains a substantially constant volume throughout movement of the valve member; and

a first valve seat and a second valve seat disposed adjacent to the flow bore and configured to engage the valve member.

2. The valve assembly of claim 1 , wherein the lower seal has a range of travel that is axially lower than a vertical position of the first valve seat.

3. The valve assembly of claim 1 , wherein the upper seal has a range of travel that is axially higher than a vertical position of the second valve seat.

4. The valve assembly of claim 1 , wherein the valve member is oblong shaped.

5. A valve assembly, comprising:

a valve body comprising a flow bore extending along a flow bore axis and an opening extending through the valve body along a longitudinal axis that is substantially perpendicular to the flow bore;

a valve member positioned within the opening, the valve member being movable between an open position that aligns a flow passage with the flow bore and a closed position that aligns a block with the flow bore;

a cavity defined by an upper seal of the valve member and a lower seal of the valve member, the cavity being translatable along the longitudinal axis in response to movement of the valve, the upper seal and the lower seal each engaging the valve body to block fluid ingress into the opening; and

a first valve seat and a second valve seat disposed adjacent to the flow bore and configured to engage the valve member.

6. The valve assembly of claim 5 , wherein a cavity volume is substantially constant throughout movement of the valve member.

7. The valve assembly of claim 5 , wherein the upper seal is arranged within a top seal orifice formed in the valve member and the lower seal is arranged within a bottom seal orifice formed in the valve member.

8. A method for forming a translating cavity valve, comprising:

providing a valve body having an opening that intersects a flow bore;

providing a valve member, the valve member having an upper seal and a lower seal arranged at opposing ends of the valve member, a flow passage being between the upper seal and the lower seal;

arranging the valve member within the opening;

engaging the valve body with the upper seal and the lower seal to from a cavity; and

arranging a first valve seat and a second valve seat such that said valve seats are adjacent to the flow bore and configured to engage the valve member.

9. The method of claim 8 , further comprising:

forming a top seal orifice in the valve member, the top seal orifice receiving the upper seal; and

forming a bottom seal orifice in the valve member, the bottom seal orifice receiving the lower seal.

10. The method of claim 8 , wherein the cavity moves along with the valve member as the valve member moves between an open position and a closed position.