The present invention concerns an apparatus for grinding/polishing a surface, including a grinding unit with a number of grinding members, a motor attachment, a motor and a screen, where the handle is mounted on the grinding unit, where the screen includes a number of grinding members that are rotatable about individual central axes, and where each grinding member has a abrading surface which is perpendicular to its central axis as hereby is formed a common abrading surface for the grinding unit.

Background of the Invention

When e.g. an old or badly maintained wooden floor is to be brought in order, it is typically planed/ground off before being finished with oil or varnish.

Moreover, there is a need for grinding/polishing surfaces of glass fibre or similar fibre reinforced composite surfaces in order to prepare these for surface treatment/coating. As examples can be mentioned wind turbine blades, boat hulls and boat decks.

Also, there is a need for grinding metal surfaces for preparing these for surface treatment/painting. The apparatuses used are typically floor planes/floor grinding machines with either a number of round plates with circular grinding wheels or a grinding cylinder with enclosing grinding belt. It is difficult to achieve uniform grinding of the floor, and that a large amount of grinding discs or grinding belts are to be used. The prior art apparatuses are typically large and heavy apparatuses which cannot easily be lifted by one person, and the weight entails that they may be difficult to manoeuvre. Furthermore, these apparatuses are usually provided with spacers in the form of height adjustable wheels, which is not an advantage as the grinding drums cannot optimally follow the contour of the underlying surface, but the spacing between grinding drum and underlying surface will instead be determined by the contour of the underlying surface at the spots where the wheels are running. Moreover, wheels will frequently prevent grinding/polishing from being effected up to adjoining walls and corners.

Also, it is also known with apparatuses with a grinding unit where a number of rotating grinding members are driven by a circular toothed rim at the circumference of the apparatus in order hereby to produce rotation about a central axis of each member, and at the same time establishing rotation of the members about a central axis of the apparatus. By these apparatuses, the said central axes will extend perpendicularly to the abrading surface of the members. By these apparatuses there no possibility either for grinding/polishing the surface in an edge area up to adjoining walls and corners due to the toothed rim.

Object of the Invention

It is the object of the present invention to indicate an apparatus which is easy to manoeuvre by grinding/polishing surfaces, and which is mechanical simple and has low self- weight. Moreover, it is the object to indicate an apparatus where it is possible to achieve grinding/polishing and cleaning that will get as close as possible to corners and adjoining walls.

Description of the Invention

This is achieved by an apparatus of the kind specified in the introduction to claim 1, which is peculiar in that grinding members are rotatably seated in a mounting plate, that the mounting plate is secured to a bracket fitting supporting the motor attachment, that the mounting plate is formed by two circular plates spaced apart with outer circumferences approximately corresponding to the inner diameter of the outer wall of the screen, that at least two suction pipes fastened to the two plates extend through the two plates, the suction pipes extending from the lower of the two plates to a point above the upper wall of the screen for suction of grinding dust, and that the screen is mounted loosely and can be displaced up and down as it is guided by the suction pipes and the mounting plate.

Suction thus occurs at the top of the grinding unit and does not prevent any part of the cylindric wall from being disposed close to a wall or against a corner. By a loose mounting of the screen for displacement controlled by one of the suction pipes, a light and mechanically simple apparatus is achieved as there is no need for special fittings or similar for mounting the screen.

The apparatus according to the present invention has a grinding unit to which may be associated an exhaust for the suction pipes passing through the screen. Hereby is achieved dustless grinding/polishing where dust is directly removed. Suction may occur via a separate hose associated with the handle.

According to a preferred embodiment, the apparatus according to the invention is peculiar in that the grinding elements include sandpaper items which are slit inwardly towards the surface of the disc. By slit sandpaper items is achieved a grinding which is particularly efficient as it follows the structure of the surface.

According to a further embodiment, the apparatus according to the invention is peculiar in that the grinding elements are mounted replaceable in axially extending grooves in the disc. This will facilitate replacement of the grinding elements.

