US1240898A - Electric-railway system. - Google Patents

Description

K. E. STUART. ELECTRIC RAILWAY SYSTEM. APPLICATION FILED MAXI-.1914.

1,240,898. t fi ptn 25,1917.

13 SHEETS-SHEET I.

A'ITORNEY K. E. STUART; ELECTRIC RAILWAY system. APPucAriuu mm Yum-1.

Patented Sept; 25, 1917.

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NTOI i -ATTORNEY K. E. STUART. 5150mm RAILWAY SYSTEM.

' APPLICATION man MAYLISTM Patented Sept, 25, 1917.

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ELECIRIC RAILWAY SYSTEM. APPLICATION HL'ED' my i914.

' Patented Sept, 25,1917.

13 SHEETS-SHEET '5 BY 55K K. E. STUART.

ELEGTBIC'RAILWAY SYSTEM. APPLICATION FILED MAY 1, 1314.

1 ,240,898. Patented Se t. 25, 1917.

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Patented Sept. 25, 1917.

44; nrrlio RN BY KuE! STUART. ELEQTRIC RA ILWAY SYSTEM. APPLICATION FILE MAY I M.

Patented Sept. 25,,1917.

i3 SHEETS-SHEET I l.

Hls ATTORNEY K. E. STUART.

ELECTRIC RAILWAY SYSTEM. APPLICATION FILED MAY nan.-

1,240,893; I V PatenqedSept 25, 1917.

13 SHEETS-SHEET l2.

# 2 ATTORNE;

KnivnETH n. STUART, or LONDONQENGLAND,

unaware-RAILWAY srsrnm;

Original application -fi1ed April 29, 1912, Serial No. 693,973. Divided and this 1914. Serial-No. 835,778.

To all whom it may concern:

Be it-known that I, a citizen of the United States, residing in the city of London, England, have invented new and useful Improvements in Electrlc- Railway Systems, .of, which the following is a specification.

My. invention relates to an electric rallwaysystem suitable for the despatch of mail,

preaching car or train is a station 1 11 question or system to I tions excepting that parcels, etc., in which the moving cars or trains carry nomotormen.

My invention resides in a system of control for the trains or cars-involving a block revent collision between cars or trains, an res-ides more particularly in means for automatically accelerating, braking, starting and stopping the trains or cars.

My invention resides also in a system for indicating automatically in each station the position of cars or trains on the line and for indicating whether a particular apto be stopped at the to pass it without stopping; and my invention lecting means used in connection with such a system.

My invention resides in other features hereinafter described and claimed.

For an illustration of one of the forms of my invention reference is had to the accompanying drawings, in which:

Figure 1 is a diagram of the'connections upon a car and between the carand the track and conductor rails and one type of controller, which is shown in the reversing position or position in which it makes such connections as will cause the car to start backward.

Fig. 2'is a diagram of the same connections excepting that the controller is shown in the braking position or position in which it makes such connections as will cause the car to be electro-dynamically braked. Y

Fig.3 is a diagram of the sameconnecthe controller is shown in the starting position. or position'in' which it makes such connections as will causethe carto start forward.

'Fig. 4 is a diagram of the same connections excepting that the controller is shown in the through position. or position in which it makes such connections as will cause the car to continue at a predetermined speed. 1

Specification 0: Letters Patent.

KENNETH E. STUART,

resides in sesection when they made-by the l in the through or normal position, which in Patented Sept. 25, 1917. application filed May 1,

diagram of the electrical apconnections at a terminal sta- Fig, 5 is a paratus and tion. a

Fig. 6 is a similar diagram (shown for convenience in three parts) for the first block section, supposed to adjoin the preceding sect'ion on the right. I

Fig. 7 is a similar diagram for the second block section, supposed to adjoin the preceding section on the right.

Fig. 8 is a similar""diagram for the third block section, which includes an intermediate station and is supposed to adjoin the preceding section onthe right. This figure also shows diagrammatically the electrical apparatus and connections at the said inter mediate station. I Figs. 9 and 10 are similar diagrams \for portions of the fourth and fifth block sectionsrespectively, each supposed'to adjoin the preceding section on the right. Fig. 11 is a diagram of the connections made by the contactors of the first block'section when they are in the braking position or position which causes the train to come to rest upon this section.

