This invention relates to dental floss.

It is known to manufacture dental floss by extruding nylon material and thereafter processing the material in an appropriate manner, for example to coat it with various binders and/or active ingredients. Such dental floss is useful in removing residual food and plaque from spacings between teeth. However, the interproximal spacings are of different sizes and this requires dental floss also to be of different sizes.

It is an object of this invention to obviate and/or mitigate this disadvantage.

According to one aspect of this invention there is provided a dental floss comprising a plurality of threads knitted together to define an elongate cord.

The threads are preferably knitted together by constructing loops and whales around a plurality of needles, the needles being arranged in substantially circular configuration about an aperture to which the knitted cord is delivered after each pass of the threads around the needles.

In one embodiment of this invention, the threads

comprise a plurality of threads of an elastic material, and at least one thread of a non-elastic material capable of providing a wiping effect over the teeth.

The cord conveniently comprises five threads of a said elastic material, and one thread of said non-elastic material. The elastic material may be spandex, for example as sold under the Trade Mark L.YCRA. The non-elastic material may be nylon, or formed of polyethylene preferably ultra high molecular weight polyethylene (UHMW-PE) , for example as sold under the Trade Mark DYNEEMA.

According to another aspect of this invention, there is provided a method of forming a dental floss comprising knitting together a plurality of threads to define a cord .

Preferably, the threads are knitted together by constructing loops and whales around a plurality of needles in a plurality of passes of the threads around the needles to form the cord, whereby after each pass, the cord so formed is delivered through an aperture arranged centrally of the needles. Preferably, the threads are knitted around four, six or eight needles.

Conveniently, at least some of the threads are of an elastic material, and at least one of the threads may be of a non-elastic material. In one embodiment of the invention, five threads are of an elastic material, and one thread is of a non-elastic material.

An embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which:-

Fig. 1 is a schematic plan view of threads knitted together to form a dental floss: and

Fig. 2 is an arrangement of needles for forming the floss shown in Fig. 1 ; and

Fig. 3 is a view of alternative arrangements of needles for forming dental floss.

Referring to the drawings, Fig. 1 shows schematically a dental floss 1 comprising a knitted arrangement of threads 1 OA , 1 OB , 1 OC , 1 OD , 1 OE and 10F which are knitted into each other to form the dental floss 1 which is in the form of a tubular cord. Although, the embodiment shown uses six threads, it will be appreciated that any appropriate number of threads could be used.

Threads 1 OA , 1 OB , 1 OC , 1 OE and 10F are formed of a suitable elastic material, and may be spandex, for example as sold under the Trade Mark LYCRA and, can be stretched in their lengthwise direction. The thread 10D is formed of a suitable non-elastic material, for example nylon or a polyethylene thread, such as that sold under the Trade Mark DYNEEMA.

Fig. 1 shows schematically a portion of the floss 1. It will be appreciated that referring to Figs. 2 and 3 that the floss 1 is tubular in configuration. As shown in Fig. 1 , the threads 10A to 10F appear to have respective opposite ends 12A to 12F and 14A to 14F. Similarly, thread 10A'shown in dotted lines appears to have opposite ends 12A'and 14A.' In view of the fact that the construction of the floss 1 is tubular in configuration, the thread 10A continues at the end 14A as the end 12A'of thread 10A.' Similarly, the thread 10B continues as the thread 10B.' The other threads 10C to 10F are also continued so that an elongate tube of the floss 1 is formed. Thus the floss is configured as if the threads 10A to 10F are wound around an axis X-X extending longitudinally thereof. As indicated above, Fig. 1 shows schematically an only portion of the floss 1. It will be appreciated that the floss 1 would continue above and below the portion shown for as long as

de s i r e d .

Referring to Fig. 2, there is shown a top plan view of apparatus 11 for use in knitting a dental floss 1. The apparatus 11 comprises a circular bobbin 20 to which are affixed four pins or needles 22,24,26,28. The apparatus is suitable for use with a known form of knitting known as "french knitting" or "circular knitting". In essence, the knitting involves winding the threads in turn around the outside of the needles 22 to 28 and then lifting the previous threads wound around the needles over the thread just wound and delivering the previously wound thread into the aperture 30.

The commencement of the knitting procedure will not be described since this would be known by persons skilled in the art. Fig. 2 shows a stage after some of the floss 1 has already been knitted and delivered into the aperture 30. As can be seen from Fig. 2, the threads 10F are wound around the individual needles 22 to 28 and are supporting the floss 1 which is hanging therefrom in the aperture 30. The next stage in the procedure is for the thread 10A to be wound around the outside of the needles 22 to 28 and then the threads 10F around the needles 22 to 28 is then lifted over the thread 10A wound around the needles 22 to 28 and delivered into the aperture 30.

After this has been done, process would be repeated with the thread 10A and thereafter with the other threads 10B to 10F in succession. The process would then continue until a desired length of dental floss 1 is formed through the aperture 30.

Various modifications can be made without departing from the scope of the invention for example, the arrangement of the needles and the number of threads and the loop formation can be varied, for example to that shown in Fig. 3 which shows possible other arrangements of needles and threads to form a dental floss. By varying the loop formation, the tension of the thread can be varied to vary the properties of the floss.

Referring to Fig. 3, there is shown various arrangements of needles for forming tubular cords having different knitting patterns. The number of needles and threads can vary from two to ten. The knitting patterns can also be varied for each different number of needles, as shown, by varying which needles the threads are wound around. The top pattern in Fig. 3 shows the use of three needles 32,34,36 around which three threads 10A,B, C are wound. In this embodiment, two elastic threads 10A,10B, and one non-elastic thread 10C are used. The skilled person will appreciate the operation of the other

patterns shown in Fig. 3 to enable him to manufacture cord using such patterns.

A further modification would be to vary the number of non-elastic threads to elastic threads.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon .