BACKGROUND ART Applicator pads are used in conjunction with various compounds to treat the surfaces of a wide range of materials including paint, metal, composites and plastics.

The compound is normally in the form of a paste or liquid.

The pads are typically connected to the shaft of a rotary drive unit via a hub element which is fixed to one end face of the pad. The pad material is selected according to the surface to be treated or the particular stage of a series of treatments to the same surface. Typical materials are synthetic foams.

Known applicator pads are formed from a single type of foam the characteristics of which are selected to suit the required surface treatment process. Where the foam has a high density, the resulting pad will give a high degree of cut but gives relatively poor polishing.

Conversely, a softer foam with a lower density will give a lower degree of cut but improved polishing. There will be a variation in the characteristics of each foam pad dependent not only upon the batch of foam from which it was cut but also upon the area in each batch of foam from which the pad was cut.

To polish or abrade a surface, pressure must be applied through a hub element to the pad. This can be achieved by using a hub element with a rigid backing plate which extends across substantially all of one end face of the pad. However, this has the disadvantage that upon application of the pad to a surface, distortion of the pad can expose the rigid backing plate of the hub element to the surface with the consequent risk of damaging that

surface. Accordingly it is usual for the backing plate to have a diameter smaller than that of the pad.

In the pad assembly described in our International Patent Application published under No. WO-A- 95/27480 a hub element is located in a recess formed in an end face of the pad. This arrangement allows the pad to distort around the hub when in use, thereby minimising the risk of the hub element engaging the surface being treated and consequent damage thereto.

US-A-3924362 discloses a sanding pad assembly in which the pad is formed having a core of open cell foam and an outer layer of closed cell foam having properties different to that of the core. The outer layer is moulded to the core. Between the core and the outer layer there is provided a transition layer in which there is a gradual change in the physical properties between those of the core and those of the outer layer. The composite pad enables a pad to be formed having a desired hardness and resilience for a particular application whilst giving a durable pad with reduced susceptibility to tearing and ripping, and with reduced distortion when rotated at high speed.

SUMMARY OF THE PRESENT INVENTION According to the present invention, an applicator pad comprises a generally cylindrical backing section of a first type of foam and a generally cylindrical contact section of a second type of foam having different flexibility from the first type of foam, the backing section and contact section being attached together over a generally planar juxtaposed area thereof.

As the sections have different flexibility, the overall properties of the pad can be controlled to give any desired degree of flexibility or stiffness, and the flexibility of the pad and of different pads can be made more uniform than where the pads are made of a single section. In particular, the backing section can be formed of a foam having a high density to give a good cut, and the contact surface can be formed of a foam having a low

density to give good polishing. Where it is required to have a high cut but little polishing, both sections of the pad can be formed from high density foam. By forming the pad from two cylinders of foam, the pad will have a consistent flexibility across the entire contact surface of the pad. In particular, where the backing section is of denser foam, in use, pressure applied to the pad from the hub will be spread over the entire surface area of the backing section due to its high density and the pressure will be applied uniformly to the contact section over the entire contact surface. This is not the case in the prior art where the hub or backing plate has a diameter smaller than that of the foam pad to prevent the edges of the backing plate contacting and damaging the surface to be treated as the pressure is only applied to the central part of the foam pad. In the prior art arrangements, as pressure is not applied to the peripheral portions of the foam pad, these peripheral portions are not effective in treating the surface properly. However, as they extend outside the active portion of the pad they prevent the user from being able to see accurately the portions of the surface which are being treated by the pad. This precludes the treatment of a precise area. For example at the edge of an area to be treated, it will be necessary for the edge of the prior art pads to extend beyond the area to be treated as the edge portion does not treat the surface effectively. It will not be possible to position the edge of the active region of the pad accurately against the edge of the surface to be treated as the edge of the active region is within the peripheral extent of the pad. This problem is overcome with the present invention in that the same pressure is applied uniformly to the entire surface of the contact section of the pad, and therefore the edge of the pad needs merely to be aligned to the edge of the area to be treated.

