Abrasive tool, in particular abrasive disc

Abstract

The invention relates to an abrasive tool (1), comprising a support body (2) and an abrasive layer (3) arranged on the support body (2). At least one through-opening (D) is formed in the support body (2) and is designed such that a workpiece can be observed during grinding. The at least one through-opening (D) is surrounded by the support body (2). The abrasive tool (1) has improved grinding properties and improved operating comfort.

Description

[0001] Grinding tool, especially grinding wheel

[0002] The invention relates to a grinding tool, in particular a grinding wheel.

[0003] A grinding tool in the form of a grinding wheel is known from WO 2018 / 149 483 A1. The grinding tool comprises a support body to which an abrasive layer is directly attached. To form the abrasive layer, the support body is first coated with an adhesive and then placed in an electrostatic field, so that the abrasive grains are moved toward the support body as a result of the electrostatic field and adhere there to the adhesive. Because the support body itself forms a base for the abrasive grains or the abrasive layer, the abrasive layer can be formed in any desired three-dimensional shape depending on the shape of the support body.

[0004] The invention is based on the object of creating a grinding tool with improved grinding properties and improved ease of use. The grinding tool should, in particular, be designed as a grinding wheel.

[0005] This object is achieved by a grinding tool having the features of claim 1. At least one through-opening is formed in the support body. The at least one through-opening or the respective through-opening thus lies within the support body. The circumferential contour of the support body is not changed, in particular by the at least one through-opening or the respective through-opening. The at least one through-opening or the respective through-opening enables an operator to observe the workpiece and the flying sparks during grinding. The at least one through-opening thus forms a respective viewing window or a respective viewing area onto the workpiece to be machined. This allows the operator to set a suitable angle of attack of the grinding tool relative to the workpiece and thus the size and / or position of a working point of the grinding tool more easily and quickly.The operator can thus use the grinding tool efficiently and with optimized wear.

[0006] Because the at least one through-hole or the respective through-hole is surrounded by the support body, the grinding tool or the support body exhibits a high degree of stability despite the at least one through-hole. This ensures smooth running of the grinding tool, so wear is not increased and the service life of the grinding tool is not impaired.

[0007] Furthermore, the at least one through-opening or the respective through-opening enables improved removal of grinding dust during grinding. Grinding dust generated during grinding can be removed into the environment more easily and quickly thanks to an air flow through the at least one through-opening or the respective through-opening, so that the grinding dust does not impair further grinding. This improves the grinding performance of the grinding tool.

[0008] The at least one through-opening or the respective through-opening can be designed symmetrically and / or asymmetrically. Preferably, the at least one through-opening or the respective through-opening is designed symmetrically with respect to at least one axis of symmetry.

[0009] The support body is in particular one-piece and / or in particular non-metallic and / or in particular electrically non-conductive. The support body comprises, for example, at least one material from the group consisting of vulcanized fiber, cotton, plastic, glass fibers, and carbon fibers. The support body is preferably a one-piece plastic support body. The plastic support body is produced, for example, by an injection molding process, an additive manufacturing process, or a subtractive manufacturing process. The support body is in particular three-dimensionally shaped. Preferably, the support body is curved in a radial direction and / or in a circumferential direction relative to a rotational axis of the grinding tool. The support body in particular has a geometrically determined shape and can have any shape or contour in an axial direction. In a grinding tool in the form of a grinding wheel, the support body is in particular designed as a support plate or support disk.Preferably, the support body of the grinding wheel is made of one piece plastic.

[0010] The grinding tool comprises a connecting element for clamping the grinding tool in a grinding tool drive and / or for rotating the grinding tool about a rotational axis by means of the grinding tool drive. The connecting element is designed, for example, as a hub or a shaft. The grinding tool designed as a grinding disc preferably comprises a hub as a connecting element, which is formed in a clamping region of the support plate. The grinding tool has a grinding side facing the workpiece to be machined and a drive side facing the grinding tool drive. The grinding layer comprises at least abrasive grains and a backing bond for securing the abrasive grains. The backing bond comprises a binder or adhesive. The binder serves to secure the abrasive grains. The grinding layer preferably comprises a top bond. The top bond is applied to the secured abrasive grains.The topcoat comprises a binder and, optionally, abrasive fillers. The binder of the topcoat can be identical or different from the binder used to secure the abrasive grains. The abrasive layer can be attached directly to the backing or indirectly via a backing layer. No abrasive layer is present in the area of ​​the at least one through-hole.

