METHOD OF TREATING A WORKPIECE

Abstract

A surface of a workpiece is treated by rotating about an axis a brush having a multiplicity of radially projecting bristles with tips engaging a surface of a workpiece to be treated while positioning a stop nonrotatable with the brush in engagement with the bristles radially inward of the stop so as to rearwardly deflect the bristles prior to contact with the workpiece and thereby store kinetic energy in the bristles so that as the bristles pass the stop the kinetic energy is released and the bristles spring elastically forward and percussively strike the workpiece surface. A roughness of the workpiece surface is determined and the stop is positioned radially relative to the axis or the brush is positioned relative to the workpiece at a spacing in accordance with the determined roughness.

Claims

1. A method of treating a surface of a workpiece using a brush assembly, the method comprising the steps of: rotating about an axis a brush having a multiplicity of radially projecting bristles with tips engaging a surface of a workpiece to be treated; positioning a stop nonrotatable with the brush in engagement with the bristles radially inward of the stop so as to rearwardly deflect the bristles prior to contact with the workpiece and thereby store kinetic energy in the bristles, whereby as the bristles pass the stop the kinetic energy is released and the bristles spring elastically forward and percussively strike the workpiece surface; determining a roughness of the workpiece surface; and positioning the stop radially relative to the axis or the brush relative to the workpiece at a spacing in accordance with the determined roughness.

2. The method according to claim 1, the stop is positioned radially for the most part relative to the axis at a radial spacing that is changed according to the determined roughness.

3. The method according to claim 1 wherein roughness of the surface of the workpiece is detected by contacting and/or contact-free means.

4. The method according to claim 1, wherein the roughness of the processed surface of the workpiece is detected and converted by a controller into actuating movements of the stop and/or of the ring brush depending on a desired roughness profile of the surface.

5. The method according to claim 1, wherein roughness of the surface is determined by scanning the surface of the workpiece in a tactile manner with a stylus and/or in a contactless manner by a sound source and/or a source for electromagnetic waves.

6. The method according to claim 5, wherein the source for electromagnetic waves is a laser that scans the surface of the workpiece.

7. The method according to claim 6, wherein the surface of the workpiece is scanned using a two-dimensional triangulation method.

8. The method according to claim 1, further comprising the step of not only positioning the stop relative to the ring brush, but also displacing the ring brush together with the stop in relation to its radial spacing and/or parallel to the surface of the workpiece.

9. An apparatus for treating a surface of a workpiece, the apparatus comprising: a brush rotatable about an axis and having a multiplicity of radially projecting bristles with tips engageable with a surface of a workpiece to be treated; a stop nonrotatable with the brush and in engagement with the bristles radially inward of the stop so as to rearwardly deflect the bristles prior to contact with the workpiece and thereby store kinetic energy in the bristles, whereby as the bristles pass the stop the kinetic energy is released and the bristles spring elastically forward and percussively strike the workpiece surface; and control means for determining a roughness of the workpiece and positioning the stop radially relative to the axis or the brush relative to the workpiece at a spacing in accordance with the determined roughness.

10. The apparatus according to claim 9, wherein the brush is rotated in a predetermined working direction and the stop is upstream in the direction from a location where the bristle tips strike the workpiece surface.

11. The apparatus according to claim 8, wherein the brush and workpiece are displaced relative to each other in a predetermined direction and roughness is detected by scanning the surface at a location downstream in the predetermined direction from the location where the brush tips engage the surface such that a treated portion of the workpiece is scanned.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0016] 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:

[0017] FIG. 1 is a perspective view of a rotary brush tool together with brush assembly and associated ring brush according to the invention, the latter being driven by the former; and

[0018] FIG. 2 is a schematic side view of the system of FIG. 1.

SPECIFIC DESCRIPTION OF THE INVENTION

[0019] As seen in FIG. 1 a rotary brush tool has a part-cylindrical frame 1 that can fit around a workpiece 2 to be processed. According to this embodiment, and without limitation thereto, the workpiece 2 is a pipe or conduit made of individual pipes that are butted and welded together. The pipes are connected to one other by a butt weld 3 visible in FIG. 1. In the exemplary case, in order to protect the weld seam 3 and, in general, the region of the interconnection of the pipes from corrosion, the surface of the workpiece 2 in the vicinity of the weld seam 3 is processed by the rotary brush tool described in detail below. Subsequent to this treating, a protective coating can be applied to the pipe or workpiece 2 in this region.

