GRINDING DISC FOR A GRINDING DEVICE AND GRINDING SYSTEM

Abstract

A grinding disc for a grinding device, with a fastening interface formed for rotationally fixed fastening to a driven member of the grinding device such that the grinding disc, limited by a peripheral disc rim surface, can be driven into a grinding movement. The grinding disc has a fastening surface on a working side, to which fastening surface a grinding means provided with an abrasion layer can be or is detachably fastened via fastening means. The grinding disc has dust extraction openings arranged on the fastening surface and air intake openings arranged on the disc rim surface, which are connected respectively to dust outlet openings arranged on the device side of the grinding disc via an extraction channel system running in the grinding disc, with the result that, during grinding, the resulting grinding dust can be removed by means of a dust extraction device coupled to the grinding device.

Description

The invention relates to a grinding disc for a grinding device, with a fastening interface formed on a device side of the grinding disc facing the grinding device, which fastening interface is formed for rotationally fixed fastening to a driven member of the grinding device such that the grinding disc, limited by a peripheral disc rim surface, can be driven into a grinding movement suitable for grinding machining of a workpiece, wherein the grinding disc has a fastening surface on a working side axially opposite the device side, to which fastening surface a grinding means provided with an abrasion layer can be or is detachably fastened via fastening means, wherein the grinding disc has dust extraction openings arranged on the fastening surface and air intake openings arranged on the disc rim surface, which are connected respectively to dust outlet openings arranged on the device side of the grinding disc via an extraction channel system running in the grinding disc, with the result that, during grinding, the resulting grinding dust can be removed by means of a dust extraction device coupled to the grinding device.

It is known to extract abraded dust particles through the grinding disc with the help of an airstream. The air or dust extraction openings are located on the underside of the grinding disc.

A grinding disc of the type named at the outset is known for example from EP 3 187 305 A2. Numerous dust extraction openings, which can be connected to dust outlet openings arranged on the top side of the grinding disc via an extraction channel system, are located on the underside of the grinding disc described there, thus on the fastening surface, for fastening a grinding medium in particular in the form of an abrasive disc. Furthermore, extraction openings are provided arranged on the edge side of the disc, whereby grinding dust arising on the fastening surface during grinding can be extracted via the dust extraction openings formed there, and additionally grinding dust located in the periphery of the grinding disc via the lateral edge side dust extraction openings.

The object of the invention is to produce a grinding disc of the type named at the outset with which dust extraction of grinding dust arising during grinding can be optimised.

This object is achieved by a grinding disc with the features of independent claim 1. Developments of the invention are shown in the dependent claims.

The grinding disc according to the invention is characterised in that the dust outlet openings are respectively connected via axial through-channels to first dust extraction openings arranged on the fastening surface, wherein respectively a radial extraction channel extending radially outwards branches off from the axial through-channels, which extraction channel opens into one of the peripheral air intake openings, and wherein respectively an axial extraction channel branches off from the radial extraction channels and opens on the fastening surface via a second dust extraction opening.

A main flow direction radially from out to in and then upwards is established by the direct connection between the peripheral air intake openings and the device-side dust outlet openings, whereby, compared with conventional grinding discs, the flow resistance for the dust airstream is clearly reduced. In particular it is avoided that the dust airstream is deflected in one direction, in peripheral direction of the grinding disc, before exiting, device side, via the dust outlet openings. A type of jet nozzle is produced between a respective air intake opening and an associated dust outlet opening by the main flow direction directed upwards from laterally outside, which nozzle sucks air, and thus grinding dust, from other channel sections of the extraction channel in the manner of an ejector, with the result that this grinding dust is carried along.

Thus in addition to the already present suction effect for extracting the grinding dust via the first and second dust extraction openings, an additional suction is produced via the main flow. As a result, swirls and blockages in the grinding disc are reduced to a minimum. To the greatest possible extent, air flows in laminar fashion. To further increase air flow speed in the dust extraction channels, channel geometry is ensured. This leads to grinding residues, which possess mass, being able to follow the airstream better, and the grinding residues in the grinding disc thus being reduced. Furthermore, air swirling in the extraction channels is reduced, whereby the grinding residues in the grinding disc are reduced. This means that the grinding particles do not rotate, and almost all dust particles are extracted. The dust particles no longer reach the environment or, after extraction, no longer fall back onto the workpiece. A further important aspect is that the peripheral air intake openings ensure complete uncoupling of the dust extraction channels on the fastening surface or underside of the grinding disc. Thereby, the air required for extraction can also flow unhindered into the grinding disc when the user machines the whole surface of the material with the grinding disc.

