US1260995A - Electric regulator. - Google Patents

Description

VENTOR A-bf A TTOHNEYS WITNESSES J. BIJUR.

v ELECTRIC REGULATOR.

APPLICATION FILED JULY 1. I910.

5 SHEETS-SHEET 2.

luvs/V1012 WITNESSES:

J. BlJUR. ELECTRIC REGULATOR,

APPLICATION FILED JULY 1,1910.

Patented Mar. 26, 1918.

5 SHEETS-SHEET 3- igl- IN VENTOI? WITNESSES: T 1 g; 3

J. BIJUR.

ELECTRIC REGULATOR.

APPLICATION FILED JULY 1. 910- 1260995. Patented Mar. 26, 1918;

5 SHEETS-SHEET 4.

.WITNESSES: INVENTOR J. BIJUR.

ELECTRIC REGULATOR.

APPLICATION FILED JULY 1. I910.

Patented Mar. 26, 1918.

5 SHEETS-SHEE 5- WITNESSES UNITED STATES PATENT OFFICE.

JOSEPH BIJUR, OF NEW YORK,

.N'. Y.', ASSIGNOR TO THE SAFETY CAR HEATING LIGHTING COMPANY, OF NEW YORK, N. Y., .A CORPORATION OF NEW JERSEY.

' nnncrnro nneunn'ron.

Specification of Letters Patent.

Patented Mar. 26, 1918.

7 '0 all whom it may concern:

Be it known that I, JOSEPH -BIJUR, a citizen of the United States, residing at New.

York, in the county of York and State of New. York, have invented certain new and useful Improvements in Electric Regulators', of Whl0l1 the following is a full,

clear, and exact description, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to electrical regulating apparatus. One of the objects thereof is to provide reliable, efficient and accurate electrical regulating apparatus. other object is to provide apparatus of the above typein which extreme variation in a resistance element is efliciently utilized. Another object is to provide in regulating apparatus, simple and practical means for substantially eliminating the effect of variations in temperature. Another object is to provide regulating apparatus of the character first mentioned of compact and selfcontained construction. Other objects will be in part obvious and in part pointed out hereinafter.

. The invention accordingly consists in the features of'construction,. combinations of elements and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the application of which will be indicated in the following claims.

same

In the accompanylng drawings, wherein 1s shown one of various possible embodi- Figure 1 is a diagrammatic plan of the Fig. 2 is a plan of a pilot regulator; I

Fig. 3 is a side elevation of the same;

Fig. 4 is a front elevation of a main regulator;

Fig. 5 is a plan view of the same;

7 Fig. 6 is an end elevation of the same;

Figs. 6 and 6 are views of details of the apparatus;

Figs. 7 and 8 are curves illustrating. certain features of the action of the apparatus. Similar reference characters refer to similar parts throughout the several views of the drawings.

Referrin now in detail to Fig. 1 of the drawings,t ere is shown a generator 1 hav inga shunt field 2 across the mains 3 and 4 of which is bridged a secondary battery 5. Suitable switches 6 and 7 are provided as in the main 3, and the former may-be of an automatic construction known in the art in a similar relation. Serially connected in the main 4 isa variable resistance medium 8, hereinafter described in detail, and bridged across the mains at'a "pointbeyond this resistance are lamps or other translating devices 9. Also brldged across the mains and at a point adjacent the lamps 9 is a voltagecoil 10 having connected in its circuit a resistance element 11, hereinafter referred to in detail.

As conducive-to" a clearer understanding of the details of this invention, it may be noted at this point that the field of the solenoid 10, whose field varies with the voltage across the mains adjacent the lamps, is utilized to control the current flowing through a local circuit 12, also bridged across the mains and having disposed therein the magnet 13. The latter magnet by suitable means appropriately varies the resistance of the medium '8 toaccord w'ith'any tendency to abnormalities of the voltage upon the lamps and by this variation of the potential drop in the main 4, the lampvoltage is held constant to a nice degree.