Fig. 12 is a diagram of the connections made by the same contactors when they are in the starting position or position to restart the train after it has been brought to rest upon this section.

Fig. 13 is a made by the same contactors when they are in the through position, or normal position, which in this case are such as to re tard the train to a speed at which it can diagram of the connections safely enter upon the curved portion of the line. Fig. 14 is a diagram of the connections made by the contactors of the second block are in the braking position. l

Figs 15 is a diagram ofthe connections made by the same contactors when, they are in the starting position.

Fig. 16 is a diagram of the connections same cont-actors when they are this case are such as to accelerate the train again to full speed and then pass it over the remainder of the section at substantially that speed. g

Figs. 17, 18 and 19 are diagrams of the connections made by the contactors of the third block section when they are in the braking, starting and through positions re-v made within the same controller when it is in the starting position.

Figs. 22, 23,24 and 25 are diagrams of the connections made within the controller for the approach section of either station when it is in thejreversing, braking, through and starting positions respectively.

Figs. 26, 27, 28 and 29 are diagrams of the connections made within the controller for the unloading section, loading' section or siding section of either station when it is in, the reversing, braking, neutral and starting positions respectively.

Figs. 30- and 31 are diagrams of the'connections made within the controller for the braking section of the intermediate station when it is in the braking and starting positions respectively.

Fig. 32 is a diagram of the connections made. within the controller for the switch points of the intermediate station when it is in the station position, or position in which the switch points are set to direct a car into the station.

Fig. 33 is a diagram of the connections made within the same controller whenr-it is in the past position or position to direct a car past the station.

Fig. 34 is a side elevation, partly in section on the line 11 of Fig. 35, of one of the contactors above. mentioned.

Fig. 35 is a plan view of the same, part being shown with the cover broken away.

Fig. 36 is an end elevation of the same, the left half being in section on the line 22 and the right half on the line 77 of Fig. 37 is a sectional end elevation of the same, on the line 8-8 of Fig. 34.

F i 38 is a horizontal section, some parts in p an, on the line 33 of'Fig. 39, ofa single ended relay.

Fig. 39 is a plan view of the same.

Fig. 40 is a section on'the line 55 *of Fig. 38.

' Fig. 41 is an end'elevation, partly in sec-v tion, on the line 66 of Fig. 38. U

Figs. 42 and- 43 are side elevations, partly in section, and plan View, respectively, of a modified form of relay.

Fig. 44 is a diagram showing the curves otretardation from full speed to rest of an empty car and a loaded car when my system of equalizing the braking cfi'ect upon the two is employed.

Retei'r ng now to Figs. 1, 2, 3

and 'l, are contact conductor rails for the motor fieldand armature respectively. ex-

' tending alongv thetrackway andinsulated.

Fig. 34.

and 4,1, I

from the ground .and from the track rails T T M is the electric motor driving the car through the gears G and G and wheels W,. S, and S are collector shoes carried by the car and bearing upon the conductor rails T and connections upon the car are from T, through the shunt field F, and'the point 19 to the frame of the car F and thence through the wheels to and through the track rails T There is also a connection from T through the differential "series field F and the brush.

B,, to the'motor armature A and thence through the brush B point 19, car frame F and wheels to the track T There are thus three connections to the motor, a. 6., one to the shunt field, one to the armature, and a returnconnection common to both field and armature. These are used to start, stop and reverse the car in the following manner:

Upon certain sections of the line, which will be clearly indicated hereinafter, the conduct-or rails T and T,, as well as both the track rails T are insulated from the similar rails of the troller not upon the car. Upon such portions of the line the car may therefore be controlled by an operator at a distance. The manner of doing this is illustrated in Figs. 1,2,3and4.

