US2427805A - Carbon pile voltage regulator - Google Patents

Description

Sept. 23, 1947. w. G. NEILD 2,427,805

WilliauwG. IVeild.

Sept. 23, 1947. w. G. NEILD 2,427,305

CARBON FILE VOLTAGE REGULATOR Filed Dec. 27, 1944 4 SheetsSheet Fig.2.; fg e ii 10 v A 16 1 V t r Fig-5- W95 OI still:

WI I" 66 gunman/(o0 William G. lveilab.

Sept. 23, 1947. w. G. NEILD 2,427,305

CARBON PILE VOLTAGE RBQULA'I'OK Filed Dec. 27, 1944 4 Sheets-Sheet 3 INVE'VI'UIL yilliam a Arromvzv MIX-1 Sept. 23, 1947. w. a. NEILD 2,427,305

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Patented Sept. 23, 1947 UNITED STATES PATENT OFFICE cannon PILE VOLTAGE REGULATOR Application December 27, 1944, Serial No. 570,002

8 Claims.

The present invention deals with electrical regulators and is concerned primarily with regu1ators of the so-called carbon pile type.

At the present time carbon pile regulators have come into widespread use for such purposes as controlling the voltage of the output of generators and also in the governing of current.

All of these carbon pile regulators operate on the principle of varying the pressure applied to the carbon pile; the range of effective pressure on the pile being the regulating range of the regulator.

There has now come into fairly widespread use a regulator which is characterized as including the usual carbon pile, one end of which is relatively fixed. Operatively associated with the other end to apply pressure on the pile, is an armature and this armature is carried by a spring of the leaf type having a plurality of spring fingers which engage at the extremities thereof, an inclined abutment formed on the electromagnet.

The force of the electromagnet is rendered effective on the armature, and the spring above referred to, tends to urge the armature towards the pile, while the magnetic force tends to withdraw the armature from the pile and to force the spring fingers into abutting relation along the inclined surface of the abutment provided on the electromagnet so as to approximately vary' the force exerted by the spring inversely as the square of the distance between the armature and magnet so as to effect basic correspondence with varying magnet full results.

With carbon pile regulators of this type considerable mechanical difficulty has been experienced in obtaining desired regulating effects due to the difficulties incident to calibrating the several spring fingers to the inclined abutment, so as to give the effect desired. Moreover, the latter spring has a characteristic which outside its normal limited working range and with lower forces is quite different from that within its limited working range. Thus upon wear of the carbon pile which inevitably results through use, this latter characteristic often results in high voltage and consequent failur of control and damage to the electrical system.

An object of the present invention, therefore, is to simplify and improve the aforenoted spring construction.

Another object of the invention is to provide a novel leaf spring construction having a first spring surface inclined at an angle to a first abutment surface provided on an armature plate and a second spring surface inclined at an angle to a second abutment surface and the said spring surfaces being so arranged as to wrap upon the respective abutment surfaces so as to substantially vary the force exerted by the spring on the carbon pile approximately inversely as the square of the distance between the armature and magnet so as to effect basic correspondence with varying magnet pull results.

Another object of the invention is to provide 5 a novel leaf spring arranged to wrap upon the under surface of an armature plate so as to provide the desired regulating effect.

Another object of the invention is to provide a novel spring construction having a relative wide operating range so as to compensate for severe wear of the carbon pile and thereby prevent a rise in voltage under such conditions.

Another object of the invention is to provide a novel mounting for the armature including a leaf spring forming a frictionless hinge for the armature and having an end portion wrapping upon an abutment surface so as to progressively increase the resistance of said spring to displacement of the armature by an electromagnet.

Another object of the invention is to provide a novel ring providing a mounting means for the armature and having an inner wall surface forming an abutment for the spring, and said ring being formed of a material having a relatively high coefficient of expansion so that the expansion nd contraction of the ring due to changes in temperature will adjust the spring through the abutting surface of the inner wall so as to compensate for those changes in the resistance of the carbon pile and in electromagnetic force act ing upon the armature due to change in the resistance of the electromagnetic winding caused by variations in temperature.