' Recurring to the solenoid 10, it is to be noted that the field of this element controls the position of a movable core '14, which, acting through the knife-edge l o', moves a lever 16.* This lever, one end of which enters the core 14 beneath the knife-edge -15,

comprises a pair of arms 17 and 18 clamped about a rocking spindle 19. The ends of the spindle are provided with a downwardly extending edge, as indicated at 20, and these edges rest upon bearings 21 mounted in casings 22 upon the frame 23.v This frame is secured to a panel 2 1 supporting the solenoid 10 through the frame 25. In frame 23 there is formed a suitable bracket 26, for the arm 17, provided with set-screws 27 to limit the range of movement of the arm. Arm 18 is jointed to a rod 28 at its free end, the latter member leading to a suitable dashpot 29. Also connected to the arm 18 is a spring 30, the tension of which is adjustable by the threaded pin 31 and knurled nut These several moving parts are so formed and related that their center of ravity, collectively considered, is substantially in the axis about which they swing, and, hence, they are not only unaffected by jarring or vibration, but tend to maintain, in so far as gravity is concerned, any position in which they may be placed.

Formed upon the arm 17 is a depending lug or arm 33, to which is pivoted a link 34 swung from the frame by the pairs of parallel links 35 and connected with a movable pressure-plate 36. Adjustably mounted op posite this plate in the frame 23 is a similar plate 37, the position of which is governed by a suitable threaded shank 38. Between these plates are mounted a set of thin upright carbon disks 39, contacting one with another, and suitable means are provided to make connection to these disks serially in the circuit 12. As these'disks are compressed by the downward swinging of the arm 17, due to an increase of field strength of the solenoid 10, their aggregate resistance is reduced and the current in the circuit 12 increased in substantial accordance therewith. The mechanical resistance to compression of these disks is of a low order owing to their small size, loose contact and upright disposition, and the force exerted by the core of the solenoid 10 is multiplied several times by the leverage due to the above arrangement and. proportioning of parts. For this reason, assuming the various forces to be balanced with a normal voltage across the lamps, any slight variation in this potential difference" will be highly effective in its variation of the resistance of the carbon-disks, and a small departure from normal voltage will generally cause a continuous compression or compression of the disks until they act through the regulating apparatus, later described, to restore normal voltage across the lamps and a normal field strength of the solenoid 10. The

action of this pilot is thus rendered extremely sensitive, and by a proper conformation and adjustment of the spring 30 it can be made to hold substantially any position with normal voltage across the mains.

The resistance element 11 is formed of an alloy of such composition that its electrical resistance is substantially constant throughout a large range of temperatures, and this resistance is t ken of such value that nearly the entire fal in potential in the branch circuit, comprising the solenoid 10, occurs at this point. In this manner, a large proportion of the (FR heating occurs in the element 11, rather than in the solenoid 10, which is of a relatively low resistance, and this heating effect does not vary the current by which it is caused. It will be noted, however, that with any given change in voltage across the lamps, there willbe an exactly corresponding proportional change in potential difference at the terminals of thesolenoid, and,

consequently, a like variation in its field strength. For example, assuming that the voltage across the lamps is thirty and with twenty-five volts drop in the resistance element 11 there is substantially five volts across the solenoid; if now there is a given change of voltage across the lamps, there is only one-sixth of this change across the solenoid, but as its potential difference at its terminals is only five volts, instead of thirty, the effect of this variation in voltage is the same as though the solenoid were directly connected, and, yet, the inaccuracy, due to variation in temperature, is eliminated as the heating in the solenoid is insignificant. To form the entire solenoid of the above alloy, having sufiicient ampere turns, would occasion a large loss in cheapness and compactness.

Considering now the main regulator, shown in Figs. 4, 5 and 6, it is to be noted that the magnet 13 is of the two-pole type, having separate windings upon each pole, and these poles 40 and 41 are provided with rounded, tapering ends. Coacting with this magnet, which is mounted adjacent a frame 42, is an armature 43 secured to a frame 44 pivotally connected at 45 to main frame 42. This armature is provided with a pair of openings 46 adapted to permit the entry of the rounded poles 40 and 41, and the curve of the poles, as well as the walls of the openingsQ-is so formed that with a given field strength of the magnet, the pull exerted upon the armature increases uniformly at a slight rate as the armature approaches the poles. This effect is gained by so'forming the parts that as the lines of force through the armature multiply upon its approach to the poles, they decrease in effectiveness to nearly the same extent owing to their lateral tension rather than direct pull in the direction of movement of the armature. The above is expressed in the terminology of commonly accepted theories of magnetic action and will, it is believed, make clear that any variation in pull of the magnet 13 upon its armature is due substantially to a corresponding variation in its field strength. Connected with a projection 47 upon the swinging armature 43, by means of links 48, is a forked crank 49 having secured thereon a stepped contact-bar 50 for a purpose hereinafter described. Pivotallymounted upon the supporting pin 51, between the portions of the crank 49, is a link 52 which curves about a shaft 53, the latter being mounted in bearings 54 upon the frame 42 and having a crank 49 pinned thereon. This link extends throughout the length of the apparatus and is connected with a short rod 55 by a pivot-pin 56. This pivot-pin has a loose bearing in the link 52 and. accordingly,

