US2128361A - Electric illumination control system - Google Patents

Description

Au 30, 1938. R. B. llUNTER I 2,128,361 ELECTRIC ILLUMINATION CONTROL SYSTEM Filed Dec. 24,1954 2 Sheets- Sheet 1 Aug. 30, 1938 R. B. HUNTER O ELECTRIC ILLUMINATION CONTROL SYSTEM Filed Dec. 24-, 1934 2 Sheets-Sheet 2 TIME Patented Aug. 30, 1938 Richard B. Hunter, Shorewood, Wis., assignor to Cutler-Hammer, Inc. poration of Delawar- Milwaukee. -Wis., a cor- Application December 24, 1934, sci-mine. 758,960 4 14 Claims.

This invention relates to electric illumination control systems and more particularly to systems and apparatus for controlling the degree or degrees of energization of electric illumination cir-' 5 cuits.

While not limited thereto the invention is 'particularly applicable to the control of illuminating lights wherein it is desired to eifect' regularly recurring illumination intensity variations of a predetermined character. A

An object of my invention is to provide control systems of the aforementioned character having means for individually preselecting the minimum intensities and the maximum intensities of iilumination of the respective groups of lamps.

Another object is to provide such apparatus having means-for individuallypreselecting the rates of increase and the rates of decrease in intensities of illumination of' the respective groups of lamps.

Another object is to provide such apparatus having means for automatically varying the intensities of illumination of a plurality of groupsof lamps between selected minimum and maximum values in accordance with selected rates of increase and decrease of such intensities, respectively.

Another object is to provide a plurality of units of apparatus'of the aforementioned character having meanswhereby the phase relation of the cyclic illumination intensity changes in the respective groups of lamps may be preselected. Another object is to provide means common to the respective control units of a plurality of lamp circuits for automatically rendering the aforementioned illumination varying means effective at regularly recurring intervals.

Various other objects and advantages of the invention will hereinafter appear.

In carrying .out my invention I prefer to em- 55 in Figs. 1 and 2.

circuits employing differently colored groups of The contact arms"! and 8 are manually adjust- "control parts shown in Figs. land 2.

Fig. 4 is a diagram showing the operation of the light circuits of Figs. 1 and 2 under given conditions of adjustment of the control systems, and

Fig. 5 is a fragmentary diagrammatic illustration of a modifled'arrangement of certain of the 5 Referring first to Fig. 1 of the drawings, I have illustrated, by way of example, two groups of electric lamps, designated respectively by the reference characters] and 2, continuity of cir- 10 cuitand intensity of illumination ofv the lamps in the respective group's beihg subject to control by a system constructed in accordance with my invention; it'being" understood that in practice a considerably larger number of lamp groups. will '15 ordinarily be employed, the control elements being merely duplicated for each additional group of lamps, as'will be pointed out more clearly hereinafter.

, Included in circuit with the lamps of group I isa suitable current controlling or regulating devlce,'such as the dimmer rheostat 3. A manually-operable switch 4 is also included in circuit with thelamp's of group 1 to provide for connection of the lamps across lines L, L

Upon closure of the switch 4' the circuit for the l'amp-group'l will be completed, the intensity, of illumination of the lamps being dependent upon the position of the rheostat contact arm 5 of the dimmer rheostat 3. Said contact arm is shown in its lower extreme position and is adapted to be moved between said position and its upper extreme position to provide for gradual variation of the illumination intensity of the lamps between full-dark and full-bright illumination intensity.

Means-are provided to effect movement or adjustment of the rheostatwontact arm 5 from any given position thereof to any other position preselected therefor. More specifically, the means aforementioned provides for automatic movement of said, rheostat arm alternately in opposite directions between preselected positions. .The means for preselecting the positions between which the rheostat arm 5 is to be moved and for effecting movement of. said arm eomprises essentially a sending rheostat 6, having adjustable contact arms I and 8 associated therewith, a receiving rheostat 9 having an adjustable contact arm l0 associated therewith, and the coil Ii of a polarized relay of suitable form, said rheostats 6 and 9 and coil II being connected with respect to each other and with respect to lines L, L in the form of a Wheatstone bridge.

through one pole of the switch i8, armature A able, the pivoted ends of said arms being connected selectively to one side of the polarized relay coil ii through the normally closed contacts i2 and the normally open contacts ll, respectively, of an electromagnetically operable switch H. The other side of the coil Ii is connected to the pivoted end of the power-operated contact arm ill. r

The contactor I5 of the polarized relay is normally biased to an intermediate or neutral position, as illustrated, when the bridge circuit is in balanced condition, and the same is moved automatically into engagement with the stationary contacts I6, i'l, selectively, depending upon the direction of unbalance of the bridge circuit. The controlling effect of the Wheatstone bridge circuit and its associated parts is described in detail in my Patent No. 1,906,859, dated May 2, 1933.