[0020] As will readily be understood, the rotary brush tool to be described in greater detail below is not only suitable for treating surfaces on curved workpieces 2 such as the pipe or conduit shown in FIG. 1. Rather, the rotary brush tool can be used just as well for treating a flat workpiece surface, although this is not shown in detail. According to this embodiment, the rotary brush tool is carried by the machine frame 1. In addition, the machine frame 1 can be set up such that it surrounds the workpiece or pipe 2, in this case like a claw. Moreover, it is conceivable for the machine frame 1 to rotate about an axis of the pipe, thereby enabling the pipe in question to be processed in the region of the weld seam 3 as a whole and over its entire circumference by the rotary brush tool.

[0021] Specifically, the rotary brush tool has a drive 4 only partially visible in FIG. 1 and that rotates a brush assembly 5 as an essential component of the rotary brush tool. The assembly 5 is equipped for this purpose with a ring brush 6, 7 best seen in FIG. 2. The ring brush 6, 7 is composed of a core sleeve 6 and bristles 7 that are anchored in the core sleeve 6 and project radially outward therefrom to form an annular brush. The core sleeve 6 can be made of a woven plastic strip of polyamide, for example. According to this embodiment shown in FIG. 2, but without limitation thereto, the bristles 7 are steel bristles anchored in the core sleeve 6 and that have bristle tips 7 that are bent forward. Of course, this is only for the sake of example.

[0022] The ring brush 6, 7 is received in a rotatably drivable brush holder 8 best seen in FIG. 1. The brush holder 8 can be designed as described in the applicant's patent DE 43 26 793 [U.S. Pat. No. 5,525,315]. In principle, other brush holders 8 are also conceivable here, such as those presented in detail in applicant's patent application WO 2017/220338 [US 2019/0224805]. The brush holder 8 for receiving the ring brush 6, 7 can be constructed from multiple parts as described in the above-mentioned publications. In principle, however, it is also conceivable for the ring brush 6, 7 to be securely connected to the brush holder 8. In general, however, a multi-part brush holder 8 will be used according to the publications mentioned above, not least in order to enable the ring brush 6, 7 to be replaced as need and wear dictate.

[0023] An adjustable stop 9 is also of particular importance for the rotary brush tool or the brush assembly 5. In fact, the stop 9 is connected to an arm 10 and can be positioned thereby with respect to its radial spacing A to the axis Z of the ring brush 6, 7 shown in FIG. 2. This is indicated by a corresponding arrow in FIG. 2. The movement of the stop 9 with respect to its position relative to the bristles 7 now takes place as a function of the roughness or coarseness of the surface of the workpiece 2. That is, the stop 9 is positioned depending on the roughness or coarseness of the surface of the workpiece 9. The criterion used for positioning the stop 9 is the already processed surface of the workpiece 2, i.e. the region of the surface of the workpiece 2 downstream of the rotary brush tool or the brush assembly 5 in the treatment direction indicated by arrow B in FIG. 2. In principle, the part of the surface of the workpiece 2 upstream in the treatment direction B can also be used for positioning the stop 9. According to this embodiment however and preferably, the region of the surface of the workpiece 2 downstream in the treatment direction B and has already been processed is examined for its roughness or coarseness, and the stop 9 is positioned on that basis.

[0024] Thus as also described in above-cited commonly owned U.S. Pat. No. 9,554,642 (which is incorporated herewith by reference) the brush 5 is rotated on the frame or housing 1 about the axis Z in one direction at a predetermined angular speed such that the bent-forward tips 7 of the steel-wire bristles 7 extending generally radially of the axis Z define a circular orbit centered on the axis Z. These tips 7 engage a surface of the workpiece 2 radially at a location to abrade the surface at this location. The stop or blocking element 9 nonrotatable relative to the brush 5 and radially inside the orbit and rearward in the brush-rotation direction from the abrading location temporarily slows angular movement of the bristle tips 7 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 7 striking and hammering the workpiece surface generally perpendicularly at the abrading location.