the functions of a universal joint. Rod 55 passes loosely through a pressure-plate 57 and has threaded thereon a heavy adjusting nut 58, which bears upon an insulated collar .59 formed on the pressure-plate.

' plates or taps 62 into four sections, the several sets being serially connected in main 4 in parallel one with another.

It may be noted at this point that as the armature 43 swings downwardly, it rotates the shaft 53 and exerts a thrust upon the link 52, which is transmitted through the rod 55 and nut 58, to relieve the pressure 'tion 66 to a dash-pot 67 of any ordinary or upon the plate 57, which is thus permitted to swing outwardly upon the loosely connected links 63 by which it is suspended. It may also be noted that by an adjustment of .the nut 58 the pressure upon the sets of disks is varied without varying the position of the armature 43,: v

Mounted on shaft 53 is a crank, 64 having an arm 65 which leads by a pivotal connecwell known construction. This crank is provided with an arm 68 extending toward the pressure-plate 57, which is sowmounted, proportioned and adjusted as to balance the weight of the various-parts, connectedwith the shaft 53, in their various positions and maintain the center of gravity of the several weights acting upon the shaft substantially.

in its axis.

Formed in crank 64 is a slot 69 concentric with respect to the shaft53 and adjustably mounted in this slot, as by means of the nut 70, is a link 71 leading to a spring 72, the tension of which is adjusted by the eye-bolt 73 passing through the frame 42. This arrangement of parts permits not only adjustment of the tension of the spring, which is carefully proportioned to perform its functions, but adjustment of its effective pulling arm with respect to the shaft 53, and consequently of the rate of variation of its turning movement as the shaft rotates from any given position.

The spring 72 tends to rotate the shaft 53 in opposition to the attractive force of the magnet 13, and acting through the crank 49 and link 52, which form in effect a toggle, tends to compress the several sets of carbondisks, the pressure upon all sets being equalized by the universal joint connection of the link with rod 55. These disks are accord- 1 ingly compressed or released in accordance with the preponderance of turning movement of the spring 72 or magnet 13 and travel freely and unaffected by gravity bein held in alinement by means of the several rods 74 extending from the frame 42 to the plate 60 and provided with insulating sleeves 75.

A suitable electrical connection is provided from main 4 to contact-bar 50, as shown in Fig. 1, and the several stepped contacts of this element coact with the springbrushes 76, 77, 78 and 79. These brushes 7 9, '7 8 and 77 are respectively connected with the successive plates 62 and brush 76 is in connection with the main 4.

As the contact bar 50 swings upwardly under the influence of the spring 72 and approaches a position of maximum pressure with the toggle substantially on its center, the spring-brush 79 is first met, providing a dead short-circuit about the first section of the several sets of disks, and thus reducing the residual resistance of the medium. Swinging farther the contact-brush 78 is engaged, 79 being bent back, cutting out another section, and in this manner the entire residual resistance of the medium at maximum compression is eliminated by a metallic short-circuit about the same. The rapidly increasing pressureexerted by these shortcircuiting brushes as they are successively met and bent back to permit the next contact to be made acts directly to oppose rotation of the shaft 53 and is utilized as hereinafter described.

Q In order to avoid the chance of ambiguity in the meaning of certain expressions used throughout this description and following claims, it may be noted at this point that the term plate or pressure-plate is used broadly as definitive of any element through which pressure may be exerted upon a variable resistance medium, and by the expression collective resistance tocompr'ession, or the like, with reference to contacting resistance elements, is meant their resistance to pressure due to their contacting one with another and gaining support one from another as distinguished from the relatively insignificant mechanical resistance which they exert when loosely disposed, due probably to their tilting against one another. It may also be noted that by the central position of the toggle, or a position on its center, is meant that position in which the axes of its two component members are substantially in alinement.

