The present invention relates generally to castors and more particularly to free floating castors.
The state of the art castors, as we are all aware, are wheels that trail the direction of motion of the platform or trolley onto which they are mounted. The wheel in the castor assembly has freedom to revolve, in the horizontal plane, around the vertical axis of the castor assembly, through 360.degree.. The wheel being located at a certain distance (trail distance) from the single vertical axis of the assembly at the end of a trail arm makes the wheel follow the direction of the motion of the trolley.
Standard castors have two inherent flaws--one, the castors have a tendency to get wedged, and two, swiveling/fishtailing of the trolley onto which the castors are fitted when the direction of motion is reversed.
Wedging is a momentary restriction in the smooth motion of a castor trolley experienced during reversal of direction of its travel. While reversing the direction of motion, the castor becomes dynamically unstable. The wheel initially follows the reverse path and then deviates. During this process, the castors have to revolve to re-align. The castors could either revolve in the same or opposite directions. Wedging occurs when both castors revolve either inwards or outwards, i.e., in opposite directions. During the reversal motion, the wheels get dragged momentarily until they realign. In order to overcome wedging, extra effort needs to be applied which will be proportional to the weight on the wheels. This difficulty would, in day-to-day life, have been experienced while handling baggage trolleys at airports, etc.
Fishtailing of the trolley also occurs while reversing. Owing to the revolving action, the castors could revolve in the direction opposite to the intended one. For instance, while reversing the direction from forward to rearward, the castors could revolve in clockwise direction. Thereby, the trolley will swing towards the right hand side. In case of an obstruction ahead and in order to avoid it, one needs to apply additional force to turn left. However, on doing so, one finds a momentary resistance to the effort because the castors are revolving in the wrong direction. By continuing to pull backwards, one could hit the obstacle. The way out would be to push forward again, make the castors revolve in the opposite direction and then pull back or apply enough force to drag the wheels in the desired direction.