[0011] The grinding layer is, in particular, three-dimensionally shaped. The grinding layer is, in particular, curved in a radial direction and / or in a circumferential direction relative to a rotational axis of the grinding tool. The three-dimensional shape of the grinding layer corresponds, in particular, to a portion of a three-dimensionally shaped surface or an adhesive surface of the support body.

[0012] The abrasive grains preferably have a geometrically defined cutting edge. The abrasive grains are, in particular, triangular in shape. Preferably, at least some of the abrasive grains are aligned relative to one another and / or to an adhesive surface of the support body.

[0013] A grinding tool according to claim 2 ensures improved grinding properties and improved operating comfort. The interrupted central region is arranged in a radial direction between the clamping region and the closed outer region. A closed inner region can be arranged in the radial direction between the clamping region and the interrupted central region. The clamping region and / or the closed inner region and / or the interrupted central region and / or the closed outer region are in particular annular and / or arranged concentrically to the rotation axis.

[0014] The closed inner region surrounds the clamping area in the radial direction. The interrupted central region surrounds the clamping area and the closed inner region in the radial direction. The closed outer region surrounds the clamping area, the closed inner region, and the interrupted central region in the radial direction. The interrupted central region is interrupted in the radial direction and / or in the circumferential direction by at least one through-opening. The closed outer region stabilizes the interrupted central region and thus the support body or the grinding tool. This ensures that the grinding tool runs very smoothly, which does not increase wear on the grinding tool and does not impair its service life.

[0015] The interrupted central region begins in the radial direction with an inner end of the at least one through-opening and ends with an outer end of the at least one through-opening. The closed outer region has a dimension AA in the radial direction. The dimension AA corresponds to a distance of the at least one through-opening or the respective through-opening from a circumferential contour of the grinding tool or of the supporting body in the radial direction. The grinding layer is arranged in the interrupted central region on the supporting body, in particular over its entire surface. The grinding layer can be arranged at least partially in the closed inner region and / or in the closed outer region.

[0016] The grinding tool comprises, in particular, a connecting element arranged or formed in the clamping area. The connecting element is arranged or formed concentrically to the rotation axis.

[0017] A grinding tool according to claim 3 ensures improved grinding properties and improved operating comfort. Because the circumferential contour of the closed outer region has a consistent curvature direction, the support body has no recesses in the radial direction. This ensures high stability and smooth running. The closed outer region is, in particular, annular. The circumferential contour of the closed outer region or of the support body is, in particular, designed as a circle. The circumferential contour is, in particular, concentric with the rotational axis of the support body or of the grinding tool.

[0018] A grinding tool according to claim 4 ensures improved grinding properties and improved ease of use. The fact that the grinding layer is arranged in the interrupted central region creates an interrupted grinding region. The interrupted grinding region is interrupted in the radial direction and / or in the circumferential direction by the at least one through-opening. No grinding layer is present in the region of the at least one through-opening, so that the respective through-opening forms a viewing window or viewing area. The respective viewing window or viewing area thus interrupts the grinding layer in the radial direction and / or the circumferential direction.

[0019] The grinding layer can be arranged at least partially in a closed inner region and / or in a closed outer region of the support body, so that a closed inner grinding region and / or a closed outer grinding region is formed. The closed inner grinding region and / or the closed outer grinding region is in particular annular and arranged in the radial direction directly adjacent to the interrupted grinding region, so that the grinding layer is continuous in the radial direction outside the at least one through-opening. The grinding layer is preferably arranged over the entire surface in the closed inner region and / or in the closed outer region.

[0020] A grinding tool according to claim 5 ensures improved grinding properties and improved ease of use. The at least one reinforcement or the respective reinforcement is arranged in a border area at least partially around the associated through-opening. The at least one reinforcement or the respective reinforcement is arranged on a drive side of the grinding tool or the support body. The at least one reinforcement or the respective reinforcement surrounds the associated through-opening, in particular completely. The at least one reinforcement or the respective reinforcement is in particular formed integrally with the support body. The at least one reinforcement or the respective reinforcement reinforces and stabilizes the support body or the grinding tool in the area of ​​the associated through-opening. This ensures compliance with the relevant safety regulations and a high level of smooth running.Furthermore, the at least one reinforcement creates a negative pressure on the drive side of the grinding tool when the grinding tool rotates around the rotational axis. Due to the negative pressure on the drive side, an air flow is generated through the at least one through-opening or through the respective through-opening, which enables improved removal of grinding dust and has a cooling effect.