As preliminary to a discussion of the operation of this apparatus, it may be noted that the mechanical resistance to compression of a pressure-controlled variable resistance medium increases at an increasing rate as the compression progresses. To illustrate this, if a pressure of ten pounds is required to compress the mediumfor onetenth of an inch, twenty pounds will not suffice to compress it two-tenths of an inch.

The pressure required in this case may be thirty pounds, and to compress it a further tenth, it may require one hundred pounds or more. The above is merely illustrative of the fact that the curve of compression, with compressive force as ordinates and linear compression as abscissae is upwardly concaved. It may also be noted that the curve representing the force exerted by a toggle as it approaches its center, with a uniform turning moment, is likewise upwardly concaved, and these curves correspond closely, except as the toggle comes upon its center, when its force is theoretically infinity, and accordingly increases at this stage faster than the mechanical resistance of the carbons. Thus, with a uniform turning moment of the shaft 53, the pressure exerted upon the carbons increases at an increasing rate and their resistance to compression likewise increases at an increasing rate. The toggle is thus used to compensate for the accelerating resistance to compression of the resistance medium, and, hence, the resistance to turning of the shaft 53 exerted by the carbons through the toggle is substantially constant, although it increases to a slight degree throughout .most of the range and decreases more sharply at the end of maximum compression, due to the above noted effect of the toggle. Referring to Fig. 7 of the drawings, the curve AB is illustrative of the turmngmoment required for a uniform rate'of compression of the resistance medium; the abscissae being the compression of the medium and the ordinates the torque or the turning moment required to affect it. The drop of the curve at C is due to absence of collective resistance to compression of the carbons, and the drop at B due to the effect of the toggle. The latter drop is compensated for by the resistance to the turning of the shaft effected by the successive deformation of the short-circuiting brushes, above noted, and, hence, the resultant of the various forces, aside from the magnet, acting to rotate to relieve pressure upon the carbons, is indicated by the curve AD.

Considering the forces tending to turn the shaft in the opposite direction, the weight of all parts may be disregarded, for the are balanced, as above noted, and the das -pot is, of course, merely a retarding, rather than an active, force.- The spring 72 as the compression progresses loses a portion of its tractive force, due to the release of tension, but this is partially compensated for by the increase of the effective arm through which it acts on the shaft 53. These errors would exactly ofi'set one another, theoretically considered, only with the crank at forty-five degrees to the line of pull on the spring, but, in practice, the parts are so arranged that the turning moment of the spring is substantially constant or slightly falling. Hence,

in Fig, 7, the dotted curve EF represents the effective turning moment of the spring. The difference between these resultant torques, indicated by the vertical cross-hatching, is the turning moment which must be exerted by the magnet to Vary the pressure from total compression to total release and the curve GH Fig. 8, represents this torque. The slight decrease in the effective arm through the crank'49 is substantially compensated for by the slight increase in the pull due to hence, with a magnetic field strength, and consequently with a strength of current in the magnet, which increases continually as indicated by the curve G-H Fig. 8, there will be a substantially uniform compression of the variable resistance medium. Hence, for any current value in the magnet 13, there is a fixed and definite position which the regulating apparatus will assume and a fixed and definite resistance which is inserted serially in the main 4. In this manner the chance of hunting of the apparatus is done away with and its action is rendered thoroughly reliable, accurate and effective. It is to be pointed out in this connection that by reason of the grouping of the sets of re sistance members about the actuating link 52, which, in so far as certain broad features of this invention are concerned, may be replaced by any actuating element, there is attained a compactness of structure and di-' rectness of pull which contribute materially to the advantages and elficient action of the apparatus.

