US979556A - Block-signal system. - Google Patents

Description

G. S. PFLASTERER.'

BLOCK SIGNAL SYSTEM.

APPLICATION FILED 113.23, 1909.

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G. S. PFLASTBRER.

BLOCK SIGNAL SYSTEM. APPLIUATION yHLM) Planas, 1909.

WINESSES INI/EN TOI? 9,556, Patented Dec.27, 1910.

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GEORGE S. PELASTERER, OF NASHVILLE, TENNESSEE.

BLOCK-SIGNAL SYSTEM.

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Specification of Letters Patent.

Patented Dec. 27, 19H).

Application led February 23, 1909. Serial No. 479,612.

To all whom i may concern:

Be it known that I, GEORGE S. PrLAsrnnnn, a citizen of the United States of America, residing in Nashville, in the county of Davidson and State of Tennessee, have invented a certain new and uset'ul Improvement in Block-Signal Systems, of which the following is a true and exact description, reference being' had to the accompanying drawings, which form a part thereof.

rIhe present invention relates to railway signals and particularly to block signal systems for single track railways, has tor its main object the provision ot an improved. block signal system for single track railways which can be cheaply installed and is inexpensive to maintain and is reliable, effective, and relatively simple in construction and operation.

The system disclosed herein is primarily intended as an improvement on, and is of the same general type as, the system disclosed and claimed in my copending application Serial No. 4315492, tiled June 9th, 1908.

The present application, like the prior application, discloses a system in which an absolute clear signal indication can be given a train about to enter a block only when the block is entirely tree from trains, while a permissive signal indication may be given to admit a train to the block, following a previously admitted train still in the block, when the latter has proceeded a predetermined distance from the end of the block at which it entered.

In the signal apparatus shown in detail in said prior application, the signals are manually actuated and are controlled through electric circuit connections including slot windings and track relays. In one loi'm of the system disclosed herein, manually actuated slot controlled signals are employed, while in another form the signal is directly actuated through an electrical operating mechanism, but the instrumentalities employed in both forms of the system disclosed in the present application for controlling tlie energization ot the slots, or of the electrical signal actuating mechanism, are like those' described and claimed in the prior application.

The system disclosed herein, like the system ot the former application, resembles the well known telegraph block signal system and is particularly adapted to facilitate the conversion into the new system of existing telephone or telegraph block systems.

In my prior application, the means shown for preventing the setting of a signal in a full clear position when a permissive but not a full clear indication is proper, comprises means for opening the signal controlled slot circuit upon a movement of the signal actuating lever beyond the intermediate or cautionary position. In the form ot system disclosed herein, in which slot controlled manually actuated signals are employed, however, I do away with the means for breaking the slot circuit upon a movement oi the signal actuating lever beyond the intermediate position and provide in lieu thereof a mechanical latch which normally prevents the movement ot' the signal lever beyond the intermediate position, and I provide also an electric locking device, normally lockingthe latch in the latching position, and means for automatically releasing the device to permit the latch to be unlatched when a full clear signal indication is proper.

In both forms of the system disclosed herein, I provide means for maintainingrthe energization of the signal controlling winding when it has once been initially energized until the rea-r end of a train entering the block at the end where the signal controlled by the winding is located, has passed through the first section of the block, which is preferably a short section. The arrangements are such, however', that in case a following train enters the block section vacated by the entering train as the latter passes into the block the signal will be at once restored to danger, so that the signal will be set in front of the following train, no matter how closely its front end may follow the rear end of the preceding train to the signal point.

In the claims annexed to and forming a part of this specification, I have aimed to point out with particularity the features ot' novelty characterizing the present invention, but for a better understanding ot' the invention, reference should be had to the accompanying descriptive vmatter and drawings, in which I have described and illustrated diagrammatically, apparatus and circuit arrangements by which the invention may be carried out.

Of the drawings: Figure l is a diagrammatic view illustrating a portion of a signal block with that form of my system in which manually actuated slot controlled signals are employed, the view showing the instruments located at one end of the block and certain of the intermediate connections; Fig. Q is a diagrammatic representation of the signal proper employed in Fig. l and its actuating mechanism; Fig. 3 is a plan view partly in section of the signal actuating lever and locking mechanism therefor of Figs. l and 2; Fig. 4C is a view generally similar to Fig. l, illustrating a modification in which the signals are electrically actuated; and Fig. 5 is a section on the line 5 5 of Fig. 2.