According to a further embodiment, the apparatus according to the invention is peculiar in that each grinding member includes a circular disc and grinding elements mounted thereon, that each disc has a surface to which a first edge part of a number of grinding elements are mounted, as the grinding elements are oriented substantially at right angles to the surface of the disc, that the grinding elements extend radially in the grinding member, that the grinding elements have approximately the same height such that their opposing second edge part is disposed in and forms the abrading surface, that the screen includes a circular upper wall and a cylindric outer wall at the outer circumference of the screen, that the outer circumferences of the grinding members are about touching the outer circumference of the screen, and that the central axes for the grinding unit and the grinding members are parallel. As each of the grinding members are provided with radially extending grinding members or so-called grinding strips, it will be possible to let these grinding elements extend to the outer periphery of each of the grinding members, and thereby also to the outer circumference of the apparatus. Hereby it becomes possible to go very closely to sidewall, skirting boards, corners, or similar. There will be no risk of damage to skirting boards and walls as they are protected by the cylindric outer wall of the screen. The floor may be ground/polished right up to the edge, as the second edge part of the grinding elements, which is opposite the first edge part, is provided with grinding elements in the form of abrasive paper, brushes or similar for grinding/polishing the surface. Thus it becomes possible to avoid corner areas and corners where no grinding/polishing occurs. Since no apparatus parts that protrude beyond the grinding elements are required, it will be possible to establish grinding right up to an adjoining wall or skirting board.

The construction with motor and grinding elements rotating about parallel axes enables a particularly simple mechanical design with the motor disposed upon the grinding unit. The motor can then rotate the grinding members by a mechanically simple and light design, for example consisting of belt drive with drive belts or chains.

As the handle is mounted pivotable in a largely vertical plane, it will be possible to put the handle in an arbitrary position relative to the apparatus. Since the grinding apparatus is circular, there is obtained an apparatus which is easy to manoeuvre as the operator may turn the apparatus between different positions by forward and backward driving. The operator may simply move the grinding unit in an arbitrary direction without having to lifting the grinding elements off in order to change direction.

As all the grinding members perform grinding in a common grinding plane with rotation at right angles to the grinding plane and thereby the surface to be ground, a change of direction will not give any negative effect on the quality of the grinding. Due to the rotation of the grinding member and the superposed rotation performed by following grinding members, it will be possible to achieve overlapping grinding/polishing paths. Due to operation with a central motor which is connected to each of the grinding members via belts, chains or similar, it is possible to establish an arbitrary direction of rotation for the grinding members. This will further contribute to establishing a smooth and uniform surface without visibly crossing grinding/polishing marks. As the grinding members are disposed with their outer circumference touching the outer circumference of the grinding unit, it is ensured that no edge areas which are not ground/polished are left at adjoining walls or similar. In principle, the grinding members may be disposed at different distances from the central axis of the grinding unit. However, it is preferred that the grinding members are disposed with their central axes at the same radial distance from the central axis of the grinding unit. The outer circumference of all grinding members can hereby touch the outer circumference of the grinding unit when the all grinding members have the same diameter.

According to a further embodiment, the apparatus according to the invention is peculiar in that the motor is mounted in the motor attachment upon the grinding unit with rotation about the central axis of the grinding unit.

According to a further embodiment, the apparatus according to the invention is peculiar in that the grinding members are rotatably seated in a mounting plate, that the mounting plate is suspended rotatably such that both the mounting plate and the grinding members are rotated when the apparatus is operating. When the grinding members are mounted in a mounting plate, a particularly simple design is achieved where there is established a superposed rotation of the grinding members and the individual rotation of the grinding members when the apparatus is operating. The mounting plate will be rotated by the same rotor driving the grinding members. According to a further embodiment, the apparatus according to the invention is peculiar in that the motor is mounted rotationally fixed in the motor attachment, and that the handle is mounted pivotable in relation to the motor attachment. By such design, the need for a frame for the apparatus is avoided. The motor attachment will thus constitute part of the screen enclosing the grinding unit, and at the same time constitute an attachment for the motor. Hereby a relatively light construction is achieved. This design is furthermore advantageous as the handle is mounted pivotable in the motor attachment. Thus there is no need for a separate fastening of the handle. The motor attachment may in principle constitute a bushing, the inner side of the bushing being used for securing the motor, and where a bearing part is formed at the outer side of the bushing, interacting with a second bearing part disposed lowermost on the handle. Mounted on the handle, this will enable pivoting of the handle in a vertical plane. Hereby is achieved simple manoeuvring.

