GB2060171A - A touch sensitive control - Google Patents

Abstract

An electric locomotive is provided with a touch sensitive control responsive to signals generated and transmitted through the driver either by the driving gear of the locomotive or by an artificial signal generator and antenna. The driver transmits these signals by hand contact with a touch plate 309 on the locomotive control handle to amplifiers 301 to 303. Amplifiers 301 and 302 have resistive capacitive circuits to effectively exclude unwanted signals and circuit 331 provides a threshold. A further amplifier (Fig. 3 B1) connected to amplifier 303 controls a relay through a transistor, which in turn controls an emergency brake. Providing a signal of the requisite frequency is present at touch plate 309 the brake is held off, but not otherwise. If the driver removes his hand from the control handle the transmission link is broken and no signal is present at the plate 309. A resistive capacitive time delay circuit connected to the input of the further amplifier delays operation of the brake and disconnection of the propulsion mechanism from the driving wheels for a predetermined period the duration of which is pre-set by a variable resistor and provision is made for preventing release of the brake after operation until a requisite signal is present at plate 309 for more than a predetermined minimum period. <IMAGE>

Description

SPECIFICATION A touch sensitive control The present invention relates to a touch sensitive control particularly, but not exclusively, for a locomotive deadman's handle or control.

Previous controls of this nature have suffered from the disadvantage that they have imposed an additional, often inconvenient and/or uncomfortable requirement on the locomotive driver as a result of which the driver has attempted in some way to by-pass the control and thus to render it ineffective. Thus, for example, in the case of a lever which must be constantly urged to an operative position to prevent an emergency brake coming into operation, ways have been found to tie the lever in the operative position with the result that, should the driver become incapacitated for some reason the control remains operative and the emergency brake is not applied as it should be.

According to the present invention there is provided a touch sensitive control comprising a touch plate and circuitry connected to the touch plate, the circuitry comprising filter means operative to pass signals entering at the touch plate to a detection circuit and the detection circuit being operative to detect signals so passed exceeding a predetermined magnitude and to produce a control signal in the event that such signals are detected.

An advantageous embodiment of the invention may comprise any one or more of the following preferred features:- (a) The filter means comprises one or more operational amplifiers, the or each amplifier having a tuneable feedback path comprising a capacitor and resistor in parallel.

(b) The detection circuit comprises a diode and a variable resistor is provided to vary the threshold value of the circuit.

(c) The detection circuit comprises a light emitting diode operative to be switched on when a signal above the predetermined threshold level is present.

(d) The detection circuit comprises an operational amplifier and a transistor which is operative to be switched on when a signal above the predetermined threshold level is present.

(e) The transistor of (d) is operable to control the flow of current through the coil of a relay, the contacts of which are disposed in a solenoid circuit which, when energised, holds a locomotive emergency brake off.

(f) A resistive-capacitive combination is connected to one input of the operational amplifier of (d) which maintains an input at the amplifier terminal for a predetermined time after the signal ceases to be detected.

(g) The predetermined time of (f) is variable by means of a variable resistor.

In order that the invention may be more clearly understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which, Fig. 1 is a pneumatic circuit diagram for a locomotive, Fig. 2 is an electrical circuit diagram for a locomotive, Fig. 3 comprising constituent sub-Figures 3A, 38(1) and 3B(2) is a circuit diagram of a sensing unit for a deadman's handle for a locomotive, Fig. 4 is a plan view of the locomotive control desk showing the locomotive controls, and Fig. 5 is a pneumatic circuit diagram for a locomotive showing a modification of the arrangement of Fig. 1.

Referring to Fig. 1, four pneumatically operable brake cylinders 2 are supplied with air from a main air reservoir (not shown) through a pneumatic supply circuit. The main air supply line, referenced 3, leads from the reservoir via an electropneumatic valve 5, emergency valve 4 which is controlled by the valve 5, and double check valve 8 to the brake cylinders 2. The double check valve 8 is also connected at 11 to the drivers direct brake valve, a dupiex gauge 9 is connected both to the supply line 3 and on the cylinder 2 side of the check valve 8, and electropneumatic pressure switches 1 OA and 1 OB connect opposite input sides of the check valve 8 to segments T9 and T10 of a connection strip 12 and to a pilot switch 13 (see Fig. 2). Segments T1 to T8 are connected to touch sensors on the locomotive controls.