Another object of the invention is to provide a novel armature, leaf spring and mountin ring assembly whereby one end of the leaf spring is fastened to the ring and armature in such a manner as to form a frictionless hinge for the armature, while the other end is preformed so that when assembled a first portion of the end lies tangent to the perpendicular inner wall surface of the ring, while a second portion of the spring lies tangent to the horizontally extending under surface of an armature plate. The leaf spring is further so arranged that an electromagnetic force applied to the armature against the biasin force of the leaf spring causes the points of tangency of the leaf spring to move up the inner wall surface of the mounting ring and 50 out the under surface of the top plate of the armature so as to progressively increase the resistance of the spring to displacement of the armature.

Another object of the invention is to provide 55 a main leaf spring and a novel auxiliary leaf spring so arranged in relation to the main leaf spring as to change the spring rate acting upon the armature.

Another object of the invention is to provide 60 a novel main spring for counteracting the bias- 3 ing force of an electromagnet on an armature, and an auxiliary spring acting upon said armature jointly with said main spring within a predetermined operating range.

Another object of the invention is to provide on the regulating spring a novel dynamic vibration damping means, including two pendulous weights mounted at opposite sides of the armature by spring hinges so as to minimize the effects of severe external shocks.

These and other objects and features of the invention are pointed out in the following description in terms of the embodiments thereof which are shown in the accompanying drawings. It is to be understood, however, that the drawings are for the purpose of illustration only, and are not designed as a definition of the limits of the invention, reference being had to the appended claims for this purpose.

In the drawings, wherein reference numerals refer to like parts throughout the several views:

Figure 1 is a longitudinal sectional view of the carbon pile regulator constructed in accordance with the present invention with certain parts broken away to better illustrate the novel leaf spring structure.

Figure 2 is a modified form of the invention of Figure 1.

Figure 3 is a fragmentary view of Figure 1 showing the operation of the novel leaf spring as the armature is forced toward the electromagnet.

Figure 4 is a top plan view of the spring assembly of Figure 1 and somewhat reduced in size.

Figure 5 is a perspective view of the novel leaf spring illustrating the manner in which the wrapping end portions of the spring is preformed.

Figure 6 is a top plane of a third modified form of the novel spring assembly.

Figure 7 is a perspective view of the novel spring used in the form of the invention shown in Figure 6.

Figure 8 is a fragmentary sectional view taken along the lines 8-8 of Figure 6.

Figure 9 is a fragmentary view illustrating the mode of operation of the novel spring of Figure 6.

Figure 10 is a view of Figure 11 illustrating the wrapping action of the novel spring on the under horizontal surface of the top plate.

Figure 11 is a fragmentary view illustrating the manner in which the end of the spring is preformed.

Figure 12 is a view illustrating graphically a comparison between the spring characteristics of the several leaf springs herein described.

Figure 13 is a. view illustrating graphically the effect on the regulated voltage of variance in the adjustment of the carbon pile by wear or other causes.

Referring to Figure 1, it will be seen that there is provided a frame I having attached thereto by screws 2 a plate 3. Screw threadedly aifixed to the plate 3 is a magnetic core 4 which projects through an electromagnet winding 5 also carried by the plate 3. The core 4 is fastened in position by screws 6. A casing I encloses the electromagnet and a suitable annular member I5 isfreely mounted upon the casing |0 permitting a limited expansion and contraction of the member I5 in response to changes in temperature. The member I5 is preferably in the form of a die cast aluminum ring having a relatively great temperature coefllcient of expansion.

The annular member 5 is fastened to the plate 3 through suitable screws I6, one of which is shown in Figure 1. The screws l6 project freely through openings H in the ring I5. Screws I9 extend freely through openings 20 formed in a plate 2|, one of which is shown in Figure 1, into screw threaded engagement with ring IS. The screws I9 are fastened at the opposite end by nuts 23. The screws I9 are preferably formed of a material having a very low temperature coefficient of expansion and may be formed for instance, of the nickel iron alloy sold under the trade name of Invar.

