Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B06—GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS IN GENERAL
  • B06B—METHODS OR APPARATUS FOR GENERATING OR TRANSMITTING MECHANICAL VIBRATIONS OF INFRASONIC, SONIC, OR ULTRASONIC FREQUENCY, e.g. FOR PERFORMING MECHANICAL WORK IN GENERAL
  • B06B1/00—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency
  • B06B1/02—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy
  • B06B1/04—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with electromagnetism
  • B06B1/045—Methods or apparatus for generating mechanical vibrations of infrasonic, sonic, or ultrasonic frequency making use of electrical energy operating with electromagnetism using vibrating magnet, armature or coil system

Definitions

• the present invention concerns an electromechanical transducer for transmitting low frequency vibrations to a mechanical system, e.g. to a part of a ship's hull.
• the purpose of transmitting such vibrations is to prevent fouling by marine organisms on the outside of the hull.
• the starting point of the present invention is to be found in Norwegian publicy available patent application no. 87.3306, with the same inventor as in the present invention.
• a transducer of electrodynamical and loudspeaker-like type where a center bolt which is fixed to the transducer voice coil extends through a central and axial bore in a substantially cylindrically shaped magnet.
• the magnet poles are separated by a cylindrical air gap in which the voice coil is situated, and the magnetic field is substan ⁇ tially radial from the central pole to the concentrically surrounding other pole.
• the central pole has a through bore for the center bolt extending therethro'ugh.
• Two support springs or diaphragms are provided for retaining the magnet in its position.
• the two diaphragm springs are arranged substantially flush with the two substan ⁇ tially flat and parallel surfaces of the cylindrical magnet, an the voice coil is secured with varnish onto a coil bobbin of plastic or cardboard material fixed to the center bolt outside one of the support diaphragms.
• fig. 1 shows an axial cross section through an embodiment of a transducer in accordance with the invention
• fig. 2 shows the same transducer in an axial view directly "from above”.
• the transducer in accordance with the invention is intended to be fixed e.g. to a hull plate in a ship in order to impart transverse mechanical vibrations to the plate.
• the hull plate is equipped with a hold in which the transducer center bolt 1 is well secured by means of a screw connection.
• the center bolt 1 may of course be connected with the mechanical system to be vibrated, in other manners than the one shown here, for example by welding, a nail connection, a quick-coupling or similar means.
• Reference numeral 4 concerns a magnet of strontium ferrite, which magnet has a cylindrical shape with concentric magnet poles and an annular air gap pole, analogous to the prior art transducer embodiment.
• the center pole 13 has a central and axial bore through which the center bolt 1 extends, and the magnetic field between the poles extends substantially radially from the central pole 13 to the surrounding pole, through the air gap 12.
• a coil bobbin 7 projects into the air gap 12, from above in the figure.
• a coil 6 is wound onto the b"obbin 7.
• the coil bobbin 7 which has a cup shape (standing upside down in the figure) in accordance with the invention is formed by one single piece, and is made of rolled metal, preferably aluminum.
• a coil bobbin is made of cardboard or plastic material, but the new coil bobbin used here, which bobbin is a central feature of the invention, is able to withstand far stronger forces than the previous constructions, and also provides much more efficient removal of heat by conduction, enabling the use of higher power.
• Other metals than aluminum may be used, however these metals must be rollable and have such characteristics that the magnetic field in the air gap is not influenced substantially, e.g. weakly paramagnetic characteristics.
• the coil 6 is wound onto the bobbin 7 and fixed thereto in a particular manner.
• a varnish as fixing agent
• this type of coil winding is able to withstand temperatures of about 240°C, in comparison with a previous upper limit of about 120°C.
• the coil bobbin 7 is secured with its central area (the bottom of the cup) to the center bolt 1, and consequently stays stationary in relation thereto.
• the aluminum bobbin 7 is more rigid than a coil bobbin of cardboard or plastic material, and thereby also provides a more ideal behaviour (i.e. lack of behaviour, or really lack of movement) of the coil 6 in the air gap 12, which air gap has as narrow a shape as possible in order to give the transducer a high efficiency.
• the magnet 4 is supported by two support springs or diaphragms 2 and 8.
• the examplary configuration of the diaphragms or springs 2 and 8 appears most clearly from fig. 2, in which a three-arm configuration is shown.
• the support springs 2 and 8 are secured to the center bolt 1.
• Substantially flat arms extend from the central area, in this case three arms, to mounting positions on magnet 4.
• a central feature of the invention is the arrangement of the distance pieces 11 on the outside of plates 3 and 5, said distance pieces being used for the mounting of the diaphragms or support springs 2 and 8.
• the diaphragm springs 2 and 8 are equipped with suitably placed knee points 9 in each arm. This feature is introduced in order to obtain a precise constructional control of spring stiffness for the support springs 2 and 8, and consequently a precise determination of natural resonance for the transducer.
• the support springs 2 and 8 are preferably made of metal, e.g. brass, and possesses a high modulus of elasticity.
• Reference numeral 10 represents a bracket on the coil bobbin 7 with terminal ears for electrical supply leads to voice coil 6.

Landscapes

• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)
• Audible-Bandwidth Dynamoelectric Transducers Other Than Pickups (AREA)
• Piezo-Electric Transducers For Audible Bands (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=19892024

Family Applications (1)

Country Status (3)

Cited By (5)

Citations (11)

• 1989
  • 1989-05-16 NO NO891976A patent/NO167699C/no unknown
• 1990
  • 1990-05-16 WO PCT/NO1990/000085 patent/WO1990014169A1/en unknown
  • 1990-05-16 AU AU56519/90A patent/AU5651990A/en not_active Abandoned

Patent Citations (11)

Non-Patent Citations (1)

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