US 20060280908 A1
The present invention relates to a flexible grinding product and a method of producing the same. Such a grinding product comprises a flexible underlay (1) which consists of two layers laminated to each other. These comprise a lower base layer (2) and an upper layer (3), a cavity layer. The underlay includes a top surface (5) having at least one adhesive layer (6) arranged thereto after lamination and a layer of grinding agent (7) applied by means of the adhesive layer. The grinding product is characterized in that the layer that is coated with grinding agent includes holes which form cavities (4), whereby the cavities provide space for grinding dust and grinding residues and facilitate their re-moval from the surface being ground.
1. A flexible grinding product comprising a flexible underlay, at least one adhesive layer on one side of the underlay and a layer of grinding agent applied by means of the adhesive layer,
the underlay consisting of two layers which are laminated to each other and comprising a lower base layer and an upper layer, which is provided with a top surface,
the top surface comprising grinding agent applied thereto after lamination, whereby
the top surface is provided with holes which form cavities in the top surface so that
the cavities provide space for grinding dust and grinding residues and facilitate their removal from the surface being ground.
2. A flexible grinding product according to
3. A flexible grinding product according to
4. A flexible grinding product according to
5. A grinding product according to
6. A flexible grinding product according to
7. A grinding product according to
8. A grinding product according to
9. A flexible grinding product according to
10. A flexible grinding product according to
11. A flexible grinding product according to
12. A flexible grinding product according to
13. A flexible grinding product according to
14. A flexible grinding product according to
15. A method of producing a flexible grinding product, which comprises a flexible underlay, at least one adhesive layer applied on one side of the underlay and a layer of grinding agent applied by means of the adhesive layer,
the lower base layer and the porous upper layer being laminated to each other to form an underlay, after which
a top surface of the upper layer is coated with grinding agent, whereby
cavities are formed in the top surface to provide space for grinding dust and grinding residues and to facilitate their removal from the surface being ground.
16. A method according to
17. A method according to
18. A method according to
19. A method according to
20. A method according to 15, wherein the base layer of the underlay is perforated before it is laminated to the upper layer.
21. A method according to
22. A method according to
The invention relates to a flexible grinding product according to the preamble of independent claim 1. The invention further relates to a method of producing a similar grinding product according to the preamble of independent claim 15.
Grinding product of this kind includes special recesses for removal of grinding dust from the grinding surface and for cooling the grinding surface.
Production of discoid grinding products consisting of a flexible underlay, such as paper, is well known. One side of the underlay is provided at least with one adhesive layer, which includes an essentially continuous layer of grinding agent substantially applied thereto.
To enable continuous maintenance of the grinding product's grinding effect, as much of the grinding dust released during grinding as possible must be removed from the space between the grinding product and the grinding surface of the object being ground. As the underlay of such grinding products has not conventionally been air and dust permeable, the grinding products have usually been provided with specific perforated openings, which extend through the grinding product and are connected to air ducts, for example, through which grinding dust can be sucked out while grinding continues. Such products are described in EP 0 781 629, for instance.
These prior art grinding products are produced so that an otherwise finished grinding product is fed through an apparatus where the grinding product is provided with holes by perforation or another piercing process. However, this way of providing the grinding product with through-holes has several disadvantages. Perforation causes cracks and other undesired deformations at the edges of the holes, both in the underlay and in its adhesive layer. Due to crack formation and deformations, the material bridges between the holes must be made relatively wide because narrow material bridges can easily break. Consequently, the holes must be placed at a relatively long distance from one another, as a result of which the grinding product is not cleaned efficiently enough and its grinding effect decreases relatively fast during grinding.
Such perforation also causes other disadvantages. Perforation of the underlay weakens the grinding product to such an extent that a continuous grinding belt cannot be formed of it. The reason for this is that perforation causes increased stretching in the underlay when it is subjected to stress. In addition, an edge perpendicular to the main plane of the grinding product is often formed at the hole edges of the underlay in the perforation process. This edge makes the removal of grinding dust through the holes of the grinding product more difficult. It is further generally known that the perforator wears fast during perforation because of the hard grinding agent.
Most of the above-mentioned disadvantages can naturally be avoided by coating the underlay of the grinding product after it has been perforated, impregnated and coated with a sufficient number of adhesive layers as described in U.S. Pat. No. 2,838,890. The problem associated with this solution is that this grinding product cannot be used in producing a continuous grinding belt, or grinding belts made of perforated grinding products can only be produced from grinding products having a relatively thick underlay. The underlay must be thick so as avoid stretching of the grinding belt. However, the impregnation and coating of the underlay in accordance with the above-mentioned US publication makes the underlay brittle, which means that the grinding product can be bent only a little without breaking it. A grinding belt made of this grinding product would thus break easily in use. If the grinding belt is sufficiently elastic so that is does not break, there is the risk that the grinding belt is stretched too much by belt tension.
Net-like grinding products with a cloth base provided with through-holes for dust removal have also been devised. Such a solution is described in WO 96/13358, for example. The problem associated with this solution is that the cloth requires a special production technique and its use is thus expensive. Also the processing and coating of the cloth require special methods. Furthermore, the finished product has the disadvantage that the cut and perforated edges are weakened by the holes that are on the cutting line since they form notches in the edge of the finished product.
Finally, it may be mentioned that the problem arising in connection with the above-mentioned perforation of grinding products has been relieved by using as the underlay an open cloth or a net where most of the surface is air-permeable. Grinding products produced this way have, however, a poorer grinding capacity than the grinding products described earlier because a continuous and substantially even layer of grinding agent cannot be applied to a cloth or a net. The grinding agent layer will not be in a uniform main plane but will follow the uneven surface of the cloth or net in different planes. As the amount of grinding agent acting on the surface of the work piece is smaller per unit area compared to a case where the whole surface is coated with grinding agent, the grinding effect will decrease. Such a grinding product is described in Fl 96584, for example.
The problems involved in prior art solutions can be substantially avoided by the present invention. The object of the invention is thus to provide a flexible grinding product which is easy to handle, has a high strength and a sufficient dust removal capacity.
This object is achieved by the flexible grinding product and its production method characterized by what is stated in independent claims 1 and 15. Respective dependent claims describe suitable further embodiments and variants of the invention that improve its operation.
The present description and the appended claims use the terms “pore” and “porosity” to refer to a channel structure that substantially goes through a material. This channel structure may be formed artificially or it may be a natural characteristic of the material.
The term “grinding surface” means the surface of a work piece at which the effect of the grinding product is directed.
The grinding product and the method of producing the same according to the invention provide several significant advantages over the prior art. It is thus not necessary to make perforations to an underlay already coated with grinding agent since the adhesive layer is applied to an underlay whose upper surface has already been provided with holes obtained by laminating a cavity layer to a base layer. This naturally simplifies the production of the grinding product as well as reduces the costs. The hole structure on the top surface of the underlay can also be achieved in a simple manner so that no cracks or edge is formed in the coating at the edges of the hole. As no cracks are formed, the holes on the upper surface can be arranged very close to one another and thus the material bridges between the holes can be narrow. This makes both the removal of grinding dust and cooling of the grinding surface more effective.
A further substantial advantage provided by the invention is that the adhesive layer will extend as a substantially continuous layer from the top surface of the underlay to its hole structure and to the edge surfaces provided therein.
Since the adhesive layer extends over the edge surface of the hole structure, the transitional area between the underlay's top surface and edge surface is uniform and smooth without any cracks or edges, which facilitates collection of grinding dust particles from the space between the top surface of the grinding product and the work piece to the grinding product.
The adhesive layer will also strengthen the edge surfaces of the underlay as well as the bottom sections of the recesses which are formed from the hole structure since the adhesive layer, if desired, may also impregnate these surfaces. The adhesive layer can thus cover part of the edge surface or even the whole surface of the recesses.
The grinding product can also be made very flexible by laminating two substantially unstretchable thin materials to each other. This way the grinding product can be used in producing continuous grinding belts, for instance.
The dust transportation properties of the grinding product are better than those of competing products since the hole structure in the top surface of the underlay forms a temporary storage place or reservoir for dust and grinding residues during grinding. This way dust and grinding residues may be stored in holes and recesses while the grinding product is against the grinding surface. As soon as air flow can be generated at the grinding product, the collected dust or grinding residues can be transported further.
The dust transportation properties can be improved further by forming the base layer of a porous material. Such material can be preferably used in the production of grinding products for oscillating grinding machines, for example, where the requirements for stretch resistance are not as high as in the case of a grinding belt.
When the material of the base layer includes a fastening element or the lower side of the base layer is provided with fastening loops known per se, the grinding product can be easily applied to known grinding machines.
Further advantages and details of the invention will appear from the description below.
In the following, the invention will be described in greater detail with reference to the drawings, in which
In the following, a preferred embodiment of a flexible grinding product is described with reference to the above-mentioned figures. The solution comprises the components shown in the figures, each of the components being provided with a respective reference number. These reference numbers correspond to the ones used in the description below.
