Limp-in control arrangement for an electro-pneumatic brake control system

A limp-in control arrangement for an electro-pneumatic integrated control system for railway vehicles including a supply and exhaust magnet valve for electrically controlling the pneumatic brakes on the railway vehicle, an electromagnetic relay for sensing the operational condition of the electro-pneumatic integration control system, a switching device for enabling a limp-in control function when the electro-pneumatic integrated control system is experiencing a malfunction, an operating device for initiating a limp-in control function by releasing and reapplying the pneumatic brakes to allow the railway vehicle to be moved to a repair facility.

FIELD OF THE INVENTION
 This invention relates to a limp-in feature for controlling the air brakes
 for railway vehicles and, more particularly, to a limp-in control
 arrangement for permitting the application and release of the brakes on a
 disabled railway vehicle when the electro-pneumatic integrated control
 system experiences an electrical malfunction so that the disabled railway
 vehicle can be moved to a repair shop.
 BACKGROUND OF THE INVENTION
 In certain electro-pneumatic brake control systems, the brake pipe control
 is dependent upon the functional operation of the electronics. If the
 electronics in existing electro-pneumatic integration control system
 malfunction, there is currently no electrical way in the controlling cab
 to operate the train brakes. The present electro-pneumatic integrated
 control system is provided with a pneumatic backup arrangement to generate
 brake cylinder pressure when the brake pipe is varied. It would be very
 beneficial to provide an alternate electrical means for controlling brake
 pipe pressure when the computer of the electro-pneumatic integrated
 control system malfunctions. Such an arrangement could be used as a
 limp-in control to permit the trainman or operator to manually switch to
 this mode and move the train to a repair shop or the like.
 OBJECTS AND/OR SUMMARY OF THE INVENTION
 Accordingly, it is an object of this invention to provide a unique limp-in
 control feature for an electro-pneumatic integrated control system for
 railway vehicles.
 A further object of this invention is to provide a new arrangement of
 releasing the brakes on railway vehicles during an electronic failure.
 Another object of this invention is to provide a novel electrical apparatus
 for controlling the brakes on a disabled railway vehicle.
 Yet a further object of this invention is to provide a new and improved
 limp-in feature for allowing a railway vehicle to be moved by
 applying/releasing the brakes of a train.
 Yet another object of this invention is to provide a unique arrangement for
 electrically controlling the pneumatic-operated brakes on a railway train
 which is equipped with an electro-pneumatic integrated control system.
 Still a further object of this invention is to provide a novel and unique
 limp-in control arrangement for an electro-pneumatic integrated control
 system for railway vehicles comprising, an exhaust magnet valve and a
 supply magnet valve in which the electrical conditions control the brakes
 on the railway vehicle, means for sensing the operational condition of
 said electro-pneumatic integrated control system, means for enabling a
 limp-in control function when said electro-pneumatic integrated control
 system is experiencing a malfunction, means for initiating a limp-in
 operation by releasing and reapplying the brakes so that the railway
 vehicle may be moved to repair said malfunction.
 Still another object of this invention is to provide a limp-in control
 arrangement which is economical in cost, unique in design, efficient in
 operation, dependable in service, durable in use, and simple in
 construction.
 DESCRIPTION OF THE DRAWINGS
 The above objects and other attendant features and advantages will be more
 readily appreciated as the present invention becomes better understood by
 reference to the following detailed description when considered in
 conjunction with the accompanying drawings, wherein:
 FIG. 1 is a partial diagrammatic illustration of a manual limp-in control
 arrangement for an electro-pneumatic integrated circuit brake control
 system for railway vehicles in accordance with the present invention.
 FIG. 2 is a truth table of the positions of a pair of cam-operated switches
 when the brake handle is moved to its application, lap and released
 positions.
 FIG. 3 is a truth table of the electrical conditions of the supply and
 exhaust electromagnetic valves when the brake handle is moved to its
 application, release and lap positions.

