EP1019221A1

EP1019221A1 - Abrasive disk

Info

Publication number: EP1019221A1
Application number: EP98946537A
Authority: EP
Inventors: Hervé Charrue; Marc Robert
Original assignee: Norton SA France
Current assignee: Saint Gobain Abrasifs SA; Saint Gobain Ceramics and Plastics Inc
Priority date: 1997-10-01
Filing date: 1998-10-01
Publication date: 2000-07-19
Anticipated expiration: 2018-10-01
Also published as: AU9355198A; IT1297017B1; FR2768955A1; WO1999016583A1; EP1019221B1; IL135403A0; ES2188015T3; IL135403A; DE69809579D1; ITMI972868A1; FR2768955B1; DE69809579T2

Abstract

The invention concerns an abrasive disk comprising a support perforated in its centre for being mounted, and whereof the working zone comprises at least an 'active' zone provided with abrasive means and at least a continuous 'inactive' zone devoid of abrasive means.

Description

ABRASIVE DISC

The invention relates to abrasive discs, in particular all those which are used on portable machines called "grinders", as well as on more specialized machines of the angle grinder type.

Abrasive discs can come in different forms. We can in particular, without limitation, fall into three categories.

The most common discs are those made of materials belonging to the family of conventional abrasives applied, namely a superposition of generally three elements: a support, more or less rigid, on which is disposed a layer of abrasive particles secured to the support by the minus one, and usually two layers of binder. These materials are then cut to the desired shape, generally circular, and pierced in their center with an opening allowing their fixing by clamping to the axis of the tool, directly, or by means of a rigid part if the support is flexible, rigid part sometimes designated under the Anglo-Saxon name of "backing plate" or even "pad".

Other discs consist of a generally rigid support which is provided at its periphery with a working area in which bristles or brushes, for example metal, are distributed, in particular so that the plane passing through the area of work is substantially parallel to the disk plane, or perpendicular to the axis of rotation of the disk once mounted on the tool. Still others also consist of a generally rigid support and provided on their periphery, their working area, with lamellae made of the conventional abrasive material described above. These lamellae are fixed by one of their edges to the periphery of the disc, their opposite free edges forming abrasive edges. They are generally inclined and close enough to each other to partially overlap in a given step. These discs are known under the designation of flap discs, or also under the Anglo-Saxon designation of "flap dise".

The selection of the abrasive disc is done appropriately according to various parameters, in particular the nature of the material to be ground (wood, polymer material (plastic), composite material, metal, ...) and the amount of material to be removed.

The use of abrasive discs comes up against a recurring problem, which is that of the risk of excessive heating of the part during grinding, harmful heating from different points of view: it can lead to deterioration of the part, its deformation even. The deterioration may be in particular mechanical or thermal. If the part is metallic, there may be a change in the structure of the metal, a metal like stainless steel will tend to turn blue. Heating can also cause waste material to be thrown at high temperatures which is dangerous for the operator or his environment. The invention therefore aims to improve the design of the abrasive discs, in particular to overcome the drawback mentioned above, by managing to limit the heating of the parts to be ground.

The subject of the invention is an abrasive disc comprising a support pierced in its center for its mounting and such that its working area comprises at least one "active" area provided with abrasive means (s) and at least one area " inactive ”which is continuous and devoid of abrasive means.

Within the meaning of the invention, the term "disk" includes a relatively rigid part which is adapted to be mounted on a shaft capable of being driven by a rotary movement. This term is not limited to purely circular shapes. It includes the materials that we associate with rigid parts, in particular for mounting on angle grinders.

The disc can be flat or curved.

Within the meaning of the invention, the term “working zone” is understood to mean the zone of the disc capable of coming into contact with the part to be rectified, during the abrasion operation, zone generally extending radially from the outer edge. of the disc up to a certain distance from its center: in the case of flexible flat discs, the working area generally constitutes the entire surface of the abrasive disc. In the case of brush or flap discs, this zone generally extends from the outer edge up to at most 2/3 of the radius of the disc, which zone may be convex in the case of brushes, or according to a plane raised relative to the plane passing through the center of the disc in the case of lamellae.

Within the meaning of the invention, by “active” zone is understood the part of the work zone effectively capable of operating abrasion, as opposed to “inactive” zones. The “active” zones are thus those where the lamellae, brushes or abrasive particles are located, the “inactive” zones generally being constituted by the very support of the disc, non-functionalized and / or by any part attached to the support, passive screw -with respect to abrasion, but which can participate in the construction of the disc, in particular in keeping some of its constituent elements in place.