An additional advantage of the present invention is that the generally planar contact surface between the

sections of the pad allows these to be attached by welding or by an adhesive.

Furtherstill, as the edges of the composite pad are exposed, a user can easily identify the material forming the different sections, and from this identify the properties, such as the flexibility, of the pad. This identification is even easier when the different materials from which the pad is formed have different colours or are otherwise made visually distinct to identify not only the materials used but also the combination of materials.

Multi-section applicator pads according to the invention will flex and deform in use in manners quite different from the pads previously available. Less flexible sections will reinforce those which are softer or more flexible, and the more flexible sections will allow greater wholesale movement of less flexible sections.

In preferred embodiments of the invention the pad has a rotational axis extending through the exposed surfaces of the backing and contact sections and the juxtaposed areas thereof. A recess can be formed in the exposed side of the backing section and the recess can be centred about the rotational axis to receive the hub of a rotary machine. Such a hub element typically has on one side a boss for coupling to a rotary drive unit and on the opposite side a surface for releasable connection to the pad. The attachment surfaces might for example comprise hook and loop fasteners.

An applicator pad according the invention can provide improved polishing and/or abrading performance over those of the prior art. In addition, because the two section of foam used in pads of the present invention are generally thinner than the single body of foam used previously, there is a reduction in the variations of characteristics of each foam section used in the applicator pads.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a plan view of an applicator head according to a first embodiment of the invention; and, Figure 2 is a cross-sectional view of the applicator head of Figure 1 along line A-A.

DETAILED DESCRIPTION OF PREFERRED EXAMPLE An applicator head according to a preferred embodiment of the invention is illustrated in Figures 1 and 2. It comprises a hub element 10 having a boss 12 which is integrally formed with a circular plate 14, and an applicator pad 16 comprising a backing section 20 and contact section 22. The cross-section of the applicator pad shown in Figures 1 and 2 is substantially circular.

The circular plate 14 may be attached to the backing section by any appropriate means. In the preferred embodiments illustrated in Figures 1 and 2 the plate fits into a complementary recess 24 formed in the backing section on one end face of the pad 16. Other configurations of the complementary surfaces may be adopted to provide different forms of engagement. The preferred method of releasably attaching the circular plate 14 to the applicator pad 16 comprises hook and loop fasteners, although other methods of attachment using for example pressure-sensitive adhesives, may be appropriate.

As shown in Figure 2, the applicator pad 16 comprises a backing section 20 and a contact section 22.

The backing section is permanently connected to the contact section for example by an adhesive or by welding.

The contact section is more flexible than the backing section. Typically this is achieved by selecting a harder foam for the backing section than for the contact section. The dimensions and characteristics of each foam section are selected to suit the task for which the applicator is designed to fulfil.

As shown, both the backing section 20 and the contact section 22 are generally cylindrical and have the same diameter. The attachment between the sections lies in a single plane generally parallel to the end faces of the

pad 16. In this way, the pad 16 in any plane parallel to the axis through the pad 16 has a consistent composition.

In order to polish or abrade a surface using the applicator pad, pressure is applied from the hub element to the surface to be treated via the applicator pad. Due to the relative stiffness of the backing section 20, pressure applied to the backing section 20 will be transmitted uniformly over the entire contact surface of the contact section 22. The pads are particularly suitable for use on a hub element overlaying only a central area of one distal end of the applicator pad as the less flexible backing section reinforces the pad to its periphery.

As a result of the way foam is manufactured, there are variations in the characteristics of each foam used in applicators, even with foams taken from the same production batch. The thicker the foam used, the greater the impact of these variations in terms of performance between applicators. Because applicator pads according to the current invention comprise two layers of foam having different characteristics, each individual section of foam is therefore typically thinner than the single block of foam used in prior systems. Thus, the impact of these variations is reduced.

As there is no extension of the contact section 22 around the side of the backing section, the side of the pad can be seen. This allows identification of the pad especially where the layers are of different colours.