1. Field of the Invention
The present invention relates to a driving force transmission switching apparatus and, more particularly, to a driving force transmission switching apparatus for switching among objects to which a driving force is transmitted.
2. Description of the Related Art
In recent years, cameras have been equipped with a variety of driven devices such as film feeding devices, lens moving devices, or the like. There have been various attempts to drive these diverse driven devices with a single drive source, e.g., a single motor, in order to meet a demand for reduced sizes, lower cost, etc. For instance, Japanese Unexamined Patent Publication No. 5-321986 discloses a driving force transmission switching system equipped with a single motor and designed to drive a plurality of driven devices as mentioned above by appropriately switching among driven devices to which the driving force of the motor is transmitted, by using a planetary gear assembly. More specifically, the driving force transmission switching system revolves a planetary gear by running the motor in one direction to select a driven gear associated with a device to be driven. After selecting the driven gear, the motor is run in the other direction to transmit a driving force to the driven device via the driven gear.
However, the driving force switching system proposed in Japanese Unexamined Patent Publication No. 5-321986 requires a space for the planetary gear to revolve. Furthermore, if there are a plurality of devices to be driven and are located away from each other, then many gears are required, thus involving a large wasteful space.
Japanese Unexamined Patent Publication No. 5-257195 discloses a driving force transmission switching apparatus provided with two driven assemblies, wherein, while one of them is being driven, the other remains locked. This, only satisfies an application wherein driven assemblies have only two states and has been inapplicable to a driving force transmission switching apparatus equipped with three or more driven assemblies.
None of the aforementioned, taken alone or in combination, teach or suggest the present invention.
A first object of the present invention is to provide a driving force transmission switching apparatus that is small and yet capable of switching among a plurality of objects to which a driving force is transmitted.
A second object of the present invention is to provide a driving force transmission switching apparatus capable of reliably retaining a driven assembly in a halted state even when not in engagement with a driving assembly.
To these ends, according to the present invention, there is provided a driving force transmission switching apparatus for a camera, which is equipped with:
a drive source that generates a driving force;
a worm gear that receives the driving force to rotate;
a driving force transmission gear device that includes a driving gear and meshes the driving gear with the worm gear to move the driving gear parallel with an axial direction of the worm gear as the worm gear rotates so as to shift the driving gear to a plurality of transmission positions far applying a driving force of the drive source and a non-transmission position when not applying the driving force of the drive source;
a plurality of driven gears which are disposed in positions for meshing with the driving gear, respectively corresponding to the plurality of transmission positions where the driving gear is positioned, and which receive a driving force of the drive source via the driving gear; and
a position control device for meshing the driving force transmission gear device with the worm gear to move the driving force transmission gear device parallel with the axial direction of the worm gear as the worm gear rotates so as to shift the driving force transmission gear device to the plurality of transmission positions for applying a driving force of the drive source and a non-transmission position when not applying the driving force of the drive source.
These objects and advantages of the present invention will become further apparent from the following detailed explanation.