DART SHAFTS AND A METHOD OF MANUFACTURE THEREOF

Abstract: A one-piece dart shaft (12) is produced by flattening an end portion (11), e.g. by swaging, and then stamping or punching therein a slot (20). The slot walls are shaped to receive and retain a dart flight having four vanes. The shaft (12) is preferably of steel material.

Description: I DART SHAFTSAND A METHOD OFMANUFACTURETHEREOF The present invention relates to a method of manufacturing dart shafts and to dart shafts produced by the method. The dart shafts are preferably, but not essentially, of the type disclosed in GB Patent 2019232B, which relates to a one-piece dart shaft having a slot extending generally diametrically through its thickness and terminating short of both ends of the shaft, the slot being of minimum transverse dimension in a plane containing the longitudinal axis of the shaft, and the slot walls diverging generally at right angles to one another from this minimum portion to the mouths of each slot, which mouths are located generally diametrically of the shaft, so that a one-piece flight having four vanes may be inserted laterally of the rear and the vanes may then extend radially of the shaft axis each lying against a corresponding one of said slot walls. Such dart shafts are in practice made of aluminium alloy or plastics material. Aluminium alloy has the disadvantage of being soft so that it bends with use. Plastics materials such as polycarbonate are more resilient, but after a period of use they may snap. The present invention seeks to overcome or reduce one or more of the above problems. It seeks to provide a method of providing a dart shaft of a hard and strong material which is not brittle, more particularly of steel. According to a first aspect of the present invention there is provided a method of manufacturing a dart shaft comprising producing in an elongate rod member an axially-extending through slot to receive a dart flight, the method comprising the steps of flattening a portion of the rod for a distance equal to or greater than the intended slot and then stamping or punching through the flattened portion to produce the slot. According to a second aspect of the present invention there is provided a dart shaft manufactured by a method in accordance with the first aspect. The invention also provides a dan incorporating such a dart shaft. The material of the shaft is preferably steel, e.g. carbon steel or stainless steel. The flattened portion of the rod is preferably slightly longer than the length of the finished slot, and is preferably flattened to a width approximately twice the width of the finished slot. The flattening is preferably achieved by cold forming. The stamping or punching operation is preferably effected by passing the flattened portion between a punch and a die shaped to an appropriate configuration to produce the slot length, the slot width, the slot wall form and die outside profile of the shaft in the vicinity of the slot. The operation may be performed by a machine having a plurality of dies, one of which is selected for each operation in dependence upon the dimensions and shapes required. A preferred embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, of which: Figs, la and b are end and side views of a rod or wire member from which the dan shaft is made: Figs. 2a, b and c are end and mutually perpendicular first and second side views of the flattened member; and Figs. 3a and b are top sectional and side views of the dan shaft with the slot formed therein. To manufacture the dart shaft, an appropriate material is first selected, for example a grade of steel capable of hardening and tempering. In its softened state the steel is drawn into a rod or wire 10 of an appropriate diameter "d" , straightened and cut to the desired length of the finished component. Preferred values of "d" lie within the range 0.05 to 0. 12 inches (0.127 to 0.305 cm). The wire is then flattened by cold forming over a length "1" slightly in excess of the length required for the finished slot dimension and to a width "w" approximately twice the maximum width of the finished slot. The flattened portion 1 1 of wire is now passed between a punch and die designed to an appropriate configuration to produce die slot 20 and to define the slot length "h" , slot width "s" , the slot wall form and me outside profile of the shaft in the vicinity of the slot. These shapes are preferably similar to those disclosed in GB Patent 2019232B. The dimension "h" preferably lies wid in the range of 10 to 60 mm depending on the size of the dan flight to be insened, and the dimension "s" preferably lies within the range 0.3 to 1 mm. The die stamping process does not necessarily remove any material from the rod or wire, it may simply deform it. However, during the die stamping process, rough edges are produced which can be substantially removed by clipping and rumbling or any other appropriate method. The resulting one-piece shaft 12 is then hardened and tempered, scale is removed and the final finish applied by rumbling, barrel polishing or the like. The steel surface can be protected from corrosion by electro-plating and can be decoratively coloured, e.g. by well-known staining methods, or plating with gold or chemicallv blacking. An advantage of the above method is that it comprises only relatively few steps. The complicated and costly drawing, turning, milling and grinding operations, which would otherwise be necessary, are avoided. Another advantage is that the various dimensions of me dan shaft may be freely selected at the manufacturing stage. Thus the total length of the shaft is selected by choosing an appropriate length of wire or rod member, and this in no way interferes with the tooling for making the slot. With the prior an dan shafts made of plastics material, the entire mould would need to be altered. With prior an metallic dan shafts complicated tooling arrangements would be needed to make dan shafts of different lengths. Also, die length and/or width of die slot can easily be changed to cater for dan flights of different sizes. It is simply necessary to replace the die of the stamping machine. Again this is complicated in connection with prior an arrangements. An advantage of dart shafts produced by the above method are that they are substantially hard, unbendable and unbreakable in normal use. In addition the shafts may be slender so that die chances are reduced of the shaft of a dart already in d e dartboard being struck by a subsequent dan. Various modifications may be made to the above described method. For example, during the cold forming and/or die stamping processes, identification marks can be introduced onto the shaft. Also the end 15 may be pointed or otherwise shaped so as to provide a deflection surface in the event of contact by the point of a following dan. The flattening of portion 11 may be achieved by other operations, e.g. pressing. For connection to a dan body, a shaft may be introduced to an adaptor which can be made of any appropriate materials such as thermoplastics or aluminium alloy provided with a screw d read connection for the dart body . The connection between the shaft and d e adaptor may also be screw-d readed. Alternatively a shaft may be introduced directly into die dan body provided with an appropriate female hole. In mis case both the end of die shaft itself and die hole in the dart body may be screw-direaded. The connection between an adaptor element and the shaft may be made in odier ways. e.g. by an interference fit or the shaft can be connected by use of an appropriate adhesive. Alternatively the shaft can be provided wi i a flattened section and used as an insert in a moulding so that the adaptor part of die shaft is permanendy fixed to ie shaft, die flattened section providing an interlocking mechanism and a means of preventing rotation between the shaft and the connecting pieces. In a further arrangement, a shaft and connecting piece may be arranged so that die shaft can freely rotate in the connecting piece but not become detached from it, so mat a following dan hitting a dart flight assembled into the shaft can continue on its path moving the obstructing flight out of the way by rotation. Other cross-sectional shapes may be used for the slot and die inserted flight may have more than four vanes, e.g. it might have six vanes, with four lying against the slot walls and two arranged freely therebetween. The shaft can be made of metallic or non-metallic materials other than steel if desired.

