Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D13/00—Wheels having flexibly-acting working parts, e.g. buffing wheels; Mountings therefor
  • B24D13/14—Wheels having flexibly-acting working parts, e.g. buffing wheels; Mountings therefor acting by the front face
  • B24D13/16—Wheels having flexibly-acting working parts, e.g. buffing wheels; Mountings therefor acting by the front face comprising pleated flaps or strips
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D18/00—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for
  • B24D18/0045—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for by stacking sheets of abrasive material

Definitions

• the present invention relates to an abrasive tool of the disposable type applicable to equipment, both professional, industrial and for hobbies, to sand materials of various types having rough surfaces.
• the invention relates to a device using rotating abrasive discs.
• the abrasive surfaces used for sanding are of different types, both natural and synthetic.
• diamond, corundum, silica, quartz, pumice, sandstone or various synthetic oxides such as aluminium, chrome, iron, glass oxides and so forth are used.
• the chosen material is ground so as to obtain a predefined grain size which also depends on the type of sanding desired, it is then combined with a binding agent to make it adhere to a backing or modelled, with or without the binding agent, to form the tool, to mention just some of the more conventional methods.
• the sanding of an untreated surface is usually conducted in a series of stages. Levelling and roughing are usually the first steps, , followed by finishing and polishing after filling in any cracks or pores.
• an abrasive surface having a different grain is used, that is to say in which abrasive powder material has a specific grain size: the biggest grain is used to roughly sand the surface, in that it permits removal of the excess material more easily but is unable to provide a surface finish; the finer grain instead makes it possible to achieve a good finish as far as sanding the surface but cannot be used for the first rough sanding step.
• abrasive tool used in particular for manual sanders is that of the so-called abrasive flap or lamellar discs.
• An abrasive disc of this type shown by way of example in figure 1, is composed of a disc-shaped backing in essentially rigid material such as plastic or aluminium, onto which a plurality of abrasive fins of the desired grain are glued.
• the fins are arranged so as to partially overlap each other like roof tiles, which allows them to expose a sharp edge contributing greatly to the sanding action, this being the point in which the greater pressure is exerted by the operator during use.
• Lamellar flap discs have various advantages compared to traditional abrasive discs composed of a single disc of abrasive material, such . as longer duration and high quality performance, but have the drawback of being expensive, having a rigid structure and entailing an excessive waste of material at the moment of their disposal, especially of the rigid support to which the lamellar flaps are glued.
• the purpose of the present invention is therefore to make available an abrasive tool for sanding machines which resolves the drawbacks of the prior art and in particular which is flexible, lasting, of limited cost and which permits high quality performance.
• One object of the invention is therefore a flexible abrasive tool of the lamellar-like type re-adaptable according to the wear of the abrasive surface.
• Another object of the invention is a constructionally simple abrasive tool of the lamellar-like type of a contained cost.
• One further object of the invention is therefore a flexible abrasive tool of the lamellar-like type having a variable grain abrasive work surface.
• Figure 1 is a plan view of an abrasive lamellar flap disc according to the prior art
• Figure 2 is a perspective transparent view of an abrasive tool according to the invention.
• Figure 3 is a plan view of an abrasive disc of the tool according to the invention.
• Figure 4 is a plan view of the abrasive disc in figure 3 according to a different embodiment of the invention.
• Figure 5 is an exploded side view of the abrasive tool of the invention fitted onto a manual sander
• Figures 6A and 6B show the sequence of operations needed to predispose the abrasive tool according to the invention
• Figure 7 is a perspective transparent view of an abrasive tool according to a different embodiment of the invention .
• the abrasive tool which the invention relates to comprises a plurality of flexible abrasive discs 2, open at a radial cut 3 and arranged in an overlapping and staggered configuration such as to define an abrasive, lamellar-like work surface 4 with overlapping flaps, wherein each flap 5 is formed of a protruding portion of an abrasive disc 2.
• abrasive disc is understood to mean both a correctly named disc of a circular shape and any other disc, even of a polygonal shape, suitable for use in sanding machines with rotating elements.