Formed integral with the plate 2| is a carbon piie housing 24 having heat radiating fins 25. The housing 24 has a flange 25 provided at the opposite end from the plate 2|. The ring I5 is formed with an annular recess or cylindrical boss 21 disposed within an annular recess or chamfered end portion 28 of the flange 28 and in circumspaced relation therewith to permit radial contraction and expansion between the boss 21 of the ring I5 and the chamfered end portion 28 of the flange 26 without effecting a clrcumbinding thereof. The flange and ring are further disposed in sufficient spatiality to preclude engagement of the adjacent face of the ring with the flange of the housing upon longitudinal expansion of the housing in response to a rise in temperature.

It will be noted, however, that since the rods I9 have a very low temperature coemcient of expansion, the distance between the plate 2| and the ring I5 will remain relatively constant, since the same are fastened in spaced relation by the rods l9.

Fastened to the plate 2| at the exterior surface thereof by suitable screws, not shown, is a second plate 30. The plate 35 is insulated from the plate 2| by a suitable insulating member 3|. There is fastened to the plate 30 by a bolt 35 and nut 35, a cap 31 in which is screw threadedly engaged a screw 40 locked in position by a suitable fiat spring lock indicated by the numeral 39. The screw 40 has a cleft portion 4| accessible from the exterior.

An electrical conductor 42 is connected to the cap 31 by the nut 36 and through the cap 31 to the nut 40. Mounted in the housing 24 and extending longitudinally therein is a non-conducting tube 45 of a suitable refractory material, such as porcelain. Tube 45 is retained in place by a member 48 engaged in a groove 49 formed in the tubular member 45. The member 48 is attached to the plate 2| by a screw 50. The tubular member 45 carries carbon discs 55 forming a carbon pile. Contactor members 56 and 51 are positioned at opposite ends of the carbon pile 55.

The screw 40 is turned so as to adjust the contactor 55 and thereby the initial contact pressure between the carbon discs 55.

The contactor 51 provided at the opposite end of the carbon pile 55 is mounted in a cup shaped securing member 60 formed in an electrical conductor plate 6|. An electrical conductor 62 leads from the conductor plate 6|.

The conductor plate GI and the contactor 51 is biased under force of a novel spring biased armature plate assembly indicated generally by the numeral 55 in a direction toward the carbon pile 55.

The novel spring biased armature, plate assembly, includes a top plate 65 and bottom plate 61 positioned at opposite sides of a novel leaf spring I formed of a. suitable material and preferably a spring steel having a relatively low temperature coefficient of expansion. The top plate 65, bottom plate 61 and leaf spring III are fastened to an armature 15 by bolts 16. The plate is attached by screw 18 to the top plate 66, bottom plate 61, spring and armature l5 and is insulated therefrom by insulating plate 19, insulating bushing 80, and washer 8|. Separating the magnet case in and ring I5 across the air gap between the magnet 4 and armature extends a suitable non-magnetic member 83 preferably formed of brass for providing means for limiting the minimum magnetic gap between the armature and magnet case to prevent sticking of the armature 15 at the extreme minimum air gap position.

The novel leaf spring I0, shown in Figure 1, is clamped at one end by a bar 85 and securing screws 86 to the annular member I5, as shown in Figure 4, so as to form an antifrictional hinge for the armature assembly.

The novel leaf spring 10, as shown in Figure 5, has the opposite end portion 90 preformed with two gradual curved bends at 9| and 92, the bend at 9| being formed with a greater radius than the bend at 92.

