The present invention relates to sports balls and, in particular, to golf and tennis balls. However, the Invention 1s not limited to balls used 1n these two particular sports.

5 BACKGROUNDART

There has long been a need for a mechanism which enables essentially outdoor games such as golf and tennis to be played for greater lengths of time in order to best utilize the capital cost of the outdoor playing facilities. This requires that twilight and/or night

10 time use of such facilities be possible. One proposal for such extended playing times 1s contained 1n the specification of International Patent Application No. PCT/AU88/00324 published under no. WO 89/018101n which a playing surface having luminescent portions is used and the playing area 1s Illuminated with ultraviolet light.

15 It is also known from Australian Patent No. 533145 (previously Application No. 10219/83) to provide for a golf ball with a fluorescent cover, the fluorescent pigments and dyes used 1n the cover being commercial products available from the Dayglo Color Corporation of the USA or Lawter Chemical Co of Skokie, Illinois, USA.

20 However, It has been determined in practice that fluorescent balls are not sufficiently visible after dark on a golf course, for example, because the intensity of radiation from the ultraviolet light sources 1s relatively low. Accordingly, the intensity of the re-emitted visible radiation from the fluorescent balls Is also low.

25 It 1s also known to use a golf ball (manufactured by PICK POINT SPORTS of Florida, USA) with a stick or rod of two chemical materials separated by a frangible portion which, after being subjected to a predetermined bending, breaks allowing the two chemicals to mix thereby emitting light. Such materials are sold under the registered trade mark

30 CYALUME of American Cyanamid Company of Bound Brook NJ USA. This stick or rod 1s inserted into the ball along a centrally aligned hole, however, this ball suffers from the disadvantage that 1t does not behave mechanically or aerodynamically like a conventional golf ball. It 1s jf also relatively expensive since the emitted light lasts only 4 hours and

35 then the stick (which costs approximately AS2.00) must be discarded.

In order to overcome these problems, 1t has been proposed to use a golf ball painted with a phosphorescent paint. Such a ball can be "charged" by being strongly irradiated with radiation and which therefore

emits visible radiation for a relatively lengthy time during which the intensity of the emitted radiation decays. However, such painted phosphorescent balls suffered from the problem that they were "scuffed" during use. As a consequence a dark patch appeared at the location of the various hits and the illumination Intensity was rapidly reduced. Thus these balls did not emit sufficient light for a sufficient length of time to be of any practical use. In particular, these balls were uneconomic since experience indicated that after one game of golf the ball was not able to be used for night time play. The object of the present invention is to provide a phosphorescent ball which provides an adequate optical performance and so can be used for outdoor sports at night time over a reasonable length of time, for example, at least several games..

SUMMARYOFTHEINVENTION According to one aspect of the present Invention there 1s disclosed a phosphorescent ball for night time sporting and leisure activities, said ball comprising plastics to which during manufacture a phosphorescent pigment has been added. The adding can be by way of impregnation or dyeing. PREFERREDEMBODIMENTS

Preferred embodiments of the present Invention will now be described with reference to the following examples.

EXAMPLE1 The first embodiment of the phosphorescent golf ball has an overall weight of 46.5 gm (1.64 ozs) and overall diameter of 4.27 cm (1.68 inches). The ball has a substantially conventional centre or core with a weight of 35.5 gm (1.25 ozs) and diameter of 3.81 cm (1.5 inches). The cover accordingly has a weight of 11 gm (0.39 ozs) and thickness of 0.23 cm (0.09 Inches) and it 1s formed from a blend of ionomer polymers Including poly (ethylene-co-methacrylic add) and those sold by Du Pont under the name SURLYN.

To the cover material is added a phosphorescent pigment having a weight of approximately 4 g (0.14 ozs). Accordingly, the range of the pigment concentration in the cover material is from approximately 107. to approximately 50%, and preferably 257.-35%, by weight.

The preferred pigment is sold in Australia under the name LUMI-GSS by LEPCHEM AUSTRALIA PTY LIMITED and comprises phosphorescent zinc

sulphlde (ZnS:Cu) crystals. A combination of phosphorescent pigments 1s able to be used provided the total weight of the pigment 1s 1n accordance with the above.

In addition, one or more clear coats can be added to the ball over the cover material. The preferred form of Inner clear coat 1s clear epoxy resin and the preferred form of outer clear coat is clear urethane. Best results were achieved 1f no optical brlghteners were present in the clear coats. Any Indicia can be applied to the ball between these two clear coats. EXAMPLE2

Early experiments Indicated that pigment concentrations below about 5% were entirely unsatisfactory since the glow duration was too short. In addition blotchy and uneven light effects were produced 1f scrap cover material was re-ground and added to the cover material during fabrication. In order to overcome this problem, the ball as described 1n Example 1 was fabricated and virgin cover material at the appropriate pigment concentration was used. For subsequent batches scrap pigmented cover material could then be used without deleterious effect.

Furthermore, because of the weight of the pigment, the mass of the centre or core had to be reduced but the volume maintained. This problem was solved by the use of less dense fillers.

EXAMPLE3 Conventional inner cores for golf balls are of various colours such as pink, blue and grey. Since the colour of a conventional golf ball 1s determined by Its outer cover which is both coloured and opaque, the colour of the Inner core is Irrelevant. It has been found that the optical performance of the balls of both Example 1 and 2 can be enhanced by Increasing the reflectivity of the inner core. Improved results are obtained with a white, preferably brilliant white, inner core. Chrome plating to a mirror finish also is useful. The difference caused by the reflective Inner core is only just discernable under normal light conditions, however, the difference in emitted light under no or low light conditions Is quite marked.

EXAMPLE4 The abovementioned phosphorescent pigments take the form of a crystalline powder. The balls of Examples 1-3 where made by blending the ionomer and pigment together in a mill. The pigment crystals were added

-4- to the thermoplastic material which was softened by friction from the mill. After this mixing the material was allowed to cool and then was granulated. These granules were then placed In the injection moulding machine. Although this produced an acceptable result, a much Improved result was obtained by separately but simultaneously feeding the pigment and the ionomer Into the screw feed of the Injection moulding machine.

EXAMPLE5 Any of the above described balls can also be provided with an additional phosphorescent layer. This 1s achieved by adding phosphorescent pigment to the Inner clear coat of epoxy resin at a concentration of 10%-50% by weight. In this way any "scuffing" of the ball which does occur through use, does not result 1n a dark patch but Instead results in a patch which 1s substantially equally phosphorescent as its surroundings.

EXAMPLE6 The preferred embodiment of a tennis ball has a conventional elastomeric hollow interior which 1s provided with an outer cover made from fibrous material. The preferred material for the outer cover is a felt blend of 60% wool and 40% nylon by weight. The phosphorescent pigment is either attached to, or located within, the nylon during or before the fabrication of the nylon fibres. The pigment can also be attached to the wool fibres by, for example dyeing. A concentration of 20% by weight of the abovementioned phosphorescent plgment(s) was used. EXAMPLE7

A tennis ball having the conventional elastomeric hollow interior was made as in Example 6. However, the outer cover was made from felt having a 40% wool 60% nylon by weight composition. The range of felt compositions extends from 20% wool 80% nylon to 80% wool 20% nylon by weight.

It has been determined that the balls of the abovementioned examples are able to stand repeated use to at least approach the use periods of conventional balls. Accordingly, the economic cost of such balls is not prohibitive. The foregoing describes only some embodiments of the present invention and modifications, obvious to those skilled in the art, can be made thereto without departing from the scope of the present invention.