The controller used is merely an adaptation of a well-known commercial type having fingers bearing upon a common drum which in various positions makes various connections between them. In this case there are eight fingers and four positions of the drnm The fingers are numbered 11 to 18 inclusivelyand the connections established between them by the drum in each of its several positions are indicated by the lines joining them and passing to the right of them.

adjoining sections of the lineand connected to a manually operated con Referring to Fig. 3, it will be seen that there Isa connection from the positive main to the finger 12 and thence through the drum to the finger 11, which is connected to the conductor rail T,, which, it will be remembcred. has a connection through the collecton shoe S to theshunt field of the motor M on the ear. The finger 13 has'a connection through the rheostat or resistance R, with the positivemain and through the drum to the finger 15, which in turn is connected to the conductor rail T whence. the connection is through the collector shoc'S to the armature of'the motor M tl'irough series field winding F. The finger 16 is connected to the track rails T and also tln-ough the drum to the finger 17, which is connected to the negative main. As already explained, both the armature and shunt field ha ve a return connection to the track rails T5, connections as shown in Fig. 3. therefore, the motor field \Vith the F will be excited to full T respectively. The electrical 0 strength while the armature will receive cur- I rent at a reduced voltage,

which may be starting the car from field F is in. opposition but the current flow made suitable for rest, and the series to shunt field F through F is not great, due to resistance R and therefore the motor field is not greatly weakened by F As the car is intended to move at slow speed only while under the control of these controllers, it is not necessary to provide another position in which the rheostat R is cut out. Under'certain circumstances to be explained later, however,

. it may be desired tokeep the car moving uniformly at the reduced speed with which it arrives upon the portion of the line in question, and for this purpose another position of the controller is provided as shown in Fig. 4. In this position the connections are the same as before excepting that the finger 15 which supplies the motor armature is now connected through the drum to the finger 14 which receives current through a greater resistance than the finger 13.. The connections for braking the car are shown in Fig. 2. In this case the motor field F, is excited to full strength as before,

while the armature instead of being con transferred through nected to the positive main is connected through, the drum and finger 16 to the track rails T thus completing a short circuit through the armature. Any rotation of the armature will now cause it to generate an electro-motive-force which on account of the low resistance of the armature circuit will cause aheavy current to flow which in turn resists the rotation of the armature, or in other words exerts a braking effect on the This armature current is in reverse direction, and, passing through series field F.., causes the latter to act. cumulatively with the shunt field F to produce a still.

stronger fields As will be shown later, by interposing a suitable resistance in the armature circuit (not shown in Fig. 2) I regulate the braking effect so as not to damage the motor or cause the car wheels NV, to skid on the rails T The method of reversing the directions of the car isshown in Fig. 1. In this case it will be seen that the motor armature is con' nected through the drum to the finger 12, which receives the full voltage from the positive main; The return connection from the track rails T, is. however, no longer directly to the negative main but is through the drum and finger 18 to the negative main through the rheostat The field connection from the conductor rail T, has also been the drum and finger l? to the negative main direct. With these connections it will be livid is now connected in serieswith' the armature, 'hut in shunt or parallel with the rheostat H 'lhus, the current now flows and 18 and the rheostat and is now the same as vfield, making a compound field. Without ened as it, gathers speed.

seen that the shunt from the finger 15 through the conductor rail T the differential series field'F and the armature to the point 19, where it divides, part returning through the fingers 1G R to the negative main, while a part flows through the shunt field and fingers l1 and 17 to the negative main direct. As the resistance of R is very great compared with that of the remainder of the armature circuit,,the fall of potential through it at the instant of switching on the current with the motor at rest will be verynearly the full voltage of the power supply. In other words the shunt field will receive very nearly the full'voltage of the 'mains across its terminals and will be excited to a corresponding degree. It will be noticed, moreover, that the direction of the current in the shuntfield has been'reversed, that of the series the latter, the motor would now develop a torque in the reversednrection approximating its normal..startingtorque... Bymeans of the cumulative field is further strengthened and the torque developed in the reverse. direction can be made to equal or exceed the normal direction starting torque.