[0025] According to this embodiment, a roughness detector 11, 12, 13 is provided downstream of the brush assembly 5 or the rotary brush tool in the treatment direction B in order to enable detection of the roughness or coarseness of the already processed surface of the workpiece 2. For this purpose, the roughness detector 11, 12, 13 has a laser 11, a distance sensor 12, and a camera 13, for example a CCD camera 13. The laser 11, the distance sensor 12, and also the CCD camera 13 are all connected to a controller 14 that operates with or without feedback and is responsible for controlling and detecting the roughness measurement values R.sub.a, that is, for the sake of example and without limitation, the mean roughness R.sub.a in accordance with the introductory explanations.

[0026] In fact, the laser 11 is directed onto the surface of the workpiece 2 at a defined angle and projects an extremely thin line of light onto the surface in question. This line of light is now examined for distortions caused by the surface texture by the high-resolution camera 13, which may be equipped with an unillustrated lens. The surface profile in question can be calculated directly from the deflection of the line of light relative to its straight course. The image of this projected and, due to the surface texture, distorted line of light of the laser 11 is detected by the camera 13, and this image data is converted by the controller 14 connected to the camera 13 to the desired roughness values R.sub.a, or the roughness values in question R.sub.a are derived therefrom.

[0027] The additional distance sensor 12 is used primarily for control purposes and ensures that, in case of any deviations of the surface of the workpiece 2 from a plane, bulges, etc., a perfect and sharp image of the straight line of light outputted by the laser 11 is still present on the surface of the workpiece 2 and can be examined for deviations resulting from the surface texture. Optionally, the spacing of the entire roughness detector 11, 12, 13 to the surface of the workpiece 2 can be changed appropriately as indicated by a double arrow in FIG. 2. A change in the spacing is made in accordance with the measured values of the distance sensor 12.

[0028] As already explained, the stop 9 can be positioned radially for the most part relative to the axis Z of the ring brush 6, 7. A stop drive 15, which is merely indicated in FIG. 2, may provide for corresponding actuating movements of the stop 9 or of the arm 10 supporting the stop 9. For this purpose, the stop drive 15 acts on the arm 10 that is mounted so as to be rotatable about the axis Z coaxially with the ring brush 6, 7. This is obviously only for the sake of example and by no means limiting. In any case, the radial spacing A of the stop 9 to the axis Z of the ring brush 6, 7 can be varied by the stop drive 15, as indicated in FIG. 2.

[0029] In addition to the drive 4 for the ring brush 6, 7 and the stop drive 15 for the stop 9, another ring brush drive 16 is also provided. By the ring brush drive 16, the entire ring brush 6, 7 including the stop 9 and the arm 10 can be urges toward the surface of the workpiece 2 and lifted off same, thereby applying a load perpendicular to the surface of the workpiece 2, as indicated by a corresponding double arrow 16 in FIG. 2. The roughness depth of the surface of the workpiece 2 can thus also be influenced, as already explained above. For this purpose, the stop drive 15 on the one hand and the ring brush drive 16 on the other hand are each connected to the control unit 14 as indicated by corresponding electrical connecting lines in FIG. 2. In principle, the ring brush drive 16 can also ensure that the ring brush 6, 7 is displaced not only relative to its spacing from the surface of the workpiece 2, but alternatively or additionally also undergoes a change in position parallel to the surface of the workpiece in question 2. That is, the ring brush drive 16 may also be responsible for an axial movement of the ring brush 6, 7, as indicated by the double arrow in FIG. 1. Applied to FIG. 2, this means that the ring brush drive 16 also moves the ring brush 6, 7 perpendicular to the drawing plane or parallel to the axis Z.

[0030] In the context of the invention, the stop 9 is moved by the stop drive 15 and/or the ring brush 6, 7 along with stop 9 and with the arm 10 are displaced collectively by the ring brush drive 16 in dependence upon roughness values R.sub.a of the surface of the workpiece that are detected by the roughness detector 11, 12, 13. This can be performed by the controller 14 with or without feedback. For this purpose, the roughness values in question R.sub.aActual are detected in the treatment direction B downstream of the ring brush 6, 7 by the roughness detector 11, 12, 13 and transmitted to the controller 14. In the controller 14, these actual values R.sub.aActual are now compared with the set-point values R.sub.aTarget stored therein. Depending on the deviation of the actual values R.sub.aActual from the target values R.sub.aTarget, the stop 9 is now moved by the stop drive 15 and/or the entire ring brush 6, 7 by the ring-brush drive 16 in order to effect a convergence between the target values R.sub.aTarget and the actual values R.sub.aActual in the manner of a feedback control.