EP1248696B1 - Abrasive grindstone and method for making same - Google Patents

Abstract

The invention concerns a grindstone exhibiting good abrasive properties while being inexpensive, consisting of stacked layers (12, 13, 14, 15) comprising at least one layer of abrasive grains (14) which includes juxtaposed zones (14A, 14B) consisting of different abrasive grains, one proximate to the centre of the layer (14) and the other along its external periphery. The method for forming said layer (14) of the stack consists in: making a blank consisting of a first type abrasive grains and a ring consisting of a second type of abrasive grains, the respective inner and outer contours of the blank being geometrically similar; positioning the ring and the blank in inserting position, then in a subsequent step for making the grindstone, pressing the stack of layers. The invention is useful for making cutting-off and surface-treating wheels.

Description

The invention relates to an abrasive wheel of the thin wheel type, comprising several layers of stacked constituents agglomerated by pressure.

Such wheels are made by stacking, generally around a central metal ring, a protective paper disc, a sheet reinforcement generally made of fabric or similar meshed, perforated or dimpled, with a layer of abrasive grains, also with another backing sheet usually fabric or the like, and possibly another disc of paper protection; then the stack is generally heated; then she is pressed, and thus the abrasive grain layer and the mesh reinforcement layers, perforated or dimpled are generally at least partially nested by following the penetration of the abrasive grains into the meshes, perforations or alveoli.

The prior art knows documents GB 1,540,511 and JP 06-312377 grinding wheels corresponding to the preamble of claim 1.

Commonly, these grinding wheels have a remote hub, that is to say that the part of the grinding wheel which is in the immediate vicinity of the central ring does not does not extend in the same plane as the part which surrounds it, and the grinding wheel is mounted on the grinding machine in such a way that this part further away from the ring be the most protruding beyond the machine; the wheel is therefore generally used for surfacing only on the surface on the side opposite to the machine, of this part; for cutting, it is naturally the around the same part that is most requested. It is therefore essential that this part contains very high performance abrasive grains, and unnecessarily expensive that the part close to the ring has the same abrasive grains as is the case with conventional grinding wheels.

Also, during the rotation of the grinding wheel, the circumferential speed abrasive grains close to the periphery is much superior to that of grains more close to the ring, and thus the optimal abrasive for the two regions is not necessarily the same.

The object of the invention is to remedy these drawbacks known wheels, by proposing an abrasive wheel of the wheel type slim, according to the features of claim 1.

Thanks to this structure, the grinding wheel according to the invention can be made from abrasive grains perfectly suited to the function they must ensure even if the grinding wheel is made up of regions of functions different.

• dans la couche de grains abrasifs qui comporte une région s'étendant au voisinage du centre et une région s'étendant le long de la périphérie de la couche, constituées de grains abrasifs différents, ces deux régions sont juxtaposées ;
• dans la couche de grains abrasifs qui comporte des régions juxtaposées constituées de grains abrasifs différents, au moins deux de ces régions sont juxtaposées le long d'une ligne de joint qui présente une forme circulaire ;
• dans la couche de grains abrasifs qui comporte des régions juxtaposées constituées de grains abrasifs différents, au moins deux de ces régions sont juxtaposées le long d'une ligne de joint fermée qui présente une forme non circulaire ;
• la meule comporte au moins deux couches de grains abrasifs dont au moins l'une comporte des régions juxtaposées constituées de grains abrasifs différents, l'une de ces régions s'étendant au voisinage du centre de la couche tandis qu'une autre de ces régions s'étend le long de la périphérie de la couche ; et
• la meule comporte des ajours.

The grinding wheel according to the invention can also have one or more of the following characteristics:

• in the layer of abrasive grains which has a region extending near the center and a region extending along the periphery of the layer, made up of different abrasive grains, these two regions are juxtaposed;
• in the layer of abrasive grains which has juxtaposed regions made up of different abrasive grains, at least two of these regions are juxtaposed along a joint line which has a circular shape;
• in the layer of abrasive grains which has juxtaposed regions made up of different abrasive grains, at least two of these regions are juxtaposed along a closed joint line which has a non-circular shape;
• the grinding wheel has at least two layers of abrasive grains, at least one of which has juxtaposed regions made up of different abrasive grains, one of these regions extending in the vicinity of the center of the layer while another of these regions extends along the periphery of the layer; and
• the wheel has cutouts.

