Патент USA US2127427код для вставки
‘Aug; 16, 1938. M. w. SCHELDORF 2,127,427 PERMANENT MAGNET GALVANOMETER Filed July 51, 1937 23 Inventor‘: ? , Marvel‘ W. Scheldor? 2,127,427 ‘ Patented Aug. l6, 1-938 Nl'l‘E stra'res PATENT OFFICE " ‘ _ 2.12am PERMANENT MAGNET oarvanonm'raa Marvel w. Scheldori', Schenectady, N. ‘ll., assign or to General Electric fllompany, a corporation I or New York . Application July or, 1937, Serial No. 156,732 f ‘ 4 Claims. My invention relates to permanent-magnet (Cl. I'll-95) it. The armature had a strong tendency to snap galvanouieters o! the balanced armature type. such as those employed in radio loud speakers, magnetic pick-up devices, electrocardiographs, % and the hire, is .1“. its object is to provide a gal vanonleter whose response is more nearly pro over against and bridge the pole pieces, the posi tion indicated in dotted lines, as soon as there was any" current flow in the exciting winding. This tendency was due largely tothe tendency of the armature to move to close the only air gap in the permanent magnet ?ux circuit, and portional to the variation of the current in its this tendency increased as the armature de; ‘‘ euciting winding than has been the caselwith parted from a'cent'ral position, making it im prior galvanometers of this type. ‘ practicable to offset‘this' magnetic pull by any W The ieatures oi the invention which are be simple restraining device. For, these reasons, the lieved to he novel and patentable will be pointed useful working range of the armature was quite out in the claims appended hereto. For a better and the de?ecting force dimcult to match understanding otmy invention, reference is made limited control by a restraining spring. in the ioilowing description to the accompanying and I have found that, if the permanent magnet 15 / it drawing wherein a side view ot a preferred em circuit is provided with additional air gaps, as, ‘hooliinent oi my invention is illustrated. for example, by, placing nonmagnetic spacers it Ili‘he fgalvanoineter illustrated is oi.‘ the bal and it between the permanent magnet ll arid. anced armature type. ‘It includes a pair oi U~ the pole-piece parts it and it, greatly improved shaped colt-iron pole-pieceparts it and it with results are obtained. The permanent magnet their open sides facing each other but separated must be of a larger size or produce a greater to provitle a relatively large armature air gap. total ?ux than before because now appreciable in which a magnetic vane armature it is sym metrically mounted. The armature is biased to a central neutral position by suitable restraining means which may comprise a torsional rod it it on which the armature is fixed at its center. The rotl iii may be clamped at one or both of its ends, one" such clamp being indicated bash oi the armature at it. an exciting winding ?ux leaks across between the pole pieces of the permaneutmagnet asindicated by the dotted lines til. However, the improved results more 26 than o?set the necessity of using a. stronger per ' 3“ made in two coils it and it surrounds opp lsite ‘ enol rtions oi‘ the armature it. These coils will .be connected'iu series and excited by a cur rent, such as the voice current of a radio loud spealter, tending to poiarize the vane armature it in the direction oi its length. Also a mirror it$1 it moved by the armature and a light ray indi cating system such as a lamp ti and scale it ay he used. _ ‘ , A horseshoe-shaped permanent magnet ii is m provided to create a unidirectional magnetome tive torce between the pole pieces of the two parts it and‘ it as indicated by the designa tions “it” and “S”. manent magnet. ' > It is evident that, with no" reluctance gap or its equivalent at it and it when there is a de ?ection oi the armature from neutral position 30 maximum reluctance, the permanent magnet ?ux increases and the magnetic pull on the armature increases not only because of the reduction‘in armature air gap reluctance wlth'deflectlon but also because of the increase in permanent-mag net. ?ux with such decrease in reluctance; that ' is, there is‘ a building up force condition that is dimcult to control. ' By increasing the reluctance of the permanent magnet ?ux circuit by the air gap at it and it, the relative decrease in total reluctance of the magnetic circuit by movement-of the arms. ture from neutral is of a much lower order than it now the excitation of "before and the increase in permanent magnet coils ill and ii is such as to polarize the arma ?ux is correspondingly less. The change in re ture to produce a south pole at its right end and luctance of the magnetic circuit due to rotation .45 north pole at its left end as indicated; the arma of the armature from maximum reluctance to a ture willtend to twist counterclockwise and, ii’ lower reluctance position is thus minimized. The the exciting current is reversed, it wlll‘tend to instability of the armature is materially deéreased turn in the‘ opposite direction against the re straining iorce of‘ the torsional shaft l3. “ ' 5 in the prior art device of this type, the perma nent magnet ll abutted directly against the soft iron pole-piece parts it and it so that the only air gap of any consequence in the permanent ‘ 55 magnet circuit was the gap between the pole pieces it and it. _ Such prior art arrangement, while operative, was not very satisfactory for - some purposes because the armature was quite unstable except, of course, in a central position ,60 with no exciting current ?owing in coils liand and its sensitivity to current variations and its . magnetic. regulation characteristics greatly im proved. ‘It is possible to secure much better re sults by using a large magnet at ‘H with the air gap at It and i9 than with a magnet weak enough to place directly on the pole-piece parts, it and it without encountering instability. The relative dimensions of the parts and of ~‘the air gaps shown in the drawing are satisfac tory, but the invention; is by no means limited to the relative dimensions illustrated. The total o 2 2,127,427 length of air gap in series at 18 and I 9 should preferably be not greater and may be less than the length ‘of air gap between the north and south pole pieces of the galvanometer with ar a mature I! in the neutral position. The total length of air gap in the useful flux path