Abstract: An MWE compressor comprising a housing defining an inlet and an outlet, and an impeller wheel rotatably mounted in the housing such that on rotation of the wheel gas within the inlet is moved to the outlet. The housing has an inner wall defining a surface located in close proximity to radially outer edges of vanes supported by the wheel. The inlet is defined by a first tubular portion an inner surface of which is an extension of the said surface of the inner wall of the housing, a second tubular portion located radially outside the first portion to define an annular passage between the first and second portions, a wall extending across the annular passage between the first and second portions, and a conical wall located upstream of the first portion and extending in the radially outwards and upstream directions from adjacent the upstream end of the first portion to the upstream end of the second portion.

Abstract: There is disclosed a valve assembly and a reciprocating type fluid pump having a piston cylinder and a cylinder head together which define a fluid chamber. A first ring valve having a seal surface on one side is disposed within the fluid chamber adjacent to the cylinder head to close at least one fluid intake passage. A bias means is provided for urging the first ring valve against the seat on the head by abutting the ring valve on the side opposite from the seal surface, and the bias means includes a peripheral region which is connected to the fluid pump and retains the first ring valve between the cylinder head and the bias means.