Technical instructions Indexing mechanisms

GN 200

With these indexing mechanisms, shaft and lead screws can be turned and positioned in steps of 6 or multiples of it.

Examples of applications:

Indexing operations Lead screws which require turning and locking Positioning and locking of shut-off mechanisms, valves, etc. Control shafts (crank and cam shafts) to accurately turn and locate limited movements Securing shafts from accidental adjustments (accident prevention)

Description:

The indexing mechanism is a self-contained unit, all the adjusting and securing components are housed in the smallest possible space. The unit consists of three main parts:

Bush - can be connected to the shaft with a key or cross-dowel. Location ring - is screwed and doweled to the machine or equipment. The bush is also a bearing for the location ring. Knurled thimble - providing engagement between the locating ring and the shaft which can be turned or positioned.

In the locked position, the knurled thimble via the internal teeth (60) connects the locating ring and the bush (both via external teeth), the latter being connected to the shaft. To turn the shaft, the knurled thimble is pulled out against the spring pressure, disengaging from the location ring, but still engaged with the bush.

Other information:

With 60 teeth, the following divisions can be achieved: 2, 3, 4, 5, 6, 10, 12, 20, 30.

A simple method provides indexing of the shaft to limited number of positions only i. e. every 120.

For this purpose, the location ring is manufactured with a dowel which allows engagement only when the bush is provided with a corresponding hole (seeexample 2).

This hole can be manufactured oversize as the dowel is for rough positioning only. Accurate positioning is maintained via the teeth. Knurled thimble and tension levers can be supplied with scales and symbols. With teeth, a more accurate and wear-resistant indexing mechanism is obtained than with single dowel locations.

When a very high torque is to be transmitted, engaging and disengaging of the teeth is made difficult due to the small clearance i. e. the friction between them. In such cases Indexing levers GN 215are recommended.