Referring to Fig. 2, the electrical wiring diagram corresponding to Fig. 1 is shown. The various items of electrical equipment of the locomotive are supplied from a battery (battery sections referenced X and Y) via parallel contacts P 1-3 and series contacts S1-3. These series parallel contacts are provided because a separate fieid in the traction operation is used to enable the generator to start the locomotive diesel engine.

Front, rear and cab lights and a heater fan L1, L2, L3 and L4 respectively are supplied via respective fuses F2-F5, the traction control circuit via pilot switch 13, engine start solenoids SAS and SBS via engine start buttons AS and BS and engine stop solenoids SA and SB via engine stop buttons ASS and BSS. The traction control circuit comprises a fuse F7, switches SAC, SBC, earth leakage relay ELR, motor contacts MA and MB comprising the power controller, motor windings, MAW and MBW, field windings FSA and FSB and a field shunt relay FSR.

The function of the pilot switch 13, is to enable the driver to isolate the traction control circuitry when a locomotive is left standing so as to prevent accidental application of power by untrained persons. When the driver causes the locomotive to move off after having been stationary the power control lever is moved from the closed position.

This initial movement causes contacts MA and MB to close. In doing so they connect their respective generators to their motors at minimum generator output voltage. As the power controller becomes further advanced generator voltage builds up as a result of engine speed (the power control levers at this stage open up the speed control levers on the diesel engines via mechanical linkage). The main traction generator is initially excited by the battery charging dynamo but becomes progressively self excited as its output builds up.

The earth leakage relay is optional which when fitted as here detects leakage to frame on any circuit, and, if such leakage is detected, disables the traction control circuit. The ELR has a re-set button but will not re-set until any earthing faults have been cleared.

Segments 13 and 14 of the connection strip 12 are connected to the normally open brake pressure switch 1 OB, segments 15 and 16 to the emergency brake solenoid coil 366 (see Fig. 3), and segments 18 and 17 are connected to the negative and positive terminals respectively of a 24 volt D.C. supply.

Referring to Fig. 3 which comprises three constituent Figures 3A, 3B1 and 3B2, the electronic sensing unit for the deadman's handle of the locomotive (the pneumatic and electrical wiring diagrams of which are shown in Figs. 1 and 2 respectively), comprises four operational amplifiers 301, 302, 303 and 304. Amplifier 301 has one input connected via a resistor 305, and capacitor 306 to a terminal 307 which is in turn connected via the central conductor of a coaxial cable 308 to a touch plate 309 on the deadman's handle in the locomotive cab. The capacitor 306 isolates DC voltage from the touch piate 309.Odd numbered inputs T1 , T3, T5, T7, T9, T1 1 of the connection strip 12 are wired in parallel and connected to terminal 307 and even numbered inputs T2, T4, T6, T8, T10 and T1 2 of the connection strip 12 are wired in parallel and connected to the sheath of the coaxial cable which is earthed at 310.

Each amplifier 301,302,303 and 304 has an input connected through respective resistors 311, 312,313 and 314 to a positive 15 volt supply.

Amplifiers 301 and 302 have feedback loops comprising a parallel combination of a resistor and capacitor to tailor the frequency response. Thus capacitor 315 and resistor 316 are connected across amplifier 301 and capacitor 317 and resistor 318 are connected across amplifier 302.

The output of amplifier 301 is connected via a series connection of a capacitor 320, resistor 321 and variable resistor 322 to the negative input of the amplifier 302. The output of amplifier 302 is connected via a series connection of a capacitor 330 and a trip circuit indicated generally by the reference numeral 331 to the positive input of the amplifier 303. The trip circuit 331 comprises a series connection of a diode 332 and resistor 333 connected between the capacitor 330 and positive input of amplifier 303 and a further diode 334 and two further capacitors 335 and 336. The diode 334 is connected between the input side of diode 332 and earth and capacitors 335 and 336 are connected between respective sides of resistor 333 and earth.Capacitor 336 acts to remove unwanted spikes on the signal fed to the positive input of amplifier 303 and a further capacitor 337 acts to remove the spikes on the power supply fed to the negative input of amplifier 303.