It will be noted thatvthe series turns are not essential to this method of reversing, but

series starting turns the are useful. .They are likewise'useful in the operation of braking, since in this case the current 111 the armature is reversed and the series turns are cumulative with the shunt turns, as above described. It may also be mentioned that the diflerential series turns improve the constant speed characteristic of the m0tor'in normal ahead running and if properly proportioned are therefore an advantage from every point of view. As the motor gathers speed when so reversed the current and consequently the fall of poten' tial through the rheostat R, will diminish. This will weaken the shunt field exactly as the field of a series wound motoris weak- A shuntmotor reversed in this way therefore develops series motor characteristics. But as I use this method of reversing only for side tracking and switching within the stations where the car is under control of the operator, this feature is not objectionable. This method of reversing avoids the use ofan extra contact conductor rail, which would otherwise be necessary to provide a separate returncon'nection from the shunt field for reversing the current through it.

lfhe manual control of the car above described, a". 6., by means of controllers, is used only in or near the stations. At other points the movement of the car is independent of the operators, but subject to the automatic control of a block system.

Referring to Figs. 5,- 6, 7, 8, 9 and 10, T

' conductor railand T ductor rails into the sections above refer n red to.

At the approach to each station it will obviously be necessary to provide means for bringing the car to rest. In Fig. 5 the 1nethod of accomplishing this at a terminal is shown. This is accomplished by disconnecting the armature conductor rail T from the source of current S0 (connected to positive main pm and to negative main mn) and connecting it to the track rail T through a resistance while the field winding F is, separately excited at full strength, as already described. The minimum safe resistance in the armature circuit 'is determined by the speed of the car, and as the'car is retarded the resistance can therefore be out out step by step. In Fig. 5, the sections of the armature conductor rail I -I I I,, I,I

I I are each connected to the track rail T through successively smaller portions of the resistance or rheostat R The section 'I -I is connected to the positive mainpm,

for reasons that will be explained later. The sections of'the armature contact conductor rail T such as I I etc., which are for braking normally connected to the track rails T, I call retarding sections. The section I,I vI call an equalizer section. The whole series collectively I call a'braking section. v

The field conductor rail T throughout the retarding sections, as Well as elsewhere, is likewise divided into sections (as at I I I etc, Fig. 5.) which haveto do with the system of indicating in the stations the position of. the cars in transit and also with the block system, both of which will be described later. Each section of the field conductor rail receives currentthrough a. series solenoid in the relays R R etc. These series solenoids are of negligible resistance so that the field conductor rail may, except in the ease of" sections that are under the control of controllers, be considered to be in permanent connection with the positive main pm, causing the motor field F to be excited as stated.

The operation of the retarding sections willibe better understood by reference to Fig. 44. In this figure, the full line 1 is the curve of retardation of a loaded car from 30 miles per hour to rest, ordinates being proportional to speed and abscissae to distances. In the case illustrated, on the first retarding section, 2'. 0., I,I.,, the speed is retarded from 30 to 15 miles per hour. Upon the equalizing section I I the motor on the car receives current from the source of power tending to drive it, but the resistance interposed between it and said source is so.

motor armature whose loaded car,

calculated that the torque developed by the motor is 'insufficient to overcome the resist ance of the car to forward motion, which therefore continues to be retarded, though at a reduced rate. The car is retarded on the equalizing section from 15 to 10 miles per hour. On the remaining retarding sections, the speed is reduced from 10 to 5 miles per hour, from 5 to 2% miles per hour and from 2;; miles per hour to rest respectively.

In Fig. 44 the dotted line e 0 is the curve of retardation of an empty car arriving at the same speed as the loaded car.

The function of the equalizing section is as follows:

The braking effect of a short-circuited field is separately. excited at constant strength is, with a given resistance in the armature, circuit, propor-' tional to the speed. In other words, for a given speed it is the same for both the loaded and empty cars. But at a given speed the empty car possesses less energy than the loaded car, consequently it will be retarded more rapidly. In the case illustrated in Fig. 44 the empty car reaches the equalizing section with a speed of 13% milesper hour, as compared with 15 for the loaded car. At this reduced speed, how ever, the empty car receives agreater current from the source of power than did the and gains in speed relatively to it. It leaves the equalizing section with-a speed of 11 miles per hour as compared with 10 for the. loaded car. From this point it begins again to be retarded more rapidly than the loaded car and finally comes to rest at the same spot (20, Fig. 44).