According to a further embodiment, the apparatus according to the invention is peculiar in that the grinding unit is supported on the grinding elements of the grinding members. Since the grinding unit is resting directly on the grinding members, a light construction is achieved, and the need for supporting elements, e.g. support wheels preventing unencumbered grinding/polishing close to walls, is obviated. Moreover, there is achieved the advantage that there are no separate support elements that may give rise to erratic grinding. By the apparatus according to the invention, the grinding elements of the grinding members will optimally follow the contour of the underlying surface, thereby providing correct grinding/polishing.

According to a further embodiment, the apparatus according to the invention is peculiar in that at least at its lower edge, the screen has a resilient sealing edge which extends to the grinding surface and establishes a dustproof connection with the surface. Hereby is achieved a dustproof connection with the ground surface without risking that the sealing edge, which e.g. is constituted by a rubber lip, will cause the grinding members not to follow the contour of the surface. The sealing edge rubber lip will therefore be made of a very soft and yieldable material so that the weight of the apparatus is borne by the grinding elements. Not just a lower edge area needs to be formed of rubber. A large part of the screen may be constituted by rubber which does not only extend at the sidewall but also at the upper wall of the grinding unit. Such a rubber screen may be fastened to a metal plate forming the motor attachment. Hereby, the amount of metal is reduced, enabling a lighter design.

As alternative to the rubber lips it will be possible to provide the screen with other elements that establish a dust sealing, including a number of brushes which are mounted at the edge area. As alternative to rubber, other materials may be applied as well, such as soft plastic materials.

According to a further embodiment, the apparatus according to the invention is peculiar in that the motor is mounted with its drive shaft rotatable about the central axis of the grinding unit, and that the drive shaft is provided with a belt drive, and that belts connect the motor belt drive with belt drives on each of the shafts of the grinding members. By establishing a belt drive on the drive shaft, it is possible to connect belts between the motor belt drive and belt drives on respective shafts of the grinding members, such that different directions of rotation can be achieved for each of the grinding members.

Moreover, it also becomes possible to establish different rotational speeds for the grinding members, if so desired. This may simply be effected by dimensioning belt drives on the drive shaft and the shafts of the grinding members in a suitable way.

According to a further embodiment, the apparatus according to the invention is peculiar in that the motor is a frequency controlled motor. Hereby it becomes possible to control the rotational speed of the grinding unit and the grinding members, respectively, without need of a separate gear. Hereby a mechanically simple and relatively light construction is achieved.

Belts, chains or similar which are connected with each of the grinding members such that they rotate in different directions enable establishment of easy control and thereby manoeuvring of the apparatus.

The apparatus according to the present invention is described as being used for grinding or polishing a surface. Grinding/polishing depends on whether grinding elements or polishing elements are used in the grinding members.

In the grinding members, the used grinding elements will typically be fastened in undercut grooves such that they can easily be replaced by drawing out/inserting the tools in the radially oriented grooves which are located in the circular disc of the grinding member.

The apparatus can be used on all surfaces where grinding/polishing is desired. The apparatus may thus be envisaged applied for grinding/polishing of wood, metal and/or fibre-reinforced plastic materials.

Description of the Drawing

In the following, the invention will be explained in more detail with reference to the enclosed drawing where:

Figs. 1-4 show an apparatus according to the invention in perspective view, from above, from the side and from below, respectively;

Fig. 5 shows a partial perspective and schematic view of an apparatus according to the invention where certain parts are removed;

Fig. 6 shows a partial perspective view according to Fig. 4, but with other apparatus parts removed;

Fig. 7 shows a partial view from above with some apparatus parts removed for illustrating the location of the motor and the grinding members; and

Fig. 8 shows a perspective partial view with some apparatus parts removed for illustrating the course of the belts.