The output from amplifier 303 is earthed through a series connected resistor 340 and light emitting diode 341. This output is also connected to the negative input of amplifier 304 via a diode 342, resistor 343 and resistor 344. The junction of resistors 343 and 344 is connected to the 1 5 volt power supply through a resistor 345 and switch 1 OB, to earth through a capacitor 346 and to earth through a resistor 347 and variable resistor 348.

The output from amplifier 304 is connected through a resistor 360 to the base of an NPN transistor 361. The emitter of this transistor is connected through a diode 362 to earth and the collector is connected through a further diode 363 to a 23.5 volt power supply. The coil 364 of a heavy duty relay is connected across the diode 363, the diode 363 acting to prevent EMF generated in the coil. The contacts RA1 of the heavy duty relay connect a diode 365 to a 23.5 volt power supply.

The coil 366 of an emergency brake solenoid, which requires 24v to hold it off, is connected across the diode 365. The power supply circuit comprises a diode 367 connected in series with a resistor 368 to the positive pole of a 24 volt supply. A zener diode 369 is provided to stabilize the power supply with a +25% tolerance. This zener is connected between the earth line of the supply and the terminal of the resistor 368 remote from the diode 367. Capacitors 370 and 371 are connected in parallel with the zener 369 and filter power supply interference. The 23.5 volt supply is taken from the junction between resistor 368 and diode 367 and 15 volt supply from the junction between the zener 369 and resistor 368.

Fig. 4 shows a plan view of the locomotive cab.

There are two separate sets of controls located at opposite sides respectively of the cab. Each set comprises two throttle handles 401 and 402, 403 and 404, a straight air brake handle 405, 406, operation of which causes switch 1 OB to become activated in the process of making a normal straight air brake application, and reverser handles 407, 408. The throttle handles are provided with touch sensitive areas respectively connected to segments T1 to T8 of the connection strip.

The operation of the deadman's handle sensing unit is as follows. A locomotive driver boarding a locomotive equipped with the above described system will generally find one or other of the following two sets of conditions existing. Either the locomotive will have been temporarily out of service, for example at a driver's shift change, or it will have been out of service for some time such as when it has been parked overnight. In the first case, the locomotive air reservoir connected to line 3, Fig. 1, will be found to be charged and a deadman's handle application will have taken place as a result of the previous driver having vacated the cab. The parking brake should have been applied.Under these circumstances the driver taking over simply has to proceed with his normal driving technique, the deadman's application being automatically cancelled at a predetermined period after he takes hold of the touch sensitive driving controls situated on the throttle.

These driving controls are insulated from the metal structure of the locomotive.

In the second case the locomotive should be found to have its reservoir discharged, the engine stationary and the parking brake applied. In this case the driver should perform his normal start up procedure, during the course of which, main reservoir and brake cylinder 2 pressures will build up simultaneously due to the action of the emergency relay valve 4, until the latter pressure reaches a predetermined figure at which point, cylinder pressure will stabilize but main reservoir pressure will continue to build until the compressor becomes unloaded. At this stage the locomotive is fit to be driven and again when the driver takes hold of the touch sensitive driving controls the deadman's handle application will be cancelled after a predetermined period and the locomotive can be driven normally.

When the driver grasps the controls as mentioned earlier he effectively connects himself to the touch plate 309 and thence to the touch sensitive circuitry which is connected to the plate 309. The signals received by the driver's body, acting as a receiving antenna, are transmitted by an antenna which may be mounted under the floor boards of the locomotive cab, in the cab roof, or on the cab side. The signals are the ambient electrical noise generated by the electrical equipment of the locomotive which operates when the locomotive is operating. For this reason, the system functions only when the locomotive is operative, the brake control by the deadman's handle being automatically applied when it is not.