Claims: Claims: 1. A method of manufacturing a dart shaft comprising producing in an elongate rod member (10) an axially-extending through slot (20) to receive a dart flight, characterised in that die mediod comprises die steps of flattening a portion (11) of die rod for a distance equal to or greater than the intended slot and then stamping or punching through the flattened portion to produce the slot. 2. A method according to claim 1 , wherein the rod member is of steel material. 3. A method according to claim 1 or 2, wherein the portion of the rod is flattened so that it has a width (w) approximately equal to twice the widdi of the subsequendy-produced slot. 4. A mediod according to any preceding claim, wherein the slot is produced by a die-stamping operation which simultaneously determines the slot length (h), die slot widdι(s), die slot wall form and the outside profile of the shaft in the vicinity of the slot. 5. A method according to any preceding claim, wherein die slot is produced to have a minimum transverse dimension in a plane containing the longitudinal axis of the shaft, and the slot walls are formed to diverge generally at right angles to one anodier from near to the longitudinal axis to die mouths of each slot. 6. A dart shaft manufactured by a mediod in accordance with any of claims 1 to 5. 7. A one-piece dart shaft having a slot (20) extending generally diametrically through its thickness and terminating short of both ends of the shaft, die slot being of minimum transverse dimension in a plane containing the longitudinal axis of the shaft, and die slot walls diverging generally at right angles to one anodier from this minimum portion to the mouths of each slot, which mouths are located generally diametrically of die shaft, so that a one-piece flight having four vanes may be inserted laterally of die rear and die vanes may men extend radially of the shaft axis each lying against a corresponding one of said slot walls, wherein die slot is located in a flattened portion (11) of the shaft and is produced by a stamping or punching operation. 8. A dan shaft according to claim 7 of steel material. 9. A dart comprising a dart body member connected to a dart shaft in accordance with any of claims 6 to 8.

Inventors: LOWY STANLEY ROBERT, LOWY, STANLEY, ROBERT
Applicants: LOWY STANLEY ROBERT, UNICORN PRODUCTS LTD, LOWY, STANLEY, ROBERT, UNICORN PRODUCTS LIMITED
Application year: 1996
Main classification: A63B65
IPC codes: F42B6