With any system of braking depending upon friction there is not only a great Varia tion in the distance required to bring a train to rest on account of variation in the coefficient of friction, but there is also a great difference between empty and loaded cars (100% or more); With dynamo-electric braking this variation is reduced to about l2-;;%. By means of the equalizing section, however, it can be further reduced to a negligible quantity.

It will be observed that on each of the retarding sections the speed is reduced in' the same ratio (being halved in this case, except that on last section the speed is reduced-to zero). The object of this is as follows? The maximum allowable electro-dynamic braking effect, expressed as a torque in foot pounds, at the beginning of each section is limited either by the adhesion of the driving 'wheels or by the capacity of the motor, and

- at its end 'a braking effect which bears preceding section and section, etc.

tion is secured by so proportioning the-- lengths of the sections and their associated armature circuit resistances that the braking effects at the initial ends of the sections are substantially equal, and the' braking effects at the terminations of the sections are likewise substantially equal, it being remembered that the speed nevertheless is always decreasing; and furthermore, the ratio of the braking effect at the beginning of each section to the braking effect at the termination of each section is substantially the same r'or all sections with the exception of the last, in'which case the same maximum braking eifect is produced at the initial end of the last section, but the braking effect is reduced to zero as the car comes to rest. For instance, at the point at which it is desired that the motor braking should begin the resistance to be insertedin the armature circuit in order to give the maximum allowable braking torque is determined. With this factor known the rate of negative accelera tion or braking is determined. From this thelength of the section necessary to insure the desired ratio to the braking effect at its initial end is determined. The next step is the determination of the resistance to be 1nserted in the armature circuit for the next succeeding braking section.

This, however, is a function of the speedat the end of the is therefore determined in the same way as the corresponding resistance for the first section. This process is followed out for the desired number of sections, and we have the following relation:

in which T is the braking elfect or at the initial end of the first section, T the effectat the end of the first section. T, the effect at the beginning of the second section, and T, the effect at the end of the second It being remembered, however, that the braking effort is proportional to the speed and. that the speed at the end of the first section is substantially equal to the speed at the beginning of thesecond section,

torque and so on, we may write:

are the speeds at the beginning of the successive retarding sections. If this law is followed it will be found that the successive retarding sections become shorter and shorter as in Fig. 44.

The retarding sections are normally at the entrance tothe station, their function being to prevent thecars from entering the station eircept at the volition of the operator. When the "cars have come to rest or been retarded to a safe speerh'therefore, it is the positive main pm.

call the approach section is under the control of the controller necessary that the operator should be able to cause them to enter the station.

This is accomplished by connecting the retarding sections to a controller in the station by means of which the operator may-by a movement of a lever disconnect them simultaneously from the track rail and connect them to the source of power.

In Fig. 5 this controller isshown at O It will be observed that the retarding section L L' is permanently connected throu h. the rheostat R to the track rail and the equalizing section 1 l, is permanently-connected through the rheostat R, to The operator thus has no control over the car until it'has been retarded to a safe speed. The remaining retarding sections are,however, the fingers 22, 23 and 24 of the controller C,, and in the position shown in Fig. 5, these fingers are connected through the drum tothe fingers 25, 26 and 27. Thence 25 is connected directly to the and 27 are connected to the track rail through 5 the rheostat R as previously stated. The connections made by the drum of this controller in this (the braking) position are shown again for clearness in Fig. 20, side by side with the connections'made by it in the alternative or starting position (Fig. 21). From this figure it will be seen that in the starting position the fingers 22, 23 and 24 are connected to the finger 2i, and from Fig. 5 it will be seen that the finger 21 is connected through the rheostat R, to the positive main. In this case there are no reversing or through positions of the controller. The functions of the finger 28 and the solenoid 29 will be explained later.

