GB2150470A

GB2150470A - Making a grinding tool

Info

Publication number: GB2150470A
Application number: GB08408170A
Authority: GB
Inventors: Peter Bruhn; Eberhard Seiffert; Herbert Ancker; Villy Hornskov
Original assignee: Ver Schmirgel & Maschf
Current assignee: Ver Schmirgel & Maschf
Priority date: 1983-11-23
Filing date: 1984-03-29
Publication date: 1985-07-03
Also published as: DE3342233A1; GB8408170D0; IT1181534B; IT8485555A0; GB2150470B; FR2555088A1

Abstract

A grinding tool is made by connecting a plurality of fringed rectangular strips (3) of abrasive material to a cylindrical foundation member (1). An uncut central area (6) of each strip (3) containing the longitudinal axis (5) of symmetry is connected to the foundation member (1) so that the axis (5) follows a helical path on the surface of the foundation member (1). <IMAGE>

Description

SPECIFICATION Method of producing a grinding tool The present invention relates to a method of producing grinding tools.

International Patent Application DE 31 52 552 Al (WO 82/01845) discloses a method of producing grinding elements in which a rectangular sheet is slitted along its entire length. Each slit extends from a point away from the centre line as far as the closer side edge to form a number of interconnected small sheets. After slitting the sheet is folded about the centre and then bent round and joined end to end at the center to form a closed ring. Then a wire of melting material is laid into the fold line, and after bending over is combined with the ring by the application of heat and pressure. The rings made in this way are placed on a rotating spindle. Between each ring a holding disc is provided.

This proposed method is time-consuming and cumbersome. The grinding tool produced in this way exhibits only a low level of grinding performance. The individual small sheets produced have no grinding action when the tool is used for processing the edge surfaces of plates stacked one upon the other and separated by gaps. in this situation the flexible grinding sheets are deflected away from the plates and do not touch the edge surfaces requiring grinding. In addition, the plates, as a consequence of their alignment, strike the tool with their edges, and cause indentations and markings, and damage the edges of the tool which should remain square.

Finally, the performance of this proposed method requires the employment of a large amount of technical apparatus because of the use of heating and pressing devices.

The present invention provides a method of producing a grinding tool including a solid foundation member and grinding or polishing members affixed onto said solid foundation, which grinding or polishing members each consist of a flexible, rectangular thin strip of abrasive on a support, the strip having parallel longitudinal sides and two shorter parallel transverse sides, including the steps of slitting each strip to form a fringe along each longitudinal side, the fringes being disposed on both sides of a longitudinal central area containing an axis of symmetry of the strip and the fringes being parallel to said transverse sides, said slitting step releasing inherent stresses in said strip, and disposing said slitted strip on the foundation member and joining them to said member in such a manner that the central areas of the individual grinding members come to lie along a helical path with the abrasive facing outwardly with respect to the foundation member and said axis of symmetry of each strip coinciding with said path.

The invention also provides a method of producing a grinding tool including the steps of taking at least one retangular lamina having two parallel long sides and two parallel short sides and two major surfaces, at least one said major surface being abrasive, cutting a plurality of parallel slits in each said lamina, said slits extending from at least one said long side parallel to said short sides, said slits defining at least one fringe leaving an uncut londitudinally extending area, and applying said uncut area of the or each said lamina to an outer surface of a cylindrical support such that said central strip defines a helical line on said outer surface.

The invention further provides a grinding tool including a plurality of fringed strips of abrasive sheet each defining an uncut region, a cylindrical support surface to which the uncut regions of the fringed strips are secured and extend along a helical path around said surface.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which: Figure 1 is an isometric representation of a grinding tool; Figure 2 is a top view of a retangular abrasive lamina which is a starting material for producing the grinding tool of Figure 1; Figure 3 is a top view of the lamina after it has been cut to produce a fringe-like pattern; Figure 4 is an isometric representation of the arrangement according to Figure 3 in stess-relieved condition; Figure 5 is a partial view of a solid foundation member with two stretched grinding strips applied thereon; and Figure 6 is a partial view of the grinding tool showing two grinding elements in brush form connected to the foundation member.