In a development of the invention, at least two of the axial through-channels arranged adjacent to one another in peripheral direction of the grinding disc are connected to one another via a connecting channel running in peripheral direction. The suction effect of the main flow over the connecting channels is thus also extended to adjacent through-channels.

In a particularly preferred manner, an axial additional extraction channel branches off from the at least one connecting channel, which additional extraction channel opens out via a third dust extraction opening on the fastening surface. A third dust extraction opening can also be embedded on the fastening surface via the connecting channel, at the main flow between the peripheral air intake openings and the dust outlet openings.

In a further development of the invention, an operated additional extraction channel branches off from the at least one connecting channel, which additional extraction channel has a radial channel section connected to the connecting channel and an axial channel section abutting against the radial channel section, which axial channel section opens via a fourth dust extraction opening onto the fastening surface.

In particularly preferred manner, the at least one connecting channel is formed curved, arc-shaped, in peripheral direction of the grinding disc. The connecting channel can for example connect a plurality of axial through-channels together as a type of ring section. For example, the connecting channel can form a part of a circular ring which is arranged concentrically to the centre of the grinding disc.

In a further development of the invention, the air intake openings open out respectively by means of a channel-shaped section.

In particularly preferred manner, the channel-shaped sections are formed edge-less, in particular tangent-constant (G1 continuity). The channel-shaped sections can for example be formed in a parabola shape in the cross-section.

The openings of the air intake openings can be flow-optimised, with the result that in particular the formation of air-flow breakaway edges for the airstream when flowing into the air intake openings are avoided. This makes a substantial contribution to establishing a laminar flow through the extraction channel system. It is thus particularly important that the contour of the air intake opening, thus in particular of the channel-shaped section, is formed edge-less. This can for example take place by a flow-modulated contour of the air intake openings in which tangent-constant transitions are formed. In principle, it would also be possible to form curvature-constant (G2 continuity) transitions, even if this comes at a higher cost.

In a further development of the invention, the fastening surface of the grinding is free from extraction channels opening out on the disc rim surface. This improves the grinding effect as no slots needed for extraction, opening out on the edge surface, need be formed with a grinding means, in particular abrading disc, fastened to the fastening surface, with the result that a greater bearing surface and thus grinding surface is available on the edge side.

In a further development of the invention, at least one ventilation channel for ventilating the working side of the grinding disc via a ventilation opening opens out on the disc rim surface. Air can reach the inside of the fastening means fastened to the fastening surface via the at least one ventilation channel, which fastening means can for example be an adhesive layer in the form of a friction pad of a hook and loop closure which ensures that the dust particles swirl up, with the result that these can be extracted as well via the extraction channel system and not accumulate on the inside of the adhesive layer.

In a further development of the invention, the grinding disc has a base part equipped with the fastening surface and the dust extraction openings, and a cover part which is or can be detachably fastened to the base part via a fastening device, which cover part is equipped with the fastening interface for fastening to the driven member and the dust outlet openings.

Expediently, the base part is formed as a foam body. When producing the foam body, the extraction channel system is formed expediently with the dust extraction openings and the air intake openings the same. The cover part is expediently a plastic part, for example a plastic injection-moulded part, wherein the dust outlet openings can also be formed the same during production, in particular by means of plastic injection moulding.

In a further development of the invention, the fastening surface of the grinding disc has an annular outer edge section in which exclusively the second dust extraction openings are arranged.

Compared with conventional grinding discs, the grinding disc according to the invention manages with a lower number of dust extraction openings and air intake openings, as the main flow direction leads from the peripheral air intake openings via the extraction channel system to the dust outlet openings and not, as in the prior art, via the dust extraction openings at the fastening surface to the dust outlet openings, with the result that both the flow speed and the volume flow of extracted air is clearly increased compared with the prior art. There are thus fewer dust extraction openings on the fastening surface of the grinding disc according to the invention, and consequently, at the grinding means fastened thereto, fewer intake through holes, with the result that overall there is more grinding surface available for machining the workpieces. Overall, the grinding disc according to the invention manages with 30% to 50% fewer dust extraction openings compared with the prior art.

