US3015464A

US3015464A - Railway switch control apparatus

Info

Publication number: US3015464A
Application number: US765836A
Authority: US
Inventors: Rankin J Bush
Original assignee: Westinghouse Air Brake Co
Current assignee: Westinghouse Air Brake Co
Priority date: 1958-10-07
Filing date: 1958-10-07
Publication date: 1962-01-02
Anticipated expiration: 1979-01-02

Description

Jan. 2, 1962 R. J. BUSH 3,015,464

RAILWAY SWITCH CONTROL APPARATUS Filed Oct. 7, 1958 2 ,Sheets-Sheet 1 BY ug .wwf

H125' TTOHNW Jan. 2, 1962 R. J. BUSH 3,015,464

RAILWAY SWITCH CONTROL APPARATUS Filed Oct. '7, 1958 2 Sheets-Sheet 2 BY @LA has HTWGBJVE'Y United States Patent O 3,015,464 RAILWAY SWITCH CONTROL APPARATUS Rankin J. Bush, Jeannette, Pa., assgnor to Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Filed Oct. 7, 1958, Ser. No. 765,836 4 Claims. (Cl. 246-258) My invention relates to railway switch control apparatus, and more particularly to a novel and improved hydraulic switch apparatus including control circuits therefor.

It is a principal object of my invention to provide an improved hydraulic switch apparatus for controlling track switches including means for biasing a track'switch to its extreme positions, and means for nullifying the effect of said biasing means during operation of said machine.

It is another object of my invention to provide an improved switch apparatus having means to enable the associated track switch to be trailed without damage to the machine.

In the attainment of the foregoing objects, I provide a source of fluid under pressure, a track switch operating cylinder, control valve means for controlling the supply of fluid to said cylinder, a linkage mechanism operatively connecting a piston in said cylinder to the track switch, and a second cylinder including a piston biased to an initial position by spring means, the piston in said second cylinder also being operatively connected to said linkage mechanism and the spring means being effective to bias said track switch to its extreme positions. In operation, said first piston actuates said linkage to move said track switch, the biasing effect of said spring means being nullified by fluid supplied to said second cylinder. During a trailing action said linkage and spring are arranged to initially oppose movement of said track switch from its initial extreme position and then -to aid movement of the switch to its opposite extreme position.

Other objects and advantages of my invention will become apparent from the following description and the accompanying drawings in which like reference characters refer to like elements throughout and in which:

FXG. l is a view partly in cross section and partly diagrammatic of the control apparatus according to my invention; and

FIG. 2 is a diagrammatic view of the electrical control circuits for the apparatus of FIG. l.

I shall first describe one form of switch control apparatus embodying my invention and shall then point out the novel features thereof in the appended claims.

Referring to the drawings, FIG. l shows my hydraulic control apparatus which may be used, for example, in railroad classification yards to control track switches connecting storage tracks to departure tracks. In such applications a locomotive operates between the departure track and the storage track -to pull a cut of cars from the storage track to the departure track. For limited switch operation, a switch may be remotely controlled. However, for extensive switching operation it has been found more convenient for each locomotive or switching crew to control movement of the switch by local operation of the switch machine. .As will be explained hereinbelow, I therefore provide both remote and local control means for my machine.

For operating my switch apparatus I utilize a prime mover, indicated as a motor 10, coupled to a hydraulic pump 11, which pump has its inlet port 11a connected by a line 12 to a source of hydraulic fluid here shown as a sump or accumulator 13. The discharge port 11b of pump 11 is connected by line 14 to a pressure or inlet port 15a of a double check valve 15 having an additional pressure ICC or inlet port 15b, an outlet port 15e, and a piston 15d. Movement of piston 15d to either side of valve 15 causes one of the pressure ports 1'5a and 15b to connect to outlet port 15e and blocks the passage from the other pressure port to outlet port 15C. Port 15b connects through a hand pump 10i), line 16, and line 12 to sump 113. As will be explained in more detail hereinbelow, in case of electrical power failure, hand pump 1&0 is operated by lever 99 to build up the hydraulic pressure in the apparatus to move the track switch. Port 15e connects through line 18 to inlet port 19 of control valve 20. Line 18 connects through line 23 to the input port 24 of a cylinder 25, and through line 18a to a cylinder 95. Cylinder 95 includes

