Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B7/00—Machines or devices designed for grinding plane surfaces on work, including polishing plane glass surfaces; Accessories therefor
  • B24B7/20—Machines or devices designed for grinding plane surfaces on work, including polishing plane glass surfaces; Accessories therefor characterised by a special design with respect to properties of the material of non-metallic articles to be ground
  • B24B7/22—Machines or devices designed for grinding plane surfaces on work, including polishing plane glass surfaces; Accessories therefor characterised by a special design with respect to properties of the material of non-metallic articles to be ground for grinding inorganic material, e.g. stone, ceramics, porcelain
  • B24B7/224—Portal grinding machines; Machines having a tool movable in a plane
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B27/00—Other grinding machines or devices
  • B24B27/0076—Other grinding machines or devices grinding machines comprising two or more grinding tools
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24B—MACHINES, DEVICES, OR PROCESSES FOR GRINDING OR POLISHING; DRESSING OR CONDITIONING OF ABRADING SURFACES; FEEDING OF GRINDING, POLISHING, OR LAPPING AGENTS
  • B24B41/00—Component parts such as frames, beds, carriages, headstocks
  • B24B41/04—Headstocks; Working-spindles; Features relating thereto
  • B24B41/047—Grinding heads for working on plane surfaces

Definitions

• This invention relates to machines for smoothing/polishing flat slabs, in particular slabs of ceramic material (ceramic tiles), of natural stone (marble, granite and the like), or other equivalent materials.
• the invention can however be used for other materials, for example metal plates.
• the invention relates to those machines which use a plurality of grinding wheels rotating about their axis, their active face being in the form of a circular ring perpendicular to their axis of rotation (so-called cup grinding wheels), and comprise means for advancing the slabs below the field of action of the grinding wheels in contact with the active face of these latter.
• the known machines of this type comprise a unit (so-called "head") rotating at a relatively high speed (about 400 r.p.m.) about an axis perpendicular to the underlying surface on which the slabs rest, and able to slide axially both to compensate tool wear and to follow the slab irregularities.
• Said head carries a plurality of cup grinding wheels rotating about their axis, which is slightly inclined to the vertical so that at any moment only a small part of the active face of the grinding wheels is in contact with the slab.
• the axes of rotation of said grinding wheels are spaced from the axis of rotation of the head so that while the grinding wheels rotate about themselves, they are rotated by the head which rotates about its own axis while they act on the underlying slab.
• Disclosure of invention The object of the present invention is to provide an improved machine which overcomes said drawbacks.
• Figure 1 is a section on a vertical plane through a first embodiment of an individual grinding wheel.
• Figure 2 is a view of a first embodiment of the entire machine using the grinding wheels of Figure 1 , taken in a direction parallel to the direction of advancement of the slabs.
• Figure 3 is a section on the plane III-III of Figure 2.
• Figure 4 is an enlarged detail of Figure 3.
• Figure 5 is a section on a vertical plane through a second embodiment of an individual grinding wheel.
• Figure 6 shows the machine of Figure 3 using grinding wheels of Figure 5.
• Figure 7 is a section on an axial vertical plane through a second embodiment of the machine using grinding wheels of Figure 5.
• Figure 8 shows schematically the gearing of Figure 7.
• the machine comprises a plurality of grinding wheels each indicated overall by 10.
• Each grinding wheel 10 has a tool 11 (based on diamond, carbon, silicon or equivalent material granules) the active face 11' (ie the face which operates on the slab) of which is substantially flat, is in the form of a circular ring and is perpendicular to the axis of rotation M of the grinding wheel 10. More specifically, the shape which the face 11' assumes with use is a frusto-conical surface shape, the axis of which coincides with the axis M, and the vertex angle of which is nearly flat for the reasons given hereinafter.
• the grinding wheel 10 comprises a shaft 12 coaxial with M, to the lower end of which there is fixed a gripping member 13 into which there is securely inserted a disc 14, to the lower face of which the abrasive tool 11 is fixed.
• the machine also comprises a structure 41 , 60 (described hereinafter) which supports the grinding wheels above the slabs 3 to be machined.
• a belt conveyor 16 for example of the type comprising a horizontal conveyor belt 17 resting on a fixed surface 18 and arranged to advance the slabs 3 relative to the field of action of the grinding wheels 10 in contact with the faces 11'.
• the support surface P defined by the conveyor 16 is a normally horizontal and geometrically precise surface, in that it represents the reference plane for the machining of the slabs 3.
• each means 20 comprises a cylindrical bush 21 the outer cylindrical surface of which is rotatably engaged, via bearings 22, in a respective cylindrical through cavity 42 provided in the support structure 41 , 60 such as to be able to rotate about its axis S.
• the cavity 42 is provided directly within the structure 41 whereas in Figure 5 a bush 410 comprising said cavity 42 is joined to the structure 41, 60.
• the bush 21 comprises a central cavity 23 of cylindrical surface, the axis of which is inclined (specifically at a small angle of inclination) to the axis S.
• the grinding wheel shaft 12 is rotatable coupled, via bearings 24, with the cavity 23 such that its axis of rotation M coincides with the axis of the cavity 23.