The invention also relates to a grinding system, with a grinding disc according to one of the preceding claims and with a grinding means in the form of an abrading disc which is or can be fastened to the fastening surface of the grinding disc via fastening means and has suction through holes which are flush with the dust extraction openings arranged on the fastening surface of the grinding disc.

The grinding means, in particular the abrading disc, has an abrasion layer with which the surface of the workpiece to be ground is machined. The abrasion layer can have a granulation or an abrasive stitch bonded fabric.

A preferred embodiment example of the invention is shown in the drawing, and will be explained in more detail below. In the drawings there are shown in:

FIG. 1 a side view of a grinding device equipped with a preferred embodiment example of the grinding disc according to the invention and a grinding means,

FIG. 2 a top view of the grinding device of FIG. 1,

FIG. 3 a perspective representation of the preferred embodiment example of the grinding disc according to the invention from FIG. 1,

FIG. 4 a top view of the grinding disc from FIG. 3,

FIG. 5 a section through the grinding disc along the line VI-VI in FIG. 4,

FIG. 6 an enlarged representation of the detail X from FIG. 5,

FIG. 7 a bottom view of the grinding disc from FIGS. 3 and 4,

FIG. 8 a top view of the grinding disc from FIG. 4 without cover part and

FIG. 9 a top view of a grinding means in the form of an abrading disc for fastening to the fastening surface of the grinding disc.

FIGS. 1 to 8 show a preferred embodiment example of the grinding disc according to the invention 11 when being used as a grinding device 12. The grinding device 12 serves to abrasively machine or grind a workpiece 13, which can for example be a component made of wood, metal or other materials. For example it is possible to machine the body of a motor vehicle or grind wooden construction elements with the help of the grinding device 12.

By way of example, the grinding device 12 is shown in the form of a portable grinding machine. The portable grinding machine is for example a disc-type sander.

The grinding device 12 possesses a drive housing 14 in which a drive mechanism, not shown, in particular in the form of a drive motor, is accommodated. Overall, the drive housing 14 is arranged and shaped such that it can serve as a handle for holding the grinding device 12. The user can then likewise grasp the drive housing 14 with the other hand, and press the grinding device 12 downwards against a workpiece 13 to be ground.

The drive mechanism in the form of the drive motor can drive a tool shaft directly or via a gear mechanism (not shown), on the driven member (not shown) of which shaft there is arranged a grinding disc receiver (not shown), to which the grinding disc 11 can be coupled via its fastening interface 15, described below in more detail.

The drive mechanism in the form of the drive motor is preferably an electric drive motor. Alternatively, a compressed air motor is also conceivable. A utility connection 16, for connecting a supply line 17, for example an electric line and/or a compressed air hose (depending on the drive concept of the drive motor) is provided at the drive housing.

A dust collection section 18, which opens out from the drive housing 14 via a dust removal connection 19, is located above the grinding disc receiver of the drive housing 14 and associated fastening interface 15 of the grinding disc 11. An extraction line 20, for example a suction tube or suction hose, which for example leads to a vacuum cleaner (not shown), is connected to the dust removal connection 19. The extraction line 20 and vacuum cleaner possibly attached thereto are components of an extraction device 21 for extracting dust from a surface of the workpiece 13.

As already mentioned, the fastening interface 15 serves to couple the grinding disc 11 to the grinding disc receiver or counter-fastening interface to the drive housing 14 on the sides of the grinding disc 11.

As shown in particular in FIG. 3, the fastening interface 15 comprises a receiver 22 with a central through-hole, wherein the through-hole 23 is encircled by an irregularly shaped contour 24. The contour 24 can for example be developed like a keyhole or a bayonet.