The invention also relates to a method for manufacturing a abrasive wheel as defined above, characterized in that, for manufacture at least one layer of abrasive grains, on the one hand, a wafer possibly having a central hole, and consisting of grains abrasives of a first type, and on the other hand at least one crown made up abrasive grains of a second type, the inner contour of the crown and the outer contour of the wafer being geometrically similar, then to make the grinding wheel, we put the crown and the wafer in relation optional insertion on a reinforcement layer possibly another layer of reinforcement on the wafer and the crown in insertion relationship, and in a later stage of the manufacturing process presses the stack of constituent layers.

Thanks to this process, it is possible to make a grinding wheel comprising at least one layer of abrasive grains which has regions made up of different abrasive grains arranged concentrically, without imbalance likely to cause destruction of the grinding wheel recommended working speeds, and this with a large margin of safety.

• avant de la presser, on chauffe la pile de couches de constituants ;
• on dispose une galette comportant un trou central sur une couche de renfort en enfilant son trou central autour d'une bague autour de laquelle est déjà enfilée la couche de renfort, puis on dispose la couronne autour de la galette afin que la couronne et la galette soient en relation d'insertion sur la couche de renfort ;
• on superpose successivement, au moins, une couche de renfort, une couche de grains abrasifs, une couche de renfort, une couche de grains abrasifs, et une couche de renfort, et pour fabriquer au moins l'une des couches de grains abrasifs, on fabrique d'une part une galette et d'autre part au moins une couronne présentant respectivement un contour extérieur et un contour intérieur géométriquement semblables, que l'on met en relation d'insertion.

The method can also have one or more of the following characteristics:

• before pressing it, the stack of layers of constituents is heated;
• we have a wafer having a central hole on a reinforcement layer by threading its central hole around a ring around which the reinforcement layer is already threaded, then we have the crown around the wafer so that the crown and the wafer are in insertion relation on the reinforcement layer;
• at least one reinforcing layer, a layer of abrasive grains, a reinforcing layer, a layer of abrasive grains, and a reinforcing layer are successively superimposed, and to manufacture at least one of the layers of abrasive grains, manufactures on the one hand a wafer and on the other hand at least one crown respectively having an outer contour and an inner contour geometrically similar, which is put in insertion relation.

une machine de fabrication de galettes comportant éventuellement un trou central à partir de grains abrasifs d'un premier type,

une machine de fabrication de couronnes à partir de grains abrasifs d'un deuxième type, le contour intérieur de la couronne et le contour extérieur de la galette étant géométriquement semblables,

une ligne d'assemblage comprenant un poste de mise en relation d'insertion des couronnes et des galettes

et une machine de pressage.

The subject of the invention is also an installation for manufacturing an abrasive wheel, characterized in that it comprises:

a wafer manufacturing machine optionally comprising a central hole from abrasive grains of a first type,

a machine for manufacturing crowns from abrasive grains of a second type, the internal contour of the crown and the external contour of the wafer being geometrically similar,

an assembly line including a connection point for inserting crowns and pancakes

and a pressing machine.

• la figure 1 est une section transversale schématique d'une première forme de réalisation d'une meule selon l'invention,
• la figure 2 est une section transversale schématique d'une variante de la meule de la figure 1,
• les figures 3 et 4 sont des schémas montrant en section transversale respectivement deux phases de fabrication dans un moule, d'un composant de la meule de la figure 1,
• les figures 5 et 6 sont des schémas montrant en section transversale respectivement deux phases de fabrication dans un moule, d'un autre composant de la meule de la figure 1, et
• la figure 7 est une vue schématique de dessus, d'une ligne d'assemblage à laquelle est associée une machine de pressage, pour mettre en oeuvre le procédé de fabrication de meules abrasives selon l'invention.

