EP1543923B1 - Roughing disc - Google Patents

Description

The invention relates to a roughing grinding wheel according to the preamble of claim 1.

In such known roughing wheels whose diameter is greater by at least a factor of 10 than their thickness, when used on hand-held angle grinders in the grinding insert strong vibrations occur, which can cause considerable physical damage to the hand-arm system. To eliminate this disadvantage, vibration and noise reduced roughing wheels have been developed, but have other disadvantages such as unpleasant odor during the grinding process and / or lower grinding performance.

From DE 26 32 652 A a noise-damped grinding wheel is known in which two sanding plates are firmly joined together by means of a layer of suitable plastic, usually a polymer, it being expressly pointed out that this material must not be too soft, so that the two sanding plates are securely connected to each other. The layer should be noise and vibration damping, on the one hand to reduce the noise nuisance, on the other hand, to reduce the adverse effects of vibrations on the hands and arms of the operator.

From CH-PS 434 023 a relatively thick circumferential grinding wheel is known, which consists of several fabric-reinforced, glued together individual disks, wherein in the adhesive layer, an elastic insert can be provided. Such packages have a higher grinding performance than a one-piece composite compact disc. From CH-PS 434 023 a compact disc is also known, each having abrasive-free zones in their radially outer regions, which are formed by annular spacers, which may optionally be removed again, so that a significant gap between the adjacent regions is formed , These abrasive-free zones lead to a particularly cool grinding during circumferential grinding and, in addition, produce additional chip space which enables a substantially increased grinding performance with otherwise identical disk composition.

The invention has the object of providing a roughing grinding wheel of the generic type in such a way that when used under forces that attack substantially in the direction of the central axis of the grinding wheel, the vibrations are significantly reduced.

This object is achieved by the features in the characterizing part of claim 1. The grinding wheel has a compact construction in the region within the at least one annular separating layer and has a two-layer or multi-layer structure only in the region of the at least one separating layer. The separation layer has primarily the function of reducing the amplitude of vibration during grinding. It does not primarily act as a cushioning layer but softens the grinding wheel in this area without the need to soften the overall structure of the abrasive grain bonded by the binder. The abrasion itself is therefore not increased. The separating layer extends in the radial direction only over the working area of the grinding wheel, that is to say only via the area which can be worked off during the grinding operation. The work areas of the grinding wheel defined by the radial extent of the separating layer can move radially relative to one another and thus under the axial Dodge forces resiliently. The amplitude of the oscillation occurring due to the bending in the attack area and the subsequent recovery is thereby greatly reduced compared with grinding wheels formed continuously as a composite grinding wheel. This causes a softer and less vibration sanding.

Claims 2 and 3 indicate particularly advantageous embodiments of the at least one separating layer.

Claim 4 indicates a preferred thickness range of each release layer.

According to claim 5 advantageously at most three separating layers are present.

Claim 6 indicates where advantageously the separating layer is arranged when only one separating layer is present.

Claims 7 and 8 indicate preferred ranges of outside diameter and thickness of the grinding wheel.

Fig. 1

eine Hand-Schleifmaschine mit einer Schrupp-Schleifscheibe nach der Erfindung im Schleifeinsatz,

Fig. 2

eine erfindungsgemäße Schrupp-Schleifscheibe in einer Seitenansicht in Explosionsdarstellung,

Fig. 3

eine Schleifscheibe nach Fig. 2 in Normal-Darstellung,

Fig. 4

einen Teilschnitt durch eine Schleifscheibe mit zwei Trennschichten,

Fig. 5

einen Teilschnitt durch eine Schleifscheibe mit drei Trennschichten und

Fig. 6

einen Teilschnitt durch eine Schleifscheibe mit einer Trennschicht aus nur einer Zwischenlage.

Further features, advantages and details of the invention will become apparent from the following description of exemplary embodiments with reference to the drawing. It shows

Fig. 1

a hand grinder with a roughing wheel according to the invention in the grinding insert,

Fig. 2

a roughing grinding wheel according to the invention in an exploded side view,

Fig. 3

a grinding wheel according to FIG. 2 in normal representation,

Fig. 4

a partial section through a grinding wheel with two separating layers,

Fig. 5

a partial section through a grinding wheel with three separating layers and

Fig. 6

a partial section through a grinding wheel with a release layer of only one intermediate layer.