The novel leaf spring 10 is positioned in the annular ring I5 so that an end portion 95 rests upon the horizontal surface of the member 83, while the surface between the end 95 and the bend 92 lies either tangentially along the vertical inner wall surface of ring l5 or at an angle thereto, depending upon the compressive force applied to the spring 10. Likewise, the surface between the bend 92 and 9| lies either tangentially along the under surface of the top plate 56 or at an angle thereto, depending upon the compressive force applied to the spring 10.

As the electromagnetic force of the electromagnet 5 increases, the armature 15 is drawn toward the core 4 decreasing the air gap between the core 4 and the armature 15. As the force thus exerted on the armature 15 increases, the end portion 90 of the spring 10, wraps along the inner surface of the ring l5 and along the under surface of the top plate 66, as shown in Figure 3.

The end portion 90 of the spring 10 thus wraps upon the abutment surface provided by the inner surface of the ring I5 and the under surface of the plate 56, and the length of the portion 90 of the spring 10 subjected to further bending as the armature 15 moves further toward the electromagnet 5, continuously decreases. The spring thus shortens and becomes stiffer as the length of the air gap between the armature 15 and electromagnet 5 lessens. Through appropriate design of the portion 90 of the spring "ill in relation to the abutment surfaces, the resistance of the spring 10 may be readily made to approximately vary inversely as the square of the distance between the point of application of the magnet pull to the spring and some fixed datum point which corresponds with the zero length of air gap. Except for the relatively small force needed to adjust the pile through adjustment screw 40 the total pull of the magnet 5 balances the pressure exerted by the spring Ill.

The regulator of the present invention is particularly adapted for use as a regulator to maintain a constant voltage in a circuit. As an example, the carbon pile 55, as is well known in the art, may be connected through the conductors 42 and 62 in series with a shunt field winding of a generator, while the winding 5 of the electromagnet is connected in series with an adjustable ballast resistance across the output terminals of the generator. Thus if the voltage at the output rises, the electromagnet 5 adjusts the armature 15 so as to decrease the pressure on the pile 55, increasing the electrical resistance of the pile 55 so that the field is reduced and the output voltage is reduced to the desired value. A decrease in the voltage at the output would cause an opposite effect, increasing the voltage to the desired value.

Thus variations in the regulated voltage will effect the magnet 5 to adjust the carbon pile 55 through the leaf spring 10 and armature 15 so as to vary the resistance afforded thereby and maintain the regulated voltage at the desired constant value. The novel spring Ill will progressively increase the resistance of said spring to displacement of the armature 15 toward the electromagnet 5.

It will be further noted that an error may be introduced into the regulator due to the effects of variations in temperature upon the resistance of the carbon pile 55 and the resistance of the electromagnet winding which preferably, is wound of copper wire. In order to eliminate the latter errors there has been provided the annular member l5 having a greater temperature coefficient of expansion than the spring 10 mounted therein. Thus upon an increase in temperature radial outward expansion of the member [5 will be effected, decreasing the pressure setting of the spring 10 so as to compensate for a decrease in the electrical resistance of the carbon pile 55 and a decrease in the biasing force of the electromagnet 5 for a given voltage. The latter decrease in the force of the magnet 5 may be effected by an increase in the resistance of the copper winding due to an increase in temperature. A decrease in temperature would, of course, have an opposite effect upon the carbon pile 55, copper winding of the electromagnet 5 and the annular member l5.

Since a rise in temperature will effect a decrease in the resistance of the carbon pile 55, it will be readily seen that the annular member l5 will also compensate for the effect of temperature variations on the carbon pile 55 by varying the tension acting on the carbon pile 55 in response to temperature change.

In Figure 2, there has been shown a modified form of the invention in which like numerals indicate like partsto those previously described with reference to Figure 1.

In the latter form of the invention there is provided an auxiliary leaf spring I00 positioned between the main leaf spring 10 and the top plate 66 and attached to the armature I5 by the bolts 16 and 18. One end of the auxiliary leaf spring 10 is clamped to the annular member i5 by the bar and screws 85.