DETAILED DESCRIPTION OF THE INVENTION
 Referring now to the drawing and, in particular, to FIG. 1, there is shown
 the limp-in control portion of an electro-pneumatic integrated control
 system for railway locomotives, such as, passenger trains or mass and/or
 rapid transit cars. As shown, the braking system includes a CS-2 type of
 automatic brake handle BH, which does not include a continuous range of
 brake applications but includes six discrete positions, such as: release,
 holding, lap, service, handle-off, and emergency. This limp-in control
 arrangement can also be used with standard pneumatics, CS1 or CS2
 arrangements with push-button switches.
 The release, handle-off and emergency positions behave in the same manner
 as the present continuous range handle operation. The release position
 discharges brake cylinder and charges brake pipe, the handle-off position
 bleeds off brake pipe giving a complete reduction, and emergency position
 initiates an automatic brake emergency. The service position reduces brake
 pipe at a controlled rate, and will continue to reduce it as long as the
 handle is in service position. The service position also acts as
 suppression position. Moving the handle from service position to the lap
 position halts the reduction at the current brake pipe pressure. The
 operator moves the handle back and forth in these positions to reduce
 brake pipe to the desired position, instead of a fixed handle position
 determining the reduction, and automatically lapping. With brakes applied,
 the operator may move the auto handle to holding position, and in this
 position brake pipe is allowed to recharge, but brake cylinder is held
 constant (brakes remain on). The pressure in brake cylinder will not be
 exhausted until the brake handle is moved back to release position.
 It will be seen that automatic brake handle operates a pair of movable cam
 members C1 and C2, which will be described in greater detail hereinafter.
 In viewing FIG. 1, it will be noted that the output of a filtered main
 reservoir MR is pneumatically connected to the input port SIP of the
 supply magnet valve SMV via pipe line PL1. The air pressure in the main
 reservoir MR is maintained at a desired psi level by a suitable air
 compressor (not shown). As shown, the output port SOP of the supply magnet
 valve SMV is connected to pipe line PL2 which in turn is connected by pipe
 line PL3 to the input port EIP of the exhaust magnet valve EMV and by pipe
 line PL4 to the input of an equalizing reservoir ER. The output of the
 equalizing reservoir is connected by pipe line PL5 to a relay air valve
 (not shown) which in turn is connected to brake pipe. The exhaust magnet
 valve EMV includes an output port EOP which is exhausted to atmosphere EX.
 In viewing FIG. 1, it will be appreciated that when the electro-pneumatic
 integrated control system is operating properly, the electromagnetic relay
 OR is energized so that the movable contacts A and A' engage their front
 contacts and connect one end of the coil of the exhaust magnet valve EMV
 to +24 VDC and one end of the coil of the supply magnet valve SMV to +24
 VDC, respectively. During normal operation, the movable contacts B and B'
 of the energized electromagnetic relay OR connect the other end of the
 coil of the exhaust magnet valve EMV to the drive card of the
 microprocessor or computer and also the other end of the coil of the
 supply magnet valve SMV to the drive card of the microprocessor or
 computer, respectively.
 It will be assumed that either the computer has malfunctioned, or the +24
 VDC power supply has been interrupted so that the operational relay OR
 becomes deenergized. This causes the movable contacts A, A', B and B' to
 drop away and assume the positions as shown in FIG. 1. Thus, the movable
 contacts A and A' engage the open back contacts while the movable contacts
 B and B' close the back contacts to return trainline 4T. As shown in FIG.
 1, the brakes are automatically applied during such electrical failures
 since the deenergized supply magnet valve SMV closes off the main
 reservoir and the deenergized exhaust magnet valve EMV exhausts the
 equalizing reservoir ER to atmosphere. In order to allow the train or
 relay car to limp-in to a repair shop or the like, some means must be
 provided to release the brakes. As shown, the limp-in control circuit
 normally opens double pole pushbutton electrical switch PBS. It will be
 seen that one terminal of the one pole P1 of the switch PBS connects power
 trainline 13T to the limp-in circuit while the two terminals of the other
 pole P2 of the switch PBS is connected to an annunciation circuit which
 alerts a maintainer or operator that the limp-in control is in operation.