As is apparent from Fig. 1, roughing wheels 1 are used on hand-grinders 2, namely so-called angle grinders. They are attached to an output shaft 3 of the grinding machine 2, which by a central opening 4 with a centering ring 5 of Grinding wheel 1 is inserted therethrough, so that the center axis 6 of the grinding wheel 1 coincides with the corresponding center axis of the output shaft 3. The attachment of the grinding wheel 1 on the output shaft 3 by means of a clamping nut. 7

The rough grinding wheel 1 is used on a workpiece 8 to be machined in such a way that the grinding wheel 1 is loaded with a force P not radially to its center axis 6, but substantially transversely thereto in the area of its outer circumference 9, so that it is bent accordingly, as shown in Fig. 1 exaggerated for the attack area 10 of the grinding wheel 1 on the workpiece 8. The angle a between the direction of attack of the force P and the center axis 6 is predominantly in the range of 20 to 60 °. As further shown in Fig. 1, the grinding wheel 1 returns after leaving the attack area 10 in its normal position radially to the central axis 6 back.

The grinding wheel 1 consists in its basic structure of abrasive grain 11, which is bound by means of a binder, usually phenolic resin. From Fig. 2 and 3, the basic structure of the roughing wheel results 1. Thereafter, the grinding wheel 1 on its underside 12 and on its upper side 13 each have a reinforcement 14 and 15, respectively, by a soaked with the binder of the abrasive grain 11 tissue , in particular a glass fabric, is formed, which is so soaked in the rule with phenolic resin. It is followed in each case inwardly to a layer 16 or 17 of abrasive grain 11 with binder, which in turn on their adjacent sides reinforcements 18, 19, which may be equal to the reinforcements 14, 15. The reinforcements 14, 15, 18, 19 and the layers 16, 17 are constructed so that they concentric to the central axis 6, the central opening 4 limit. Between the two inner reinforcements 18, 19 is an annular Separating layer 20 is arranged, which is formed in the present case of two adjacent intermediate layers 21, 22, which consist for example of paper, plastic film or the like. As a rule, this separating layer 20 does not extend to the outer circumference 9 of the grinding wheel 1, but has an outer diameter D ₂₀ for which the following applies in relation to the outer diameter D _{1 of} the grinding wheel 1: 0.97 ≦ D ₂₀ / D ₁ ≤0,99. The outer diameter D _{1 of} the grinding wheel 1 is in the range of 100 to 300 mm. Inwardly, the separating layer 20 extends over the working region 23 of the grinding wheel 1, ie radially to the axis 6 inwardly over a range which can be consumed during use, for example in accordance with FIG. This work area 23 extends over 60 to 100 percent of the flat area 24 of the grinding wheel when viewed from the outer circumference 9, wherein the flat area 24 is located radially outside the inner clamping area 26 offset by a crank 25.

The grinding wheel 1 may have on its outer sides still a lower paper cover 27 and an upper paper cover 28, wherein the upper paper cover 28 is usually formed at the same time as a label. The centering ring 5 is placed from above.

As is apparent from Fig. 3, the grinding wheel 1 is formed in a compressed state so that the bonded abrasive grain 11 also passes through the inner reinforcements 18, 19, although in the production according to FIG. 2, the inner reinforcements 18, 19 and the release layer 20 directly be placed over each other. The bonded abrasive grain is also located in the small radially outer region 29 outside of the release layer 20. The reason why the release layer 20 does not extend beyond the full outer diameter D ₁ and consequently formed radially outward of the bonded abrasive grain filled region 29 is primarily in manufacturing reasons. A certain tolerance compensation in the production makes this necessary. At the beginning of a grinding process, the bonded abrasive grain of this area 29 is abraded, so that then the release layer 20 is exposed. For the inner diameter d _{20 of} the separating layer 20, in comparison with the outer diameter D _{1 of} the grinding wheel 1, 0.2 ≦ d ₂₀ / D ₁ ≦ 0.65.

If - as shown in Fig. 3 - only one release layer 20 is present, then this is in the middle thickness range of the grinding wheel, wherein for the distance b of the separating layer 20 from the upper side 13 of the grinding wheel 1 in relation to the total thickness c Grinding wheel 1 is: 0.33 ≤b / c ≤0.66. In other words, this means that in the presence of only one separating layer 20, this is located in the middle third of the axial extent of the grinding wheel 1.

