US 20080003929 A1
The device for cutting and grinding contains a drive unit, a drive spindle, and means for chucking a rotating tool onto the drive spindle. Vibration damping means are provided between the tool and the chucking means. The vibration-damping means are provided in the form of a coating made of elastic material applied to the chucking means or to the tool or are provided in the form of one or more discs, which are made of elastic material and which are inserted between the tool and the chucking means.
1. Device for cutting and grinding with a drive unit (10), a drive spindle (14) and means (16, 24) for clamping a rotating tool (20) onto the drive spindle (14), wherein vibration-damping means are provided between the tool (20) and the clamping means (16, 24),
characterized in that the vibration-damping means are provided in the form of a coating of elastic material on the clamping means (16, 24) or the tool (20) or in the form of one or more disks (36) of elastic material to be inserted between the tool (20) and the clamping means (16, 24).
2. Device according to
3. Device according to
4. Device according to
5. Device according to
6. Device according to one of
7. Device according to
8. Device according to
9. Device according to
10. Clamping device for clamping a cutting or grinding tool onto a drive spindle (14), with two clamping elements (16, 24) with vibration-damping means,
characterized in that the vibration-damping means are a coating (34) of elastic material on the clamping elements (16, 24).
11. Clamping device according to
12. Clamping device according to
13. Tool for use with a device according to
characterized in that the inner edge of the fixing hole (28) of the tool (20) has a coating (34) made of the elastic material.
14. Tool according to
The invention relates to a device for cutting and grinding, e.g. an angle grinder, with a drive spindle on which a rotating tool, such as a grinding, roughing or cutting disk, is fixed. The fixing takes place by means of two clamping elements, in general a clamping flange and a clamping nut. The clamping flange is formed in a single piece with the drive spindle or sits loose but rotation-resistant on the latter. The clamping nut is screwed onto the end of the drive spindle. The tool is clamped fast between the clamping flange and the clamping nut. The clamping elements can also be a lower and an upper clamping flange which are clamped against each other by means of a nut.
The invention also relates to a clamping device and a rotating tool, such as a grinding, cutting or roughing disk.
When using angle grinders without vibration-damping elements, vibrations occur which are transmitted via the grips, generally a main and additional hand grip, to the user's arms. Prolonged working with angle grinders can therefore lead to damage to health, such as feelings of numbness in the lower arm. The main and additional hand grips of angle grinders therefore sometimes contain vibration-damping means.
From DE-OS 26 32 652 a grinding disk is known consisting of at least two abrasive plates connected to each other, which are connected to each other by means of a polymer layer arranged between them. Vibrations are to be reduced thereby.
From DE-GM 76 28 082 it is known to insert a disk ring of elastic material between the grinding disk and each of the two clamping flanges. The grinding disk sits on the drive spindle with loose fit. Vibrations are likewise reduced thereby. A similar arrangement is also known from U.S. Pat. No. 3,566,547.
WO 00/27590 describes a clamping device for grinding disks, wherein a metal intermediate ring which is provided with a damping layer of elastic material is arranged between the clamping flange or the clamping nut and the grinding disk. The damping layer extends in both radial and axial direction.
From JP 95 118 376 a vibration-damped grinding disk is known which is connected to the shank by means of an arrangement comprising one soft and one hard damping element which lie laterally against the grinding disk.
From JP 56 163 882 a grinding stone is known which is fixed by means of sleeve flanges to a central damping wheel of elastic material which is in turn fixed by means of clamping flanges to a mandrel on which the drive spindle sits.
The problem underlying the invention is to reduce in a simple manner to the greatest possible extent health-damaging vibrations in the hands of the user of a hand-operated cutting or grinding device.
According to the invention this problem is solved by arranging an elastic layer between the clamping elements and the tool.
The layer is preferably provided on both sides of the rotating tool and inside the fixing hole with which the tool on the spindle is clamped fast. The grinding tool thus has no direct contact with the clamping elements, i.e. the spindle, the clamping flange and the clamping nut, and all contact or clamping surfaces are provided with the elastic material. The transmissions of the vibration from the grinding tool to the drive spindle and thus the drive unit are thus already reduced at the start of the transmission path, with the result that the vibrations are already markedly damped before they are transmitted to the drive unit.
The layer of elastic material can be provided in each case on one or both of the abutting clamping surfaces of the tool and the clamping elements.