pressure switches

93 and 94, of any suitable conventional type, which are actuated to open when the pressure in cylinder 95 reaches a predetermined level. As will be explained in detail hereinbelow, as the motor 1i) causes pump 11 to build up the pressure in the apparatus to a point above that required to complete the movement of the track switch, the excess pressure actuates the

pressure switches

93 and 94 to open or break the electrical circuits which energize the motor and the control solenoids of the control valve 2t?.

Control valve 20 includes a tubular housing 21 having a cylinder 30 formed in the central portion of the housing, and a pair of

chambers

31 and 32 formed at opposite ends of the housing, each of which chambers includes a cylinder positioned in approximately perpendicular relation to cylinder 36. Cylinder 30 receives a main spool valve unit 28 consisting of a rod 28a carrying three spaced pistons 28b, 28C 'and 28d. Piston 28C is positioned centrally on rod 23a, and pistons 28h and 28d are respectively positioned adjacent the ends of rod 28a. In actual practice spool valve unit 2S may be formed as a single piece. Each of the cylinders in the end chambers forms a control spool valve unit, as will be explained in more detail hereinbelow.

Housing 21 includes the single inlet port 19 and tive outlet ports 26a, 2Gb, 39, 41a and 4111. Ports 26h and 41a connect through

lines

42 and 43, respectively, to a track switch operating cylinder 22; and,

ports

26a, 39 and 41b connect through line i4 to sump 13. Further in the normal position of spool valve unit

2S outlet ports

26a, 26h, 41a and 41b communicate with cylinder 30.

A passageway 29 for permitting iiuid flow is formed in the upper portion, as oriented in FIG. l, of the wall of housing 21 and provides direct communication between inlet port 19 of housing 21 and each of the cylinders formed in

chambers

31 and 32. It will be understood that passageway 29 is in the form of a longitudinal aperture and that it does not extend around the circumference of housing 21. A central opening 27a in housing 21 provides communication between cylinder 30 and passageway 29. A pair of aligned but separated

passageways

52 and 53 for permitting liuid ow are formed in the wall of housing 21 at a point approximately diametrically opposite to passageway 29.

Passageways

52 and 53 communicate with sump 13 through ports 26a and 41b, respectively. Also, in the normal position of spool valve unit 23, both

passageways

52 and 53 communicate through ports 26a and 41b, respectively, to cylinder 30. There is, of course, no direct communication between

passageways

29, 52 and 53.

In the normal position of spool valve unit 28, piston 28C seals opening 27a in housing 21. However, to provide a measure of communication between valve 20 and sump 13 for venting the valve, piston 28C has an angular slot or groove 4t) which provides communication with passageway 29 through an outlet port 39 and a line 44 to sump 13. A choke or restriction, not numbered, is formed in outlet port 39 to limit the direct ow of iluid 3 between inlet port 19 and outlet port 39 so that fluid will not tend to bypass valve 26 and flow directly between the pump 11 and sump 13.

Pistons 28b and 28d are hollow and form cylinders, each of which receives a caged spring and plunger which are effective to center the spool valve unit 28 when the pressure exerted on either end of spool valve 28 by one or the other of the control valves is relieved, as will hereinafter be explained in detail. Pistons 28h and 28d are similar and function similarly. Referring, for example, to piston 28d, a caged spring 47 in cylinder 45 formed in piston 28d biases plunger 46 to the right-hand end of piston 28b. When the pressure exerted on the left-hand end of spool valve unit 28, as will be explained hereinbelow, is relieved, the caged spring 47 is etfective to return the valve to its center position. Likewise, the caged spring in piston 28b returns the valve unit 23 to its center position when the pressure on the righthand end of spool valve unit 28 is relieved.