[0021] A grinding tool according to claim 6 ensures improved grinding properties and improved operating comfort. The respective front edge is arranged in front of the associated through-opening with respect to a predefined direction of rotation of the grinding tool, whereas the respective rear edge is arranged after the associated through-opening in the direction of rotation. The rear edge and the front edge are in particular part of a reinforcement that is formed in a border area around the associated through-opening on the support body. The front edge and the rear edge are arranged on a drive side of the support body or of the grinding tool. The front edge and the rear edge are in particular formed integrally with the support body.

[0022] When the grinding tool rotates in the predefined direction around the rotation axis, the front and rear edges create a vacuum on the drive side, generating an airflow from the grinding side through the corresponding through-hole to the drive side. This airflow allows for the removal of grinding dust and has a cooling effect. Because the respective rear edge is raised relative to the corresponding front edge, the airflow at the rear edge is redirected, particularly toward a corresponding recess. This allows the grinding dust to be removed from the grinding tool into the environment in the desired manner.

[0023] A grinding tool according to claim 7 ensures improved grinding properties and improved ease of use. The at least one recess or the respective recess is arranged on a drive side of the grinding tool. The at least one recess or the respective recess is arranged in a circumferential direction of the grinding tool next to an associated through-opening. Preferably, the at least one recess or the respective recess is arranged between two through-openings adjacent in the circumferential direction. The at least one recess or the respective recess extends, in particular in the radial direction, up to a circumferential contour of the support body or the grinding tool.

[0024] An air flow coming from the at least one through-opening or the respective through-opening can flow along the at least one recess or along the respective recess towards the environment. This allows grinding dust from the grinding side of the grinding tool to be discharged into the environment in the desired manner. In addition, the at least one recess or the respective recess reduces the flow resistance on the drive side, so that the air flow ensures a strong cooling effect. The at least one recess or the respective recess is designed in particular like a groove, for example in the form of a bead. The at least one recess or the respective recess has in particular a width defined in the circumferential direction, which widens in the radial direction. Preferably, each through-opening is assigned a reinforcement and / or a recess.

[0025] A grinding tool according to claim 8 ensures improved grinding properties and improved ease of use. Preferably, several through-openings are formed in the support body. The through-openings can be identical and / or different. Preferably, the through-openings are formed at equal angular intervals around the rotational axis. The support body is, in particular, rotationally symmetrical about the rotational axis with a rotation angle A. <p. Für den Drehwinkel gilt: A<p=360° / N. Die Durchgangsöffnungen haben jeweils ein inneres Ende und ein äußeres Ende. Vorzugsweise haben die inneren Enden der Durchgangsöffnungen in der Radialrichtung einen gleichen Abstand von der Drehachse. Entsprechend haben vorzugsweise die äußeren Enden der Durchgangsöffnungen in der Radialrichtung einen gleichen Abstand von der Drehachse.

[0026] A grinding tool according to claim 9 ensures improved grinding properties and improved operating comfort. The FD / FS ratio ensures, on the one hand, a sufficient field of vision for observing the workpiece through the at least one through-opening and, on the other hand, a sufficiently large grinding layer. The larger the FD / FS ratio, the larger the field of vision. Conversely, the smaller the FD / FS ratio, the larger the grinding layer. If multiple through-openings are formed in the support body, the area FD denotes the sum of all partial areas of the through-openings.

[0027] A grinding tool according to claim 10 ensures improved grinding properties and improved operating comfort. The AD / AS ratio ensures, on the one hand, that an operator can adequately observe the workpiece or the grinding area and, on the other hand, that the stability of the workpiece or the grinding tool in the grinding area is maintained. The larger the AD / AS ratio, the better the grinding area can be observed by an operator. Conversely, the smaller the AD / AS ratio, the higher the stability.

[0028] A grinding tool according to claim 11 ensures improved grinding properties and improved operating comfort. The radial distance AA corresponds to a dimension of a closed outer region of the support body in the radial direction. The ratio AA / AD ensures, on the one hand, that an operator can sufficiently observe the workpiece or the grinding area and, on the other hand, that the stability of the grinding tool or the support body is not impaired. The larger the ratio AA / AD, the larger the dimension of the closed outer region in relation to the dimension of the at least one through opening in the radial direction and the greater the stability. Conversely, the smaller the ratio AA / AD, the larger the dimension of the at least one through opening and thus the observability of the workpiece or the grinding area.A grinding tool according to claim 12 ensures improved grinding properties and improved ease of use. The angle α enables alignment of the at least one through-opening or the respective through-opening to a desired setting angle of the grinding tool. The angle α is defined between the radial direction and the main extension direction of the at least one through-opening or the respective through-opening in relation to an intersection point P. The intersection point P lies within the respective through-opening and has the smallest distance from the rotation axis in the radial direction. If multiple through-openings are formed in the support body, the through-openings can have identical angles α and / or different angles α.

[0029] A grinding tool according to claim 13 ensures improved grinding properties and improved operating comfort. The L / B ratio enables adaptation of the at least one through-opening or the respective through-opening to the desired viewing area and the required stability of the grinding tool. Preferably, the at least one through-opening or the respective through-opening is designed as an elongated hole, where L / B > 1, in particular L / B > 1.5, and in particular L / B > 2.

[0030] A grinding tool according to claim 14 ensures improved grinding properties and improved ease of use. The abrasive grains are immediately or directly attached to the carrier body by means of a ground bond. The ground bond comprises a binder or adhesive that serves to attach the abrasive grains to the carrier body. To produce the grinding tool, the carrier body is coated with the binder or adhesive, forming an adhesive surface. The abrasive grains are transported to the adhesive surface, for example, using an electrostatic field, and adhere there. After the binder or adhesive has hardened, the abrasive grains are attached to the adhesive surface or the surface of the carrier body. The carrier body itself thus forms a base for the abrasive grains or the grinding layer. The abrasive grains can be applied to the carrier body in one or more layers.Preferably, the abrasive layer comprises only a layer of abrasive grains which are attached directly to the support body.

[0031] With regard to the fastening of the abrasive grains directly to a support body and with regard to a grinding tool produced in this way, reference is made to WO 2018 / 149 483 A1, the content of which is incorporated by reference into this patent application.

[0032] A grinding tool according to claim 15 ensures improved grinding properties and improved ease of use. The grinding layer is indirectly attached to the support body via the support layer. The support layer is in particular annular and / or one-piece. The support layer comprises in particular at least one material selected from the group of vulcanized fiber, rubber and paper. The support layer is attached to the support body by means of a binder or adhesive. Preferably, the support layer is attached to the support body with at least 80%, in particular with at least 90%, and in particular with at least 95% of its surface. The grinding layer is attached to the support layer on a side opposite the support body. The grinding layer and the support layer form in particular a coated abrasive that is attached to the support body.Further features, advantages, and details of the invention will become apparent from the following description of several exemplary embodiments. They show:

[0033] Fig. 1 is a side view of a grinding tool in the form of a grinding wheel according to a first embodiment,

[0034] Fig. 2 is a plan view of the grinding wheel in Fig. 1 to illustrate a grinding layer attached directly to a support body and through openings formed in the support body,

[0035] Fig. 3 is a rear view of the grinding wheel in Fig. 1 to illustrate reinforcements in a border area around the through openings and recesses,

[0036] Fig. 4 is a first sectional view through the grinding wheel along the section line IV-IV in Fig. 3,

[0037] Fig. 5 is a second sectional view through the grinding wheel along the section line VV in Fig. 3,

[0038] Fig. 6 is an enlarged view of a detail VI in Fig. 5,

[0039] Fig. 7 is a plan view of a grinding tool in the form of a grinding wheel according to a second embodiment, Fig. 8 is a sectional view through the grinding wheel along the section line VIII-VIII in Fig. 7, and

[0040] Fig. 9 is an enlarged sectional view through the grinding wheel along the section line IX-IX in Fig. 7 in the area of ​​one of the through openings.

[0041] A first embodiment of the invention is described below with reference to Figures 1 to 6. The grinding tool 1 shown in Figures 1 to 6 is designed as a grinding wheel. The grinding tool 1 comprises a support body 2 and an abrasive layer 3 arranged thereon. The grinding tool 1 serves for grinding a workpiece W. The workpiece W is, in particular, metallic. The workpiece W is illustrated by way of example in Figure 4. The abrasive layer 3 is only partially shown in Figures 1 and 2.

