Field of the invention This invention relates to split rings.

Background to the invention

Split rings or 'snap' rings are in common use in industry. They are simple rings that are split on one side to form a ring that can expand and collapse as a spring. A disadvantage of split rings is that they often expand or collapse in an uncontrolled manner. Smaller rings can be manipulated with hand tools but larger rings are generally rather cumbersome and are often installed by means of an uncontrolled release of the potential energy of the sprung state. This may well be a hazardous event. Moreover, the opening of a large split ring may also be difficult owing to the large forces required. For example, split rings which are used in subsea installations may have diameters of 750 to 1000mm or so and may require an opening force of up to 2000 lbs (lOOOkgf). This invention allows for the controlled manipulation of split rings in general and large split rings in particular.

Summary of the invention

The invention provides in one aspect a split ring including a multiplicity of apertures each of which extends in a radial sense through the ring and in each of which is disposed a unit which carries one end a rotary bearing member and is adjustable to cause the rotary bearing member to advance and retract radially with respect to the ring.

In a preferred form of the invention each unit comprises a threaded shank. The shank may have at its other end a slot for the rotation of the shank. Each unit may comprise a cage partially enclosing the rotary bearing member, which is preferably a ball. The invention also provides a method of fitting a split ring into a groove in a member having a cylindrical surface, the split ring including a multiplicity of apertures each of which extends radially through the ring, comprising: inserting into each of a multiplicity of the apertures a unit which carries at one end a rotary bearing member and adjusting the units such that the ring is supported with respect to the said surface by means of the rotary bearing members; moving the ring axially into register with the groove; adjusting the units further such that the rotary bearing members engage the groove; and reversely adjusting the units to disengage the rotary bearing members from the groove while allowing the ring to relax into the groove.

Each unit may include a screw-threaded shank and the units may be inserted and adjusted by a screwing action.

Brief description of the drawings

Figure 1 illustrates one embodiment of a split ring according to the invention

Figures 2 - 4 illustrates various phases in the fitting of the split ring to a grooved shaft.

Figure 5 illustrates in section part of the split ring including a ball transfer unit. Detailed description

In Figure 1 is shown a split ring 1, i.e. a solid ring which has a gap 2, which may be an oblique slit. The ring 1 is, as shown in Figures 2 and 3, intended for insertion in a circumferential groove 3 on the outside of a shaft 4. This is not the only use for a split ring and it may for example be inserted in an annular groove or profile on the inside of a cylindrical object such as a wellhead. The ring 1 has a series of apertures 5 spaced apart at preferably regular intervals around its circumference. Each aperture extends in a radial sense though the ring. In this embodiment the radial sense is centripetal but it need not be.

Into each aperture is inserted an adjustable bearing unit 6. One of these units 6 is shown in Figure 5. It comprises a threaded shank 7 which engages a fixed thread, in this embodiment provided on the inside of the aperture 5 so that a bearing can be advanced in a radial sense with respect to the ring 1. At one end (in this example the radially outer end) of the shank is a slot 8 by means of which the shank 7 can be rotated. At its other end, in this example the inner end of the shank, is a cage 9 retaining a rotary bearing member such as a ball 10 which protrudes from the end of the cage.

In order to fit the split ring onto the shaft 4 shown in Figures 2 to 4, units 6 are screwed into at least some of the apertures 5, i.e. preferably at least three of the apertures and preferably more than three. The units are adjusted so that the bearings 10 advance towards the cylindrical surface of the shaft 4 to support the ring on the shaft 4. Then, as shown in Figure 2, the split ring can readily be slid down the shaft 4, sliding on the bearings 10 of the units 6. This prevents the damage that is often caused to the surface of shafts when large split rings are installed. As is shown in Figure 3, once the split ring 1 reaches the groove 3 the ring 1 is slid to a position where the bearings 10 can be advanced into the groove 3. The gap may be wedged to avoid premature collapse of the ring 1. The bearings are advanced until they engage the floor of the groove so that the ring 1 can ride freely on the bearings 10.

In order to avoid a possibly hazardous snap of the ring into the groove 3, the bearings may be adjusted to provide minimal clearance with respect to the outside diameter of the shaft 4. The ring can rest on the outside diameter, overlapping the groove, thereby providing a brake on axial travel, and the units 6 can be adjusted to advance the bearings to the bed of the groove before the ring is moved finally into register with the groove. This technique minimises the release of potential energy from the stressed ring.

As is shown in Figure 4, once the ring is positioned correctly in the groove the bearing units may be reversely adjusted to retract the bearings 10 and the ring 1 may allowed to collapse into the groove in a safe and controlled manner. In this form of the invention the bearing units 6 may then be removed from the apertures 5 until the time comes to remove the ring 1 from the groove 4.

To remove the ring 1 from the groove 3 the process may simply be reversed. In essence the same method as described may be used for installing split rings into internal grooves by reversing the direction in which the units are facing, the bearings 10 being on the outside of the ring and the slotted end being on the inside of the ring 1. There could be two sets of apertures 5 and corresponding units 6. One set of apertures would be spaced (for example) one third the way across the ring from one side of the ring and the other spaced two-thirds the way across the ring. Then one set of bearings may support the ring on the shaft while the ring is moved into register with the groove and then the other set of bearings may be advanced to engage the bed of the groove while the ring is still supported on the shaft. Again, this technique minimises the release of potential energy from the stressed ring. The particular bearing units 6 as described above are simple and easily constructed. A less desirable but feasible alternative would be to use, instead of a ball, a roller held in a splined cage with a swivel coupling to the shank 7. More complex embodiments may also be feasible, for example a unit which can be secured within the aperture and includes hydraulic means for advancing and retracting the bearing member 10.