The trolley in the transport system contains a dish for holding the load. A compression plate is mounted underneath the dish and there are four springs fitted between the dish and the plate. Four guide shafts run through the dish, the plate, and the buffer, and on to the frame at the bottom of the trolley. They are there to stabilize the dish and plate during operation. Here is a front view of the trolley as seen from Bay 2. This image shows the BPS (belt-pulley system), the compression plate along with both sets of springs - the plate springs and the buffer springs - and the load. Pins at the dish and plate are also shown. These are manually operated pins used to operate the transport system.
A rack is vertically attached underneath the compression plate that carries the load; it is pushed up and down by the compression plate. The rack is supported by a linear guide and bearings, which are attached to the side panels by mounting bars. The rack drives a pinion mounted on a crankshaft, which is attached to two side panels. The pinion meshes with the moving rack and rotates. The pinion drives the crankshaft to rotate it as well.
The size of the pinion compared to the rack (number of teeth) determines the gear ratio. The ratio affects the amount of force required to move the rack and the resulting movement of the belt, pulleys and the wheel.
Note: If a compression plate gear reduction system is employed, a small vertical movement of the rack translates to a large number of rotations of the wheel.
A pulley mounted on the pinion shaft drives a belt, which in turn drives another pulley mounted on the wheel shaft at the bottom of the trolley. Here is another view of the belt-pulley system (BPS) in relation to the rack and pinion. The BPS is a continuously variable transmission (CVT) - also known as a mechanical variator [Source: Wikipedia]. The CVT uses a V-belt which runs between two variable-diameter pulleys. The pulleys consist of two cone-shaped halves that move together and apart. The V-belt runs between these two halves, so the effective diameter of the pulley is dependent on the distance between the two halves of the pulley. The V-shaped cross-section of the belt causes it to ride higher on one pulley and lower on the other; therefore, the gear ratio is adjusted by moving the two sheaves of one pulley closer together and the two sheaves of the other pulley farther apart.
The CVT output speed will remain constant regardless of the input load and therefore the input speed, as the variable pulley diameters ensure continuous speed adjustment depending on the load on the BPS.
The pulley halves are moved apart and brought together by springs.
Spring Action: The springs are designed to respond to the tension in the belt. When the belt experiences increased tension (due to acceleration), the springs compress, which can pull the pulley halves closer together. Conversely, when the belt tension decreases (during deceleration), the springs can expand, allowing the pulley halves to move apart.
Effect on Belt Motion:
Narrowing the Pulleys: When the pulleys are narrowed (due to spring compression), the belt rides higher on the conical surface. This effectively reduces the diameter, allowing for a lower gear ratio, which helps maintain a constant speed at the output.
Widening the Pulleys: When the pulleys widen (due to spring expansion), the belt rides lower on the conical surface, increasing the diameter. This allows for a higher gear ratio, compensating for reduced input speed.
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