WO2009067077A1

WO2009067077A1 - Grinding elements

Info

Publication number: WO2009067077A1
Application number: PCT/SE2008/051329
Authority: WO
Inventors: Kåre Kilgren
Original assignee: Htc Sweden Ab
Priority date: 2007-11-20
Filing date: 2008-11-20
Publication date: 2009-05-28

Abstract

A grinding element (1) adapted to be arranged on a holder plate (2), for grinding and/or polishing hard floor surfaces, wherein the grinding element (1) has the form of a geometric body defined by a substantially oblong base surfaces B, a work piece engaging surface A, spaced apart from the base surface B, and at least two spaced apart long side surfaces L extending substantially along a longitudinal direction of the grinding element and substantially between the base surface B and the work piece engaging surface A, wherein the long side surfaces L present a respective concave surface portion.

Description

GRINDING ELEMENTS

Technical Field

The present document relates to grinding elements for grinding and/or polishing hard floor surfaces, such as concrete floors, wherein the grinding element has a shape for reducing the work piece engaging surface and maintaining mounting stability.

Background

When grinding and/or polishing hard floor surfaces, e.g. of stone or stone-like material such as concrete, terrazzo etc., a grinding machine is usually employed together with water or other cutting fluids. The residual particles, i.e. dust and debris, from the grinding process are collected together with the water. The water also reduces the temperature at the contact area between the work piece and the grinding element. The collected dust and debris, mixed with water or other fluids, may be very heavy and difficult to handle and remove from the grinding working site. Therefore a procedure with dry grinding/polishing is desirable, where the dust and debris simply can be removed by vacuum cleaning and gathered as a dry mass.

In a dry procedure the threshold friction when starting the grinding, i.e. starting the rotational movement of the grinding device over the work piece, renders the torque applied, and hence the heat developed, high. The high heat development is especially undesirable when using grinding devices with abrasive particles, which are heat sensitive, e.g. diamond.

It is further important that the grinding elements are designed to withstand the applied forces and the threshold friction that arises during start- up.

Grinding devices and grinding elements for grinding and/or polishing hard floor surfaces are known from e.g. EP 1 321 233 A1.

EP-A1 -1 304 190 discloses a cutting tool for the removal of coatings from mineral substrates consisting of a series of angled cutting segments. However these cutting segments are quite large, thus having a relatively large threshold friction and therefore a large heat development at the start-up of grinding.

US 6 196 91 1 B1 disclose a tool including abrasive elements, which may be formed in arcuate sections. These segments are also, however quite large and may hence give rise to a large heat development during start-up due to the forces applied.

US 2,501 ,422 and CH52589 disclose grinding segments having a single concave long side surface.

Hence, there is a need for a grinding element, which reduces the forces applied at the onset of grinding and also the heat which is developed and which is capable of withstanding the forces applied at the start up and during the grinding process.

Summary It is a general object of the present disclosure to provide an improved or alternative grinding element, which eliminates or alleviates at least some of the disadvantages of the prior art.

More specific objects include providing a grinding element which is able to reduce the heat development and withstand the forces applied during the start up of the grinding process.

The invention is defined by the independent claims. Embodiments are set forth in the following description and drawings.

According to a first aspect, there is provided a grinding element adapted to be arranged on a holder plate, for grinding and/or polishing hard floor surfaces, wherein the grinding element has the form of a geometric body defined by a substantially oblong base surfaces, a work piece engaging surface, spaced apart from the base surface, and at least two spaced apart long side surfaces extending substantially along a longitudinal direction of the grinding element and substantially between the base surface and the work piece engaging surface, wherein the long side surfaces present a respective concave surface portion.

By the grinding element having at least one concave portion, there is provided a grinding element which is curved and it is hence possible to have a narrow profile, i.e. a small short side length of the grinding element. A narrow profile results in a reduced engagement surface area, but still has a relatively large support surface bearing against the holder plate and therefore may be able to withstand the forces applied during start-up of the grinding. The two substantially concave surface portions may be formed as a smoothly curved shape, or by two or more surface portions which meat at an angle.

The term "grinding element" refers to an element with a grinding and/or polishing effect. Such elements can comprise a matrix of metal or plastics resin which contain grinding particles of any size and any material, for example a grinding agent such as PCD and/or diamond.

