EP0064249B1 - Position drive for railway switches - Google Patents

Abstract

A high-speed switch machine for actuating railroad switch points. The machine has an electric motor which drives a hydraulic pump. The pump supplies pressure fluid to a hydraulic cylinder adapted to move the switch points from an initial to a second limit position. A four-way, two-position hydraulic control valve directs fluid to the cylinder such that the cylinder automatically operates in an extension and retraction cycle. The uni-directional motor and two-position control valve minimize response times of the actuating components so that the switch points are thrown in a short time period.

Description

The invention relates to an actuator for a rail switch for switching the switches between a first and a second end position, consisting of an electric motor with only one direction of rotation, a hydraulic pump driven by this motor, a hydraulic cylinder with a piston rod, a hydraulic four-way control valve for supplying Hydraulic fluid to the cylinder for the purpose of alternately driving the piston rod from a fully retracted position in the extending and retracting directions, from a two-position rotary cam driven by the piston rod and rotatable in opposite directions by successive extension strokes of the piston rod, from a functionally connecting the rotary cam to the switch Circuit for moving the switch between each end position based on a predetermined amount of rotation of the rotary cam in one direction or the other and from reversible detection means for determining the arrival of the Switch at the second end position during an adjustment stroke of the switch and for reversing the control valve in order to retract the piston rod into its fully retracted position.

In the patents US-A-3 363 097 and US-A-3 158 345 actuators of the aforementioned type are described. In order to carry out the extension and retraction processes of the hydraulic cylinder or its piston rod for the purpose of actuating the rotary cam, an electric motor which is reversible in its direction of rotation and which is connected by a complex electrical control circuit is used according to the first-mentioned patent specification. In addition to the fact that the complex control circuit causes corresponding manufacturing costs, there is a certain loss of time when reversing the electric motor, which means that a fault in the actuator is only noticed after a corresponding delay time, which can lead to dangerous situations when changing the switch. According to the second-mentioned patent specification, instead of the electric motor with the associated electrical control circuit, an electrically operated, hydraulic three-position four-way control valve is used in connection with a pressure accumulator. The three-position valve has a neutral intermediate switching position, from which it has to be switched to one or the other operating position so that the aforementioned hydraulic cylinder can be acted upon with the corresponding hydraulic control fluid. It is understandable that a considerable amount of time is required for the switching of the three-position valve, which also means that a fault in the actuator can only be determined after valuable time has elapsed, with the undesirable sequel already mentioned.

The object of the invention is to provide a switch actuator of the type mentioned in the introduction, which operates at high speed and is constructed with simple means such that there are no lost times when the hydraulic cylinder in question is actuated.

The solution is based on the above-mentioned actuator and is characterized in that the four-way control valve has a first position for extending the piston rod and a second position for retracting the piston rod, that this control valve is preceded by a directional control device actuated by a solenoid that pressure-sensitive means are connected together with the detection means, which cause the actuation of the solenoid and the directional control device to immediately place the control valve in its second position, which returns the piston rod to its fully retracted position, and that immediately upon the arrival of the piston rod in its fully retracted position Position responsive means are provided for deenergizing the solenoid and actuating the directional control device again to re-position the control valve in its first position, that the pressure responsive means and the directional control ereinrichtung for reversing the hydraulic two-position four-way control valve are effective to cause the retraction of the piston rod in the event of a switch failure when reaching the second end position and failure of the changeover of the detection means, and that feedback means including electrical holding circuits to effect a second cycle of the cylinder are provided in order to produce the piston rod extending again and the switch returning to the first end position in the event of failure to reach the second end position due to a fault.

A preferred embodiment of the actuator according to the invention is that the directional control device consists of an electrically controlled, hydraulic two-position four-way control valve which is supplied with pressure fluid by the hydraulic pump via a control line.

By means of the actuator according to the invention, simple means ensure that there are no more lost times when the hydraulic cylinder in question is switched on, since the four-way control valve connecting this cylinder is already in the corresponding switching position at the start of an extension stroke of the piston rod of the hydraulic cylinder and not only in this position Switch position must be brought, and this was based on the knowledge that the end of the retracting stroke of the piston rod can be used advantageously to change the four-way control valve. The directional control device is then preferably an electrically controlled, hydraulic two-position four-way control valve. Faults in the actuator can thus be determined immediately when it is actuated. These advantages are achieved with simple constructional means, so that the actuator according to the invention can be manufactured inexpensively. Furthermore, the avoidance of switching loss times ensures that the actuator operates at high speed.