The operation of the control system illustrated in Fig. 1 is as follows:

Assuming that the various elements of the control system are in the respective positions illustrated and that it is desired to provide a given illumination or lighting effect, the switch 4 is closed to connect the lamp group I across the lines L, L which represent a suitable source of alternating current supply.

Closure of the switch l8 connects the Wheatstone bridge circuit across lines L L, which represent a suitable source of direct current supply. Upon energization of the bridge circuit the rheostat contactor 5 will either remain in its lower extreme position or will be moved to vary the amount of resistance of rheostat 3 in circuit with the lamps, as determined by the relative positions of the contact arms 1, 8 and ill. The contactor 5 and the contact arm ID are shown as being mechanically connected with but electrically insulated from each other.

The contact arm 1 is shown as having been adjusted to a position slightly above its lower extreme position, thus providing for a relatively low intensity of illumination as the minimum intensity at which it is desired that the lamps of group I shall burn to obtain a given'lighting effeet. The contact arm 8 is shown as having been adjusted to a position which provides for substantially three-fourths bright illumination intensity as the maximum intensity at ch it is desired that the lamps of group i sh ...,:-:burn.

Thus upon closure of switch I! the Wheatstone bridge circuit will be energized, the circuit extending from line L through one pole of the switch l8, a small portion of the sending rheostat contact arm 1, normally closed contacts l2 of switch ll, through the polarized relay coil ll, contact arm Ill, through all of the receiving rheostat 9, and through the other pole of switch l8 to line L. The bridge circuit will be unbalanced due to the difference in the relative positions of the contact arms 1 and I0, consequently the direction of current flow through the coil II will be such as to move the contactor l5 into en-' gagement with the stationary contact I, establishing for the motor switch l9 an energizing circuit extending from line L through one pole of switch I8, winding of switch i9, contact II and contactor l5 of the polarized relay, and through the other pole of switch l8 to line L.

Switch l9 responds to establish for the motor M an energizing circuit extending from line LP and field F of said motor, through a portion of rheostat 20, contact arm 2|, switch I! and through the other pole of switch It to line 13 whereupon the motor M operates in a direction to move the contact arm in through the medium of the gear drive 35 upwardly on the receiving rheostat 9 into a position-corresponding to that of the contact arm I on the rheostat 6, thus balancing the bridge circuit and deenergizing motor M. Contactor 5, being mechanically connected to the contact arm III, is moved into a position on the dimmer rheostat 3 wherein a relatively low intensity of illumination of the group of lamps l is provided. I

Motor M is provided with a second field F adapted upon energization thereof to effect operation of the motor in the reverse direction. Included in circuit with the aforementioned field F is the rheostat 20 the contact arm. 2i of which is shown as having been adjusted to provide ior inclusion of substantially three-fourths of the resistance of said rheostat in circuit with said held for effecting operation of the motor at a relatively low speed. Included in circuit with the field F is the electromagnetically operated switch 22 and the rheostat 23, the contact arm 24 of which is shown as having been adjusted to provide for inclusion of substantially half of the resistance of the rheostat 23 in circuit with the field F. It will be readily apparent from the foregoing that the speed of movement of the contactor 5 in each direction over the dimmer rheostat 3 is controlled by adjustment of the respective rheostat contact arms 2| and 24.

Means common to the various groups of lamps such as groups I and 2 are provided to effect alternate energization and deenergization of the switches H at predeterminedintervals,whereby,as will be more clearly set forth in connection with lamp group I, the contact arms 1 and 8 are alternately rendered effective, causing unbalancing of the Wheatstone bridge circuit in opposite directions with consequent movementof the contactor 5 between positions on the dimmer rheostat 3 which correspond to the positions of the arms] and B on the sending rheostat 5.

The aforementioned cycling means comprises a set of normally open contacts 25 to 34, inclusive, which areadapted to be closed successively by the cams 35 to 45, inclusive. Said cams are fixed to a shaft 48 which is arranged to be driven by the motor 41 through the medium of the speed reducing gear driye' l8.

Associated with each of the groups of lamps i and 2 is a selector 50 and 5|, respectively. Each of said selectors comprises a number of stationary contacts 52 to SI, inclusive, said contacts being connected to the contacts 25 to 3, respec tively, of the cycling means. The contacts 52 to Bl of the selector 50 are arranged to be engaged selectively by the contactors '62 and 63, said contactors being manually adjustable to provide for control of the time at which the increase and the decrease, respectively, in illumination intensity of the lamps is initiated Upon closure of the switch the motor 41 is connected across lines L, L? and operates to drive the shaft in a clockwise direction (as indicated by the arrow) through the medium of the gear drive ll. The cam 36 is shown as having eiiected closure of the contacts 25 and as the shaft 45 continues to rotate the cams 31 to 45 effect closure "successively of the contacts 25 to 3!. The

:contactor 82 of the selector 50 is shown in encontacts 26, contact 53 and contactor 82 of selector 50, through the winding of switch I4 and through resistance 64 to line L.

the contact arm 8 of sending rheostat 6, contacts 65 of switch I4 also being closed and contacts I2 .thereof being opened. The Wheatstone bridge circuit will be unbalanced, the circuit therethrough extending from line L through one pole of switch I8, a portion of rheostat 6, contact arm 8, contacts I3 of switch I4, polarized relay coil II, contact arm III, which, as aforestated, will as aforedescribed. Response of switch I8 effects have moved to a position corresponding to the position of contact arm "I, through a portion of the receiving rheostat 9 and through the other pole. of switch I8 to line L.