In the drawings, and referring first to the form of system shown in Figs. l, 2 and 3, Y represents the track rails divided into sections .by insulated joints Z, Z2, Z2, Z4, etc. The signal S for the one signal station A shown is located adjacent the insulated joints Z2 and controls the entrance of trains into the block beginning at the joints Z2 and running to the left. For each block section shown, there is a source of current as a battery X11, X12, X13, X14, and for each of the sections shown there is a corresponding track relay M, M2, M2 and M4, and in addition, there is an eXtra track relay M for the section adjacent the right hand end of the block to which signal S pertains.

The signal S is manually actuated, but is controlled by an electric slot. Tn the arrangement shown diagrammatically in Fig. 2, the actuating device is a lever Ss which may be moved from the normal danger position shown into an intermediate position or cautionary position, or into a third or full clear position under certain conditions. The lever Ss is connected by a rod S7 to one arm of a bell-crank lever SG, the other arm of which is connected by a rod S5 to the slot links S2, the latter being connected in turn to the rod S2 by which the signal proper is operated. The slot links S2 are connected to the armature S2, which renders the slot link connection between the rods S2 and S5 operative when the slot winding R is energized.

The rod S2 carries collars S2, S10 and S1l which control switches X, X2 and X2. Switches X and X2 are normally open, but switch X is closed by an upward movement of rod S2 somewhat less than that required to give a permissive signal indication, and switch X2 is closed by an upward movement of the rod slightly greater tha that required for a permissive indication. Switches X and X2 after being closed remain closed until the rodS2 moves below the closing position. Switch X3 is normally closed, but is opened when the rod S2 moves above the normal position. The e'nergization of the slot winding R is dependentupon the condition of the track relays of the block and the closure of certain switches under symbol S15 the manual control of the signal operators at the two ends of the block, and T will remark that the instruments and devices at station A may be, and under ordinary conditions are, exactly duplicated at the end of the block remote from that at which station A is located.

The quadrant S12, in which the lever SS is mounted, is provided with a housing for a mechanical latch or sliding bolt T, which is normally spring held in the position in which it bars the movement of the lever Ss beyond the cautionary or permissive signal setting position. The bolt T is formed with a hole T2 through which a locking pin U2, carried by the armature U of magnet U, projects when the magnet is denergized. `When the bolt T is freed from the locking pin U2, it may be moved out of the path of lever SS by engaging the knob T2.

It will be observed that the bolt or latch T is separate from the usual means conventionally shown and indicated .by the for holding the signal lever S2 in any one of the three positions into which it may be adjusted. The bolt or latch releasing knob T3 is out of proximity to the lever proper, and the operator cannot release this latch and simultaneously shift the lever with one hand in a practically automatic manner as he can do with a switch actuating mechanism provided with such a holding device as is indicated by S15. y

At each station there are located two indicator magnets I and i. One T is energized when the circuit connections are such that a full clear signal indication may be had, and the other, 71, when a permissive indication may be had.

The armature I of magnet l .is connected by an arm T2 and link T2 to a target or indicator It, which, when magnet l is energized, is thrown into f'iew through the opening B in a cover B which normally conceals the target. This target may be marked in any suitable manner to indicate its character, as by the words Block clear. Similarly, armaturez' controls a target i* through link 172 and arm 2'2. Target i* may be marked Train in block. When neither of magnets I nor z" is energized, a legend Instrument free is visible through opening VB. The magnets I and z" and connected parts, and the stick magnet G, emergency circuit breaker L and three way switch J, hereinafter described may be all inclosed in a single compact case, of which the cover plate B forms one wall. It will be understood, of course, that the key F hereinafter described and the handles of switch J and circuitbreaker L should project through the wall of this case.

From the station A, a conductor l runs to the other end of the block. This conductor is unbroken between the block ends and is the common or return line of the system. F rom the station A in the arrangement shown, two signal lines 12 and 2O run to some intermediate portion of the block, at which is located what l term an interlocking relay E. Similar lines 12 and 2O run between the relay E and the remote station.