As is apparent from Fig. 4, two separating layers 20 may be present, which are arranged symmetrically over the thickness c. Here, too, each separating layer 20 is bounded on both sides by a reinforcement 18, 19. The same applies to the embodiment according to FIG. 5, where three separating layers 20 are provided.

A separating layer 20 'can also consist not only of two intermediate layers 21, 22 but, as shown in FIG. 6, of only one relatively thick intermediate layer 30, which consists of a material which, in the area of the attack, forms when the bending occurs 10 caused approximately radially directed to the axis 6 shearing forces in itself and thereby dissolved practically in two intermediate layers. Such properties have, for example, cardboard or paper. In principle, it is also conceivable that the only one intermediate layer 30 made of a material, for example a suitable plastic material, which undergoes only a slight bond with the binder, as a rule phenolic resin, so that in the described bending stress, the intermediate layer 30 from the abrasive grain 11 and der Armierung 18 or 19 breaks off. Otherwise, the structure of such a grinding wheel 1 'is the same as that already described.

When using the roughing grinding wheel 1, 1 'according to the invention in the manner already described at the outset, first the radially outer region 29 is worked off. If the separating layer 20 or 20 'is exposed on the outer circumference 9, then the described embodiment of the separating layer or separating layers 20 or 20' causes the grinding wheel 1 or 1 'has the behavior of several packetized grinding wheels, but the strength and Stability of the grinding wheel as a compact grinding wheel within the separating layer 20 in the region of the crank 25 and in the clamping region 26 is maintained. The work areas 23 of the grinding wheel 1, 1 'defined by the radial extension of the separating layer 20 or 20' can move radially relative to one another and thus resiliently deflect under the axial forces. The amplitude of the oscillation occurring due to the bending in the attack area 10 and the subsequent recovery is thereby greatly reduced compared with grinding wheels formed continuously as a composite grinding wheel. This causes a softer and less vibration sanding. For the thickness e of a release layer 20 or 20 'applies: 0.1 mm ≤e ≤2.0 mm, the larger thickness ranges will occur primarily in single-layer liners 30, if they are made of cardboard.

Claims (8)

1. A rough-grinding wheel, comprising

   - abrasive grit (11) bonded by binder;

   - reinforcement (15, 14) respectively adjoining the top (13) and the bottom (12);

   - further reinforcements (18, 19) embedded in the abrasive grit (11);

   - a central passage (4);

   - a center line (6);

   - a periphery (9);

   - a radially outer working area (23);

   - a thickness c and

   - an outside diameter D₁, with 10c ≤ D₁ applying to the outside diameter D₁ in relation to the thickness c;

   characterized
   in that it comprises at least two layers (16, 17) of bonded abrasive grit (11) which are reinforced bilaterally in a direction of the center line (6) by respective reinforcement (15, 19, 14, 18) and
   in that between adjacent layers (16, 17), provision is made for an annular separating layer (20, 20') with an outside diameter D₂₀ and an inside diameter d₂₀ and a thickness e, which extends as far as into the proximity of the periphery (9) and defines the working area (23), separating from each other the adjacent layers (16, 17) while supporting them one relative to the other in the direction of the center line (6) and
   in that the separating layer (20, 20') spans the working area (23), with 0.2 ≤ d₂₀/D₁ ≤ 0.65 applying.
2. A rough-grinding wheel according to claim 1, characterized in that the at least one separating layer (20) is comprised of two intermediate layers (21, 22) that rest on one another.
3. A rough-grinding wheel according to claim 1, characterized in that the at least one separating layer (20') is comprised of an intermediate layer (30) which tears open or off radially of the center line (6) under shearing action.
4. A rough-grinding wheel according to one of claims 1 to 3, characterized in that 0.1 mm ≤ e ≤ 2.0 mm applies to the thickness (e) of the at least one separating layer (20, 20').
5. A rough-grinding wheel according to one of claims 1 to 3, characterized in that one to three separating layers (20, 20') are provided.
6. A rough-grinding wheel according to one of claims 1 to 5, characterized in that if there is only one separating layer (20, 20'), it is disposed in the mid third of the wheel (1, 1') as seen in a direction of the center line.
7. A rough-grinding wheel according to one of claims 1 to 6, characterized in that 100 mm ≤ D₂₀ ≤ 300 mm applies to the outside diameter D₂₀ of the grinding wheel (1, 1').
8. A rough-grinding wheel according to one of claims 1 to 7, characterized in that 4 mm ≤c ≤ 12 mm applies to the thickness c of the grinding wheel.

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