US1365545A - Lighting system - Google Patents

Description

Patented Jan. 11, 1921.

2 SHEETS-SHEET I.

H. D. ROHMAN.

LIGHTING SYSTEM.

APPLICATION Hm) ocr. 1. 1918.

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H D. ROHMAN.

LIGHTING SYSTEM.

APPLXCATIQN FILED 0e11, 1918.

Patented Jan 11 1921.

2 SHEETS-SHEET 2.

UNITED STATES HARRY D. ROHMAN, or NEW YORK, 1v. Y.

LIGHTING SYSTEM.

Application filed @ctoher 1, 1918.

T 0 all 4.0 7mm it may concern Be it known that I, HARRY D. R HMAN, a citizen of the Republic of Switzerland, and residing at New York city, in the county of New York and State of New York, United States of America, have m vented certain new and useful Improvements in Lighting Systems, (Case No. 20,) of which the following is a specification.

This invention relates to lighting systems such as used for example, in lighting and heating railway vehicles and the like. and the nature of my invention and its objects and advantages will be best understood from a brief statement of the defects in standard systems which it is intended to overcome.

The invention has to do primarily with the maintenance of proper voltage on the lamp or other translating circuits, while the generator is the source of supply, and heretofore, in train lighting systems, it has been customary to follow one of two general methods. By one method, which is most commonly followed, the dynamo current must pass through a resistance element. which is given such a value that the proper amount of current at the proper pressure w1ll be passed to the lighting circuit, assuming that all of the lamps are lighted, this resistance being shortcircuited when the dynamo cuts out and the battery is supplying the lamps. The difficulty with this system is that it is inadequate to take care of conditions which arise out of subcontrol of the various lamps of the lighting circuit. In such arrangement, for example. when one or more lamps is, or are, switched off, the ohmic value of the circuit is increased which occasions an increase in voltage across the lighting circuit because of the fact that the resistance element now has too low a value to pass the proper amount of current at the proper pressure, and the lamps burn too brightly and burn out very rapidly. Similarly, if a number of lamps be added to the circuit, then the ohmic value of the circuit is decreased and tie voltage falls, the resistance element then having too high value to pass the proper amount of current at the proper pressure to the lighting cir cuit. It will also be apparent that similar fluctuations in volt ge will take place by the substitution of new lamps of different value place of lamps having a value for which the stem was initially designed.

[By the other method commonly followed,

Specification of Letters Patent.

Patented Jan. 11, 1921.

Serial No. 256,381.

the lamp voltage is maintained constant by complicated regulating mechanism which, as is well-known, does not function uniformly, unless carefully maintained. Vhile both systems approximate fair lamp voltage regulation, they fall short of obtaining accurate regulation. 7

It is the purpose of my invention to provide a simple and efficient means for obtaining very close lamp voltage regulation, and in one of its broader aspects my invention consists, inter alia, in the utilization of a regulating resistance element, the condition of which will always be in uniformity, or in step, with the conditions obtaining throughout the entire system. Further, I propose to use the battery itself to regulate the lamp voltage.

l accomplish the foregoing, together with such oth r objects as may hereinafter appear. by means of apparatus which I have illustrated in preferred form in the accompanying drawings, wherein:

Figure 1 is a diagram of a lighting system reduced to its simplest form and illus trates the application of my improvements; and Fig. 2 is a diagram in which the details of the system are more fully developed.

Referring now to the simple diagram of Fig. 1, A indicates a dynamo which is preferably of the speed controlled type such, for example, as a slipping belt dynamo in which the belt which is driven from the car axle. slips on the dynamo pulley when the train attains a speed at which the dynamo develops full output, say for example, at 535 miles per hour. After this speed is attained, the armature rotates at a substantially constant speed regardless of variations in train speed,

as is well understood by those skilled in this art. The battery is indicated at B, such bat tery, for the purpose of this description, being an Edison 28 cell battery. The positive and negative main leads arerespectively indicated at '7 and 8. But one lighting circuit D is illustrated, the positive 12 of such lighting circuit being connected to the positive 7 through the iron wire resistance r, and the negative 12 being connected to negative 8. The lighting circuit is controlled by the main switch 13 and the positive 12 is also adapted to be connected to the positive 7 by means associated with the automatic cutin and out switch C, when the battery is supplying the lamps and the dynamo is out out. The automatic cut-in switch C may be of any preferred type and is constructed to close when the dynamo voltage has been built up to a point where it is equal to or greater than that of the battery, and to open when the dynamo voltage drops below that of the battery, as is well understood.

