GB2077640A - Improvements in abrasive and polishing sheets - Google Patents

Abstract

An abrasive or polishing sheet has a brushed, knitted nylon material secured to it. The nylon has less than 20 loops or curls per square mm. A carrier pad has a material to which the sheet can be attached. The material of the pad has inclined stalks extending therefrom which have unhooked ends. These features result in a very low peel strength between sheet and pad.

Description

SPECIFICATION Improvements in abrasive and polishing sheets The present Invention relates to abrasive or polishing sheets which can be removably mounted on a backing pad so that the sheets can be readily exchanged for other sheets of different characteristics or for replacement when worn.

G.B. 1,205,267 discloses abrasive or polishing discs replacably attached to a carrier pad adapted to be mounted for rotation by a tool by providing the opposed surfaces of the disc and the pad with a plurality of interengageable self-locking fastening members. The tool carrier pad is provided with a looped mesh or fabric so that when the two are pressed together the loops fasten onto the hooks providing a self-locking fastening. A similar idea is described in G.B. 1,083,547.

This uses a woven textile sheet which provides the hooks and this is attached to the polishing head by means of a solvent activated precoating. The pad has a textile sheet providing the loops attached to the reverse of the polishing side of the pad.

In the present applicants British Patent Application No. 79.28718 (Case 4) it has been proposed to provide an abrasive or polishing sheet with a textile material made from continuous filament multi-filament yarn adhered to the reverse of the working face of the sheet and the free surface of the material being engageable by hooks.

In the present applicants British Patent Application, No. 79.28717 type (Case 3) it has been proposed to provide an abrasive or polishing sheet having indicia carried on its rear face overlaid by a material providing a surface engageable by hooks, the material being adhered to the said indicia carrying face of the sheet such that the said indicia and their information content remain discernable through the said material. Experimentation with these types of material has generally indicated that they are very advantageous as compared with prior proposals, but one disadvantage has arisen in practice.This is that, when the abrasive or polishing sheet is used, for example, as a disc on a polishing or sanding pad rotated at high speed and with a pressure against the article that is sanded or polished, it is found that the peel strength between the textile material and the hooked material tends to rise due to close interengagement of the hooks with the yarn to an extent very considerably in excess of the peel strength which arises from simply laying the abrasive or polishing sheet on the hooked material and smoothing it out by hand.

It is thought that the action of the pressure on the sheet during its used plus the torque exerted by the hooks on the yarn very considerably increases both the number and extent of engagement of the hooks with the yarn so increasing the peel strength as referred to above. In fact the peel strength is often found to rise to such a degree that it is very difficult to obtain disengagement of the sheet from the hooks by a simple peeling operation.

Accordingly, the object of the present invention is so to reduce the peel strength when the sheet is initially applied to the pad that rotation of the sheet under pressure does not produce a peel strength which makes it difficult to separate the sheet from the pad by a straightforward peeling operation, when it is desired to remove the sheet e.g. for replacement purposes.

According to one aspect of the present invention an abrasive or polishing system comprises a pad adapted to be connected to a sanding or polishing tool, and an abrasive or polishing sheet arranged to be removeably secured to the pad, one of the pad and the back of the sheet having a textile material adhered thereto which is made from a woven or knitted yarn having filament loops or curls extending from its surface remote from the pad or sheet, there being, on average, less than 20 loops or curls per square mm. of surface area of the sheet.

There may conveniently be on average less than 1 5 loops or curls per square mm. of surface area of the sheet. In an alternative embodiment there are between 4 and 1 8 loops or curls per square mm. and preferably between 6 and 10 loops per square mm.

According to another aspect of the present invention an abrasive or polishing system comprises a circular pad adapted to be connected to a power driven sanding or polishing tool and an abrasive or polishing disc arranged to be removeably secured to the pad, one of the pad and the back of the disc having a textile material adhered thereto which is made from a woven or knitted yarn which has filament loops or curls extending from its surface remote from the pad or sheet, and the other of the pad and the back of the disc having a layer thereon from which extend loop-engaging or curl-engaging members in the form of mono-filament stalks having unhooked ends.