The opposite end portion illi of the auxiliary leaf spring I00 extends at an angle to the under side of the top plate 66 and is bent on such a radius as to bear upon the end portion of the spring 10 to effect a desired increase in the spring resistance to movement of the armature 15 within a minimum electrical resistance range of the pile 55 and thereby decrease the minimum electrical resistance of the pile 55 within the latter regulating or operating range.

Thus within such operating range, the auxiliary leaf spring i0i effects a change in the spring rate acting upon the armature 15. As the arma ture I5 approaches the zero air gapposition the leaf spring 15 wraps along the inner surface of the annular member 15 and the auxiliary spring ill, compressing the spring iiil toward the top plate 55 against the tension thereof so that at the high electrical resistance end-of the carbon pile 55, the auxiliary spring I50 has no effect. Through this latter arrangement there is provided a spring characteristic, whereby upon movement of the armature I5 towards the maximum air gap position, a biasing force is produced which more nearly approaches the force produced by the electromagnet 5 plus the pile force, which latterforce becomes quite large within the minimum electrical resistance operating range as compared with a relative low pile force within the maximum electrical resistance operating range.

In this connection, it should be noted that for ideal operating conditions the force exerted by the leaf spring 10 of Figure 1 or the combined forces of the main leaf spring 10 and the auxiliary leaf spring llii of Figure 2 acting upon the armature 15 should equal the counter balancing biasing force of the electromagnet 5 plus the inherent biasing force of the carbon pile 55 at the desired regulated voltage. If the force exerted by the spring means 10, or 15 and llil exceeds the force exerted on the armature 15 by the electromagnet 5 and the carbon pile 55 at the desired regulated voltage, it will be readily seen that the force of the spring means will cause a further biasing force to be exerted on the carbon pile 55 decreasing the electrical resistance thereof so as to cause a regulated voltage above the desired value. However, if the force exerted by the spring means be less than the force exerted on the armature 15 by the electromagnet 5 and carbon pile 55 at the desired regulated voltage, it will be readily seen that the force of the electromagent '5 will decrease the biasing force exerted on the carbon pile 55 below that required to efiect the desired voltage and thereby increase the electrical resistance thereof, to cause a regulated voltage below the desired value.

As the armature I5, approaches the extreme open air gap position, it is desirable to maintain the biasing force exerted by the spring" means less than the force exerted by the electromagnet 5 at the predetermined voltage value, rather than in excess thereof, so as to assure a regulated voltage within the latter limited range less than the predetermined constant voltage, but not in excess thereof.

Through this latter arrangement considerable wear of the carbon pile 55 is permitted without excessive voltage conditions resulting. In the arrangement in Figure 1, this condition is provided by properly positioning the left hand end of the under plate 61 in relation to the spring I and adjacent end of the top plate 55. It has been found that by adjusting the position of the under plate 51 toward the adjacent end of the top plate 56, the biasing force of the leaf spring ill in this latter range is decreased. It is desirable to position the end of the under plate 51 so that the latter biasing force of the spring 10 will be only slightly less than that provided by the electromagnet for the desired regulated voltage.

In the form of the invention shownin Figure 2, it will be readily seen that as the armature 15 moves to the extreme open air gap position the end portion 90 of the spring is biased under the force of the end ilil of the auxiliary spring I05, so that the end illl within the latter limited operating range augments the biasing force of the leaf spring 10. Thus within'the latter limited operating range of the leaf spring II and auxiliary spring III, the force exerted by the spring II on the armature II will more nearly approach a condition where the same will equal the force exerted by the electromagnet I plus the inherent biasing force of the carbon pile 55 at the desired regulated voltage.

Moreover, in the forms of the invention shown in Figures 1 and 2, it has been found desirable just beyond the maximum practical electrical resistance operating range of the carbon pile 55 to have the spring 15 arranged so as to provide a biasing force in excess of that provided by electromagnet 5, plus the inherent force of the carbon pile 55 at the desired regulated voltage. The effect of this provision is that the spring 15 provides a snubbing action that resists adiustment of the carbon pile 55 to a higher electrical resistance than the practical operating range of the carbon pile 55 by forces other than the regulated forces, as for example external shocks.

In the form of the invention shown in Figure 2, there is also provided a dust-tight cover ilil which encloses the armature assembly within the annular member i5. An annular groove H5 is provided in the member i5 for receiving an annular edge of the cover cap iill positioned in a suitable sealing ring I IS. A suitable orifice H1 is formed in the cover cap for receiving an end of the tubular member 45 of the carbon pile 55. The cover cap H0 is fastened to the annular ring l5 by the bolts IS.

A third form of the invention is shown in Figures 6 through 10, in which, like numerals indicate like parts to those indicated in Figure 1.

In the invention shown in Figures 6, 7 and 5, there are provided on the leaf spring 15 laterally projecting ears or spring hinges I" to which there are riveted at opposite sides, suitable weights indicated by the numerals I25 and ill. The weights I25. and I25 provide a dynamic vibration damping means to minimize the eifect of severe external shocks on the regulator.

It will be further noted, that the leaf spring II is arranged, as shown in Figures 9 and 10, so as to wrap only on the surface of the leaf spring between the bend 9i aid 92 along the under surface of the top plate 65 as the armature 15 moves toward the zero air gap position. Moreover, the leaf spring 10 is so arranged that the end 55 merely pivots at the junction of the inner wall of the annular member i5 and the member 55 during the movement of the armature 15, without a wrapping action along the inner surface of the annular member i5. However, by the proper selection of the spring Ill and position of the same in relation to the under surfaces of the top plate 55, a similar regulating effect may be produced to that previously described with reference to Figure 1.

From the foregoing it will be readily seen that there has been provided a novel armature leaf spring assembly in which one end acts as a frictionless hinge, while the other end portion is preformed, as previously explained, and arranged to wrap upon an abutment surface so as to progressively increase the resistance of the leaf spring to displacement of the armature by eletromagnetic forces.

Moreover, there has been provided a novel spring assembly arranged to operate upon severe wear of the carbon pile.

Moreover, there has been further provided a novel means for compensating for the effects on the regulator caused by changes in temperature.

Furthermore, in Figures 12 and 13 there has been illustrated graphically, a comparison of the operating characteristics of the leaf springs hereinbefore described.

In Figure 12, the dotted line A indicates an approximation of an ideal spring characteristic in which the spring force is always equal to the sum of the electromagnetic force plus the pile force at the desired regulated voltage. Line B indicates a'regulator where the spring force exceeds the sum of the pile force plus the magnetic force at the desired regulated voltage as the armature approaches the maximum air gap position. Line C indicates the spring characteristic of a regulator such as shown in Figure 1 where there is provided a spring in which the spring force is loss than the sum of the forces exerted by the magnet and pile at the desired regulated voltage as the armature approaches the maximum air gap position. Thus in the latter device as the pile wears, the regulated voltage decreases, rather than increases as in the case if a regulator having a spring characteristic such as indicated by the line B. The line D indicates the effect of the second spring of Figure 2, which causes the spring force to more nearly approach the ideal condition indicated by line A.

Figure 13 illustrates graphically, by the lines B-I and B2, the operation of a typical carbon pile regulator such as heretofore well known in the art, when used to control the shunt field of a generator so as to regulate the terminal voltage of the generator, as compared with the operation of the novel regulator of the present invention, indicated by lines C--l and C2 in regulating in a similar manner the terminal voltage of such a generator.

The lines 3-! and B--2 indicate the effect on the terminal voltage by operation of a carbon pile regulator having an armature spring with characteristics such as shown by line B of Figure 12, upon adjustment of the pressure acting on the carbon pile by wear or other causes as indicated graphically in Figure 13.

The lines Ci and C-2 indicate the effect on such terminal voltage through wear on the carbon pile of a regulator having an armature spring with a spring characteristic such as shown by line C of Figure 12.

The lines Bi and C-I indicate such effect under conditions of a fifty ampere load on the generator and lines 3-! and C2 indicate the effect under no load conditions.

It will be readily seen that a decrease in the pressure exerted on the carbon pile from the point of adjustment indicated on Figure 13, represents a comparable adjustment due to wear on the carbon pile.

The lines Bl, B2, C--l and C-2 illustrate graphically the carbon pile wear permitted Without detrimental rise in the regulated voltage by the respective regulators under the conditions specified.

It will be readily seen from Figure 13 that the novel regulator of the present invention allows greater wear or longer life without permitting the regulated voltage to rise above allowable limits and with greater stability of operation.

Although only three embodiments of the invention have been illustrated and described, various changes in the form and relative arrangement of the parts which will now appear to those skilled in the art ma be made without departing from the scope of the invention. Reference 10 is therefore to be had to the appended claims for a definition of th limits of the invention,

What is claimed is:

1. In an electrical regulator of the type includ ing a variable electrical resistance means, an electromagnet, an armature movably mounted in relation to said electromagnet, means connecting the armature to the variable electrical resistance means, said electromagnet biasing said armature in a direction for increasing the electrical resistance of said variable electrical resistance means; the improvement comprising a leaf spring, first and second plate members, said leaf spring fastened between said first and second plate members and to said armature, an annular member mounted on said electromagnet, said leaf spring positioned within said annular member and extending diametrically across said annular member, one end portion of said leaf spring fastened to said annular member so that said leaf spring forms a flexible hinge for said armature, the other end portion of said leaf spring bearing upon said electromagnet and in such a manner that one part thereof extends at an angle to the inner surface of said first plate member and another part thereof extends at an angle to the inner surface of said annular member, said parts of said leaf spring wrapping tangentially upon said surfaces as said armature moves toward said electromagnet so as to progressively increase the resistance of said leaf spring to displacement of said armature by said electromagnet.

2. In an electrical regulator of the type including a variable electrical resistance means, an electromagnet, an armature movably mounted in relation to said electromagnet, means connecting the armature to the variable electrical resistance means, said electromagnet biasing said armature in a direction for increasing the electrical resistance of said variable electrical resistance means; the improvement comprising a. leaf spring having a relatively low temperature coefficient of expansion, first and second plate members, said leaf spring fastened between said first and second plate members and to said armature, an annular member mounted on said electromagnet, said leaf spring positioned within said annular member and extending diametrically across said annular member, one end portion of said leaf spring fastened to said annular member so that said leaf spring forms a flexible hinge for said armature, the other end portion of said leaf spring bearing upon said electromagnet and being formed in such a manner that one part thereof extends at an angle to the inner surface of said first plate member and another part thereof extends at an angle to the inner surface of said annular member, said parts of said leaf spring wrapping tangentially upon said surfaces as said armature moves toward said electromagnet so as to progressively increase the resistance of said leaf spring to displacement of said armature by said electromagnet and said annular member formed of a material having a relatively great temperature coefficient of expansion so that the position of the inner surface of said annular member varies with temperature for adjusting said leaf spring.

3. An electrical regulator, comprising, in combination, a variable electrical resistance means, an electromagnet, an armature movably mounted in relation to said electromagnet, means connecting the armature to the variable electrical resistance means, said electromagnet biasing said armature in a direction for increasing the elec- 11 trical resistance of said variable electrical resistance means, a spring member for biasing said armature in an opposite direction for decreasing the electrical resistance of said variable electrical resistance means, a ring like element, said spring member positioned within said ring like element and extending diametrically across said element,

one end of said spring fastened to said element and the opposite end bearing on the inner surface of said element and resting upon the electromagnet, and a portion of said opposite end of said spring wrapping tangentially upon the inner surface of said ring so as to progressively increas the resistance of said spring to displacement of said armature by said electromagnet. 4. An electrical regulator, comprising, in combination, a variable electrical resistance means, an electromagnet, an armature movably mounted in relation to said electromagnet, means connecting the armature to the variable electrical resistance means, said electromagnet biasing said armature in a direction for increasing the electrical resistance of said variable electrical resistance means, a spring member for biasing said armature in an opposite direction for decreasing the electrical resistance of said variable electrical resistance means, a ring like element, said spring member positioned within said ring like element and extending diametrically across said element, one end of said spring fastened to said element and the opposite end bearing on the inner surface of said element and resting upon the electromagnet, and a portion of said opposite end of said spring wrapping tangentially upon the inner surface of said ring so as to progressively increase the resistance of said spring to displacement of said armature by said electromagnet, and a second spring for varying the spring rate of said first spring member within a predetermined operating range.

5. An electric regulator comprising a carbon pile, an electromagnet mechanically attached to one end of said pile, an armature for said electromagnet, a flexible sheet metal spring member, means connecting said armature and spring together and to the other end of said pile, so that movement of the armature towards the electromagnet is opposed by the biasing force of said spring member, and the pile is subjected to a compressive force equal to the difference between the pull of the electromagnet and the spring pressure, portions of said spring member projecting laterally from said member, and pendulous weight afllxed to said projecting spring portions and at opposite sides of the armature to dampen the vibration of said spring member.

6. An electrical regulator, comprising, in combination, a variable electrical resistance means, an electromagnet, an armature movably mounted in relation to said electromagnet, means connecting the armature to the variable electrical resistance means, said electromagnet biasing said armature in a direction for increasing the electrical resistance of said variable electrical resistance means, a spring member for biasing said armature in an opposite direction for decreasing the electrical resistance of said variable electrical resistance means, a hollow element carried by the electromagnet and having an inner surface, said spring member positioned within said hollow element and extending across said hollow element, one end of said spring fastened to said element and the opposite end bearing on the inner surface of said element and resting upon the electromagnet, and a portion of said opposite end (I said spring wrapping tangentially upon the inner surface of said hollow element so as to progressively increase the resistance of said spring to displacement of said armature by said electromagnet.

7. An electrical regulator, comprising, in combination, a variable electrical resistance means,

an electromagnet, an armature movably mounted in relation to said electromagnet, means connecting the armature to the variable electrical resistance means, said electromagnet biasing said armature in a direction for increasing the electrical resistance of said variable electrical resistance means, a spring member for biasing said armature in an opposite direction for decreasing the electrical resistance of said variable electrical resistance means, a hollow element carried by the electromagnet and having an inner surface. said spring member positioned within said hollow element and extending across said hollow element, one end of said spring fastened to said element and the opposite end bearing on the inner surface of said element and resting upon the electromagnet, and a portion of said opposite end of said spring wrapping tangentially upon the inner surface of said hollow element so as to progressively increase the resistance of said spring to displacement of said armature by said electromagnet, said spring member having a relatively low temperature coefli'cient of expansion, and said hollow element having a relatively great temperature coefficient of expansion so that the position of the inner surface of said hollow member varies with temperature for adjusting said spring member.

8. An electrical regulator, comprising, in combination, a variable electrical resistance means, an electromagnet, an armature movably mounted in relation to said electromagnet, means connecting the armature to the variable electrical resistance means, said electromagnet biasing said armature in a direction for increasing the electrical resistance of said variable electrical resistance means, a spring member for biasing said armature in an opposite direction for decreasing the electrical resistance of said variable electrical resistance means, a hollow element carried by the electromagnet and having an inner surface, said spring member positioned within said hollow element and extending across said hollow element, one end of said spring fastened to said element and the opposite end bearing on the inner surface of said element and resting upon the electromagnet, said spring member having a relatively low temperature coefficient of expansion, and said hollow element having a relatively great temperature coefficient of expansion so that the position of the inner surface of said hollow member varies with temperature for adjusting said spring member.

WILLIAM G. NEILD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number

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