US 3172022 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
March 2, 1965 G. c. TIBBETTS TAPERED GAP MEANS FOR MAGNETIC TRANSLATING DEVICE Filed July 6, 1962 INVENTOR. 6622 06 6. jijzzf M W United States Patent Maine Filed July 6, 1962, Ser. No. 208,077 13 Claims. (Cl. 317-173) The present invention rel-ates to magnetic translating devices having a movable armature and capable of translating mechanical to electrical energy or vice versa due to the operation of variable gaps and variable magnetic fluxes, and more particularly relates to the orientation of the surfaces defining the gaps relative to the armature free end.
It is an object of this invention to provide optimum stability of the armature for all deflections of the armature of a magnetic translating device.
It is another object of this invention to provide means creating a magnetic field comprising gap-defining pole faces at angles relative to the opposing faces of the armature passing therebetween.
More particularly it is an object of this invention to orient the surfaces, forming the pole faces of the means creating the magnetic field at a vibratory portion of the armature, and the opposing faces of the armature at angles relative to each other such that the planes, in which the pole face surfaces lie, intersect the corresponding planes, in which the opposing faces of the armature lie, in lines which substantially define a plane such 1 that the virtual pivot axis of the armature lies substantially in the plane so defined. The latter plane is substantially perpendicular to the others, for very small gap angles. Insofar as the portion of the armature between the pole faces approximates a rigid body, the virtual pivot axis is so defined that said portion moves, under the action of magnetic forces, as if rigidly pivoted about said axis.
These and further objects will be apparent from the following description and drawings in which:
FIGURE 1 shows the general configuration of the invention;
FIGURE 2 is a view in section showing the invention utilized in a magnetic translating device;
FIGURE 3 is an enlarged view in perspective of the tapered pole pieces;
FIGURE 4 is an end view along line 44 of FIGURE 2 showing the tapered pole pieces defining the tapered gaps between the pole faces and the armature; and
FIGURES 5 and 6 show modified embodiments of the invention.
In its broad embodiment the present invention comprises means for defining a tapered gap relative to an armature so that with large deflections of the armature there will be optimum stability throughout the deflection. Thus the means may take the form of a pole piece inclined relative to the armature to create the tapered gap as shown generally in FIGURE 1 with pole piece 1 having pole face 2 at an angle to the armature 3; or may comprise a pole piece whose constant thickness extends parallel to the normal plane of the armature outside the projected area of the armature, but is recessed at a tapered angle relative to the armature in the projected area as shown in FIGURES 2 and 3. By choosing the angles as hereinbefore described, the gap closes or opens substantially sector-wise under the combined action of magnetic and external forces, the relative flux distribution in the gap remains substantially unchanged, and thereby the effective point of application of the magnetic forces remans substantially stationary relative to the armature, resulting in optimum "ice stability of the armature for all deflections. Closing sector-wise as used throughout the specification and claims shall be understood to mean that the closing surfaces form an angle whose apex does not move substantially as the surfaces close whereby the facing surfaces of the armature and poles reach substantial parallelism just as they touch.
The invention has application to the broad magnetic translating device of FIGURE 1 utilizing an armature 3 having some portion such as its end fixed relative to a base 4. In particular, the invention may be employed in electromagnetic transducers such as hearing aid microphones or receivers, and FIGURE 2 shows the invention utilized in the translating device 5 of copending application Serial No. 168,183, filed January 23, 1962. In that figure the pole pieces have end portions of constant thickness and parallel to the plane of the armature when centered, but have their central portions recessed to provide a taper relative to the armature. The armature 6 of the translating device is suspended at its uppermost end 7. In this case the virtual pivot axis is intermediate the upper and lower portions of the folded armature in a direction parallel to line 44, and is intermediate the pole pieces 1 and the folded portion 9 of the armature in a perpendicular direction. FIGURE 3 shows the magnets 8 of the translating device which extend laterally of the plane of the armature free end and have pole pieces 1 on their surfaces adjacent the armature, with the surfaces of the pole pieces being offset at a tapered angle as shown. FIGURE 4 is a further view of such pole pieces to indicate the relationship between the armature and the pole faces.
FIGURE 5 shows a modified configuration wherein the tapered gaps are formed by pole pieces llh-aving their pole faces adjacent the armature parallel to each other, with armature 12 having a tapered end to provide surfaces 13 defining the tapered gaps with the pole faces. Such configuration is the reverse of FIGURE 1. It is readily apparent that a configuration intermediate the extremes of FIGURES l and 5, having the pole faces non-parallel as in'FIGURE 1 and the armature end. surfaces non-parallel as in FIGURE 5, would also be effective as long as the angles were chosen as hereinbefore described.