Other characteristics and advantages of the invention will emerge from the description which follows, of embodiments of the invention and of manufacturing methods for these embodiments given by way of nonlimiting examples and illustrated by the accompanying drawings. wherein :

• FIG. 1 is a schematic cross section of a first embodiment of a grinding wheel according to the invention,
• FIG. 2 is a schematic cross section of a variant of the grinding wheel of FIG. 1,
• FIGS. 3 and 4 are diagrams showing in cross section respectively two phases of manufacturing in a mold, of a component of the grinding wheel of FIG. 1,
• FIGS. 5 and 6 are diagrams showing in cross section respectively two phases of manufacturing in a mold, of another component of the grinding wheel of FIG. 1, and
• Figure 7 is a schematic top view of an assembly line with which is associated a pressing machine, to implement the method of manufacturing abrasive wheels according to the invention.

The grinding wheel according to the invention shown in Figure 1, of the type thin grinding wheel, comprises, threaded around a central metal ring 11, layers of stacked constituents, and more precisely a disc of protection 12 generally consisting of a sheet of paper or the like, said "Paper", a reinforcing layer 13 called "fabric" and which can actually be fabric, or preferably a mesh, perforated or honeycomb material, a layer of abrasive grains 14, another reinforcing layer 15 generally identical to the first, and possibly another protective disc says "Paper".

The manufacture of such a grinding wheel comprising a phase of pressing, the layer of abrasive grains 14 and the reinforcing layers 13, 15 mesh, perforated or dimpled are generally at least partially nested as a result of the penetration of the abrasive grains constituting the layer 14, in the stitches, perforations or cells.

In addition, the abrasive grain layer 14 has regions juxtaposed, here two concentric regions 14A, 14B, formed from abrasive grains of different characteristics, one of these regions extending in the vicinity of the central ring 11 while the other region surrounds the first and extends along the outer periphery of the layer of abrasive grains.

The joint line between regions 14A, 14B made up of abrasives different is a closed line that extends here in circumference centered on the axis of the central ring 11.

The grinding wheel shown in Figure 2 being identical to that of the figure 1 except that the part of the grinding wheel which is in the vicinity of the central ring 11 does not extend in the same plane as the part which surrounds it, the description of Figure 1 also applies to Figure 2, and the components of the grinding wheel of figure 2 have the same numbers of reference as the corresponding components of Figure 1; here the region 14A adjacent to the central ring has an offset profile, and the region 14B surrounding it is flat, but alternatively region 14A could be more small and flat surface, and region 14B could then have a profile deported.

The grinding wheel according to the invention can also comprise several layers made from abrasive grains such as the grain layer abrasives 14, stacked successively, each time with the insertion of a reinforcing layer called "fabric" between two layers of abrasive grains.

• à disposer dans un moule placé sur un plateau de fabrication, la bague centrale 11 autour de laquelle on dépose successivement le disque de protection 12, la feuille de renfort 13, et les produits pulvérulents différents formés de grains abrasifs de types différents comportant un enrobage constitué par un liant, répartis dans le moule en fonction de la géométrie que l'on désire donner aux deux régions constituées d'abrasifs différents,
• à racler la couche de produits pulvérulents 14 afin de réduire son épaisseur à la valeur voulue,
• à superposer une deuxième couche de renfort 15 à la couche de produits pulvérulents,
• éventuellement à déposer une couche de produits pulvérulents et superposer une couche de renfort autant de fois que le nécessite le type de meule à fabriquer, et superposer une deuxième feuille de protection,
• et à comprimer dans une presse la pile obtenue.

It is conceivable to manufacture the grinding wheels according to the invention by the conventional method consisting

• to be placed in a mold placed on a production plate, the central ring 11 around which is successively deposited the protective disc 12, the reinforcing sheet 13, and the different pulverulent products formed from abrasive grains of different types comprising a coating formed by a binder, distributed in the mold according to the geometry which it is desired to give to the two regions made up of different abrasives,
• scraping the layer of powdered products 14 in order to reduce its thickness to the desired value,
• superimposing a second reinforcing layer 15 on the layer of pulverulent products,
• optionally depositing a layer of powdered products and superimposing a reinforcing layer as many times as required by the type of grinding wheel to be manufactured, and superimposing a second protective sheet,
• and compressing the stack obtained in a press.

