US2828395A - Electromagnetic carbon-pile regulators - Google Patents

Description

March 25, 1958 L. R. NIXON ETAL ELECTROMAGNETIC CARBON-FILE REGULATORS 3 Sheets-Sheet 1 Filed Dec. 22, 1953 3 Sheets-Sheet 2 L. R. NIXON ETAL ELECTROMAGNETIC CARBON-FILE REGULATORS March 25, 1958 Filed Dec. 22. 1953 MA. MW);

March 25, 1958 L. R. NIXON ETAL 2,828,395

ELECTROMAGNETIC CARBON-FILE REGULATORS Filed Dec. 22, 1953 3 Sheets-Sheet 5 v 20 21 20 l i i Z i 375' i 9 i i i I l '77 77 United States Patent O ELE TR M NET AR O -P LE' REGULATORS Leslie Reginald Nixon and Andrew'Stamber-ger, London, England, assignors to J. Stone & Company (Deptford) 'Limited,'l;ondon, England, :a British company ApplicationDecemherZZ, 1953, Serial No. 399,794

Claims-prioritnapplication Great Britain December 31, 1952 5 ,Claims. (Cl. 201-51) This invention concerns improvements relating to telectromagnetic carbon-pile regulators which are sealed {in an inert atmosphere. Sealingpf such regulators can he made to achieve substantial advantages, but thereare several problems to be overcome .in applying the prineiple to everyday practical use.

E 1 Parti ula pr em a ses f o the necessity f minimising heating of the magnet system by l 1e,carbon pile. {lransmissien of heat bythe inert gas can be limited by restricting communication between enclosures-containing the magnet system and pile respectively. This, however, does not-exclude the possibility of .substantial heat transmission'by conduction. According=to the present 'inventiom-for limiting the transmission ofheatiby the latter means, gthe path for .heat conduction between the enclosures forthe pile and :the magnetsystem is made-highly resistant to heat conduction. For this purpose, parts of one or both of the enclosures adjoining the connection between t-hemis or are made ofincreased length and/or of-substantially reduced cross-sectional area and/or 1 material of :low thermal conductivity.

rIt is also important that-no local .high temperature riseshould bepos'sible anywherevon the-surface of the regulator. face .of --the pile enclosure, where -:it 'is most 'li'able' to In order to prevent :suchlarise at thesuroccur, the latter is closely surrounded by a finned jacket.

In order to obtain a compact but effective arrangement of the magnet system and associated elements the magnet is advantageously disposed on the prolongation 'of the pile axis but transversely across'the same the armature being carried upon a clapper which acts upon the pile through a strut and is pivotally mounted substantially on the said axis between the pile 'and the' magnet so that the armature hasan oblique approach to the magnet poles. v

A preferred embodiment of the invention will now be more fully described by way of example and-with reference to' the accompanying drawings, in which:

Figure 1 is aside elevation of a carbon-pile regulator withthe enclosing can removed and with the pile shown in axial section;

Figure 2 is an axial section, on the line IIII inFigure -4, through the pile-compressing mechanism;

Figure 3 a plan view to a smaller scale andintended only to indicate the relative positions of the main-components;

. Figure 4a cross section on the line IVIV in Figure 1; and

Figure 5 a perspective view of a bimetal device.

The embodiment illustrated has beendevised more particularly for use as a voltage regulator on aircraft and for other cases where reliable high performance is required in conjunction with compactness. The features to be described may, however, be employed withadvantage in regulators for. other purposes.