• Figur 1 eine Aufsicht auf einen beispielsweisen Stellantrieb mit entferntem Deckel, um die inneren Bauteile zu zeigen,
• Figur 2 einen Schnitt nach der Linie 2-2 in Fig. 1,
• Figur 3 eine Aufsicht auf einen Positioniernokken,
• Figur 4 ein schematisches Schaltdiagramm des elektrischen Schaltkreises für den Stellantrieb,
• Figur 5 ein schematisches Schaltdiagramm eines anderen Bereiches des elektrischen Schaltkreises,
• Figur 6 ein schematisches Schaltdiagramm des Motorsteuerbereiches des elektrischen Schaltkreises,
• Figur 7 ein schematisches Schaltdiagramm des hydraulischen Steuerkreises.

The invention is explained below with reference to an embodiment shown in the accompanying drawings. Show it:

• FIG. 1 shows a top view of an exemplary actuator with the cover removed to show the internal components,
• FIG. 2 shows a section along line 2-2 in FIG. 1,
• FIG. 3 shows a top view of a positioning cam,
• FIG. 4 shows a schematic circuit diagram of the electrical circuit for the actuator,
• FIG. 5 shows a schematic circuit diagram of another area of the electrical circuit,
• FIG. 6 shows a schematic circuit diagram of the motor control area of the electrical circuit,
• Figure 7 is a schematic circuit diagram of the hydraulic control circuit.

The proposed machine or drive is generally designated 10 in FIG. It comprises a housing 12 with a base plate, side and end walls and with a hinged cover (FIG. 2). The housing forms a weatherproof and dustproof covering for the working components of the drive.

The rail switch (not shown) is adjusted by a hydraulic device, which includes a power cylinder, a hydraulic control valve, a pump with an electric motor and a tank for hydraulic fluid.

A fluid tank 14 includes a diffuser 16 in the fluid return line. One or more baffle walls 18 are provided in the tank to provide a calmed fluid supply to the pump inlet line 20. This helps prevent pump cavitation. A hydraulic pump 22 receives hydraulic fluid from the tank 14 via the inlet line 20. High pressure fluid exits the pump outlet line 24. A check valve CV 1 located in the line is provided in the outlet line 24.

The pump 22 is driven by an electric motor 26 which has only one direction of rotation, the motor being connected to the base plate via a bearing base 28. Electrical energy is supplied to the motor via a motor cable 30. The engine has an end bell 32 with mating openings to assist in engine cooling.

The pressure fluid from the pump reaches a distributor 34 by way of the outlet line 24. This comprises a valve 36 for reducing the pressure. This valve has connection points labeled P and T for the internal connection of a control line and an outlet line which runs to the tank 14. The distributor also contains a four-way hydraulic control valve 38. This valve 38 has P and T connection points for the hydraulic pressure lines and for a drain line leading to the tank. The valve also includes openings labeled A and B, which are connected to pivot connections 40 A and 40 B. A directional valve 42 is arranged directly above the hydraulic control valve 38. This directional valve is solenoid operated and controls the position of the hydraulic control valve 38.

A pair of pressure switches, one switch of which is visible at PS 1, is connected to the distributor 34. A fluid return line 43 provides fluid communication between the manifold 34 and the tank 14.

A hydraulic cylinder 44 is pivotally mounted at 46 on a bracket 48, which in turn is attached to the base plate of the housing 12. The end of the cylinder, which lies opposite the pivot point 46, slides on a bracket 50. The cylinder 44 is centered by two centering arms 52, which are connected to one another by tension springs 54. The arms 52 are pivotally connected to the bracket 48 at 56. The hydraulic cylinder 44 comprises an extendable piston rod 58 with a cam head 60 which is attached to the outer end of the piston rod. The cylinder 44 also has two pivot connections 62 A and 62 B, respectively on its piston side and on its piston rod side. The connection 62 A is connected to the swivel connection 40 A of the distributor 34 by a hydraulic pressure pipe 64 A. In the same way, the swivel connection 62 B is connected to the swivel connection 40 B via a hydraulic pressure line 64 B.

A rotary cam 66 comprises two cam pockets 68 A and 68 B, an upper, toothed shaft 70, a lower axle body 72 and a lower hub part 74 (FIG. 2). The lower axle body 72 is mounted in its bearing 76, which in turn is formed on the base plate of the housing 12. The lower hub part of the rotary cam is connected to a connecting rod 80 via an eye bolt 78. The connecting rod is connected in a suitable manner to the switch setting rod (not shown).