For the purposes of the invention, “continuous” means that in the zone considered, that is to say the “inactive” zone of the working zone, the disc is devoid of holes / orifices passing right through it, over its entire thickness. Preferably, the abrasive discs according to the invention are only drilled in their center for mounting on the tool.

Very advantageously, the abrasive discs thus defined significantly minimize overheating of the parts during their grinding. When the disc is rotated, the area of the workpiece to be ground is no longer in permanent contact with the abrasive means with which the disc is provided, as long as the operator exerts pressure from the disc on the workpiece: periodically , the part will be "at rest" during passage of the inactive zone (s) of the working area of the disc, resulting in less heating.

It turned out that this slightest heating did not ultimately take place, or only slightly, to the detriment of the effectiveness of the tool, the times required for grinding not being significantly lengthened, or even reduced. Thus, reducing overheating can make it possible to avoid the phase change of the metal constituting the part to be ground, to avoid the modification of its ductility which slow down the grinding work.

More than a limitation of heating, we can even speak of a real cooling effect if we appropriately design the relative arrangement of the "active" and "inactive" zones, in order to create / promote the formation of currents. ambient air induced by the rotation of the disc at the inactive zones, these air currents coming to cool the part to be ground / disc interface. It is thus advantageously possible to provide that the “active” areas are in relief with respect to the “inactive” areas in the work area. This is also the case when the working area is defined by the periphery of the disc along a plane, with the inactive areas consisting simply of the uncoated support, not provided with abrasive elements: there is de facto an extra thickness in the areas active, due to the thickness of the coating containing the coating particles, or the thickness formed by the projection along the plane perpendicular to that of the working area of the height of the inclined blades, or else of the defined thickness by the height of the abrasive bristles or brushes. This difference in “thickness” of the disc between “active” and “inactive” areas can be further accentuated by raising the “active” areas, in particular by adapting the shape of the support of the disc.

Preferably, the working area of the disc according to the invention is broken down into a plurality of “active” areas separated from one another, by one or more of the “inactive” areas. Optimally, a distribution of the “active” and / or “inactive” zones is adopted which is regular over the entire periphery of the work zone. Many configurations are possible: we can have alternating zones active and inactive, for example by segmenting the work area concentrically. It is also possible to have an alternation of active and inactive zones distributed radially, segmented by dividing lines coinciding with the radii of the disc, dividing lines possibly also being non-linear. We can also have a generally “active” work area (reciprocally “inactive”), interrupted locally by “inactive” work areas (reciprocally “active”) whose contours are in the form of a closed line, with shapes various geometries, for example in circular form. However, it is necessary for the disk to have sufficient efficiency, the “active” zones having to be sufficiently large with respect to the whole of the working zone, their surface being chosen as a function of the desired performance and being able to vary according to the applications. targeted. It is therefore preferred that the “active” zone or all of the “active” zones constitute 10 to 90% of the work zone, in particular 40 to 80%, and preferably 50 to 70% thereof.

These percentages refer to the measurement of the surface of the effectively abrasive working area, that is to say the surface of the support of the disc which, in the working area, is covered with abrasive elements (particles) or which are attached grouped abrasive elements (lamellae, brushes).

The invention can be applied both to discs whose support is more of the flexible type and which must generally be associated with a rigid piece for mounting on the tool than to discs whose support is sufficiently rigid in itself. even so that it can be mounted directly on the tool.

As mentioned above, the abrasive means with which the discs according to the invention are fitted can be chosen from the coatings with abrasive particles bonded to the support of the discs. The abrasive particles may in particular be chosen from grains made of ceramic, zirconium oxide, aluminum oxide, silicon carbide, flint.

The abrasive grains in a layer are in particular joined to the support by at least one layer of binder, and generally two layers of binder, the first layer deposited on the support making it possible to deposit the abrasive grain and ensuring the basic adhesion of the grains, the second layer covers the layer of abrasive grains to anchor them. The binders are usually of two types: either based on synthetic resin of the urea-formaldehyde or phenol-formaldehyde type, or based on natural or organic glue. It is also possible to provide a final layer based on agent (s), for example with an anti-fouling function or promoting cold cutting.

The attachment of the abrasive grains to the support can also be obtained by any means known to those skilled in the art, for example by application of a high frequency.

The abrasive means can also be in the form of bristles or brushes (grouping of several bristles), generally metallic and implanted in the support.

The abrasive means can also be strips, as described above, fixed by one of their edges to the periphery of the disc.

In the first case, the support is generally flexible, in particular based on paper, canvas, non-woven textile fibers, glass or metal fibers, or the superposition of at least two of these materials, treated before depositing the abrasive coating. It is associated with a rigid element (“backing plate” or “pad”) for mounting on the tool, rigid element usually made of metal or possibly reinforced plastic material.

