Rotary shafts – gudgeons – housings – and flexible couplings for ro – Fluid coupling
Patent
1998-06-03
2000-10-03
Browne, Lynne H.
Rotary shafts, gudgeons, housings, and flexible couplings for ro
Fluid coupling
464 32, F16D 380
Patent
active
061265497
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a coupling arrangement for coupling a driving unit to a driven unit.
2. Description of the Related Art
It is known to mount between driving and driven units different types of couplings which break the connection between said units when overloading occurs. If the driving unit tends to race when the load is disconnected, the revolutionary speeds on the driving side may become so great as to cause damage to the driving unit. For instance, when driving generators with the aid of steam or gas turbines, load peaks occur in the event of phase synchronization errors or short-circuits such as to necessitate the connection between turbine and generator to be broken immediately. However, when a small rotating mass is found on the turbine side of the coupling, the steam or gas turbine that was connected by the coupling may already have been seriously damaged or wrecked before the turbine drive has had time to switch off, i.e. within the space of one-half to one second. In the case of a water turbine that rotates at a speed of 120 rpm, for instance, and drives a generator through gearing at a speed of, e.g., 1500 rpm, the failure of a shear coupling mounted between the gearing and the generator with subsequent racing of the turbine, e.g. to a speed of 240 rpm, can wreck or seriously damage the gearing.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a novel and improved coupling arrangement with which the aforesaid problems are avoided.
To this end, there is proposed a coupling arrangement of the kind defined in the introduction which includes in combination a shear coupling which is active between the units and which fails immediately upon the occurrence of an overload, and a brake coupling which becomes active between the units when the shear coupling fails.
The arrangement proposed in accordance with the invention prevents the rotational speed of the driving unit from increasing excessively when the shear coupling fails, by virtue of the braking effect caused by of the brake coupling, so as to prevent damage and enable operations to be re-commenced after reestablishing the coupling between the units.
The shear coupling may be of any appropriate kind, and may, for instance, have the form of a conventional shear-pin coupling. Shear pins, however, have a tendency to become fatigued and may need replacing at given intervals in order to prevent undesirable failure of the coupling in the event of an overload which lies beneath the intended limit. According to the invention, the shear coupling will preferably comprise a coupling which is fixedly connected to one of said units and which includes a chamber that contains liquid under pressure such as to deform a coupling part into coupling engagement with the other unit, and means which functions to immediately remove the chamber pressure upon relative movement between the coupling and said other unit, so as to release coupling engagement between said other unit and the shear coupling. This type of shear coupling can readily be adapted so as not to be damaged by or cause damage to the units connected thereby, in the event of a coupling failure.
The brake coupling may also be a conventional coupling, for instance in the form of a disc coupling. It will be understood that the coupling discs will suffer considerable wear when the brake coupling is applied and normally it will be necessary to replace the discs after a shear coupling failure. The disc coupling will exert a full braking moment immediately the shear coupling fails, which is not always desirable in practice. According to the invention, the brake coupling will preferably be an hydraulic coupling which is active between the shear coupling on the one side and one of said units on the other side, this unit being disengaged from the shear coupling in the event of an overload. One advantage with this type of coupling is that the braking effect will increase with increasing differences in speed between the
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Appell Bo
Falk Curt
Binda Greg
Browne Lynne H.
Voith Safeset AB
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