EP1019221B1 - Abrasive disk - Google Patents

Description

The invention relates to abrasive flap discs.

Abrasive discs can come in different forms. We can in particular, without limitation, store them in three categories.

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

Other discs consist of a generally rigid support which is provided at its periphery with a working area where hairs are distributed or brushes, for example metallic, in particular so that the plane passing through the work area is substantially parallel to the plane disc, or perpendicular to the axis of rotation of the disc once mounted on the tool.

Others still consist of a support generally rigid and fitted around their periphery, their work area, lamellae made of the conventional abrasive material described above. These slats are fixed by one of their edges to the periphery of the disc, their edges free opposites forming abrasive edges. They are generally tilted and close enough to each other to partially overlap according to a given step. These discs are known by the designation of discs with slats, or under the Anglo-Saxon designation of "flap disc".

The selection of the abrasive disc is done appropriately depending on different parameters, including the nature of the material to be ground (wood, polymer material (plastic), composite material, metal, ...) and the quantity of material to be removed.

There is, however, a problem with the use of abrasive discs recurrent, which is the risk of excessive heating of the part during rectification, harmful heating from different points of view: it can cause the deterioration of the part, its very deformation. The deterioration may in particular be mechanical or thermal. If the room is metallic, there may be a change in the structure of the metal, a metal stainless steel type will tend to turn blue. Overheating can also cause projections of high temperature material waste hazardous to the operator or his environment.

It is known from US Pat. No. 3,628,292 an abrasive disc provided with a coating comprising abrasive grains in a resin binder. The disc has bumps and recesses that alternate radially. he is also known from US Pat. No. 5,197,249 a segmented abrasive disc which comprises Abrasive-free areas to extend the life of the disc.

It is also known from US Pat. No. 4,679,360, which forms the basis for the preamble of claim 1, an abrasive disc with lamellae, each lamella being in contact with the two neighboring lamellae.

The invention therefore aims to improve the design of the discs abrasives, especially to overcome the drawback mentioned above, by achieving to limit the heating of the parts to be rectified.

The subject of the invention is an abrasive disc according to claim 1.

For the purposes of the invention, “disc” is understood to mean a part relatively rigid which is adapted to be mounted on a susceptible shaft to be animated with a rotary movement. This term is not limited to forms purely circular. It includes the materials that we associate with rigid parts, in particular for mounting on angle grinders. The disc can be flat or curved.

For the purposes of the invention, the term “work area” means the area of the disc likely to come into contact with the workpiece, when the abrasion operation, an area generally extending radially from the edge outside of the disc up to a certain distance from its center: For flap discs, this zone generally extends from the outer edge up to at most 2/3 of the disc radius, area that can be according to a plane raised relative to the plane passing through the center disc in the case of slats.

For the purposes of the invention, the term “active” zone includes the part of the work area actually capable of operating abrasion, as opposed to "inactive" zones. The “active” zones are thus those where are localized slats, areas "Inactive" being generally constituted by the very support of the disc, not functionalized and / or by any part attached to the support, passive towards abrasion, but able to participate in the construction of the disk, in particular to keep some of its elements in place constitutive.

For the purposes of the invention, "continuous" means that in the area considered, that is to say the "inactive" zone of the work zone, the disc has no openings / holes going right through it, on any its thickness. Preferably, the abrasive discs according to the invention do not are drilled only in their center for mounting on the tool.

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

It turned out that this slightest warming up did not take place in the end little or no, to the detriment of the effectiveness of the tool, the time required to the correction is not significantly lengthened, or even reduced. Thus, reducing the heating can avoid the change of phase of the metal constituting the part to be rectified, avoid modification of its ductility which slows down the grinding work.

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

Preferably, the working area of the disc according to the invention is breaks down into a plurality of "active" zones separated from each other others, by one or more of the “inactive” zones. Optimally, we adopt a distribution of "active" and / or "inactive" zones which is regular all around the work area. A lot of configurations are possible: we can have alternating zones active and inactive, for example by segmenting the work area of concentrically. We can also have an alternation of active zones and inactive radially distributed, segmented by dividing lines coinciding with the spokes of the disc, dividing lines possibly also not straight. We can also have a work area globally "active" (reciprocally "inactive"), interrupted locally by “inactive” work areas (conversely "Active") whose contours are in the form of a closed line, with various geometric shapes, for example in circular form.