Two position-indicating cams 82 A and 82 B are mounted on the upper shaft 70. The cams are set to operate the limit switches LS 3 and LS 4. The cams actuate a limit switch when the rail switch has reached one of its limit positions or end positions. Details of the construction of the cam 82 A are shown in Figure 3; the cam 82 B has the same construction. The cam includes a body 84 with a central bore 86. An opening 88 is provided at its end of the body part, with a mounting bolt 90 extending through the separate leg portions formed by the opening.

A worm drive 92 is provided, the worm protruding into the bore 86. The worm thread engages in the toothing of the upper shaft 70 of the rotary cam. With this arrangement, the position of the cam track 94 can be precisely adjusted. The orientation of the Cam on the shaft can be adjusted by the worm 92. When the appropriate position is reached, the bolt 90 is secured to lock the cam in that position. This design eliminates the need for an adjustable limit switch arm because the adjustment is now provided in the cam mount. In order to summarize or explain the operation of the rotary cam, the following processes take place when the switch is switched from an initial end position to a second end position.

The piston side of the cylinder 44 is supplied with a fluid pressure, whereby the piston rod 58 is caused to extend. The cam head 60 engages the rotary cam 66 to cause the cylinder to pivot until the cam head is seated in the cam pocket 68A. A further extension of the piston rod causes the rotary cam to rotate further counterclockwise (FIG. 1). When the rail switch arrives at its second end position, the hydraulic fluid supply is reversed so that it communicates with the piston rod side of the cylinder. This causes the piston rod to retract. The centering arms 52 allow the cylinder to return to its original position. At this point, the rotary cam has been pivoted so that the cam head 60 will engage the cam rod 68 B due to a subsequent extension of the piston rod and will thereby return the switch to its initial end position.

The electrical and hydraulic circuits that control the operation of the point actuator are shown in Figures 4 to 7. According to FIG. 4, a 24 volt direct current source is connected to a symmetrical network as shown. A hand protection switch contact is provided. These contacts are opened when a control relay is actuated, which is actuated by the manual switch device on an actuator. This prevents an injury caused by an erroneous automatic switching process during an attempted manual switch setting.

The network contains three main lines 100, 102 and 104. The main line 100 comprises a pressure switch PS 1 and control relays CR3 and CR4 connected in parallel. Line 100 also includes a push button start switch PB1. A holding circuit 106 includes normally open contacts CR4. A second holding circuit 108 comprises a normally open contact CR1 and a normally closed contact CR2. Line 104 comprises a control relay CR2, contacts M2 and CR4 connected in parallel and a pressure switch PS2.

Line 104 includes a normally open limit switch LS3 and a normally closed limit switch LS4. Line 104 also has contacts CR1 and M1 connected in parallel and a control relay CR1. Red, green and yellow indicator lights are connected to line 104 as shown. These indicator lights can be located at a remote location, e.g. in a signal tower. The red light is switched on via line 110, the green light via line 112 and the yellow light via line 114.

The circuits for the motor and the motor starter are shown in FIG. 6. The motor is suitable for 220 volt operation with three-phase current at 60 hertz. The engine 26 may have an output of 3 horsepower and operate at a speed in a range from 1425 to 1725 revolutions per minute. The motor comprises a contactor 116 with overload protection devices, which are designated OL and with the motor contacts M. The electrical energy is supplied via the lines L1, L2 and L3.

The control circuit is shown in Figure 5. Electrical energy with 220 V and 60 Hz is present on lines L2 and L3. Line 118 includes a motor control signal M, overload protection contacts OL and a contact CR2. Line 120 comprises contacts M3 and CR3 connected in parallel, these in series with a normally closed contact CR3 and with a solenoid SOL. Both lines 118 and 120 are connected to the point L3 via an on-off switch, the switch being part of the push-button switch PB1.

The hydraulic circuit is shown in Figure 7. This is a schematic representation of those parts which have been shown and described above in connection with FIGS. 1 and 2. The same reference numbers are therefore used for the same parts. The internal connections of the manifold 34 include a hydraulic pressure line 122 that directs pressure fluid from the pump outlet line 24 to the hydraulic control valve 38. A drain line 124, which includes a check valve CV2, connects the control valve 38 to the tank return line 43. The breakdown valve 36 is to be provided between the lines 122 and 124 to prevent damage to the system in the event of a misconstruction.

The hydraulic control valve 38 is a four-way, two-position valve. The normal working position is designated 1 and shown in Figure 7. The reverse position is designated by 2. Valve 38 is adjusted between positions 1 and 2 by the control pressure in lines 126 and 128. The pressure in these lines is in turn controlled by the directional valve 42. This directional valve is shown in its normal working position 1 and is moved into its reverse position 2 by the solenoid SOL. The control pressure is supplied via line 130 and removed from pressure line 122. A tank or drain line 132 connects the outlet of the directional valve 42 to the tank 14. The hydraulic valve 38 is connected to the cylinder bores 64A and 64B via the lines 134 and 136. Pressure switches PS1 and PS2 communicate with lines 134 and 136, respectively.

