Brush assembly

Abstract

The invention relates to a brush assembly (3) which is equipped with a brush holder (4) rotatably driven about an axis (A) and a ring brush (5, 6) consisting essentially of a brush strip (5) and bristles (6) attached thereto, forming a bristle ring (7) and projecting outwards. According to the invention, the brush strip (5) with its longitudinal extent (L) and thus also the bristle ring (7) is connected to the brush holder (4) at an angle to the axis (A), deviating from a vertical orientation.

Description

[0001] The invention relates to a method for machining the surface of a workpiece according to claim 1.

[0002] A known and generic method, as described in US 2009 / 199356 A1, essentially involves the production of such a brush unit. For this purpose, the bristle ring can be spiral-shaped and rotate around an axis.

[0003] In a brush unit of the design described above according to EP 1 834 733 B1, the bristles are slowed down for a specific time using a stopper that is inserted into the rotating bristle ring. Once the bristles are released by passing through the stopper, the kinetic energy stored in this way, i.e. by the bristles and / or a brush belt holding the bristles, can be used. The kinetic energy is used to predominantly percussively process a surface of the workpiece using the bristles. This achieves effects comparable to those observed in sandblasting. The advantage of the known procedure according to EP 1 834 733 B1 compared to sandblasting is that it works without blasting media, so that the technical outlay on the system is significantly reduced. Environmental pollution caused by the blasting media can also be avoided.In addition, a particularly cost-effective structure and efficient approach are observed. This has proven successful.

[0004] In the further prior art according to WO 2012 / 038537 A1, the stop means immersed in the rotating bristle ring is simultaneously designed as a grinding body for the bristles. In this case, a distinction can be made between the two functions, i.e. the stop function and the grinding function, depending on the direction of rotation of the ring brush and / or the position of the stop means relative to the bristle ring. In fact, the stop means is designed to be adjustable relative to the bristle ring. The stop means is adjusted radially and / or tangentially. Eccentric adjustment of the stop means is also possible. In addition, the stop means can be adjusted by the driven bristles.

[0005] The state of the art has generally proven itself in terms of processing the surface of the workpiece using bristles and the resulting roughness. However, with previous methods, the surface of the workpiece is not consistently covered with "craters" caused by the bristles. While comparable and adjustable roughness levels to those achieved with sandblasting can be achieved, allowing subsequent coating, welding, etc. of the workpiece surface to be carried out without problems, the roughness profile is subject to fluctuations, thus exhibiting a certain degree of anisotropy in the state of the art. However, for many applications, an isotropic and uniform roughness of the surface of the treated workpiece is required.

[0006] The anisotropy or lack of uniformity of the roughness profile observed in the prior art can essentially be attributed to the fact that the bristles are typically anchored in the brush belt. Since the bristles are often U-shaped, the brush belt carrying the bristles is equipped with rows of bristles in its circumferential direction and axial spacing between them, which is due, for example, to the U-shape of the bristles. These spacings between the individual rows of bristles result in the roughness profile being uneven during percussive machining of the workpiece surface. In practice, attempts are made to counteract this by having the brush unit or a rotary brush tool equipped with one back and forth over the surface, for example.

[0007] Aside from the fact that such a movement is strenuous and cannot necessarily ensure the required uniformity, such procedures cannot be directly implemented and realized, for example, when machining the surface of the workpiece with a machine, such as a robot arm. Furthermore, the prior art calls for even more effective machining of the workpiece surface. The invention aims to remedy this situation.

[0008] The invention is based on the technical problem of further developing such a method for machining the surface of a workpiece using a brush unit in such a way that the roughness profile produced on the surface of the workpiece thus machined has a higher degree of uniformity than the previous state of the art. Furthermore, the possibility of increasing the roughness if necessary should be provided at the same time.

[0009] To solve this technical problem, the invention proposes, in a generic method for processing the surface of a workpiece using a brush unit, that the bristle ring of the ring brush, which runs obliquely relative to the axis of the brush holder, acts on the surface in a tumbling, rotating manner.