Contactor I5 of the polarized relay will move .-into engagement with the stationary contact I8,

due to unbalancing of the bridge circuit, to establish for the motor switch I9 an energizing circuit I to substantially three-fourths full brightness thereof.

The circuit for the winding of switch I4 is maintained through contacts 55 of said switch:

Thus the maximum illumination intensity of the lamps of group I, as determined by the position of contact arm 8, is maintained until motor 41 has rotated shaft 48 far enough to effect closure of contacts 32 by cam 43, whereupon the winding of switch I4 is short-circuited, as is readily apparent. Switch I4- drops out to open the contacts I3' and 85 and to close the contactsv I2. Contact arm I again becomes effective and this time the bridge circuit becomes unbalanced in the opposite direction. Polarized relay con-' tactor I5 will be moved, into engagement with stationary contact I I to establish for motor switch 22 an energizing circuit extending from line L through one pole of switch I8, the winding of switch 22, contact I I and contactor I5 of the polarized relay, through the other'pole of switch I8 to line L Motor switch 22 responds to complete a circuit for energization of motor M extending from line I through one pole of switch I8, armature A and field F of said motor, through a portion of rheostat 23, contactor 24, switch 22 and the other pole of switch I8 to line L. Motor M operates in a direction to eflect movement of contact arm I downwardly into a position corresponding to that 01' contact arm I, and at a speed determined by' the setting of contact arm 24.

Thus contactor is moved over rheostat 8 to decrease the intensity of illumination of the lamps of group I to a value determined by the setting Response. ofswitch I4 closes contacts I 3 to render effective operation, rendering it extremely, convenient to work out a pleasing combination series or cycle of illumination eifects.

Now considering the lamp group 2, the adjustable elements of the control unit associated.

therewith are shown adjusted to positions differing from those of the'elements associated with the lamp group I. Contact arm 61 of the sending rheostat 65 is shown in a position which provides for substantially one-fourth bright illumination intensity of the lamps, while contact arm 68 is shown in a position which provides for substantially seven-elghts bright illumination intensity of said lamps.v Contact arm 88 of motor rheostat I0 is shown in a position which provides for a relatively rapid increase in illumination intensity of the lamps of group 2', while contact arm II of motor rheostat I2 is shown in a position which provides for a relatively slow or gradual decrease in illumination intensity of said lamps.

As aforestated, contacts 52 to SI of selector 5I are electrically connected to the contacts 25 to 34, respectively. For purposes of illustration the wires connecting said contacts are shown as being contained in a conduit I5. Said conduit is indicated as extending beyond the selector 5| inasmuch as the contacts of selectors associated with additional lamp circuits may be electrically connected to the contacts 25 to 34 through the medium of the wires contained in said conduit, as will be apparent.

Selector 5| has associated therewith contact arms 13 and I4. Contact arm 13 is shown as having been moved into engagement with stationary contact 55, which contact is electrically connected with'the stationary contact of the aforementioned set 28. Thus when closure of contacts 28 is effected by cam 39 contact arm 68 of sending rheostat 81 will be rendered eifective with results similar to those aforedescribed in.

connection with the lamp group I. Contact arm 14 is shown as having been moved into engagee ment with contact 60, which contactis electrically connected with the stationary contact 'of set 33. When closure of contacts 33 is effected by cam 44 contact arm 81 will be rendered effective with results similar to those aforedescribed in con'- nection with the lamp group I.

The control elements of the aforedescribed system are preferably arranged upon a control panel in a manner to provide for convenient arrangement of the manually operable elements of the system upon the face of said panel. For example, a portion of such a control panel is illustrated at 18 in Fig. 3,v showing the arrangement of the manually adjustable contact arms associated with the control units for three groups of lamps. The handles of the contact arms .1, 8, 2 I, 24, 52 and 63 associated with the lamp group I,

1 are shown as comprising the group at the lefthand side of the panel; the group of handles in the center of the panel comprise those of the contact arms 81, 88, 58, II, 13 and 14, associated' with the group of lamps 2. The group of handles at the right-hand side of the control panel comprise those of contact arms II. to 82, inclusive,

associated with an additional group of lamps lighting effects willbe produced of substantially the character illustrated diagrammatically in Fig. i. It may be assumed that the lamps in each of thegroups I and 2 and the lamps in the group associated with the contact arms I! to 02 are of diil'erent colors. For example, the lamps of group I may be white, the lamps of group 2, red, and the lamps of the group with which the contact arms 11 to 02 are associated may be blue, as indicated by the letters, W, R and B in Fig. 4, which designate the respective lighting curves of the individual illumination circuits.