In the latter two cases, the support is generally rigid, in particular of plastic / reinforcing fiber composite of the glass fiber or metal type.

The invention relates more particularly to abrasive discs of the lamella type, comprising a preferably rigid support pierced at its center for its mounting, its working area being continuous and comprising a plurality of lamellas with abrasive coating fixed by one of their edges at the periphery of said support and aligned substantially in a circle centered on the axis of the disc. According to the invention, at least one of the strips has no contact with at least one of the other two neighboring strips which are "active", ie actively participating in the abrasive function of the disc.

We thus find in the configuration of a flap disc having the important technical characteristic generalized above, namely that the "active" zone of the working zone is in fact discontinuous, interrupted to release at least one continuous non-abrasive zone: in the usual configuration, all the slats are inclined so as to partially overlap, and thus create an abrasive surface passing through each of the edges of the slats, that is to say the edge of the slats opposite to that fixed to the support. In the invention, there is on the contrary at least one strip which is not in this case and which interrupts the continuity of the abrasive zone, and this without having to very radically modify the structure and the method of manufacture of the discs with slats: in the areas thus devoid of slats, there is the continuous support guaranteeing the rigidity and integrity of the entire disc.

Preferably, provision is made for the edge attached to the support of this strip to be separated from the edge of the active neighboring strip with which it is devoid of contact by a distance at least equal to the height of the strips. The lamellae can thus be divided into at least two groups of at least two lamellae each, with a distance between two groups of lamellae greater than the distance between two lamellae of the same group by at least a factor of 2, in particular of at least a factor of 4.

According to a preferred embodiment of the invention, each group of lamellae comprises at least five of them, all inclined relative to the plane passing through the working area of the disc and arranged so that their abrasive coatings partially overlap, with in particular a ratio (slat height / distance between two slats) in the same group of at least 4. It may be necessary to provide that at least one of these groups is provided with a so-called wedging means. Indeed, in the usual configuration, the slats are aligned along a circle, each slat coming support the previous slat and keep it at the desired angle of inclination

("Previous" or "next" refer, arbitrarily, to the way in which the slats succeed each other in the working area with reference to the direction of rotation provided for the disc). The alignment being interrupted by this division into groups, each of the “first” lamellae of the groups (always with reference to the direction of rotation of the disc) may have to be supported by an additional means in order to be held in position, this means possibly being a wedge , an index, dots of glue, regularly distributed and fixed to the surface of the support or forming an integral part of the latter, before depositing the strips therein.

It can also be provided that each group of lamellae comprises a sufficiently high number of lamellae so that it can be accepted that the first lamella collapses, becoming de facto "inactive" in terms of abrasion but serving as a wedge "in situ For the other lamellae of the group, or even for the last lamella of the preceding group of lamellae (neighbor).

The flap disc according to the invention preferably comprises at least a part, in particular all of the slats inclined according to a plane making an angle α of at least 1 0 °, in particular 1 5 to 60 ° with the plane passing through the disc work area.

According to a preferred configuration of the invention, the edge of the lamellae opposite the edge fixed to the support forms an abrasive "edge" through which an axis can pass making an angle β relative to the radius of the disc. This angle can be zero, the axis passing through the edge coinciding with the radius. It can also be non-zero, angle of at least ± 5 °, in particular from ± 5 to ± 25 °. Conventionally, it is positive if the measured angle from the axis passing through the edge to the radius is in the same direction as the direction of rotation of the disc once mounted on the tool. (An angle β thus measured chosen negative is advantageous to facilitate cooling by ambient air). All the discs according to the invention therefore make it possible to limit overheating during the rectification of the parts. In general, they are rather suitable for high rotational speeds, for example from minus 1000 revolutions per minute (in particular at most 1300 revolutions per minute) and for abrasion for removal of material.

The invention will be detailed below with the aid of nonlimiting examples illustrated by the following figures: Ω FIG. 1: a flexible abrasive disc according to the invention in side view,

O Figure 2: a rigid abrasive disc with lamellae according to the invention in top view,

O Figure 3: the flap disc of Figure 2 in side view. All these figures are very schematic in order to facilitate reading.