The layer of elastic material can be a coating on the tool or on the clamping elements. The layer of elastic material can also be a separate component which is arranged between the tool and the clamping elements. Both possibilities can also be combined, for example by providing the inner edge of the fixing hole of the tool with a coating and by providing a thin disk of the elastic material on one or both sides of the tool between the tool and the clamping flange or the tool and the clamping nut.
The clamping elements (clamping flanges and clamping nut) have a central hole, with which they sit on the drive spindle. This hole usually has, on the side of the clamping surfaces, a collar on which the rotating tool sits with its hub or fixing hole. The cylindrical outside of the collar or the inside of the hub hole also have the coating of elastic material.
The elastic layer or coating preferably consists of a polyurethane elastomer, which is in particular characterized by high resistance to wear and abrasion, resistance to ozone, UV radiation, mineral oils and fats, e.g. Vulkollan®. The mould material used can have the following characteristic mechanical-physical values:
The material is not used as semi-finished product, but as mould material. A negative mould is produced which is filled with the mould material. During hardening the connection to the clamping flange or the clamping nut takes place with the aid of an adhesion promoter.
If the layer is a separate component, the connection to the clamping flange or the clamping nut is unnecessary.
In the case of a first particularly preferred version of the invention the clamping surfaces of the tool are not provided with a coating and only the clamping surfaces of the clamping flange and of the clamping nut including the periphery of the respective collar are provided with a coating. In this embodiment grinding disks with the usual measurements, in particular the usual hub hole diameter of 22.23 mm, can be used. The diameter of the collar of the clamping flange and of the clamping nut with no coating is reduced to the point where the usual diameter of 22.13 mm is then achieved with the coating. For this purpose the collars have an original diameter of e.g. 17.2 mm, and the coating has a thickness of 2.5 mm. A clamping device with two clamping elements formed in this manner is also a subject of the invention.
In a second version of the invention the clamping elements are not provided with a coating and the clamping surfaces on both sides of the tool and the inner edge of the hub hole of the tool are provided with a coating. The clamping flange and the clamping nut are thus unchanged. The hub hole of the tool then has e.g. a diameter of 25.4 mm without coating, which is then reduced by a coating 1.585 mm thick to 22.23 mm. The particular advantage of this version is that the clamping flange and the clamping nut have standard measurements and are thus unchanged. The tool coated in the manner described can therefore be used instead of conventional tools without the clamping flange or the clamping nut having to be replaced. A tool in which the clamping surfaces have on both sides in the region of the hub hole an elastic coating with raised sections is also a subject of the invention.
In a third version of the invention the inner edge of the hub hole of the tool is provided with a coating and the contact or clamping surfaces of the clamping flange and of the clamping nut are also provided with a coating. The clamping surfaces of the tool are not on the other hand provided with a coating. The clamping flange and the clamping nut each have a collar which extends into the hub hole of the tool, and the peripheral surfaces of these collars also have no coating in the region which projects over the coating of the clamping surfaces. In this case too there is the advantage that the clamping flange and the clamping nut can have standard measurements.
In a fourth version of the invention, similar to the third version, the inner edge of the hub hole of the tool is provided with a coating. The clamping surfaces of the tool and of the clamping flange and of the clamping nut have no coating however, and instead in each case a thin ring disk made of the elastic material is inserted between the clamping flange and the tool, and between the tool and the clamping nut. In this case too the clamping flange and the clamping can nut have standard measurements.
The coating of the clamping surfaces of the clamping flange and of the clamping nut or the coating provided instead of the areas of the tool surrounding the hub hole has a thickness of between 0.5 and 5 mm, preferably 1.5 to 2.5 mm. The coating of the inner edge of the hub hole of the tool or the coating provided instead, the collar of the clamping flange and of the clamping nut preferably has a thickness of approximately 2.5 mm.
In all four versions of the invention mentioned either the clamping flange and the clamping nut are thus formed such that a standard grinding disk with usual measurements can be clamped in, or the grinding disk is formed such that it can be clamped in by means of a standard flange and a standard clamping nut of usual measurements.
In all four abovementioned versions of the invention a clear damping of the vibrations is achieved by means of the elastic coating. A further reduction in the vibrations is possible by the coating having axially directed raised sections or being in the form of such raised sections. In the latter case the coating consists only of the raised sections. The raised sections do not then project from a flat coating, but are applied as individual, discrete surface pieces to one or both clamping elements, the tool or a disk inserted between them.
