Патент USA US2119272код для вставки
- May 31, 1938'.' B, A, ENGHOLM ' ~ 2,119,272 LOUDSPEAKER Filed July 5, 1934 i741 @547 Baa-4, X/4Z, vim Sum/wen Patented May 31, 1938 . c , 1 : q r UNi'i‘ED STATES PATENT OFFIQE 2,119,272 LOUDSPEAKER Bernard A. Engholm, Shaker Heights, Ohio, as signor to The Bola Company, Cleveland, Ohio, a‘ corporation of Ohio Application July 5, 1934, Serial No. ‘733,757 2 Claims. (01. 179-4155) This invention relates to loud speakers, such opening 13 into which the tip of the inner pole for exampleas those, which utilize a moving coil piece extends, whereby an‘ annular air gap is that operates in an air gap across a magnetic ?eld. Speakers, which have a magnetic ?eld that is produced by a permanent magnet usually comprise a strip which is rectangular in cross section, and which has a width that is severaltimes the thickness. The strip is generally arranged in the form of a U and supports an inner pole piece 10 on the intermediate portion, and an outer pole piece at the ends of the arms of the U. The inner pole piece, heretofore, so far as I am aware, has been a solid cylinder, the diameter of which has been considerably smaller than it the width of the magnet. I have found however, that such construction is objectionable in that it restricts the extent to which the magnet can be charged at the time of excitation. I believe that the restriction is due to the fact that the 20 pole piece, because of its small size becomes saturated before the magnet, and thereby prohibits the introduction of su?icient flux at the time of excitation to saturate the magnet. As a result, _ the flux distribution in the magnet does not have s the desired degree of uniformity, and the density is greatly impaired. provided between the two pieces. A voice coil M is removably mounted on a support !5, within the air gap, and the support in turn is attached to a diaphragm l6, which is illustrated as being substantially conical in form. The interconnected support and diaphragm are shown as being at tached to a centering member I‘! which is rigidly fastened at its inner periphery to the neck of 10 the diaphragm and at its outer periphery to the clamping rings '9- The clamping rings in turn may be attached to astationary diaphragm hous ing 20, as by securing members 72 I. I have found that if the inner pole piece is 15 made solid and of uniform diameter throughout its length,‘and that if the diameter is less than the width of the permanent magnet, that the magnet can be charged, but that the extent of it will be materially less than if the inner pole 20 piece were made in accordance with my inven tion. The invention therefore, comprises a structure in which the pole tip is circular in cross section, within the region 0f the air gap but is ?ared outwardly from such region until it is sub- 25 stantially equal to the width of the _magnet. An object of my invention therefore, is to make a low reluctance pole structure, which when ap- This is particularly ShOWn in Fig- 3- ‘ F01‘ @6011 omy of manufacture, I make the inner pole piece plied to a permanent magnet enables it to be of laminations and fasten'them rigidly together, 39 charged to a much greater degree than any con- as by rivets. 30 struction heretofore designed, and of which I The permanent magnetic ?eld structure, which am aware. Furthermore, my invention is directed to a construction which, when the magnet is in use will result in a ?eld of greater inten- is produced by my invention, as described, great 1y increases the charge that can be imparted to the magnet at the time of excitation, and pro duces a structure that has more uniform flux 35 distribution over any type of pole structure here tofore used. sity and of more uniform ?ux distribution, for a magnet of a given Size, and Which can be made economically and readily assembled. Referring now to the drawing, Fig. l'is a side I c1aim:-— ’ elevation, partly in section, of a loud speaker hav40 mg 1'1 Permenent ?eld magnet; Fig- 2 is a real" View Of the Speaker shown in Fig. 1, but on a reduced Scale, with part Of the magnet broken away to show the interior construction, and Fig. 3 is a sectional view taken through the magnet 45 to show the inner pole piece in side elevation. The loud speaker with which I have illustrated my invention has a permanent magnetic 1_ In a loud speaker having a permanent mag netic structure comprising a one-piece U-shaped 40 strip- having substantially uniform width through out its length, and having an inner pole piece fas tened thereto, the inner pole piece comprising a plurality of ?at plates which extend parallel to each other and in the same direction as the arms 45 of the U, and having an outer pole piece at tached to the ends of the arms and having an ?eld structure, which comprises a U-shaped magnetic strip iii, to- which an inner pole piece mi N is rigidly connected, adjacent the midportion thereof, and to which an outer pole piece I2 is connected at the ends thereof. Pole pieces are opening that cooperates with the inner pole piece to provide an annular air gap, one end portion of the plates forming a cylinder and the inter- 50 mediate portion of the plates being ?ared in all planes which transversely cut the midportion preferably attached to the strip 58 by welding, although other forms of connection may be uti55 lized, if desired. The outer pole piece has an of the U-shaped strip. 2. A magnetic structure for a loud speaker comprising a permanent magnetic one piece 55 2 2,119,272 strip, an outer pole piece attached to the strip nection thereto, the plates terminating at the and having an opening therein, an inner pole opposite end in a reduced cylindrical tip which piece comprising a plurality of plates, means for holding the plates in abutting face to face rela tionship, each of said plates having a width equal to that of said strip adjacent its point of con projects into the opening in the outer pole piece to provide an annular air gap. BERNARD A. ENGHOLM.