The braking section ends at I and at this point another section of the track, which I section, begins. This 0,, which is similar to the controller that has already been descr bed in connection with Figs. 1, 2, 3 and 4. It will be remembered thatit has four positions, viz., revet-sing, braking, starting and through. For clcarness. the drum connections in each of these positions are shown again in Figs. 22, 23, 2t and 25. The object of the through position may now be understood. It is that this approach section I,-I, may serve as an equalizer section for trains that have been admitted from the braking section, the operation being the same as that of the equalizing section already described. By this means ,an empty section at a speed less than desired speed because it has been to greater degree braked on the preceding braking section, will be ad celerated because the current required for the acceleration is relatively smaller and occasions smaller drop of potential in the resistance R with thev result that there is connected to track rail and 26 car. arriving on this tively higher voltage than in the case of a loaded car arriving under similar conditions.

The approach section in general enters the station and is used for shunting or switching the cars, hence the reversing, braking and starting positions.

From the approach section the car normally passes overaswitch point orsystem of switch points which may direct it on to an unloading section or ,upon a siding, at the will of the operator. In Fig. 5, the unloading section is from I, to I, and a sidin is shown from L to I I, to I, is a loading section.

These three sections in the order last" named are under the control of the controllers C C, and C, respectively. The controllers are all similar to each other, but differ from the controller C in that they have no through position, the place of which is taken by a neutral position, in which all connections to the section are interrupted.

The drum connections for the several posi tions of these controllers are shown in Figs. 26, 27, 28 and 29. They are similar to those of C except that instead of the two fingers 13 and 14 connected through different resistances to. the positive main 12m, there is but one, indicated at 33.

It will be noticed that the several controllersare not associated with the same rheostatsR- R,, R, and R either for receiving current through them from the source, or for braking purposes. The object in this is to avoid the use of the same rheostats for two sections upon which it maybe desired to move trains at the same time, for

if two trains were to take current simultaneously through the same rheostat the current and consequently the fall of potential same as when only one was taking current and neither train could develop the required starting torque.

It will be noted thatthe field conductor rail T and the track rails T, of each of these sections under control of controllers having a reversing position are insulated from the adjoining sections as well as the armature conductor rail (as atl and I, F ig. 5). This is necessary, as in reversing, the field conductor rail completely changes in its polaritv, while a considerable difference of potential is created between the section of the track rail and adjoining sections owing to its being connected to the negatire main am. through a. resistance as previouslyexplained.

It is to be understood that the arrangev ment oi an actual station may be. more or less of a modification of the arrangementdescribed while conformingto it in that there will be one or more sections completely insulated from adjoining sections and each unthrough the rheostat would not be the der the control. of a separate controller, whereby cars can be moved on one section without disturbing those on another.

W hen a car passes over the insulators I, or I it leaves the control of the operator at the station and enters upon a series of sectic-n5 9 11 l27 I12 I137. 1a 14 and I14 1 which I call accelerating sections. The accelerating sections are normally connected to the positive main through successively less portions of the rheostat R The field conductor rail is likewise sub-divided, but as a1- rcady explained, all of its sections, except in the case of sections that are under the 'control of controllers, are permanently connected to the positive main pm.

As the car advances over the accelerating sections, therefore, theresistance that was interposed in the armature circuit at start ing is cut out step by step until at I the armature is receiving full voltage, the field F, being meanwhile separately excited to full strength, causing the car to be accelerated to full speed.

The section I,I -I is connected to the positive main through the contactor K,, which has to do with the block system to be explained later.' With this exception, the connections of the accelerating sections of the terminal station shown in .Fig. 5, with the positive main are permanent. i

tive-force), s the speed at any instant, T

the motor torque and R the total resistance of the armature circuit, then with the field separately excited to full strength:

'1 const.

