Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D9/00—Wheels or drums supporting in exchangeable arrangement a layer of flexible abrasive material, e.g. sandpaper
  • B24D9/08—Circular back-plates for carrying flexible material
• • 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

Definitions

• the present invention relates to a process for the manufacture of an abrasive tool, in particular an abrasive tool for application on a power tool of the eccentric orbit sander type.
• abrasive sheet materials provided with small particles of a hard material on the surface have been known for a long time.
• Such abrasive sheet materials may be composed of a sheet of e.g. paper or cloth onto which grains of a hard material, such as sand, silicon carbide, tungsten carbide or the like is provided.
• a hard material such as sand, silicon carbide, tungsten carbide or the like is provided.
• Common products of such abrasive sheet materials are sand paper or emery cloth, which may be used for manually driven tools as well as for power driven tools.
• a very common type of a power driven tool using such an abrasive sheet material is a tool having a moving pad on which the abrasive sheet material is attached.
• An example of such a tool is an orbital sander which has a rectangular pad which under use is moving back and forth.
• eccentric orbit sanders or random orbit sanders respectively, in which the path of movement of the pad holding the abrasive sheet material is not linear, but rather eccentric.
• the abrasive sheet material for the tools of the eccentric orbit sander type is usually provided with attachment means on the non-abrasive surface in order for the sheet material to be secured on the moving pad.
• attachment means of the sheet material usually comprises one part of a Velcro fastening means (the loop part of the Velcro) whereas the pad on which the sheet material is to be attached, is provided with the other part of the Velcro fastening means (the hook part of the Velcro).
• Abrasive tools of the above type comprising such power driven tools however suffers from the disadvantage that the grains provided on the sheet material very quickly loose their respective adhesion to the sheet material used, resulting in a very rapidly declining abrasive efficiency. Furthermore, due to the somewhat fragile character of the sheet material, use of such material will under rough conditions eventually result in the sheet material itself being torn apart. The above features result in the need to a frequent renewal of the abrasive sheet material of the power tool, which is a time consuming operation as well as a rather expensive solution.
• Metal discs having abrasive material soldered thereon for application on an angle grinder are already on the market. In such a tool the disc is secured to the rotating shaft with a nut.
• the disc in order for a metal disc having abrasive material soldered thereon to be able to be securely attached to the Velcro fastening means under the working conditions of such an eccentric orbit sander, wherein quite violent forced are involved, the disc should have a weight that is not too high (i.e. the disc should not be too thick); if the disc is too heavy (too thick) the forces involved will be able to overcome the attachment forces of the Velcro tape, resulting in the disc leaving its position on the pad on which it is attached which may lead to a very dangerous situation. Accordingly it is essential that discs having relatively light weights (i.e. thin discs) are used for such power tools.
• the Velcro fastening means of a typically eccentric orbit sander tool e.g. of the type Würth Master ETS 150 Twin is capable of securely attaching a metal disc having a weight of not more than 42 grams (a typically paper disc has a weight of 34 grams).
• DE 1 288 950 B discloses a method of manufacturing an abrasive tool wherein particles of metal carbide are soldered to a thin steel plate.
• an abrasive tool made of metal sheet having soldered thereon grains of an abrasive material which abrasive tool is for example intended for a power tool of the eccentric orbit sander type, wherein the metal sheet is sufficiently thin in order to be securely attached to the fastening means involved, and wherein the metal sheet after being soldered is suitable for the intended application.
• the present invention is aimed at solving the problems set out above. This is accomplished by a process according to the present invention for the manufacture of an abrasive tool, in particularly an abrasive tool for application on a power tool of the eccentric orbit sander type, comprising:
• the abrasive tool primarily relates to application with a power tool of the eccentric orbit sander type it has been found, that the abrasive tool according to the present invention is highly useful in such applications of other types of power tools, wherein an abrasive tool can be attached to a pad on the power tool.
• Such other types of power tools comprises e.g. orbital sander type, an angle grinder or a sander of the type for use for sanding wooden floors.
• the abrasive tool is contemplated for use with any type of power tool allowing such tool.
• Even belt sanders/grinders of the hand held or floor grinder/sander type are contemplated as power tools which may be used with the abrasive tool.
• the abrasive tool is capable of providing an efficiency which may be more than three times the efficiency encountered with conventional abrasive tools (in the form of paper discs) in terms of time consumed in order to perform a given abrasive task.
• the reason for this efficiency is that the abrasive residues, such as e.g. dust appearing during the working of the tool is less prone to adherence to the spaces between the individual grains of the tool of the present invention, as compared to the situation for the conventional tools. This might be so because the grains are more sharp and more distant to each other, as compared to the prior art tools.
• the abrasive tool has a lead time which is 40 - 400 times the lead time of conventional abrasive tools.
• the present invention relates in a first aspect to a process for the manufacture of an abrasive tool, in particular an abrasive tool for application on a power tool of the eccentric orbit sander type according to claim 1.
• a metal body is applied with soldering paste on some of or all the area of a surface of the metal body. Then an abrasive material is applied to all or a part of said soldering paste whereafter the metal body is subjected to a heating zone for a period of time under a specific gas atmosphere during which the abrasive material becomes soldered onto the metal body, and it is subsequently subjected to a temperature declination in a curing zone.
• the process according to claim 1 may be performed manually as separate steps wherein the respective metal bodies are manually moved from step to step.
• the complete process in automatic, so that the metal bodies are moved from step to step via automatic conveying means.
• the metal body to be used as a starting material in the process according to the present invention may be selected from the group of metals termed "spring steel".
• a preferred metal to be used in the process according to the present invention is spring steel CK 75 (according to DIN 17222/1544) or spring steel CK 101.
• the metal body should be in sheet form having a thickness of 0.04 to 0.25 mm.
• the thickness of the metal plate may have a lower limit of 0.05, preferably 0.06, more preferred 0.07, yet more preferred 0.08 mm and most preferred 0.1 mm.
• the thickness of the metal plate may for example have an upper limit of 0.22 mm, such as 0.20, more preferably 0.18, yet more preferably 0.16, still more preferred 0.14, and most preferred 0.12 mm. If the abrasive tool is for application on a power tool of the eccentric sander type, the thickness of the metal body is preferably 0.2 or 0.1 mm.
• the shape of the metal body may be circular, triangular or any other suitable shape that fits well onto the pad of the power driven tool.
• Typical sizes for circular shapes are 0 115 mm, ⁇ 125 mm and ⁇ 150 mm.
• a typical size of a triangular shape is a triangle having identical curved leg lengths of 95 mm.
• the metal body is subjected to a cleaning and/or degreasing process prior to the application of the soldering paste.
• the cleaning and/or degreasing process will be performed by immersing the metal body in a cleaning and/or degreasing material, such as a detergent.
• a cleaning and/or degreasing material such as a detergent.
• any other suitable cleaning/degreasing materials and/or techniques generally used for such purposes are contemplated.
• the metal body which has previously been cut into a shape which makes the final product suitable for use with the intended type of power tool, is applied with a soldering paste to an area of the surface.
• This application may be performed by applying the soldering paste to the selected area of the metal body with a spray brush or a roller or in any other suitable way.
• the preferred way of application is application by spraying.
• the metal body is preferable applied with soldering paste on one surface only.
• the metal body which may have another shape, may be applied with soldering paste on more than one surface.
• soldering paste to be applied may be any kind of soldering paste which is suitable for the intended purpose of soldering the abrasive particles onto the metal body.