. Inthe regulator illustrated, the magnet system and the pile-compressing mechanism are enclosed in acylindrical 2,828,395 Pa e ted 5. .58

2 c n 1' ow by a chain ine in Figure h in the end 2 or both .ends 2, 3domed andmafde, for example, of magnetic martensitic stainless steel. The pile 4, composed of small diameter discs 5, guided in a ceramic sheath 6, is enclosed in a metal tube 7 shrunk upon the sheath and located co-axially with the can 1. To minimize'jheatconducjtion between the pile 4 and magnet systeminthecan 1, them'et'al tube 7 is extended towards the can by a .part of considerably reduced cross section (for example reduced to aboutone eighth or even less) and" made" for example of relatively poorly conducting austenitic stainless steel. As' illustr ated, this .part is a co-axial tube i 8 soldered into the tube 7 and into an intu-r'ned, central, funnel-.shaped'portion 9 (Figure 2) of the adjacent cover 2 of the can; The .cover2 is separate from the body of the can .1 and is soldered into it by means of ,a flange 10. A domed shape of the covers 2 3 .n'otonly stiifens them againstdeflection due to any pressure difference between' the inside and outside of the can 1, but, as regards the cover 2, also further lengthen'sthe path .fprrhefatconduction between the pile 4 and t ei i' q h cen The outer. end of the tube 171s tightly closed by a terminal .seal ;1 5 .for ming .a ,tixed abutment for the pile ,4, the seal-being coveredbyaprotective cap 11'. Thecan .1 and tubes 7.8 thus form acomplctely sealed enclosure the wholepf which is tilled with an inert'atmosphere. This is preferably L a gas or a. gas; tnixture-with a .good .viscosity and thermal -;conductivity. A suitable 'gas is helium.

To avoid danger i of local overheating with consequent k fifi e e e ial nai c tth max m mt pcra ture rise anywhere on the outside of the regulator should be as low as possible. A robust jacket with lins'12and ;a core,14 sufiiciently thickto obtain as low a temperature rise as possible, is .thereforeemployed. 'Preferably, it ;is pressure die-cast around the ,tube 7 enclosing the pile 4,-thus ensuring uniformhigh thermal conductivity between-the-tube and jacketand also rendering machining of mating-surfacesunnecessary.

The fixed abutment 15 at thesealed outer endof the tube 7, thatis the fixed end of the pile 4,.is connected to .the fixed magnet structure andis-located in relation'to the whole'magnetsystem by way of the outer-end fin 16 of the-jacket and a number of spaced tie rods 17 extending with clearance through holes :18 in the othehfins 12 andpassing by way of scaled connections .19 with the cover :Zintothe interior of the can 1 where they are connected-to-lugs 20 on an end part 21 of the fixed structure supporting the magnet system hereinafter described. The tie rods 17 form a rigid connection between the several parts and avoid the possibility oflost motion in the pile-compressing mechanism when the pile 4 is compressed. The rods 17 may be'made of a metal with a co-efficient of expansion suitable for ensuring temperature compensation for relative thermal expansion of the carbon ,pile 4. In this case, the domed shape of the cover 2- also assists in minimizingstresses caused-by differencein'thermal expansion between the.rods 17;and the tubesi7,;8. The end fin 16 is made of dished shape, with'the concavity outwards, in'ordertodncrease its rigidity and also to afford protection to-the seal at the outer end-of the tube 7.

Necessary readjustment for eventual change in the length of the pile 4 may be permitted without unsealing the regulator by providing for external adjustment of the relative positions of the magnet systernand abutment 15, that is the fixed end of the pile. This may be done by providing adjustablescrew connections between the tie rods 17 and the, end fin 16. Preferablyvand; as

assesses one or each of the tie rods is composed of two stud portions 17 17 screwed with threads of different pitch into a sleeve nut portion 17 Turning of the nut portion 17 will thus adjust the effective length of the tie rod. The adjusted position can be locked by means of lock nuts 17 In this case, not only the inner end of the stud is fixed, namely in the lug 20, but also the outer end in the fin 16, as by a key 23.

