Marine propulsion – Electric drive for propelling means
Patent
1997-10-08
1998-10-27
Avila, Stephen
Marine propulsion
Electric drive for propelling means
440111, 248638, B63H 2130
Patent
active
058270957
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a mount structure for supporting an electric apparatus comprising a rotor and a stator frame on a ground base. More particularly, the present invention relates to a mount structure for supporting an electric apparatus comprising a rotor and a stator frame, such an electric apparatus being preferably a marine engine rotating a propeller, on a ground base, such as a hull of ship, said mount structure comprising at least one vibration damping unit, which comprises a vibration damping rail, which is arranged to receive and damp the vibration of the electric apparatus and which is secured to the stator frame.
It is a known procedure to support apparatuses and engines causing vibration and trembling, for instance combustion engines, against the mount thereof by means of structures damping vibration or trembling, the object being to prevent the vibration from being transmitted to the ground base. If the ground base is very sturdy, vibration is not usually a great problem. However, if the type of the base is such that it may resonate according to the vibration of the apparatus and the engine, the vibration may become a great problem.
Many types of vibration damping structures are known in the above-mentioned objects. One commonly used way of damping vibration is to use elastomers, such as rubbers, which may be connected to different metal elements, such as bolts, flanges, sleeves, etc. The aim is thus to achieve an elastic structure, which also provides the structure with sufficient rigidity. In damping the vibration of combustion engines, rubber dampers and the like are widely used. Rubber dampers are used for instance in diesel engine--generator combinations, which are mounted on a common ground base. A problem of vibration dampers containing elastomers is that the capability of elastomers to damp vibration deteriorates as the elastomers age. Due to this, the use of rubber dampers is not desirable in objects which have to operate for a long time, and for which laborious repair service is not possible or is extremely undesirable. In addition, the problem with highly elastic dampers is that they also allow relatively large movement, which may cause high stresses on power transmission components provided in the shaft line if the combustion engine is rigidly attached directly to the shaft line. If elastic vibration dampers are used under a motor driving a propeller, a flexible clutch must also be used.
U.S. Pat. No. 5,160,113 discloses the mounting of an electric apparatus to a base by means of a vibration damping unit. The solution described in the publication is not suited for damping the vibration of a marine engine effectively.
Electric apparatuses, such as electric motors, constitute a group of apparatuses in which vibration and trembling are not usually a major problem. However, if an electric apparatus is large with respect to the ground base it rests on, great vibration may be produced in the ground base. The specific resonance of the ground base may be within a range which further intensifies the vibration. Trembling may also become a problem in applications where the requirements concerning the level of vibration are strict.
For instance vibration spreading in ships through structures is typically within a frequency range of 100-2000 Hz. Such vibration may cause disturbing noise for instance in cabins through resonating wall surfaces. The vibration causes small alternating motion in the hull, the magnitude of such motion being for instance 1 mm/s. Such vibration may be disturbing for instance in passenger ships, because of which the motion caused by the vibration is reduced, if possible, to be for instance lower than 0.3 mm/s.
The object of the present invention is to provide a mount structure for an electric apparatus, significantly reducing vibration and obviating the disadvantages mentioned above. The invention is preferably applied in ships, but other uses are also possible.
These aims are achieved with the mount structure of the invention, characterized in that spacing
REFERENCES:
patent: 4744539 (1988-05-01), Stimeling
patent: 4978320 (1990-12-01), Chaplin et al.
patent: 5022628 (1991-06-01), Johnson et al.
patent: 5054740 (1991-10-01), Wheeler
patent: 5160113 (1992-11-01), Whiddon
ABB Industry OY
Avila Stephen
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