 The other terminal of the one pole P1 is connected by lead L1 to the
 movable contact MC1 of a cam-operated switch A. The lead L1 is also
 connected to the movable contact MC2 of a camoperated switch B via lead L2
 and is connected via lead L3 to a movable contact MC3 of a minimum
 reduction pressure operated switch MRPS. The movable contact MC1 of the
 camoperated switch A normally engages stationary contact S1 which is
 connected to one end of the coil of the electromagnetic relay RL1 via lead
 L4, diode D1 and lead L5. The other end of the coil of relay RL1 is
 connected to the return trainline 4T. The movable contact MC2 of the
 cam-operated switch B normally engages open stationary contact S2. As
 shown, the relay RL1 is mechanically linked to a pair of heel contacts
 RL1A and RL1B. It will be noted that when the relay RL1 is deenergized the
 heel contacts RL1A and RL1B engage their back contacts BCA and BCB,
 respectively. The heel contact RL1B is connected to a stationary contact
 S3 of the minimum reduction pressured operated switch MRPS via lead L6.
 The back contact BCB of relay RL1 and the front contact FCA of relay RL1
 are open contacts. The front contact FCB of relay RL1 is connected to the
 lead L7. The stationary contact S1' of switch A is contact to heel contact
 RL1A via lead L8 while the stationary contact S2' of switch B is connected
 to the movable contact MC4 of an over pressure protection switch OPPS via
 lead L9. The stationary contact S4 of the over pressure protection switch
 OPPS is connected to one end of the electrical coil of the supply magnet
 valve SMV via lead L10. As previously mentioned, the other end of the
 electrical coil of the supply magnet is connected to the movable heel
 contact B' of relay OR via lead L11. As shown, the back contact BCA of
 relay RL1 is connected to one end of the exhaust magnet valve EMV via lead
 L12 while the other end of the electrical coil of the exhaust magnet valve
 EMV is connected to the movable heel contact B of relay OR via lead L13.
 Again, let us assume that the limp-in circuit is in the position as shown
 in FIG. 1, and that a maintainer or operator desires to release the brakes
 on the train or transit car. The limp-in feature is cut-in by depressing
 the push-button switch PB5 which closes the terminals of the two poles P1
 and P2. The closing of pole P2 energizes the annunciation circuit while
 the closing of the pole P2 energizes the relay RL1 via power trainline
 13T, pole PI, leads L1, L2, contacts MC1, S1, lead L4, diode D1, lead L5,
 coil of relay RL1 and return trainline 4T. The energization of the
 electromagnetic relay RL1 does not have any immediate function on the
 limp-in operation except that the movable contacts RL1A and RL1B are
 shifted from the back contacts BCA and BCB to the front contacts FCA and
 FCB, respectively. In order to release the brakes, the brake handle BH is
 moved to the release position which causes both of the cams C1 and C2 to
 pick up, as noted in the truth table in FIG. 2, to shift the movable
 contact MC1 and MC2 to engage stationary contacts S1' and S2',
 respectively. This will deenergize the relay RL1 since the cam C1 opens
 stationary contact S1. Since the pressure in the equalizing reservoir ER
 is below 103 psi at this time, the movable contact MC3 does not engage
 stationary contact S3 and the relay RL1 cannot be held energized over its
 front contact FCB. The picking up of both of the switches A and B causes
 power to be applied to both the exhaust and supply magnet valves EMV and
 SMV. The exhaust magnet valve EMV is energized over an electrical circuit
 extending from power trainline 13T, pole P1, lead L1, contacts MC1, Sl',
 lead L8, contacts RLLA, BCA, lead L12, the coil of exhaust valve EMV, lead
 L13, contact B, to return trainline 4T. Similarly, the supply magnet valve
 SMV is energized over an electrical circuit extending from power trainline
 13T, pole P1, leads L1, L2, contacts MC2, S2', lead L9, contacts MC4, S4,
 lead L10, the coil of supply valve SMV, lead L1, contact B' to return
 trainline 4T. Thus, when the exhaust and supply magnet valves EMV and SMV
 are energized, the equalizing reservoir ER will start to charge. That is,
 the energized exhaust valve EMV is closed off to atmosphere by upper valve
 portion of valve EMV while the energized supply valve SMV connects the
 equalizing reservoir ER to the filter main reservoir MR via pipe line PL1,
 the upper valve portion of valve SMV, and pipe lines PL2 and PL4. When the
 equalizing reservoir ER reaches 110 psig, which may be observed on a gage
 in the control cab, the operator should move the brake handle BH to a lap
 position wherein the switch A remains picked-up while the switch B is
 released by cam C2 and returns to its normal position as noted in the
 truth table of FIG. 2. However, if the operator fails to move the brake
 handle BH to its lap position to deenergize the supply magnet valve SMV,
 the equalizing reservoir ER will continue to be charged by the main
 reservoir MR. Now when the pressure reaches 112 psig, the over-pressure
 protection switch OPPS will open the contacts MC4 and S4 to deenergize the
 supply magnet valve SMV. This will prevent the equalizing reservoir ER
 from being overcharged even with the brake BH still in its released
 position. Leakage to the equalizing reservoir is not maintained in the
 limp-in mode of operation, except when the pressure drops below a 108 psig
 and the brake handle is placed in its released position. It will be
 appreciated that the minimum reduction pressure switch MRPS will be
 picked-up and close contacts MC3 and S3 but this will not affect anything
 at this time.
