GB2169227A - Rotary grinding or polishing device - Google Patents

Abstract

The device, for acting on complex surfaces, consists of a number of grinding or polishing discs (1) each consisting of two or more layers of segments (2) radiating from a retaining area which forms an edge (3) around a central hole (8). In the retaining area the segments are kept together by a heat-activatable string (4) which also keeps together the grinding or polishing disc in the form of a ring. A series of discs are retained in foamed material rings at their inner peripheries, the rings spacing the discs axially. <IMAGE>

Description

SPECIFICATION Rotating grinding or polishing disc The invention relates to a grinding or polishing device of the kind consisting of one or more substantially circular grinding or polishing discs each having a central hole said grinding or polishing discs having radial grinding or polishing segments arranged along the periphery.

Such rotating grinding or polishing devices are eg. used for grinding or polishing furniture parts such as louvered or panelled doors. By such objects it is very often difficult to obtain a good and uniform grinding or polishing result because the objects will often have a very complex shape with projections, hollows, grooves etc.

A rotating grinding or polishing device of this kind is described in eg. the specification to US patent no. 2,879,631 disclosing a brush. This brush consists of a large number of slit or slotted sheets of stiff sheet material having been coated with abrasive materials which sheets by the folding thereof are retained in a metal channelform back element.

This structure, however, is encumbered with several drawbacks. It is for example costly as well as inconvenient to use a metal channelform element.

This way of assembling the grinding or polishing disc is also inadvantageous because the segments cannot be fully joined together. This will have the effect that the segments relatively often break off.

It is a further drawback that the segments can only with difficulty turn their abrasive surfaces in towards the object because they are made of stiff material such as thin spring steel. This will produce an uneven and poor grinding or polishing result.

Finally, this known structure is rather heavy which will necessitate a comparatively powerful motor and which will also impair the polishing quality.

All things considered this known structure cannot grind or polish wooden objects, for example, that are not quite even because the segments simply cannot follow the configuration of the object.

At the same time the brush is both expensive and difficult to manufacture.

The bbject of the invention is therefore to provide a light-weight and cheap grinding or polishing device that is capable of grinding or polishing even very complex surfaces.

This object is achieved according to the invention in that each grinding or polishing disc is provided with two or more substantially parallel layers of grinding or polishing segments, and that the segment layers along the edge of the central hole are kept together by a binding material situated between the layers.

The grinding or polishing device according to the invention is very cheap in manufacture becuase no complicated metal parts are required for holding together the individual grinding or polishing discs.

Thus the grinding or polishing device is not either heavy which will make it possible to use a smaller - and cheaper - motor. Since the grinding or pol- ishing segments are effectively retained, the grinding or polishing device can last for a comparatively long time. The grinding or polishing performance is good because the segments will bend in such a manner that the grinding or polishing coatings will follow the surface of the object for a comparatively large part of a turn.

The light segments can follow "hollows or grooves" in the object because the rotation will carry them outwards. The grinding or polishing quality will also be high because each individual segment can follow the object freely but nevertheless have such stiffness that for example knots or projections are also ground or polished.

As disclosed in claim 2, a grinding or polishing device according to the invention can be characteristic in that along the entire edge the binding material extends somewhat radially for forming a retaining area. There is hereby achieved partly a high degree of durability of the grinding or polishing disc and partly a suitable stiffness of the retaining area. This stiffness has proved to be of great importance to the quality of the grinding or polishing result because the segments must follow the configurations of the object but still engage same with a certain pressure.

If the two layers of segments, as disclosed in claim 3, are formed integrally, the grinding or pol- ishing disc being made of substantially rectangular slit sheet material which has been folded and joined to form a ring, there is obtained a very eas ily manufactured and cheap grinding or polishing disc with the smallest possible consumption of material, Moreover, there is obtained a suitable distance between two adjacent segments so that these are freely movable.

It is advantageous if as disclosed in claim 4, the binding material is a heat-activatable material. It is thereby possible to easily form a suitably wide retaining area by pressing the grinding or polishing disc between two heated jaws.

A preferred embodiment of the invention is characteristic in that the heat-activatable material has the shape of a string. By letting the ends of the string meet, the string will keep together the ring while at the same time ensuring the stiffness in the retaining area.

A further strong grinding or polishing device is obtained if the string encircles the central hole several times as is disclosed in claim 6. It is thereby possible to quite exactly prepare the retaining area by means of the number of windings and the ring is kept together in a safe manner.

