Transfer mechanism

Transfer mechanism

I) Linear transfer mechanisms:

We will explain the operation of three of the typical mechanisms: the walking beam transfer bar system, the powered roller conveyor system, and the chain-drive conveyor system.

This is not a complete listing of all types, but it is a representative sample.

Walking beam systems: With the walking beam transfer mechanism, the work parts are lifted up from their workstation locations by a transfer bar and moved one position ahead to the next station. The transfer bar then lowers the parts into nests which position them more accurately for processing. This type of transfer device is illustrated in Figure powered roller conveyor system. This type of system is used in general stock handling systems as well as in automated flow lines. The conveyor can be used to move pans or pallets possessing flat riding surfaces the rollers can be powered by either of two mechanisms. The first is a belt drive, in which a flat moving belt beneath the rollers provides the rotation of the rollers by friction. A chain drive is the second common mechanism used to power the rollers. Powered roller conveyors are versatile transfer systems because they can be used to divert work pallets into workstations or alternate tracks. We discuss roller conveyor systems.

Fig: Walking Beam transfer system. Showing various stages during transfer cycle

Chain-drive conveyor system

Figure illustrates this type of transfer system. Either a chain or a flexible steel belt is used to transport the work carriers. The chain is driven by pulleys in either an over and under configuration, in which the pulleys turn about a horizontal axis, or around the corner configuration, in which the pulleys rotate about a vertical axis. This general type of transfer system can be used for continuous, intermittent, or non synchronous movement of work parts. In the no synchronous motion, the work parts are pulled by friction or ride on an oil film along a track with the chain or belt providing the movement. It is necessary to provide some sort of final location for the work parts when they arrive at their respective stations.

Fig: Chain - Driven Conveyor, “Over and under" type.

II) Rotary transfer mechanisms:-

There are several methods used to index a circular table or dial at various equal angular positions corresponding to workstation locations. Those described below are meant to be a representative rather than a complete listing.

Fig: rack and pinion mechanism for rotary indexing table

Rack and Pinion: This mechanism is simple but is not considered especially suited to the high-speed operation often associated with indexing machines. The device is pictured in Figure and uses a piston to drive the rack, which causes the pinion gear and attached indexing table to rotate. A clutch or other device is used to provide rotation in the desired direction.

Ratchet and Pawl: This drive mechanism is shown in Figure. Its operation is simple but somewhat unreliable, owing to wear and sticking of several of the components.

Geneva Mechanism: The two previous mechanisms convert a linear motion into a rotational motion. The Geneva mechanism uses a continuously rotating driver to index the table, as pictured in Figure. If the driven member has six slots for a six-station dial indexing machine, each turn of the driver will cause the table to advance one-sixth of a turn. The driver only causes movement of the table through a portion of its rotation. For a six-slotted driven member, 120° of a complete rotation of the driver is used to index the table. The other 240° is dwell. For a four slotted driven member, the ratio would be 90° for index and 270° for dwell. The usual number of indexing per revolution of the table is four, five, six, and eight.

CAM MECHANlSMS. Various forms of cam mechanism, an example of which is illustrated in Figure 4.9, provide probably the most accurate and reliable method of indexing the dial. They are in widespread use in industry despite the fact that the cost is relatively high compared to alternative mechanisms. The cam can be designed to give a variety of velocity and dwell characteristics.




Application of automation include the following:

1. numerical control

2. Automated production lines

3. Automated assembly

4. Robots in manufacturing.

5. Flexible manufacturing systems.

6. Building automation systems

7. Building automation system.(BAS)

8. CAD/CAM and computer integrated manufacturing (CIM).

9. Automated in daily life.