Pneumatic percussive tool

Claim 1

A pneumatic percussive tool comprising: a cylinder having an upper end portion and a lower end portion; a hammer disposed in said cylinder for reciprocating movement therewithin under the action of compressed air, therewith to impart blows to a working implement received in the front end portion of said cylinder; air-distribution means, said means being connected to a source of compressed air during the operation of the tool, and disposed in the rear end face of the upper end portion of said cylinder for distributing the compressed air provided from the source; a housing fixedly mounted on the rear end portion of said cylinder, for rigidly holding said air-distribution means to said cylinder, at least one portion of the peripheral surface of the front end of said housing having a different diameter, than the other, while the front end face of said front end of said housing is provided with slots; handle means mounted on said housing and axially movable along the outer surface of said housing between a maximum predetermined forward position and a maximum predetermined rearward position, said handle means being provided on the inner surface of the front end part thereof with at least one portion having a diamter which is greater than that of the surface thereof in contact with said housing, and in the wall of the rear end part of that portion with through passages communicating with atmosphere, said handle means being provided for controlling said tool and permitting communication between said air-distribution means and said source upon movement thereof forwardly along the housing towards said maximum predetermined position into the operative position of the tool; a casing mounted on said cylinder forwardly of the housing, the outside diameter of the rear end portion of the casing being substantially equal to the outside diameter of said portion of said housing, said casing defining together with said cylinder and the front end portion of said housing a manifold for collecting the exhaust air; a shock absorber disposed between said housing and said handle for returning said handle towards said maximum predetermined rearward position into the rearmost inoperative position of the tool and reducing vibration of the handle; said portion of the housing having a diameter smaller than that of the surface of said housing mounting said handle; rear end and front end cavities defined by the axial movement of the handle along the housing towards said maximum predetermined forward position into the foremost operating position, the rear end cavity communicating with said manifold through said slots formed in the front end face of said housing and being defined by said portion of the housing, the inner surface of said handle and the outer surface of the rear end portion of said casing, and said front end cavity communicating with its rear end portion through the front end portion of said rear end cavity, as well as with atmosphere through said passages of the handle, Said front end portion also communicating with atmosphere through its open front end portion, which front end portion has a greater crosssectional area than that of said rear end cavity and is defined by said portion of the handle and the outer surface of said casing so that upon entry of the exhaust air from said manifold into said rear end cavity and into said front end cavity communicated therewith and having a greater cross-sectional area the ambient atmospheric air is sucked in through said passages in the handle walls, whereby the speed of air discharge from said front end cavity is reduced thereby lowering the aerodynamic noise.