It is however necessary that the disc has sufficient efficiency, the "active" zones must be sufficiently large compared to the entire work area, their surface being chosen according to the desired performance and may vary depending on the applications referred. We therefore prefer that the “active” zone or all of the zones "Active" constitutes 10 to 90% of the work area, in particular 40 to 80%, and preferably 50 to 70% thereof.

These percentages refer to the measurement of the area of the actually abrasive work, i.e. the surface of the disc support to which are attached grouped abrasive elements (lamellae).

The invention can be applied both to discs whose support is more of a flexible type and should generally be associated with a room rigid for mounting on the tool only to discs whose support is rigid enough in itself to be mounted directly on the tool.

The abrasive means are lamellae, such as described above, fixed by one of their edges around the perimeter of the disk.

The support is generally rigid, especially made of plastic / reinforcing fibers such as glass fibers or metal.

The invention relates to the abrasive discs of the lamella type, preferably having a rigid support pierced with sound center for its assembly, its working area being continuous and comprising a plurality of abrasive-coated lamellae 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, more than one of the strips is lacking contact with at least one of the other two neighboring lamellae who are "active", ie actively participating in the function abrasive disc.

We thus find in the configuration of a flap disc having the important technical characteristic generalized above, namely that the "active" area of the work area is in fact discontinuous, interrupted to clear at least one non-abrasive continuous zone: in the usual configuration, all the slats are inclined so as to be partially overlap, thereby creating an abrasive surface passing through each of the edges of the lamellae, that is to say the edge of the lamellae opposite to the one fixed to the support. In the invention, on the contrary, there is more than one lamella which is not in this case and which interrupts the continuity of the zone abrasive, and this without having to radically modify the structure and the method of manufacturing flap discs: in the areas without slats, we find the continuous support guaranteeing the rigidity and integrity of the entire disc.

Preferably, it is provided that the edge attached to the support of this lamella is separated from the edge of the neighboring active lamella with which it has no contact at a distance at least equal to the height of the lamellae.

The slats can thus be divided into at least two groups at least two slats each, with a distance between two groups of slats greater than the distance between two slats of the same group at least a factor of 2, especially at least a factor of 4.

According to a preferred embodiment of the invention, each group of slats have at least five, all inclined 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 from support the previous slat and keep it at the desired angle of inclination ("Previous" or "next" refer arbitrarily to the way the slats follow one another in the work area with reference to the direction of rotation provided for the disc). The alignment being interrupted by this distribution into groups, each of the "first" lamellae of groups (always with reference to the direction of rotation of the disc) may have to be supported by additional means to be held in position, this medium can be a wedge, index, glue points, regularly distributed and fixed to the surface of the support or forming an integral part of it last, before depositing the slats.

It can also be provided that each group of lamellae comprises a sufficiently large number of lamellae to accept that the first strip collapses, becomes de facto "inactive" in term abrasion but serving as a wedge "in situ" for the other lamellae group, or even for the last lamella of the previous lamella group (neighbour).

The flap disc according to the invention preferably comprises at least at least part, in particular all of the slats inclined according to a plane making an angle α of at least 10 °, in particular 15 to 60 ° with the plane going through the work area of the disc.

According to a preferred configuration of the invention, the edge of the lamellae opposite the edge fixed to the support makes an abrasive "edge" by which can pass an axis making an angle β with respect to the radius of the disc. This angle may be zero, the axis passing through the edge coinciding with the radius. He can too be non-zero, angle of at least ± 5 °, in particular from ± 5 to ± 25 °. Conventionally, it is positive if the measured angle of the axis passing through the radius edge 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 at minus 1,000 revolutions per minute (including a maximum of 13,000 revolutions per minute) and for abrasion for material removal.

