US1859629A - Acoustic diaphragm - Google Patents

Description

y 1932- E. c. NILSQN 1,859,629

' ACOUSTIC DIAPHRAGM 2 Filed Feb. 9, 1928 2 Sheets-Sheet l INVENTOR Patented May 24, 1932 UNITED STATES-PATENT OFFICE EVERETT C. NILSON, OF WORCESTER, MASSACHUSETTS, ASSIGN OR OF FORTY PER CENT TO RALPH G. NILSON, OF SAN FRANCISCO, CALIFORNIA, AND TWENTY PER CENT TO NILS NILSON, OF WORCESTER, MASSACHUSETTS 'ACOUSTIC DIAPHRAGM,

Application filed February 9, 1928. Serial No. 253,095.

This invention relates to acoustic diaphragms and .more particularly to diaphragms employed in radio loud speakers,

commonly known in the art as cone speakers. It has for its Object the production of a diaphragm which is almost entirely free from resonance within-the audible range. This is accomplished by constructing the diaof cones, cylinders, prisms, spheres, pyramids or hybridized surfaces of these shapes as will presently appear.

The various sections of the diaphragm may beso chosen and located that the resulting diaphragm will have-a beautiful artistic appearance. This is another object of the invention and many of the embodiments coming within the scope of the appended claims have beauty as-one of their main attributes.

The number ofdesigns possible is infinite and the designs shown in the drawings are representative only and are illustrative of.

the wide variety of shapes whi h may result in the practice of this invention. The different sections can be colored in various ways to give "more prominence, to the design used. The design will be symmetrical, as shown in the drawings, or it can be unsymmetrical to adapt itself to available space in a radio 'cabinet or other support provided for the loud speaker. .Sections may be chosen in such a manner that the resulting design has the appearance of some object, such as a ship, a star, an animal or a person, such object being in relief. while at the same time improving the acoustic characteristics of the diaphragm. In all cases, however, whether the d aphragmbe designed from an acoustic or from tlHaItlStlC viewpoint, there will be however,

a decrease in the resonance defects which prevail in diaphragms of the cone typeheretofore produced.

Diaphragms made in accordance with this invention are free from the type of distortion present in almost all other types of cone speakers and which causes a low mellow sound to be emitted inaddition to the sound which is being reproduced. This type of distortion spoils entirely the effect of. high shrill notes. In diaphragm's of the present invention high piercing sounds are reproduced as such in all their clarity and only the mellow tones are mellow. This result is brought about by the use of a plurality of individual sections as will hereinafter be described in detail.

In order that the invention may be more fully understood, attention is called to the accompanying drawings, in which:

Fig. 1 is a front elevation of a diaphragm made in accordance with this invention.

Fig. 2 is a central vertical cross section of Fig.

Figs. 3 and 4 are modifications.

Fig. 5 is a perspective view of a dia-.

phragm having hybrid surfaces similar to those shown in Figs. 1 and 2. Fig. 6 is a cross section taken on line 6-6 of Fig. 5.

In Figs. 1 and 2 a diaphragm is shown comprising a central curved tapering section 12 surrounded by a plurality of plane sections 13, a curved section 18 and an annular section- 19. The surface 12 is ahybrid surface in the form of a conical pyramid starting out as a circular cone at its apex 11 and gradually merging into a pyramidal base of five straight sides 15 forming a regular pentagon. Any other number of sides 15 may, of course, be employed and the particular number shown is illustrative of only a single embodiment. A surface of this type is highly aperiodic due to the different radial distances between points on the edg'e15 and the apex 11 of the surface. The surface 12 is perfectly symmetrical about its apex 11 and in this respect possesses a slight advantage in appearance over elliptical or eccentric cones which can be used to give this aperiodic effect. A suitable opening can be provided at the apex of the surface 12 to receive the driving rod or voice coil of a sound reproducing unit.

I Sections 13 are approximately plane and The surface 18 maybe defined as a truncated termediate sounds.-

sluggish to follow an conical pyramid. The annular section 19 7 serves to make the whole structure more rigid around the edge.

It will be apparent that the various sections, being composed as they are of different types of surfaces sions, will have different acoustic characteristics. The individuality of the sections allows them to vibrate separately in accordance with their own characteristics and the sound emitted from the diaphragm will be the sum of all the sounds emitted by the individual sections. I

A high piercing sound will vibrate section 12 and it will act as a simple diaphragm with a fixed edge in response to a sound of this pitch. The remainin sections may be too they will then serve to damp the vibrations of section 12.