The switch actuator functions as follows:

The drawings show the switch actuator and the control circuits in their normal working position. In this state, the rail switch is in the open position, with the limit switch LS3 normally open and the limit switch LS4 normally closed. The motor 26 is switched off and the pressure switches PS1 and PS2 are closed. The green indicator light is switched on via lines 104 and 112.

It should be noted that in this described state, each part is ready for the next switching operation. The hydraulic control valve 38 in position 1 will immediately deliver pressurized fluid via lines 134 and 64A to the piston side of the cylinder 44. No displacement of the valve control members or the valve slide or the like. Or other time-consuming activities are necessary to prepare the actuator for a switch operation. This increases the speed of the point actuator, thereby reducing the time required for an actuating process.

A course setting is initiated by pressing the start button PB1 (or the remote start button). This connects the 220 volt source to points L2 and L3 in Figure 5 and energizes control relays CR3 and CR4. Contacts CR4 on line 106 close to hold the circuit via line 100. Contacts CR4 on line 102 also close and energize control relay CR2. As a result of the excitation of the relay CR3, the contacts CR3 in line 120 (FIG. 5) close and open accordingly. When relay CR2 is energized via line 102 and contact CR3, the normally closed contacts CR2 in holding circuit 108 open and the contacts in line 118 close. This last process energizes the relay M by closing the contacts M (Figure 6), whereby the motor 26 is started. At the same time, the contacts M1, M2 and M3 close in the corresponding lines 104, 102 and 120. When the engine starts, hydraulic pressure fluid becomes to the piston side of the cylinder 44 via the hydraulic lines 24 and 122, via the control valve 38 in position 1 and via the Lines 134 and 64A passed. As a result, the piston moves and the piston rod extends from the cylinder and pivots the rotary cam 66, as has already been explained. The operation of the control circuit up to this point in time can be referred to as the order of extension.

When the rotary cam 66 begins to rotate, the actuating cam 82A turns off the limit switch LS3, thereby changing the state of LS3 to a closed position. As can be seen from FIG. 4, the green indicator light is thereby switched off and the red indicator light is switched on via line 110. The red indicator light informs the control personnel that the rail switch is in an open position. Closing LS3 also energizes relay CR1 via line 104 and contacts M1. This closes the contacts CR1 in both the line 104 and the holding circuit 108. When the rail switch safely reaches the transfer position, the cam 82B brings the switch LS4 into an open position. This de-energizes the relay CR1 and again opens the contacts CR1 in the line 104 and in the holding circuit 108. Likewise, the changed position of LS4 switches off the red indicator light and switches on the yellow indicator light via line 114. This yellow light informs the control personnel that the turnout is in the turn out position.

At this time, the following processes take place, which can be summarized under the term move-in order. When the rail switch reaches the second end position, the cam 66 is prevented from further pivoting. As a result, the piston rod 58 is also prevented from extending further. This causes pressure to build up on lines 64A and 134. When the pressure reaches a set limit, the pressure switch PS1 opens, breaks the circuit on line 100 and de-energizes relays CR3 and CR4. This causes the following events. The contacts CR4 in the holding circuit 106 open, so that, together with the previous opening of the contact CR1, the line 100 is not energized until the pushbutton switch is subsequently actuated. Contacts CR4 on line 102 also open, but relay CR2 remains energized via PS2 and M2. De-energization of CR3 causes contacts CR3 in line 120 to open and close accordingly. Since contacts M3 are closed at this time, solenoid SOL is energized via line 120. The solenoid reverses the position of the directional valve 42 (FIG. 7) so that it moves from position 1 to position 2. This causes the pressurized fluid in control line 130 to be directed into line 128. Line 126 is then connected to drain line 132. This reversal of the control pressure causes the main hydraulic control valve 38 to move from position 1 to position 2. When the master valve 38 reverses, pressurized fluid is directed to the piston rod side of the cylinder 44 via lines 122, 136 and 64B. Likewise, the pressure in lines 64A and 134 is simultaneously reduced via drain line 124. This causes the pressure switch PS1 to close again. However, because both the holding circuit 106 and the holding circuit 108 are open at this point, the extension order is not repeated.