As the particular construction of the inter locking relay E forms no part of the nresent invention and is fully described and illustrated in my said prior application, I will not describe it herein further than to say that when the block is entirely tree from trains, it serves to connect the. two lines 12, and when the block contains trains, it serves to connect the line 20 fromuthe station at which the trains have entered the block with the line 12 from the station at which the trains are to leave the block.

then it is desired to actuate the signal at one end of the block, the operator at the remote end of the block closes certain circuit connections which connect a source of current between the line 12 and the line 1 at his station. The operator at station A, for instance, supplies current for the clearance of the signal at the other end of the block by depressing a hand key F which throws up the armature Gr' of a magnet G, which I call a stick magnet, and thereby connects the adjacent end of the line 1 to the line 2. The line 2 runs to one terminal ot' the stick magnet G. The other terminal of the magnet G is connected by a line 3 and conductor 4 to one terminal of a source ot' current such as the battery Q. The other terminal of the source of current Q is connected by conductors and 6 and switch X3 to the switch point 9 of a three way switch J. The three-way switch J, in the form shown, comprises switch contacts 7, 8, 9, 10 and 11, and a pair of switch blades connected by an operating handle in the usual manner with one switch blade permanently electrically connected to the contact 8, and the oth er blade permanently electrically connected to the contact 10. Then the switch blades are thrown to the right of the position shown, the right hand switch blade connects the contacts 1() and 11, and the contacts 7, 8 and 9 are disconnected. When the switch blades are thrown to the left of the nosition shown in the drawings, contacts 7 and 8 are connected by the left switch blade, and the contacts 9, 10 and 11 are disconnected from each other. When the Vthree-way switch J is in the intermediate lines 1 and 2 thus causes current to be sent from. the source Q. at station A through acircuit, including the common line 1 and the line 12 to the interlocking relay, and trom there either the other line 2, or the line 2() leading away from the interlocking relay. S0 long as this circuit is closed, magnet G retains armature G and when broken, the latter falls. Preferably, l arrange an indi-l cating device to show when armature Gr falls. ln the form shown, the indicator is a bell G2 engaged when armature G drops by a striker carried by the armature. The striking ot' this bell indicates that the circuit of magnet G is broken and this means normally that a train has entered the block at the other end. It, as in case of emergencies, an operator, after having moved key F to permita signal to be cleared at the other end of the line, wishes to prevent such clearance, he can do so by opening the circuit breaker L. Similarly, when a signal is to be cleared at station A and the operator at the remote station performs his part, current is supplied Ato the station A. through the circuit including line 1, line 12 between the remote station and relay E, and either line 12 or line 2O between relay E and station A. 1Whenl current is supplied to station A by lines l and 12, the signal S may be fully cleared, and when supplied by lines 1 and 20, the signal may be setin the intermediate position only.

I will first describe the connections and mode of operation by which the signal is set in the full clear position. As a a prerequisite to giving a full clear signal indication. at station A, the operator there must throw the three-way switch J to the lett, thereby connecting the switch contacts 7 and 8. rThe absolute signal clearing conductor 12 is connected to the switch contact 8 and a conductor 13 runs from the switch contact 7 to one termin al oi the switch indicator magnet l. The other terminal et the switch indicator magnet 1 is connected to one end of a conductor 111, the other' end Aot which is connected through an armature ot' track relay M2, when the latter is energized, to a conductor 15 which is connected to the common conductor 1 through the armature G ot' the stick magnet G when the latter is denergized. lith the circuit connections described when the'three-way switch at station A is in the proper position and the operator at the remote station has connected a source of current between hisl conductor 12 and the common conductor 1, and the two conductors 12 are connected by the interlocking relay E, a flow oi current is set up which energizes the magnet I and threw-'s the target l* in front of the olriening B of the shield B. Then the indicator magnet l is energized, its armature l closes connection between the conductors 19 and 16. Conductor 19 is connected to one side of the battery Q at station A by conductors 3 and 1, and the conductor 16 forms part of a circuit running to the other side of the battery Q, and including, besides conductor 16, the conductor 17, slot winding R and conductor By these means the slot winding R is energized from the battery Q. This enables the signal to be moved out of the normal danger position by the signal actuating lever SS. Then the armature I is attracted by the energization of magnet T, it also connects conductors 19 and 24, and this causes the energization of the lock magnet U through a circuit including the battery Q, portions of conductors 5 and 6, conductor 25 .including winding of magnet U, conductor 211, armature I of indicator magnet I, conductor 19 and conductors 3 and 4 to battery Q. Vhen lock magnet U is energized, the armature U is attracted and the locking pin U2 is moved out of the hole in the mechanical locking plunger or latch T. When the latch T is thus freed, the signal lever S8 may be moved into the position in which' the signal gives the full clear indication. As the signal is moved beyond the intermediate position into the full clear position, the collar S10 on rod S2 engages and closes switch X2 so that the subsequent denergization of magnet T will not of itself cause the breaking of the Vcircuit for energizing lock magnet U.

