NZ213537A - Grinding or polishing disc: grinding surface made up of radial "petals" - Google Patents

Description

-ami>*■- N.Z.No.

NEW ZEALAND Patents Act 1953 COMPLETE SPECIFICATION 213537 'ROTATING GRINDING OR POLISHING DISC" 1 *J\J We, UDVIKLINGSCENTRET HANSEN £ HUNDEB0L A/S, a Danish manufacturing and trading company, of Kanalvej 22, DK-6823 Ansager, Denmark, do hereby declare the invention, for which we pray that a Patent may be granted to and the method by which it is to be performed, to be particularly described in and by the following statement : - - 1 - (followed by 1A) »^v» * ' * i ,i V* 213537 lA 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 10 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 15 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 25 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 incon-30 venient 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. 155.

X < n -X • i 213537 2 1 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 5 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 10 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 15 follow the configuration of the object. At the same time the brush is both expensive and difficult to manufacture.

The object of the invention is therefore to provide 20 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 25 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 30 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 21353' 1 together the individual grinding or polishing discs. Thus the grinding or polishing device is not either heavy which will make it posssible to use a smaller - and cheaper - motor. Since the grinding or polishing 5 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 10 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 15 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 25 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 30 result because the segments must follow the configurations of the object but still engage same with a certain pressure. o If the two layers of segments, as disclosed in claim v '23S! r: ."J5 ^ t i ii ■■ w"» » y.---v>---- 1 3, are formed integrally, the grinding or polishing disc being made of substantially rectangular slit sheet material which has been folded and joined to form a ring, there is obtained a very easily 5 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 IS 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 20 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 25 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 polishing device is designed as disclosed in claim 7, the rings ensuring a sufficiently large distance between two grinding or polishing discs so that 213537 1 the segments thereof are freely movable.

The invention will be further described in the following with reference to the drawing, wherein: Fig. 1 is a grinding or polishing disc for a grinding or polishing device according to the invention, Fig. 2 is a section through the grinding or polishing device in Fig. 1 seen in the direction 11-11 of the arrows, and Fig. 3 is a number of grinding or polishing discs assembled to form a grinding or polishing device according to the invention.

Fig. 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 Fig. 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. /• / i ■ ^ 5 !> i Xvv. o 1 These properties are very important to an effective grinding or polishing result.

It is therefore possible to use materials other 5 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 10 the surface of the object. If desired, the bending may be facilitated by weakening lines.

Fig. 3 clearly shows how a number of grinding or polishing discs 1 are assembled to form a grinding 15 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. 20 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 30 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 advanta- 'a*** 2135 7 geously 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 polishing 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 polishing 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. - i ir rwwm. - ■ m 213537 ( i 8

Claims (4)

WHAT WE CLAIM IS:

1. A grinding or polishing device of the kind consisting of one or more substantially circular grinding or polishing discs comprising a member formed from a substantially rectangular slitted. flat sheet of material folded and shaped to have a central ring defined by two substantially parallel layers joined at an edge having a circular configuration which defines a central hole; radial grinding or polishing segments extending radially from the central ring in two substantially parallel layers, and an adhesive material is situated between the parallel layers along said edge of said central ring for securing the two layers of said central ring together and maintaining said sheet in said circular configuration, and wherein the adhesive material extends radially inwardly from said edge within said central ring to form a retaining area for the segments, and wherein said adhesive has the shape of a string which encircles the central hole several times.

2. A grinding or polishing device according to claim 1, wherein the adhesive material is a heat-activatable material.

3. A grinding or polishing device comprising a number of grinding or polishing discs as defined in claim 1 or 2 characterised in that there are a Plurality of rings for joining said discs around a common axis with each disc being spaced from an adjacent disc by at least one ring. p5*'1 y 213537

4. A grinding or polishing device according to claim 1 substantially as herein described with reference to the accompanying drawings. 4 Q UDVIKLINGSCENTRET HANSEN S. HUNDEBOL A/S By Their Attorneys HENRY HUGHES LIMITED \