According to yet another aspect of the present invention an abrasive or polishing system comprises a pad adapted to be connected to a power driven sanding or polishing tool and an abrasive or polishing disc arranged to be removeably secured to the pad, one of the pad and the back of the disc having a textile material adhered thereto which is made from a woven or knitted yarn which has filament loops or curls extending from its surface remote from the pad or disc, and the other of the pad and the back of the disc having a layer thereon from which extend loop-engaging or curl-engaging stalks having ends which face away from the layer. The stalks are preferably inclined in different directions.

The textile material is conveniently a brushed, knitted, mutifilament nylon material, and the textile material is preferably prepared by knitting, brushing, stretching, and setting in that order. The textile material may be adhered to the sheet or disc by a foam latex which may be transparent, like the textile material itself, so that indicia carried by the rear face of the sheet or disc are discernible through the textile material.

The invention may be carried into practice in a number of ways but one specific embodiment will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a plan view of the top free surface of a fabric to be applied to a sanding disc, at approximately 60 fold magnification.

Figure 2 shows the material of Fig. 1, at approximately 30 fold magnification.

Figure 3 is a perspective view of a layer of material having stalks thereon, and which is applied to an abrasive wheel, at approximately 30 fold magnification.

Figure 4 shows part of the material of Fig.

3, at approximately 60 fold magnification, and Figure 5 is a magnified photo-micrograph of a cross section through an abrasive disc in accordance with the invention at approximately 60 fold magnification.

The photo-micrographs of Figs. 1 to 5 were taken on a scanning electron microscope. The photo-micrograph of Fig. 5 was prepared bycutting a clean cross section through the sample of sanding disc. The surfaces to be viewed were then coated with a thin metallic, e.g., gold or palladium reflecting layer as is conventional in preparing samples for electron photo-micrography. A stream of electrons was then directed onto the cut surface at 45 and the electrons reflected from the surface also at 45 were collected and used to produce an optical image. It will be appreciated that the depth of focus of such photographs is very much greater than in optical photography and thus in effect one is able to see into the interior of the fabric.

In the example illustrated a thin paper sheet had 100 mesh abrasive grit applied to one face in conventional manner and its rear face printed with the grit size and any other data required, such as the manufacturer's name, trade mark, and grading code for the product.

A layer of foam latex adhesive of a transparent nature was then employed to laminate to the paper a thin textile fabric formed from brushed nylon. The adhesive was dried and the sheet cut into discs or strips. The discs are used for rotary sander pads and are cut to preferably have a slightly larger diameter than the pads with which they are to be used.

Strips are used for orbital sanders which have rectangular abrasive sheets. The printed indo , cia on the sheet were formed with relatively large letters for example 7mm high and made of strokes 1 mm thick so tht they could be readily seen through the fabric.

The textile fabric comprised warp-knitted 28 gauge 30 denier multifilament type 66 nylon fabric. Specifically the number of filaments per strand of nylon was between 20 and 30.

One surface of the material was then very lightly brushed by using either fine needles or an abrasive paper on a roll in order to draw curls or loops from the body of the knitted fabric. Whilst the knitted fabric was knitted at 1 26 inch width its relaxed width was 72 inches. After brushing the material is stretched laterally to 95 inches and then heat set. This has the effect of reducing the number of curls or loops per square mm. In the example shown in Figs. 1 and 2 and the number of loops per square mm. is of the order of 8 but the invention broadly envisages a lightly brushed fabric having on average less than 20 loops or curls per square mm. of surface area of the sheet and desirably less than 1 5 loops or curls per square mm. of surface area of sheet.Alternatively there may on average be between 4 and 18, for example, between 6 and 10 loops or curls per square mm. of surface area of the sheet.

The weight of the resultant fabric was approximately 70 gramms per square metre.