The pile is arranged to be compressed through a strut 24 with pointed ends 25 (Figure l) and 26 (Figure 2) acting between cups 27, 28 made of insulating material, such as glass or synthetic sapphire. The cup 27 adjacent to the pile 4 is enclosed in a conducting ferrule 29 carrying the movable co-llector, which comprises a carbon plug 30 at the adjacent end of the pile. The other cup 28 is mounted by means of a holder 31 in a flanged plate 32 which is connected by a pivot 33 to the upper end 34 of a clapper structure constituting the movable element of the magnet system. The plate 32 and the cup 28 carried by it are urged towards the strut 24 by a helical compression spring 35 abutting against a part 35' of the clapper structure and located approximately upon the prolonged axis of the pile 4.

The ferrule 29 is extended, out of contact with the strut 24, into the interior of the can 1 where it has a flange 36 (Figure .2) engaged by a coaxial helical compression spring 37 of relatively large diameter made from strip wound on edge and abutted through a hat-shaped insulating washer 38 against the inside of the funnel-shaped portion 9 of the cover 2. The spring 37 serves to steady the ferrule 29 and also to cause the said ferrule and the pile collector 30 to follow the strut 24 under conditions in which the pile reaction is low. It may conveniently also be used to make electrical connection between a stationary conductor 39 and the ferrule 29, for which purpose it is preferably made of a good electrical conductor, such as copper.

The part 35 of the clapper structure is fixed by a screw 40 to the main L-shaped part 41 of this structure carrying the armature 42. The clapper structure is mounted upon a part 44 (Figure 1), formed on or fixed to the part 21 of the fixed structure, by means of pairs of crossed leaf springs 45, 46. The axis 47 of rocking of the clapper so determined is located very close to the prolonged axis of the pile 4-, but the arrangement is such (Figure 2), that the strut 24 and the virtual lever arm by which the clapper acts on the said strut closely approaches a dead-centre condition when the pile is compressed, so as to compensate for the increasing pile reaction. In order to minimise sideways thrust on the movable collector 30, the slight rocking movement of the strut 24 which occurs upon movement of the clapper structure is arranged to be initially towards alignment with the pile 4 and then away from alignment (Figure 2 shows the mechanism in the position of rest, that is, with the armature unattracted and the pile fully compressed).

The main spring of theregulator comprises a helical tension spring 4?, or a plurality of such springs, disposed substantially parallel to the prolonged axis of the pile 4,

' but near the cylindrical wall of the can 1. The fixeo anchorage G for the spring can be set and adjusted by means of a nut 51 0n a screw 52 mounted in a cross piece 53 secured to the fixed structure. The movable anchorage 54 of the spring, which acts upon the clapper structure through a bimetal device hereinafter described, may be arranged, as shown, so that the virtual lever arm with which it acts about the axis 47 decreases with extension of the spring 49. This arrangement reduces the necessity for using a spring with a low rate, which would be difiicult to accommodate, and also permits of the use of a longer spring.

The magnet itself is a horseshoe magnet 55 disposed transversely of the can with, for the sake of explanation, the poles 55' projecting downwardly. The magnet, carrying its winding 56 on its two limbs, is clamped to two shapes in both cases.

upper and two lower claw-like parts, 57 and 58 respectively, which extend lengthwise of the can 1 from the end part 21 of the fixed structure. The magnet is so clamped by studs 57', 58 passing through an end frame 59 hereinafter referred to. The armature 42 has, due to the above-described relative disposition of the parts, an oblique approach to the poles The armature and/or the poles may be appropriately profiled in per se known manner in order to obtain a required magnet characteristic.

