US1786584A - Electromechanical vibration-translating device such for example as loud-speakers - Google Patents

Electromechanical vibration-translating device such for example as loud-speakers Download PDF

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Publication number
US1786584A
US1786584A US293961A US29396128A US1786584A US 1786584 A US1786584 A US 1786584A US 293961 A US293961 A US 293961A US 29396128 A US29396128 A US 29396128A US 1786584 A US1786584 A US 1786584A
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Prior art keywords
armature
force
centre
axis
point
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Expired - Lifetime
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US293961A
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English (en)
Inventor
Trouton Maurice
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WIRELESS MUSIC Ltd
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WIRELESS MUSIC Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R11/00—Transducers of moving-armature or moving-core type

Definitions

  • the present invention is'concerned with improvements in or relatlng to electrical devices of the type in which one member is caused to move relatively to another member under the influence of electrically generated forces acting between adj acent sur-- faces on the respectivemembers orin which electrical oscillations are generated by the relative movement of two members, the move ment being at leastin part rotational.
  • One object of the present invention is to minimize the injurious effect ofreactiveforces acting upon an armature during viuse'the'se forces to advantage.
  • Another object of the present invention is to provide an electro-magnetic vibratory device which is eflicient and in which a substantially linearerelation between a plied curbration due to the loa'dwhich it drives, or to rent and resulting displacement o a point in the armature maybe obtained, Whether the pole pieces actuating the armature'areon the same or onopposite sides of thearmature.
  • a further object of the invention is to tor in which equal and opposite currents fed to the'fdevice produce equal and opposite displacements of a point on the armature.
  • the memberxto be driven by a vibratoryrarmature, or thememberadapted to drivethe armature is connected to the armature at a point (referred to as th'e' point of attachment) situated between the centre and the heelthereof.
  • the armature isto be regarded as those parts of the vibratory member which lie, atany moment, vertically above the stationary co-operating surface (assuming that the stationary surface is disposed horizontally) and the end of the armature nearer the real or virtual'axisj of rotation thereof will be referredto as the heel of'the arma "provide an efiicient electro-magnetic vibradevice in whlch' the magnet poles are turefthe opposite end of the armature being referred. to as the toe.
  • the armature is so dimensioned and disposed that as it moves from its position of closest proximity toacooperating surface away from said surface, the point at whichfithe resultant attractive force (referred to as the centre of force) acts, moves towards the toe of said armature.
  • the parts are so dlmensioned and disposed that, asthe armature moves, the
  • the point. of attachment is so selected that the centre of force moves from one side to the other side of the point of attachmentas the armature moves from its innermost to its It is preferably arranged that the change inthe radius of rotation of the centre of force during movement of the armature shall be sufficiently large in relation to the radius itself, to provide compensation for relatively large changes of attractive force.
  • Figs. 1 to 3 are views in side elevation plan and end elevation respectivelyof a part of an electromagnetic vibratory device in accordance with the invention, the View in Fig. 1 being a section on the line R-R of Fig. 2, and
  • FIGs. & and 5 are diagrams illustrative of the invention.
  • a magnet (coils of which are indicated at C) is arranged with its pole pieces 1 and 2 projecting inwards, a small air gap being left between the tips of the pole pieces and the magnetic circuit being closed excepting for this air gap.
  • the upper surfaces of the pole pieces adjacent the air gap which will be referred to as the pole surfaces, will be regarded as one of the surfaces above referred to, namely the fixed surface.
  • the armature may therefore be regarded as mounted for rotational vibration about an axis 6 which is upon the centre line of the cross piece 4.
  • the cross piece 4 is thus adapted to twist and furnish the required restoring force.
  • the width of the armature is, as shown, greater than the width of the air gap.
  • the under surface of the armature will at first be considered to remain flat and for simplicity, its plane will be assumedto contain the axis of rotation 6, since very little error is introduced by this latter assumption.
  • the axis of rotation of the armature surface will thus be assumed to be at B (Fig. 1).
  • the law of magnetic force between the two surfaces is a complex one, but it may be assumed with sufficient accuracy for many practical purposes that the total magnetic force is equal to where 0 is a constant, aim is an element of length along the armature, (that is in a direction normal to the axis B), y is the distance between the element (Zn and the pole surface measured along its arc of rotation, p is the width of the magnet poles, the distance a: being measured from the edge of the poles nearer the axis of rotation, and A is a constant. It is interesting to note that the constant A may be regarded as the length of air gap (having the same cross section as the working air gap between armature and poles) which has the same reluctance as the iron path. A will be referred to as the equivalent minimum air gap.