As shown in Figure 1 the grinding tool produced by the method to be described consists of a solid foundation member 1 and grinding or polishing members 2 connected with said foundation to define a roller-shape.

The starting materials for the method are grinding agent strips 3, one of these being shown in Figure 2. Each strip is in the shape of a rectangle with two transverse sides 3a and two longer longitudinal sides 3b. These grinding agent strips 3 consist in a known manner of a base coated with a binder in which abrasive particles are firmly embedded. In the representation of Figure 2 the abrasive surface is visible.

These grinding agent strips are cut in any suitable manner from a larger-size grinding agent sheet.

The solid foundation member 1 is constucted in the illustrated embodiment as a hollow cylinder, and may consist, for example, of wound paper, fabric or plastics material. Clamping plates are fixed into each end of this solid foundation member 1. These plates allow the grinding tool to be clamped on any suitable grinding-wheel spindle with a length corresponding to the width of the tool. For those grinding-wheel spindles of a length equal to a multiple of the tool width it is possible in each instance to insert between two adjacent foundation members 1 on the spindle an intermediate connecting piece.

The transverse axis of symmetry of the strip is denoted by reference numeral 4 and reference numeral 5 denotes the longitudinal axis of symmetry of the strip 3.

The grinding agent strip 3 may for example be 250 mm long and 210 mm wide, though other dimensions may be used. The grinding agent strips 3 are then slitted, each slit starting from one of the two longitudinal sides 3b and extending as far as a central area 6 which lies on both sides of the longitudinal axis of symmetry 5. The slits produce a fringe-like formation 7 parallel with each of the two transverse sides 3a. The grinding agent strip 3 is therefore provided with fringes 7 on both sides of the lingitudinal axis 5 while the central area 6 remains uncut.

By means of this cutting process the inherent stresses of the grinding agent strip 3 are relieved, so that it assumes the brush form represented in Figure 4. The grinding agent strips 3 in brush form are now disposed on the foundation member 1 and joined to it in such a way that the central areas 6 of the individual grinding members, which adjoin at their transverse sides 3a, come to lie along a helical path 8 with the abrasive layer facing the outer surface of the foundation member 1. The axis 5 of longitudinal symmetry of each grinding agent strip 3 coincides with the helical path 8.

It is clear that the two grinding strips shown in Figure 5 assume the stretched position illustrated only when the fringe-like structure 7 is pressed in the direction of the foundation member 1; if there is no such pressure the abrasive members assume a position as shown in Figure 6.

If now several individual brush-form abrasive members are in the manner indicated hereinabove applied on the outer surface of the foundation member 1, a rose-countersink (curly-headed) and roller-shaped grinding or polishing tool in which the individual fringes of each abrasive member overlap one another in a confused manner is obtained. However, there is obtained an outstand ingly resilient yielding grinding tool providing a soft abrasive effect which operates on the complicated shapes of the workpiece in uniform manner and with a relatively reduced removal of working material.

The helical path 8 may be multiple, that is it may have several pitches, in which case there will be several starting points or ending points of the strip axes on the outer surface of the foundation mem ber 1.

In a variant of the tool each grinding agent strip 3 according to Figure 3 is cut off at one of the bor der edges of the central area 6, so that the strip re mains whole. In this manner fringes are produced which extend only in a single direction. The brushes obtained by this means are applied in the above-described manner with their centre areas 6 onto the foundation 1. In this case the abrasive grain sides of the brushes always face in one and the same direction.

The individual brush-shaped abrasive members are secured to the outer surface of the foundation member 1 by adhesive connection. For this pur pose it is necessary to coat the abrasive surface of the centre area 6 with adhesive and to glue the individual brush-shaped grinding members side by side on the surface of the foundation 1 in the above-indicated manner.

