Noise-attenuating pneumatic compressor and medical apparatus incorporating same

DETAILED DESCRIPTION The present invention addresses these needs by providing a compressor which achieves the sound-attenuating advantages of Helmholtz-type resonators without the size disadvantage typical of these resonators.
One aspect of the present invention provides a compressor consisting of a housing, a cylindrical chamber having an open end connected in communication with an interior of the housing and a closed end, and a piston assembly disposed in the cylindrical chamber and having a piston head dividing the cylindrical chamber into a high pressure side between the piston head and the closed end and a low pressure side between the piston head and the open end.
Drive means are provided to drive the piston assembly reciprocally in the cylindrical chamber between an intake position and an exhaust position.
A suction aperture and a discharge aperture communicate with the high pressure side of the cylindrical chamber, the suction aperture being opened and closed by suction valve means and the discharge aperture being opened and closed by discharge valve means.
The compressor further includes a resonating chamber having an interior defining a predetermined volume.
A flow path is provided between the interior of the resonating chamber and the suction aperture so that movement of the piston assembly from the exhaust position to the intake position draws a volume of air from the interior of the resonating chamber into the high pressure side of the cylindrical chamber.
The discharge aperture of the compressor may be connected to a medical device so that movement of the piston assembly from the intake position to the exhaust position can expel this volume of air toward the medical device.
Port means in the resonating chamber provide an air communication path of a preselected diameter between the interior of the resonating chamber and the exterior thereof.
In accordance with well-known acoustic principles, the large volume of the resonating chamber in relation to the diameter of the air communication path results in an attenuation of the pulsing sounds generated by the inlet side of the compressor