THIS INVENTION relates~-to an improved -rotary -brush. -- It-is particularly, although not solely, applicable to a rotary floor maintenance brush.

Rotary floor maintenance brushes generally comprise a base and a plurality of outwardly sloping fibres projecting from one ^" side of the base. To permit such brushes to be used for both scrubbing and polishing operations, it has been proposed to provide the fibres with varying abrasive characteristics, the fibres of greater abrasive charac¬ teristics being located towards the centre of the brush and the fibres of lesser abrasive characteristics being located towards the outer periphery of the brush. In operation of the brush, the speed at which the fibres travel varies increasingly towards the outer periphery of the brush. The slower moving, more abrasive fibres at the inner region of the brush perform the scrubbing operation while the faster moving, lesser abrasive fibres at the outer region of the brush perform the polishing operation.

Because of their varying abrasive characteristics, the fibres have varying wear rates; the fibres at the outer region of the brush wear at a faster rate than those at the inner region of the brush. During the operating life of the brush, this difference in wear rates ultimately leads to fibres wearing to different lengths, the longest fibres being located at the inner periphery of the brush. Because of the outwardly sloping nature of the fibres and the forces exerted on the fibres during operation of the brush, the fibres become distorted and longer fibres tend to overlay their neighbouring shorter fibres. This has three adverse affects on performance of the brush. First, the overlying fibres tend to shield the floor or other surface being treated by the brush from the underlying

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fibres and this diminishes the performance of the brush. Secondly, the free ends of the longer, more abrasive fibres move further from the centre of the brush and so travel at an increased speed during operation of the brush; gain speed; this is detrimental to the polishing operation performed by the brush. Thirdly, the contact area between the floor surface being treated by the brush and the tufts of fibres increases owing to the change in slope of the distored fibres. This is because the plane of contact between each tuft and the floor or other sur¬ face is inclined to the length of the tuft rather than being normal thereto. These three factors have cumulative effect in progressively decreasing the operating perfor¬ mance of the brush throughout its service life.

It is an object of this invention to provide a rotary brush in which the performance characteristics of the brush do not vary significantly throughout the service life of the brush.

In one form the invention resides in a rotary brush having a base and a plurality of fibres projecting from one side of the base, characterised in that the fibres at the inner region of the brush are sloped inwardly towards the centre of the brush.

According to a preferred feature of the invention, the free ends of the fibres define a working face, the fibres being of varying length whereby the space between the working face and said one face of the base increases in the direction towards the centre of the brush.

According to a further preferred feature of the invention, the fibres at the outer region of the brush are sloped outwardly away from the centre of the brush.

The fibres are preferably of varying abrasive characteris¬ tics, the fibres of greater abrasive characteristics being located- towards .the- centre .of the brush, and-t e^fibres...oi lesser abrasive characteristics being located towards the outer periphery of the brush.

The fibres may be of varying diameter and abrasive charac¬ teristics, the fibres of larger diameter and greater abrasive characteristics being located towards the centre of the brush and the fibres of smaller diameter and lesser abrasive characteristics being located towards the outer periphery of the brush.

The fibres may be of varying diameter and abrasive charac¬ teristics, the larger more abrasive fibres impregnated with abrasive particles being positioned in the central region of the brush and decreasing in diameter and abra¬ sive characteristics to the least abrasive unimpregnated fibres in the outer periphery of the brush.

The fibres are preferably arranged in'tufts. The tufts are preferably arranged in rings about the centre of the brush.

The tufts may be arranged in a plurality of bands, the fibres in each band being of uniform abrasive characteris¬ tics.

The invention will be better understood by reference to the following description of one specific embodiment thereof. The invention will be described with reference to the accompanying drawings in which:-

Fig. 1 is a schematic sectional elevation of a prior art rotary brush, illustrating the brush in its unworn state;

Fig. 2 is a view similar to that of Fig. 1, except that the prior art brush is shown in a worn state; Fig. 3 is a schematic sectional elevation of a rotary brush according to the invention.

Referring to Figs. 1 and 2 of the accompanying drawings, the prior art brush 11 comprises a circular base 13 from one face 15 project a plurality of fibres 17 which slope outwardly away from the centre of the brush. The fibres 17 are grouped in tufts 18 and are of varying abrasive characteristics, the fibres of greater abrasive charac¬ teristics being located towards the centre of the brush and the fibres of lesser abrasive characteristics being located towards the outer peripheriy of the brush. The tufts of fibres of the illustrated prior art brush are grouped into three bands according to their abrasive characteristics. There is an inner band 19 having fibres with the highest abrasive characteristics, an intermediate band 21, and an outer band 23 having fibres of the lowest abrasive characteristics. The inner band of fibres 19 performs a scrubbing action for dirt removal, the inter¬ mediate band 21 travels at a faster rate than the inner band and prepares the floor surface for a polishing opera¬ tion which is performed by the outer band of fibres 23.

The fibres in the outer bands 23 wear at a faster rate than those in the intermediate band 21-which in turn wear at a faster rate than those in the inner band 19. Because of the difference in wear rates, a wear pattern is esta¬ blished in the brush whereby the fibres in the inner band 19 are longer than the fibres in the intermediate band 21 which in turn are longer than the fibres in the outer band 23, as illustrated in Fig. 2 of the drawings. Because of the outwardly sloping nature of the fibres and the centri¬ fugal and loading forces exerted on the fibres during operation of the brush, the degree of slope of the fibres

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increases in the outward direction and thereby longer fibres overlay shorter neighbouring fibres. As explained hereinbefore, this•has- a- detrimental effect-on -the .pe-rfor-, mance of the brush.

Referring now to Fig. 3 of the drawings, the rotary brush 30 according to the embodiment includes a circular base 31 from one face 33 of which projects a plurality of fibres 35. The fibres are grouped into tufts 36 which in turn are grouped into three bands; namely, an inner band 37 an intermediate band 39 and an outer band 41. The fibres in the inner band 37 and intermediate band 39 slope inwardly towards the centre of the brush while the fibres in the outer band 41 slope outwardly away from the centre of the brush. The fibres in each band are of uniform abrasive characteristics, but the abrasive characteristics of the fibres vary from band to band. Specifically, the abrasive characteristics are highest for the fibres in the inner band 37 and lowest for the fibres in the outer band 41.

A typical inclination for the inwardly sloping fibres is 20° from a line perpendicular to the plane of the face 33 of the base of the brush. The inward slope of the fibres is such that the angle of inclination is maintained throughout the life of the brush due to the weight of the . machine and rotational speed of the brush. In this way, there is no significant change in the performance charac¬ teristics of the brush during its working life.

The free ends of the fibres 35 are trimmed so as to define a working surface which diverges from the face 33 of the base of the brush in the direction towards the centre of the brush. A typical slope for the working surface of the brush is 1:16. The trim of the fibres simulates the wear pattern which would later become apparent on the fibres.

This assists in providing the brush with performance characteristics which do not vary significantly during the operating- -ϋ-fe--of— he--brush.- -■ - -.--...._. _...

Although the invention has been described in relation to one specific embodiment, it is not limited thereto and various alternations and modifications may be made without departing from the scope of the invention. The invention may, for instance, be applied to rotary brushes other than floor maintenance brushes.