The invention relates to a blade for cutting and/or grinding in accordance with the preamble of claim 1.

EP 1 103 347 Al describes a blade or a tool insert for cutting, slitting or grinding, in which a plurality of arrow-shaped apertures are arranged between a radially inner region for fixing and a radially outer active region, all the apertures being arranged radially at the same level. For all radii, the apertures have substantially a constant length in the circumferential direction, independently of the size of the respective radius or circumference. A region which appears to be translucent when the blade is rotated rapidly on account of the apertures would therefore have a translucence which decreases continuously from the inside to the outside. It is the object of the invention to specify a blade for cutting and/or grinding which makes simple and effective work monitoring possible.

According to the invention, this object is achieved with the characterizing features of claim 1 for a blade which is mentioned at the outset. The position of the region of homogeneous translucence appears to be well defined in the case of a corresponding observation from the side of the rotating blade by an operator.

For example, the operator can estimate a penetration depth of the blade quickly and simply as a result. This is assisted by the effect that human perception identifies the edges of a shape of uniform brightness in a particularly satisfactory manner.

In the context of the invention, a blade for cutting and/or grinding is to be understood to mean every flat or disk-shaped, rotating tool, in particular cutting blades, for example with incorporated diamonds or other hard materials, saw blades, for example with saw teeth as active region, grinding blades with grinding edging on end faces and/or side faces of the active region, and the like. The closed apertures are often arranged outside an active region or radially further to the inside, in particular between the receiving region and the active region. In principle, however, the apertures can also extend into the active region.

The translucence for a given radius of a circumferential circle about a center of rotation is understood here to be the sum of the interrupted circumference, divided by the circumference. The translucence will in practice usually be far below 50%, just to ensure the mechanical stability of the blade.

In one optimized embodiment of the invention, the translucence in the homogeneous region has a range of fluctuation of less than 15%, preferably of less than 10%. This ensures satisfactory localization with regard to the perception by the operator. In a generally advantageous way, the radial width DH of the homogeneous region is not less than a fifteenth, preferably not less than a tenth of a maximum radius of the blade. As an alternative or in addition, the width DH of the homogeneous region is not more than a quarter, preferably not more than a fifth of a maximum radius of the blade. Overall, this ensures sufficient mechanical stability of the blade, even with regard to natural frequencies which occur. In one preferred embodiment of the invention, at least one edge region of non-homogeneous translucence adjoins the homogeneous region radially to the outside or radially to the inside. Here, the edge region particularly preferably extends over a radial width DR which is not more than a fifth, in particular not more than a tenth of the radial width DT of the translucent region. Overall, this ensures sufficient localization of the translucent region, a large multiplicity of shapes for the apertures being made possible, in particular, by the non-homogeneous edge regions.

In one particularly preferred embodiment of the invention, it is provided that, over the width DH of the homogeneous region, the aperture has a substantially constant opening angle on each circular arc over a center of rotation. As a result, a single, individual aperture already satisfies the criterion of homogeneous translucence.

As an alternative or in addition to this, it can also be provided, however, that the homogeneous translucent region is produced by the superimposition of the translucences of a plurality of, in particular overlapping, apertures which do not per se satisfy the criterion of homogeneous translucence.

In the interest of a simple construction, the closed aperture in the homogeneous region is formed from adjacent, radially infinite segments of a substantially constant opening angle. Here, the constant opening angle satisfies the criterion of homogeneous translucence. It is preferable but not necessary that the shaping takes place with the formation of a consistent or consistently differentiable border line of the aperture.

In one embodiment which is expedient and esthetically pleasing, the aperture has an arrow shape and/or hook shape with two limbs. Here, a tip of the arrow shape or hook shape can preferably point in the circumferential direction. A particularly pleasing shape is achieved here if the tip of the arrow and/or hook is rounded.