[0042] The grinding tool 1 forms an axis of rotation M. The grinding tool 1 defines a grinding side S and a drive side A along the axis of rotation M. During grinding, the grinding tool 1 is rotationally driven about the axis of rotation M by means of a grinding tool drive (not shown). For this purpose, the grinding tool 1 comprises a connecting element 4. The connecting element 4 is designed as a hub and arranged concentrically to the axis of rotation M. On the grinding side S, the grinding layer 3 is arranged on the support body 2. The grinding side S faces the workpiece W during grinding. In contrast, the drive side A faces the grinding tool drive during grinding. The support body 2 is designed in the form of a support plate. The support body 2 is made in one piece from a non-metallic material, for example from a plastic. The support body 2 defines a circumferential contour UK, which is designed as a circle.

[0043] In the present exemplary embodiment, six through-openings are formed in the support body 2, which are collectively referred to as through-openings D and individually as through-openings Di, D , D3, D4, D5, and De. The through-openings D extend completely through the support body 2 in an axial direction, i.e., in the direction of the rotation axis M. The through-openings D serve to observe the workpiece W during grinding. Accordingly, the through-openings D form viewing windows or viewing areas. For a number N of through-openings D, the following generally applies: 1 < N < 24, in particular 2 < N < 12, and in particular 3 < N < 8.

[0044] The support body 2 forms in a radial direction R successively a clamping area 5, a closed inner area 6, an interrupted central area 7 and a closed outer area 8.

[0045] The clamping area 5 is flat. The connecting element 4 is arranged or formed in the clamping area 5 concentrically to the rotation axis M.

[0046] The closed inner region 6 surrounds the clamping region 5. The closed inner region 6 is ring-shaped and arranged concentrically to the axis of rotation M. The closed inner region 6 extends in the radial direction R from the clamping region 5 to the interrupted central region 7 or to the through openings D. The closed inner region 6 forms a crank K, so that the interrupted central region 7 and the closed outer region 8 are spaced apart from the clamping region 5 in the axial direction. By means of the crank K, a clamping nut, which serves to connect the grinding tool 1 to the grinding tool drive, is accommodated and thus concealed in a receiving space formed by the crank K. This ensures that the clamping nut does not come into contact with the workpiece W to be machined during grinding.Furthermore, due to the offset K, the grinding tool drive is spaced from the through openings D.

[0047] The interrupted central region 7 surrounds the clamping region 5 and the closed inner region 6. The interrupted central region 7 is annular and arranged concentrically to the axis of rotation M. The interrupted central region 7 extends in the radial direction R from an inner end of the through openings D to an outer end of the through openings D. The interrupted central region 7 is interrupted in a circumferential direction C around the axis of rotation M and in the radial direction R by the through openings D. Due to the closed inner region 6 and the closed outer region 8, the through openings D are surrounded by the support body 2.

[0048] The closed outer region 8 surrounds the clamping region 5, the closed inner region 6 and the interrupted central region 7. The closed outer region 8 is annular and arranged concentrically to the axis of rotation M. The closed outer region 8 extends in the radial direction R from the outer end of the through openings D to the circumferential contour UK. Due to its circular shape, the circumferential contour UK has a constant direction of curvature with respect to the axis of rotation M. The closed outer region 8 and the constant direction of curvature of the circumferential contour UK are ensured by the fact that the through openings D do not interrupt the closed outer region 8 and the circumferential contour UK and the support body 2 surrounds the through openings D.

[0049] The through-openings Di to De are arranged at equal angles or angular spacings Acp around the rotation axis M. The following applies to the angular spacings Acp: Acp = 360° / N, where N denotes the number of through-openings D. In the present embodiment, N = 6 and Acp = 60°. The through-openings Di to De have an identical arrangement and design, so that the support body 2 is rotationally symmetrical about the angle or angular spacing Acp = 60°.

[0050] The respective inner end of the through-openings D has a radial distance Ri from the axis of rotation M, whereas the respective outer end of the through-openings D has a radial distance RA from the axis of rotation M. In the radial direction R, the through-openings D have a dimension AD = RA - RI. The through-openings D each have a main direction of extension H, which encloses an angle α with the radial direction R at an intersection point P. The intersection point P lies within the respective through-opening D and has the smallest distance from the axis of rotation M in the radial direction R. The angle α is defined opposite to a predefined direction of rotation DR of the grinding tool 1. The following generally applies to the angle α: 0° < α < 60°, in particular 10° < α < 50°, and in particular 20° < α < 40°. In general, the angle α for the through-openings D can be identical and / or different.

