Source: {"pile_set_name": "USPTO Backgrounds"}

Track lighting systems are well known. The systems typically comprise a track which is mounted to the ceiling or wall and which is connected to an electrical supply source. The track is a hollow, elongated extrusion having neutral and voltage busses mounted within the track and running the length thereof. One or more lighting fixtures are sidably mounted to the track such that they can be moved to desired locations along the length of the track. Each lighting fixture is coupled to the track--both mechanically and electrically--by means of a track adapter. The track adapter includes neutral and voltage electrical contacts which are disposed to conductively communicate with the voltage and neutral electrical busses in the track. In addition the track adapter includes a ground contact which either engages a ground bus running the length of the track or contacts the track extrusion to ground the circuit. Thus the track adapter electrically connects the associated light fixture to the source of electrical power.
A variation on standard track lighting is the dual circuit track lighting system. In this arrangement two separate voltage busses are mounted within the track and run the length thereof. The ground and neutral contacts of the track adapter are fixed in position, but the voltage contact is movable with respect to the track adapter between a first position in which the voltage contact electrically couples to the first voltage bus of the track, and a second position in which the voltage contact electrically couples to the second voltage bus. By selectively mounting the lighting fixtures to contact either the first or second circuit, it is possible for one track light to be operated independently of a second track light mounted to the same track.
Conventional track adapters for dual circuit track lighting systems rely on frictional engagement between the voltage electrical contact and a corresponding slot in the track adapter to maintain the voltage contact in its first or second position. This arrangement is problematic, however, in that too much frictional engagement will make the voltage contact difficult to move between its first and second positions, while too little frictional engagement will permit the voltage contact to move unintentionally from one position to the other, or even to an intermediate position in which the voltage contact fails to contact either voltage bus.
Consequently there is a need for a track adapter for dual circuit track lighting systems which includes a mechanism for affirmatively maintaining the voltage contact in its desired position while permitting easy movement of the voltage contact between its two positions. There is a further need for a track adapter for dual circuit track lighting systems which reduces the likelihood that the voltage contact will be placed in an intermediate position in which the voltage contact fails to contact either voltage bus.