One division of the "time scale indicated in Fig. 4 represents the interval between closure of two successive cam switches 20 to 24. Thus with ten cams as illustrated in Fig. l a complete cycle of the illumination control is represented by ten divisions on the "time" scale. Referring to the curve W it will be noted that the rise in the curve, representing voltage increase, begins at the second moment of the "time scale which is determined by the position of contact arm 62 of selector 00. The rise of the curve W indicates a relatively gradual increase in voltage as provided for by the setting of the contact arm II on the motor rheostat 20. The fall in the curvew, representing voltage decrease, begins at the eighth moment of the "time" scale as determined by the position of contact arm 41 of selector 50. The rate of voltage decrease, as aforedescribed, is determined by the setting of contact arm 2'. of motor rheostat 21.

The curves R and B portray respectively, the voltage characteristics of the lamps of group 2 and the lamps of the group controlled by the contact arms I1 to 02, as determined by the illustrated settings of the contact arms associated with each group. Due to the setting of the contact arms I9 and 14, l1 and II the cycles of illumination control of the latter groups of lamps, as portrayed by curves R and B. respectively, are out of phase with the cycle portrayed by curve W and out of phase with each other.

Referring to Fig. 2, the voltage of the lamps of groups I and 2 is controlled through the medium of the saturable reactors 90 and III, respectively. The lamps are connected across lines 'L and U, the lamps of group I being connected in series with the alternating current coils 92 of the saturable reactor 90 and the lamps of group .2 being connected in series with the alternating current coils 93 of the saturable reactor II. The reactors 90 and 9| are provided with the direct current control windings 94 and 95, respectively, each of said windings being connected in series with an electron tube 99 across the lines L and L. Each of the reactor control windings 94 and 95 has connected in parallel therewith an electron tube 91, the purpose of which is to smooth out the ripples of the current inthe windings as supplied through the tubes 00. v

Associated with each of the lamp groups I and 2- is a transformer 90 having a primary winding 90! connected in'parailel with the lamps. One terminal of the secondary winding is connected with the control grid of tube 90 and the other terminal is connected with the anode 09* of a double anode electron tube 99. The cathodes of tubes 90, 91 and 00 may be heated in any wellknown manner. A second transformer I00 has a primary winding I00 which is adapted to be connected selectively through the normally closed contacts I02 of a switch IIII with the pivoted end of contact arm I or through the normally open contacts I02 of said switch (when closed) with the pivoted end of contact arm 0.

Contact arms 1 and I are associated with a rheostat I01 and are employed as described in connection with Fig. 1 to pre-select'the minimum and maximum intensities of illumination at which cuit consisting of a condenser I08 and a resistor I09 connected in parallel therewith. A second energy storage discharge circuit consisting of a condenser H0 and a parallel resistor III is connected in series with the secondary winding I00" of transformer I00 between anode 99 and the cathode of tube 99.

In accordance with the teachings of the patent of Carroll Stansbury, No. 2,024,838 dated Dec. 17, 1935, additional energy storage discharge circuits are provided as indicated by the numerals H2, H3, H4 and H5. Each of the last-mentioned circuits preferably possesses predetermined discharge characteristics diifering from any of the other of said circuits in order to provide various rates of increase and decrease in illumination intensity of the lamps.

By means of the contact arms 2I and 24 and the stationary contacts H6, H1, H9, H9, I20 any one of the energy storage discharge circuits I I2, III, I I4, I I may be selectively connected in parallel with the energy storage circuit consisting of the condenser I I0 and the resistor I I I to modify the discharge characteristic thereof as described in detail in the aforementioned Stansbury patent.

The cycling means comprising the cam operated switches 25 to 34 and associated mechanism, and the selectors 50 and 5| are essentially identical with the corresponding devices shown in Fig. 1. Thus considering operation of the system controlling the illumination intensity of the lamp group I as shown in Fig. 2, closure of switch 4 will connect the lamps across lines L, L. Said lines represent an alternating current constant potential source of supply. Closure of switch 49 connects motor 41 across lines L, L". Said motor drives shaft 46 to -eifect closure of switches 25 to 34 successively, as aforedescribed. Contact arm 02 of selector 50. being in engagement with the stationary contact 53 completes an energizing circuit for switch IOI upon'closure of contacts 29 of the timing means. Switch IOI responds to close its contacts I03, I05 and I06 and to open its contacts I02 and I04. Closure of contacts I04 provides a maintaining circuit for switch I0 I.