[0051] The through-openings D have a length L in the main extension direction H and a width B perpendicular to the main extension direction H. The general rule for the ratio L / B is: 0.5 < L / B < 10, in particular 1 < L / B < 8, and in particular 2 < L / B < 6. In the present exemplary embodiment, the through-openings D are designed in the form of an elongated hole. The following applies in particular to the shape of the elongated hole: L / B > 1, in particular L / B > 1.5, and in particular L / B > 2. The respective elongated hole has rounded corners.

[0052] The closed outer region 8 extends from the outer end of the through-openings D to the circumferential contour UK. The circumferential contour UK has a radial distance Ru from the rotation axis M in the radial direction R. For a dimension AA of the closed outer region 8 in the radial direction R, the following applies: AA = Ru - RA. The radial dimension AA of the closed outer region 8 thus corresponds to the radial distance of the through-openings D from the circumferential contour UK. The following generally applies to the ratio AA / AD: 0.05 < AA / AD < 0.5, in particular 0.1 < AA / AD < 0.4, and in particular 0.15 < AA / AD < 0.3.

[0053] The abrasive layer 3 is arranged in the interrupted central region 7, in the closed outer region 8 and partially in the closed inner region 6. In the region of the through-openings D, no abrasive layer 3 is present. The abrasive layer 3 is only partially shown in Figures 1 to 6. The abrasive layer 3 comprises a base bond 9, abrasive grains 10 and a cover bond 11. The abrasive grains 10 are directly attached to the carrier body 2 by means of the base bond 9. The base bond 9 comprises a binder which provides an adhesive surface for the abrasive grains 10. The cover bond 11, which comprises a binder and optionally abrasive-active fillers, is applied to the abrasive grains 10. The binder of the base bond 9 and the cover bond 11 can be identical or different.

[0054] During the manufacture of the grinding tool 1, the abrasive grains 10 are transported to the ground bond 9 or the bonding surface, for example, by an electrostatic field. The abrasive grains 10 are thereby aligned with their central longitudinal axes relative to the support body 2 and relative to each other. The abrasive grains 10 are triangular in cross-section. The abrasive grains 10 thus have a geometrically defined cutting edge.

[0055] The grinding layer 3 has a three-dimensional shape. The grinding layer 3 is curved in the circumferential direction C and in the radial direction R. The grinding layer 3 is annular. Because the grinding layer 3 is arranged partially in the closed inner region 6, completely in the interrupted central region 7, and completely in the closed outer region 8, the grinding layer 3 forms an inner closed grinding region Si, a central interrupted grinding region SM, and an outer closed grinding region SA. The central interrupted grinding region SM corresponds to the interrupted central region 7 of the support body 2. The closed outer grinding region SA corresponds to the closed outer region 8 of the support body 2. The closed inner grinding region Si corresponds to an annular part of the closed inner region 6, which faces the through-openings D in the radial direction R.The through openings Di to De each have a corresponding area FDI to FD6. The through openings Di to De have a total area FD, where FD applies. = FDI + FD2 + FD3 + FD4 + FDS + FDC. The grinding layer 3 has an area Fs. The following generally applies to a ratio FD / FS: 0.05 < FD / FS < 0.8, in particular 0.1 < FD / FS < 0.6, and in particular 0.15 < FD / FS < 0.4.

[0056] The grinding layer 3 extends in the radial direction R from a distance Rs from the rotational axis M to the distance Ru of the circumferential contour UK. The grinding layer 3 has a dimension As = Ru - Rs in the radial direction R. The following generally applies to a ratio AD / AS: 0.2 < AD / AS < 1, in particular 0.3 < AD / AS < 0.9, and in particular 0.4 < AD / AS < 0.8.

[0057] Each of the through-holes Di to De is assigned a reinforcement Vi to Ve and a recess Ti to Te. The reinforcements are individually designated Vi to Ve and collectively V. Accordingly, the recesses are individually designated Ti to Te and collectively T. The reinforcements Vi to Ve are arranged in a corresponding border area Ui to Ue around the corresponding through-hole Di to De. The border areas are individually designated Ui to Ue and collectively U.