  • Equation (2) is'only true if the armature is of such stiffness that its flexure can be disregarded. With such an armature it is found that in most practicalcases the value of 8 has to be made ratherhigh inorder to get a suflicient movement of the centre of force to give a sufficiently close approach tolinearity,-and this leads to lack of sensitivity. It has however, been discovered that if the armature be made so 7 that its flexure due to the forces acting upon it is not negligible, this flexure can be made to assist in securing linearity.
  • the armature In estimating the effect of the magnetic force in producing flexure we may regard the armature as a beam anchored at the heel of the armature. This will of course only be the case if, as in the device shown in Figs. L3, the armature is considerably more flexible 'than the member between it and the cross bar. l
  • the arm of the moment of the resultant magnetic force is shorter in this case than when rotation about the axis of rotation of the armature is being considered and a small movement of the centre of force will consequently have a greater effect.
  • flexure tends to reduce the toe air gap, that is to say, the effect in both cases is to make .
  • the armature move'lnore nearly parallel to itself than it would if it did not bend. If one surface moves parallel to itself and parallel to a co-operating surface, the centre of force does not move. If one surface moves parallel to itself but at an angle to a co-operating surface, the movement of the centre of force is greater than it would be with pure rotational movement.
  • the fiexure tends to reduce the movement of the centre of force towards the heel when the armature approaches the magnet pole and to increase the movement of the centre of force to wards the toe when the armature moves outwards. If the arrangement is such that the amount of fiexure is greater, owing to the movement of the centre of force (which may be regarded as acting at a short arm) in the outermost armature position than in the innermost position, the effect of flexure will be, as stated, to assist in giving the linear relation desired. i
  • Fig. 5 is a diagram illustrating the foregoing and also offering a possible explanation of the advantage of connecting a diaphragm to the armature at a point between the centre and the heel of the armature.
  • the armature 3 is shown in full lines in its outermost position during vibration and in dotted lines in its innermost position.
  • the armature is flexible and the disposition and direction of the forces acting upon it in the two positions are indicated by the arrows.
  • M and M are the resultant magnetic forces in the two positions respectively
  • L and L are the forces at the point of attachment due to the mass of the diaphragm or-other driven load
  • R and R are the mechanical restoring forces.
  • the amount of flexure which has been found desirable in practice is extremel small, for example of the order of 0.01. m/m, but since the total amplitude of vibration of the point of attach- .ment may not exceed 0.05 m/m and the final air gap will be a small fraction of the amplitude, it will be clear that a small amount of flexure may have a very important effect.
  • th'e magnet pole surfaces are mounted for rotary adjustment about an axis in their plane and in the same vertical plane as the point B.
  • the radius of rotation of the magnet poles was reduced by 2 m/m with good results.
  • the cross bar is mounted upon a platform the upper surface of which is 0.02 m/m below the axis of rotation of the magnet poles.
  • the length of the cross bar between the end supports is 38 m/m, the depth of the cross bar is 5 m/m and its width 1.2 m/m.
  • the radius'of rotation of the heel of the armature is 6.0 m/m, the length of the armature is 9.6 m/m, the thickness of the armtaure 1.7 m/m and its width 6 m/m.
  • the magnet is a U-shapedcobalt steel magnet (86% cobalt) 1 15 m/min length along the centre line, including the pole pieces, and having a cross sectional area of 85 sq. m/m.
  • the air gap between the pole pieces is 2.3 m/m.
  • the point of attachment is 1.2 m/m back from the centre of the armature.
  • a vibratory device comprising an arma- I turemounted for vibration about an axis,.a magnet pole surface adapted-to co-operate with a surface of said armature, means adaptedto vary theforce between the armature and magnet'pole surface inaccordance with electricaloscillations, a member adapted tobe driven bysaid armature, and'means connecting the armaturewith said member, said connecting means being attached to the armature at a pointsituated between the centre of said cooperating surfaces and the ends thereof nearer said axis.
  • a device for the inter-conversion of electrical and mechanical energy comprising an armature mounted for vibration about an axis, a surface'adapted to cooperate-with said armature, means for providing an attractive force between the armature and said surface, restoring means for the armature, and means, adapted to transmit mechanical vibratory energy, attached to the armature at a point within the magnetically active part of the armature, whereby the centre of attractive force will move from one side to the other side of said point as the armature moves, during vibration, from its position of closest proximity to said surface to' its position furthest fromsaid surface.
  • a device for the inter-conversion of electrical and mechanical energy-comprising an armature mounted for vibration about an axis, a convex surface adapted to cooperate with said armature, and means for providing an attractive force between said armature and said surface. q a Y 7.
