US2271667A - Electroacoustic transmitter and the like - Google Patents

Description

Feb. 3, 1942.. D. o. SPROULE 2, 7

ELECTROACOUSTIC TRANSMITTER AND THE LIKE Filed May 1, 1959 2 Sheets-Sheet l !//z a g Dona\d sproum vEN-roQ Feb. 3, 1942. D. o. SPROULE 2,271,667

ELECTROACOUSTIG TRANSMITTER AND THE LIKE Filed May 1, 1939 2 Sheets-Sheet 2 J K y c &

Patented F ch. 3, 1942 ELECTROACOUSTIC TRANSMITTER AND THE mm.

Donald Orr Sproule, London, England, assignor of one-third to Arthur Joseph Hughes, Essex, England, and one-third to Henry Hughes & Son Limited, London, England, a British com- 7 Application May 1, 1939, Serial No. 271,025

In Great Britain May 4, 1938 7 Claims.

This invention relates to electro-acoustic transmitters and the like and has for one object to form a structure which can be magnetised rapidly and strongly and which can be demag- I netised rapidly.

Another object of the invention is to form a magnetic structure in which the magnetising flux can be built up in the magnetic circuit very rapidly and, to a considerable extent free from the delaying action of eddy current in the magnetic material thus enabling echo sounding transmitters to be constructed in which the polarising coil may be energised very powerfully but only intermittently.

A further object of the invention is to form an electro-acoustic transmitter or the like in which the length of the magnetic circuit is reduced, the density of the magnetising electric current can be increased and the dimensions andinductance of the magnetising coil may be made less than is usual with known constructions.

Owing to the conditions and circumstances of use it is most important that the utmost economy of space, weight and cost of materials should be exercised thus making it undesirable if not quite impracticable to employ a permanent magnet in such transmitters also the ordinary form of electromagnet is unsuitable when it is required to energise such electromagnet only for that time during which the driver coil is being energised as the solid construction prevents a rapid rise and fall of the field strength in the gap and the high inductance of the windings prevents the necessarily rapid rise in current that is called for if the magnetic field strength is to be raised rapidly.

An additional object of the invention is to en able a very robust and powerful electro-acoustic transmitter to be constructed suitable for echo sounding and similar purposes which can be operated more economically than known transmitters for the same purpose.

The invention consists of an improved electro-acoustic motor having a stationary electromagnet with a polar gap for a driver coil and a polarising coil characterised in that the electromagnet core is composed of laminations of magnetic material insulated from one another.

The invention can be put into practical effect by many divers constructions and arrangements so that the following description must be considered as of one example only.

In the drawings- Fig. 1 is a front elevation of one kind of lamination used in the construction.

Fig. 2 is a front elevation of another kind of lamination used in the construction.

Fig. 3 is a part sectional perspective'elevation showing a stage of assembly.

Fig. 4 is a part sectional perspective elevation showing the assembly completed. a

Figure 5 is a fragmentary plan view drawn to a larger scale partly in section and with parts broken away to expose underlying features;

Figure 6 is an elevation of one form of improved electro-acoustic transmitter arranged according to this invention.

As shown in Figure 4 a radial cross sec- 7 tion through the improved construction exhibits a pot magnet A having a tunnel a for a polarising coil b, a polar gap c for a driver coil and angular surfaces d and e for cooperation with the base plate I and ring g.

The improved pot magnet A is composed of la'minations of magnetic material which are arranged radially or substantially so and which are of such parallel or taper transverse section that they can cooperate with insulating material and/or spacers interposed therebetween to be compacted into annular foim..

To enable the polarising coil b to be located in the tunnel a, the pot magnet structure A consists of two series of laminations, an inner series of laminations h (Figure 1) substantially of rectangular form and notched on the lower part to produce the angular surface d and an outer series of laminations (Figure 2) substantially of channel shape to form the tunnel a between the limbs k and l when associated with a lamination h as shown in Figure 4. Each lamination j is notched to produce an angular surface eand the radial length of the limb is is less than that of the limb I so that the gap 0 is formed when the parts are assembled.

The individual laminations h and i are composed of magnetic material with an insulating layer and may be stamped from ordinary flat sheet, th said laminations being assembled radially or substantially so. Aseach lamination h or a is substantially of equal thickness when out from a flat sheet if they are arranged radially it is necessary to introduce spacers m of paper in the gaps non the external peripheries as shown in Figure 5 to enable consolidation to be effected. Alternatively the use of the spacers m may be avoided if the individual insulated laminations are slightly curved so as to increase the effective thickness of each lamination h, or :irelatively to the increase in radius, or some or all of the laminations h or 7' are given a wedge shaped cross section.

The construction shown in the drawings includes the circular base plate I having an internally arranged annular flange o presenting an angular surface 12 externally and a threaded outer periphery q for cooperating with the screwed ring 9 having an internal angular surface 1'.

