When using the SKF OK couplings for shaft connections, advantage is taken of the powerful oil injection method.
Preparation of the shaft is simple. No keyways to machine, no taper and no thrust ring. When mounting the OK coupling, a thin inner sleeve with a tapered outer diameter slides onto the shaft. A thick outer sleeve with a matching tapered inner surface fits onto the inner sleeve. Ordinary mineral oil is then injected between the sleeves. A built-in hydraulic jack drives the outer sleeve up the taper of the inner sleeve.
When the outer sleeve has reached its final position an interference fit is created – just as if the outer sleeve had been heated and shrunk on. But no heat is required, and the coupling can be removed as easily as it was mounted.
This powerful use of friction enables the OK coupling to transmit torque and axial loads over the entire area of the shaft. There are no stress raisers at the keyway. And no fretting when high shock or reversing loads exist.
Very large couplings, which previously could only be shrunk on after heating, can now be assembled cold with the OK method.
Designs
The OKC coupling has been on the market since the early 40s. OKC couplings are the standard with many well-known controllable pitch propeller manufacturers in the world, but are also used for other applications such as rolling mills, pumps, diesel engines, etc.
Designs
The inner sleeve of the OKCX coupling is coated with carbides utilizing advanced plasma technology. This coating increases the torque capacity considerably, some 50% higher than for an OKC coupling of the same size, and gives the OKCX coupling a number of advantages:
Designs
The OKCK coupling for wind turbines is designed to fit within limited space, and yet still maintain the benefits of more traditional SKF OK couplings: quick and easy mounting and dismounting. It is designed to create controlled high pressure against the shafts without leaving any tooling permanently in place. The OKCK Coupling is mounted using oil power. No loud and vibrating pneumatic wrenches are used. Factory mounting time is less than half an hour and the dismounting time is the same. This also applies if the coupling has to be dismounted and mounted on-site.
Practical testing has shown that the OKCK coupling reduces mounting time up to sixteen times compared with mechanical couplings. And only one person is needed to perform the job.
Designs
The OKF coupling (fig 3) was developed to create a simple connection between a cylindrical shaft and engines or gearboxes having a flange at the thrust shaft. The OKF coupling is available with or without a hydraulic unit for mounting/ dismounting. Since the coupling is mounted on a cylindrical shaft and not fixed by keyways, it can easily be adjusted axially and rotated to the desired position.
As with mounting the innovative OKC coupling, the OKF coupling requires only a cylindrical shaft. It is based on the principle of transmitting torque by applying a powerful interference-fit with the oil injection method. Mounting and dismounting takes a fraction of the time required with conventional devices.
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