However, it is also possible to replace the glued connection by a strip clamp connection as shown in Figure 5 of the drawing. Individual clamping elements are denoted there by reference numeral 9.

In this case it is appropriate to cover the grinding members with a holding strip 10 following the helical path 8. The clamping elements 9 pass through this strip 10 as well as the associated centre area 6 of the grinding member and the ends of the clamping elements anchor themselves in the foundation member 1.

If the grinding tool is driven in rotation the fringes 7 stand up as a result of centrifugal force, and thus they point radially outwards.

It will be appreciated that the described grinding tool is able to process without difficulty and with very light grinding pressure flat workpiece surfaces, as well as convex or concave surfaces. As a result of the multiplicity of fringe-like patterns of slits and their sections defined by the varied orientations not a single area on the workpiece remains unprocessed. Consequently, this grinding tool is particularly suitable for the processing of wood workpieces with convex and/or concave surface areas. At whatever stage the processing is carried out, whether before painting, after imtermediate painting and final painting, or after pickling, the same basic depth is achieved in all parts of the surface, even when these parts face different spatial directions or lie in different planes. This is because the tool adapts itself elastically to any shape of workpiece and is therefore suitable for obtaining soft-grinding effects or even first grinding depth.

By modifying the angle of the helical line along which the individual grinding members are disposed on the outline of the solid foundation, the grinding performance may be modified at will or adapted to the workpiece to be processed, so that an optimum performance can always be achieved.

Claims

1. A method of producing a grinding tool including a solid foundation member and grinding or polishing members affixed onto said solid foundation, which grinding or polishing members each consist of a flexible, rectangular thin strip of abrasive on a support, the strip having two parallel longitudinal sides and two shorter parallel transverse sides, including the steps of slitting each strip to form a fringe along each longitudinal side, the fringes being disposed on both sides of a longitudinal central area containing an axis of symmetry of the strip and the fringes being parallel to sdaid transverse sides, said slitting step releasing inherent stresses in said strip, and disposing said slitted strips on the foundation member and joining them to said member in such a manner that the central areas of the individual grinding members come to lie along a helical path with the abrasive facing outwardly with respect to the foundation member and said axis of symmetry of each strip coinciding with said path.

2. A method as claimed in claim 1, in which the slits of the fringes are relatively close.

3. A method as claimed in claim 1, in which the spacing of the slits defining each fringe is substantially the same.

4. A method as claimed in claim 1, in which the spacing of the slits defining each fringe is variable.

5. A method as claimed in any one of the preceding claims, in which the helical path is multiple.

6. A method as claimed in any one of the preceding claims, in which the grinding members are glued to the foundation member.

7. A method as claimed on any one of claims 1 to 5, in which the grinding members are grippingly clamped to the foundation member by means of clamping elements.

8. A method according to claim 7, in which the central areas of the grinding members are covered over by a holding strip which follows the helical path and in which said clamping elements pass through said strip and the associated central area and having their ends anchored in the foundation member.

9. A method of producing a grinding tool including the steps of taking at least one rectangular lamina having two parallel long sides and has parallel short sides and two major surfaces, at least one said major surface being abrasive, cutting a plurality of parallel slits in each said lamina, said slits extending from at least one said long side parallel to said short sides, said slits defining at least one fringe leaving an uncut longitudinally extending area, and applying said uncut area of the or each said lamina to an outer surface of cylindrical support such that said central strip defines a helical line on said outer surface.

10. A grinding tool including a plurality of fringed strips of abrasive sheet each defining an uncut region, and a cylindrical support having a surface to which the uncut regions of the fringed strips are secured such that said regions extend along a helical path around said surface.

11. A method of producing a grinding tool substantially as herein described with reference to the accompanying drawings.

12. A grinding tool substantially as herein described with reference to the accompanying drawings.