During assembly, as shown in Figure 5 the inner series of insulated laminations h and paper spacers m is arranged on the base plate 1 with the angular parts d in contact with the angular surface p of the annular flange o, the polarising coil b is placed in position and the outer series, of insulated laminations a and paper spacers m is arranged on the base plate f over the coil b with the internal faces of the lower limbs l in contact with the external surface of the inner series, the screwed ring 9 is then placed in position and tightened up to clamp the assembly of stampings' h and 7, the spacers m and the coil b firmly in place and with the laminations insulated from one another.

The whole assembly may be impregnated withshellac, artificial resin, condensation product, or other insulating natural or artificial substance or composition to increase the rigidity of the structure and usually is attached to the remainder of'the electro-acoustic apparatus byscrews or the like as shown in Figure 6.

It will be recognised that by the use of a laminated structure for the pot magnet A the delaying action of eddy currents is avoided and that.

it is possible toenergise thepolarising coil 1) intermittently by an electrical current of higher density than is possible or convenient when continuous energisation is efiected thereby enabling the size of the polarising coil 1) to be reduced and the length of the magnetic circuit to be shortened with a consequential reduction of the magnetic reluctance so that it is possible to use a relatively small number of ampere turns having a comparatively low inductance.

The so called driver coil s located in the gap 0 may be of the usual wire wound form or may consist of a solid metal ring in which the exciting current may be induced by transformer action from the polarising coil b supplied with an energising alternating current for this purpose in addition to the pulses of direct current for polarising, thus reducing the supply conductorsv to a single'two core cable, said solid metal ring having very much greater strength. than a coil of wire such as s wound on a former t so that it is better able to withstand the very large forces to .lar series of bifurcated laminations with limbs of unequal length arranged with said limbs disposed radially and inwardly, an annular series of rectangular laminations arranged radially and each having one end in contact with a longer limb of" one of said first named laminations and 7 the other end spaced from the shorter limb of said one of said bifurcated laminations to define an air gap, a polarising coil between said limbs, an annular driving member in said air gap, a pair of annular members engageable with the inner edges of said rectangular laminations and the outer edges of said bifurcated laminations to clamp said laminations together in said annular form and interengaging means for detachably connecting said annular members.

2. An electroacoustic motor having an annular series of bifurcated laminations with limbs of unequal length arranged with said limbs disposed radially and inwardly, an annular series of rectangular lamination arranged radially in contact with one series of lambs of said first named laminations and spaced from the other series of said limbs to define an air gap, a polarising coil between said limbs, an annular driving member in said air gap, oppositely directed inclined portions on the outer edges of each of said laminations, and a pair of detachably connected annular clamping elements having inclined surface portion engaging the inclined edge portions of said laminations to retain the latter in position.

3. An electroacoustic motor having an annular series of bifurcated laminations of even thickness with limbs of unequal length arranged with said limbs disposed radially and inwardly, wedge shaped spacers between said laminations, an annular series of rectangular laminations of even thickness each rectangular lamination being disposed radially with one end in contact with the longer limb of one of said first named laminations and the other end spaced from the shorter limb of said one of said first mentioned laminations to form an air gap, wedge shaped spacers between said laminations, a polarising coil between said limbs, an annular driving member in said air gap, an angular projection on the outer edge of each lamination, a base plate and a clamping element detachably connected to said 'base plate, said base plate and clamping element said limbs disposed radially and inwardly, wedge shaped spacers between said laminations, an annular series of rectangular laminations of even thickness arranged radially in contact with one series of limbs of said first named laminations and magnetically cooperating with both series of said limbs to form annular salient poles, wedge shaped spacers between said laminations, a polarising coil between said limbs, an annular driving member between said po les, an angular projection on each lamination, an annular base plate, an annular fiange on said base plate having an angular surface to fit the angular projections on the rectangular laminations, an external screw thread on said base plate, a ring, said ring having an angular surface to 'fit the angular projections on the bifurcated laminations and an internal screw ths ead to fit the screw thread on said base plate.

5. In an electroacoustic motor, the combination of a serie of bifurcated thin laminae having spacedapart limbs arranged in the form of an annulus with said limbs directed radially of said annulus, a second series of substantially rectangular laminaedisposedjn alignment witltsaid bifurcated laminae with one end of each lamina of said second serie in contact with one limb of each bifurcated lamina and the other end adjacent to and spaced from the other limb of said bifurcated lamina to form an air gap, relatively inclined portions on the outer edges of the laming paced apart limbs arranged in the form of an annulus with said limbs directed radially of said annulus, a second series of laminae spanning the gap between and in alignment with the limbs of said bifurcated laminae with one end of each laminae of said second series in contact with one limb of each bifurcated lamina and the other end adjacent to and spaced from the other limb of said bifurcated lamina to form an air ,gap, relatively inclined portions on the outer edges of the lamina of both series and a pair ofinterengaging members having surfaces complementally inclined with relation to and engaging the inclined portions on said laminae for retaining the latter in said annular form.

7. The device as set forth in claim 6 comprising a polarizing coil between the limbs of said bifurcated member and a driving member disposed in said air gap.

DONALD ORR. SPROULE.

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