RESIN-BONDED GRINDING DISK
A resin-bonded grinding disk for use on a hand-held power tool includes a clamping flange. The resin-bonded grinding disk includes a top side, an underside arranged opposite to the top side, a grinding disk surface area, a central cutout configured to hold the grinding disk in the clamping flange, a first reinforcement fabric arranged on the top side, and a second reinforcement fabric arranged on the underside. The first reinforcement fabric comprises a first reinforcement fabric surface area which substantially corresponds to the grinding disk surface area. The second reinforcement fabric comprises a second reinforcement fabric surface area which is smaller than the grinding disk surface area.
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This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/EP2014/069835, filed on Sep. 17, 2014 and which claims benefit to German Patent Application No. 10 2013 110 237.9, filed on Sep. 17, 2013. The International Application was published in German on Mar. 26, 2015 as WO 2015/040083 A1 under PCT Article 21(2).
FIELDThe present invention relates to a resin-bonded grinding disk, in particular a cutting-off disk or a roughing disk.
BACKGROUNDResin-bonded grinding disks are used to machine workpieces by cutting (cutting-off disks) or roughing (roughing disks). They consist, for example, of a resin/reinforcement fabric composite in which abrasive grains are embedded, wherein the abrasive grains effect the subtractive removal of the material from the workpiece. A surface machining of a workpiece is possible with roughing disks. The material of roughing disks is thicker than that of cutting-off disks due to the relatively high lateral load on the surfaces. Roughing disks are additionally always offset to further increase stability. By contrast, cutting-off disks are relatively thin to be able to provide cuts that are as narrow as possible.
Known resin-bonded grinding disks are manufactured in a manufacturing mold. The bottom of the manufacturing mold has hitherto been designed with a laminated reinforcement fabric to obtain a surface that is as smooth as possible. A mixture of abrasive grains, resins, and fillers is then poured into the manufacturing mold, wherein the resin-bonded reinforcement fabric can be interlaced with further reinforcement fabrics. A further reinforcement fabric terminates the mixture at the top. The material is then pressed.
The main purpose of the reinforcement fabric is to provide stability and thereby also the safety of the grinding disk. Safety is of particular importance, in particular in hand-held machines, since the operator, in contrast to stationary machines, is inevitably located in the immediate vicinity of the grinding disk during machining. Non-optimal guidance of the machine is always to be expected due to manual guidance. Sudden lateral forces, which even the very narrow cutting-off disk must withstand, can therefore arise. The reinforcement fabric is, however, comparatively expensive.
SUMMARYAn aspect of the present invention is to provide an improved resin-bonded grinding disk which reduces the amount of reinforcement fabric and is thus less expensive to produce.
In an embodiment, the present invention provides a resin-bonded grinding disk for use on a hand-held power tool comprising a clamping flange. The resin-bonded grinding disk includes a top side, an underside arranged opposite to the top side, a grinding disk surface area, a central cutout configured to hold the grinding disk in the clamping flange, a first reinforcement fabric arranged on the top side, and a second reinforcement fabric arranged on the underside. The first reinforcement fabric comprises a first reinforcement fabric surface area which substantially corresponds to the grinding disk surface area. The second reinforcement fabric comprises a second reinforcement fabric surface area which is smaller than the grinding disk surface area.
The present invention is described in greater detail below on the basis of embodiments and of the drawings in which:
The quintessence of the present invention is that the grinding disk according to the present invention has as few reinforcement fabrics as possible, with one on the top side and one on the underside of the grinding disk. Each reinforcement fabric initially serves as a support for the introduction of torque from the clamping flange into the grinding disk. In this case, it is important that each reinforcement fabric projects into the region of the grinding disk at which clamping with the clamping flange takes place. In order to pass the torque as far as the radially external regions of the grinding disk, at which machining usually takes place, it is then sufficient for only a single reinforcement fabric to support the transfer of the torque to that location. A second reinforcement fabric is there largely superfluous and can be dispensed with. The minimum requirement for the reinforcement fabric therefore exists, i.e., two reinforcement fabrics radially on the inside, and one reinforcement fabric radially on the outside. In other words, the second reinforcement fabric covers only the radially internal region, but not the radially external region. Depending on the configuration, up to about 35% of the reinforcement fabric can thus be dispensed with per disk. This results in a considerable cost-saving potential. This also includes, in principle, disks in which the surface area of the first reinforcement fabric is slightly smaller than the nominal diameter of the disk, in particular for manufacturing reasons.