Sounds next lower in the audible range will vibrate section 12 and sections 13 in unison. Should there be both high and intermediate sounds present, section 12 will emit both, while sections 13 will emit only the in- When such a condition exists, damping of the adjacent sections by each other is instantaneous and extremely effective. It is evident that if a body is vibrating at a particular frequency, another body vibrating at a I instantaneously kill the vibration of the first body when the two are brought in contact with each other.

which employ a stationary,rather than a vibratory, member to damp the vibrating body. In the present invention, any tendency at all in one section or group of sections to sustain a particular frequency will be immediately opposed by the adjacent sections. tirely eliminates the resonance defects of the simple cone speakers.

As the sounds become lower more and more of the sections will vibrate and the very lowest sounds will vibrate the diaphragm as a whole. It will be obvious that such a construction will produce a diaphragm in which more frequencies are reproduced by plunger having different dimen-v difi'erent frequency will- This method of damping is far more effective than those :methods This enaction of the diaphragm, as distinguished from transverse vibratory waves in the surface of the diaphragm. The small central section will act as a plunger t pe diaphragm on the higher fre uencies, w ile the larger surfaces act as a p ungerin reproducin the lower frequencies. I By the automatic al ocation of soundsin this manner to surfaces of different areas, there is a tendency for the amplitude of vibration to remain more nearly constant for all of the frequencies provided for in the design of the diaphragm.

In speakers of previous design it was desirable to use a lar e diaphragm so that low frequencies might v reproduced without too great a movement ofthe diaphragm. With such a diaphragm, quencies were distorted because the diaphragm prevented plun er action at these frequencies. On the ot er hand, when a smaller diaphragm is used so that the higher frequencies are more faithfully reproduced, the lower frequencies cause such a large amplitude of vibration that the pole pieces of the electro-ma netic unit are frequently struck byl the diaphragm, thereb setting up harsh metallic noises. In the ynamic, or moving coil, type of speaker the metallic noises are eliminated, but there is a detrimental efiect onthe flexibility andelasticity of the delicate'coil supporting spider, thereby destroying its effectiveness and occasionally causing the arms of the support to break because of mechanical fatigue. Such disadvanta es are obviously ehminated by the use of a iaphragm in which high frequencies are reproduced y a small area and the low frequencies by a large area, both having substantially the same relatively small amplitude of vibration. 1

Another important feature of the invention is also due to the individuality of the several sections and that is the automatic allocation of sounds of different intensities. Feeble forces which aretoo weak'to vibrate the mass of the whole diaphragm will vibrate cone 12 alone and sounds which would be lost on a massive simple cone diaphragm are thereby preserved. The stronger sounds will vibrate more sections and some sounds will be of such strength that the whole diaphragm will be vibrated. Since feeble forces act upon a relatively small surface and strong forces vibrate a relatively large surface, the. amplitude of vibration at the driving point will tend to remain more nearly constant over the entire volume range thereby giving rise to extremely important advantages.

Thus, in a diaphragm constructed-1n accordance with the present invention, there is a double allocation of the sound emitted from the diaphragm, one determined by the intensity of the sound and the other determined y ts frequency, both allocations having a beneficial effect on the performance of the however, the higher freamaze reproducer and increase the amplitude of vibration under conditions which would otherwise cause the amplitude of vibration to be too small and decrease it when it would otherwise be too great.

It will be apparent from the foregoing that a sound reproducer having a diaphragm constructed in accordance with the present invention has the effect of combining a plurality of cone speakers of different characteristics, retaining all of their individual advantages and disposing of their resonant disadvantages. Accordingly, sound reproducers can be designed to provide for tremendous volume and at the same time be capable of reproducing faithfully sounds of low volume. Heretofore, it has been necessary to sacrifice either sounds of high intensity or sounds of low intensity to attain substantial fidelity in the reproduction of sounds in one relatively narrow range of intensity. It is a matter of common experience thatnearly all .powerful sound reproducers manufactured on a commercial scale are deficient in reproducing the softer strains of a musical selection. for example, and to derive proper enjoyment from such reproducers or loud speakers it is necessary for the listener to be at some remote point while the loud speaker remains adjusted to give the volume for which it is designed. I have found, however,

that merely by substituting a diaphragm constructed in accordance with my invention,

' the full possibilities of the driving unit of the center of inertia of the entire diaphragm definitely to is located substantially within opening 11. It is at this opening that the driving force is applied and it is well-known that any force is most effective when it is applied to the center of inertia-of the mass upon which it acts. Only certain. embodiments coming T within the scope of this invention, however.

will have the driving force applied at the center of inertia, since this feature is dependent upon the size and shape of the sect-ions of which the diaphragm is composed.

