GB2408226A

GB2408226A - Backing plate for grinding tool

Info

Publication number: GB2408226A
Application number: GB0425564A
Authority: GB
Inventors: Joerg Dehde
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2003-11-22
Filing date: 2004-11-19
Publication date: 2005-05-25
Anticipated expiration: 2024-11-19
Also published as: CN1618571B; DE10354653A1; GB0425564D0; CN1618571A; GB2408226B

Abstract

A backing plate for a portable grinding tool comprises a reinforcing body 11 which is connectable to a drive in the grinding tool, and an elastically deformable body 12 with a planar bearing surface 121 for attatchment of an abrasive sheet thereto. The reinforcing body 11 has an axially protruding annular collar 16 surrounding a central circular depression 15. Only an annular zone 123 of the body 11 which abuts against the collar 16 is supported by the reinforcing body 11. The distance between the centre of the bearing surface 121 and the innermost part of the annular zone 123 is approximately the same as the distance from the outer circumference of the bearing surface 121 to the outermost part of the annular zone 123. The elastically deformable body 12 is applied to the reinforcing body 11 by spraying for foaming.

Description

ROBERT BOSCH GMBH, 70442 Stuttgart Grinding wheel for a hand-held grinding

machine

Prior art

The invention takes as its starting point a grinding wheel for a handheld grinding machine having a drive gear, particularly for an eccentric or vibrating grinder, according to the precharacterising clause of Claim 1.

A known hand-held grinding machine (US 5 018 314) constructed as an eccentric grinder has a circular grinding wheel which is placed on an electric-motor driven eccentric driven shaft of an eccentric gear by means of a rotary bearing. The supporting body of the grinding wheel has a planar plate and a bearing piece which protrudes from the plate at a right-angle, forms one piece with the plate and has the rotary bearing inserted therein. The circular abrasive-medium carrier, which is manufactured from plastics material, abuts flat against the plate of the supporting body and reaches over the plate of the supporting body in cliplike manner by means of its correspondingly constructed edge.

A known grinding wheel for a hand-held grinding machine (EP 0 557 733 B1) has a supporting plate of plastics material, a pad foamed onto the supporting plate as a carrier for an abrasive medium and a steel disc arranged as a reinforcing part between them. The underside of the pad forms a planar bearing surface for an abrasive sheet and is provided with tracks of touch-and-close fasteners to which the velour rear side of the abrasive sheet adheres.

Advantages of the invention The inventive grinding wheel for a hand-held grinding machine having the features of Claim 1 is advantageous in that a very high level of flexibility of the grinding wheel is achieved as a result of the fact that the abrasive medium carrier is not supported over the entire bearing surface but only in an annular zone located within the bearing surface. During grinding, the region of the annular zone of the abrasive-medium carrier is relatively hard as a result of being supported on the supporting body, and the outer and inner regions of the abrasivemedium carrier which adjoin the annular zone are softer owing to the lack of support by the supporting body and therefore adapt better to the contour of the surface to be machined. As a result of these differentlyacting elastic regions of the abrasive-medium carrier, the grinding wheel can tilt around the "harder" region of the abrasive-medium carrier, as a result of which the grinding wheel lies against the workpiece very well, resulting in smooth movement of the hand-held grinding machine. Overall, the grinding wheel according to the invention adapts very well to convex and concave contours of the workpiece surface and delivers very good grinding results. The grinding wheel according to the invention is also advantageous when the surfaces to be machined are planar. As a result of the "softer" region of the abrasive-medium carrier located within the "harder" annular area, no increased pressure is transmitted to the workpiece in the centre of the grinding wheel and the \ abrasive sheet, the track of touch-and-close fastenings present between the abrasive sheet and the bearing surface, or the paint finish of the workpiece are prevented from overheating.

Advantageous further developments and improvements of the grinding wheel indicated in Claim 1 are possible as a result of the measures described in the further claims.

Drawing The invention is described in more detail below with reference to an exemplary embodiment illustrated in the drawing, which shows: Fig. 1 a section of a grinding wheel for an eccentric grinder; Fig. 2 a sectional illustration of the grinding wheel according to Fig. 1, pressed against a workplace having a convex surface.

Description of the exemplary embodiment

As an exemplary embodiment for a hand-held grinding machine having an electric-motor driven drive gear, the grinding wheel (illustrated in a longitudinal section in Fig. 1) for an eccentric grinder has a supporting body 11 and an abrasive-medium carrier 12 which is fixed on the supporting body 11 and is made of an elastically deformable material, preferably a plastics material. The abrasive-medium carrier 12 is fixed to the supporting body 11 by spraying or foaming. The supporting body 11 manufactured from plastics material or metal is constructed to be placed on the drive gear of the eccentric grinder and, to this end, has a central through-opening 13 for guiding through a fixing screw. One example of an eccentric grinder having a drive gear constructed as an eccentric gear is illustrated in US 018 314. Like the grinding wheel described therein, the supporting body 11 here can also have a further central cutout for receiving a rotary bearing placed on the driven shaft of the eccentric gear.

In the exemplary embodiment of Fig. 1, the grinding wheel is circular. The supporting body 11 is in the form of a truncated cone on which the abrasive-medium carrier 12 is placed on its base surface having the larger diameter, said abrasive-medium carrier at the same time reaching over the lateral surface 112 of the supporting body 11.