[0058] The reinforcements V are identically designed and arranged in a respective surrounding area U around the respective through-opening D. The reinforcements V are arranged on the drive side A of the support body 2. The reinforcements V are part of the support body 2 and are formed by it. In the area of ​​the reinforcements V, the support body 2 has a greater material thickness than in the area of ​​the recesses T. The reinforcements V completely surround the respective through-opening D. The reinforcements V each form a front edge 12 and a rear edge 13 when viewed in the circumferential direction C or in the predefined direction of rotation DR. The front edge 12 is arranged in front of the rear edge 13 with respect to the predefined direction of rotation DR of the grinding tool 1. The rear edge 13 is higher than the front edge 12.

[0059] The recesses T are arranged in front of the respective associated through-opening D and adjacent to the respective front edge 12 with respect to the predefined direction of rotation DR. The recesses T are formed by the support body 2, which has a smaller material thickness in the region of the recesses T. The recesses T have a width in the circumferential direction C that widens in the radial direction R. The recesses T are preferably V-shaped in cross-section.

[0060] The functionality of grinding tool 1 is described in detail below:

[0061] The grinding tool 1 is connected in the usual way by means of the connecting element 4 to a grinding tool drive (not shown in more detail), for example to an angle grinder. For this purpose, a drive shaft of the grinding tool drive is guided through the connecting element 4 designed as a hub, and the grinding tool 1 is connected in the clamping area 5 to the drive shaft of the grinding tool drive by means of a clamping nut. The drive side A faces the grinding tool drive, whereas the grinding side S faces the workpiece W to be machined. The grinding of the workpiece W is carried out by an operator. For this purpose, the operator guides the grinding tool 1 to the workpiece W and brings the grinding layer 3 into contact with the workpiece W. Because the through openings D form viewing areas, the operator can observe the workpiece W and the flying sparks during grinding through the through openings D.This allows the operator to optimally adjust the angle of attack of the grinding tool 1 relative to the workpiece W and thus the size and / or position of a working point of the grinding layer 3. For example, the angle of attack or the working point is optimally adjusted when the flying spark passes approximately centrally through the respective through-opening D. Because the through-openings D are surrounded by the support body 2, the closed outer region 8 stabilizes the support body 2 or the grinding tool 1. Because the closed outer grinding region SA of the grinding layer 3 is arranged in the closed outer region 8, the closed outer region 8 of the support body 2 can also be used for grinding.

[0062] When the grinding tool 1 rotates about the axis of rotation M, a negative pressure is created on the drive side A due to the reinforcements V compared to the grinding side S. Due to the negative pressure, air flows from the grinding side S through the respective through-opening D to the drive side A. The air flow F is illustrated in Fig. 3 as an example for the through-opening Di. Starting from the respective through-opening D, the air flows out on the drive side A along the respective associated recess T into the environment. For this purpose, the air is deflected due to the higher rear edge 13 in the direction of the respective front edge 12 and to the respective associated recess T. The air flow F carries grinding dust from the grinding side S through the through-openings D to the drive side A and from there into the environment, and the grinding layer 3 is cooled. This improves the grinding performance of the grinding tool 1.

[0063] Because the abrasive layer 3 is applied directly to the support body 2, for example by electrostatic coating in an electrostatic field, the abrasive layer 3 can be three-dimensionally shaped or curved in any desired manner, and the abrasive grains 10 can be aligned relative to the support body 2 and relative to one another. As a result, the grinding tool 1, in conjunction with the through-openings D surrounded by the support body 2, has improved grinding properties and improved operating comfort. Due to the enclosed outer region 8 and the reinforcements V, the grinding tool 1 has a user-friendly, smooth running and prevents an impact effect of the grinding tool 1 during grinding, thus reducing wear on the grinding tool 1 and strain on the operator. In particular, the grinding tool 1 can reduce the processing time and thus the strain on the operator.

