1. Field of the Invention
The present invention relates in general to a folding seat for a motor vehicle, which is foldable when not in use, and more particularly to a folding seat which is installed in a driver's cabin of a truck or the like for use as an extra seat.
2. Description of the Prior Art
In order to clarify the task of the present invention, one of the conventional folding seats of the above-mentioned type will be outlined with reference to FIG. 5. The seat of this drawing is commonly called "jump seat" wherein the seat cushion proper is foldable when not in use.
The seat has a seat cushion 100 which is pivotally mounted on a base structure 102 secured to a floor 104 of the driver's cabin near a rear or side wall 106 of the same. The seat cushion 100 has a supporting stay 108 pivotally hanging therefrom. The lower end of the stay 108 is slidably received in a guide rail 109 secured to the base structure 102. A spring 110 biases the stay 108 toward the seat cushion 100.
When not in use, the seat cushion 100 assumes an upright folded position as illustrated by a phantom line, placing the lower end of the stay 108 at the uppermost position of the guide rail 109. Upon requirement of use, the seat cushion 100 is pulled down from the folded position and the stay 108 is pulled against the spring 110 bringing the lower end of the stay 108 into locking engagement with a given position of the guide rail 109. With this, the seat cushion 100 is held in a horizontal in-use position as illustrated by a solid line. The wall 106 located behind the seat can serve as a backrest.
However, the above-mentioned conventional folding seat has the following drawbacks due to its inherent construction.
That is, when the seat cushion 100 assumes its folded position, the lower end of the stay 108 is displaced from the given locked position of the guide rail and thus unlocked. Thus, when the vehicle moves on a rough road or the like with the seat cushion 100 folded, the stay 108 and thus seat cushion 100 are subjected to vibration producing uncomfortable noises. One method of solving this drawback is to increase the force of the spring 110. However, as is easily understood, increasing the spring force increase the force which is needed when the seat cushion 100 is pulled down for its practical use. This induces a troublesome operation of the seat and may cause the operator get hurt in the finger.