FIG. 1 represents a flexible abrasive disc 1, with a diameter of approximately 15 cm, comprising a cloth support 2 suitably primed, partially covered with an abrasive coating 3 comprising a layer of phenol-formaldehyde binder, then a layer of grains of zirconium oxide and finally a second layer of binder similar to the first. This disc is pierced in its center with an orifice 4 intended for mounting by clamping on the axis of a tool. The work area extends from its circumference, here circular, to a certain distance from the mounting orifice, in a circle represented by dotted lines. The bravery zone therefore here has a substantially annular shape. It is broken down into different segments: three "active" zones 5 provided with the coating 3 described above, alternating with three "inactive" zones 6 devoid of the coating 3 and leaving the support visible. The lines (i) dividing the “active” zones and the “inactive” zones thus cut the working zone into a plurality of ring portions. Each work zone is thus delimited by two dividing lines, the one (i) which is the first to attack the part to be rectified as a function of the direction of rotation of the disc symbolized by an arrow, is preferably non-radial. This prevents the entire leading edge of each active area, when the disc is rotated, from coming into contact with the part at the same time. Optionally, as shown in FIG. 1, the “active” zones 5 are in relief, in the sense that the support has been deformed so as to raise these zones compared to the inactive zones of a given height (deformation by stamping of the discs after cutting, for example). The sum of the areas of the active areas 5 corresponds to approximately 60% of the complete work area comprising the “active” areas and the “inactive” areas.

This disc works in association with a rigid support made of reinforced plastic, in a known manner, if necessary of a shape adapted to take account of the relief of the disc on its rear face.

During the grinding operation, the part to be grinded is periodically at "rest" during the passages over the inactive zones 6, thus limiting friction and therefore heating which results therefrom.

It is also within the framework of the invention that, in the case represented in FIG. 1 where the “active” zones are raised relative to the inactive zones, provision is made for the inactive zones to be provided also with an abrasive coating, de facto became “inactive” due to its position in the work area.

Figures 2 and 3 describe the preferred embodiment of the invention, namely a flap disc distributed in different groups. The disc shown comprises a rigid support 11 nylon reinforced with plastic composite having a depression centered on its central mounting hole 1 0. On its periphery, in particular over a width corresponding approximately to 1/3 or half of its radius R , are fixed with a layer of glue of the strips 1 3 projecting from 0 to 5 mm from the periphery of the support 1 1, strips aligned on a circle C centered on the center O of the disc and partially overlapping. This planar support area covered by the strips, of approximately annular shape, constitutes the working area of the disc.

These strips are made of a flexible abrasive material of the type of that constituting the flexible disc of FIG. 1. The diameter of the support is approximately 1 0.5 cm. The strips are of width L 25 mm, of height h of 17 mm and of thickness e of approximately 0.5 mm. They are inclined at an angle α of approximately 35 to 40 ° relative to the plane passing through the working area. The abrasive edges 1 2 of each of the first lamellae x1 of the lamella groups are along an axis offset by an angle β of about -1 0 ° relative to the radius R passing through the fictitious center O of the disc (it is negative, according to the conventions described above taking into account the direction of rotation of the disc). We see from the two figures that the slats are divided into four groups g1, g2, g3, g4 of about 1 5 to 1 8 slats, or in all about fifty slats (if they were all contiguous, and overlapping continuously, as is known, they would be approximately 80). To simplify Figure 2, all the lamellae of groups g1, g2, g3 and g4 have not been shown, the dotted lines around the periphery of the disc symbolizing the lamellae not shown. The arrows indicate the direction of rotation of the disc once mounted on the tool.

In each group, the base of each strip 1 3 (its edge which is fixed to the support) is distant by a distance measured by following the periphery of the disc d 1 of approximately 2 mm from the base of the adjacent strip x2. The base of the first lamella x1 of each group is distant from the base of the last lamella of the preceding group x3 by a distance d2 measured by following the periphery of the disc of approximately 30 to 50 mm. We therefore find the alternation of "active" zones, formed by the groupings of lamellae g 1, g2, g3, g4 and "inactive" zones i l, i2, i3, i4 which are continuous and have no lamellae.

In each group, the first strip rests on a block 1 4. These blocks are distributed and fixed to the support before adding the strips (Instead of being added, it is also possible to provide that the support itself is locally deformed by appropriately). It may only be an excess thickness of glue. They are optional: when the lamellae in each of the groups are sufficiently numerous, the first lamella, which cannot rest on the preceding lamella, can tend to collapse and become “inactive” with respect to the effect. abrasive. On the other hand, it will make it possible to prevent the fall of the following ones, then serving itself as a hold. By operating on the tool, this disc cleans, in zones i of rest periods limiting heating. There is a difference in H levels significant between on the one hand the plane in which the abrasive edges 1 2 of the lamellae are located and on the other hand the plane of the support in the working zone devoid of lamellae (difference H equal to h.sin α), which can favor the formation of ambient air currents induced in the "channels" formed in the inactive zones i delimited by the first and last lamellae of the two groups of lamellae framing them, the air currents allowing significant cooling of the room. Note that having chosen a negative β angle is in this context very advantageous: it will facilitate the engagement of ambient air in "these channels". The invention thus offers a solution to the known problem of blue staining of metal parts rectified by this type of flap disc, and in a relatively simple manner: the support remains unchanged (or almost unchanged if shims have to be provided), the abrasive material remains in the form of lamellae known per se. The only change is their distribution, which can take a wide variety of forms not limited to those shown in the figures. In addition, for a given abrasion job, the disc according to the invention "consumes" fewer abrasive means, and may even in certain applications, make it possible to reduce the time necessary for this job.