• lamellar-like means a configuration in which a plurality of flaps 5 are positioned so as to create a partially overlapping lamellar structure, typical of the abrasive lamellar discs shown by way of example in figure 1.
• each abrasive disc 2 of the plurality of discs comprises a central hole 7 from which a plurality of slots arranged in a spoke pattern depart, so as to form flaps 9 positioned around the hole 7.
• the abrasive disc 2 further comprises said radial cut 3 which extends from the peripheral rim 6 of the disc to the central hole 7.
• the abrasive disc 2 is flexible.
• An abrasive disc suitable for the purposes of the present invention is any one of the conventional flexible abrasive discs.
• the flexible abrasive discs are characterised by a backing to which a suitable abrasive powder adheres by means of a binding agent.
• a disc having a paper backing typically weighing from 70 to 300 g/m 2 or a canvas or canvas/paper backing may be used.
• the backing may be made from semi-rigid plastic material or even a thin and flexible sheet of metal, such as aluminium.
• the backing comprises the male or female element of a velcro fastening system on the opposite side to the abrasive side, so as to permit its removable attachment to the polishing pad of a sander which will in turn comprise the complementary velcro element.
• the abrasive powder may be selected from among those commonly used in the sector depending on the type of surface to be sanded and the desired finish.
• a natural abrasive powder of diamond, corundum, quartz silica, pumice, sandstone, emery, garnet or a synthetic powder of aluminium, chrome, iron, zirconium oxides, boron nitride, silicon carbide, glass, boron carbide, ceramic-coated aluminium oxide may be used.
• the grain may be chosen from among those commonly used for the varying degrees of finish required, for example for artificial corundum and for silicon carbide this may be between 8 and 240 degrees, as defined in the UNI table 3898. A small number corresponds to a coarse grain, suitable for rough sanding, while the higher numbers identify an increasingly finer grain.
• the binding agent may be chosen from among those widely used in the sector, such as natural glues, ureic resins and phenolic resins.
• the abrasive powder on the backing may have a closed coating, that is to say with a high density of abrasive granules, suitable for hard materials and for a high quality finish; or an open coating namely with a low density of abrasive granules, suitable for ensuring high resistance to clogging.
• the abrasive disc may comprise additives, such as anti-clogging additives (zinc stearate) or anti-static products.
• the abrasive disc 102 comprises a plurality of through holes 10 on its surface, the function of which is to assist the removal of the dust formed during sanding.
• Figures 6A and 6B show the sequence in which the abrasive tool 1 is assembled starting from a plurality of abrasive discs 2, 102. First of all, the discs are stacked, aligning the respective radial cuts 3. The discs are then bent together so as to bring the rims 11, destined to form the working rims of the tool, into a position offset from the opposite rims 12, which instead remain hidden under the abrasive surface 4 (figure 6 ⁇ ) .
• the bottom disc of the stack is rotated in the direction of the arrow, around an axis perpendicular to the disc and passing through the centre, then in succession all the other discs from the bottom to the top, so as to achieve a staggered configuration which gives rise to the lamellar-like abrasive work surface 4 (figure 6b) .
• the number of abrasive discs 2 composing the abrasive tool 1 may vary from a minimum of two discs to a dozen or more.
• the flap 5, that is the portion of disc emerging and thus exposed to globally form the abrasive work surface 4 becomes increasingly smaller.
• the lamellar-like configuration of the tool will comprise a large number of flaps 5, each of which presenting a sharp edge 11 which constitutes the part of greatest friction and which during use works harder and is therefore subject to greatest wear.
• the abrasive tool 1 may then be mounted on a polishing pad 13 of a sander 14 (shown schematically in figure 5) by means of a suitable stop screw 15.
• the pad 13 typically has a central depressed area 16 with a hole.
• the stop screw 15 passes through the central hole 7 of the abrasive tool and through the hole of the pad 13 before screwing onto the rotating plate 17 of the sander 14. This way, the head of the stop screw 15 is positioned under the abrasive surface 4 which is instead supported by the outer portion of the pad 13, and does not therefore interfere with the surface to be sanded.
• This type of attachment of the tool to the sander is permitted by the flexibility of the material with which the abrasive tool 2 is made and by the presence of the slots 8 which form the tongues 9 suitable to be bent downward and clamped between the head of the stop screw 15 and the surface of the central depressed area 16 of the polishing pad 13.