For the connection to the bimetal device and for the mounting of the pivot 33, the clapper structure extends beyond the axis 47, that is upwardly, to a point near the main spring 4%. The bimetal device is intended, by varying the effective action of the spring, to efiect compensation for change of resistance of the magnet winding due to temperature variation. One suitable construction of such device comprises two pairs of bimetal hairpin strips, 60 and 61 respectively (Figure 5). The first pair of strips 60 is connected at its ends 60 by screws 60 to the upper end 34 of the clapper part 41 and at the other ends 60 by screws 60 to the adjacent ends 61 of the strips 61. The otherends 61 of the latter are connected to a cross piece 54 constituting the movable anchorage for the spring 49. The higher-expansion sides of the bimetal strips 60,61 are the outer sides of the hairpin With increase in the temperature, determined mainly by the temperature of the winding 56, the bimetal strips 60 will deflect so as to reduce the tension in the spring 49, while the strips 61 will deflect to reduce the length of the virtual lever arm with which the spring acts and thus to reduce the effective rate of the spring. In this arrangement, in any position of the armature 42, the strips 60 effect compensation for the reduction in the magnet torque, resultant upon the decrease in current due to the increased resistance of the winding 56 at the increased temperature, while the strips 61 effect compensation for the reduction in the rate of change of magnet torque with armature travel which also results from the reduction in current. The compensation thus to be provided will naturally depend upon the characteristics of the magnet system. By this means, for example, regulation for constant voltage can be obtained which is substantially unaffected by temperature variation in the magnet winding 56.

The bimetal device described, or a simpler form of such device, for compensating for the etfect of heating due to the current in the winding 55 and/or to such due to ambient-temperaturevariation, may be arranged to be influenced by an auxiliary heater whose temperature rise is caused in known manner to be proportional to that of the winding. This heater may be housed, for example, in a bore in the clapper -41. A suita le position for this bore is indicated at 41 in Figure 2. By this means, the heating of the device can be well matched to the heating of the Winding. Alternatively or addition, a resistance with a negativetemperature co-eflicient may be employed connected in series with the winding 56. Close contact between this resistance and the winding may be obtained by winding the former into the latter or arranging it closely thereto on the inside or outside. This resistance may be shunted by a fixed resistance in order'to modify the compensation effect in required fashion.

In the illustrated inoperative condition of the regulator,

'- the clapper 41 is held against a stop 65 (Figure 2) by the spring 49, the pile 4 being maintainedunder compression by the auxiliary spring 35 bearing on the plate 32. As shown in Figure 2, the stop 65 is adjustably mounted on the end of the lower tie rod 17. For coupling the plate 32 to theclapper whenthe armature 42 is attracted, the clapper part 35 is provided with a pin es engageable with the remote side of the end of the plate 32. In the aforesaid inoperative condition, there is a slight lostmotion gap between the pin 65 (Figure 2) and plate 3?. and as long as this gap exists, the minimum resistance of esca ees the compressed pile 4 will be practically unaffected by pile shrinkage. When the armature 42 is attracted, the lost motion is first taken up and then the plate 32 and the parts 31, 28 connected to it are carried along by the clapper 41 and the pile is decompressed. If desired, the lost-motion gap may be controlled by a bimetal device which compensates for any change in the distance between the fixed end of the pile and the magnet system due to thermal-expansion effects.

A pneumatic dashpot 67 of the annular-diaphragm type is arranged in a relatively cool position at the end of the can 1 remote from the pile, where its plunger portion 68 is fixed on the outside of the end frame 59. In order to obtain as compact an arrangement as possible, the dashpot 67 and the frame 59 are inclined in relation to the axis of the can (Figure 1), the axis of the dashpot extending towards the end of the clapper 41 remote from the armature 42. Bars 70 on the pot portion 71 of the dashpot are adjustably connected to rods 72 which straddle the magnet and are themselves connected to the ends of a stiff cross bar 73 flexibly connected to the clapper 41 by three crossed springs 74, 75 (Figure 2), the spring 74 being connected to the middle of the bar with one spring 75 on each side.

Counter-balance weights 76 are supported from the clapper 41 by arms 77 secured to parts 79 extending laterally from the said clapper. These weights serve to balance the clapper structure and armature in relation to the axis 47.

The magnet core may be composed of grain-oriented wound strip, for example as described in the specification of our patent application Serial No. 367,620, filed July 13, 1953.