Fig. 5 illustrates a cross-section of a sanding disc produced in this manner and which incorporates an abrasive layer 10, a backing paper layer 12, a foam adhesive layer 14 and a fabric layer 1 6 which has for example a section of multifilament yarn at 1 8 with a number of curls 20 drawn therefrom by the brushing process outlined above. The sanding disc shown in Fig. 5 prior to sectioning and photographing, had in fact been used a number of times for experimental purposes for adhering to a pad in a manner to be described and as a consequence, the number of curls or loops 20 shown in Fig. 5 is considerably in excess of the number shown in Figs. 1 and 2 due to further loops being drawn from the body of the fabric 1 6 upon separation of the disc from the pad.

Looking again at Figs. 1 and 2 it will be appreciated that the fibres which are drawn out in the form of curls or loops 20 are teased out of the main body of the fabric but these teased out fibres generally seem to have both ends retained within the fabric. The structure has a random appearance, the teased out fibres crossing each other and not being arranged in any readily discernible pattern in contrast to the basic knitted structure of the fabric which is highly ordered and made up from the knitted multifilament yarn.

Figs. 3 and 4 show a material which can be secured to a sanding or polishing pad and which comprises a woven base layer 30 again formed from multifilament yarn and which retains rows of spaced stalk-like members 32.

In contrast to many products (for example sold under the trade mark VELCRO) these stalks do not have hooked ends but have their ends cut so that they face away from the body of the sheet 30 although it will be seen clearly from Fig. 3 that the stalks, whilst inclined to the vertical are inclined in different directions.

It is found that on the one hand the very low number of hoops or curls produced in the textile sheet and/or the provision of simply stalks in the adhering layer, rather than hooks, lower the peel strength of the two materials when adhering one to the other to a very considerable degree as compared with standard products. As a consequence it is found that when these materials are employed for sanding operations at high speed and at considerable pressures, whilst the peel strength after such rotation and pressure does rise it does not rise to a level which makes it difficult to remove by a simple peeling operation by hand.

Claims (11)

1. An abrasive or polishing system comprising a pad adapted to be connected to a sanding or polising tool, and an abrasive or polishing sheet arranged to be removeably secured to the pad, one of the pad and the back of the sheet having a textile material adhered thereto which is made from a woven or knitted yarn having filament loops or curls extending from its surface remote from the pad or sheet, there being, on average, less than 20 loops or curls per square mm. of surface area of the sheet.

2. A system as claimed in Claim 1, in which there are on average, less than 1 5 loops or curls per square mm. of surface area of the sheet.

3. A system as claimed in Claim 1, in which there are, on average, between 4 and 1 8 loops or curls per square mm. of surface area of the sheet.

4. A system as claimed in Claim 1, in which there are, on average, between 6 and 10 loops or curls per square mm. of surface area of the sheet.

5. An abrasive or polishing system comprising a circular pad adapted to be connected to a power driven sanding or polishing tool and an abrasive polishing disc arranged to be removeably secured to the pad, one of the pad and the back of the disc having a textile material adhered thereto which is made from a woven or knitted yarn which has filament, loops or curls extending from its surface remote from the pad or sheet, and the other of the pad and the back of the disc having a layer thereon from which extend loop-engaging or curl-engaging members in the form of mono-filament stalks having un-hooked ends.

6. An abrasive or polishing system comprising a circular pad adapted to be connected to a power driven sanding or polishing tool and an abrasive or polishing disc arranged to be removeably secured to the pad, one of the pad and the back of the disc having a textile material adhered thereto which is made from a woven or knitted yarn which has filament loops or curls extending from its surface remote from the pad or sheet, and the other of the pad and the back of the disc having a layer thereon from which extend loop-engaging or curl-engaging stalks having ends which face away from the layer.

7. A system of claims in Claim 6, in which the stalks are inclined in different directions.

8. A system as claimed in any one of the preceding claims in which the textile material is a brushed, knitted, multifilament nylon.

9. A system as claimed in Claim 8,, in which the textile material is prepared by knitting, brushing, stretching and setting in that order.

1 0. A system as claimed in any one of the preceding claims in which the textile material is adhered to the sheet or disc by a foam latex.

11. A system as claimed in any one of the preceding claims in which the sheet or disc has indicia carried on its rear face which are discernible through the textile material.

1 2. An abrasive or polishing system substantially as specifically described herein with reference to Figs. 1 to 5 of the accompanying drawings.