However, in addition to the fact that the known installations allowing the implementation of this process, generally, are bulky and expensive, operate at a relatively slow rate, are subject to frequent breakdowns due to the inevitable presence of abrasive grains in the whole machine, and are not very scalable, the process may not allow to perfectly control the distribution of abrasive products and thus lead to the manufacture of grinding wheels with an imbalance unacceptable.

This is why, advantageously, we manufacture the grinding wheels according to the invention by replacing the removal of the pulverulent products formed from abrasive grains comprising a coating, by depositing a cake abrasive itself manufactured as will be seen hereinafter from such abrasive grains and, for the abrasive layer (s) with two regions concentric, by removing an abrasive pad and crown manufactured in the same way as we put an insertion relation, in eliminating the scraping phase, and continuing the process by superimposing a reinforcing layer on the wafer and the crown in relation insertion.

In the case of a grinding wheel with several layers of abrasive grains, one, several, or all of these layers can be made of this way.

The abrasive pad and ring can be made using a method and a machine such as those described in detail in patent document FR 99 07 282 of the applicant, which allow to make wafers and crowns without the inconvenience mentioned above and in particular remarkably well balanced.

In short, the wafer making machine has a table of rotary manufacturing step by step of generally circular shape comprising by example four sectors equipped with molds, and fixed work stations specialized to perform the different tasks respectively or manufacturing operations on the contents of the molds when they pass in front of them; thus, several patties can be simultaneously in manufacturing course on the table. The machine also has a table rotary storage on which the patties made on the table manufacturing are aligned or / and stacked before being removed to be transferred to an assembly line.

The stations that equip the machine are a dumping station abrasive product consisting of abrasive grains comprising a coating consisting of a binder, a scraping equalization station, a pressing, a wafer unloading station, and a cleaning station of the table.

The molds (Figures 3 and 4), of generally cylindrical shape, have a side wall 16 inside which is mounted a bottom sliding 17 suitable for sliding in vertical direction, provided with a core central 18

The abrasive dumping station is provided at its upper part an abrasive product tank; at its bottom, the post of spill has a closable slot so the product can be poured into the mold when it is positioned under the slot, the bottom of the mold being positioned inside the side wall at a depth greater than the desired thickness for the cake.

The abrasive product being spilled slightly in excess, a scraper equalization 19 scrapes the product flush with the side wall 16 of the mold.

The pressing station compresses the product by force of the order of a few tonnes (or tens of thousands of newtons), forming then the cake intended to be introduced into an assembly line which will be described below.

The unloading station transfers the pancakes from the table manufacturing at the storage table.

The cleaning station cleans the table area which passes opposite, downstream of the unloading station.

So in the present case where each of the four sectors of the table is equipped with a single mold, we have almost or simultaneously a mold being filled, a mold being scraped, a pancake being pressing, and a cake being unloaded from the table manufacturing.

The crown making machine can be the same as the wafer making machine, in the shape and dimensions of the molds close (Figures 5 and 6); thus, the molds, of generally cylindrical shape, have a side wall 16 'inside which is mounted a bottom sliding 17 'suitable for sliding in vertical direction, provided with a core central 18 '. An equalizing scraper 19 'scrapes the excess abrasive product flush with the side wall 16 'of the mold. The description of the machine manufacturing and its operation will therefore not be repeated.

Thanks to the fact that we make wafers and crowns ready to be introduced into an assembly line, it is easier to make grinding stones of different dimensions and also to move from "monolayer" grinding stones to "multilayer" grinding stones.

Indeed, the tools of the stations being not very complex, can in the event of a change in manufacture or a breakdown, be exchanged very quickly; in addition, advantageously, the dimensions of the grinding wheels can be chosen so that a wafer of given dimensions can enter into the manufacture of a wheel with a single type of abrasive grains of relatively small diameter, and serve as a central cake in a grinding wheel larger diameter to two types of abrasive grains; for example, a 75 mm wafer can be used to form the central region of a 125 mm grinding wheel with two types of abrasive grains.

In addition, the rotary table is relatively small (the diameter can be reduced to a value less than one meter), and the molds which are used only for the production of wafers and crowns, are light weight (less than 15 kg).

The pressing force to be exerted on the abrasive product to making the patties and the crowns one by one is relatively moderate, of the order of a few tonnes (or tens of thousands of newtons), during about a second.