The abrasive-medium carrier 12 has a rear side 122 and, remote therefrom, a planar bearing surface 121 for an abrasive sheet (not illustrated here), to which the abrasive sheet adheres e.g. by means of a touch-and-close fastening. The touch-and-close fastening can be realised in known manner by a touch-and-close covering on the bearing surface 121 and a velour covering on the rear side of the abrasive sheet. A central opening 14 passing through the abrasive-medium carrier 12 up to the supporting body 11 is provided in the bearing surface 121.

Provided in the base surface 111 of the supporting body 11, there is a central depression 15, as a result of which an axially protruding, circumferential collar 16 is formed on

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the end face of the supporting body 11 which faces the rear side 122 of the abrasive-medium carrier 12. The collar 16, which is constructed in one piece with the supporting body 11, abuts against the rear side 122 of the abrasive-medium carrier 12 by means of an end-face supporting surface 161, so that the abrasive-medium carrier 12 is only supported by the supporting body 11 in an annular zone 123 within its bearing surface 121. The annular zone 123 in the exemplary embodiment of Fig. 1 is positioned such that the radial spacing between the outer annular-zone edge and the axis of the grinding wheel and the radial spacing between the outer annular-zone edge and the circumferential line of the abrasive-medium carrier 12 are approximately the same size.

The width of the collar 16, and therefore the width of the annular zone 123 within which the abrasive-medium carrier 12 is supported by means of its rear side 122 remote from the bearing surface 121, is selected according to the individual application.

As a result of the fact that the abrasive-medium carrier 12 is only supported on the supporting body 11 by means of its rear side 122 within the annular zone 123, zones or sections having a different elasticity are produced in the abrasive-medium carrier 12 when grinding. The annular zone 123 is relatively hard so that a relatively high pressure force can thereby be applied to the workpiece during grinding. The outer and inner adjoining sections are "softer" and can adapt very well to uneven contours of the surface of the workpiece.

The deformation of the abrasive-medium carrier 12 when pressing against a convex surface 17 of a workplace is illustrated in Fig. 2. This clearly shows that the section of the abrasive-medium carrier 12 which is located outside the annular zone 123 and the section of the abrasive-medium carrier 12 which is located inside the annular zone 123 deform elastically and cling to the convex contour of the surface 17 to be machined. This ensures even abrasion and therefore high-quality grinding results.

The invention is not restricted to a grinding wheel for an eccentric grinder, it can relate equally well to a grinding wheel for an oscillating grinder. The grinding wheel can also be of a quadrangular, rectangular or square construction. In this case, for example, the supporting body 11 is constructed as a truncated pyramid, in which a quadrangular depression is present in its base surface so that a frame- like circumferential collar 16 is produced to support the rectangular or square abrasive-medium carrier 12. The supporting body 11 can also be constructed as a plastics plate. In this case, the circumferential collar 16 is produced with an end-face supporting surface for the abrasive-medium carrier 12 by providing a central depression in the plastics plate and, more precisely, in its plate surface which faces the abrasive-medium carrier 12. )

Claims

Claims 1. A grinding wheel for a hand-held grinding machine having a drive

gear, particularly an eccentric or vibrating grinder, having a supporting body (11), which may be connected to the drive gear, and an abrasive-medium carrier (12) which is made of an elastically deformable material, is supported on the supporting body (11) and has a rear side (122) which faces the supporting body (11) and a planar bearing surface (121) for an abrasive sheet, said bearing surface being remote from the supporting body (11), characterized by a construction of the supporting body (11) which is such that the abrasive-medium carrier (12) is only supported on its rear side (122) within an annular zone (123).
2. A grinding wheel according to Claim 1, characterized in that the spacing between the inside edge of the annular zone (123) and the centre of the bearing surface (121) and the spacing between the outside edge of the annular zone (123) and the outside edge of the bearing surface (121) are approximately the same size.
3. A grinding wheel according to Claim 1 or 2, characterized in that a central opening (14) passing through the abrasive-medium carrier (12) is present in the bearing surface (121).
4. A grinding wheel according to one of Claims 1 - 3, characterized in that the supporting body (11) has, on its end face facing the rear side (122) of the abrasive-medium carrier (12), an axially protruding circumferential collar - ' (16) which abuts against the abrasive-medium carrier (12) within its annular zone (123) by means of an end-face supporting surface (161).
5. A grinding wheel according to one of Claims 1 - 4, characterized in that the abrasive-medium carrier (12) has a circular bearing surface (121) and the supporting body (11) is a truncated cone in which a central, circular depression (15) is present in its base surface (111) abutting against the rear side (122) of the abrasive-medium carrier (12).
6. A grinding wheel according to one of Claims 1 - 4, characterized in that the abrasive-medium carrier (12) has a quadrangular bearing surface (121) and the supporting body (11) is a truncated pyramid in which a central, quadrangular depression (15) is present in its base surface (111) abutting against the rear side (122) of the abrasive- medium carrier (12).
7. A grinding wheel according to one of claims 1 - 4, characterized in that the supporting body (11) is a planar plate body in which a central depression (15) is present in its base surface abutting against the rear side (122) of the abrasive-medium carrier (12).
8. A grinding wheel according to one of Claims 1 - 7, characterized in that the abrasive-medium carrier (12) is applied to the supporting body (11) by spraying or foaming.
9. A grinding wheel substantially as herein described with reference to the accompanying drawings.