BRIEF DESCRIPTION OF THE DRAWINGS
The drawings show:
FIG. 1 a longitudinal cross-sectional view of an electrical hand-held power tool;
FIG. 2 a longitudinal cross-sectional view at an increased, in comparison with FIG. 1, scale of a detail II in FIG. 1; and
FIG. 3 a perspective view of barrier means.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
An electrical hand-held tool 1, which is shown in FIG. 1, includes an outer housing 3, a working tool-side assembly 2 in form of a percussion mechanism assembly that is supported in the outer hosing 3 for a limited axial displacement therein and that imparts blows along a rotational axis A, and an inner cooling fan 4 in form of a centrifugal blower located in a cooling air conduit. The cooling air conduit 5 extends between the working tool-side end of the working tool-side assembly 2 at which a chuck 6 is secured, and the cooling fan 4. At the fan side, the cooling air conduit 5 includes barrier means 7. A small portion of a cooling air 9 which is aspirated by the cooling fan 4 through the outer housing 3 and a substantial portion of which, after cooling an electric motor 8, is blown out, enters, through the barrier means 7, the tubular cooling air conduit 5, an air-tight annular space 10, and openings 11 of a guide tube 12 into the antechamber of a die 13 axially displaceable, within limits, in a guide tube 12 and, finally, the chuck 6 that releases this portion of the cooling air 9 again into the atmosphere.
As shown in detailed view in FIG. 2, the barrier means 7, with a barrier opening 14 that opens radially inwardly toward the rotatable cooling fan 4, provides for an increase of the air flow of the cooling air 9 that flows through the cooling fan 9. To this end, the barrier means 7 is arranged adjacent to the cooling fan 7 at a radial distance therefrom which is so selected that a sealing clearance 15 between the radially outer edge of the cooling fan 4 and the barrier opening 14 is substantially smaller than the opening width of the slot-shaped barrier opening 14, i.e., smaller than the slot width 16. The longitudinal extension of the barrier opening 14 runs transverse (here perpendicular to the plane of the drawing) to a dust-tightness gradient 17 within a curved flow cross-section and is arranged within a flow cross-sectional region with a lower dust-tightness (here in the upper part of the drawing). The longitudinal edges 18 of the barrier opening 14, which are located in the flow cross-section, are formed so that they are sharp-edged in the direction opposite the flow direction.
FIG. 3 shows that with the barrier means 7 being located in the plane of a centrifugal blower, the longitudinal edges 18 of the barrier opening 14 have a shape of an arc segment. At that, the common cross-section 19 of both tubular cooling air conduits 5 is greater than the slot-shaped barrier opening 14.
Though the present invention was shown and described with references to the preferred embodiment, such is merely illustrative of the present invention and is not to be construed as a limitation thereof and various modifications of the present invention will be apparent to those skilled in the art. It is therefore not intended that the present invention be limited to the disclosed embodiment or details thereof, and the present invention includes all variations and/or alternative embodiments within the spirit and scope of the present invention as defined by the appended claims.
Patent Application
20070237591
