Power brush

Abstract

A power-brush apparatus has a housing and a brush rotatable on the housing about a brush axis and having bristles extending generally radially of the axis and having tips defining on rotation of the brush a circular orbit centered on the axis. The tips are engageable at a location with a workpiece surface. In accordance with the invention a blocking element is positioned radially inside the orbit immediately upstream from the location in a normal rotation direction of the brush. A drive rotates the brush in a working direction about the axis relative to the housing at a predetermined angular speed in the direction and thereby orbits the tips of the bristles about the axis such that the bristles engage the blocking element, are slowed thereby, and when released thereby snap back to accelerate forward and strike the workpiece at an augmented speed.

Claims

1. A power-brush apparatus comprising: a housing; a brush rotatable on the housing about a brush axis in a working direction and having bristles made of steel wire, extending generally radially of the axis, and having tips defining on rotation of the brush a circular orbit centered on the axis, the tips being engageable at a location with a workpiece surface and each being bent forward relative to the respective bristle in the working direction; a blocking element fixed relative to the housing and positioned radially inside the orbit immediately upstream between 25 and 45 relative to the axis and to the working direction of the brush from the location; and drive means for rotating the brush in a working direction about the axis relative to the housing at a predetermined angular speed in the direction and thereby orbiting the tips of the bristles about the axis such that the bristles engage the blocking element, are slowed thereby, and when released thereby snap back to engage the workpiece surface at a greater peripheral speed than the angular speed with the bent-forward bristle tips striking and hammering the workpiece surface generally perpendicularly at the location.

2. The power-brush apparatus defined in claim 1 wherein the blocking element is fixed on the housing.

3. The power-brush apparatus defined in claim 2 wherein the blocking element has a radial outermost edge generally lying on the orbit.

4. The power-brush apparatus defined in claim 1 wherein the brush comprises a core sleeve from which the bristles extend.

5. The power-brush apparatus defined in claim 4, further comprising: a pair of axially spaced holder disks flanking the core sleeve, rotatable about the axis on the housing, and connected to the drive means.

6. The power-brush apparatus defined in claim 1 wherein the bristles are provided at density of at most 16 bristles per cm.sup.2.

7. A method of abrading a workpiece, the method comprising the steps of: rotating a brush on a housing about an axis in a direction at a predetermined angular speed such that bent-forward tips of bristles made of steel wire extending generally radially of the axis define a circular orbit centered on the axis; engaging the tips radially at a location with a workpiece surface to abrade the surface at the location; and positioning a blocking element fixedly relative to the housing and radially inside the orbit upstream 25 to 45 relative to the axis and to the direction from the location and thereby temporarily slowing angular movement of the bristle tips such that when released they snap back to engage the workpiece surface at a greater peripheral speed than the angular speed and with the tips striking and hammering the workpiece surface generally perpendicularly at the location.

Description

BRIEF DESCRIPTION OF THE DRAWING

(1) The above and other objects, features, and advantages will become more readily apparent from the following description, reference being made to the accompanying drawing in which:

(2) FIG. 1 is a perspective view of the power-brush apparatus according to the invention;

(3) FIG. 2 is a largely schematic side view of the power brush;

(4) FIG. 3 is another side view;

(5) FIG. 4 is an exploded sectional end view of the brush assembly; and

(6) FIG. 4A is a large-scale view of the detail indicated at IVA in FIG. 4.

SPECIFIC DESCRIPTION

(7) As seen in FIG. 1, a power brush has a housing 1 and a drive motor 2 for a brush 3 comprised of a core sleeve 4 centered on an axis 6 and provided with radially projecting bristles 5. During normal operation outer tips 5 of the bristles 5 lie on a cylindrical orbit 8 centered on the axis 6, and in fact these tips 5 are bent slightly forward into a rotation direction R. In practice two bristles 5 form part of a U-shaped steel wire that fits through a pair of radially throughgoing holes 7 (FIG. 4A) in the sleeve 4. Here the bristles 3 are formed into three angularly equispaced groups separated by gaps 9 with no bristles 5. They are provided a density of 14 to 16 bristles/cm.sup.2.