FIGURE 6 depicts a further embodiment of the invention wherein the pole faces 14 are presented directly by the surfaces of the magnets 15, with no intermediate pole pieces. Since the flux-collecting and flux distribut ing functions of the pole pieces are omitted, the magnets preferably are tapered in the same sense as the gaps or otherwise processed so that they are elfectively thinner at their edges nearest the virtual pivot axis and progressively effectively thicker toward their edges away from said axis. For example, by having the taper of the magnet such that the ratio of magnet thickness to gap thickness remains substantially constant from point to point in the direction of the extent of the armature at center rest position, the relative flux distribution in the gap again remains substantially unchanged as the free end of the armature moves substantially sector-wise to- Ward or away from either magnet. It is apparent that the tapered gaps could be defined by similar tapered magnets whose adjacent gap-defining surfaces are parallel to each other but utilized with a tapered armature as in FIGURE 5, or any intermediate configuration with nonparallel magnets and armature surfaces as described above concerning FIGURE 5.
The drawings are exaggerated, and not intended to limit the invention to configurations having gaps with tapers as large as depicted.
Many modifications will be apparent to the artisan. It is obvious that the invention in its broadest aspects can n a magnetic translating device' including an armatur having a substantially rig'idly 'fi'ried portion and a vibratory portion, the improvement *comprising'means, efini'ng at' least one tapered gapbetween'thearmature sa'id translating-*dvice -a'ndmeans supplyinga mag n'etic field' irr the viciriity of a vibratoryregion of the armaturej-f closable substantially sectorwise, anddefining a substantially invariant-relative'fiuX distribution in said 'gap throughout deflections ot-"the armature, the first -"i1arr1'ed means comprising surfaces lying in respective planes intersecting in aline substantially fixed relative to arrd sp'aac'ed'from th fixed portion of the armature.
21 The improvement as recited inclaim l wherein' the first-nained'means comprise the surfacesofthe armature anathema-named means. I I
3. 1he improvement as recited in claim 1 wherein the rsenamed means comprisesat least-one surface of the ast-named-means. I 4. The-improvement recited in' claim 3 wherein the Y lastmar'ned means'comprisesat least one magnet.
5. "Theimprovement as recited-in claim4 wherein said -n1agnetis tapered=in the samesense as said gap.
' 6. '.l" he im' pavement as recited -in claim" 3 wherein eiid at least ne surface is at an angle-relative to'- the he improvement-as*recited in claim 6 whe'rein the" 's rfac? of the armature i adjacent said at--least one surface is also at an angle "relative'=to* the-general extent the first-named means comprises at least one pole piece forming'part ofsaid last-named means.
11. In a magnetic translating device including an armature having a substantially rigidly fixed portion and a vibratory portion, the improvement comprising means, including a vibratory region of the armature and a pole face presented thereto, defining a tapered gap therebetween, closable substantially sectorwise,-and defining a substantially invariant relative flux distribution in the gap throughout deflections of the armature, the plane in which lies the pole face and the plane in which lies the adjacent surface of said vibratory region of the armature intersecting in a line substantially fixed relative to and spaced from the fixed portion of the armature.
' 12. The improvement as recited in claim 11' including asecond means on the side of 'the'arm-ature opposite the first said means, and similarly including a pole face presented to the armature symmetrical with respect to the first-named pole face. a
13. In a magnetic translating device including'an armature having a substantially rigidly fixed portion and a vibratory portion; the improvement comprising magnets extending on opposite sides of the armature and presenting pole faces to a vibratory region of the armature such that theplanes inWhichlie' the pole faces and the planes in which Bethe-respective adjacent surfaces of said vibratory region of the armature respectively intersect References Cited by the Examiner UNITED STATES PATENTS 1,568,589 1 /26 Eddington 317-173 2,718,614 -9/s5 Gamble 317-171 2,754,685 7/56 Lansky '317171 2,941,130 6/60 Fischer 317-471 'FOREIGN PATENTS 1,052,458 37-59 Germany.
112,593 12/44 'Sweden.
LARAMIE E; ASKIN, Primary Examiner. E. JAMES SAX ,"JOHN F."BURNS, Examiners.