The whole regulator may be suspended upon a base (not shown) by means of an anti-vibration mounting, one flexible support, say in the form of a spring system, being provided at each end of the regulator approximately concentrically with the axis of the can 1.

Such construction and arrangement permits of good advantage being taken in practical operation of the following benefits of scaling in an inert atmosphere: Firstly the pile 4 can be run at a relatively high temperature, so that carbon elements 5 of small cross-sectional area can be used, which reduces the work required to be exerted upon the pile for a given range of resistance variation. For, although the minimum resistance for a given compressive force is substantially independent of the area, the maximum resistance obtainable increases as the area is reduced, because the effects of friction and sensitivity to vibration are reduced. Secondly, with a sealed regulator, the damping afforded by the dashpot 67 is unaffected by atmospheric-pressure variation and, therefore, by altitude. Also the inert gas used may be one of suitable viscosity for the dashpot. Further, by using a gas of high thermal conductivity, the temperature gradients between the pile 4 and the tube 7 and between the winding 56 and the bimetal strip device 60, 61 can be reduced. Finally, with enclosure in an inert gas, both the electrical insulation and the flexible material of the dashpot will tolerate a higher working temperature. In addition, the sealed enclosure affords proofing against climatic conditions without further special provision.

We claim:

1. An electromagnetic regulator comprising a carbon pile, a magnet system, a pile-compressing member acting between the Said system and the said pile, a wall forming an enclosure closely surrounding the pile, a casing form ing an enclosure for said magnet system, means supporting said pile enclosure in a position spaced away from the said casing, and a tubular wall extension of substantially less cross sectional area relative to said pile enclosure which forms a connecting enclosure part between the said enclosures and through which the said pile-compressing member extends and acts.

2. A regulator according to claim 1, wherein the casing is can-shaped and has a cover into a part of which the tubular extension is sealed, the said cover part being extended inwardly of the casing to increase the length of the heat-conduction path between the enclosures.

3. An electromagnetic regulator comprising a carbon pile, a magnet system acting upon said pile, a tubular enclosure for the pile, a can-like enclosure having a cover for the magnet system, supporting means holding said tubular enclosure spaced away from said can-like enclosure, said tubular enclosure having an extension extending beyond said pile, said extension being of substantially less cross-sectional area than the said tubular enclosure, said cover having a part extending inwardly of said can-like enclosure, said tubular extension being sealed into said inwardly extending part of said cover whereby the length of the heat-conduction path between the enclosures is increased.

4. An electromagnetic regulator comprising a carbon pile, a magnet system, a supporting structure for the said magnet system, a pile-compressing member acting between the said system and the said pile, a wall forming an enclosure closely surrounding said pile, a casing forming an enclosure for the said magnet system, tie rods connecting the said pile enclosure to the said supporting struc ture, in spaced apart relation, said rods being sealed into the said casing, and a tubular wall extension which forms a connecting enclosure part between the said enclosures and through which the said pile-compressing member acts, said pile and magnet system being sealed in an inert atmosphere in the said enclosures.

5. An electromagnetic regulator comprising a carbon pile, a magnet system, a supporting structure for the said magnet system, a pile-compressing member acting between the said system and the said pile, a wall forming an enclosure closely surrounding said pile, finned jacket surrounding the said wall, a casing forming an enclosure for said magnet system, tie rods connecting the said jacket to the said supporting structure in spaced apart relation, said tie rods being fixed to the end of the jacket remote from the magnet system and sealed into the adjacent part of the said casing, and a tubular wall extension which forms a connecting enclosure part extending between the said enclosures and through which the said pile-compressing member extends and acts, said enclosures of said pile and magnet containing an inert atmosphere.

References Cited in the file of this patent UNITED STATES PATENTS 2,374,417 Chilton et al. Apr. 24, 1945 2,396,596 Moore Mar. 12, 1946 2,427,805 Neild Sept. 23, 1947 2,489,071 Austin Nov. 22, 1949

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