Patent ID: 7811070

Claim:
A pneumatic vane motor comprising: a cylinder with a pressure air inlet opening having a closing edge, and an air outlet opening; and a rotor which is eccentrically journalled in the cylinder and which forms a clearance seal relative to the cylinder, wherein the rotor carries a number of sliding vanes that are disposed at equal angular intervals, and that are arranged to be in constant contact with the cylinder during rotation of the rotor and to divide the cylinder into a number of moving cells each confined between a leading vane and a trailing vane; wherein the cylinder is provided with at least one by-pass passage extending in a moving direction of the moving cells; wherein said at least one by-pass passage has an opening edge located mainly in a diametrically opposite position relative to the clearance seal between the rotor and the cylinder; wherein as the leading vane of a pressurized cell passes said opening edge, said at least one by-pass passage provides air drainage communication past the leading vane of the pressurized cell into an adjacent cell located in front of said pressurized cell in the moving direction of the moving cells; and wherein said adjacent cell communicates with the air outlet opening and forms an internal sound attenuating expansion volume for pressure air leaving said pressurized cell.