[0010] In In this context, the approach is usually such that the longitudinal extension of the brush strip and the axis of the brush holder form an acute angle of approximately 60° to less than 90°. Acute angles of approximately 70° to 85° are preferred in this context. Angles of approximately 85° have proven particularly advantageous in this context.

[0011] This "inclined position" of the brush belt and consequently also of the bristle ring relative to the axis of the rotary-driven brush holder ensures particularly uniform processing of the surface of a workpiece. The bristle ring, which is inclined relative to the axis of the brush holder, ultimately ensures the wobbling, rotating impact on the surface of the workpiece. This wobbling motion is explained by the fact that the bristles of the bristle ring are inclined relative to the axis of the brush holder. If one now observes one revolution of the bristle ring, this corresponds, in a side view of the brush holder, to the fact that the bristles do not describe the same radius with respect to the surface of the workpiece during one revolution of the brush holder. Consequently, they process the surface at a single point in cross-section, or in reality, along a more or less distinct line.Rather, the inclined position of the brush belt and thus also of the bristle ring when the brush holder rotates relative to the stationary workpiece with its surface ensures that the bristles in question axially sweep over a certain area of ​​the surface of the workpiece when viewed from the side of the brush holder, a so-called processing zone.

[0012] This back-and-forth movement of the bristles in a side view is interpreted in the context of the present application as a wobbling movement. If one imagines the bristle ring as a disk that is embedded in the brush holder at an angle to the axis of the latter, the disk in question of the bristle ring performs a wobbling movement in the side view or in the front view of the brush holder. This is because the rotation axis belonging to the disk in question changes direction during the rotation of the bristle ring, as will be explained in more detail below with reference to the exemplary embodiment. In any case, the overall effect is a wobbling, rotating impact on the surface of the workpiece, which ensures particularly uniform surface treatment. In particular, any inhomogeneities as in the prior art are expressly not observed.

[0013] According to a further advantageous embodiment, the brush belt is guided in more than one revolution around the axis of the brush holder and connected to the latter. Furthermore, the design is such that the brush belt encloses the brush holder in a spiral shape. In this case, the brush belt, which runs spirally around the axis of the brush holder, generally has a constant pitch angle, thus ensuring that the spiral described by the brush belt relative to the axis of the brush holder is regular. Of course, an irregular shape is also conceivable.

[0014] This additional helical design of the brush belt's path in relation to the axis of the brush holder essentially defines several discs of the bristle ring - so to speak. These discs perform respective wobbling movements around their fictitious axis of rotation. This then results in individual axial working areas or processing zones created by the wobbling movement and swept over by the respective bristle overlapping one another. This mutual overlap then has the overall effect that the workpiece to be machined in this way is provided with a roughness profile on its surface which has a previously unobserved homogeneity, i.e. in which the individual craters belonging to the roughness profile are evenly distributed over the surface with largely the same depth and the same distance from one another.

[0015] In order to specifically and individually implement the helical shape of the brush belt relative to the axis of the brush holder, the brush holder has a circumferential groove to accommodate the brush belt. This is usually done so that the brush belt engages in the relevant groove with essentially no lateral play. The groove is advantageously delimited by respective groove walls. The groove walls are generally perpendicular to a cylindrical surface of the brush holder. In fact, it has proven particularly advantageous if the brush holder, including the groove and groove walls, is designed as a plastic molded part, and in particular as an injection-molded plastic part.

[0016] To secure the brush belt in the respective groove, it is connected to the brush holder at least at certain points. The connection is generally mechanical and / or adhesive. Typically, the brush belt is designed as a fabric belt, for example, a polyamide fabric belt.

[0017] The described brush unit can also be advantageously equipped with a stopper that is immersed in the rotating bristle ring. This stopper can be used to influence the roughness particularly favorably and positively, as described in detail in the applicant's EP 1 834 733 B1. In principle, such a stopper is, of course, also unnecessary.

[0018] The invention is explained in more detail below with reference to a drawing which merely represents an exemplary embodiment; in the drawings: Fig. 1 shows the method according to the invention for machining the surface of a workpiece using the brush unit in a perspective view together with a rotary brush tool, Fig. 2 shows the brush holder in a detailed view and Fig. 3 shows the brush holder in a side view during machining of the surface of the workpiece and the tumbling rotary action of the surface in question provided according to the invention.

[0019] In the Fig. 1 A rotary brush tool is shown, which is equipped with a machine housing 1 and a drive unit 2, which is only indicated and accommodated therein, for a brush unit 3. The brush unit 3 has a brush holder 4 which can be driven in rotation about an axis A. The brush holder 4 is the subject of a detailed view in the Fig. 2 .

[0020] In addition, a ring brush 5, 6 is provided, consisting essentially of a brush band 5 and bristles 6 connected thereto, forming a bristle ring 7 and projecting outwards. In particular, in the schematic side view according to the Fig. 3 one can see the individual bristles 6 as they are anchored in the brush belt 5. The individual bristles 6 can be U-shaped and can be inserted through respective receiving holes 5a in the brush belt 5. This is only shown in detail in the Fig. 3 indicated.

[0021] According to the invention, the design is such that the brush belt 5 with its Fig. 2 and 3 indicated longitudinal extension L and thus also the bristle ring 7 is connected to the brush holder 4 in a manner different from a vertical orientation compared to the axis A of the brush holder 4, running obliquely to the axis A. In fact, one observes in the embodiment and according to the Fig. 2 and3 In this context, an acute angle α is observed between the longitudinal extension L of the brush belt 5 on the one hand and the axis A of the brush holder 4 on the other. According to the exemplary embodiment, the acute angle α in question assumes values ​​in the range of approximately 70° to 85°, and is in any case below 90°. Angles α in the range of approximately 85° are usually used here, although this is of course only an example.

[0022] By this inclination of the brush belt 5 and thus also of the bristle ring 7 or the bristles 6 projecting outwards from the brush belt 5 in comparison to the axis A of the brush holder 4, it is achieved overall that the surface 9 of a Fig. 3 This can best be seen from the Fig. 3 comprehend.

[0023] If one assumes at this point - fictitiously - that the brush band 5 and the bristles 6 connected to it and thus also the bristle ring 7 as a whole describe a disk, the disk in question rotates when the brush holder 4 rotates about its axis A at a speed in the Fig. 3 indicated rotation itself around its own rotation axis R. Due to the rotation of the brush holder 4 and the inclination of the disc, the associated and fictitious rotation axis R now has the Fig. 3 In effect, a precessional motion or wobbling motion of the assumed disk is observed, which manifests itself in the different orientations of the rotation axis R of the assumed disk.

[0024] This wobbling movement and the associated wobbling, rotating impact on the surface 9 of the workpiece by the ring brush 5, 6 now results in a respective bristle 6 impacting the respective surface 9 of the workpiece not only at specific points during its rotation, but rather an axially extended and in the Fig. 3 indicated machining area B on the surface 9 of the workpiece.

[0025] Since the bristles 6 are usually U-shaped and therefore have a slight spacing between them, the surface 9 of the workpiece in question is no longer practically exposed to stripes by the individual bristles 6, as in the prior art, but rather the individual processing areas B of the bristles 6 overlap one another, thus ensuring a particularly homogeneous roughness profile on the surface 9 of the workpiece in question. This consistency and design of the roughness profile have not been observed before.

[0026] The brush belt 5 is now not only guided in one revolution around the brush holder 4, but in more than one revolution around the axis A of the brush holder 4 and connected to it. In fact, the brush belt 5 encloses the brush holder 4 in a spiral shape. The overall design is such that the brush belt 5, which runs spirally to the axis A of the brush holder 4, has a constant pitch angle, thus ultimately the individual Fig. 2 The angle α indicated between the respective longitudinal extension L of the brush belt 5 and the axis A of the brush holder 4 are each designed to be the same size. This is therefore a uniform spiral in which the brush belt 4 is guided around the respective axis A.