Detailed Description of Embodiments of the Invention

Figs. 1-4 show an apparatus 1 for grinding/polishing a surface. The apparatus includes a grinding unit 2 in which is mounted a number of grinding members 3. In the shown embodiment, four grinding members 3 are mounted. Each grinding member is rotatable about its own central axis 4. The apparatus is symmetric and may therefore be operated with arbitrary rotation about the central axis 5 of the grinding unit .

Each grinding member has an abrasive surface, and all abrasive surfaces are located in the same grinding plane 6 (see Fig. 4). The abrasive face 6 is perpendicular to the central axes 4 and 5. The grinding apparatus furthermore includes a motor 7 and a handle 8. The handle 8 is provided with a handle 9 at one end, and at its other end it is connected with the grinding unit via a connecting arrangement generally denoted by the reference number 10.

Each of the grinding members may in principle be of the type described in European patent application EP 1 633 530, the content of which is hereby incorporated by reference. Each grinding member 3 thus includes a circular disc 11 (see Fig. 7) in which is provided a number of radially extending grooves 12. Each of the grooves 12 serve as support for a grinding element 13 (see Fig. 5), where a first edge part 14 is secured in the grooves 12. Each of the grinding elements 13 will thus extend largely at right angles from the surface 16 of the disc 11 in which the grooves 12 are formed.

All grinding elements 13 have approximately the same height. The opposite second edge part 15 will thus be placed in a common plane which coincides with the abrasive face 6.

As it appears particularly from Figs. 6 and 7, the handle 8 is mounted pivotable relative to the grinding unit 2. The handle 8 is therefore provided with a forked branch 17 where at the outer end of each forked branch there is provided an opening 18. The opening 18 may receive a hingepin 19 which at the same time is mounted on a bearing element 20 with an aperture 21 for the hingepin 19. Hereby is achieved possibility of pivoting the handle by up- and downward movements relative to the grinding unit 2. The bearing element 20 is mounted on a bracket fitting 25 (see Fig. 7).

In Fig. 7 is seen that the outer periphery 37 of each grinding member approximately touches the outer circumference 38 of the grinding unit 2. In addition, a ring element 22 is fitted on the bracket fitting 25. Together with the bracket fitting 25, it serves as a motor attachment. At its central part, the ring element 22 thus has a cutout for receiving the motor 7. At the same time, the ring element 20 constitutes an abutment for the bracket fitting for providing a secure contact surface. On the ring element 22 is mounted a screen 23, for example made of a rubber element which establishes a dustproof contact with the surface to be ground/polished. The screen has a circular upper wall 33 and a cylindric outer wall 34. As it particularly appears from Fig. 4, the lower edge 24 of the cylindric outer wall 34 will coincide with the abrasive surface 6.

In its upper circular wall 33, the screen 23 has two holes 35 for passage of suction tubes 36 that are passed loosely through the holes 35.

In Fig. 5 is seen that the bracket fitting 25 is mounted on a mounting plate 26 which is formed bye two separate plates 26A and 26B. Hereby it is possible for the plates to support bearings 27 for each of the shafts 28 of the grinding members. Each grinding member has a shaft 28 supported by bearings 27 in each of the plates 26A and 26B. A pulley 29 is mounted on the shafts 28 at a position above the upper plate 26B. The pulleys 29 are driven by a pulley 31 (see Fig. 7) on the drive shaft 32 via belts 30.

The suction pipes 36 are fastened to the two plates 26A and 26B and will extend from the lower plate 26A to a point above the screen 23.

As it particularly appears from Fig. 8, the pulleys 29 are connected in pairs by a belt 30 such that two belts 30 are used for driving the shown four grinding members 3. The grinding members 3 will run in opposite directions in pairs due the way in which the two belts 30 are mounted.

The motor 7 is secured against rotation in the bracket fitting 25 and thereby the ring element 22, providing rotation to each of the grinding members 3.