3 illustrates a modificationin which sections of various types are chosen to give :the effect of a five-pointed-star in relief. Section 20 is a simple cone and the surrounding section 21 1s a hybr d surface merging from a circular cross-section to a polygonal crossgroups of sides 25 and 26.

section. The ridges 22 form a regular pentai gon and a hybrid surface having a peculiar shape. is formed between this pentagon and the irregular decagon bounded by the five Another group of sections bounded by the sides 25, 26,27 and 28 extend the irregular decagon 25, 26 into a regular decagon, 27, 28.

Surrounding decagon 27 28 is a hybrid surface 29 formed when decagon 27, 28 merges into a circle 30. The annular section formed between ridge 30 and edge 31 serves to reenforce the structure around its perimeter.

The diaphragm shown in Fig. 3 has the same advantages as the diaphragm shown in Fig. 1 but the artistic appearance is quite different.

Fig. 4 illustrates another modification in which a hybrid surface 32 having an apex 33 emanates from a cone and merges into a heptagon 34. This is surrounded. by another hybrid surface 38 formed by merging the heptagon 34 into circle 35. Surrounding surface 38 is another hybrid surface 39 between circle and hexagon 36. .In this modification the reenforcement along the perimeter is hexagonal in shape and this gives a pleasing appearance to the outline of the diaphragm.

All of the diaphragms illustrated can be made from a single sheet of inelastic material, such as paper, merely by cutting out a sector as in making a simp e cone diaphragm. Ridges can then be formed in the material and when the edges of the sector are brought together and joined, the ridges determine the shape of the several surfaces. It is, of course, not necessary'that the diaphragms be made in this way, or that they be made of paper. Probably the most practical method of manufacture will be to use moldable material which can be pressed into any desired shape in a single operation. Whether the diaphragm is made of paper or whether it is formed of moldable material, it is advantageous to choose the several surfaces of the diaphragm so that they are formable from an integral sheet of inelastic material. By so choosing the surfaces the diaphragm will be well proportioned and the weight of the diaphragm at any portion will be directly proportional to its distance from the center, just as in a simple cone diaphragm.

\Vhile I have shown and described certain preferred embodiments of my invention, it is to be understood that the various forms of diaphragms illustrated are representative only and that the invention, as defined in the appended claims, can be embodied in a wide variety of other forms.

I claim:

1. In a sound amplifying device, adiaphragm, the surface of said diaphragm comprising a hybrid surface formed by merging a cone and a pyramid.

2. An acoustic diaphragm having a truncated tapering surface, successive cross sections taken perpendicular to'the axis'of said tapering surface gradually changing 1n shape from one outline to a dissimilar outline.

3. In an acoustic diaphragm, a tapering surface, said tapering surface being bounded -having a plurality of sections, one of said prising a circular ridge and a polygonal ridge, the center of the polygon formedby sections being a curved tapering surface and other of said sections forming a truncated pyramid, a point in said diaphragm at which a driving force is adapted to be applied, said point lying approximately at the center of inertia of the diaphragm.

7. In an acoustic diaphragm, a plurality of sections, at least two of said sections being curved surfaces, said curved surfaces being joined to one another, the junction of said surfaces forming rectilinear ridges in the surface of said diaphragm.

8. An acoustic diaphragm, a plurality of ridges in said diaphragm, said ridges comsaid polygonal ridge being located at a point which is equidistant from all of the points on the circle formed by said circular ridge.

9. An acoustic diaphragm, said diaphragm comprising a conical pyramid, a succession of right cross-sections of said pyramid gradually changing in shape from rectilinear outline to curvilinear outline.

10. An acoustic diaphragm having a truncated tapering surface, one cross section of said surface being curvilinear in form and another cross section being rectilinear in form.

'11. In an acoustic diaphragm, a plurality of sections, said sections comprising a curved central section, a curved peripheral section,

and a plane section,'said plane section lying intermediate said curved central section and said curved peripheral section. V

12. Irya sound amplifying device. a diaphragm, said diaphragm composed of a plurality of sections of different acoustic characteristics, one of said sections being a hybrid surface formed by merging a section of a cone and a section of a pyramid.