The line 20 is connected at station A to the switch Contact 11 of the three-way switch J, and when a full clear signal indication is improper and the operator at station A desires to set his signal S5 in the inten mediate position, he must throw the switch J to the right so that it connects switch points 10 and 11. From switch point 10, a line 21 leads to the armature U of the locking magnet U. In th-e normal position of the parts shown in Fig. 1, the pin U2 carried by the armature U passes through the hole T2 in bolt T and engages a contact to which is connected conductor 22. The conductor 22 leads to one terminal of magnet i. The other terminal of the magnet c" is connected to one end of the line 1&1. The other end of line 111-, which, as has been pointed out, is connected to conductor 15 by one armature of track relay M2 when the latter is energized, while conductor 15 is connected to return line 1 through armature G of the stick magnet G when the latter is denergized.

The switch connections described result in energizing t-he indicator magnet z" and the energization of the latter moves the target t into view through the opening B in the cover B exposing the indication Train in Block. The energization of magnet i lifts itsy armature a' and this connects conductor 23 with the conductor 18 and thereby closes an energizing circuit through the slot magnet R, the circuit including the battery Q, conductor 5, conductor 17, conductor 1S, armature 2', conductor 23 and conductor 4. The energization of the slot R permits the actuation of the signal S by the signal lever SS; but in this case the lever S8 is prevented from being moved beyond the intermediate position by the latch T which is locked in the latching position by the pin U2. It is to be observed that the slot circuit controlled by the indicator magnet z" cannot be closed unless the latch T is locked in the path of the lever SS, since the energizing circuit of magnet z' is closed only when the armature U and pin U2 are in the locking position and thereby serve to connect conductors 21 and 22, and this can only occur when the latch T is in the position in which the pin U2 passes through the hole T2 in the latch T.

It will be observed that the signal at station A can be moved out of the normal danger position only when the block section between oints Z2 and Z3 is free from trains. In both cases the circuit for energizing the indicator magnets I yand z" includes conductors lil and 15, which are electrically connected together by an armature of track relay M2 when and only when track relay M2 is energized. This is as it should be since the signal should never be cleared to admit the train into the block until after a preced ing train has moved beyond the short track sect-ion between joints Z2 and Z3.

It is desirable in many cases to maintain the clearance of the signal after it has once been cleared, however, until the rear end of a train admit-ted to the block by the signal has passed by the signal. For instance, in the case of long freight trains, such provision makes it possible for the train men at the rear of the train to learn denitely in most cases that the engineer has not passed the signal without having a right to do so.

Tn the present case, T have disclosed means for maintaining the energization of the slot winding until the rear end of the train admitted by the signal has passed into the block and beyond the first section thereof. These means comprise a shunt about the indicator magnet controlling portions of the slot winding energizing circuit. This shunt includes a conductor 26 connected at one end to the conductor 17, and including the switch X and connected at the other end to conductors 27 and 2S. The conductor 27 is connected to the conductor 29 by the lower armature of track relay M2 when the latter is de'energized and the conductor 29 is connected to a conductor 30 by the armature of track relay M when the latter is energized. Conductor 30 is connected by conductor 31 to conductor 4. The conductor 2S is connected to the armature of track relay M and the latter, when the armature is denergized,

is connected to the conductor 4 by conduc- 1 tor 81.