In an alternative embodiment, instead of relying on ambient electrical noise, a still higher level of security maybe achieved by incorporating a signal generator to produce a special signal to which the detection and processing circuitry may be timed to respond. The signals picked up by the driver are fed to the processing amplifiers 301 and 302 via the coaxial cable 308. The coaxial cable excludes unwanted signals and the amplifiers 301 and 302 are tuned to and pass only signals of a particular frequency. When these signals exceed a preset adjustable tripping level provided by trip circuit 331 and output signal appears at the output of amplifier 303 and light emitting diode 341 is switched on thus indicating that the locomotive driver is touching the controls.The output signals at the output of amplifier 303 also results in an output signal at the output of amplifier 304 which is fed to the base of transistor 361 via resistor 360 to switch on this transistor and cause current to flow through the relay coil 364. Diode 362 ensures the release of the relay. This relay coil current holds relay contacts RA1 closed and the coil 366 of the emergency brake solenoid of the valve 5 (Fig. 1) is also supplied with current thus enabling the emergency brake to be held off. The trip level may be adjusted by adjusting the variable resistor 322 which sets the gain of the preceding stages up to the function of 317, 318 and 330.

Whenever the driver's hand is removed from the touch sensitive controls the input signal to amplifier 301 will disappear thereby allowing timing circuits to come into operation which, after a pre-set time, cause the relay contacts RA1 to change over thereby removing the 24 volt supply from the emergency brake valve allowing air to pass on to the emergency relay valve and thence to the brake cylinder 2. At the same time the propulsion mechanism of the locomotive is disconnected from the driving wheels. Referring to Figure 2, this is done in the diesel electric locomotive arrangement shown by opening switch 1 OA. This in turn takes out main traction contactors MA and MB. In a diesel hydraulic locomotive arrangement opening 1 OA would operate a magnetic valve thus allowing air to pass to the clutch cylinder of a magnetic clutch.

The timing delay is provided by the resistive capacitive combination of capacitor 346 and resistor 347 and 348 and the adjustment of this timing delay period from between 1 and 20 seconds may be achieved by appropriate adjustment of variable resistor 348. This delay enables the driver to release the controls for the delay period within the emergency brake immediately coming into action. This may be necessary in cabs where two sets of controls are provided and the driver is switching from one to the other. Providing that the driver makes contact again with the touch sensitive controls within the delay period the timing period will be reset to zero and the brake held off. Once the emergency brake has been applied a period of time must elapse before this can be cancelled.In other words, when the driver replaces his hand on the touch sensitive control a period of, say, six seconds will elapse before the deadman's handle application becomes cancelled. This is to prevent any momentary contact with the touch sensitive controls, by peop!e who may be rendering assistance to a driver who has become disabled, from accidentally cancelling the application of the brake.

The timing circuit may also operate to cause a third relay to operate for a predetermined period which in turn operates a solenoid valve to give an application of sand to facilitate braking on a wet rail. Two to three seconds after the emergency brake application has been initiated a fourth relay may be included to break the control circuit to the traction motor contacts, thereby removing power from the driving wheels. In the case of a diesel hydraulic locomotive this fourth relay would disengage the clutch via a solenoid valve to disconnect the power from the driving wheels.

However in the system described herein this function is performed by switch 1 OA.

In order to build a fail-safe factor into the sensing unit described with reference to Fig. 3 the amplifier sensing and timing circuits of Fig. 3131 are duplicated as shown in Fig. 3B2 but the amplifier 304 of the second, duplicate, channel has its polarity reversed as compared with that of the first channel. The contacts RA2 of coil 364 in the second channel are de-energised to close at the same time that the contacts RA1 of the similar coil 364 of the second channel are energised to close. The contacts RA1 and RA2 are shown in Figs. 3B1 and 3B2 in their de-energised condition.

On loss of signal the two relays change over causing the magnetic valve to become deenergised, the duplicate relay contacts being wired in such a way that if both relays do not change over simultaneously a deadman's application will occur. If due to a failure in either of the electronic channels or of the relays themselves, only one relay changes over, the deadman's application will occur and cannot be cancelled.

The duplicate channels will each be contained in separate screened boxes so that if either channel should go into self oscillation it will not affect the other.

In an alternative modified embodiment illustrated in Fig. 5, a reset pattern is incorporated in the control system so as to prevent or inhibit the locomotive driver from using the system as a lazy way to start and stop. The modification comprises a switch 1 OC which, when opened, prevents the 24v hold off supply being reapplied to EP valve 5.

The switch is opened by the pressure build up in the line between the electropneumatic valve 5 and the relay valve 4. The switch 1 OA closed, the build up is released, and the lock on produced by it removed, by pressing the reset button B1OC after the six second lapse before the deadman's handle application becomes cancelled.

