1 SELF RIGHTING WALKING AID This invention relates to a walking aid that is convenient to use and remains upright when not held. BACKGROUND TO THE INVENTION 5 Walking sticks are useful for people who have difficulty walking and keeping their balance. However conventional walking aids are not self-supporting and when they are not in use cannot be easily reached especially if they have been dropped. Walking sticks have been the subject of a number of prior patents. Some of them, such as USA application 2007/0023072, address the problem by retaining them on 10 the arm of the invalid similar to crutches. USA application 2006/0099783 discloses a multi-function stick but fails to address the issue of retrieving the stick if is dropped. USA patent 3392946 discloses a self-standing attachment for umbrellas or walking sticks that has an extended and a retracted position. It would be be difficult for a 15 person with poor balance to open up the stand and it would be difficult to walk with it in the opened position. WO 2010/001426 discloses a similar device. European patent 661010 discloses a self-righting walk stick with a curved base. This is a large and cumbersome appendage that is inconvenient to use. French patent 2668690 discloses an attachment for the end of a walking stick that 20 provides a flat base so that it can stand alone. However the stick in its upright position can easily be knocked over creating a problem for a user with poor balance. It is an object of this invention to provide a walking stick that ameliorates the problems identified in the prior art sticks. 25 BRIEF DESCRIPTION OF THE INVENTION To this end the present invention provides a walking stick which includes a shaft an axially symmetrical handle attachable at one end of the shaft 30 an axially symmetrical base attachable to said shaft, said base having an area several multiples of the cross sectional area of the shaft 2 cushioning material disposed on the edges and underneath surface of said base and a domed protrusion on the underneath surface of said base in axial alignment with said shaft 5 Stability in the stand alone walking stick of this invention is achieved by providing a wide weighted base with a self- righting part spherical base. The shaft may be adjusted in length to cater for different user heights and preferably the handle also comes in several sizes more preferably two sizes. The base may be varied in weight or additional weights added to the base to lower the centre of gravity. 10 DETAILED DESCRIPTION OF THE INVENTION A preferred embodiment of the invention will be described with reference to the drawings in which Figure 1 is a side view of the walking stick of this invention 15 Figure 2 is a section view of figure 1 with details of the handle and the base Figure 3 is an exploded view of the components of the walking stick. The shaft 7 is attachable to the spherical handle 15 by threaded engagement. The handle 15 may be provided in various sizes 50mm,55mm and 60 mm for different 20 sized hands. The handle 15 is attached to the shaft using a handle support 13 which fits about the base of handle 15 to stabilise the handle 15 from sideways bending. A threaded rod 10 screws into the ball handle 15 and is fastened by the pin 12. The rod 10 and ball handle when fastened together connect to the disc 9 by screwing the rod into 25 the internal thread of disc 9. The support disc 9 is fastened inside the shaft 7 and held in place by the pin 11. The handle support 13 slides onto the shaft 7 and a groove in the narrow end of 13 fits onto and secures pin 11. The handle is preferably ball shaped and may be of any suitable durable material. Preferably the handle is night time visible and this may be achieved by a small dab 30 of glow paint inside the ball handle.
3 The shaft 7 may be extended in length by spacer 8 (using 1 or 2 spacers of this same type) and spacer 6 is fixed to shaft 7 by pin 14. The spacers may be attached to either end but in this embodiment are attached to the bottom end to extend the length. Preferably 2 spacers of type 8 are available in the product pack to extend 5 the length but the spacer 6 is preferably fixed and stays fixed because its primary function is as a connection between shaft and spacer type 8. The base of the stick consists of an upper flared base 2 that includes a central cylindrical passage for the tubular shaft 7. Attached to the bottom of the flared base 2 is the lower base threaded grip 1. Two base weights 3 are held in place in the 10 against base part 1 by the screw fastener 16. The base part 1 also secures the rubber base rim 4 in place . The domed rubber centre base 5 is attached to the base part 1 and protrudes beyond the lower surface formed by the rubber rim 4. The base part 2 is shown in the drawings to have a concave upper surface but this may be any appropriate shape such as a straight or convex from where the upper 15 surface starts to flare extending out to the edge of the flare or the rim of part 2. These latter shapes are preferred because they are less likely to catch on stairs. The outer surface of the flared base 2 may be provided as a separate part that may be clipped onto the base to provide a different shape or colour to the base. 20 The construction has a low centre of mass because of the weights 3 and the curved protrusion 5 allows the walking stick to oscillate about the vertical if knocked. The width of the rubber rim 4, its shock absorbing properties and the low centre of mass means that it is difficult to knock this self-supporting walking stick over. 25 Those skilled in the art will realise that this invention provides a unique walking stick that provides security and convenience to those with a poor balance. Those skilled in the art will also realise that this invention may be implemented in embodiments other than those illustrated without departing from the core teachings of this invention. 30