As shown in particular in FIG. 5, the central through-hole 23 penetrates a securing plate, for example disc 25, arranged in the grinding disc 11. A pin (not shown) coupled to the driven member, the free cylindrical end of which pin is pushed through the central securing hole 23 for the purposes of fastening the grinding disc 11 and is secured to the securing plate by means of a fastening element (not shown), for example a fastening screw, is located on the counter-fastening interface of the drive housing 14. Simultaneously, the pin is equipped with a projection engaging in the in particular keyhole contour 14 on the fastening interface 15. A rotary entrainment of the grinding disc 11 is achieved by the engagement of the contoured projection in the complementary contour 25 on the receiver, i.e. the rotation movement of the driven member is transferred into a rotation movement of the grinding disc 11.

As shown in particular in FIGS. 3 to 8, the fastening interface 15 of the grinding disc 11 is located on a device side 26 of the grinding disc 11 facing the drive housing 14, while a fastening surface 28 for a grinding means 29, described below in more detail, is provided on a working side 27 axially opposite the device side 26. The grinding disc 11 is limited in a peripheral disc rim surface 30 on the periphery side. As shown in particular in FIGS. 3 to 5, the grinding disc has a base part 31 equipped with the fastening surface 28, and a cover part 33, which is or can be detachably fastened to the base part via a fastening device 32 (FIG. 5), which is equipped with the fastening interface 15. The fastening device 32 comprises, on the cover part 33, fastening projections in a ring concentrically about the centre of the grinding disc, which fastening projections engage on the base part 31 in associated fastening slots. Additionally, the cover part 33 is still stuck to or screwed to the base part 31.

The base section 31 is formed as a foam body. The cover part 33 is expediently a plastic part, in particular a plastic injection-moulded part. The securing disc 25 can be made from a different material from the cover part 33 and moulded the same as the cover part 33 during production.

Fastening means for detachable fastening of a grinding means 29 are provided on the fastening surface 28 of the grinding disc 11, thus in particular on the underside of the base part 31.

As shown by way of example in FIG. 9, the grinding means 34 is formed expediently as an abrading disc.

The grinding means possesses an abrasion layer which has a granulation or an abrasive stitch bonded fabric. The fastening means for fastening the grinding means in the form of the abrading disc to the fastening surface 28 expediently comprises an adhesive layer, for example in the form of an adhesive layer on the fastening surface 28 and a counter adhesive layer formed on the abrading disc. Adhesive layer and counter adhesive layer can for example be formed as a hook and loop closure. A hook and loop closure is generally formed of two parts, wherein on one closing part connecting parts with a hook shape, mushroom shape, arrow shape, hammer shape or the like is arranged, and these interact in a binding manner with a corresponding loop or noose material of the other closure part. It is thus necessary merely to place the abrading disc on the underside of the grinding disc 11, thus on the fastening surface 28, and press against it. To remove the abrading disc, this is simply pulled off the grinding disc contrary to the holding force exerted by the hook and loop closure.

As shown in particular in FIG. 7, the grinding disc 11 has dust extraction openings 35a-d arranged on the fastening surface 28 and air intake openings 36 arranged on the disc rim surface 30, which are respectively connected to dust outlet openings 38 arranged on the device side 26 of the grinding disc 11 via an extraction channel system (FIG. 5) running in the grinding disc 11, with the result that grinding dust arising during grinding can be removed by means of the dust extraction device 21 coupled to the grinding device 12.

As the synopsis of in particular FIGS. 4, 5, 7 and 8 shows, the dust outlet openings 38 are arranged on the device side 26 of the grinding disc 11, in particular on the top side of cover part 33. The dust outlet openings 38 are respectively connected via axial through-channels 39 (FIG. 8) to first dust extraction openings 35a arranged on the fastening surface 28, wherein a radial extraction channel 40 extending radially outwards branches off respectively from the axial through-channels 39, which extraction channel opens into one of the peripheral air intake openings 36. An axial extraction channel 41 branches off respectively from the radial extraction channels 40 and opens on the fastening surface 28 via a second dust extraction opening 35b.

The air intake openings 36 on the disc rim surface 30 are thus connected to the dust outlet openings 38 arranged on the top side of the grinding disc 11 using essentially the shortest route. Main extraction thus takes place via the peripheral air intake openings 36 on the disc rim surface 30 in direction of the dust outlet openings 38. The radial extraction channel 40 between the peripheral air intake openings 36 and the axial through-channel 39 therefore forms a main extraction channel together with the upper section of the axial through-channel 39.