• figure 1 : un disque abrasif souple qui n'est pas selon l'invention en vue de côté,
• figure 2 : un disque abrasif rigide à lamelles selon l'invention en vue de dessus,
• figure 3 : le disque à lamelles de la figure 2 en vue de côté.

The invention will be detailed below with the aid of nonlimiting examples illustrated by the following figures:

• FIG. 1: a flexible abrasive disc which is not according to the invention in side view,
• FIG. 2: a rigid abrasive disc with lamellae according to the invention in top view,
• Figure 3: the flap disc of Figure 2 in side view.

All these figures are very schematic in order to facilitate the reading.

FIG. 1 represents a flexible abrasive disc 1, with a diameter about 15 cm, with a canvas support 2 primed so suitable, partially covered with an abrasive coating 3 comprising a layer of phenol-formaldehyde binder, then a layer of grains in 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 its mounting by clamping on the axis of a tool. The work area extends from its periphery, here circular, up to a certain distance from the mounting orifice, according to a circle represented by dotted lines. The bravery area presents so here a substantially annular shape. It breaks down into different segments: three “active” zones 5 provided with the coating 3 described previously, alternating with three “inactive” zones 6 devoid of the coating 3 and leaving the support visible. The lines (i) sharing the “active” zones and “inactive” zones thus divide the zone of work in a plurality of ring portions. Each work area is thus delimited by two dividing lines, the one (i) which is the first to attack the workpiece according to the direction of rotation of the disc symbolized by an arrow, is preferably not radial. This avoids that the entire leading edge of each active area, when the disc is put in rotation, do not come into contact with the part at the same time. Optionally, as shown in Figure 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 discs after cutting, for example). The sum of the areas of the active zones 5 corresponds to approximately 60% of the complete work area including the "active" areas and areas "Inactive".

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

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

It is still part of the represented disc in Figure 1 where the "active" zones are raised relative to the zones inactive, inactive areas are also expected to have a abrasive coating, which has become de facto "inactive" due to its position in the Work zone.

Figures 2 and 3 describe the preferred embodiment of the invention, namely a flap disc distributed in different groups. The disc shown includes a rigid nylon support 11 reinforced with plastic composite with a depression centered on its orifice central assembly 10. 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, lamellae 13 protruding from 0 to 5 mm from the periphery of the support 11, slats aligned on a circle C centered on the center O of the disc and partially overlapping. This flat support area covered by the slats, shaped approximately annular, constitutes the working area of the disc.

These lamellae are made of a flexible abrasive material of the type of that constituting the flexible disk of figure 1. The diameter of the support is about 10.5 cm. The slats are L 25 mm wide, h high 17 mm and thickness e of approximately 0.5 mm. They are inclined at an angle α about 35 to 40 ° from the plane passing through the work area. The abrasive edges 12 of each of the first lamellae x1 of the groups of slats are along an axis offset by an angle β of about -10 ° relative to at radius R passing through the fictitious center O of the disc (it is negative, according to conventions described above taking into account the direction of rotation of the disk). We see from the two figures that the slats are distributed in four groups g1, g2, g3, g4 of approximately 15 to 18 lamellae, making a total of fifty lamellae (if they were all contiguous, and overlapping continuously, as is known, there would be approximately 80). To simplify Figure 2, all the slats of the groups g1, g2, g3 and g4 have not been shown, the dotted lines around the periphery of 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 13 (its edge which is attached to the support) is a distance measured by following the circumference of the disc d1 about 2 mm from the base of the adjacent lamella x2. The base of the first lamella x1 of each group is distant from the base of the last lamella of the previous group x3 by a distance d2 measured in depending on the circumference of the disc about 30 to 50 mm. So we find the alternation of "active" zones, made up of groups of lamellae g1, g2, g3, g4 and “inactive” zones i1, i2, i3, i4 which are continuous and without lamellae.