The term "for grinding and/or polishing" here refers to a holder plate with only a grinding and/or polishing element and hence not holder plates which have one or more cutting edges for cutting of floor surfaces. The base surface and the work piece engaging surface of the grinding element may be substantially parallel and of substantially the same size, such that the geometric body thus formed presents an essentially constant cross section.

At least one of the long side surfaces may present at least one substantially convex surface portion.

According to one alternative the grinding element has at least two long side surfaces, and the at least two long side surfaces both present a substantially concave portion and a substantially convex portion, and the at least two long side surfaces are substantially parallel. The substantially convex portion of one of the two long side surfaces may be aligned with the concave portion of the other long side surface, and vice versa.

According to one alternative the long side surfaces are arranged on opposite sides of the grinding elements. By this configuration of the grinding element the narrow profile may be achieved, which is able to withstand the threshold friction at the onset of and during grinding, but which still gives rise to lower applied forces and hence less heat development. The work piece engaging surface of the grinding element may have a varying topography.

By forming the grinding elements according to the present disclosure with a work piece engaging surface of varying topography there is provided a way of further reducing the threshold friction and creating a smoother start up of grinding, but still achieving a resilient grinding element.

The length of the grinding element in a longitudinal direction may be at least two times the width of the grinding element in a transversal direction, or at least four times, or at least six times or at least eight times or at least ten times the width of the grinding element in a transversal direction.

According to another embodiment, the grinding element presents at least one short side surface having a width, which is less than 50% of the total transversal extent of the grinding element, as seen in a direction transversely of the longitudinal direction. According to this embodiment a narrow and in a longitudinal direction extended grinding element is achieved.

The grinding element may be formed by an essentially homogenous material matrix with abrasive particles dispersed throughout, wherein material is formed by a metal bond diamond. By the grinding element being formed by a metal bond material, there is provided a grinding element with excellent grinding properties and resistance for grinding and/or polishing hard floor surfaces such as concrete, stone, terrazzo or similar, which also has a low threshold friction, and that gives rise to lower forces and heat development during grinding. According to a second aspect there is provided a tool for grinding and/or polishing hard floor surfaces comprising a holder plate, on which at least one grinding element, according to the first aspect of the solution, is arranged.

The tool may be configured for a direction of rotation, and the grinding element is arranged on the holder plate substantially with its longitudinal directions transversely of the direction of rotation.

According to an alternative embodiment at least two grinding elements are arranged on a holder plate. According to an alternative, 1 to 10 grinding elements may be arranged on a holder plate.

The holder plate may present sides which form an acute angle with each other, and which have undercut flanges that are formed for surrounding engagement with an undercut shoulder arranged on the abrading plate.

Such a holder plate can be releasably mountable on a abrading plate, e.g. by a sliding movement in a radial direction of the abrading plate.

Brief Description of the Drawings Embodiments of the present solution will now be described, by way of example, with reference to the accompanying schematic drawings.

Fig. 1 shows a schematic plan view of a holder plate supporting grinding elements according to the one embodiment.

Fig. 2 shows a schematic plan view of a grinding disc on which are arranged three holder plates according to Fig. 1.

Figs. 3a-3f show schematic plan views of grinding elements according to alternative embodiments.

Fig. 4a is a schematic perspective view of the grinding element in Fig. 3b. Fig. 4b is a schematic plan view of an alternative grinding element.

Figs 5a-5f show schematic perspective views of grinding elements according to alternative embodiments.

Description of Embodiments Fig. 1 shows grinding plate 3 on which holder plates 2 are arranged.

The holder plates 2 support grinding elements 1 , according to the present solution. On the holder plate 2 there are two grinding elements 1 a, 1 b arranged, the holder plate 2 and the grinding elements 1 make up the grinding tool 4. The holder plate 2 is an arrangement which can be used to attach the holder plate 2 to the grinding plate 3. Examples of such elements can be threaded holes for fastening the holder plate to the grinding disc by means of screws as shown in EP-1 321 233. Another example of such an element can be the surrounding flanges as shown in WO 2004/108352.