The switch X is controlled by the collar S9 on the signal actuating rod S2 and is open when the signal is in the danger position and is closed when the signal. is either in the cautionary or clear position. The track relays M and M are de'e'nergized when a train occupies any portion of the block section between joints Z and Z2, and relay M2 is deenergized when a train occupies any portion of block section between joints Z2, and Z2. Villien a train passes into the block section between joints Z2 and Z3 from the section between joints Z and Z2 and magnet M2 is deenergizedA- the main slot circuit is broken because of the de'energization of magnet I', or f, as the case may be. The switch X being closed, however, the denergization of M2 does not affect the auxiliary slot circuit between conductors 17 and ft. This circuit includes conductors 26v and 28, armature of magnet M', which, of course, is denergized at this time, and line 3l. Nor is the auxiliary slot circuit broken when the rear end of the train passes by joints Z2, for magnet M is arranged to have a smaller time constant than magnet M. In consequence, magnet M picks up its armature before magnet M does. As a result of this, conductor 26 is connected to line 4- by conductor 27, armature of magnet M2, conductor 29, armature of magnet M, and conductors 30 and 31 before the connection between conductors 28 and 3l is broken by the picking up of the armature of magnet M. Normally, therefore, the signal S having been cleared to permit a train to pass joint Z2 remains cleared until the train passes Z3. After the train has passed joints Z2, the energization of magnet M2 breaks the auxiliary slot circuit and momentarily at least deiinergizes the slot winding and the signal returns to danger. Should a following train enter the section between joints Z and Z2 before the preceding train has passedV beyond Z3 the auxiliary circuit is broken, for the denergization of M breaks the connection between conductors 29 and 30 and this break occurs before lines 28 and 31 are connected by the armature of magnet M.

iVhile the arrangement described normally permits the signal indication which admits a train to the block to be maintained until the rear end passes through the first section of the block, it eectually prevents the maintenance of the signal indication after a following train enters the preceding block section.

In the form of the invention shown in Fig. a where the signal is not manually actuated but is electrically operated, the devices, L, F, G, J, Q., l, z', I, I2, 2, l2, 2, It and at each signal station may be substantially the same and be controlled in the same general way as those shown in Fig. l,

though certain of the circuit connections are changed, and of course there is no signal actuating lever or electrically controlled mechanical latch.

In the arrangement shown in Fig. t, the signal S is actuated by an electrical mechanism M, which may be similar to any of the well known electrical signal actuating mechanisms now in use for operating a three position signal. Q is the batter i for supplying current to the mechanism M, and V is a polarized magnet provided with two armatures V and V2. When magnet V is energized by a current flow in either direction of proper intensity, the armature V is attracted and connects a conductor a0 running from one terminal of M to the conductor 43 running from one terminal of the battery Q1. The other side of the battery Q1 is connected by a line 42 to another terminal of the mechanism M. The third terminal of the mechanism M is connected by a conductor 4:1 and armature V2 to the conductor 40 when the armature V2 is in its normal position, but this connection is broken when the armature V2 is attracted by polarized magnet V. The armature V2 is att 'acted by the magnet U only when the current flow through the magnet is in one certain direction, and is not affected by a current flow through the magnet in the opposite direction. Vith the arrangement shown, the mechanism M moves the signal S from the horizontal danger position, shown in full lines, into the dotted line vertical positionthe full clear position,-when the current flow through magnet V is such that the armature V1 is attracted While the armature V2 is not attracted. When both armature V1 and V2 are attracted, the mechanism M sets the signal inthe intermediate dotted line, or cautionary position.