It is important that the first reinforcement fabric reinforce the disk substantially over its entire area so that the radially external regions are also correspondingly stabilized. It has been found, in particular in the case of roughing disks, that these crumble in the peripheral region if at least one layer of reinforcement fabric is not there provided at least over the entire area. The first reinforcement fabric therefore in particular has a circular shape. By contrast, the second reinforcement fabric must only be arranged in the radially internal region. A circular shape is here not important so that other shapes are also conceivable. For the second reinforcement fabric, it is therefore possible to choose shapes which allow for a waste-free production, for example, rectangular shapes, interlocking shapes, star shapes, or triangular shapes. The surface area is here understood to essentially be the area which is taken up by the disk as seen in the axial direction, without cutouts, for example, the fastening cutout, being included (the calculation uses (D/2)2×π). A diameter of the first reinforcement fabric can here correspond to the nominal diameter of the grinding disk. A diameter of the second reinforcement fabric is much smaller than the nominal diameter of the grinding disk, in particular, at least 10%, for example, at least 20%, or, for example, at least 40% smaller than the nominal diameter. The surface area of the second reinforcement fabric can, for example, also be much smaller, for example, at least 15%, for example, at least 20%, or, for example, at least 50% smaller, than the surface area of the grinding disk.
In an embodiment of the present invention, the grinding disk can, for example, only comprise the first and the second reinforcement fabric as reinforcement fabrics. This arrangement is sufficient for a large number of applications. The quantity of reinforcement fabric to be employed is here greatly reduced compared with previous solutions, with the grinding disk being covered over its entire surface with at least one layer. This possibility is applicable to cutting-off disks and roughing disks, in particular to roughing disks which have a thickness of at most 10 mm.
In an embodiment of the present invention which is in particular applicable on roughing disks, the grinding disk can, for example, only have the first reinforcement fabric, the second reinforcement fabric, and a third reinforcement fabric as reinforcement fabrics. This variant is in particular applicable for fairly thick roughing disks having a thickness of the roughing disk 9″ of at most 10 mm. Conventional roughing disks of this size have hitherto been produced with much more reinforcement fabric.
In the case of the roughing disks, the first reinforcement fabric, i.e., the one with the large area, can, for example, be arranged on that side of the roughing disk which faces the power tool, i.e., the top side. In other words: the second reinforcement fabric, i.e., the one with the smaller area, can, for example, be arranged on that side of the roughing disk on which the disk is in contact with the workpiece to be machined, i.e., on that side of the roughing disk that faces the roughing face, namely, the underside. This is because the reinforcement fabric tends to be obstructive on roughing contact with the workpiece. The reinforcement fabric does not, in contrast, disrupt the roughing operation on the top side.
A resin-bonded cutting-off disk is in particular a non-offset and flat cutting-off disk. The thickness of a cutting-off disk, which decisively defines the cutting width, is in particular at most 4 mm, for example, at most 3 mm.
The present invention furthermore relates to a method for producing a resin-bonded grinding disk of the abovementioned type. The particular feature of the method is that a surface layer is first laid on the bottom of the pressing mold, in particular a paper fabric or a nonwoven fabric, on which the reinforcement fabric to be laid at the bottom is placed. In particular in the case in which the second reinforcement fabric is laid at the bottom, said second reinforcement fabric does not completely line the bottom, as in conventional grinding disks, on account of its small dimensions. The lining of the bottom is then taken over by this additional surface layer. This prevents the mixture of abrasive grain, resin, and fillers from sticking to the bottom of the mold, thereby making it difficult or even impeding the removal of the finally pressed disk. The surface layer likewise has a circular outer contour and a surface area which largely corresponds to the surface area of the grinding disk.