Closure of contacts I03 renders effective the contact arm 8 of rheostat I01 while closure of contacts I05 renders effective the contact arm 2 I, whereupon energization of winding 94 of reactor 90 is increased to a value determined by the setting of contact arm 8 and at a rate modified by the characteristics of the energy storage discharge circuit II3. As is well known, variations of the current in the winding 94 produce variations in the voltage drop'across the coils 92 with consequent variations in the value of current supplied to the lamps.

The maximum intensity of illumination of the lamps of group I is maintained at the value determined by the setting of contact arm 8 until contacts 32 of the timing means are closed, with consequent short-circuiting of the winding of switch I0 I. Closureof contacts I02 renders contact arm I effective while closure of contacts I04 renders contact arm 24 eifective. The current in winding 94 will be decreased to a value determined by the setting of contact arm 1 thus reducing the intensity of illumination of the lamps. The rate of decrease of current in winding 94 is modified by the characteristics of the discharge circuit I ll.

The minimum illumination intensity of the lamps will be maintained at the value determined by the set ting of contact arm 1 until con- 'tacts 2B of the timing means are again closed.

The foregoing cycle of control will be automatically repeated so long as the system is energized.

As stated in the aforementioned Stansbury Patent No. 2,024,838,,the design of the' circuits H2, H3, H4, H5 depends upon'the desired rate of change in illumination intensity. Obviously,

the flexibility ofsthe system may be increased by the addition of circuits similar to circuits H2, I H,

H4 and H5, it being understood that for each circuit thus added an additional contact corresponding to contacts I Hi to I20 will be required.

In the system illustrated in Fig. 2, contact arms I and 8 of rhcostat I01, contact arms 61 and 68 of rheostat l 2 l contact arms 62 and 53 of selector 5!] and contact arms 13 and 14 of selector 5| are shown in control positions corresponding to those of the corresponding contact arms associated with the system illustrated in Fig. 1. It may be assumed that the control positions in which contact arms 21 and 24, 69 and H are shown in Fig. 2. provide for rates of illumination intensity in-- invention herein disclosed the general characteristics of the illumination cycle with reference to time may be varied either by providing means for. varying the speed of motor t! or by substituting a suitable variable speed transmission for the gearing i8.

If it is desired to vary the illumination in tensity between several maxima and minima during one complete cycle as provided by sequential operation of all of the cams 36 to 45, inclusive, the contacts 25 to 34, inclusive, controlled thereby may be interconnected electrically in the manner shown in Fig. 5, for instance, to provide for repetition of any given illumination effect two or more times during each revolution of the cam shaft 46. By this means I am enabled to stand-= ardize on the reduction gearing employed and upon the number of cams employed, regardless oi the number of illumination intensity variations desired in one control cycle, such means providing for changing the periods of variationin one direction or the other at will to suit the requirements of each particular installation.

The arrangement shown in the fragmentary diagram, Fig. 5, includes only the three stationary contacts of the cam operated sets 25, i6, 21 for,

purposes of illustration. Each of said contacts has connected thereto a jack receptacle 25 26 Zi etc., and a plug jack 25 26 27', etc., it

the contacts '52- to El of selector 50 which are engaged by the contactors 62 and $3. It is to bennclerstood that with the arrangement just described each of the conductors connecting the contacts '52 to 6| of selector 5| to said contacts 25 to 34 would also be provided with a jack receptacle and a plug jack.

I also desire to point out that by providing additional contactors like those designated by the numerals 62 and E3 (of selector 50) I may increase the number of illumination intensity changes for any circuit during each revolution of shaft 46 while providing a smaller number of illumination intensity changes for any other circuit during such revolution of said shaft 46.

In connection with the control system illustrated in Fig. 2, it is to be understood that the lighting curves shown in the diagram, Fig. 4,

while retaining substantially the outline there illustrated, will be modified as described and illustrated in the aforementioned Stansbury Patent- 1. In an illumination control system, in combination, a group of electric lamps, illumination intensity regulating means for said lamps, means for operating said regulating means between limits determining the minimum and maximum values of intensity of illumination of said lamps; said last mentioned means comprising a sending impedance and a receiving impedance connected in parallel in the form of a Wheatstone bridge, the balance of which determines the said limits of operation of said regulating means, said sending impedance having a pair of elements which are selectively effective eachto determine a point of balance of said bridge, whereby to select a minimum and a maximum intensity of illumination, respectively, for said lamps, associated means operable by unbalance of said bridge automatically to restore balance of said bridge at one or the other of said points depending upon which of said elements is effective, and simultaneously to operate said regulating means to provide for sequential and gradual decrease or increase in the intensity of illumination of said lamps; means as-- soclated with the last named restoring-means to render the same operative at a predetermined rate during said decrease of intensity of illumination and at a second'predetermined rate during said increase of intensity of illumination, and power operated means to respectively time initiation of the decrease and the increase in said intensity of illumination with reference to a given cycle by rendering one or the other of said elements effective.

