Use of ring slides — The solution for rotational and indexing applications

Use of ring slides — The solution for rotational and indexing applications

Sponsored by Bishop-Wisecarver Corp.

Their compactness makes them particularly easy to install, although it is often necessary to mount the bearing arrangement on to a shaft with the outer diameter of the bearing in a fixed housing.

While ring slides are a costeffective solution for diameters below 200 mm, they really come into their own for diameters above this where it is useful to route services through the center of the ring. The above figure shows a ring-guidance system which has the outer diameter supported by vee bearings and which is driven using an integral gear drive.

This feature is also typical in turntable applications, pick-andplace units, and applications where components must be within the ring.

The figure on the top of the opposite page shows a rotorblade inspection system. It uses a full 360° ring with a removable segment as part of the circumference to allow access for insertion of the blade into the center of the ring. The segment is placed back in position allowing full 360° rotation and full inspection of the blade surface. With standard ring slides, guidance bearings can be positioned either internally or externally using a range of bearings from 12 up to 54 mm. Lubrication is only necessary between mating vee surfaces and is supplied by lubricators incorporating an oil felt pad.

Ring slides are used either in constant rotational applications or in indexing. An integral gear facility is available to let the ring be driven. This, in turn, reduces the need to set a separate ring gear with all the inherent setting issues.

Mounting of rings couldn't be simpler — they need only be bolted to a firm flat surface. This often is easier than setting a comparable bearing to a shaft and housing.

One other key benefit of rings is the ability to produce segmental movement. As standard rings have vee running surfaces on the inside and outside, a 90 or 180° segment can be cut from the ring. In fact, any angle is possible enabling movement of the carriage through an arc which is often a more-efficient way of providing guidance and is especially useful on medical scanning machines.

Load capacity is largely determined by the size and number of bearings. In many cases four bearing assemblies are used, two concentric and two eccentric, eradicating play. Generally for most applications, four guidance bearings will supply enough capacity relative to the size of the ring. It is possible to add bearings to increase capacity. However, it is not practical to position more than six bearings as equal sharing of the load becomes less likely. Higher loaded systems are best suited to use the heavy-duty range of rings which will take loads up to 52 Kn.

The range of standard rings is from 105-mm outside diameter up to 1,109 mm, with the larger heavier-duty range up to 1,656-mm diameter.

In applications, a set up of four bearings located around the circumference of the ring offers good levels of rigidity under load while offering a low coefficient of friction leading to lower driving forces. Rings can, therefore, be used in either precision positioning applications or in areas where a simple low-cost rotational movement is required.

The range of heavier-duty rings are single-vee-edge by construction internally or externally with a Mod 5 gear option available for driving.

Vee guidance bearings used are 64, 95 or 120-mm diameter making them particularly suitable for heavy turntable applications often seen in the automotive and mechanical handling industries.