As a result, it is easy to reach with a table rotary with four molds, a rate of 1000 pancakes or 1000 crowns per hour.

In addition, as the abrasive product does not exist in the line assembly only in the form of wafers and crowns and no longer in powder form, the wear of the assembly line in which the Constituent layers are stacked is significantly reduced.

The assembly line illustrated by the diagram in Figure 7 is intended for the manufacture of grinding wheels with a single layer of abrasive grains, therefore comprising here a cake and a crown.

It comprises a conveyor 20 progressing in a closed circuit, the along which are specialized fixed work stations for perform respectively the different operations of manufacturing the grinding wheel proper. This conveyor carries trays fixed on it, suitable for receive removable trays 201 on which, as and when scrolling of the conveyor, the different elements are stacked one on the other and in particular the different layers of constituents of the grinding wheels.

More specifically, the assembly line comprises in succession in the direction of travel of the conveyor 20, a ring fitting station central 21, a basic "paper" installation station 22, a basic installation station lower reinforcement layer 23, a wafer laying station 24, a laying of crown 25, a station for laying an upper reinforcing layer 26, possibly a top “paper” installation station (not shown), here a heating station 27, and an unloading and recharging station 28.

Each work station intended to superimpose a layer of constituent has a stock of batteries each carried by a tray removable 201, and thus a short-term interruption of the operation of one of the stations, for example due to a breakdown, does not completely interrupt the manufacture of grinding wheels, the workstations located downstream working on their stock, and upstream stations that can be ordered to increase the their Here we therefore advantageously obtain a desynchronization of manufacturing operations

The heating station 27 provided here heats the batteries P which run at a temperature of about 50 to 80 ° C which facilitates a slight flow of the abrasive product constituting the wafers in the holes of the reinforcement layer, for example mesh in the case of real fabric or similar.

As each station performs a single operation of overlapping, the assembly line has a certain modularity and increasing the number of layers can be done by simply adding the appropriate number of positions; for example, to make grinding wheels two layers of abrasive grains, just add to the assembly line which has just been described, a wafer installation station, a crown, and a reinforcement layer installation station.

In the event that the reinforcing layers or "fabrics" are delivered coated with the “paper” layer, the two immediately successive items respectively of laying of "paper" and laying of "fabric" (or conversely) are replaced by a single item.

It should be noted that the laying stations can be automated or manuals.

Following the assembly line, the installation includes a pressing machine 29 in which the removable plates with their contents, leaving the heating station 27, are transferred by the unloading and reloading 28; alternatively, this machine pressing could be part of the assembly line.

The pressing machine 29 is similar to that of the applicant's patent document FR 99 07 282. As the abrasive products are already in the form of wafers and crowns, the duration of the pressing step is relatively short, and since each press works only on a stack, the pressing force can remain relatively moderate (of the order 20 tonnes, i.e. approximately 2.10 ⁵ N).

The discs discharged from the pressing machine 29 are then, in known manner, transferred to another oven to undergo a annealed before being stored for delivery.

Of course, the invention is not limited to the above examples described and represented, and others can be provided without departing from its frame, for example making grinding wheels with two types of abrasive grains (or more) one or more juxtaposed regions have openings for example made during molding.

Claims (18)