• soldering paste applied must be able to prevent to a high extend the loss of adherence of the abrasive particles to the metal body under the considerably strong forces applicable under use.
• particles of an abrasive material is applied onto the area of or onto a part of the area of the metal body which has been applied with the soldering paste.
• the application of the abrasive material may very well be performed simply by dispensing the grains of the abrasive material onto the metal body being applied with the soldering paste.
• the abrasive material to be used in accordance with the process of the present invention is tungsten carbide.
• the grain size of the tungsten carbide may be selected from the following: grain 36 (0.6 - 1 mm); grain 45 (0.4 - 0.8 mm); grain 60 (0.3 - 0.5 mm); grain 80 (180 - 250 micron); grain 120 (125 - 180 micron); grain 160 (75 - 106 micron); and grain 180 (45 - 75 micron).
• tungsten carbide is in this application intended to mean a sintered material comprising iron, carbon, tungsten, nickel, cobalt, chromium, niobium, tantalum and optionally also titanium.
• tungsten carbide is in this application intended to mean a sintered material comprising iron, carbon, tungsten, nickel, cobalt, chromium, niobium, tantalum and optionally also titanium.
• Such tungsten carbide grain material is commercially available in the above mentioned particle sizes.
• Such products may be obtained from the following companies: Höganäs, Belgium, Kenna Metal, USA and ZCCW, China.
• the abrasive tool is to be used as a sanding tool for finishing of for example wood or any other material that has to present a smooth surface it is important that the tungsten carbide particles are evenly or homogeneous distributed over the area that comes in contact with the material to be sanded. If these particles are not homogeneously distributed, the tool may leave behind traces or small grooves in the treated material.
• the abrasive material is applied onto the soldering paste of the metal body under the influence of a magnetic field.
• a magnetic field By applying a magnetic field during the application of the abrasive particles it is possible to orientate said abrasive particles in a desired direction in relation to the surface of the metal body.
• a desired orientation may be an orientation in which those particles having an oblong shape is arranged in a configuration in which they are aligned essentially perpendicular to the surface of the metal body. This will have the effect that the distance from the respective outermost points of the abrasive particles to the base of the metal body is increased compared to the situation in which no magnetic field is applied.
• the presence of an applied magnetic field during the application of the abrasive particles will give a resulting product which resembles a product obtained by use of larger particles of the abrasive material, but without applying a magnetic field.
• a magnetic field by applying a magnetic field a more coarse structure of the abrasive tool may be achieved without increasing the weight of the abrasive tool.
• the magnetic field applied may originate from an ordinary magnet, such as a rod-shaped magnet, or it may originate from an electromagnet.
• an electromagnet is preferred.
• the metal body now provided with soldering paste and tungsten carbide particles enters into a heating zone for the purpose of soldering the tungsten particles onto the metal body.
• the heating zone usually consists of a chamber which is provided with electrical heating means and means for supplying the specific gas atmosphere.
• a chamber may be a furnace, such as a belt furnace, a retort furnace or a vacuum furnace. A belt furnace is preferred.
• the actual temperature to be applied in the heating zone depends on the soldering paste which is used, and information relating to which temperature is useful with the specific soldering paste is usually given by the supplier of the soldering paste. Thus, a temperature of 984 degrees C is for example useful for the soldering paste Cubond Furnace Brazing Paste C699, mentioned above.
• the heating zone is provided with a specific protective atmosphere.
• the effect of such an atmosphere is to act as protection against the action of oxygen.
• protective gases cracked propane, cracked ammonia or a mixture of hydrogen and nitrogen is useful.
• the choice of type and composition of the atmosphere depends on the specific furnace type used and also on the preferred dew point, which on the other hand is determined by the soldering paste of choice.
• the supplier of the soldering paste can provide information relating to a preferred dew point for a specific soldering paste.
• the mixture of nitrogen and hydrogen is preferred due to the less aggressive properties of this mixture as compared to the cracked propane or the ammonia.