The flexible grinding product shown in the figures comprises an underlay 1, which consists of paper, woven cloth or film made of suitable polymer, for instance. As shown in the figures, the underlay comprises two layers laminated to each other, i.e. a lower base layer 2 and an upper porous layer provided with grinding agent, which will be referred to as a cavity layer 3 in the following. This cavity layer may be naturally porous and dust permeable in accordance with
If the porosity of the naturally porous material is sufficient as in the case of a woven net-shaped cloth, for example, no separate perforation is needed to obtain the intended hole structure; otherwise even this material can be perforated in advance.
When the cavity layer 3 is laminated to the base layer 2, recesses 4 or cavities are formed in accordance with the embodiment shown in FIGS. 1 to 4. The cavities go through one surface of the underlay 1, which will be referred to as the top surface 5 in the following. The number, shape, size and distribution of the recesses may vary according to the need depending on the grinding product. Recesses may be distributed over the cavity layer evenly or randomly. When the cavity layer is perforated, the recesses can even be distributed according to different patterns that recur on the top surface. The distribution and shapes of the perforations are illustrated in FIGS. 7 to 11.
The top surface 5 of the underlay 1 shows, in accordance with FIGS. 2 or 4, an adhesive layer 6. Both in and on this adhesive layer, there is a layer of grinding agent 7, in which case the adhesive and grinding agent layers form a substantially continuous layer on the top surface. The surface of the underlay opposite to the top surface, i.e. its lower surface 8, forms a substantially flat and strong layer suitable for a grinding belt. Here it should also be noted that the thickness of the underlay, adhesive layer and grinding agent layer have been exaggerated in the figures for the sake of clarity.
It is also feasible to arrange a separate fastening layer on the upper surface 8 of the underlay 1. This can be formed of a knitted cloth, for example. This cloth preferably has fastening loops 10 on its surface extending from the lower surface, as shown in
The embodiment of the grinding product shown in FIGS. 1 to 4 comprises recesses 4 which are arranged alongside each other and extend through the grinding agent and adhesive layers 7 and 6 and partially into the underlay 1. Thus the recesses form a storage place or reservoirs in the top surface of the grinding product, which function as collectors in removal of grinding dust and residues from the grinding surface. In the embodiments according to
In a second embodiment according to
In a third embodiment, the laminated underlay 1 comprises a base layer 2 of a material perforated in advance. This perforation can be arranged to substantially overlap with the perforation of the cavity layer, as shown in
When the grinding products according to the embodiments are to be used in mechanical grinding, they are provided with fastening loops 10 or a similar fastening layer 9 in the manner described above. If the base layer 2 includes a woven, non-woven or knitted cloth or similar material, the lower surface 8 of the underlay can be provided with suitable fastening loops in accordance with
In grinding with a grinding product according to
In grinding with a grinding product according to
In all the embodiments described above, the removal of grinding dust is facilitated as the holes at the edges of the underlay are free from cracks and other irregularities. Thanks to the uniform and continuous grinding agent layer, the material bridges 14 between the holes on the top surface of the underlay can be made narrow. This further facilitates the removal of grinding dust from the area of the material bridges towards the hole structures leading to the holes.
In connection with the production of a discoid flexible grinding product according to
The discoid flexible grinding product according to
In the production of the discoid flexible grinding product according to
Here a continuous layer of grinding agent 7 means that the layer of grinding agent comprises a continuous surface through which a hole structure has been pierced. This is contrary to some prior art grinding products where the adhesive and grinding agent layers are not continuous but form separate clusters. Thus the term “continuous” does not require that the grinding agent particles should be closely side by side. They are, however, fastened adjacent to each other by the adhesive layer 6. It can also be seen in the figures that the grinding agent particles are substantially in one plane.
The grinding product needs not be provided with a cloth having fastening loops or another fastening layer 9. An embodiment without a fastening layer is particularly suitable when the grinding product is formed as a continuous belt for use in a conventional belt grinding machine, which may be provided with a blow-through unit or a suction unit for continuous cleaning of the belt.
The number of adhesive layers on the top surface of the underlay may be even larger than two. For example, a layer known as a supercoat layer can be applied to the top surface to achieve dust rejection, cooling or lubrication.
In the figures, the edge surfaces 11 have been drawn so that they are substantially perpendicular to the main plane of the grinding product, i.e. the top surface 5 and the lower surface 8. However, the whole edge surface or part of it may also form an angle with the main plane of the grinding product. What is essential is that the edge surface can be considered to define a recess in the underlay.
The description and the appended figures are only intended to illustrate the present solution for designing a flexible grinding product. The solution is thus not limited to the embodiments described above or in the enclosed claims but it may be varied or modified within the inventive concept described in the enclosed claims.