When the cutin switch is open, positive 12 is connected to positive 7, on the battery side of the cut-in switch in such manner as to shortcircuit resistance r through the me dium of contact 17, brush 16 and wire 15. lVhen the cut-in switch has reached closed position, the plunger of the switch lifts brush 16 out of engagement with contact 17 and the dynamo supplies the lighting circuit through resistance r. lVhen the cut-in switch is in closed position, it also directly connects the positive 12 to regulating wire 20 through the medium of brush 21 and con tact 17, such regulating wire 20 being connected to the battery at a point intermediate its ends. The function and the operation of the regulating wire will be clear from the following, the description being based on the assumption that approximately average charging conditions obtain.

Assuming that the battery to be used in connection with the equipment is made up of 23 Edison cells, it will require a charging voltage of 1.7 volts per cell for a definite charging rate. This calls for a charging voltage or a generator voltage of 39 volts. Assuming now that the lamps should burn at 31 volts; that is to say, at the voltage of the battery when the latter is on discharge, it will be clear that the resistance 7' must absorb 8 volts in order to operate the lamps at the proper voltage. If now one of the lamps in circuit D be switched oil, as hereinbefore pointed out, the voltage across the lighting circuit will rise and insufiicient current will pass through resistance r to properly load such resistance; 1'. .63., to bring its tempera ture to the point where the resistance will be such as to pass the proper amount of current at the proper pressure.

In order to provide efficient and accurate regulation, I intend to use a portion of the battery itself as a regulating element, and to this end I connect the wire 20 preferably to the fifth cell from the positive end of the battery, and since each cell is at a voltage of 1.7, the drop from the positive to the regu lating wire will be 8.5 volts giving the regulating wire a potential of approximately volts, or substantially the required or preferable lamp voltage. Stated in other words, I prefer to connect the regulating wire 20 to the battery at a point where the back E. M. F. within the battery when on charge is equal to the required lamp voltage.

Assuming nowthat the cut-in switch is closed and the dynamo is generating a voltage sufiicient to produce a proper current in wire 12, and that wire 20 has been connected to positive 12 by brush 21, it' a lamp now be switched off in circuit D, the following phenomenon will result. The resistance through the translating circuit will immediately rise and be temporarily higher than the resistance through wire 20 and that portion of the battery between said wire and the main 8, and a portion or the dynamo current, after it has passed through resistance '1, will divide, the major portion flowing to the lamps and the remainder flowing to the 18 cells of the battery, through contact 17, brush 21, and wire 20, in the direction of the arrow 22.

Since the voltage between the point where the wire 20 is connected to the battery and the main 8 is substantially equal to the required lamp voltage, the aforementioned flow of current through wire 20 in the dircction of the arrow marked 22 will take place, n an amount corresponding to the increase n potential across the lamp circuit, which increase results from the cutting out of the lamp,

Stated in other words, the Wire 20 provides a parallel path for dynamo current which will take the current theretofore supplied to the lamp cut out, thus maintaining the proper lamp voltage on the remaining lamps. In the absence of the regulating wire 20, upon increase in resistance in the lighting circuit, there would be a drop in the current passing through resistance '1, but by the provision of the regulating wire providing another path to the battery in parallel with the lamps, the current flowing in the direction of arrow 22 will immediately load up the resistance r and at once assist in reestablishing the predetermined lamp voltage. Should an additional lamp be switched off, the complete cycle of operation will again take place, with a. correspondingly larger flow in the direction of arrow 22.

Contrarywise, should the lamp current increase as, for example, by the provision of additional lamps, it will be obvious that the regulating wire 20 will immediately convey the necessary amount of current but in the opposite direction, as indicated by arrow 23,

and so compensate for the insuiliciency of 1 current passing through resistance r. Thus. the regulating wire will automatically compensate for increase or decrease in load and maintain substantially constant potential across the lamp circuit.

It might appear as though the foregoing arrangement would unequally, affect the cells. Thus, for example, if the current flows in the direction of arrow 22, it will be apparent that the 18 cells of the battery will receive a charge slightly in excess of the value received by the first 5 cells. This. in a measure. will be counteracted by the fact that during the cutting out of the generator, the last 18 cells will temporarily sustain the lamp voltage until the cut-in switch is fully opened and shortcircuits resistance r. This result can be readily achieved by properly constructing the brushes 21 and 16 and designing the gaps between the respective brushes and the contact 17 in proper proportions. This unequal charge is also counteracted by the fact that should the current in wire 20 flow in the direction of arrow 23, there will be a drop in the potential across the first 5 cells, as a result of which the dynamo will pass more current into the first 5 cells. However, to insure substantially uniform charge, I provide a mechanism hereinafter to be described.

