US Patent 8393260 Valve cap

A valve cap for sealing an aperture in a pump; a plugging assembly for a valve cap to seal at an aperture in a pump; a docking unit for use with a plugging assembly for sealing an aperture in a pump; and a method of sealing an aperture in a pump. A valve cap (10) comprises a valve plug (16) including, a first engaging means (40); a compression unit (20) including a plurality of springs (56) to apply a compressive load upon the plug and second engaging means (62, 64); a docking unit (24) for landing on the compression unit, including one or more pistons (92) to apply a compressive load upon said springs and third engaging means (74, 76, 78) to lock said plug to said compression unit and seal said plug against said aperture.