It may also be noted that by reason of the arrangement and proportioning of the parts, the pressure upon the sets. of carbon disks may be reduced to any desired point, and, hence, the range of variation in resistance increased. As above noted, there is a certain range of resistance in media, comprising a plurality of substantially upright contacting members, which extends beyond the point at which they collectively resist compression. This range is extremely valuable and, yet, in ordinary regulating apparatus is unused, as the actuatlng means are not adapted to hold the compressing members in a position beyond that at which the disksv are in full contact with and pressing against one another. It may also be noted that by the use of apparatus such as that herein described, an extreme degree of compression upon the resistance medium is obtainable and the parts are, in fact, compressed to such an extent that the contact resistance may be substantially eliminated or reduced below the value of the internal resistance of the disks.

Briefly stated, theoperation of the entire apparatus is as follows :-Up'on the voltage across the mains varying from the desired normal yalue a corresponding change will occur in the field strength of the solenoid 10, thus inducing a proportionate alteration in the electrical resistance value of the group of carbon disks 39. This action Wlll occasion a proportionate change in the current flowing through conductor 12 and in the field strength of the magnet 13, the field strength of the latter being increased with a tendency to abnormally high voltage or weakened when the voltage tends to fall below normal. The variation in field strength of magnet 13 will occasion a movement of the armature 48, which, acting through the means above described, will in-' crease or decrease the resistance of the main regulator and change the potential drop therein to precisely such extent as is necessary to bring the voltage impressed upon the lamps to normal value. The action of these parts is so sensitive and rapid that there will be no substantial change in the voltage of the lamps as the slightest tendency to-change will immediately remedy itself.

It will thus be seen that there is provided apparatus in which the several ob ects of this invention are achieved, and which is sensitive, accurate and reliable in action, of simple, compact and durable construction and well adapted to meet the conditions of the hardest practical use.

As many changes could be made in the above construction and many apparently widely difierent embodiments of this invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secure by Letters Patent is:

1. In regulating apparatus, in combina tion, a varlable resistance medium comprising a plurality of sets of contacting members, and current-controlled means adapte to vary the compression of said medium at a uniform rate with a substantially uniform rate of variation of current throughout the range of collective resistance to compression offered by said members, and to reduce the compression of said medium beyond said range.

2. In regulating apparatus, in combination, pressure controlled variable resistance media, each comprising a plurality of contacting members, a pressure device extending over the ends of said media, and actuating means about which said media are grouped operatively related to said pressure device to compress said media, said actuating means being current controlled and adapted to vary the compression of said media at a uniform rate with a substantially uniform rate of variation of current throughout the range of collective resistance to compression offered by said members, and to reduce the compression of said media beyond said range. f

3. In regulating apparatus, in combination, a plurality of sets of contacting members, each set being arranged with its members in substantially upright position, pressure means extending over said several sets, connections whereby the pressure upon said sets is equalized, means adapted to reduce the pressure upon said members beyond the point at which they collectively ofierresistance to said compression, said means comprising a toggle adapted to increase-the pressure as it approaches central position and circuit-closing means upon the apparatus formed to oppose movement of said toggle. 5

4. In regulating apparatus, in combination, a plurality of pressure-controlled variable resistance media, a relatively fixed member against which said media abut at one end, a movable pressure member extending over said several media, a member having a universal joint connection with said pressure member and adapted simultaneously to exert equal pressure upon said media and electrically controlled means adapted to actuate said last member.

5. In regulating apparatus, in combination, variable resistance media, each comprising a plurality of contacting members, a pressure plate extending over the ends of 100 said media, andprovided with connections to equalize pressure thereon, and currentcontrolled means comprising a toggle having a continuous link extending between said media for controlling said plate to vary 105 the compression of said media at a uniform rate with a substantially uniform rate of variation of current throughout the range of collective resistance to compression ofl'ered by said members. 1 0

6. In regulating apparatus, in combination, a plurality of sets of contacting members, each set being arranged with its members in substantially upright position, a pressure plate extending over said sets, a 115 member extending between said sets for operating said pressure plate, a connection between said plate and said member permitting movement of said plate to equalize pressure upon said sets, electrically con- 120 trolled actuating means operatively related to said member to compress said sets and also to reduce the pressure upon said sets beyond the point at which they collectively ofier resistance to compression.

7. In regulating apparatus, in combination, a plurality of sets of contacting members, each set being arranged with its members in substantially upright position, pressure means extending over said several sets, 130

connections whereby the pressure upon said sets is equalized, and current-controlled means extending between said sets and operatively related to said pressure means to vary the compression of said members at a uniform rate with a substantially uniform rate of variation of current throughout the range of collective resistance to compression offered by said members, and to reduce the compression of said'members beyond said range.