• the abrasive surface 4, and in particular the rims 11 of the discs 2, 102 are worn, it is possible to remove, for example by cutting with scissors or another cutting tool, the worn flaps 5 or just the portion thereof comprising the edge 11, and if necessary repeating the operation of rotating the single discs shown in figure 6B, maintaining the initial staggering. This way, new portions of disc which will form the new flaps 5 are uncovered. It is thus possible to exploit to the most the abrasive surface of each disc 2, 102, gradually renewing the abrasive work surface .
• the single discs 2, 102 may also have radial weakening lines or in any case radial lines traced on them to facilitate the removal of the worn segment and keep a straight edge 11.
• the discs 2, 102 which form the abrasive tool 1 have the same grain.
• abrasive discs of a different grain 2, 102 are used, in particular arranging the different discs in succession with an increasing (or decreasing) grain. This way it is possible to obtain the sanding and finishing of a surface in drastically shorter times than with the conventional technology which provides for subsequent passages with disks of an increasingly finer grain.
• the abrasive discs 2, 102 have a so-called multi-abrasive surface, as disclosed in the prior Italian patent application no. MI2011A000850 (filed on 16 May 2011) by the same applicant.
• Multi-abrasive surface means an abrasive surface which has separate portions having a different grain.
• the arrangement of such portions on the surface of the disc may be according to various criteria but in particular those of creating a path in which the grain gradually increases or decreases. Arrangements in spots, concentric circles or spirals are for example possible. Reference is in any case made to the aforementioned patent application for a clearer understanding of the structure of such discs utilisable for the purposes of the present invention.
• the abrasive tool 201 comprises a plurality of half-moon abrasive elements 202 in place of the abrasive discs 2, 102.
• Such half-moon element 202 may be made from the abrasive discs 2, 102 by cutting along the entire diameter of the disc.
• Each half-moon element 202 comprises an abrasive surface 204 and an opposite velcro surface 240, of the female or male type, such surface 240 being destined to cling to a velcro surface of the complementary type attached to the polishing pad 13 of a sander 14.
• the plurality of half-moon abrasive elements 202 are arranged so that the single elements are staggered as shown in figure 7 (only three abrasive elements 202 have been shown for sake of clarity) , revealing the flaps 205, and the assembly thus composed is applied to the velcro on the polishing pad 13.
• This embodiment has the advantage of making the fitting of the tool more practical in that the underside, that is to say the velcro surface, would make the reciprocal sliding of the whole discs difficult.
• the abrasive tool 1 according to the present invention has many advantages.
• abrasive tool makes it possible to create a lamellar-like configuration by means of a simple and economical process. It is not in fact necessary to predispose the rigid backing in plastic or metal to which the flaps of conventional lamellar discs are glued. This translates not only into reduced production costs, but also into a reduced quantity of waste material at the end of the tool's life.
• the tool according to the invention combines the flexibility of conventional flexible discs with the typical characteristics of a lamellar configuration, something which is instead absent in the flap discs of the prior art.
• the possibility of reciprocally rotating the various abrasive discs composing the tool makes it possible to remove the worn abrasive surface, increasing the life of the tool and making it possible to practically use almost the entire surface of each disc.
• the abrasive discs composing the tool may have a different grain from one another or have a variable grain surface, as said above, which reduces the number of sanding cycles when operations are in progress.
• abrasive tool 1 may be fitted onto various types of sanders, such as rotary sanders, orbital sanders, roto-orbital , planetary, if necessary after suitable adjustments either structural or dimensional of the various types of machine used, adaptations which fall within the normal skills of a person skilled in the art and which do not depart from the object of the present invention as defined in the appended claims.
• sanders such as rotary sanders, orbital sanders, roto-orbital , planetary

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Polishing Bodies And Polishing Tools (AREA)

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• 2013
  • 2013-05-07 IT IT000734A patent/ITMI20130734A1/it unknown
  • 2013-07-09 US US14/787,308 patent/US20160074999A1/en not_active Abandoned
  • 2013-07-09 EP EP13765475.2A patent/EP2994270A1/en not_active Withdrawn
  • 2013-07-09 WO PCT/IB2013/055639 patent/WO2014181157A1/en active Application Filing

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