Claims

REVEIMDICATIONS

1. Abrasive disc (1) comprising a perforated support (2, 1 1) in its center (4, 1 0) for its assembly, characterized in that its working area includes at least one "active" area (5, g 1, g2, g3, g4) provided with abrasive means and at least one “inactive” zone (6, il, i2, i3, i4) which is continuous and devoid of abrasive means and in that in the work zone, the (the ) active zone (s) (5) is (are) in relief in relation to the inactive zone (s) (6).

2. Abrasive disc according to claim 1, characterized in that its working area is broken down into a plurality of “active” areas (5, g 1, g2, g3, g4) separated from one another by one or more of the areas "Inactive" (6, il, i2, i3, i4), preferably with a regular distribution of the "active" and / or "inactive" zones.

3. Abrasive disc according to one of the preceding claims, characterized in that the “active” zone or all of the “active” zones constitutes 40 to 80% of the working zone.

4. Abrasive disc according to one of the preceding claims, characterized in that it is flexible and associated with a rigid fixing element for mounting on the tool.

5. Abrasive disc according to one of claims 1 to 3, characterized in that it is rigid and that it can be mounted directly on the tool.

6. Abrasive disc according to one of the preceding claims, characterized in that the abrasive means are chosen from coatings (3) containing abrasive particles and deposited on the support, strips (1 3) covered with coatings containing abrasive particles and fixed by one of their edges on the support (1 1), bristles / brushes fixed (es) to said support.

7. Abrasive disc, in particular according to one of the preceding claims, comprising a support (1 1) preferably rigid drilled in its center (1 0) for its mounting, its working area being continuous and comprising a plurality of blades (1 3) with an abrasive coating fixed by one of their edges to the periphery of said support and substantially aligned along a circle centered on the axis of the disc, characterized in that at least one of the lamellae (x1) is devoid of contact with at least one of its two adjacent active lamellae (x2).

8. Disc according to claim 7, characterized in that the edge of the strip (x1) attached to the support is separated from the edge of the neighboring strip (x2) with which they are devoid of contact by a distance (d2) at least equal to the height (h) of the slats.

9. Disc according to claim 6, 7, 8, characterized in that the lamellae are distributed in at least two groups of at least two lamellae each, with a distance (d2) between two groups of lamellae (g 1, g2) greater than the distance (d 1) between two lamellae of the same group, with a ratio d2 / d 1 of at least 2, in particular at least 4.

1 0. Disc according to claim 9, characterized in that each group of lamellae (g1, g2, g3) comprises at least 5 lamellae all inclined relative to the plane passing through the working area of the disc and arranged so that their abrasive coatings partially overlap, preferably with a ratio of the height of the lamellae (1 3) to the distance between two lamellae of the same group h / d 1 of at least 4.

1 1. Disc according to one of claims 9 or 1 0, characterized in that at least one of the groups (g2) of lamellae (1 3) is provided with at least one wedging means (1 6).

1 2. Disc according to claim 1 1, characterized in that the wedging means (1 6) are fixed to the support (1 1) and maintain in position the first strip (x1) of each group, in particular in the form of a wedge, index, dots of glue.

1 3. Disc according to claim 1 2, characterized in that the last lamella of each group serves as “inactive” wedging means of said group and / or of the neighboring group.

1 4. Disc according to one of claims 6 to 1 3, characterized in that at least a part, in particular all, of the lamellae is inclined in a plane making an angle α of at least 1 0 °, in particular 1 5 at 60 °, with the plane passing through the disc work area.

15. Disc according to one of claims 6 to 15, characterized in that the edge of the lamellae (13) opposite the edge fixed to the support forms an edge (12) through which passes an axis making an angle β, relative to the radius of the disc, zero or at least ± 5 °, in particular ± 5 to ± 25 °.

16. Application of the disc according to one of the preceding claims to the rectification of parts with limited heating.