• the axis M is therefore inclined at a small angle of inclination to the axis S of. the means 20.
• the geometrical centre C of the active face 11' of the tool 11 is positioned either on the axis S or close to it.
• the centre C represents the point of intersection between the ideal plane (or rather the frusto-conical surface) on which the face 11' lies and the axis M.
• the angle between the two axes M and S ensures that at any moment only a part 11a of the face 11' operates on the surface of the slab 3 so as to create a relief angle from which the material particles are removed from the machining region.
• This angle between the axes M and S is conveniently just a few degrees or some tenths of a degree.
• Respective means are associated both with the bush 21 and with the grinding wheel 10 to rotate both about the respective axes S and M.
• the upper portion of the bush 21 projects from the cavity 42 and has fixed to it a pulley 25 which is rotated about the axis S by a transmission belt 31 driven by a motor 33.
• the upper portion of the shaft 12 projects from the cavity 23 and has fixed to it a pulley 15 which is rotated about the axis M by a transmission belt 32 driven by a motor 34.
• the grinding wheel 10 is rotated about its axis M while at the same time the axis M rotates about the axis S to move over a conical surface, the vertex of which lies substantially within the axial dimension of the grinding wheel 10.
• this vertex is positioned within the central region of the pulley 15 to reduce the rocking of this latter to a minimum.
• the active face 11' As the axis M is inclined to the axis S, the active face 11', as stated, operates at any moment only with a portion 11a thereof (this portion changing continuously) which is distant from the axis S by approximately the radius of the active face 11'.
• the portion 11a As the axis M rotates about the axis S, the portion 11a also rotates about the axis S to produce a machining region in the form of a circular ring.
• the support structure for the grinding wheels 10 comprises at least one horizontal longitudinal member 41 positioned transverse to the direction of advancement of the slabs 3 and carrying at least one aligned plurality of support means 20 with respective grinding wheels, the tools of which are positioned very close to each other.
• the longitudinal member 41 is arranged to move vertically relative to the support surface P and is urged downwards with the grinding wheels in contact with the underlying slabs 3, at constant force.
• the longitudinal member 41 carries at least one pair of rows of grinding wheels 10 ( Figures 3 and 4 show two pairs of rows) in which the tools 11 are close and almost tangential to each other, the rows being offset in pairs such that the axes of the grinding wheels are positioned at the vertices of an ideal lattice formed from equilateral triangles.
• the pulleys 25 of the bushes 21 are close together, and between them there runs a transmission belt 31 which simultaneously engages the pulleys 25 of one row and those of the adjacent row.
• a single belt 31 acting with both its branches operates four rows of bushes 21.
• the pulleys 15 of the shafts 12 are also relatively close together, a transmission belt 32 simultaneously engaging the pulleys 15 of one row and those of the adjacent row following the same path as the other belt 31 but at a higher level than this.
• the belts 31 and 32 are driven by respective pulleys 35 and 36, themselves driven by respective motors 33 and 34.
• the return pulleys for the belts 31 and 32 are indicated by 37 and 38.
• Each row of tools 11 has a length equal to the useful width of the surface P on which the slabs 3 move, these completely filling this width as they are positioned one against the other to define a continuous surface of indefinite length.
• the longitudinal member 41 can be moved with translational movement horizontally and transversely, forwards and backwards, through a distance substantially equal to the radius of the tools 11 so that, in turn, all the end tools 11 of the row completely enter the plane of the slabs 3.
• the longitudinal member 41 is pivoted at one end, on a horizontal axis, to two vertical columns 43 (the figure shows only one column 43, the other being hidden by this latter) which are slidable as an exact fit within a guide member 44.
• This is slidingly supported by two horizontal, fixed cylindrical guides supported by a fixed base 46 which also supports the supports 47 for the conveyor 16.
• bracket 48 To the member 44 there is fixed a bracket 48, between which and the longitudinal member 41 there is positioned a cylinder-piston unit 49 which normally maintains the longitudinal member 41 in a horizontal position but can raise it vertically to allow maintenance, inspection etc. to be carried out.
• the longitudinal member 41 is thrust downwards so that the grinding wheels 10 operate on the slabs 3 with the required pressure, the longitudinal member 41 being also able to slide vertically both to compensate tool wear and to follow slab irregularities.
• the cylinder-piston unit 49 can be used to provide the required pressure on the slabs together with the weight of the equipment.
• the bush 21 is rigid with a pulley 25 which is rotated about the axis S by a transmission belt 31 driven by a motor 33.
• the pulley 25 projects upwards beyond the upper face of the structure 41 and of the bush 410 and is joined to the bush 21 by one or more shafts 251 which for space considerations can be curved or out of alignment as shown in Figure 1.
• An internal toothing 411 is fixed to the top of the bush 410 (and hence rigid with the support structure 41, 60), in a manner coaxial with the axis S of the means 20.
• a gearwheel 121 coaxial with the axis M of the grinding wheel 10 is fixed to the top of the shaft 12 and engages the toothing 411.
