In WO 96/31713 is disclosed a differential gear comprising an input member constituting a cage for rolling means and having drive input means and being mounted for rotation about an output axis comprising half shafts either side of the input member, each half shaft having a clutch plate, the clutch plates being disposed either side of the input member and being urgeable together so as to clutch against said rolling means, whereby a differential output effect is achieved by the clutch plates rolling over the rolling means.

The clutch arrangement in such a gear requires spring means, e.g. belleville washers urging the plates together with the rolling means, and high contact pressures are required which in turn requires a certain surface hardness specification which can be expensive and demanding in terms of quality control.

The present invention provides a differential gear that is less expensive and easier to manufacture.

The invention comprises a differential gear comprising an input member mounted for rotation with respect to output half shafts each fixedly carrying an output member and coupling means coupling the input differentially to the output members said coupling means comprising at least one coupling member mounted, in a throughway of the input member to extend from it towards the output members, for rotation about an axis radial of the half shafts and positively engaging the output members, rotation of said coupling member about its axis of rotation permitting relative rotation of the output members on their half shafts.

The input member many comprise a circular disc and said throughway comprises a chordal slot. Said chordal slot may include a bearing arrangement for the coupling member. Said bearing arrangement may comprise a bore adapted to receive a pin on which the coupling member rotates. Said bore may be drilled in from the periphery of said input member, or moulded from one side.

The coupling member may comprise a toothed wheel the teeth of which engage in complementary recesses in the output member. The recesses may comprise throughways or indentations.

The input member may be adapted to be driven peripherally, as by comprising a worm wheel.

One embodiment of a differential gear according to the invention will now be described with reference to the accompanying drawings, in which:- Figure 1 is a half axial section; Figure 2 is a section on the line II-II of Figure 2; and Figure 3 is a part cut-away partial view on Arrow 3 of Figure 1.

The drawings illustrate a differential gear comprising an input member 11 mounted for rotation with respect to output half shafts 12, 13 each fixedly carrying an output member 14, 15 and coupling means 16 coupling the input member 11 differentially to the output members 14, 15 said coupling means 16 comprising at least one coupling member 17 mounted, in a throughway 18 of the input member 11 to extend from it towards the output members, for rotation about an axis radial of the half shafts 12, 13 and positively engaging the output members 14, 15 rotation of said coupling member 17 about its axis of rotation permitting relative rotation of the output members 14, 15 on their half shafts 12, 13.

The input member 11 comprises a circular disc, which may be of metal or plastics material, and said throughway 18 comprises a chordal slot, which may be cast or moulded in or machined out.

Said chordal slot 18 includes a bearing arrangement 19 for the coupling member 17, said bearing arrangement 19 comprising a bore 21 adapted to receive a pin 22 on which the coupling member 17 rotates. The bore 21 is drilled in from the periphery 23 of the input member 11. If, as is possible, the input member disc 11 is moulded, a slot may be moulded in from one face to receive the pin 22 which is essentially captive after assembly.

The coupling member 17 comprises a toothed wheel the teeth 17a of which engage in complementary recesses 17b in the output members 14, 15. The recesses 17b comprise throughways or indentations - they may be cast or moulded in or machined out.

The input member 11 is adapted to be driven peripherally, as by a worm wheel.

The gear is robust and simple to manufacture. As there is positive engagement, there is no need to maintain contact pressure sufficient to ensure non-slip operation. So, in turn, there is no demanding surface hardness specification which simplifies the manufacturing process. Assembly of the components is straightforward.

The gear is compact and can be accommodated within a gear box. For low speed applications, balance is not a problem and a single coupling member can suffice.

The engagement is at a distance from the half shafts and the resulting mechanical advantage reduces the forces so that the coupling member itself need not be robust - a steel pressing or stamping even a plastic moulding may be found adequate.

The teeth of the coupling member can be of any shape found satisfactory for positive engagement.

The gear is useful in connection with golf trollies, but will clearly find application in many other drive trains.