The present invention is explained in more detail below with reference to the drawings.
These stresses are primarily absorbed via two reinforcement fabrics 11, 12. According to the present invention, provision is made for exactly two such reinforcement fabrics 11, 12 in cutting-off disk 9′, the first reinforcement fabric 11 being on the underside 18, and the second reinforcement fabric 12 on the top side 17. These two reinforcement fabrics 11, 12 project into that inner radial region 19 of the cutting-off disk 9′ in which clamping via the clamping flange 4 also takes place. In this respect, the torque is introduced substantially directly into the reinforcement fabric 11, 12. It is possible, however, for the reinforcement fabric 11, 12 to be covered on the top side 17 or underside 18 by a thin layer of yet another material so that the clamping flange 4 does not bear directly against the reinforcement fabric 11, 12.
The first reinforcement fabric 11 is formed in a circular manner and has a diameter D1 which corresponds to a nominal diameter N of the cutting-off disk 9′. The surface area of the first reinforcement fabric 11 also corresponds to the surface area of the cutting-off disk 9′. The second reinforcement fabric 12 is formed in a smaller manner in terms of its diameter and essentially has a diameter D2 of only 55% of the nominal diameter N of the cutting-off disk 9′. The second reinforcement fabric 12 essentially has the purpose to generally support the conduction of the torque from the clamping flange 4 into different regions of the disk. For the further distribution of the torque into the circumferential region, however, it has been found sufficient for this to be supported by only one reinforcement fabric, specifically, the first reinforcement fabric. The advantage compared with conventional resin-bonded cutting-off disks thus resides in the saving of material since only one large layer and one small layer of reinforcement fabric needs to be used rather than two large layers of reinforcement fabric.
The reduction to only one reinforcement fabric, which extends as far as the outer circumference, also has the following advantage. Although the reinforcement fabric can in principle introduce stability into the disk, it does not have any abrasive action. The robustness of the reinforcement fabric can much rather have a disadvantageous effect on the cutting operation, for example, the movement of the disk being braked by the fabric. This also in principle applies for roughing. As a result of the reduction in the size of the second disk, only one reinforcement fabric which can “disrupt” the actual cutting operation now bears against the outer circumference.
A mixture 10 of synthetic resin, fillers, and abrasive grains is provided between the two reinforcement fabrics 11, 12, as is also known for conventional disks. The thickness B of the cutting-off disk 9′ is approximately 2 mm and is suitable for the production of very thin cuts.
In hand-held power tools, the cutting-off disk 9′ is frequently pushed axially as a result of non-optimal operation, which can create a point lateral force S. This lateral force S creates a bending load on the cutting-off disk 9′, the tensile side of which is located on the underside 18 of the cutting-off disk 9′. The side to be provided with the first, i.e., the more extensive, reinforcement fabric can, therefore, for example, be on the underside 18, which represents the axial side (with respect to the drive shaft) of the cutting-off disk 9′, facing away from the operator. In contrast thereto, an axial pulling on the part of the operator occurs more rarely so that the reduced reinforcement fabric on the top side 17 is unimportant with regard to faulty operation. Inverted mounting of the cutting-off disk 9′ on the angle grinder 1 is, however, in principle also conceivable.
Various non-exhaustive possible geometries are presented in
It is relevant, however, that the first reinforcement fabric 11 always be formed in a circular manner and covers substantially the entire disk.
The production method is explained by way of
The present invention is not limited to embodiments described herein; reference should be had to the appended claims.
LIST OF REFERENCE NUMERALS1 Angle grinder
2 Housing
3 Drive shaft
4 Clamping flange
5 Cutout
6 First handle
7 Second handle
8 Power line
9 Grinding disk
9′ Cutting-off disk
9″ Roughing disk
10 Mixture
11 First reinforcement fabric
12 Second reinforcement fabric
13 Third reinforcement fabric
14 Pressing mold
15 Cover
16 Surface layer
17 Top side
18 Underside
19 Radially internal region of the disk
20 Grinding face
N Nominal diameter of the disk
D Diameter of the reinforcement fabric
S Lateral force
F Pressing force
E Plane of the machining face
B Thickness of the grinding disk
Claims
1-11. (canceled)
12. A resin-bonded grinding disk for use on a hand-held power tool comprising a clamping flange, the resin-bonded grinding disk comprising:
- a top side;
- an underside arranged opposite to the top side;
- a grinding disk surface area;
- a central cutout configured to hold the grinding disk in the clamping flange;
- a first reinforcement fabric arranged on the top side, the first reinforcement fabric comprising a first reinforcement fabric surface area which substantially corresponds to the grinding disk surface area; and
- a second reinforcement fabric arranged on the underside, the second reinforcement fabric comprising a second reinforcement fabric surface area which is smaller than the grinding disk surface area.
13. The resin-bonded grinding disk as recited in claim 12, wherein the resin-bonded grinding disk only consists of the first reinforcement fabric and the second reinforcement fabric as reinforcement fabrics.
14. The resin-bonded grinding disk as recited in claim 12, wherein,
- the resin-bonded grinding disk further comprises a third reinforcement fabric arranged between the first reinforcement fabric and the second reinforcement fabric, the third reinforcement fabric comprising a third reinforcement surface area which is smaller than the grinding disk surface area; and
- the resin-bonded grinding disk only consists of the first reinforcement fabric, the second reinforcement fabric, and the third reinforcement fabric as reinforcement fabrics.
15. The resin-bonded grinding disk as recited in claim 14, wherein,
- the second reinforcement fabric further comprises a second reinforcement fabric diameter,
- the third reinforcement fabric further comprises a third reinforcement fabric diameter, and
- at least one of the second reinforcement fabric diameter and the third reinforcement fabric diameter is less than 80% of the grinding disk surface area.
16. The resin-bonded grinding disk as recited in claim 15, wherein at least one of the second reinforcement fabric diameter and the third reinforcement fabric diameter is less than 60% of the grinding disk surface area.
17. The resin-bonded grinding disk as recited in claim 12, wherein,
- the first reinforcement fabric further comprises a first reinforcement fabric diameter,
- the resin-bonded grinding disk further comprises a grinding disk nominal diameter, and
- the first reinforcement fabric diameter corresponds to the grinding disk nominal diameter.
18. The resin-bonded grinding disk as recited in claim 12, wherein the resin-bonded grinding disk is a cutting-off disk.
19. The resin-bonded grinding disk as recited in claim 18, wherein the cutting-off disk is an non-offset flat cutting-off disk comprising an overall thickness of at most 4 mm.
20. The resin-bonded grinding disk as recited in claims 12, wherein the resin-bonded grinding disk is a roughing disk.
21. The resin-bonded grinding disk as recited in claims 20, wherein the roughing disk is an offset roughing disk.
22. The resin-bonded grinding disk as recited in claim 12, wherein,
- the top side comprises an offset portion, and
- the first reinforcement fabric is also arranged on the offset portion.
23. The resin-bonded grinding disk as recited in claim 12, wherein,
- the resin-bonded grinding disk further comprises a grinding face, and
- the second reinforcement fabric is arranged on a side of the resin-bonded roughing disk that faces the grinding face.
24. An arrangement comprising:
- a hand-held power tool; and
- the resin-bonded grinding disk as recited in claim 12.
25. The arrangement as recited in claim 24, wherein, the resin-bonded grinding disk is a roughing disk which is mounted on the hand-held power tool so that the first reinforcement fabric faces an operator of the power tool and/or so that the second reinforcement fabric is assigned to a workpiece to be machined.
Type: Application
Filed: Sep 17, 2014
Publication Date: Aug 11, 2016
Applicant: RHODIUS SCHLEIFWERKZEUGE GMBH & CO. KG (BURGBROHL)
Inventors: GUNNAR BUEHLER (NICKENICH), MARTIN E. DAVIES (HAIGER)
Application Number: 15/022,211