Valve 26 is, of course, symmetrical about a vertical plane, as oriented in FIG. l, and the operation of the valve is similar for either left or right movement of spool valve unit 28. Assume, for explanation purposes that the spool valve unit 28 is moved to the left; a direct cornmunication will be established between inlet port 19 and line 43 through opening 27a, cylinder 30 and outlet port 41a, and at the same time, piston 28d will close outlet port 41h. Outlet port 2Gb will remain open, since piston 28b will not move a sudcient distance to close the port. In this manner a direct communication is provided through valve 20 to track switch operating cylinder 22 by a uid path which may be traced from inlet port 19,

opening 27a, cylinder 3i), outlet port 41a, and line 43v to cylinder 22. A duid return path may be traced from cylinder 22 through line 42, outlet port 26h, cylinder 30, outlet port 26a and line 44 to the sump 13.

The

chambers

31 and 32, which as previously pointed out, are formed at opposite ends of housing 21, and the control Yspool valves contained therein, are similar so that a detailed description of, say, chamber 32 and its con-y trol v'alve is deemed sulicient for an understanding of the operation of valve 20. A longitudinal aperture is formed in the right-hand wall, as oriented in FIG. 1, of chamber 32 to form a passageway 34 for liuid flow. Passageway 34 communicates with passageway 53 in housing 21 and outlet port 4112. A cylinder 35 in chamber 32 receives a control spool valve unit 36 comprising a rod 36a, and pistons 36b and 36e. Pistons 36b and 36C are mounted in spaced relation on rod 36a, which rod is normally biased downwardly, as shown in FG. l, by a coiled spring37. In the normal position of control spool valve unit 36, piston 36b is positioned approximately centrally in cylinder 35 and piston 36C is positioned adjacent the lower end of cylinder 35. The right-hand wall of chamber 32 is apertured to provide communication between passageway 34 and the upper, central and lower portions of cylinder 35 when the control spool valve unit 36 is in its normal position. Cylinder 35 also includes an opening 48 which communicates with the right-hand end of cylinder 30. A solenoid 38 circumposed about rod 36a, when energized, actuates rod 36a upwardly -to establish communication between passageway 29 and the central portion of cylinder 35. At the same time piston 36C interrupts communication between passageway 34 and the central portion of cylinder 35.

During local operation mechanical means are provided for actuating the control valve units in chambers 31 and i 32. A pair of beveled blocks 5@ and 51 are ganged to local control lever 99, as indicated by the dotted lines in FIG. l.

Blocks

50 and 51 are similar in operation and construction, and are associated with the control valves in

chambers

31 and 32, respectively. When, for example, local control lever 99 is moved to the left to a horizontal position, block 51 wedges against the enlarged end 52 of rod 36a to force control spool valve unit 36 upward.

Further, in the event of electrical power failure, means are provided for building up the hydraulic pressure in the apparatus. When lever `99 is initially moved to an approximate horizontal position to cause block 51 to raise the control valve unit 36 it is also in position to function as a hand lever for the hand pump indicated by reference character 100. Since the hand pump may be of any suitable conventional type no further description is deemed necessary. As is known, manual reciprocation of lever 99 causes pump 10il to increase the hydranlic pressure in line 16. This increased pressure causes piston 15d to move to the left and thereby connect inlet port 15b to outlet port 15C, line 18 and the `remainder of the control apparatus.

As mentioned above, output port 26h of'valve 20 connects through line 42 to a port 54 in the lower portion of a switching cylinder 22 which cylinder receives a rod 56a and piston 56b. Piston 5611 is positioned intermediate the ends of cylinder 22 to form upper and lower cavities 53a and 58b. Port 54 thus connects line 42 to cavity 54h, while a second port 55 on the upper portion of cylinder 22 connects line 43 to cavity 58a. Piston 56b moves in cylinder 22 in response to the pressure differential between

cavities

58a and 58b.