8. In regulating apparatus, in combination, a plurality of sets of contacting members, each set being arranged with its members in substantially upright position, a pressure plate extending over the ends of said sets, and current-controlled means having a universal joint connection with said pressure plate and extending between said sets and adapted to move said plate to com-' press said sets. 7 j

9. In regulating apparatus, in combination, a plurality of sets of contacting members, each set being arranged with its members in substantially upright position, and current-controlled means extending between said sets for varying the compression of said members at a uniform rate with a substantially uniform rate of variation of current throughout the range of collective resistance to compression oflered by said members, and for reducing the compression of said members beyond said range.

10. In regulating apparatus, in combination, a plurality of pressure-controlled variable resistance media, a pressure plate extending over the ends of said media, and current-controlled means extending between said media and having a universal joint connection with said pressure plate and adapted to move said plate to compress said media.

11. In regulating apparatus, in combination, a plurality of sets of contacting members, a pressure plate extending over the ends of said sets, and current-controlled means having a universal joint connection with said pressure plate for controlling said plate to vary the pressure of said sets at a uniform rate with a substantially uniform rate of variation of current throughout the range of collective resistance to compression offered by said members.

12. In regulating apparatus, in combination, a plurality of sets of contacting members, each set being arranged with its members in substantially upright position, a pressure plate extending over the ends of said sets, and current-controlled means comprising a toggle having a continuous link extending between said sets and co-acting with said pressure plate to vary the compression of said sets at a uniform rate with a substantiallyu-niform rateof variation of current throughout the range of collective resistance to compression offered by said members, and to reduce the pressure on said sets beyond the said range.

13. In regulating apparatus, in combination, a pressure-controlled variable resist ance medium comprising a plurality of contacting members formed and constituted toresist mechanical pressure at an increasmg rate as the compression progresses, means adapted to vary the pressure thereon at a different rate as the compression progresses, and electro-magnetic means operativcly related to said with a constant rate of increase of current therein to compensate for the difference in said rates and vary the compression of said medium at a constant rate throughout the range of collective resistance to compression offered by said members, and to reduce compression of said members beyond said range.

14. In regulating apparatus, in combination, a pressure-controlled variable resistance medium comprising a plurality of contacting members resisting mechanical pressure at an increasing rate as compression thereof progresses, and electrically controlled means' adapted to vary the pressure upon said medium at a different rate as compressionprogresses, said medium and said means being so formed relatively to each other that the pressure exerted by said means upon said medium is substantially equal to the resistance to compression offered by said medium throughout the range of collective resistance to compression offered by the component members of said medium, said means also being adapted to reduce the compression of said medium beyond said range.

15. In regulating apparatus, in combination, a plurality of pressure-controlled variable resistance media, a pressure plate extending over the ends of said media, and current-controlled means extending between said media and having a universal joint connection with said pressure plate and adapted to move said plate to compress said media.

16. In regulating apparatus, in combination, a plurality of sets of contacting members, -a pressure plate extending over the ends of said sets, and current-controlled means having a universal joint connection with said pressure plate for controlling said plate to vary the pressure of said sets at a uniform rate With a substantially uniform rate of variation of current throughout the range of collective resistance to compression offered by said members.

17. Regulating apparatus comprising, in combination, a presure-controlled variable resistance medium, means for causing variations of pressure upon said medium substantially corresponding to the variations of mechanical resistance to compression offered by saidmedium, an armature associated with medium and adapted v said means, and a voltage-responsive electromagnet 'co-acting with said armature.

18. Regulating apparatus comprising, in combination, a pressure-controlled variable resistance medium resisting mechanical pressure at an increasing rate as compression progresses, means for exerting pressure upon said medium at an increasing rate as compression progresses, and electro-magnetic means controlling said last named means to cause changes of resistance in said medium substantially proportional to changes of current in said electromagnetic means.

19. Regulating apparatus comprising, in combination, a pressure-controlled variable resistance medium, means adapted to cause variations of pressure upon said medium corresponding to the variations of mechanical resistance to compression ofiered by said medium, an armature associated with said means, and an electromagnet co-acting with said armature to hold said medium at a given stage of compression with a given current passing through said magnet.