(8) The circular brush 3 is supported in the housing by a brush holder comprised of two axially spaced disks 10 flanking a cylindrical core sleeve 11 (see FIG. 4). The disks 10 have axially extending tabs or webs 12 that fit into the gaps 9 so as to ensure good rotational coupling of the brush 3 to the disks 10. The disk 10 and core 11 forming the holder are carried on a shaft 13 defining the axis 6 and coupled by unillustrated means to the drive motor 2 for rotation in the direction R. The spacer sleeve 11 is not needed when the core 4 of the brush 3 is stiff enough.

(9) According to the invention a blocking element 14 is provided in the path of the bristles 5, that is radially inward of the orbit 8 and outward of the axis 6. Here the blocking element 14 is a cylindrical rod extending parallel to the axis 6 and carried on the outer end of an arm or bracket 15 secured on the machine housing 1 of the power brush. The length of the blocking element 14 is such that it substantially corresponds to the width or axial dimension of the brush core 4, so that the blocking element 14 does not stick axially past the circular brush 3.

(10) The blocking element 14 is disposed stationary relative to the rotating circular brush 3 but can for example be adjusted radially thus dip into the bristles 5 within the bristle ring 8 or emerge therefrom. Furthermore, the blocking element 14 can of course also be adjusted axially, which however is not represented. Moreover, the blocking element 14 can be provided with unillustrated cooling means.

(11) It can be seen that the blocking element 14 projects radially into the bristle ring 8 so far that an outer surface 16 of the blocking element 14 and an outer surface 17 of the bristle ring 8 approximately coincide. A protective cap or shield 18 extends radially outward past the orbit 8 over around 270 of the orbit 8, leaving a portion exposed for contacting the bristles 5 with the workpiece 19. The blocking element 14 is in this gap in the shield 18. Thus there is no need to modify the standard machine housing 1 to retrofit it with the blocking element 14 of this invention. The blocking element 14 is spaced upstream, (relative to rotation direction R) from the region of contact of the bristles 5 with the workpiece 19 by an angle , which here is between 30 and 40. Of course the blocking element 14 can also be a part of the machine housing 1 or of the protective cap 18 of the power brush.

(12) With the system of this invention the bristles 5 not only work the surface of the material 19 by scratching the tips 5 across the workpiece purely at the angular speed they assume as the result of rotation of the brush 3 about the axis 6. This effect is achieved in that the blocking element 14 engages the bristles 5 somewhat before they would normally strike the workpiece and bends them elastically back through an angle to a line N extending radially of the axis 6, then releases them so that they spring axially forward through an arc 20, which is not concentric with the circle 8, with their tips 5 moving at a speed that is equal to the speed at which they spring elastically back added to the rotation speed of the brush 3. The bristle tips 5 are therefore moving at a higher speed than the angular speed they would have over a short arc as they engage the workpiece. Thus, in effect a higher brush speed is achieved at only the critical area where the brush engages the workpiece 19, not around the entire periphery of the brush 3. The bristles 5 therefore work like tiny hammers when they strike the workpiece 19.

(13) The bristles 5 freed from the blocking element 14 form a right angle at a contact point 21 with the surface of the workpiece 19, which is a surface extending tangentially to the outer surface 17 of the bristle ring 8. Since the circular arc 20 along which by the bristle tips 5 move when released by the blocking element 14 is different from the outer surface 17 of the bristle ring, the angle which is enclosed between the arc of a circle 20 and the normal line N is less than 90. As a consequence, the bristle tips 5 meet the surface of the material 19 almost perpendicular in the region of the contact point 21 or respectively the related contact surface and moreover dispose of a speed component which is perpendicular to the surface of the material 19, as shown in FIGS. 2 and 3. After the bristles 5 come off the workpiece 19, they assume a position generally lying on respective radii to the axis 6.

(14) The blocking element 14 shows the speed of the bristles briefly. After their release, the kinetic energy which has been stored due to this speed reduction in the circular brush 3 is released during a considerably shorter time interval and is used for the additional striking treatment of the surface of the material 19 by the bristles 5. Indeed, this kinetic energy is stored primarily in the brush strip 4, since it deviates from the cylindrical trajectory, as is in particular seen in the FIG. 3, where this deviation is marked with the reference number 22.