The maximum positive accelerating torque,generally expressed in foot pounds, at the beginning of each section is limited either by the adhesion of the driving wheels or by the capacity of the motor, and is con sequently the same for all of the sections. To procure suitable mean accelerating effect with a given number of sections, I prefer to make the mean accelerating effect upon each "of them the same. This condition is secured by so proportioning the lengths of the sections and their associated armature" circuit resistances that the accelerating effects at the initial ends of the sections are substantially equal and the accelerating effects at the terminations of the sections are sen like-wise substantially equal; and further- 'more, the ratio:ofaccelerating eilect at the beginning of each section tothe accelerab. ing efiect at the termination of each section is substantially the same for all sections with the exception of=the last, in which case 'the same maximum accelerating effect is produced at the initial end of the last section, but the accelerating toaero as'the carnttains full speed. For instance; at the starting point of the car or train the resistance to armature circuit in order to givethe maxi mum allowable accelerating torque is determined. With this factor known the ra-te of acceleration is determined. Fro-mthis the speed an the desired ratio to .at its initial end is determined. T e next beginning of the second torqueat theend of=the second section, etc. 1 a Suhstituting -forveach torque value in the control-of the controllers C- length of the section necessary to'insure at its end an accelerating effect. which bears the aecelera-tin effect.

step is the determinationzof the resistance to be inserted inth'e" however, is a function of the speed at the end of the preceding-section and .is there fore detemnined in the same way as the corresponding-resistance for the first section. This process is followedoutfor the desired number of sections, and we have the following relation:

. E T; in which T isthe accelerating torque at the start, T the;torque at'the endof the first accelerating section, T the torque at the section;: and T, the

etc.,

last equation its equivalentfas given. by a precedin equation as a relationbetween resistance,- we have the following in which 8 s etci, are the speeds at the beginning of'thewsuccessive accelerating sections. This equation therefore expresses a condition of the onost efiective acceleration witha given ammber ofsections.

At the intermediate station, proach, unloadingiand-siding sections (I 31 and sa 33) 1' 11nd or n and C10 are found, but otherwise this rcspectivel station diers matter-i lly fromthe terminal station just 'described-in'ways that can best be explained in--connection with the block system.

-' It has already been stated that the held conductor 'railis dividedf'into sections, each of which receives current through a series carried along the line from one end to the effect is reduced bec'inserted in the I armature circuit for the next succeeding acceleratmg section. This,

type justdescribed.

( isp 212* For this pure other and is everywhere indicatedby the sign (Figs. 5 10 inclusive).

The construction of these relays will be understood by reference to Figs. 38-43 inclusive.

. The relay, as R is horizontal.

C is an iron core passingthrough the solenoids S iatrid S of which the former is the low resistanceseries solenoid through which the sectionsoi' the field conductor rail are supplied. When S is energized it drawsthe core C in thedirection of the arrow. in Fig. 38. 7 W, are contacts between which passes the sleeve S which is mounted upon the brassrod S, forming a continuation of the core C The sleeve S, is metallic and in-one pos'tion makes contact between the contacts W At the end which comes between these two contacts-when the core is to the left, however, the 'sleey. S is surfaced with an insulating material-fill). and in this position the connection between the two contacts is interrupted. 'The' sleeve S, is made free. to slide upon the rod' S, in order that it may lag back during the first half of themotion of the core C 1,, in the opposite direction to the arrow in Fig. 38 and com- "press the spring S which during the remainder 'of;lthe grhovement reexpands and quickens thelbrelalting of the circuit. R 3 mm! R Fig. 5, are relays of the Being represented dia-' grammatically, the contacts are shown between the solenoids instead of at one end, but this does not changethe principle of operation. I hen the solenoid nearest the contacts' is energized, the connection between the contacts must be considered to be established. Relays of this type will bereferred to hereinafter as single-ended relays. R R R etc., Fig. 6, are "relays exactly similar to those .ju'stdescribed except that the contactmechanism W N at the one end is duplicated at the other end where the stationary contacts are W W Relays of this type will, referred to as doubleended relays, and'the contacts 1W as interrupting contacts. Figs. 42 and 43 illustrate a modified form of relayg' as li inarranged with its axis tended to be operated withits axis vertical so that the weight of the core Qi', and lead weight. 101' in fallingfrom posit on shownbreak the contact, thus shunt solenoid S u Relays of this type will be called gravity relays. R Fig 5, and R Fig. 8 are of this type. These two rej lays are likewise shown diagrammatically and notwithstanding 'be understood that when the solenoid s energized, connection is established between the upper contacts; and in thecase of relay R and those like it, the lower contacts are conncoted when the solenoid is deenergized. 1 Referring again to, Fig, 5 and taking the their position must dispensihg with the

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