This invention relates to compounding elements and in particular to compounding elements used to finish the exposed surface of paint, such as, on automobiles.

Finishing the exposed surface of new paint such as on an automobile, (particularly paint of the type called BC/CC (basecoat/ clearcoat) which is a two- part paint system and is commonly used in after market painting of automobiles but also including other types of paint), typically includes (1) initial colour sanding which is done by hand using fine grit abrasive (e.g., 1200 to 1500 grit) that provides substantial smoothing or levelling of the paint surface but results in surface scratches from the abrasive grit; (2) one or more intermediate compounding operations in which a liquid or paste rubbing compound containing a finer abrasive is applied by a machine rotated compounding pad having tufts of all wool or a wool and synthetic fibre blend to remove the scratches that result from the colour sanding operation, which compounding operation leaves swirl marks on the paint; (3) a machine glazing operation in which a glaze including a yet finer abrasive is applied using a glazing or polishing pad to remove the swirl marks, which machine glazing operation leaves wheel marks that are particularly noticeable on dark colour paints; and (4) a final hand glazing operation in which a glaze including an even finer abrasive is applied by hand in an attempt to remove the wheel marks. Often, the hand glazing operation fills some of the wheel marks rather than removing them, so that after a short period of time or when the paint is subsequently washed, the fill in the wheel marks is removed and they can again be seen. In addition to the use of pads comprising wool and synthetic fibres, pads comprising a layer of open cell polymeric foam have been used in compounding operations. Foam pads are disclosed in US 3418675 and foam pads having a working surface comprising a plurality of spaced projecting portions defining recesses therebetween and disclosed in US 4962562. One of the problems associated with many known compounding pads is that they have a tendency to sling the rubbing compound onto an area adjacent the

working area. This means an operator has to waste valuable time cleaning rubbing compound off adjacent panels, windows and other unmasked areas and also, as a result of sling, much rubbing compound may be wasted. Chemically thickening the rubbing compound can help reduce sling but in many cases this leads to increased drag of the compounding element due to the stiffness of the rubbing compound spreadability.

It is an object of the present invention to provide a compounding element in which the propensity to sling rubbing compound is substantially reduced. Therefore according to the present invention there is provided a compounding element for use with a rubbing compound in the finishing of a working surface, the compounding element comprising a buffing surface and a resiliently deformable skirt around the perimeter of the buffing surface and projecting beyond the buffing surface such that, in use, application of pressure to the compounding element on a working surface causes deformation of the skirt so that the buffing surface contacts the working surface.

The compounding elements of the invention possess a skirt which contacts the working surface during the compounding operation retaining the rubbing compound in the vicinity of the buffing surface by providing a barrier to any sling. The skirt projects beyond the buffing surface and when the element is applied to a working surface the skirt contacts the working surface while the buffing surface remains spaced from the working surface. Application of pressure to the compounding element causes the skirt to deform moving the buffing surface in contact with the working surface.

The compound elements of the invention may be used in any of the compounding and glazing operations, the buffing surface and rubbing compound being selected for the appropriate task. Suitable buffing surfaces include natural fibres, synthetic fibres, combinations thereof and foams, such as those disclosed in US 3418675 and US 4962562.

The skirt may comprise any resiliently deformable material which does not abrade the working surface more than the buffing surface and rubbing compound. A preferred skirt is made of foam, particularly a soft foam, preferably having open