• Such protective atmosphere may be present in the heating zone in a composition ranging from pure hydrogen to a hydrogen/nitrogen mixture of 40:60 vol%, such as for example a hydrogen/nitrogen mixture of 90:10, 80:20, 70/30, 60:40 or 50:50 vol%.
• the time of residence of the metal body in the heating zone should obviously be sufficient in the way that it is ensured that the tungsten carbide are being soldered onto the metal body. Normally a time of residence of 5 to 30 minutes, such as 10 to 25 minutes is sufficient. A preferred time of residence of the metal body in the heating zone is 15 to 20 minutes.
• metal body upon exit from the heating zone enters into a curing zone in order to cure the product obtained so far.
• the curing of the metal prevents the resulting abrasive tool form being to fragile in respect of the harsh condition that will be encountered on the working condition. If not cured, the abrasive tool will simple be too prone to wrinkling when used for abrasive purposes on a power tool.
• the curing of the metal consists in a simple cooling of the metal bodies exiting the heating zone.
• the curing zone also comprises a chamber having a protective atmosphere.
• protective atmosphere the same types as applicable for the heating zone can be used.
• the course of the curing to be applied depends on the metal used.
• the supplier of the sheet metal can provide information relating to the curing temperatures and rate of decreasing temperature applicable for curing purposes.
• the curing consists in decreasing the temperature from approximately 900 degrees C to approximately 300 degrees C in a time span of approximately 2-3 min.
• the heating zone and curing zone are parts of the same apparatus.
• the heating zone is provided in a belt furnace wherein the metal bodies by means of a metal conveying belt enter from one end into the central part of the furnace which is provided with electrical heating elements and thus forms the actual heating zone.
• the metal bodies After having passed the heating zone enter into the curing zone which is provided in one end of the furnace.
• the curing zone has a lower temperature than the heating zone and this is provided by means of a water-cooled jacket surrounding the curing zone
• the conveyer belt transports the metal bodies out of the furnace.
• hydrogen is supplied in the central part of the furnace, whereas nitrogen is supplied at the entrance and exit openings, respectively, of the furnace.
• the abrasive tool When the metal body has finished its curing in the curing zone the abrasive tool is ready for application.
• the abrasive tool it is necessary for the abrasive tool to be provided with some kind of fastening means which allows the abrasive tool to be fitted on the power tool.
• fastening means thus depends on the specific power tool with which the abrasive tool is to be used.
• any suitable means are contemplated, such as Velcro tape, self-adhesive tape nuts and/or bolts etc.
• the abrasive tool is usually provided with the loop part of a Velcro tape.
• Velcro tape is commercially available in a form suitable for this purpose and is even manufactured with self-adhesive means on the non-Velcro side which may simply be applied to said abrasive tools.
• Such Velcro tape will - even under very rough working conditions - provide for a safe and efficient attachment of the abrasive tool to the corresponding pad on the power tool which is provided with the other part of the Velcro tape (the hook part).
• the adhesive of the Velcro tape should be able to withstand a temperature of approximately 90 degrees C.
• a comparison test was made in order to compare the abrasive tool with a conventional abrasive tool.
• the convention tool was a Bosch Redwood Top K40 sheet, and the inventive tool used was an abrasive metal tool having wolfram carbide soldered thereon of grain size 45 (which in fact is less coarse than the Bosch tool).
• the abrasive tools were successively attached to a Bosch GEX 150 eccentric orbit sander/grinder and applied as abrasive tools for the materials listed below.

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

Priority Applications (4)

Applications Claiming Priority (1)

Publications (2)

Family

ID=34745979

Family Applications (1)

Country Status (4)

Family Cites Families (6)

• 2004
  • 2004-03-02 EP EP04004832A patent/EP1570954B1/en not_active Expired - Lifetime
  • 2004-03-02 DK DK04004832.4T patent/DK1570954T3/da active
  • 2004-03-02 DE DE602004026991T patent/DE602004026991D1/de not_active Expired - Lifetime
  • 2004-03-02 AT AT04004832T patent/ATE466691T1/de not_active IP Right Cessation

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