In addition to the advantages of constant lamp voltage regulation, the apparatus is peculiarly advantageous as applied to certain types of accumulators in which there is a disposition to an abnormal gassing voltage immediately after stopping the charge. Heretofore the lamp voltage, for a brief period, would rise because of the gassing voltage and noticeable fluctuations were inevitable. By calibrating the opening between brush 21 and contact 17 in such manner that current can be drawn from the last 18 cells for a brief period during the operation of the cut-in switch, this gassing voltage can be so reduced as to make the changes in voltage between running and stopping substantially negligible. This, to a large measure, will counteract any slight excess charge the 18 cells may have received Itwill be observed that the regulation atforded by the battery through wire 20 will always be in accord with conditions throughout the system, because the condition 111 the last 18 cells in the battery will always be in step or in uniformity with the conditions ob: taiiiing throughout the system. Thus, if the battery be in a low state of charge, and the cut-in switch closes when the dynamo voltage becomes equal to that of the battery, the voltage across the lighting circuit will he correspondingly low, and if a lamp be switched off at such time, the regulating wire 20 will function as described so as to preventflickering of the lamps. Under such conditions the lamps would, of course, be operated at a low voltage, corresponding to the low voltage obtaining throughout the system. and the voltage would gradually 1ncrease as the battery again becomes charged. Flickering of the lamps, however, would be prevented by the regulatmg wlre. FllCl ing of the lamps is also prevented at the time wire 20 is connected to wire 12 because it is preferable to make the connection at a time when the voltage across the lamp circuit 1s approximately equal to the voltage across the 18 cells of the battery. By properly designing the cut-in switch so as to sensitively respond, this result can be readily achieved.

In connection with the foregoing, it is to be observed that the arrangement is particularly advantageous with an Edison cell battery because the charging voltage rises very rapidly, the curve rising abruptly and then tapering off gradually. Thus, if the battery be well depleted, the lamps will operate on low voltage for but a comparatively short period of time. \Vith batteries of other types, the voltage of the lamps will gradually increase, as before pointed out, the regulating device operating to prevent flickering during low voltage periods and to prevent flickering and maintain constant potential on the lamps as the battery approaches full charge.

Another advantage of my invention is that while heretofore in certain types of slipping belt train lighting systems it has been attempted to obtain lamp voltage regulation through the medium of two batteries, one of which floats on the lamps while the other is on charge, I am. enabled to obtain eflicient regulation by the use of but a single battery and without the utilization of any a moving parts other than those which are essential to any lighting system.

Referring now to the complete system illustrated in Fig. 2, it will be seen that I have grouped the lamps in a plurality of suitable circuits a, b, and 0, each circuit being adapted to be connected to the main lighting positive 12 by means of respective switches (Z, c and f. I have also provided a separate iron wire resistance for each circuit, respectively numbered 32, 33 and 34. These resistances are connected in parallel from the positive 7 and each resistance is given a calibration such that it will pass the proper amount of current at the proper pressure to its respective lighting circuit, assuming that all the lamps of such circuit are switched on. The switches (Z c and 7 and the main lighting switch 13 connect the respective resistances, through suitable wiring, to the main lighting positive 12.

The regulating wire 20 is arranged as. before and is adapted to be connected to main lighting positive 12 providing a parallel path for the dynamo current passing through the resistances.

As before, brush 16 serves to short circuit the lamp resistances when the dynamo cut out but I have provided additional brushes 25 and 26 each connected to the battery 120 positive through a respective resistance 27 and 28. The purpose of these resistances 2? and 28 is to assist in maintaining proper lamp voltage at the time when the dynamo. voltage has been built up to the point where 25 it approximately equals the voltage of the battery at which time the cut-in switch closes but the dynamo volta e is ins flicient to pass the proper amount of current at the proper pressure through resistances 32, 33 1:30

