Abstract: An air pump apparatus having a cylinder extending from a pump casing. The cylinder comprises a cylinder liner positioned within the walls of the cylinder and a piston is mounted for reciprocating movement within the cylinder liner. The pump chamber is formed between the front of the piston and the front portion of the cylinder wherein an annular gap is formed between the piston and the inner wall of the cylinder liner, wherein the piston has a plurality of annular grooves formed on the outer circumferential surface thereof, the annular gap and annular grooves forming a labyrinth path extending from the pump chamber.

Abstract: A sonic nozzle apparatus in a carburetor flow testing machine comprising a measuring pipe passage connecting a carburetor to be tested and a pressure source such as a vacuum pump or the like, the measuring pipe passage being provided at an intermediate portion with a cutout section in which a tubular nozzle chamber can be selectively introduced in sealed relation. A plurality of such tubular nozzle chambers are mounted on a turntable to be selectively introduced into the cutout and each nozzle chamber contains a respective sonic nozzle therein. The nozzle chambers are disposed circumferentially at regular intervals and the turntable is intermittently turnable on a support shaft disposed on one side of the measuring pipe passage. One of the mutually opposite surfaces of an upstream and a downstream portion of the measuring pipe passage divided by the cutout is constituted as a piston which is movable by a pressure fluid to selectively effect clamping or release of the nozzle chamber when aligned in the cutout.