The above described systems overcome the problem normally associated with such fail-safe braking arrangements that they encourage the driver to find a path round the safety arrangements. Not only is the system virtually impossible to substitute, but it also imposes little extra load on the driver additional to the normal requirement that he should keep hold of the driving controls It will be appreciated that the above embodiments have been described by way of example only and that many variations are possible without departing from the scope of the invention. For example, in the above described embodiment control switch 1 OB effectively acts to sense the application of the driver's straight air brake. In a modification this could be replaced by a touch sensitive control on the driver's straight air brake lever. These touch sensitive controls would be connected to segments T9-T1 0 of the connection strip. Again, control switch 1 OA senses an emergency deadman's application and opens the traction control circuit, having the same effect as switching off the pilot switch 13. The traction control circuit cannot be re-initiated without returning the power control levers to the minimum or idle position. This pressure switch 1 OA may be replaced by an additional relay, previously referred to as a "fourth relay", directly controlled by the electronics.

Claims (14)

1. A touch sensitive control comprising a touch plate and circuitry connected to the touch plate, the circuitry comprising filter means operative to pass signals entering at the touch plate to a detection circuit and the detection circuit being operative to detect signals so passed exceeding a predetermined magnitude and to produce a control signal in the event that such signals are detected.

2. A touch sensitive control as claimed in Claim 1, in which the filter means comprises one or more operational amplifiers, the or each amplifier having a tuneable feedback path comprising a capacitor and resistor in parallel.

3. A touch sensitive control as claimed in Claim 1 or Claim 2, in which the detection circuit comprises a diode and a variable resistor is provided to vary the threshold value of the circuit.

4. A touch sensitive control as claimed in Claims 1,2 or 3, in which the detection circuit comprises a light emitting diode operative to be switched on when a signal above the predetermined threshold level is present.

5. A touch sensitive control as claimed in any preceding claim, in which the detection circuit comprises an operational amplifier and a transistor which is operative to be switched on when a signal above the predetermined threshold level is present.

6. A touch sensitive control as claimed in Claim 5, in which the transistor is operable to control the flow of current through the coil of a relay, the contacts of which are disposed in a solenoid circuit which, when energised, holds a locomotive emergency brake off.

7. A touch sensitive control as claimed in Claims 5 or 6, in which a resistive-capacitive combination is connected to one input of the operational amplifier which maintains an input at the amplifier terminal for a predetermined time after the signal ceases to be detected.

8. A touch sensitive control as claimed in Claim 7, in which a variable resistor is provided for varying the predetermined time.

9. A touch sensitive control as claimed in Claim 7, in which the detection circuit comprises a second duplicate operational amplifier, resistivecapacitive combination, transistor and relay, the second, operational amplifier having an input connected with opposite phase to the first operational amplifier and the relays being connected such, that in normal operation, one is energised while the other is not, the arrangement being such that if, on loss of signal from the touch plate the relays do not change over simultaneously, a control signal is produced.

10. A touch sensitive control as claimed in any preceding claim, in which a signal generator is provided for the special generation of signals entering at the touch plate.

11. A touch sensitive control substantially as hereinbefore described with reference to the accompanying drawings.

12. A vehicle incorporating an emergency brake and a touch sensitive control as claimed in any preceding claim, the control being operative to cause actuation of the brake and disconnection of the propulsion mechanism from the driving wheels after a predetermined period after removal of the locomotive operator's hand from the control.

13. A method of operating a vehicle in which signals produced during operation of the vehicle are transmitted from an antenna in the vehicle via the vehicle driver tyo a touch sensitive control responsive only to those signals such that when the transmission link is broken by the driver removing his hand from the control a signal is preduced to cause actuation of an emergency brake on the vehicle, and disconnection of the propulsion mechanism from the driving wheels.

14. A method of operating a vehicle as claimed in Claim 13 in which the signals produced and transmitted are those produced by the driving gear of the vehicle.

1 5. A method of operating a vehicle as claimed in Claim 13 in which the signals produced and transmitted are produced by a signal generator special provided for the purpose.

1 6. A method of operating a vehicle substantially as hereinbefore described with reference to the accompanying drawings.