When the piston and piston rod reach the fully retracted position, pressure begins to build up in lines 64B and 136. When this pressure reaches a preset limit, the pressure switch PS2 opens. This breaks the circuit on line 102 (Figure 4), thereby de-energizing relay CR2. Close contacts CR2 in holding circuit 108 while contacts CR2 in line 118 open. This last process de-energizes relay M, causing contacts M in motor starter 116 (FIG. 6) to open. The motor 26 is thus switched off. Contacts M3 in line 120 also open, which results in de-excitation of the solenoid SOL. This in turn allows the directional valve 42 to return to position 1, whereby the control pressure in line 128 is reduced and instead is supplied to line 126. The control pressure in line 126 causes hydraulic control valve 38 to return to position 1. When this position 1 of the valve 38 is reached, the line 136 is vented via the drain line 124, which results in the closing of the pressure switch PS2.

The actuator is now in the state for a change from the curve position to the open position. This is basically achieved by the same extension and retraction sequence as described above, with the exception that the limit switch LS4 is only moved from the open position to the closed position (which turns the yellow indicator light off and the red indicator light on) and that the limit switch LS3 is then moved from the closed position to the open position when the through position is reached (and then the red indicator light goes out and the green indicator light comes on).

If a fault occurs at the switch during an actuating process, feedback means in the control circuit automatically return the switch to its first end position. This is accomplished in the following way. A normal extension sequence is carried out, but the second end position is not reached due to the fault. Therefore, the limit switch LS3 closes in the case of an actuation process from the through position to the curve position, but the limit switch LS4 is not opened. The red indicator light thus remains switched on, the relay CR1 remains excited via the line 104 and the contacts CR1 in the holding circuit 108 remain closed. The breakdown on the switch causes a pressure to build up on the piston side of the cylinder 44, which results in the opening of the pressure switch PS1. The pull-in order described above then takes place. When the piston is fully retracted, pressure builds up in lines 64B and 136. This opens pressure switch PS2 as in the normal pull-in order. However, de-excitation of CR2 due to the opening of PS2 completes the holding circuit 108. Therefore, as soon as PS2 closes again, a second extension sequence is initiated via the holding circuit 108 and the line 100. This second extension causes the rotary cam 66 to move back to its initial position. In the case observed here, this will result in the limit switch LS3 being opened and the red light being switched off and the green light being switched on. A normal withdrawal order then takes place. An attempt to turn the turnout failed, but the turnout is not left in an open state.

Claims (3)

1. Railroad switch machine for throwing switch points between initial and second limit positions, comprising a unidirectional electric motor (26), a hydraulic pump (22) driven by the motor, a hydraulic cylinder (44) including a piston (58), a fourway hydraulic control valve (38) to supply pressure fluid to the cylinder for alternatively driving the piston from a full retracted position in an extending and in a retracting direction, a two position rotary cam (66) engageable by said piston and adapted to be turned in opposite directions by successive extension strokes of the piston, connecting means operatively connecting the cam to the switch points to move the switch points between either limit position upon a predetermined amount of rotation of the cam in one direction or the other, and reversing detecting means (LS3, LS4) operable to detect arrival of the switch points at the second limit position during a throw of the switch and to reset the control valve (38) for retracting the piston in its full retracted position, characterized in that the fourway control valve is a two-position fourway control valve (38) with a first position (1) for extending the pistonrod and with a second position (2) for retracting the pistonrod, that a directional control device (42) actuated by a solenoid (SOL) is pre-arranged to said control valve (38) for its resetting, that pressure responsive means (PS1) are arranged to cooperate with said detecting means for producing actuation of said solenoid and its device (42) for setting said control valve (38) immediately to its second position (2) retracting the piston (58) in its full retracted position, that pressure responsive means (PS2) are provided responsive to the arrival of the piston in its full retracted position immediately to deac- tuate said solenoid (SOL) and again actuate the device (42) for resetting the control valve (38) to its first position (1), that the pressure responsive means (PS1) and the device (42) are effective to reverse the hydraulic two-position fourway control valve (38) to cause retraction of the piston in the event the switch points encounter an obstruction in reaching the second limit position and fail to reverse the detecting means (LS3, LS4), and in that recycling means including electrical holding circuits (104, 108) are provided to cause a second cycle of the cylinder when an obstruction is encountered, to thereby produce re-extension of the piston and return of the switch points to the initial limit position when there is a failure to reach the second limit position because of an obstruction.

2. Machine according to claim 1 characterized in that the two-position fourway control valve (38) is actuated by an electrically controlled hydraulic directional control valve (42) supplied by the pump (22) through a pilot line (130).

3. Machine according to claim 1 characterized in that the detecting means include at least one limit switch (LS3, LS4) and a position cam (82A, B) prearranged to said limit switch, and in that said position cam is secured on the rotary cam (66).

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