1. Field of the Invention
This invention relates to conveying apparatus in which a carriage imparted with a propelling force by a linear motor or the like motive means is run under its inertia along guide rails.
2. Description of the Prior Arts
In a conventional convertion conveying system, the carriage is generally driven by a drive source mounted thereon for running along a predetermined conveying path. With such conveying system, however, due to the installation of the drive source, the size and weight of the carriage is increased.
Accordingly, when the carriage runs very fast, there arise problems such that a large centrifugal force is generated at a curved path and energy supply becomes required.
On the other hand, there has been proposed a conveying system in which the carriage is not provided with a drive source but imparted with a propelling force from outside thus running the carriage with its own inertia. For example, in a conveying system utilizing a linear induction motor, the carriage is provided with a reaction plate which is supplied with magnetic flux varying with time so as to create in the reaction plate a definite forward or reverse propelling force thereby running or stopping the carriage. This system can miniaturize the carriage, can reduce its weight and can run the carriage at a high speed.
When conveying an object by means of a conveying system driven by a linear motor, if it is possible to convey the object, not only in the horizontal direction but also in the vertical direction, it would be possible to provide a three dimensional conveying system efficiently utilizing the space.
A prior art system enabling three dimensional conveyance is disclosed in Japanese Patent Application No. 102589/1978 (Japanese Laid Open Patent Specification No. 30726/1980). According to the conveying system disclosed therein, since guide members for limiting the transverse movement of the carriage are provided for the lower surface of the carriage, the guide rails for guiding the carriage and the carriage itself become large and complicated so that it is impossible to decrease the size of the conveying system while ensuring a desired capacity of transportation.
Further, when running three dimensionally, the carriage should be restricted in upward movement by upper guide rails. However, since the carriage is provided with only one pair of wheels vertically, there occurs great frictional force between the wheels and the upper guide rail due to the reverse rotation of the wheels. (This Japanese Patent Application does not disclose the three-dimensional running case.)