In each group, the first strip rests on a wedge 14. These shims are distributed and fixed to the support before adding the slats (Au instead of being reported, we can also provide that the support itself is locally deformed appropriately). It may be only one excess glue. They are optional: when the slats in each of the groups are sufficiently numerous, the first lamella, which cannot rest on the previous lamella, can tend to collapse and become "inactive" vis-à-vis the abrasive effect. However, it will allow to prevent the fall of the following ones, which then serves as a hold. In operating on the tool, this household disc, in zones i of the periods of rest limiting overheating. There is a difference in H levels significant between on the one hand the plane in which the edges are located abrasive 12 lamellae and secondly the plane of the support in the area of work without slats (difference H equal to h.sin α), which can promote the formation of induced ambient air currents in the "channels" formed in the inactive zones i delimited by the first and last slats of the two groups of slats surrounding them, the air currents allowing a significant cooling of the part. 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 bluing of metallic parts rectified by this type of disc slats, and in a relatively simple way: the support remains unchanged (or almost unchanged if shims are required), the abrasive material remains in the form of lamellae known per se. Only changes their distribution, which can take a wide variety of forms not limited to those shown in FIGS. In addition, for a given abrasion job, the disc according to the invention "consumes" less abrasive means, and can even some applications, reduce the time required for this work.

Claims (13)

1. Abrasive disk comprising a preferably rigid support (11) perforated in its centre (10) for its fitting, a continuous working area and comprising a plurality of plates (13) having an abrasive coating fixed by one of their edges to the periphery of said support and aligned substantially in accordance with a circle centred on the axis of the disk, characterized in that more than one of the plates (x1) has no contact with at least one of its two neighbouring, active plates (x2), so that the working area is subdivided into a plurality of active areas (5, g1, g2, g3, g4) provided with plates and separated from one another by a plurality of continuous, inactive areas having no plates (6, i1, i2, i3, i4) with a regular distribution of the active and inactive areas, all the active areas (5) being in relief compared with the inactive areas (6).
2. Abrasive disk according to claim 1, characterized in that the total of the active areas represents 40 to 80% of the working area.
3. Abrasive disk according to one of the preceding claims, characterized in that it is flexible and combined with a rigid fixing element for its fitting to the tool.
4. Abrasive disk according to one of the claims 1 or 2, characterized in that it is rigid and can be fitted directly to the tool.
5. Disk according to one of the preceding claims, characterized in that the edge of the plate (x1) attached to the support is separated from the edge of the neighbouring plate (x2) with which it has no contact by a distance (d2) at least equal to the height (h) of the plates.
6. Disk according to one of the preceding claims, characterized in that the plates are subdivided into at least two groups of at least two plates each, with a distance (d2) between two groups of plates (g1, g2) exceeding the distance (d1) between two plates of the same group, with a ratio (d2/d1) of at least 2 and in particular at least 4.
7. Disk according to claim 6, characterized in that each group of plates (g1, g2, g3) has at least 5 plates all inclined relative to the plane passing through the working area of the disk and arranged in such a way that their abrasive coatings partly overlap, preferably with a ratio of the height of the plates (13) to the distance between two plates of a same group (h/d1) of at least 4.
8. Disk according to one of the claims 6 or 7, characterized in that at least one of the groups (g2) of plates (13) is provided with at least one adjusting means (16).
9. Disk according to claim 8, characterized in that the adjusting means (16) are fixed to the support (11) and maintain in position the first plate (x1) of each group, particularly in the form of a shim, an index or adhesive points.
10. Disk according to claim 9, characterized in that the final plate of each group serves as an inactive adjusting means for the group and/or the neighbouring group.
11. Disk according to one of the preceding claims, characterized in that at least part and in particular all the plates are inclined in accordance with a plane forming an angle α of at least 10°, particularly 15 to 60°, with the plane passing through the working area of the disk.
12. Disk according to one of the preceding claims, characterized in that the edge of the plates (13) opposite to the edge fixed to the support forms a sharp edge (12) through which passes an axis forming an angle β, relative to the radius of the disk, which is zero or at least ± 5°, particularly ±5 to ±25°.
13. Application of the disk according to one of the preceding claims to the grinding of parts with limiting heating.

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