In one embodiment which is preferred from design aspects and is mechanically stable, the homogeneous region is formed exclusively by a plurality of, preferably between two and thirteen, identical apertures . Further advantages and features of the invention result from the exemplary embodiment which will be described in the following text and from the dependent claims.

In the following text, one preferred exemplary embodiment of the invention will be described and will be explained in greater detail using the appended drawings, in which: fig. 1 shows a plan view which is substantially to scale of a blade according to the invention, fig. 2 shows an enlargement of a detail of the blade from fig. 1, and fig. 3 shows an illustration of one preferred design principle of a blade according to the invention .

In the present case, the blade according to the invention which is shown in fig. 1 is configured as a cutting blade with a central receiving region 1, which comprises a hole, and a radially outer active region 2. The active region 2 has oblique slits 3 which are open to the outside and is fitted with diamond cutting elements 4.

The receiving region 1 serves for clamping the blade into a rotary drive, for example a hand-held power tool. Here, the hole of the receiving region 1, the center point of which corresponds to the center of rotation of the blade, is covered by a holder and cannot be seen during operation.

A plurality of, in the present case three, closed apertures 5 are arranged between the receiving region 1 and the active region 2. The apertures are at an identical angular spacing from one another. In the present case, the apertures 5 are congruent and are arranged in each case at the same radial spacing from the center of rotation. The orientation of the congruent apertures 5 with regard to a circumferential direction is in each case identical.

The apertures 5 have the shape of an arrow or hook with a rounded tip 5a and two limbs 5b, 5c which emanate therefrom. Here, the tip 5a points substantially in the rotational direction. The limbs 5b, 5c are shaped differently to one another, in this case and preferably .

As fig. 2 shows in detail, the aperture 5 has a homogeneous region 6 which extends in the radial direction over a width DH, an overall width DT of the region which is translucent when rotated being somewhat greater than DH .

When the blade is rotated correspondingly rapidly, the apertures 5 bring about a region or circular ring which appears to be translucent and has the width DT, the translucence being uniform or homogeneous over the width DR. This is brought about by the fact that an accumulated opening angle of the apertures 5 is constant for a given radius within the homogeneous region. In the present case, the apertures are congruent, oriented identically and in the same radial position, with the result that the shape of the translucent region would be produced identically by a single one of the apertures. In the present example, the two further apertures 5 correspondingly bring about only an increase in the translucence, but not a change in the relative translucence distribution. In other embodiments which are not shown, it can be provided that the desired relative translucence distribution is produced only by the summation of the effects of a plurality of apertures.

Accordingly, in the present case, the apertures 5 in each case have a central region 6, over which their opening angle about the center of rotation is constant for every radius.

The central region 6 is adjoined in each case by an inner edge region 7 and an outer edge region 8 which have a non-constant opening angle and therefore, when rotated rapidly, bring about a respective edge region of non-homogeneous translucence. In the present case, the edge regions 7, 8 have the same radial width DR. Said edge regions are narrow in comparison with the homogeneous region 6. In the present case, it holds that DR is less than 8% of the width of the translucent region DT . In practice, edge regions 7, 8 of this type cannot be seen per se.

Fig. 3 clarifies the properties of the different regions 6, 7, 8 of the aperture 5. Here, in each case line segments 9 which represent the same opening angle are shown for a plurality of radii. A line segment which lies radially further to the outside therefore has a proportionally greater length than a line segment which lies further to the inside. In the homogeneous region 6 of the aperture 5, the ends of the line segments therefore form a border line 10 of the aperture 5. In the present case, the border line is consistently differentiable . In other embodiments, jumps or kinks in the border line are also conceivable.

Furthermore, in each case one line segment is shown in the non-homogeneous edge regions 7, 8 which are discernibly overlapped by the segment. The line segments 9 can be considered to be radially infinitely narrow circular ring segments of a constant opening angle, from which the aperture is built up.

A method for designing an aperture with a region of homogeneous translucence can therefore be carried out in such a way that first of all a desired part border line is defined, after which the opposite border line is obtained by applying the segments.