The initial energization of the armature V is controlled bythe magnets l and z". The magnet I is energized as before described when a full clear signal indication is proper, and the armature z" is energized when a permissive signal indication is proper. The energization of these magnets in Fig. -f is controlled substantially in the manner and by the means hereinbefore vdescribed in connection with F ig. l. Conductors 2l and 22 and connecting means of Fig. l are replaced in Fig, a by a single conductor 2l however, |"lhe armature l is connected by conductor to one side of the magnet V and including resistance It for a purpose hereinafter described. Similarly, a conductor 34: connects the other side of the magnet V with the armature z'. Each of the armatures, I and z', when in its retracted position is connected by a conductor, 35 or 36, respectively, and by a conductor 37 to the conductor a, and by the latter to the positive side of the battery Q.. The lines 16 and 18 are connected by a conductor 17 and conductor 5 to the negative side ot' the battery Q. lVhen magnet l is energized, current flows trom the positive side ot the battery Q through conductors el, 37, and 36, armature lz', conductor 34, polarized magnet V, conductor 33, armature 1, conductors 1G, 1T and 5, back to the negative side ot' the battery Q. This flow ot current causes armature V to be picked up, but not armature V2. This, as before explained sets the signal in the full clear position. lVhen magnet z' is energized, (magnet 1 then being deenergized, ot' course) a current tlow through the polarized magnet V from the battery Q is set up in a direction opposite to that before described through the following circuit; conductors et, 3T and armature l, conductor 33, magnet V, conductor 311, armature 2', conductors 1S, 1T and 5, back to the negative side of the battery Q. The energization of magnet V by a tlow ot current through the circuit just described, i'esults in attracting both armatures V and V2 and in setting the signal in the intermediate position.

To obtain the same rear end control of the signal S as is obtained in the arrangement shown in Fig. 1 by the use of the auX- iliary slot circuit, l have provided a similar arrangement. in the form olf the system shown in Fig. l for maintaining` a shunt energizing circuitfor the polarized magnet V, about the portion ot the initial energizing circuit therefor, containing' armatures 1 and z'. This shunt includes conductors 33 and 39 connected to conductors 33 and 311 respectively, and to the blades ot a two blade switch X4. The switch X* is set in different positions corresponding to the different p0- sit-ions in which the signal S is set. ln the diagrammatic representation shown, the rod S13 is connected at one end to the signal blade and at the other end to one arm ot a bell crank lever SM, and the other arm ot the bell crank lever S14 is connected to the switch Xt. The switch Xt controls connection between the lines 3S and 39 and 31 and 2G. lVhen the signal S is in the horizontal. or danger position, switch X* does not operatively connect the conductors 38 and 39 to the conductors 3l and QG. lVhen the switch Xt is in an intermediate position, however, corresponding to the intermediate or cautionary position ot' the signal, conductor 3S is connected to conductor 31, and conductor 39 to conductor 26. In the position of the switch X* corresponding to the full clear signal indication, conductor 3S is connected to a branch 26 ot the conductor 26, and conductor 39 is connected to the conductor 31. The conductor 31 includes a battery Q32 and is connected to the lines 31 and 30. rl`he conductor Q6 is connected to the conductors Q7 and 2S.

It will be apparent without detailed eX- planation that after the signal, is set in either the intermediate or full clear position to permit a train to move past the joints Z2, the connections controlled by the relays M, M and M2, will serve to connect the lines 31 and 2C in the same manner and under the same conditions as these relays connect conductors 4 and Q6 in the arrangement shown in Fig. 1, and that, in consequence, a current tlow is then set up through the circuit including the battery Q2 and conductors 31 and 26, switch Xt, conductors 38 and 39, portions of conductors 33Vand 34 and polarized magnet V, in the same direction as the current flow through the magnet V from the battery Q, which initially set the signal in the full clear or intermediate position. To prevent the conductors 33 and 311, armatures l and zi and conductors 35 and 36 from serving a low resistance shunt about the magnet V for current from the battery Q2 after the train movement has served to deenergize indicator magnet l or z" as the case may be, the resistance R is inserted in the initial energizing` circuit of the polarized armature U. rllhis resistance should be great enough on one hand to prevent any substantial diversion from battery Q2 in the shunt circuit about the polarized magnet V, described, and on the other hand of course should be small enough to permit the magnet V to be energized from the battery Q without making the voltage of the latter unduly large.

ln accordance with the provisions of the statutes l have illustrated and described the best forms of my invention now known to me, but it will be apparent to those skilled in the art that changes can be made in the torm ot the apparatus disclosed without departing' from the spirit of my invention.