cells. The thickness of the skirt is selected such that it will retain the rubbing compound and will depend upon the resilience of the skirt material, the particular rubbing compound, the amount of rubbing compound used and the action to which the compound element is subjected in use e.g rotation speed. A suitable foam is an open cell polyester foam having a density in the range of 24 to 27 Kg/M ³ such as Type 4200 A commercially available from Caligen Foam Ltd, Accrington, U.K. In general foam skirts having a width in the range 5 to 25 mm and projecting 5 to 10mm beyond the buffing surface have proved to be acceptable, wider skirts being used for compounding element rotated at speeds above 2000 rpm. The skirt may be made from a strip of foam by joining the ends to form a ring and securing the ring to back-up pad or perimeter of the buffing surface. The ends and ring may be bonded with suitable adhesive or using transfer tape such as 3M No. 9485 Transfer Tape, commercially available from Minnesota Mining and Manufacturing Company (3M), St. Paul, Minnesota, U.S.A. In use the rubbing compound is either applied to the buffing surface or the working surface and the compounding pad placed on the working surface such that the skirt envelopes the rubbing compound. The compounding pad is subjected to vibratory or rotatory rubbing motion and pressure applied to bring the buffing surface in contact with the working surface. When the desired degree of abrasion has occurred the compounding element may be removed. Alternatively, in the case of a skirt being constructed of a suitable material for buffing or polishing, e.g., a wide skirt of polymeric foam, the pressure on the compounding head may be reduced such that only the skirt contacts the working surface and the rubbing motion continued to buff the surface with the skirt. Thus such a compounding element possesses two separate buffing surfaces.

The invention will now be described with reference to the accompanying drawings in which Figures 1 and 2 represent cross-sections through different compounding elements in accordance with the invention.

In the drawings like reference numerals refer to like parts. Figure 1 shows a cross-section through a compounding element in the form of a circular disc. The compounding element (2) comprises a back-up pad (4)

bearing a buffing surface (6) comprising an open cell polymeric foam having a plurality of spaced projecting portions (8) and recesses (10) as disclosed in US 4962562. A circumferential skirt (12) surrounds the buffing surface and is formed from a soft polymeric foam. The width "w" is generally in the range 5 to 25mm and the skirt (12) projects beyond the buffing surface (6) by a distance "h" which is generally in the range 5 to 10mm. Figure 1 shows the compounding element resting on a working surface (14).

With this design, when light pressure is applied to the compounding element the convoluted projections (8) come into contact with the area being compounded and provide the cutting action, whilst the soft foam skirt (12) provides a trap for any sling produced and also helps improve the smooth running of the compounding element. During the compounding operation recesses (10) of the convoluted foam act as mini compound reservoirs as rubbing compound is pushed into the recesses. This means that once the rubbing compound is used up all that needs to be done to release more compound is to stop the machine and apply pressure to the foam to compress the projections (8) to release compound from the recesses.

After all the rubbing compound is used up, pressure on the convoluted projections can be released and the action of the soft foam skirt (12) on the paint surface (14) aids in the clean up of any excess oils from the rubbing compound whilst polishing the surface to a high lustre finish. Using this design of buff, it is possible (depending on the rubbing compound used) to obtain a finish on a single colour black paint which requires no further refining, i.e., it is possible to achieve a one-step finishing operation.

Figure 2 shows a similar compounding element to that of Figure 1 which is formed by modification of a soft foam buff. A central portion (16) of a soft foam flat buf was cut out to such a depth as to allow the convoluted hard foam having projections (8) to sit just below the surface of the periphery forming the skirt (12). The mode of operation is identical to that described with respect to Figure 1. An advantage of this design is that the buffing surface (6) can be removed and replaced with a different material e.g. wool/polyester blend mop or a softer (or harder) convoluted foam.

Figure 3 shows a compounding element having a foam skirt surrounding a sliver knit wool/polyester blend mop. This design produces a higher degree of aggression compared to the use of foam.

Whilst these designs have been illustrated in the form of discs e.g. 5-1/4 inch discs which are a standard size used in the art, it will readily be appreciated the compounding elements may take a variety of different shapes e.g. square, rectangular, oval etc. depending upon the manner in which they will be employed e.g. manually, rotary machine etc. Furthermore the elements may be constructed to allow detachable fastening of the skirt and/or buffing surface to a back-up pad e.g. employing hook and loop fastening devices, mechanical fastening devices, pressure sensitive adhesives etc.