20. Regulating apparatus comprising, in combination, a resistance device exerting an increasing mechanical opposition to force tending to decreaseits value, means for exerting pressure upon said medium to compensate for the effect of said mechanical opposition, and electromagnet means for controlling said compensating means.

21. In regulating apparatus, in combination, a pressure-controlled variable resistance medium comprising a plurality of contacting members, adjustable means adapted to adjust the range of compression of said medium, a shunt circuit about said members, and electrically operated means comprising a toggle adapted to increase pressure upon said members as the toggle approaches-its central position and close said shunt as the compression approaches completion.

22. In regulating apparatus, in combination, a pressure-controlled variable resistance medium, means adapted to lead current therethrough, current taps disposed in said medium at intervals in the direction of flow of current, electrical connections to said taps, and electromagnetic means controlling the pressure upon said medium and the connections to said taps.

23. In regulating apparatus, in combination, a pressure-controlled variable resistance medium, and electromagnetic means controlling the pressure upon said medium, said means comprising means adapted to successively eliminate sections of said medium.

24. In regulating apparatus, in combination, a pressure-controlled variable resistance medium, and electromagnetic means controlling the pressure upon said medium, said means adapted to successively shunt sections 0t said medium.

25. In regulating apparatus, in combination, a pressure-controlled variablemesistance medium, a pair of members of relatively low resistance disposed in said medium intermediate its ends, means adapted to bring said members into low resistance connectionat an advanced stage of compression of said medium and short-circuit the intervening resistance members, and electromagnetic means controlling the pressure upon said medium.

26. In regulating apparatus, in combination, a pressure-controlled resistance medium, a series of members of relatively low resistance disposed at intervals in said medium, means adapted to bring said members into low resistance connection at an advanced stage of compression of said medium, and electromagnetic means controlling the pressure upon said medium 27. In regulating apparatus, in combination, a pressure-controlled resistance medium, a series of members of relatively low resistance disposed Within said medium, means adapted successively to bring said members into low resistance connection at an advanced stage of compression of said medium, and electromagnetic means controlling the pressure upon said medium.

28. In regulating apparatus, in combination, a pressure-controlled resistance medium, a pair of members of relatively low resistance disposed within said medium, and electromagnetically controlled means comprising a toggle adapted to compress said medium and bring said members into low resistance connection as the toggle approaches its central position.

29. In regulating apparatus, in combination, a pressure-controlled resistance medium, a plurality of normally opened shunt circuits respectively disposed about successive portions of said medium, means adapted to shunt successively a greater portion of said medium, a toggle adapted to compress said medium, a member moved by said toggle to successively close said shunt circuits, and electromagnetic means co trolling the position of said toggle.

80. In regulating apparatus, in combination, a pressure-controlled resistance medium, a plurality of normally opened shunt circuits respectively disposed about successive portions of said medium, a toggle adapted to compress said medium, a member moved by said toggle to successively close said shunt circuits, the contacts of said shunt circuits being arranged to offer successively greater resistance to the movement of said toggle as the compression progresses, and electromagnetic means controlling the position of said toggle.

31. In regulating apparatus, in combination, a pressure-controlled variable resistance medium, a plurality of normally opened shunt circuits respectively disposed about successive portions of said resistance, means adapted successively to close said shunts as the compression progresses and electromagnetic means controlling the pressure upon said medium.

32. In regulating apparatus, in combination, a pressure-controlled variable resistance medium, a shunt circuit about, said medium, and electromagnetically controlled means adapted to compress said medium and close said shunt as the compression approaches completion, said means comprising a toggle which increases compression as it approaches its central position.

33. Regulating apparatus for car-lighting systems comprising, in combination, a variable resistance exerting a variable physical opposition to force tending to vary its resistance value, means for exerting variable force upon said resistance substantially proportional to the variable physical opposition thereof, and electromagnetic means for controlling said first-mentioned means.

In testimony whereof I afiix my signature, 5

in the presence of tWo Witnesses.

JOSEPH BIJUR. Witnesses:

ROBERT S. BLAIR, LEONARD A. WATSON.

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