[0027] In addition, the design is such that the brush belt 4 engages substantially laterally without play in a circumferential groove 10, as can be seen from the Fig. 2 can be understood. The respective groove 10 is delimited by groove walls 11, each of which stands opposite a cylindrical surface. The brush holder 4, together with the groove 10 and the groove walls 11 defining the groove 10, is designed as a plastic part and preferably as a plastic injection-molded part. The groove 10 and the groove walls 11 can also be printed or introduced by a three-dimensional molding process. Mechanical production of the groove 10 as well as the groove walls 11, for example by milling a cylindrical plastic part, is also conceivable.

[0028] The brush belt 5 is connected to the brush holder 4 at least at certain points. The connection can be mechanical and / or adhesive. Furthermore, the brush belt 4 is usually designed as a fabric belt, particularly made of a polyamide fabric.

[0029] In addition, a brush that is immersed in the rotating bristle ring 7 and only in the Fig. 1 indicated stop means 12 may be provided, which is connected to a boom 13 of the rotary brush tool shown there or its machine housing 1.

[0030] As soon as the brush holder 4 rotates about its axis A, the already mentioned wobbling, rotating action on the surface 9 of the corresponding workpiece occurs. In addition, each individual bristle 6 or each helix of the brush belt 4 processes the already mentioned and axially extended processing zone B on the surface 9 of the workpiece, as shown in the Fig. 3 This results in an overlap of the individual processing zones B, resulting in the surface 9 being provided with a particularly homogeneous roughness profile. According to the exemplary embodiment, the individual bristles 6 are made of steel. Of course, other materials such as plastic or combinations thereof are also conceivable.

Claims

1. A method for processing the surface (9) of a workpiece with the aid of a brush assembly (3), wherein the brush assembly (3) is equipped with a brush holder (4), which can be driven rotatably around an axis (A), and a ring brush (5, 6) comprising essentially a brush belt (5) and bristles (6) connected thereto, forming a bristle ring (7) and protruding outwards, according to which the brush belt (5) with its longitudinal extension (L) and thus also the bristle ring (7) diverging from its perpendicular orientation with respect to the axis (A) of the brush holder (4) is connected to the brush holder (4) running obliquely to the axle (A), characterised in that the bristle ring (7) of the ring brush (5, 6) running obliquely with respect to the axis (A) of the brush holder (4) has a rotational tumbling effect on the surface (9).

2. The method according to claim 1, characterised in that the longitudinal extension (L) of the brush belt (5) and the axis (A) of the brush holder (4) enclose an acute angle (α) of approx. 60° to below 90°, preferably 70° to 85° and particularly preferably of approx. 85° to each other.

3. The method according to claim 1 or 2, characterised in that the brush belt (5) is guided around the axis (A) of the brush holder (4) in more than one rotation and is connected thereto.

4. The method according to any one of claims 1 to 3, characterised in that the brush band (5) surrounds the brush holder (4) in a helical manner.

5. The method according to claim 4, characterised in that the brush belt (5) running helically to the axis (A) of the brush holder (4) has a constant angle of inclination.

6. The method according to any one of claims 1 to 5, characterised in that the brush holder (4) has a groove (10) running around the circumference for receiving the brush belt (5).

7. The method according to claim 6, characterised in that the brush belt (5) engages in the groove (10) essentially laterally free from play.

8. The method according to claim 6 or 7, characterised in that the groove (10) is bounded by groove walls (11) each standing vertically with respect to a cylinder surface.

9. The method according to any one of claims 1 to 8, characterised in that the brush belt (5) is connected at least in a pointwise manner to the brush holder (4).

10. The method according to claim 9, characterised in that the connection is made mechanically and / or adhesively.

11. The method according to any one of claims 1 to 10, characterised in that the brush belt (4) is designed as a fabric belt and the brush holder (4) as a plastic moulding.

12. The method according to any one of claims 1 to 11, characterised in that in addition a stop means (12) dipping into the rotating bristle ring (7) is provided.

13. The method according to any one of claims 1 to 12, characterised in that that the individual processing zones (B) created by each coil of the brush belt (5) on the surface (9) overlap at the edge.

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