The first and second dust extraction openings 35a, 35b are connected to the fastening surface 28 at this main extraction channel. The air flowing into the main extraction channel is thus in the manner of a jet nozzle, and also produces an additional extraction effect at the bottom part of the axial through-channel 39 as well as at the axial extraction channel 41, according to the ejector principle, with the result that grinding dust is dragged into the extraction channel system via the first and second dust extraction openings 35a, 35b.

As shown in particular in FIG. 7, the first dust extraction openings 35a are arranged radially further inside than the second dust extraction openings 35b. The first dust extraction openings 35a are expediently grouped around the centre of the grinding disc 11 at regular intervals. For example it is possible that the same number of first dust extraction openings 35a, for example two first dust extraction openings 35a, is arranged in each quadrant of the fastening surface 28 of the grinding disc 11.

As mentioned, the second dust extraction openings 35b are closer to the disc rim surface 30. It is possible that the second dust extraction openings 35b are larger in diameter than the first dust extraction openings 35a. Furthermore, it is possible that the second dust extraction openings 35b are arranged on a circuit arranged concentrically about the centre. Furthermore, it is possible that the same number of second dust extraction openings 35b, for example two second dust extraction openings 35b, are arranged in each quadrant of the fastening surface 28.

As shown in particular in FIG. 7, it is noticeable that the fastening surface 28 is free from extraction channels opening onto the disc rim surface 30. As shown in particular in FIG. 8, at least two of the axial through-channels 39, arranged adjacent to one another in peripheral direction of the grinding disc 11, are connected to one another via a connecting channel 42 running in peripheral direction. Expediently, the connecting channel 42 is formed such that more than two axial through-channels 39 are connected to one another.

An axial additional extraction channel 43 branches off from the at least one connecting channel 42, which axial additional extraction channel opens out onto the fastening surface 28 via a third dust extraction opening 35c. While the first and second dust outlet openings 35a, 35b lie on a common radius line starting from the centre, the third dust extraction openings 35c are arranged offset therefrom. As shown in FIG. 4, the third dust extraction openings 35c are also grouped around the centre of the grinding disc 11. The third dust extraction openings 35c can have a smaller diameter than the first and second dust extraction openings 35a, 35b.

As shown in particular in FIG. 8, two connecting channels 42a, 42b are provided either side of a horizontal centre line through the grinding disc, which respectively connect together several of the axial through-channels 39, for example respectively four axial through-channels 39.

As also shown in FIG. 8, a curved additional extraction channel 50 branches off from the at least one connecting channel 42a, b, which extraction channel has a radial channel section 51 connected to the connecting channel and an axial channel section 52 abutting against the radial channel section 51, which axial channel section opens onto the fastening surface 28 via a fourth dust extraction opening 35d.

As shown in FIG. 7, the fourth dust extraction openings 35d are arranged radially most inward. It is also possible here for the fourth dust extraction openings 35d to be grouped around the centre of the grinding disc 11. Compared with the other dust extraction openings 35a-c, the fourth dust extraction openings 35d can have the smallest diameter. The third and fourth dust extraction openings 35c, 35d lie on a common radial line.

As shown in particular in FIG. 8, the air intake openings 36 are formed characteristic on the disc rim surface 30. They can respectively open out by means of a channel-shaped section 44. The channel-shaped sections 44 are formed edge-less, in particular tangent-constant, whereby the formation of breakaway edges, and thus turbulent flows, are avoided at the intake of the input of the grinding disc 11. Therefore, the channel-shaped, edge-less sections of the air intake openings 36 perform an important contribution to establishing a laminar flow in the extraction channel system 37. The cross-section of the channel-shaped section 44 can for example be formed as a parabola.

As shown in particular in FIG. 6, an inflow section 45 of the air intake openings 36, formed respectively on the one hand by the bottom edge of the cover part 33 and on the other hand by the base of the groove of the channel-shaped sections 34, is attached radially inwards in direction to the channel-shaped sections. As already mentioned, a grinding means, in the form of an abrading disc, is fastened to the fastening surface 28 of the grinding disc via the fastening means in the form of the hook and loop closure.