The free end of piston rod 56a is affixed by a pin 61 to the junction of

toggle arms

63 and 65 of a mechanical linkage 64. Linkage 64V includes three

arms

62, 63 and 65. Arm 62 is movably aflixed to arm 63 by pin 67 and arm 63 is movably aixed to arm 65 by pin 61. Arm 62 is pivoted on stationary pin 72 and arm 65 is pivoted on pin 71 which rides in a slot 70. Slot 70 permits pin 71 to move in a sidewise direction, as oriented in FIG. 1, but prevents any up or down movement of said pin. Arm 65 is connected by pin 66 to a throw rod 68 of the track'switch. Arm 62 has a pin 73 aiiixed thereto which pin rides in a closed slot 79 formed in a rod 76a. Rod 76a carries a piston 76b which operates in cylinder 25.

Port 24 in cylinder 25 connects line 23 to a cavity 69 formed in cylinder 25 on the left-hand side, as oriented in FIG. l, of piston 76b. Rod 76a and piston 76b are biased toward the left as shown in FIG. 1 by a coil spring 78 circumposed about rod 76a and contained within cylinder 25. Piston 76b is moved toward the right by Huid pressure admitted to cavity 69. A stop 77 on rod 76a limits movement of the rod 76a and piston 76b toward the right.

The electrical control circuitry for my Vswitch machine indicated in FIG. 1 is shown in more detail in FIG. 2. As mentioned hereinabove, provision is made for either remote or local control of my machine. The remote control circuitry will tirst be described. A remote control lever 81 normally in a central position as shown in FIG. 2 is movable either to the left or right, as oriented n the drawings, as desired to energize the switch machine to move the track switch to either of two positions here indicated as normal or reverse. Assume the switch is in the reverse position and it is desired to move the track switch to a normal position, lever 81 will then be actuated to Normal position a indicated by the dot-dash lines. At position a lever 81 connects electrically to contact 88 on lead 91, and'to contact 89 on lead 87. As lever 81 is moved to position a it physically engages a plunger S3 biased by a caged spring 84 tov return lever 81 to an intermediate position b, also indicated by dot-dash lines. At position b rod 81 connects only to contact S8 and lead 91. Lever 81 is initially urged to position a to energize the operating winding of a relay 92 by a voltage obtained from a source of potential 85 whose terminal B2 is electrically connected to lever 81. The energizing circuit for relay 92 may be traced from terminal B2 of source 85, lever 81, contact 89, lead 87, and the operating winding of relay 92 to terminal N. When energized, relay 92 picks up its front contacts and closes a stick circuit which may be traced from terminal B2 of source 85, lever 81, contact 8S, lead 91,

lead 86, contact 93 of pressure switch 95, lead 96, front contact a of relay 92, lead 90, lead 87, and the operating winding of relay 92 to terminal N. Consequently, relay 92 is initially energized directly through lever 81, contact 89 and lead 87, and then remains energized over lever 81, contact 89 and its stick circuit until the switching operation is completed; that is, until, as noted before, the pressure in the system increases and pressure switch 95 opens its contact 93 to interrupt current energy to relay 92. Energization of relay 92 causes solenoid 38 of control valve 20 to be energized over a circuit which may be traced from terminal B2 of source 85, over front contact b of relay 92, lead 97, and solenoid 38 to terminal N of source 85. Likewise motor is energized over a circuit which may be traced from terminal VB1 of source 85 over front contact c of relay 92, lead 98 and motor 10 to terminal N of source 85. As indicated in FlG. 2 terminal B1 of source 85 may be of different and higher potential than terminal B2.

Referring now to FIG. 1, the local control circuitry is as follows. As noted hereinabove, during local control operation, the control valve units in

chambers

31 and 32 of valve 20 are actuated mechanically instead of electrically. As local control lever 99 is actauted to the Normal position beveled block 57 mechanically ganged thereto, engages and Wedges against an enlarged top portion 52 of rod 36a vto lift the rod 36a and piston 36b. Referring now also to FIG. 2, in lifting rod 36a and piston 36b to the proper height, lever 99 is turned or rotated to an angle of 90, which in turn causes lever 99 to electrically contact either

brush

101 or 102, dependent on the direction ofvrotation of lever 99.