13. In an acoustic diaphragm. a curved surface, said surface merging from a surface having a curvilinear cross section into a surface having a polygonal cross section.

14. In an acoustic diaphragm, a plurality of sections, one of said sections being a curved tapering surface, said surface merging from a surface having a curvilinear cross-section into a surface having a rectilinear crosssection.

15. An acoustic diaphragm, said diaphragm having a plurality of sections, one of said sections being a curved tapering surface, said surface merging .from a surface having a curvilinear cross section into a sur face having a rectilinear cross section and a point in said diaphragm at which a driving force is adapted to be applied, said-point lying approximately the diaphragm.

16. A non-planar acoustic diaphragm having an openingin the surface thereof, said opening adapted to receive means for vibrating said diaphragm, and the center of mass of said diaphragm being located substantially Within said opening.

17. In an acoustic diaphragm, a plurality of sections, one of said sections being'a curved surface, said surface merging from a surface having a regular polygonal cross-section into a surface having an irregular polygonal cross-section.

18, A diaphragm for a sound amplifying device, said diaphragm comprising a central tapering section and a second tapering section surrounding said central section, said two sections having dissimilar outlines, one of said sections having a positive slope and the other of said sections having a negative slope with reference to the axis of said first mentioned tapering section.

19. In an acoustic diaphragm, a plurality 5 of sections, said sections comprising a curved surface and a plane surface, and a point in said diaphragm at which a driving force is adaptedto be applied, said point, lying approximately at the center of inertia of the diaphragm.

20. An acoustic diaphragm composed of a plurality of sections, said sections being bounded by ridges in the sufface of said diaphragm, said sections and said ridges forming a pointed star in relief.

21. An acoustic -diaphragm having a truncated tapering surface, one cross section of said surface being curvilinear in form and another cross section being rectilinear in form, and a point in said diaphragm at which a driving force is adapted to be applied, said point lying approximately at the center of inertia of the diaphragm.

22. In an acoustic diaphragm, a plurality of sections. one of said sections being a curved surface, said surface merging from a surface having a regular polygonal cross-section into a surface having a curvilinear cross-section.

23. A diaphragm for a sound amplifying device, said diaphragm comprising a plurality of sections, one of said sections being a curved tapering section having a positive slope and another of said'sections having a negative slope with reference to the axis of said curved tapering section, ridges formed at the junctions of said sections and polyhedral angles formed at the intersections of said ridges.

24. In a diaphragm, a plurality of surfaces, one of said surfaces being a curved surface, said surface lying remote from the center of the diaphragm, said surface being bounded on all sides by rectangular ridges.

25. In an acoustic diaphragm, a tapering surface, said tapering surface beng bounded by an inner ridge and an outer ridge, one of said ridges forming a continuous curved line and the other of said ridges forming a broken inertia of the diaphragm.

28. An acoustic diaphragm having a truncated tapering surface, successive cross sections taken perpendicular to the axis of said tapering surface gradually changing in shape from one outline to a dissimilar outline, and a point in said diaphragm at which a driving force is adapted to be applied, said point lying approximately at the center of inertia of the diaphragm.

29. A non-planar acoustic diaphragm, said diaphragm being provided with an opening in the surface thereof adapted to receive means for vibrating said diaphragm, and

said diaphragm being physically balanced about said opening.

30. An acoustic diaphragm, said dia-' phragm comprising a truncated conical pyramid, a succession of right cross-sections of said truncated pyramid gradually changing in shape from rectilinear outline to curvilinear outline.

31. An acoustic diaphragm, a plurality of ridges in said diaphragm, said ridges comprising a circular ridge, a regular polygonal ridge and an irregular polygonal ridge.

32. An acoustic diaphragm, a plurality of sections in said diaphragm, said sections comprising a central curved tapering section and a plane section, said curved tapering section having a positive slope and said plane section having a negative slope with reference to the axis of said curved tapering section.

33. In an acoustic diaphragm, a curved surface, said curved surface being bounded by an inner ridge and an outer ridge, one of said ridges being curvilinear 1n form and the other of said ridges having the form of a polygon.

34. In an acoustic diaphragm, a plurality of sections, one of said sections being a curved surface, said surface merging froma surface having a polygonal cross-section into a surface having a polygonal cross-section of a different number of sides than said first men tioned polygonal cross-section.

In witness whereof, I hereunto subscribe my name this 6th day of February, 1928.

EVERETT C. NILSON.

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