Finally, it is advantageous if the grinding or pol- ishing device is designed as disclosed in claim 7, the rings ensuring a sufficiently large distance between two grinding or polishing discs so that the segments thereof are freely movable.

The invention will be further described in the following with reference to the drawing, wherein: Figure 1 is a grinding or polishing disc for a grinding or polishing device according to the invention, Figure 2 is a section through the grinding or pol- ishing device in Figure 1 seen in the direction ll-ll of the arrows, and Figure 3 is a number of grinding or polishing discs assembled to form a grinding or polishing device according to the invention.

Figure 1 shows how a grinding or polishing disc 1 consists of (double) segments 2 radiating from a retaining area around a central hole 8. The grinding or polishing disc is for example made of cloth coated with an abrasive coating 9 but the use of other materials is also possible.

As will particularly be seen from Figure 2, the abrasive coating 9 is provided on the outside of the cloth layers.

By the edge 3 the two layers have been joined by melting a string 4 of a heat-activatable material between the layers. There is thus obtained a retaining area being suitably stiff but nevertheless flexible.

These properties are very important to an effective grinding or polishing result.

It is therefore possible to use materials other than heat-activatable ones. The use of various kinds of glue or the like is thus possible.

During the grinding or polishing process the segments 2 will bend so that the abrasive coating follows the surface of the object. If desired, the bending may be facilitated by weakening lines.

Figure 3 clearly shows how a number of grinding or polishing discs 1 are assembled to form a grinding or polishing device having intermediate rings 7.

Apart from retaining the discs 1 the rings 7 are intended to provide a suitable distance between the segments 2 so that these are freely movable.

The rings 7 are advantageously made of foamed material such as polystyrene, the rings 7 thereby being light as well as strong. It is of course possible to make use of other suitable materials.

The heat-activatable string 4 encircles the hole 8 several times thereby obtaining a strong disc with good properties. It has been found that grinding or polishing discs having a diametre of approx. 30 cm, a central hole of approx. 10 cm and a width of segments of approx. 5 mm have outstanding abrasive properties. In this respect it is important that the segments are of suitable width in that otherwise it will not be possible to adjust the grinding or polishing process. Finally, the rings 7 are advantageously almost twice thick as the width of the segments 2.

It is essential to the grinding or polishing process that there is comparatively good space between the segments. It is thereby avoided that the segments entangle during the process thus reducing the abrasive effect and that the grinding or pol- ishing device is damaged.

It is also important that the segments are dimensioned so as to be able to freely follow the surface of the object.

When working with lacquered objects this will thus make an expensive, manual grinding or pol- ishing process superfluous because the small fibres formed by a usual rough grinding can now for the first time be machined away by a grinding or polishing device according to the invention. For this device possesses the optimum combination of distance between segments, flexibility of segments, stiffness in the retaining area and the possibility of fast rotation, namely between 900 and 1200 revolutions per minute. Therefore the grinding or polishing device according to the invention has also proved to be superior to all other makes in the market since no grinding or polishing devices whatsoever can grind or polish with an equally high quality as the grinding or polishing device according to the invention.

Claims (8)

1. Grinding or polishing device of the kind consisting of one or more substantially circular grinding or polishing discs each having a central hole said grinding or polishing discs having radial grinding or polishing segments arranged along the periphery, characterised in that each grinding or polishing disc (1) is provided with two or more substantially parallel layers of grinding or polishing segments (2), and that the segment layers along the edge (3) of the central hole (8) are kept together by a binding material (4) situated between the layers.

2. Grinding or polishing device according to claim 1, characterised in that along the entire edge (3) the binding material (4) extends somewhat radially for forming a retaining area.

3. Grinding or polishing device according to claims 1-2 and having two layers of segments, characterised in that the two segment layers are formed integrally, the grinding or polishing disc (1) being made of substantially rectangular slit sheet material which has been folded and joined to form a ring.

4. Grinding or polishing device according to claims 1-3, characterised in that the binding material (4) is a heat-activatable material.

5. Grinding or polishing device according to claim 4, characterised in that the heat-activatable material has the shape of a string.

6. Grinding or polishing device according to claim 5, characterised in that the string encircles the central hole (8) several times.

7. Grinding or polishing device according to claims 1-6, characterised in that a number of grinding or polishing discs (1) are joined around a common axis by means of rings (7) being adapted to retain the grinding or polishing discs between themselves.

8. Grinding or polishing device substantially as hereinbefore described with reference to the accompanying drawings.