Brushes

101 and 102 are electrically connected by lead 103 so that regardless of the direction of rotation of lever 99, motor 10 will be energized over a circuit which may be traced from terminal B1, of source 85, through contact 94 of pressure switchy 95, lead 104, lever 99, brushes 101 or 102 and lead 103, lead 105 and motor 10 to terminal N.

The over-all operation of my switch apparatus will now be described. Assume initially that the track switch is in the position as shown in FIG. l and that said track switch is being trailed by a train moving from rails 4a and 4b to rails 5a and 5b. Assume further that my switch apparatus is in an unoperated condition with the control valve 20 in the position shown in FIG. l. As the first car wheel passes over the switch and-rail 4b is moved toward rail 5b throw rod 68 will move downwardly, as oriented in FIG. l. The end of linkage arm 65 attached to rod 68 is moved downwardly pivoting on stationary pin 71 and the opposite end of arm 65 is moved upwardly carrying rod 56a therewith. The end of arm 63 attached to rod 56a will also be moved upwardly causing the opposite end of arm 63, that is, the end which joins with arm "62 to move toward the `left to a position as indicated by the dotted circle 67. As the opposite end of arm 63 moves toward the left, arm 62 will pivot on stationary pin 72 causing the end of arm 62 riding in slot 79 of rod 76a to move toward the right and thus pulls rod and piston unit 76 to the right as shown by the dotted lines. Spring 78 and linkage 64 are interconnected to effect an over-center spring arrangement wherein the spring 78 opposes movement of the linkage 64 during the initial portion of the linkage travel and assists the movement of the linkage during the latter portion of the linkage travel. More specifically, spring 78 opposes movement of linkage 64 until

arms

63 and 65 are moved past the point where said arms form an imaginary straight line through their centers. As

arms

63 and 65 move past said imaginary line, the force of spring 78 will pull the upper end of arm `62, the end riding in slot 79, toward the left and the rod and piston unit 76 assume the postiion as shown in solid lines in FIG. l. As the upper end of arm 62 is pulled toward the left the lower end of arm 62 will movetoward the

right forcing arms

63 and 65 to snap to a position as indicated by the dotted lines 63' and 65 while arm 62 moves to the position as shown in FIG. l. The track switch will then be biased by spring 78 to a position wherein track 4b is adjacent track 5b. As rod 56a and piston 56b are actuated by linkage 64 the fluid in cavity 58a will be displaced through port 55 and line 43 to sump 13 through the fluid return path previously traced, and the other switch machine components including contact valve 20 will be unaffected by the trailing action.

Assume now that the track switch has been moved by the foregoing trailing action to a position with rail 4b alongside rail 5b and that it is desired to operate the track switch by remote control lever 81 to move rails 4a and 4b to the position shown in the drawings. Assume further that the linkage 64, rod 56a and piston 56b are in the position indicated by the doted lines 63 and 6'5. Lever 81 is in its unoperated or center position as shown in the drawings and is momentarily actuated toward the Normal position, indicated by line a against rod and piston unit 83 for a time sufficient to energize relay 92. Spring biased plunger 83 returns lever 81 to position b. Relay 92 will be energized from terminal B2 of source 85 through lever 81, contact 89 and the electrical circuit previously traced. Relay 92, when energized, picks up or closes its front contacts a, b and c. Frontcontact a closes the stick circuit for relay 92 over the circuit previously traced; front contact b completes the energizing circuit for solenoid 38 to actuate or lift rod and piston unit 36 upwardly, as oriented in the drawings, over the circuit previously traced; and front Contact c completes the energizing circuit for motor 10 overthe circuit previously traced, and motor 10 begins to build up the pressure in the pump 11.

When control valve unit 36 is moved upwardly, communication is established in valve 20 from inlet port 19 through passageway 29, cylinder 35 in chamber 32 and opening 48 to the right-hand end of cylinder 30 and against the right-hand end of piston 28d. The fluid pressure from pump 11 drives piston 28d toward the left. As is obvious, rod 28a, pistons 28b and 28e also move to the left. As piston 28e moves to the left communication is established in valve 20 from inlet port 19, through opening 27a in casing 27, and cylinder 30 to outlet port 41a, which is connected by line 43 to port 55 and cavity 58a of cylinder 22. The iluid pressure from pump 11 will cause rod and piston unit 56 to move downwardly. It follows that the fluid from cavity 58b in cylinder 22 will flow through port 54, line 42, outlet port 26h, cylinder 30, outlet port 26a, and line 44 to be returned to sump 13.