2. In an illumination control system, incoming a sending rheostat and a receiving rheostat arranged in the form of a Wheatstone bridge, a

contactor associated with said receiving rheostat and adapted to be driven in opposite directions by said motor, said sending rheostat having a pair of contactors each adjustable individually to de- 'termine a point of balance of said bridge, whereby to preselect the limits of movement of said receiving rheostat contactor and said impedance element in opposite directions respectively, means for rendering said sending rheostat contactors effective alternately for predetermined periods of time with reference to a given cycle, means responsive to unbalance of said bridge to selectively establish power connections for said I motor to effect operation thereof in one direction or the other and tending to restore balance of said bridge at one or the other of said points depending upon which of said sending rheostat contactorsis effective, and simultaneously to move said impedance element to provide for sequential and gradual decrease or increase in the intensity of illumination of said lamps, and means to preselect the speeds of said motor for each direction or operation thereof. s

3. In an illumination control system, in combination, a group of electric lamps, illumination intensity regulating means for said lamps, said means comprising a resistance element and a contactor movable with respect to said resistance element, a reversible electric motor for eilecting movement of said contactor in opposite directions, follow-up control means for said motor comprising a sendingrheostat and a receiving rheostat connected in the form of a Wheatstone'bridge, a contactor associated with said receiving rheostat and adapted to be driven in opposite directions by ,said motor, said sending rheostat having a pair I of contactors each adjustable individually todetermine a point of balance of said bridge, whereby to preselect the limits of movement of said receiving rheostat contactor and said regulating resistance contactor in opposite directions respectively, means for rendering said sending rheostat contactors effective selectively for predetermined periods of time with reference to a given cycle, means responsive to unbalance of said bridge to selectively establish power connections for said motor to effect operation thereof in one direction or the other and tending to restore balance'of said bridge at one or the other of said points depending upon which of said sending rheostat contactors is eflective, said last mentioned means comprising a polarized relay coil connected in said Wheatstone bridge circuit and a contactor associated with said coil, said contactor being normally biased to an intermediate position and the same being movable by said coil in one direction or the other accorde ing to the sense of unbalance of said bridge, a I

pair of contacts to be engaged by said contactor selectively upon movement thereof in one direction orthe other, and means to preselect the speeds of said motor for each direction of opera-v tion thereof. v

4. In an illumination control system, in combination, a lamp circuit, illumination intensity control means comprising a resistance element included in said lamp circuit and a contactor movable with respect to said resistance element, a reversible electric motor for eflecting movement of said contactor in one direction or the other, follow-up control means for said motor coinprlsing a sending rheostat, a receiving rheostat and a polarized relay coil arranged in the form of a Wheatstone bridge, a contactor associated with said receiving rheostat and adapted to be driven by said motor, a pair of contactors associated with said sending rheostat, said last mentioned contactors being manually adjustable individually to determine a point of balance of said bridge,-whereby to preselect the limits of movement of said receiving rheostat contac'torin opposite directions respectively, an electromagnetically operable switch adapted when de-energized to render effective one of said sending rheostat contactors, said switch being adapted when energized to altera V nativeiy render effective the other of said sending rheostat contactors, means for sequentially effecting energization and deenergization of said switch for predetermined periods of time, a contactor associated with said polarized relay coil, said contactor being normally biased to an intermediate position and the same being movable by said coil in one direction ,or the other according to the sense of unbalance of the Wheatstone bridge, a pair of contacts to be engaged by said contactor selectively upon movement thereof in one direction or the other, said contacts when entensity regulating'means for said lampsymeans for operating said regulating means between limits determining the minimum and maximum values of intensity of illumination of said lamps; said last mentioned means comprising a sending impedance and receiving means connected with the latter in the form ofa balancing control circuit, the balance of which determines the said limits of operation of said regulating means, said sending impedance having a pair of elements which are'selectively effective each to determine a point of balance of said circuit, whereby to select a minimum and a maximum intensity of illumination, respectively, for said lamps, associated means operable by, unbalanceof said circuit automatically to restore balance of said circuit at one or the other of said points depending upon which of said elements is effective, and simultaneously to operate said regulating means to provide for sequential and gradual decrease or increase in the intensity of illumination of said lamps; means associated with said last named restoring means to render the same operative at a predetermined rate during said decrease of intensity of illumi-. nation and at a second predetermined rate during said increase of intensity of illumination; and power operated'means to respectively time initiation of the decrease and the increase in said intensity of'illumination with reference to a given cycle'b'y rendering one or the other of said elements. eifective.