and 34;. This apparatus is fully described and claimed in my co-pending application, Serial Number 163,815, filed April 23, 1917, and for the purposes of this specification it will sutlice to say that the cut-in switch, after closing, is farther attracted on a rise in voltage and lifts brush 16 placing resistances 27 and 28 in parallel with resistances 32, 33 and 3 1 thereby reducing the total resistance in an amount sufficient to permit the dynamo to deliver the proper amount of current at the proper pressure to the lighting circuits. As the dynamo voltage rises, the plunger of the cut-in switch is attracted still farther and brush 25 is lifted out of engagement with contact 17 leaving resistance 28 in parallel with resistances 32, 33 and 34:, thus increasing the total lamp resistance in proportion to the increase in dynamo voltage. When the dynamo develops a voltage suflicient to properly supply the lighting circuits through resistances 32, 33 and 34, the last brush 26 is lifted out of engagement with contact 17 and the main resistances 32, 33 and 34 function to maintain proper lamp voltage assuming all lamps are switched on in the respective circuits. Preferably coincident with the lifting of brush 26, regulating wire 20 is connected as before described.

Resistances 32, 33 and 34 are so calibrated as to take care of the big changes in the lighting circuits such as the closing or opening of any one of the switches (Z, c and f, and if any of the lamps of an individual circuit are switched on or off, and new lamps of different value substituted, or additional lamps added, the regulating wire 20 will function as before set forth to maintain substantially constant lamp voltage and to eliminate flickering.

The reducer switch mechanism G and the stop charge mechanism H are fully described and claimed in my co-pending application, Serial Number 256,380, filed October 1', 1918, and for the purpose of this specification, it will suflice to point out that the reducer mechanism is designed to automatically reduce the rate of charge by placing a resistance in parallel with the battery dependent upon the condition of the battery as reflected by the reducer switch shunt and series operating coils. The reducer 'mechanism also serves to protect the system against open circuit running. The stop charge mechanism H operates to discontinue the charge when the battery has become fully charged. Neither the reducer mechanism nor the stop charge mechanism interferes with the operation of the regulating wire, but all of the mechanism together with the slipping belt drive constitutes an effective lighting system.

In order to insure equal charge of all cells, I provide any suitable mechanism such as a resistance M adapted to be placed in parallel with 18 cells when the main lighting switch is opened, the resistance being calibrated to pass but a small amperage such as would be suflicient to take care of slight inaccuracies.

It will also be apparent from the foregoing that I have provided lamp voltage regulating means of substantially zero value when there is proper voltage on the lighting circuit, such means having negative value when the lamp voltage tends to rise and having positive value when the lamp voltage tends to fall. Thus the regulating element will meet all of the various conditions which may be encountered in train lighting and will function uniformly, notwithstand ing the conditions in the system, because the regulating element will always be in step with such conditions.

I claim:

1. In a car lighting system, the combinatlon of a dynamo, a lighting circuit, a battery to be charged, a cut-in and cut-out switch in the charging circuit, a lighting circuit resistance, a connection between the lighting circuit side of said resistance and a point in the battery intermediate its terminals, and means acting when the cut-in and cut-out switch is closed to place said connection in parallel with the lighting circuit.

2. In a lighting system, the combination of a dynamo, a lighting circuit, a battery to be charged, a cut-in and cut-out switch in the charging circuit, a connection between the battery side of the cut-in and cut-out switch, and a point in the battery interme diate its terminals, and means acting when the cut-in and cut-out switch is closed to place the circuit through said connection in parallel with the lighting circuit.

3. In a car lighting system, the combination of a dynamo, a lighting circuit, a battery to be charged, a cut-in and cut-out switch, a lighting circuit resistance adapted to be short-circuited by the cut-in and cutout switch when the latter is open, a path in the battery in parallel with the lighting circuit and connected to the battery at a point intermediate its terminals, and means operated by the cut-in and cut-out switch for closing and opening the circuit of the said path, said means opening the circuit to said path before the resistance is short-circuited.

1. In a car lighting system, the combination of a dynamo, a lighting circuit, a battery to be charged, a cut-in and cut-out switch, a resistance for the lighting circuit, a connection between the lighting circuit side of said resistance and a point in the battery intermediate its terminals, means operated by the cut-in and cut-out switch for short-circuiting the resistance when said switch is open, and means operated by the circuit through said connection in parallel with the lighting circuit.

6. In a lighting system, the combination of a constant watt dynamo, a lighting circuit, a battery to be charged, a lighting circuit resistance, a connection between the lighting circuit side of said resistance and a point in the battery intermediate its terminals, and an electro-magnetic switch for placing the circuit through said connection in parallel with the lighting circuit.

In testimony whereof, I have hereunto signed my name.

HARRY D. ROHMAN.

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