A MOUNTING FOR MACHINERY

Abstract: The engine (5a) and other machinery within a marine vessel is mounted on a raft (4) which is relatively flimsy compared with conventional constructions. The raft (4) is supported by electromagnets (8) the current to which is controlled so as to avoid vibration and flexing which would otherwise take place and so as to reduce transmission of vibration to the hull and other parts of the ship.

Description: This invention relates to a mounting for machinery. It is conventional in some areas of marine engineering to mount machinery, including an engine, on a raft which is then installed in the hull of the ship with the inter-position of springs and shock absorbers as a means of reducing the amount of noise transmitted through the hull. Hitherto the raft has been made as rigid as possible. This has resulted in a very large and heavy structure. Even so however problems are sometimes experienced as a result of vibration and flexing of the raft. This results in undesirable noise and can also result in breakdowns because of imperfect alignment of different articles of the machinery. One example of such problems has been the fracture of fuel pipes. The invention arose during a consideration of the above problems. This invention provides a mounting for machinery comprising a raft for supporting the machinery and an array of supports for the raft, characterised in that the raft is non rigid and the supports are adjustable and are controlled by control means, in dependance upon flexing or resonance of the raft detected by the control means, such as to suppress that flexing or resonance. By employing the invention it will be appreciated that it becomes possible to use a raft construction which is relatively flimsy, since the relative positioning of the different parts of the machinery, or the different machines, may be determined by the control means rather than by the stiffness of the raft. The size and weight of the conventional raft need therefore no longer be such a problem. If the control means acts in such a way as to ensure that the integral force transmitted to a carrier for the machinery, for example the hull of a ship, has a substantially zero component for vibrations associated with the aforementioned flexing and resonance; then noise and other vibration transmitted to the hull of the ship (or carrier for the machinery) can be very substantially reduced. This is an additional advantage that can be obtained by employing the invention. Alternatively the appropriately defined weighted integral of the force transmitted may have a substantially zero component for vibration associated with the flexing and resonance such that the force, although zero over the whole area of the raft, can be greater over localised areas that provide rigid support, this thereby eliminating or reducing forces on those areas that are weaker or themselves susceptible to vibration. As mentioned above the present invention enables the weight of the raft to be greatly reduced. By taking this to the extreme it is possible to eliminate the raft altogether, and according to a second embodiment of the invention there is provided a mounting for machinery comprising an array of supports for the machinery, characterised in that the machinery is non rigid and the supports are adjustable and are controlled by control means, in dependance upon flexing or resonance of the machinery detected by the control means, such as to suppress that flexing. It is possible that hydraulic or other mechanisms could be used for the supports. However electromagnets are preferred. One way in which the invention may be performed will now be described by way of example with reference to the accompanying drawings in which:- Figure 1 is a schematic cross-section through a ship constructed in accordance with the invention; and Figure 2 is a schematic illustration of the functioning of the control. Referring to Figure 1 there is shown a ship having a hull 1 in which a seating 2 is installed in accordance with conventional practice. The seating defines a recess 3 which receives a raft 4 which, in the illustrated arrangement, is of relatively flimsy and flexible construction compared with known structures. The raft 4 carries various items of machinery including an engine 5a, a generator 5b and a pump 5c which are linked together by links (shown schematically by the lines 6) and therefore need to be accurately aligned with each other. A number of permanent magnets 7 are mounted in the seating 2 and these are aligned with respective electromagnets 8 mounted in the raft 4. Sensing transducers 9, only two pairs of which are shown, are also mounted on the seating and on the raft and act to detect the distance between those two components at different places, they may comprise of any transducer type giving an electrical output, but preferably comprise of either optical or magnetic sensing means. An electronic control system 10 receives measurements from the sensors and controls the currents through the various electromagnets in such a way as to ensure that a) the raft 4 does not flex or vibrate and b) the integral force transmitted to the seating from the raft has a substantially zero component for vibrations associated with any flexing and resonance of the machinery itself. Although in this embodiment electromagnets 8 are described repelling permanent magnets 7, one skilled in the art will realise that pairs of electromagnets may be used or alternatively an arrangement is foreseen whereby electromagnets are used to attract metallic members connected to either the raft or the hull in order to keep the raft levitated. With reference to Figure 2 a schematic illustration is shown of the functioning of the control device. The input from the sensors 11 undergoes a modal matrix decomposition function which identifies wave functions within the raft. Once these wave functions are identified control elements for each actuator produce an inverse modal matrix configuration 14 which via the output to the actuators 15 reduces or cancels flexing and vibrations within the raft.

Claims: A mounting for machinery (5,6) comprising a raft (4) for supporting the machinery and an array of supports (7,8) for the raft, characterised in that the raft (4) is non rigid and the supports (7,8) are adjustable and are controlled by control means (10), in dependance upon flexing or resonance of the raft detected by the control means, such as to suppress that flexing or resonance. A mounting according to claim 1 in which the control means controls the supports such that the integral force transmitted to the carrier for the machinery has a substantially zero component for vibrations associated with the flexing and resonance. A mounting according to claim 1 in which the control means controls the supports such that an appropriately defined weighted integral of the force transmitted has a substantially zero component for vibration associated with the flexing or resonance. A mounting for machinery comprising an array of supports for the machinery, characterised in that the machinery is non rigid and the supports are adjustable and are controlled by control means, in dependance upon flexing of the machinery detected by the control means, such as to suppress that flexing. A mounting as claimed in any preceding claim wherein the array of supports comprises an array of electromagnets. A marine vessel incorporating a mounting as defined in any preceding claim.

Inventors: JOHNSON, FREDERICK ALISTAIR, SWINBANKS, MALCOLM ALEXANDER
Applicants: GEC-MARCONI LIMITED
Application year: 1989
Main classification: B63H21
IPC codes: B63H21, E05B15, B23Q11, B09B3, F16M5