Fig. 2 shows a grinding plate 3 on which are arranged three holder plates 2, supporting grinding elements 1. It can be seen that the number of holder plates 2 arranged on the grinding plate 3 can vary as required. Normal configurations comprise 3-6 holder plates 2. It can be seen that the holder plate 2 according to the present solution can be fitted with an arbitrary number of grinding elements for example 1 , 2, 3, 4, 5, 6, 7, 8, 9 or 10 depending on requirements and the space available on the holder plate 2. Fig. 2 also shows a tool 4 for grinding and/or polishing hard floor surfaces where the tool 4 according to one embodiment comprises a holder plate 2 on which at least one grinding element 1 is arranged. The tool 4 is configured to rotate in an intended direction R (Fig. 1 ). According to one embodiment, the grinding element 1 may be arranged on the holder plate 2 with its longitudinal directions transversely of direction of rotation R (Fig. 1 ). Figs. 3a-3f and 5a-5f exemplifies alternative embodiments of geometries and curvatures, e. g. the placement and number of concave and convex portions of the long side surfaces L of the grinding elements 1.

Fig. 4a illustrates a grinding element 1 having the form of a three- dimensional body. The body is defined by a base surface B and a work piece engaging surface A. The surfaces A and B are substantially parallel and spaced apart by two long side surfaces L. The long side surfaces extend in a longitudinal direction of the grinding element 1. In a transversal direction the surfaces A and B are spaced apart by a short side surface S. The short side surface S has a length m-i. Fig. 4a shows that one of the long side surfaces L may, according to one embodiment have one concave portion and one convex portion. According to an alternative embodiment the opposing and parallel long side surface L has respectively a convex and concave portion so that an S-shaped configuration of the grinding element appears. As shown by the Figs 4a-4b the length m₂ of the grinding element 1 in a longitudinal direction may vary in proportion to the width m₃, i.e. the total transversal extent of the grinding element, to give rise to different curvatures and geometries of the grinding element 1. In one embodiment is the length m₂ twice the width m₃, in another embodiment it is at least four times, in an alternative embodiment at least six times or in yet an alternative embodiment at least eight times or in yet an alternative embodiment at least ten times the width ITi₃. Also, according to an alternative embodiment, the number of concave and convex portions can vary.

The width m₁ of the short side surface S, may be less than 50% of the width m₃ of the grinding element 1.

The parallel base surface and the work piece engaging surface A may, according to one embodiment form a geometric body which has an essentially constant cross section.

In an alternative embodiment, a grinding element 1 may have a work piece engaging surface a with a varying topography. It shall however be understood that the varying topography may be designed in any way suitable for the purpose of the present disclosure.

Such a work piece engaging surface may have a varying topography with a total top surface having an area which is less than 30% of an area of the base surface. By the varying topography of the top surface of the engagement surface, a smaller portion of the engagement surface engages the work piece, i.e. the floor surface, which provides a way of reducing the threshold friction at the onset of grinding, and thereby a reduction in the applied forces and hence the heat evolved during start up. This may also give rise to a more gentle start up. Furthermore, with a smaller initial engagement surface, the matrix material will be removed more quickly, such as to expose the abrasive particles and provide optimal grinding/polishing performance.

By "work piece engaging surface" is meant the outermost portion of the grinding element, which engages the work piece. The summits of the protruding parts of the varying topography of the work piece engaging surface hence forms the top surface of the work piece engaging surface. The top surface area is formed of several protruding parts of the work piece engaging surface The total top surface may have an area which is less than 20% of the area of the base surface, or less than 10% or less than 5% or less than 2% of the area of the base surface.

The varying topography of the top surface may present, in a side projection, at least two parallel ridges, spaced apart by a trough, extending between a pair of opposing sides of the body, wherein the ridges has a rounded top portion.

By forming the top surface as rounded ridges and troughs there is a way of creating the varying topography of the top surface of the engagement surface for the reduction of the threshold friction.

The varying topography of the top surface, may in an alternative embodiment present an elevated embossed pattern.

The grinding element may be formed by a metal bond diamond material, i.e. with a matrix substantially formed of metal material. In the alternative, the grinding element may be formed by a resin bond diamond material, i.e. with a matrix substantially formed of polymer material.

Fig. 5a illustrates a grinding element having a generally S-shaped body with rounded ends.

Fig. 5b illustrates a grinding element having a generally S-shaped body with substantially straight ends.

Fig. 5c illustrates a grinding element having a body with a narrow central portion, flanked by a pair of wider, generally rounded portions.