• the bush 21 is rotated (by the pulley 25 and the driven belt 31) about the axis S.
• the bush 21 drags with it the shaft 12, the axis M of which rotates about the axis S to describe a conical surface.
• the gearwheel 121 rolls on the toothing 411 to rotate the shaft 12 (and the grinding wheel 10) about its axis M.
• the grinding wheel 10 is also rotated, with the ratio of the rotation of the grinding wheel 10 about the axis M to the rotation of the axis M about the axis S depending on the geometrical relationship between the pitch circle diameters of the gearwheel 121 and of the toothing 411, which can be formed in the most convenient manner.
• the point of intersection between the axes M and S can be positioned as close as possible to the active face 11'.
• the portion 11a hence defines a circular ring virtually identical to the circular ring defined in plan view by the tool 11 , this having been found advantageous in practice for the proper operation of the tool.
• the angle of inclination between the axes S and M can be advantageously increased compared with the embodiment shown in Figure 1 so that the tool 11 operates in the most favourable geometrical configuration.
• FIG 6 shows the same machine embodiment as shown in Figures 2- 4, but with the aforedescribed modifications relative to the motorization of the grinding wheels 10 and bushes 21.
• this embodiment there is only one belt 31 driven by the motor 33 to simultaneously engage all the pulleys 25 (as already seen). Hence a single belt 31 operates all four rows of bushes 21 and hence all four rows of grinding wheels 10.
• a machine can be formed in which several grinding wheels act at the same time on each slab 3, even if relatively small.
• Figures 3 and 6 show tiles 3a and 3b having sides of 20 cm and 10 cm respectively, ie small slabs.
• the axis M of the grinding wheels 10 is virtually stationary.
• the polishing action on each slab 3 acts in circles which are small, numerous and mutually cross, to determine an extremely valid final polishing effect substantially constant in each region of the slab.
• FIG. 7 shows a different embodiment of the structure supporting the grinding wheels 10.
• This support structure comprises a cylindrical head 60 rotating about a central main shaft 61 of vertical axis, which is driven by a suitable motor (not shown).
• the head 60 supports a plurality of units comprising a grinding wheel 10 and support means 20 as shown in Figure 5, these being positioned at equal distance from the axis A, the arrangement being such that the tools 11 are close together, with their centres angularly equidistant.
• the head 60 supports a plurality of support means 20, for each of which the bush 21 is rotationally coupled to the head 60, via bearings 22, within a respective cylindrical seat 62 in the head 60.
• the bush 21 is free to rotate relative to the head 60 about its axis S, which is vertical (ie perpendicular to the surface P).
• the head 60 is rotated by one or more idle planet gears 63 (four gears 63 are shown in Figure 7) supported by shafts 631 carried by a cover 68 which is made fixed with respect to the rotation of the shaft 61 (by means not shown) and covers the head 60.
• the gears 63 engage a gearwheel 64 coaxial and rigid with the main shaft 61 , and simultaneously engage internal toothing 65 rigid with the head 60.
• the rotation of the shaft 61 hence causes the head 60 to rotate, via the planet gears 63, with a suitable transmission ratio, for example with an angular speed of 1/4 the angular speed of the shaft 61.
• each bush 21 is joined by its shaft (or shafts) 251 to a coaxial gearwheel 66, all said gearwheels 66 engaging a gearwheel 67 coaxial and rigid with the shaft 61. Consequently the rotation of the head 61 drags with it the gearwheels 66 which, engaged by the gearwheel 67, are rotated (and with them the respective means 20) about their axes S with a suitable transmission ratio, for example with an angular speed about 7 times the angular speed of the head 20.
• a plurality of said internal toothings 411 are fixed to the head 60, each coaxial with the axis S of the relative means 20, and with which the gearwheel 121 fixed to the shaft 12 of the respective grinding wheel 20 engages. Consequently, as already described with reference to Figure 5, the grinding wheels 10 rotate as a result of the rotation of the support means 20.
• Figure 8 schematically shows the aforedescribed gearing and the direction of rotation of the various gearwheels. The result is that while the grinding wheels 10 operate on the slabs 3, each describing a working region in the form of a circular ring (as already described), the grinding wheels undergo a circular path about the central axis A.
• this embodiment behaves as the traditional heads carrying grinding wheels rotating with a circular path.
• the result of the various movements to which each grinding wheel 10 is subjected, combined with the advancement movement of the slabs 3, produces on each slab 3 a polishing action extending as numerous small circles which mutually cross to determine an extremely valid polishing effect which is substantially constant in every region of the slab 3.
• the head 60 can be rotated at a lower speed, with the result that the various members are less stressed.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Ceramic Engineering (AREA)
• Inorganic Chemistry (AREA)
• Grinding Of Cylindrical And Plane Surfaces (AREA)

Applications Claiming Priority (5)

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ID=26331970

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• 1995
  • 1995-04-26 WO PCT/IT1995/000060 patent/WO1995030515A1/en not_active Application Discontinuation
  • 1995-04-26 AU AU23190/95A patent/AU2319095A/en not_active Abandoned
  • 1995-04-26 EP EP95916840A patent/EP0758287A1/de not_active Withdrawn

Non-Patent Citations (1)

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