[0064] A second exemplary embodiment of the invention is described below with reference to Figures 7 to 9. In contrast to the first exemplary embodiment, the abrasive layer 3 is fastened to the support body 2 via a support layer 14. The abrasive layer 3 is only partially shown in Figure 7. The abrasive layer 3 is fastened to the support layer 14 and forms abrasive on a backing. The support layer 14 is of one-piece and annular design. The abrasive layer 3 is fastened to the support layer 14, which in turn is fastened to the support body 2 with the side facing away from the abrasive layer 3. The support layer 14 is fully connected to the support body 2. The support layer 14 is fastened in the interrupted central region 7 and partially in the closed inner region 6 and partially in the closed outer region 8. The support layer 14 is made, for example, of vulcanized fiber, rubber or paper.The support layer 14 is attached to the support body 2 by means of a binding agent. The abrasive layer 3 is not bent or flexed and thus not broken. The support layer 14 has through-openings whose number, arrangement, and design correspond to the through-openings D of the support body 2, so that the visible areas formed by the through-openings D are retained. Regarding the further structure and further functioning of the grinding tool 1, reference is made to the previous embodiment.

Claims

Patent claims 1. Grinding tool, in particular grinding wheel, comprising - a supporting body (2), and - a grinding layer (3) arranged on the support body (2), characterized in that at least one through-opening (D) for observing a workpiece (W) during grinding is formed in the support body (2), and that the at least one through-opening (D) is surrounded by the support body (2).

2. Grinding tool according to claim 1, characterized in that the support body (2) comprises: a spaim region (5) for rotating the grinding tool (1) about a rotation axis (M) by means of a grinding tool drive, a central region (7) interrupted by the at least one through opening (D) and surrounding the spaim region (5), and a closed outer region (8) surrounding the interrupted central region (7).

3. Grinding tool according to claim 2, characterized in that the closed outer region (8) forms a circumferential contour (UK) which has a constant direction of curvature with respect to the axis of rotation (M).

4. Grinding tool according to one of claims 2 or 3, characterized in that that the grinding layer (3) is arranged at least in the interrupted central region (7).

5. Grinding tool according to at least one of the preceding claims, characterized in that the supporting body (2) forms at least one reinforcement (V) which is arranged around the at least one through opening (D).

6. Grinding tool according to at least one of the preceding claims, characterized in that the support body (2) forms a front edge (12) and a rear edge (13) in a border region (U) around the at least one through opening (D), wherein the rear edge (13) is raised compared to the front edge (12).

7. Grinding tool according to at least one of the preceding claims, characterized in that the supporting body (2) forms at least one recess (T) next to the at least one through-opening (D).

8. Grinding tool according to at least one of the preceding claims, characterized in that for a number N of the at least one through-opening (D) the following applies: 1 < N < 24, in particular 2 < N < 12, and in particular 3 < N < 8.

9. Grinding tool according to at least one of the preceding claims, characterized in that that the at least one through-opening (D) has an area FD and the grinding layer (3) has an area Fs, where: 0.05 < FD / FS < 0.8, in particular 0.1 < FD / FS < 0.6, and in particular 0.15 < FD / FS < 0.

4.

10. Grinding tool according to at least one of the preceding claims, characterized in that the at least one through-opening (D) has a dimension AD radially to a rotational axis (M) and the grinding layer (3) has a dimension As radially to the rotational axis (M), where: 0.2 < AD / AS < 1, in particular 0.3 < AD / AS < 0.9, and in particular 0.4 < AD / AS < 0.

8.

11. Grinding tool according to at least one of the preceding claims, characterized in that the at least one through-opening (D) has a dimension AD radially to a rotational axis (M) and for a radial distance AA of the at least one through-opening (D) from a circumferential contour (UK) of the support body (2) the following applies: 0.05 < AA / AD < 0.5, in particular 0.1 < AA / AD < 0.4, and especially 0.15 < AA / AD < 0.

3.

12. Grinding tool according to at least one of the preceding claims, characterized in that the at least one through-opening (D) defines a main extension direction (H), wherein for an angle a between a radial direction (R) and the main extension direction (H) the following applies: 0° < a < 60°, in particular 10° < a < 50°, and in particular 20° < a < 40°.

13. Grinding tool according to at least one of the preceding claims, characterized in that that the at least one through-opening (D) has a length L in a main extension direction (H) and a width B perpendicular to the main extension direction (H), where: 0.5 < L / B < 10, in particular 1 < L / B < 8, and in particular 2 < L / B < 6.

14. Grinding tool according to at least one of the preceding claims, characterized in that the grinding layer (3) is attached directly to the supporting body (2).

15. Grinding tool according to at least one of claims 1 to 12, characterized in that the grinding layer (3) is attached to a support layer (14) which is attached to the support body (2).

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