6. In an illumination control system, in cornbination, a group ofelectric lamps, illumination intensity regulating means for said lamps, means for operating said regulating means between limits determining the minimum and maximum values of intensity of illumination of said lamps; said last mentioned means comprising a sending impedance and follow-up means connected with the latter in the form of a balancing control circuit, the balance of ,which determines the said limits of operation of said regulating means, said sending impedance having a pair of elements which are selectively effective each to determine a point of balance of said circuit, whereby to select a minimum and a maximum intensity of illumination, respectively, for said lamps, associated means operable by unbalance of said circuit automatically to tend to restore balance of said circuit at one or the other of said points depending upon-which of said elements is eifec- 'tive, and simultaneously to provide for sequential and gradual. decrease or increase'in the intensity of illumination of said lamps; means-associated with said last named restoring means to render the same operative at a predetermined rate during said decrease of intensity or illumination and .r

at a second predetermined rate during said increase of intensity of illumination; and power operated means to respectively time initiation of the decrease and the increasein said intensity of illumination with reference to a given cycle by rendering said elements efiective alternately, whereby to effect decrease and increase in the intensity of illumination of said lamps between said minimum and maximum values in a regularly recurring cycle.

7 In an illumination control system, in combination, a group of electric lamps, illumination intensity regulating means for said lamps, means for operating said regulating means between limits determining the minimum and maximumvalues of intensity of illumination of said lamps; said last mentioned means comprising a sending impedance and receiving means connected with the latter to provide a balancing control circuit, the balance of which determines the said limits of operation of said regulating means, said sending impedance having a pair of elements which are selectively eiiective each to determine a point of balance of said circuit, whereby to select a minimum and a maximum intensity of illumination, respectively, for said lamps, associated means operable by unbalance of said circuit automatically to tend to restore balance of said circuit at one or the other of said points depending upon which of said elements is eiiective, and simultaneously to operate said regulating means to provide for sequential and gradual decrease or increase in the intensity of illumination of said lamps; means associated with the last named restoring means to render the same operative at a predetermined rate during said decrease of intensity of illumination and at a second predetermined rate during said increase of intensity of illumination, whereby to select the periods of dwell or unchanging minimum and max mum intensities of illumination of said lamps with respect to a given cycle; and power operated means to respectively time initiation of the decrease and the increase in said intensity of illumination with reference to said cycle by rendering said elements 1 effective alternately.

8. In an illumination control system, in combination, a plurality of groups of electric lamps, each of said groups of lamps having illumination intensity regulating means individual thereto, each of said regulating means having means tween limits determining the minimum and maximum intensities of illumination of said group of lamps; said last mentioned means comprising a sending impedance and receiving means connected with the latter to provide a balancing control circuit, the balance of which determines the said limits of operation of said regulating means, said sending impedance having a pair of elements whichare selectively effective each to determ ne a point of balance of said circuit, whereby to select a minimum and a maximum intensity of illumination, respectively. for said group of lamps, associated means operable by unbalance of said circuit automatically to tend to restore balance of said circuit at one or the other of saidpoints depending upon which of said elements is effective, and simultaneously to operate said regulating means to provide for sequential and gradual decrease or increase in the intensity of illumination of said group of lamps; means associated with the last named restoring 'rneans to render the same operative at a predetermined rate dur ing said decrease of intensity-or illumination and at a second predetermined rate during said increase of intensity of illumination; and common power operated means including adjustable parts associated with the said individual operating 'means to respectively time the initiation or the decrease and the increase in said intensity of illumination with reference to a. given cycle by rendering one or the other of said elements eftective, whereby the. decreasing or increasing or unchangingintensities of illumination of the respective groups of lamps are controlled in a predetermined relationship.

.9. In an illumination control system, in combination, a plurality of groups of electric lamps, each of said groups of lamps having illumination intensity regulating means individual thereto, each of said regulating means having means associated therewith for operating the same between limits determining the minimum and maximum values of intensityof illumination of said group of lamps; said last mentioned means comprising a sending impedance and a receiving impedance connected in parallel in the form of a Wheatstone bridge, the balance of which determines the said limits of operation of,said regulating means, said sending impedance having a pair of elements which are selectively effective each to determine a point of balance of said bridge, whereby to select a minimum and a maximum intensity of illumination, respectively, for said group of lamps, associated means operable by unbalance of said bridge automatically to tend to restore balance of said bridge at one or the other of said points depending upon which of said elements is eiiective, and simultaneously to operate saidregulating means to provide for sequentialand gradual decrease or increase in the operating means for said regulating means to respectively time the initiation of the decrease and the increase in said intensity of illumination with reference to a given cycle by rendering one or the other of said elements effective, whereby the decreasing or increasing or unchanging associated therewith for operating the same bei intensities of illumination of the respective groups of lamps areocontrolled in a predetermined rela tionship.