  • a vibratory device comprisingan armature mounted for vibration about an axis, a magnet pole surface adapted to co-operate with a surface of the armature, means adapted to vary the force between said cooperating surfaces in accordance withelectrical oscillations, a member adapted to be driven by the armature, and means connecting the armature with said member, said means being connected to the armature at a point situated between the centre of said cooperating surfaces andthe ends of said surfaces near said axis, and the radial length of said cooperating surfaces being at least of the radius of rotary vibration of the centre of said cooperating surfaces.
  • a device for the inter-conversion of electrical and mechanical energy comprising an armature mounted for vibration about an axis, a magnet pole surface adapted to cooperate with a surface of the armature, and means, adapted to transmit mechanical vibratory energy, connected to the armature at a point within the magnetically active part thereof.
  • a device for the inter-conversion of electrical and mechanical energy comprising anarmature mounted for vibration about an axis, a magnet pole surface adapted to cooperate with a surface of the armature, means for providing an attractive force between the armature and said surface, and restoring means for said armature, the radial length of the said cooperating surfaces being at least of the radius of rotary vibration of the lengthwise centre of said surfaces and the disposition of the armature being such that the centre of attractive force thereon will move away from said axis when the armature moves during vibration from its position of closest proximity to said surface to its position furthest from said surface.
  • Adevice for the inter-conversion of electrical and mechanical energy comprising an armature mounted. for vibration about an axis, a magnet pole surface adapted to co operate with a surface of the armature, means for providing an attractive force between the cooperating surfaces, and restoring means for said armature, the radial. length of said cooperating surfaces being at least of the radius of rotary vibration of the lengthwise centre of said cooperating surfaces and the disposition of the armature being such that the point in the armature at which the resultant attractive force upon the armature acts, moves so that the moment of said resultant force above said axis varies according to a substantially linear law with the displace-- ment of a point on the armature towards and away from said surface.
  • a vibratory device comprising an armature mounted forvibration about an axis, a magnet pole surface adapted to cooperate with a surface of the armature, means adapted to vary the force between said cooperating surfaces in accordance with electrical oscillations, a member adapted to be driven by the armature, and means connecting said member to the armature at a point situated in the magnetically active part of the armature between the centre of said cooperating surfaces and the end of said surfaces nearer said axis, the portion of the armature which co-operates with said pole surface being flexible in relation to the portion thereof between said co-operating surfaces and axis.
  • a device for the inter-conversion of electrical and mechanical energy comprising an armature mounted for vibration about an axis, a magnet pole surface adapted to cooperate with a surface of the armature, and means, adapted to transmit mechanical vibratory energy, connected to the armature at a point situated between the centre of said co-operating surfaces and the ends of said surfaces nearer said axis, the portion of the armature which co-operates with said pole surface being flexible in relation to the porion thereof between said co-operating surfaces and said axis.
  • a device for the inter-conversion of electrical and mechanical energy comprising an armature mounted for vibration about an axis, a magnet pole surface adapted to cooperate with a surface of the armature, means for providing an attractive force between said co-operating surfaces, restoring means for the armature, and means, adapted to transmit mechanical vibratory energy, at tached to the armature at a point within the magnetically active portion of the armature.
  • the centre of attractive force is adapted'to move from one side to the other side of said point when the armature moves, during vibration, from its position of closest proximity to said surface to its position furthest from said surface, the portion of said armature which co-operates with said pole surface being flexible in relation to the portion thereof between said co-operating surfaces and axis.

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  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Reciprocating, Oscillating Or Vibrating Motors (AREA)
US293961A 1927-08-05 1928-07-19 Electromechanical vibration-translating device such for example as loud-speakers Expired - Lifetime US1786584A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB20732/27A GB299537A (en) 1927-08-05 1927-08-05 Improvements in or relating to electro-mechanical translating devices, such for example as loud speakers

Publications (1)

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US1786584A true US1786584A (en) 1930-12-30

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US293961A Expired - Lifetime US1786584A (en) 1927-08-05 1928-07-19 Electromechanical vibration-translating device such for example as loud-speakers

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US (1) US1786584A (enrdf_load_stackoverflow)
BE (1) BE353324A (enrdf_load_stackoverflow)
FR (1) FR658378A (enrdf_load_stackoverflow)
GB (1) GB299537A (enrdf_load_stackoverflow)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114666704A (zh) * 2022-03-17 2022-06-24 维沃移动通信有限公司 发声装置以及电子设备

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN114666704A (zh) * 2022-03-17 2022-06-24 维沃移动通信有限公司 发声装置以及电子设备

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Publication number Publication date
BE353324A (enrdf_load_stackoverflow)
GB299537A (en) 1928-11-01
FR658378A (fr) 1929-06-04

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