Fig. 5d illustrates a grinding element having a generally narrow body, with a wider, rounded central portion. Fig. 5e illustrates a grinding element having a generally zig-zag- shaped body.

Fig. 5f illustrates a grinding element having a pair of narrow, substantially straight portions, which are substantially parallel and displaced in a direction transversely of the straight portions. The straight portions are connected at their adjacent ends, such as to form a stylized S-shape or simple zig-zag-structure.

The difference between the upper portion and lower portion of the varying topography of the engagement surface is less than 0,6 mm, alternatively less than 0,5 mm, or less than 0,4 mm or less than 0,3 mm.

According to an alternative embodiment, at least two grinding elements 1 may be arranged on the holder plate 2.

Examples of holder plates are provided in EP-1 321 233 and WO 2004/108352. One particulary advantageous embodiment of the present invention involves such a holder plate as disclosed in WO 2004/108352.

Claims

1. A grinding element (1 ) adapted to be arranged on a holder plate (2), for grinding and/or polishing hard floor surfaces, wherein the grinding element (1 ) has the form of a geometric body defined by: a substantially oblong base surface (B), a work piece engaging surface (A), spaced apart from the base surface (B), and at least two spaced apart long side surfaces (L) extending substantially along a longitudinal direction of the grinding element and substantially between the base surface (B) and the work piece engaging surface (A) c h a r a c t e r i s e d in that the long side surfaces (L) present a respective concave surface portion.

2. The grinding element (1 ) according claim 1 , wherein the base surface (B) and the work piece engaging surface (A) are substantially parallel and of substantially the same size, such that the geometric body thus formed presents an essentially constant cross section.

3. The grinding element according to claim 1 or 2, wherein at least one of the long side surfaces (L) presents at least one substantially convex surface portion.

4. The grinding element (1 ) according to any one of the preceding claims, wherein the grinding element (1 ) has at least two long side surfaces (L) and wherein the at least two long side surfaces (L) both present a substantially concave portion and a substantially convex portion and wherein the at least two long side surfaces are substantially parallel.

5. The grinding element (1 ), according to claim 4, wherein the substantially convex portion of one of the two long side surfaces (L) is aligned with the concave portion of the other long side surface (L), and vice versa.

6. The grinding element (1 ), according to any one of the preceding claims, wherein the long side surfaces (L) are arranged on opposite sides of the grinding element.

7. The grinding element (1 ) according to any one of the preceding claims, wherein the work piece engaging surface (A) has a varying topography.

8. The grinding element (1 ) according to any one of the preceding claims, wherein the length (m₂) of the grinding element (1 ) in a longitudinal direction is at least two times the width (m₃) of the grinding element in a transversal direction, or at least four times, or at least six times or at least eight times or at least ten times the width (m₃) of the grinding element in a transversal direction.

9. The grinding element (1 ) according to any of the preceding claims, wherein the grinding element (1 ) presents at least one short side surface (S) having a width (ITi₁), which is less than 50% of the total transversal extent of the grinding element (m₃), as seen in a direction transversely of the longitudinal direction.

10. The grinding element (1 ) according to any of the preceding claims, wherein the grinding element (1 ) is formed by an essentially homogenous material matrix with abrasive particles dispersed throughout.

1 1. The grinding element (1 ) according to claim 10, wherein the grinding element (1 ) is formed by a metal bond diamond material.

12. A tool (4) for grinding and/or polishing hard floor surfaces comprising a holder plate (2), on which holder plate (2) at least one grinding element (1 ) as claimed in any one of the preceding claims is arranged.

13. The tool (4) for grinding and/or polishing hard floor surfaces according to claim 1 1 , wherein the tool (4) is configured for a direction of rotation (R) and wherein the grinding element (1 ) is arranged on the holder plate (2) substantially with its longitudinal direction transversely of the direction of rotation (R).

14. The tool (4) for grinding and/or polishing hard floor surfaces according to claim 12 or 13, wherein at least two grinding elements (1 ) are arranged on the holder plate (2).

15. Grinding tool according to any one of claims 12-14, wherein the holder plate presents sides which form an acute angle with each other, and which have undercut flanges that are formed for surrounding engagement with an undercut shoulder arranged on the abrading plate.