The contact surface between the clamping elements and the tool is reduced by means of the raised sections. The reduction is preferably at least 50 percent.
In a preferred embodiment the raised sections are formed as radial bearing ribs or bars, wherein at least three ribs or bars are present. If there are four clamping holes in the clamping nut, there are also expediently four bearing ribs. The ribs or bars are arranged with the same angular separation on the clamping surface and have a width of at least 1 mm and preferably between 1.5 and 5 mm. If the raised sections have another shape, their smallest cross-sectional measurement is also at least 1 mm.
The raised sections preferably have a height of 0.2 to 2.5 mm. If the raised sections are part of a flat coating, the coating preferably has a thickness of approximately 1 to 3 mm and the raised sections project approximately 0.5 mm from it. If the raised sections are discrete coatings of elastic material, they preferably have a height of approximately 1.5 to 2.5 mm. The bars of the clamping flange are generally higher than the bars of the clamping nut. For example, the bars of the clamping flange have a height of 2.5 mm, while the bars of the clamping nut have a height of only 1.5 mm.
The bearing ribs or bars can also be in the form of one or more concentric circles. In a particularly preferred embodiment the bearing ribs are in the form of spiral arms. In this case each spiral arm expediently extends over an angular range of 360° divided by the number of the spiral arms. If there are four spiral arms each spiral arm extends over an angular range of 90°, running within an angular range of 45° from the inside outwards and then in a further angular range of 45° along a circular line on the other edge of the clamping flange or the clamping nut. In this case the bearing ribs can have a height of e.g. 2.5 mm and a width of 2 mm. With this height the coating then consists only of the bearing ribs. Alternatively the bearing ribs can project with a smaller height of e.g. 0.5 mm from a flat coating, with the flat coating covering the whole clamping surface of the clamping flange or of the clamping nut and being able to have a thickness of e.g. 2 mm. If there are particularly wide bars or ribs (e.g. 5 mm) the ends lying on the edge of the ribs in the form of spiral arms are somewhat shortened by the clamping holes. Due to the greater utilization of space at the edge of the clamping flange the embodiment of the invention with ribs or bars in the form of spiral arms has a greater wear resistance and at the same time a better support of the tool (grinding disk) against tilting and wobbling.
The raised sections of the elastic coating can in principle be present on all areas of the clamping surfaces. In general, however, it is sufficient for them to be present on the surfaces lying normal to the axis of the drive spindle.
The tools can be straight or cranked, and the drive unit can have an electric motor, in particular a high-frequency motor, compressed-air motor or petrol-driven motor.
The invention is naturally particularly advantageous in the case of hand-operated devices for cutting and grinding.
Embodiment examples of the invention are explained in more detail with reference to the drawing. There are shown in:
The angle grinder schematically represented in
The tool 20 is a grinding disk, a cup wheel, a cutting disk, a roughing disk or the like. When working with such tools vibrations occur which are transmitted from the tool 20 to the drive unit 10 and via its hand grips 18 to the user. In order to reduce the transmission of the vibrations to the drive unit, a layer of elastic material is provided between the tool 20 and the clamping flange 16 and the clamping nut 24. There is therefore no direct undamped contact between the tool 20 and the clamping elements 16, 24.
In the second embodiment example shown in
FIGS. 8 to 16 show embodiment examples in which the clamping surface 30 of the clamping flange 16 and the clamping surface 32 of the clamping nut 24 have the coating 34. The clamping flange 16 and the clamping nut 24 in turn have a collar 26, around the periphery of which the coating 34 is raised. The tool 20 has no coating either in the hub hole 28 or in the areas surrounding the hub hole 28.
As mentioned at the outset, the clamping nuts can also be formed as upper clamping flanges, which are then clamped with a nut on the drive spindle against the tool and the lower clamping flange.
When the clamping nut 24 is screwed onto the drive spindle 14 the ribs 40 are in fact to a large extent compressed, so that the areas between the ribs 40 can also contact the edge of the hub hole of the tool 2. The contact pressure is higher in the area of the ribs 40, however, so that the clamping forces are primarily effective in the area of the ribs 40. The vibrations are thereby transmitted from the tool 20 to the drive spindle 14 and the drive unit 10 less than when there are clamping forces acting evenly on the clamping surfaces 30, 32.