The abrading disc possesses output through-holes 46a-d which are flush with the dust extraction openings 35a-d arranged on the fastening surface 28 of the grinding disc 11. Grinding dust thus ends up from the workpiece surface, via the intake through holes 46a-d of the abrading disc and the dust extraction openings 35a-d, at the fastening surface 28 of the grinding disc 11, and ultimately in the extraction channel system 37, and is then extracted via the dust outlet openings 38 arranged on the cover part 33. Grinding dust thus ultimately collects in the dust collection section 18 and is then extracted via the dust removal connection 19 and the extraction line 20.

As shown in particular in FIG. 8, the grinding disc 11 possesses at least one ventilation channel 47 for ventilating the working side 27 of the grinding disc 11, which opens onto the disc rim surface 30 via a ventilation opening 48. Expediently, two ventilation openings 48a, 48b, diametrically opposite one another, are provided with regard to the centre of the grinding disc 11, which ventilation openings are connected to associated ventilation channels 47a, 47b. Air can reach the inside of the friction pad fastened to the fastening surface 28 via ventilation channels 47a, 47b, and in so doing ensures that the dust particles swirl up, with the result that these can be extracted as well via the extraction channel system 37 and not accumulate on the inside of the adhesive layer.

Claims

1. A griding disc for a grinding device a fastening interface formed on a device side of the grinding disc facing the grinding device, which fastening interface is formed for rotationally fixed fastening to a driven member of the grinding device such that the grinding disc, limited by a peripheral disc rim surface, can be driven into a grinding movement suitable for grinding machining of a workpiece,wherein the grinding disc has a fastening surface on a working side axially opposite the device side, to which fastening surface a grinding means provided with an abrasion layer can be or is detachably fastened via fastening means,wherein the grinding disc has dust extraction openings arranged on the fastening surface and air intake openings arranged on the disc rim surface, which openings are respectively connected via an extraction channel system running in the grinding disc to dust outlet openings arranged on the device side of the grinding disc, with the result that, during grinding, the resulting grinding dust can be removed by means of a dust extraction device coupled to the grinding device,wherein the dust outlet openings are respectively connected via axial through-channels to first dust extraction openings arranged on the fastening surface, wherein a radial extraction channelextending radially outwards branches off respectively from the axial through-channels, which extraction channel opens into one of the peripheral air intake openings, and wherein an axial extraction channel branches off respectively from the radial extraction channelsand opens on the fastening surface via a second dust extraction opening.

2. The grinding disc according to claim 1, wherein at least two of the axial through-channels, arranged adjacent to one another in peripheral direction of the grinding disc, are connected to one another via a connecting channel running in peripheral direction.

3. The grinding disc according to claim 2, wherein an axial additional extraction channel branches off from the at least one connecting channel, which additional extraction channel opens out via a third dust extraction opening on the fastening surface.

4. The grinding disc according to claim 2, wherein a curved additional extraction channel branches off from the at least one connecting channel, which extraction channel has a radial channel section connected to the connecting channel and an axial channel section abutting against the radial channel section, which axial channel section opens onto the fastening surface via a fourth dust extraction opening on the fastening surface.

5. The grinding disc according to claim 2, 4, wherein the at least one connecting channel is formed curved in arc shape in peripheral direction of the grinding disc.

6. The grinding disc according claim 1, wherein the air intake openings respectively open out by means of a channel-shaped section.

7. The grinding disc according to claim 6, wherein the channel-shaped section is formed edge-less, in particular tangent-constant.

8. The grinding disc according to claim 7, wherein the channel-shaped section is formed in a parabola shape in the cross-section.

9. The grinding disc according to claim 1, wherein a base part equipped with the fastening surface and the dust extraction openings, and a cover part which is or can be detachably fastened to the base part via a fastening device, which cover part is equipped with the fastening interface for fastening to the driven member and the dust outlet openings.

10. The grinding disc according to claim 1, that wherein the fastening surface of the grinding disc has an annular outer edge section in which exclusively the second dust extraction openings are arranged.

11. A grinding system, with a grinding disc according to claim 1, and with a grinding means in the form of an abrading disc which is or can be fastened to the fastening surface of the grinding disc via fastening means and has intake through holes which are flush with the dust extraction openings arranged on the fastening surface of the grinding disc.