should cuit excited by a permanent magnet and having pole pieces defining an air gap, a magnetic vane armature movably supported in said gap, means for resiliently biasing said armature to a neutral position of maximum reluctance in the flux path across said air gap, and an exciting winding which, when energized, polarizes said armature obviously not be greater and should preferably be less than the leakage flux gap at 20. With the relative dimensions shown» in the drawing, causing it to turn against its bias to a lower reluctance position, said magnetic circuit con taining an additional appreciable and intentional 10 there is a negligible change in flux density across the armature air gap when the armature l2 air gap for the purpose of minimizing the per manent magnet ?ux change in said magnetic circuit whichis due to the movement of said _ moves from the neutral to an extreme position, and this useful flux is comparable in magnitude to'the leakage of flux of the permanent magnet II, the greater portion of which traverses the _. armature to a lower reluctance position. 2. A galvanometer having a magnetic circuit path indicated at 20. If I make gaps I8 much larger in proportion to the other gaps than here represented, bene?cial results as regards sta containing an armature air gap and a perma nent magnet for producing a ?ux across said air gap, a magnetic vane armature pivoted in said bility will still be obtained but this will call 20 for a further increase in the size, strength and cost of the permanent magnet that ceases to be justifiable. The particular air gap dimen sions and strength of flux to be used in any par ticular case will depend upon the degree of sta bility and sensitivity desired and the use for which the device is intended. 'The strength of the permanent magnet used may be such that the flux density in the useful air gap is increased in comparison to prior gal vanometers of this general type. In such prior devices it, was the practice to fit the pole pieces _ such as H and I! to the permanent magnet as perfectly as possible. The result was that any increase in ?ux strength for the purpose of in pieces separated by an air gap, a permanent I intentionally provide air gaps at points i8 and I9 and increase the strength of the perma nent magnet used, but I do not wish to limit my invention to any particular gap dimensions and maximum reluctance with respect to the per 40 strength of permanent magnet because any ap- ' reasonable increase in size and cost of the per manent magnet. In accordance with the usual practice, the magnet i1 is made of high grade permanent mag . net material and is permanently magnetized to The 50 provide an efiicient permanent magnet. pole pieces l0 and II are made of soft iron and the armature I2 is preferably made of the best grade of soft, high permeability magnetic ma terial obtainable. m) By means of my invention, the useful range of vibration of the armature is increased, its de ?ection is more nearly proportional to the exci tation current, and a more suitable restraining spring may be used. It is evident that the structural relation of the parts may be materially changed without de parting from the principle of the invention. In accordance with the provisions of the patent statutes, I have described the'principle of opera tion of my invention together with the apparatus which I now consider to represent the best em bodiment thereof but I desire to have it under stood that the apparatus shown is only illus trative and that the invention may be carried 70 out by other means. . What I claim as new and desire to secure. by Letters Patent of the United States is: 1. A galvanometer comprising, a magnetic cir-» additional appreciable and intentional air gaps to minimize the change in reluctance of the magnetic circuit caused by such movement of 30 said armature. 3. A galvanometer comprising, soft-iron pole magnet for producing a unidirectional ?ux be tween said pole pieces across said ,gap, a magnetic vane-armature pivoted in said air gap, a spring biasing said armature to a neutral position of 85 creasing sensitivity also decreased the stability. preciable gap at the points l8 and i9 improves the relation between sensitivity and stability and is highly beneficial ‘up to the point where this expedient becomes impracticable due to an un , air gap, said vane being resiliently biased to a neutral maximum reluctance position with re spect to the permanent magnetic flux crossing 20 said gap, and an exciting coil which, when ener gized, polarizes said vane causing itto turn from a neutral maximum reluctance position against its bias to an unstable lower reluctance position with respect to the permanent magnet ?ux cross ing said air gap, said magnetic circuit including manent magnet ?ux crossing said gap, said ar mature being movable in opposite directions from such position to lower reluctance positions in 40 cluding positions where it may bridge said pole pieces, an exciting winding which, when ener- ‘ gized, polarizes said magnetic vane armature. causing it to turn from its neutral position to intercept more of the permanent magnet ?ux crossing said gap and lowering the reluctance of said magnetic circuit, and nonmagnetic spacers between said permanent magnet and said soft iron pole pieces for the purpose of minimizing the change in reluctance of the magnetic circuit ' due to such movement of said armature. 4. A galvanometer comprising, pole pieces sep arated to form an armature air gap, a permanentv magnet forming with said pole pieces a magnetic. circuit for producing a unidirectional flux across said gap, a magnetic vane armature pivoted at its center in the center of said gap, resilient means for biasing said vane to a neutral maxi mum reluctance position with respect to the ?ux crossing said air gap but permitting the vane 60 to turn in either direction from such position to lower reluctance positions including positions where the‘vane may bridge said pole pieces, the ’ permanent magnet being of horseshoe shape and being magnetically spaced from the pole pieces 85 by reluctance gaps permitting a substantial leak age ?ux between its pole pieces which does not cross the armature air gap, and a coil which, when energized, polarizes the magnetic vane ar mature and causes it‘ to-de?ect from its neutral position.