 Accordingly, the brakes of the vehicle are released and if the operator or
 maintainer moves the brake handle to its lap position, it will be seen
 from the truth tables of FIG. 2, the switch A is picked-up and the switch
 B remains released but the pressure in the equalizing reservoir ER remains
 unchanged. Thus, with the brakes released, the maintainer or operator may
 apply power to bring the disabled vehicle to the repair shop. Upon arrival
 at the repair shop, the throttle is moved to its off position and so that
 when the brakes are applied, a minimum reduction of the brake pipe of at
 least 6 psig is recommended. The minimum reduction pressure switch MRPS is
 utilized to ensure such a brake pipe reduction operation is carried out.
 Thus, when the maintainer or operator moves the brake handle BH to the
 apply position, both of the switches A and B assume their released
 positions as shown in the truth table of FIG. 2. It will be seen that when
 the switch A is in its released position, the relay RL1 is energized over
 a circuit path extending from power trainline 13T, pole P1 of pushbutton
 switch PBS, lead L1, movable contact MC1, stationary contact S1', lead L4,
 diode D4, lead L5, the coil of relay RL1 and to return trainline 4T. It
 will be noted that even if the operator returns the brake handle BH to its
 lap position, the relay RL1 will remain energized over its closed front
 contact FCB. The power is removed from the exhaust magnet valve EMV by the
 opening of the back contact BCA by the movable contact RL1A. Thus, the
 pressure in the equalizing reservoir ER will continue to drop until it
 reaches 103 psig at which time the contacts MC3 and S3 of the minimum
 reduction pressure switch MRPS become opened and deenergizes the relay RL1
 to close its contacts RL1A and BCA to thereby energize the exhaust magnet
 valve EMV. Accordingly, the exhaust valve EMV is cut-off to atmosphere to
 thereby maintain the equalizing reservoir ER at 103 psig. Thus, the
 minimum pressure reduction is achieved.
 Now, if the operator of the vehicle chooses to keep the brake handle BH in
 the apply position or moves it from the lap position to the apply
 position, the pressure in the equalizing reservoir ER will continue to
 drop. At any time after the minimum reduction is achieved, the pressure in
 the equalizing reservoir ER can be lower or held at that time.
 Accordingly, the brake pipe will continue to follow the equalizing
 reservoir and the vehicle brakes will follow the brake pipe. Any time
 after the minimum reduction has occurred, the equalizing reservoir can be
 recharged. The electrical condition or state of the supply and exhaust
 magnet valve SMV and EMV for the brakes in the apply, release and lap
 positions is shown in the truth table of FIG. 3.
 Thus, the present invention has been described in such full, clear, concise
 and exact terms as to enable any person skilled in the art to which it
 pertains to make and use the same, and having set forth the best mode
 contemplated of carrying out this invention. We state that the subject
 matter, which we regard as being our invention, is particularly pointed
 out and distinctly asserted in what is claimed. It will be understood that
 variations, modifications, equivalents and substitutions for components of
 the above specifically-described embodiment of the invention may be made
 by those skilled in the art without departing from the spirit and scope of
 the invention as set forth in the appended claims.