id. In an illumination control system, in corn bination, a plurality of groups of electric lamps, each oisaid groups of lamps having illumination intensity regulating means individual! thereto, each oi said regulating means having means associated therewith for operating the same between limits determining the minimum and maximum values of intensity of illumination of said group of lamps; said last mentioned means comprising an electric valvehaving a grid and adapted to vary the impedance oi said regulating means in accordance with the conductivity of said valve, as sending impedance having a pair of elements which are selectively effective each to determine a value of voltage to be impressed upon said grid, whereby to select a minimum and a maximum intensity oi! illumination, respectively, for said group of lamps; means having an inherent time function for effecting changes of said grid voltage and thereby simultaneously to vary the impedance oi said regulating means to provide for sequential and gradual decrease or increase in the intensity of illumination of said group oi lamps between iii) said selected minimum and maximum values. means associated with said last named means to selectively modify the time function thereof, whereby to render the same operative at a predetermined rate during said decrease of intensity of illumination and at a second predetermined rate during said increase of intensity of illumination; and common power operated means including adjustable parts individual to each of the operating means for said regulating means to respectively time the initiation of the decrease and the increase in said intensity of illumination with reference to a given cycle by rendering said elements effective alternately, whereby the decreasing or increasing or unchanging intensities of illumination of the respective groups of lamps are controlled in a like relationship for repeated cycles.

11. -In an illumination control system, .in combination, a group of electric lamps, illumination intensity regulating means for said lamps comprising a variable impedance device, means comprising an electric valve having a control grid and adapted to vary the impedance of said regulating means in accordance with the conductivity of said valve between limits determining the minimum and maximum values of intensity of illumination of said lamps, means for varying the conductivity of said valve, said means comprising a sending impedance having a pair of elements which'are selectively effective each to determine a value of voltage to be impressed upon said grid, whereby to select a minimum and a maximum intensity of illumination, respectively, for said lamps, means having an inherent time function for effecting changes of said grid voltage and thereby simultaneously to vary the im pedance of said regulating means between said limits, means associated withsaid last named means to selectively modify the time function thereof, whereby to render the same operative at a predetermined rate during said decrease of intensity of illumination and at a second predetermined rate during said increase of intensity of illumination; and power operated means to respectively time initiation oi the decrease and the increase in said intensity of illumination with reference to a given cycle by rendering said elements effective selectively. v

12. In an illumination control system, in combination, a group of electric lamps, a variable impedance device for regulating the illumination intensity of said lamps, means for varying the impedance of said device between limits determining the minimum and maximum values of illumination intensity of said lamps; said last mentioned means including an electric valve having a grid for controlling its conductivity in accordance with the voltage impressed upon said grid, means comprising a sending impedance having a pair of elements which are selectively effective each to determine a value of voltage to be impressed upon said grid, whereby to select a minimum and a maximum intensity of illumination, respectively, for said lamps, an energy storage circuit connected to said grid, andmeans having an inherent time function for controlling the changes in said grid voltage and thereby simultaneously varying the impedance of said device between the said limits, means associated with the last named means to selectively modify the time function thereof, whereby to render the same operative at a predetermined rate during said decrease of illumination intensity and at a second predetermined rate during said increase of illumination intensity; and power operated means to respectively time initiation of the decrease and the increase in said illumination intensity with reference to a given cycle by rendering one or the other of said elements effective.

13. In an illumination control system, in combination, a source of electric power, an electric valve having a grid for controlling its conductivity in accordance with the voltage impressed upon said grid, a lamp circuit connected to said source and to said valve and whose voltage varies in accordance with the conductivity of said valve, an energy storage circuit connected to said grid having an inherent time function and adapted 'to vary the voltage impressed thereby upon said grid, and means comprising a plurality of energy storage circuits having different discharge characteristics which are selectively effective to modify the time function of ,said first named storage circuit, whereby said grid voltage is varied at a selected rate.

14. In an illumination control system, in cor L'- bination, a group of electric lamps, illumination intensity regulating means for said lamps, means for operating said regulating means between limits determining the minimum and maximum values of intensity of illumination of said lamps, said last mentioned means comprising an electric valve having a grid and adapted to vary the impedance of said regulating means in accordance with the conductivity of said valve, a sending impedance having a pair of elements which are selectively effective each to determine a value of voltage to be impressed upon said grid, whereby to select a minimum and a maximum intensity of illumination, respectively, for said lamps, an energy storage circuit connected to said grid having an inherent time function and adapted to,

vary the voltage impressed upon said grid and thereby simultaneously to vary the impedance of said regulating means to provide for gradual decrease or increase in the intensity of illumination of said lamps between said selected minimum and maximum values, means comprising a plurality of additional energy storage circuits having different discharge characteristics which are selectively effective to modify the time function 'of said first mentioned energy storage circuit, whereby to render the Latter operative at predetermined rates during the decrease or the increase in the intensity of illumination, and power operated means to respectively time initiation of the decrease and the increase in said intensity of i1- lumination with reference to a given cycle by sequentially rendering one and then another of said last mentioned energy storage circuits effective.

RICHARD B. HUNTER.

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