US2047361A - Electrodynamic loudspeaker - Google Patents

Description

July 14, 1936.

P. R. DIJKSTERHUIS 2,047,361

ELECTRODYNAMIC LOUDSPEAKER Filed Jan. 21, 1932 13 14 a \flw 12 rFn n n rfn m INVENTOR POPKO REINDER DIJKSTERHUIS AI'TORNEY Patented July 14, 1936 UNITED STATES PATENT OFFICE ELECTRODYNAMIC LOUDSPEAKER Application January 21, 1932, Serial No. 587,870 In Germany April 2, 1931 5 Claims.

This invention relates to an electrodynamic loudspeaker comprising a magnet, one of the pole pieces of which consists of a soft-iron ring.

According to the invention the ring and the magnet have clamped between them the means of supporting the diaphragm. This ensures that special means of attachment for the supporting members can be dispensed with and in addition that the clamping operation can be effected simultaneously with the placing in position of the ring. If, as is the practice, the ring is pressed into the magnet this method will assist materially to reduce the time of manufacturing the loudspeaker, also because any screws of attachment can be dispensed with, which is very important when loudspeakers of the said kind are to be produced in bulk.

The idea of the invention is preferably applied to loudspeakers furnished with a conical diaphragm the edge of which is secured to a carrier by means of a resilient substance. In such a case the carrier is clamped to the magnet system in the manner above referred to. In the said construction, this has the advantage of permitting during assembly of first suspending in the magnet the ring and the carrier and then suspending in the carrier the cone to which the coil for the speech modulated currents is attached and also the means for centering it.

In order that the invention may be clearly understood and readily carried into effect one construction in accordance therewith will now be described more fully with reference to the accompanying drawing. 7

In the figure, I designates a permanent magnet the pole pieces of which are formed by a soft-iron ring 2 and a soft-iron central stud 3 which are arranged relatively to each other to form an air gap 4. A coil 6 for the speech modulated currents which is secured to a conical diaphragm 5 is arranged in the said air gap in which it is kept centered, for example, by a flexible hood-shaped body "i, having its flange shaped edge 8 glued to the cone and being centrally fixed to the central pole by means of a small bolt 9.

The edge ID of the cone 5 has glued to it a strip I l of a yielding substance, say thin leather, which has its edge l2 clamped by means of small bolts l3 between a metal ring it and the edge l5 of a metal frame It. This frame is in the shape of a 'frustrum and is provided with spokes l'l united on the underside by an annular part I8 which according to the invention is clamped between the ring 2 and the magnet I. The clamping is efiected. by pressing the ring and the flange N3 of the the lateral wall which is situated in the neighbourhood of the air gap consists of a soft iron ring having such a section that the angles formed by the upper and the lower surface of the ring and the upper side and the lateral side of the stud which are at right angles to each other respectively are substantially equal. This construction has a great advantage in that the stud can have the usual cylindrical form that is to say such a form that from the point of attachment in the box it gradually decreases in section so as to have at least in the neighbourhood of the air gap, and throughout constant sections. A stud which is so constructed is preferable to a stud the cross section of which is larger near the gap than at the other points, as with a given volume of the gap the height of the latter depends on the diameter of the stud in the neighbourhood of the air gap and on the width of the air gap, and the height cannot be too small as in this case the leakage coefficient would receive an excessive value.

Having now described my invention what I claim is:

1. An electrodynamic loudspeaker comprising a magnet one of the pole pieces of which consists of a soft-iron ring, and means for supporting the loudspeaker diaphragm clamped between the ring and the magnet.

2. Electrodynamic acoustic apparatus comprising a magnet system, a diaphragm, and a rigid member extending from said magnet system to the peripheral edge of said diaphragm for supporting said diaphragm, said rigid member including a flanged portion, and a flange on a part of said magnet system adapted to clamp the 5. Electro-dynamic acoustic apparatus comprising a magnet system, said magnet system including at least two parts connected in series with respect to the flow of magnetic flux therethrough, a diaphragm, and a housing for said diaphragm having a portion clamped between said two parts of the magnet system and retained thereby solely by friction, said housing being adapted to support the peripheral edge of said diaphragm.

POPKO REINDER DIJKSTERI-IUIS.

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