Movement of rod 56a and piston 56b in a downward direction actuates linkage 64. The ends of

arms

63 and 65 attached by pins 61 to rod 56 are moved downwardly and linkage 64 is moved to a position as indicated by the solid lines in FIG. l. As linkage 64 is actuated its arm 65 pivots on pins 71 and the end of arm 65 attached to track switch lever 68 is moved upwardly causing rails 4a and 4b to assume a position as shown in the drawings. At the same time fluid underpressure is routed to track switch operating cylinder 22, fluid under pressure is also routed through

lines

18 and 23 to port 24 and cavity 69 of cylinder 25. The uid under pressure in cavity 69 acts to move piston 76b Vagainst the biasing forcerof spring 78. In effect the pressure in cavity 69 nulliies or cancels the biasing force of spring 78 during the power movement of the trackvswitch. Thus the track switch is moved to its normal position smoothly and with no closure shock.

When the track switch reaches its eXtreme position the continued increase in pressure developed by pump 11 as it is driven by motor 10 causes pressure switch 93 to interrupt or open the stick circuit to relay 92, previously traced. Deenergizing of relay 92 causes its front contacts a, b and c to open. Opening of front contact a interrupts the stick circuit for relay 92; opening of front Contact b interrupts the energizing circuit to solenoid 38 to canse control valve unit 36 to assume the position as shown in FIG. l, and to relieve the pressure on the righthand end of main spool valve unit 28; and, openingv of front contact c interrupts the energizing circuit to motor to stop the pressure build-up. Main spool lValve unit 28 will then be returned to its normal position by the caged spring not numbered, in piston 28h, since the righthand end of piston 23d will be Vented through opening 48, the apertured central portion of cylinder 35,

passageways

34 and 53, outletV port 41h and line 44 to sump 13.

The operation of my switch apparatus during local control operation is similar to remote control operation. However, for local control operation, lever 99 when actuated to a Normal or Reverse position mechanically lifts the control valveunit 36 in chamber 38 or the control valve unit in chamber 31, respectively; no electrical circuits to energize the solenoids are necessary. -When lever 99 is actuated to either the -Normal or Reverse position motor 10 is energized from terminal B1 or source 85 over contact 94 of pressure switch 95 and the circuit previously traced. When the track switch reaches its eX- treme position the continued increase in pressure developed by pump 11 as it is driven by motor 10 causes pressure switch 93 to interrupt or open the energizing circuit for motor 10.-

lIt will, of course, be appreciated that my switch control apparatus operates in a similar manner when the control levers 81 and 99 are actuated to a reverse position.

It will also be appreciated that a principal advantage of my switch control apparatus is the provision of a means to bias the track switch to either of its extreme positions and means to nullify the effect of said biasing means during the operation of my apparatus. Further, a trailing move over the track switch does not cause any uid under pressure to be routed through the apparatus which iiuid might cause damage to said machine.

While my invention has been described with reference to a particular embodiment thereof, it will be understood that various modifications maybe made by those skilled in the art without departing from the invention. The appended claims are therefore intended to cover. such modifications within the Vtrue spirit and scope of the invention.

Having thus described my invention what I claim is:

1. Hydraulic apparatus arranged to receive fluid under pressure for operating a railway track switch between irst and second extreme positions comprising valve means for controlling the ow of said fluid, first and second track switch operating cylinders each including a rod and piston unit, linkage means operatively connecting said rod and piston units to said track switch, spring means biasing the rod andpiston unit of said second cylinder to the nearest extreme position during a trailing movement over said switch, said spring means being eiective during a trailing movement to initially oppose and then aid movement of said switch as it is moved from one to the other of its extreme positions, means for routing fluid to said iirst and second cylinders concurrently, the iiuid routed to said first cylinder causing its rod and piston unit to move said switch from one tothe other of its extreme positions, and the fluid routed to said second cylinder nullifying the force of said spring means to ease movement of the track switch under power from one to the other of its positions whereby closure shock of the switch is lessened.