It will also be apparent to those skilled in the art that certain features of the invention may sometimes be used with advantage without a corresponding use ot others.

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

1. In a block signal system, the combination with a pair ot' block sections and a signal governing the passage of trains into one. ot said sections from the other, of electric controlling mechanism for the signal, devices automatically responsive to the presence ot trains in said block sections, means controlled by one ot said devices for preventing the initial energization of said mechanism when said one section is occupied by a train, and means controlled by said devices lor maintaining the energization ot said mechanism on the passage of a train into said one section from the other section and until the rear end of the train passes through said one section so long as no other train enters said other section, said last mentioned means being rendered inoperative by the entrance of another train in said other section.

2. ln a three position signal mechanism, the combination With a signal and an actuating device therefor adapted upon a limited movement to move the signal from the danger position to an intermediate position, and on a further movement to move said signal into a third position, of a manually actuated mechanical latch normally preventing the movement of the actuating device to set the signal in a third position, and an electric loch for said latch.

3. ln a three position signal mechanism, the combination with a signal actuating` lever, of a stand in Which the lever is mounted, a latch mounted in said stand and movable into and out oit the position in which it projects into the path ot the lever and prevents the latter from being moved beyond the intermediate position into the clear position, but not interfering With the movement ot the lever into the intermediate position, a spring normally holding the latch in its said position, and a handle by which the latch may be manually retracted from its said position.

et. lin a. three position signal mechanism, the combination with a signal. actuating lever, ot a stand in which the lever is mounted, a latch mounted in said stand and movable into and out of, and having provisions whereby it may be manually moved out oit', the position in Which it extends across the path of the lever and prevents the latter from being moved beyond the intermediate position into the clear position, yielding means normally holding the latch in its said position, a locking part normally engaging said latch and positively holding it in its said position, and electro-magnetic means for moving' said locking part to tree the latch.

5. ln a block signal system, the combination with a manually actuated electric slot controlled signal and the electric slot thereof, of devices automatically responsive to the presence of trains in ditlierent portions ot' the block, means controlled by said devices for permitting the energization of said slot ivhen the section of the block adjacent the signal is free from trains, but preventing said energization when said section has a train in it, a lock normally preventing the movement ot the signal beyond an intermediate position, and lock releasing means also controlled by said devices, etlective only when the block is entirely free from trains, for initially releasing the lock,

6. In a block signal system, the combination with a signal, of a manually actuated signal setting lever, a latch movable into and out of the position in which it prevents the movement of the lever beyond an intermediate position, a locking part adapted to engage and hold the latch in said position, and electro-magnetic means tor moving said locking part to free said latch, said means being automatically responsive to the presence of trains in the block to Which the signal pertains and being capable of moving the loclring part out of engagement with the latch only when said block is entirely free from trains.

7. ln a block signal system, the combination with a signal, of a manually actuated signal setting lever, a latch movable into and out of the position in Which it prevents the movement of the lever beyond an intermediate position, a locking part adapted to engage and hold the latch in said position, electro-magnetic means for initially moving said locking part to free said latch, said means being automatically responsive to the presence of trains in the block to Which the signal pertains and being` capable ot moving the locking part out oi engagement With the latch only when said block is entirely tree from trains, and means con# trolled by the position of the signal for maintaining said locking part out of the position in Which the latch is free, regardless of the presence of trains in said block after, and While, the signal is beyond its intermediate position.

8. ln a block signal system, the combination with devices automatically responsive to the presence of trains in different portions ot' the bloeit, of a signal, a manually actuated signal setting lever connected to said signal, a latch n'iovable into and ont oit' the position in which it prevents the movement ot the lever beyond an intermediate position, a locking part adapted to engage and hold the latch in said position, electromagnetic means for moving said locking part to free said latch, said means being controlled by said devices and prevented thereby from moving the locking part out of engagement with the latch exceptwhen the block to which said signal pertains is 'free :trom trains, an electric slot in the connections between the lever and signal` and means controlled by said devices and the position ot said locking part adapted to energize said slot when said locking part engages and holds the latch in said position, and a particular portion of the block isl free from trains, although another portion of the block may be occupied by trains.

Geol?. BLACKIE, C. W. GRANT.

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