1. Abrasive wheel of the thin wheel type, comprising several layers (12, 13, 14, 15) of stacked constituents, comprising at least one layer of abrasive grains (14) which comprises juxtaposed regions (14A, 14B) consisting of different abrasive grains, one of these regions extending close to the centre of the layer (14) whilst another of these regions extending along the external periphery of the layer, characterised in that the said regions (14A, 14B) are formed respectively by a pad and an annulus put in insertion relationship.
2. Abrasive wheel according to Claim 1, characterised in that, in the layer of abrasive grains (14) which comprises a region (14A) extending close to the centre and a region (14B) extending along the periphery of the layer, consisting of different abrasive grains, these two regions are juxtaposed.
3. Abrasive wheel according to either one of Claims 1 and 2, characterised in that, in the layer of abrasive grains (14) which comprises juxtaposed regions (14A, 14B) consisting of different abrasive grains, at least two of these regions are juxtaposed along a joint line which has a circular shape.
4. Abrasive wheel according to either one of Claims 1 and 2, characterised in that, in the layer of abrasive grains (14) which comprises juxtaposed regions (14A, 14B) consisting of different abrasive grains, at least two of these regions are juxtaposed along a closed joint line which has a non-circular shape.
5. Abrasive wheel according to any one of Claims 1 to 4, characterised in that it comprises at least two layers of abrasive grains, at least one (14) of which comprises juxtaposed regions (14A, 14B) consisting of different abrasive grains, one of these regions extending close to the centre of the layer (14) whilst the other of these regions extends along the periphery of the layer.
6. Abrasive wheel according to any one of Claims 1 to 5, characterised in that it comprises openings.
7. Method of manufacturing an abrasive wheel according to any one of Claims 1 to 6, characterised in that, in order to manufacture at least one layer of abrasive grains, firstly a pad is manufactured comprising possibly a central hole, and consisting of abrasive grains of a first type, and secondly at least one annulus consisting of abrasive grains of a second type, the internal contour of the annulus and the external contour of the pad being geometrically similar, and then, in order to manufacture the wheel, the annulus and pad are put in insertion relationship possibly on a reinforcing layer (13), another reinforcing layer (15) is possibly superimposed on the pad and annulus in insertion relationship, and, in a subsequent step of the manufacturing method, the stack of layers of constituents is pressed.
8. Method of manufacturing an abrasive wheel according to Claim 7, characterised in that, before pressing it, the stack of layers of constituents is heated.
9. Method of manufacturing an abrasive wheel according to either one of Claims 7 and 8, characterised in that a pad comprising a central hole is disposed on a reinforcing layer (13) by slipping its central hole around a ring (11) around which there is already slipped the reinforcing layer, and then the annulus is disposed around the pad so that the annulus and pad are in insertion relationship on the reinforcing layer.
10. Method of manufacturing an abrasive wheel according to any one of Claims 7 to 9, characterised in that there are successively superimposed at least a reinforcing layer (13), a layer of abrasive grains, a reinforcing layer, a layer of abrasive grains, and a reinforcing layer, and, in order to manufacture at least one of the layers of abrasive grains (14), there are manufactured firstly a pad and secondly at least one annulus having respectively an external contour and an internal contour which are geometrically similar, which are put in insertion relationship.
11. Installation for manufacturing an abrasive wheel according to any one of Claims 1 to 6, characterised in that it comprises
    a machine for manufacturing pads comprising possibly a central hole from abrasive grains of a first type,
    a machine for manufacturing annuluses from abrasive grains of a second type, the internal contour of the annulus and the external contour of the pad being geometrically similar,
    an assembly line (20) comprising a station (25) for putting annuluses and pads in insertion relationship
    and a pressing machine (29).
12. Installation according to Claim 11, characterised in that the pad manufacturing machine and/or the annulus manufacturing machine comprise a stepping rotary manufacturing table comprising a station for pouring abrasive product, a station for equalisation by raking, a pressing station, a pad discharge station and a table cleaning station.
13. Installation according to Claim 12, characterised in that the pad manufacturing machine and/or the annulus manufacturing machine also comprise a station for storing pads and/or annuluses before being transferred to the assembly line.
14. Installation according to Claim 13, characterised in that the annulus manufacturing machine comprises at least one mould comprising a lateral wall (16') inside which there is mounted a sliding bottom (17') adapted to slide in the vertical direction, provided with a central core (18').
15. Installation according to any one of Claims 11 to 14, characterised in that the assembly line comprises a station for laying a reinforcing layer (23) upstream of the station (25) putting in insertion relationship.
16. Installation according to any one of Claims 11 to 15, characterised in that it comprises a machine for manufacturing pads comprising a central hole and in that the assembly line (20) comprises a station (21) for placing a central ring upstream of the station (23) for laying a reinforcing layer.
17. Installation according to any one of Claims 11 to 16, characterised in that the assembly line comprises a heating station (27) before the pressing station (29).
18. Installation according to any one of Claims 11 to 17, characterised in that the assembly line comprises at least one station where there are successively superimposed at least one reinforcing layer (13), a layer of abrasive grains, a reinforcing layer, a layer of abrasive grains, and a reinforcing layer.

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