2. Hydraulic apparatus arranged to receive fluid under pressure for operating a railway track switch between normal and reverse positions vcomprising control valve means, first and second operating cylinders each including rod and piston units, linkage means connecting said rod and piston units to said track switch, spring means for the rod and piston unit in said second cylinder for biasing said track switch through said linkage to its nearest position, said spring means and said linkage forming an over-center spring loaded arrangement such that during a trailing move over said switch said arrangement initially opposes and then aids movement of said track switch as it is moved from the one to the other of its positions, during said trailing movement the rod and piston units in said first and second cylinders being operated against negligible `liuid pressure, uid displaced from said iirst cylinder essentially by-passing said control valve means, during operation of said apparatus said control valve means routing fluid under pressure to said firstr cylinder to cause said track switch to be moved from one to the other of its positions, and means for routing fluid under pressure to said second cylinder ior overcoming the biasing force of said spring means concurrently as iiuid is routed to said first cylinder to ease movement of the track switch under power from one to the other of its positions whereby shock to the switch at closure is minimized.

3. Hydraulic apparatus arranged to receive uid under pressure for operating a railway 'track switch between normal and reverse positions comprising first and second operating cylinders each including rod and piston units, linkage means connecting said rod and piston units to said track switch, spring means for the rod and piston unit in said second cylinder, said spring forcing said linkage to assume one of two positions dependent on the position of the rod and piston unit in said first cylinder to bias said track switch through said linkage to its nearest position, said spring means and said linkage forming an over-center spring loaded arrangement such that during a trailing move over said switch said arrangement initially opposes and then aids movement of said track switch as it is moved from the one to the other of its positions, said trailing move causing the rod and piston unit in said first cylinder to move from one to another position but otherwise not aiecting operation of said apparatus, a control valve, electrical and mechanical control means for said valve, said valve routing Huid to said first cylinder to cause said track switch to be moved from one to the other of its positions, and means for routing fluid to said second cylinder concurrently as liuid is routed to said first cylinder for overcoming the biasing force oi said spring means which eases the power movement of the track switch and lessens the shock to the switch at closure.

4. Hydraulic apparatus arranged to receive iiuid under pressure for operating a railway track switch between normal and reverse positions comprising first and second operating cylinders each including rod and piston units, linkage means connecting said rod and piston units to said track switch, spring means for the rodand piston unit in said` second cylinder for biasing said track switch through said linkage to its nearest position, said spring means and said linkage forming an over-center spring loaded arrangement such that during a trailing move over said switchgsaid arrangement-initially opposes and then aids movement of said track switch as it is moved from the one to the other of its positions, control valve means comprising a housing having an inlet and a plurality of outlet ports, a main cylinder receiving a rod and piston unit and a pair'of auxiliary cylinders at either end of said main cylinder, each of said auxiliary cylinders receiving a rod and piston unit, said housing including a tluid passageway connecting to said inlet port and apertures connecting said auxiliary cylinders to said main cylinder, means for selectively actuating the rod and piston unit in one of saidauxiliary cylinders'to connect said fluid passageway means through said auxiliary cylinder to one end of said main cylinder to route said iiuid to actuate the rod and piston unit received therein, when actuated the rod and piston unit in said main cylinder providing direct communication between the inlet and an associated outlet-port, means conveying fluid from said associated outlet port to said rst cylinder to cause said track switch to be moved from one to the other of .its positions, and means for routing fluid to said second cylinder conllreutly as iluid is routed to said first cylinder for cancelling the biasing force of said spring means whereby the track switch is power operated from one to the other of its postos smoothly and without closure shock.

References Cte in the le of this patent UNTTED STATES PATENTS 1,735,019 Speer Nov. 12, 1929 Bone Ian. 24, 1933 Bone Spt. 14, 1937