AU2017268605A1 - Interlock and parking system - Google Patents

Abstract

The present invention relates to a pneumatic parking brake interlock system suitable for attachment to an existing vehicle parking system. The interlock system includes a logic processor operatively connected to (i) at least one sensor operable to generate a signal indicative of an unsafe condition, and (ii) a parking brake control valve, wherein the interlock issues an output signal to the parking brake control valve to automatically remove pressurised air from a parking brake in response to a signal input from the aforesaid sensor. - - 38 - O- 28 20 Fig. 2

Description

INTERLOCK AND PARKING SYSTEM

FIELD OF INVENTION [0001] The present invention relates to vehicles with pneumatic brake systems and more particularly, a pneumatic parking brake interlock.

[0002] It will be convenient to hereinafter describe the invention in relation to trucks having pneumatic brake systems, however it should be appreciated that the present invention is not so limited and can be used for other types of vehicles having pneumatic brake systems.

BACKGROUND ART [0003] It is to be appreciated that any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the present invention. Further, the discussion throughout this specification comes about due to the realisation of the inventor and/or the identification of certain related art problems by the inventor. Moreover, any discussion of material such as documents, devices, acts or knowledge in this specification is included to explain the context of the invention in terms of the inventor’s knowledge and experience and, accordingly, any such discussion should not be taken as an admission that any of the material forms part of the prior art base or the common general knowledge in the relevant art in Australia, or elsewhere, on or before the priority date of the disclosure and claims herein.

[0004] Interlocks are devices or mechanisms for coordinating the functions of different components in a system to avoid undesirable results. Interlocks often play an important role in safety applications in industrial processes by ensuring that the operation of one component automatically actuates or prevents operation of another component.

[0005] Many large vehicles such as buses and trucks have pneumatic brake systems. Pneumatic brake systems are particularly common in vehicles such as railway trains and semi-trailers that have multiple trailers or carriages which must be linked into the brake system. A pneumatic brake system fundamentally comprises a service brake in operative

2017268605 30 Nov 2017 connection with a foot control pedal, a parking brake which is set using a control lever or electronic actuator, and a compressed air storage tank with air lines that connect to the service brake and the parking brake.

[0006] The parking brake typically comprises a spring that urges a pair of callipers to squeeze a pair of pads against disc on the wheel axle, or urges a pad to press outwards on a cylindrical, drum-shaped part of the wheel axle. The parking brake is designed to keep the wheel axle stationary or set in the On' position by virtue of the spring pressure being applied to the pads.

[0007] Air pressure must be used to overcome the force of the spring in the parking brake. In contrast, air pressure is used to apply the service brake.

[0008] With respect to the service brakes, when an operator depresses the foot control pedal during driving to slow or stop the vehicle, air pressure decreases in the system, causing the brake pads to spread across brake drums, creating friction and slowing the rotation of the wheels. An air compressor refills the air storage tank with filtered air from the atmosphere and when the operator lifts their foot off the brake pedal, the air pressure in the system increases back to its original state.

[0009] When the vehicle engine is idling, or turned off, the operator's foot is no longer on the foot pedal so the service brake system is not being applied. The parking brake is normally applied to avoid the vehicle rolling. Setting of the parking brake operates valves that (a) close the path to the compressed air storage tank and (b) vent the pressurised air in the lines between the compressed air storage tank and the brakes, thus allowing the spring actuated parking brake to engage the disc or drum and resist wheel rotation.

[0010] One of the problems associated with this type of system is that it allows the operator, upon reaching a destination, to step out of the cabin without first setting the parking brake. Operators often deliberately leave their vehicle idling for convenience during short stops, or in order to minimise engine wear, conserve fuel, or power on-board auxiliary systems such as air conditioners. Operators may also unintentionally step out of the cabin without setting the part brake. Irrespective of the reason, if the park brake is not applied the vehicle may keep moving if it is in gear or on a slope.

2017268605 30 Nov 2017 [0011] Another problem is that the parking brake is set by operating a control lever or electronic actuator mounted on the dashboard or other panel in the vehicle cabin. The lever or actuator position can be altered if they are inadvertently knocked by an operator or passenger as they leave the vehicle cabin.

[0012] In the past, various hardware devices have been developed to address this problem. The hardware includes device such as industrial proximity switches however they need to be mounted in precarious positions, such as adjacent the vehicle tail shaft or wheels to monitor rotation speed. The environment under the chassis is less than ideal for obtaining reliable and accurate measurement and the device is usually vulnerable to damage in rugged areas such as building sites and mine benches.

[0013] Some other systems for automatic venting of the pneumatic system have been developed, but have proved unsuitable due to the risk that they could apply the brake inadvertently during normal driving or at speed.

[0014] US patent 8,480,183 (Morris et al) discloses a parking brake interlock that receives the parking brake air supply from a parking brake valve and exhausts the air supply if there is no service brake air pressure or if there is no ignition-on signal. The invention of US 2008/0224532 addresses the problem of accidental initiation of the parking brake by the operator or a passenger as the enter or leave the vehicle cabin.

[0015] US patent 9,381,895 (Smathers) relates to an air brake system having a control valve for the parking brake that vents air to apply the parking brake in the event of driver absence and/or open driver door.

[0016] US patent 6,758,298 (Eberling et al) discloses an interlock which automatically applies the pneumatically operated brakes of a bus during certain operator activities, such as, the operator leaving the driver seat, turning on flashing caution lights, or opening the bus door. The interlock includes a piston actuator positioned within the foot brake pedal and communicating with an auxiliary pressure line. The auxiliary line supplies pressure to the foot pedal and activates the parking brake in response to the driver leaving the seat or a door opening. The system of US 6,758,298 is stated as being suitable for integral

2017268605 30 Nov 2017 incorporation into original equipment manufacture (OEM) systems during vehicle assembly.

SUMMARY OF INVENTION [0017] An object of the present invention is to provide a pneumatic parking brake interlock that is suitable for retrofitting to existing vehicles (ie post-OEM).

[0018] Another object of the present invention is to provide improved safety for vehicles having pneumatic braking systems.

[0019] A further object of the present invention is to alleviate at least one disadvantage associated with the related art.

[0020] It is an object of the embodiments described herein to overcome or alleviate at least one of the above noted drawbacks of related art systems or to at least provide a useful alternative to related art systems.

[0021] In a first aspect of embodiments described herein there is provided a vehicle parking brake interlock system comprising:

- a compressed air tank for supplying pressurised air;

- a service brake connected to the compressed air tank via a service control valve and operable to apply braking pressure when the pressurised air is supplied thereto;

- a parking brake connected to the compressed air tank and operable to remove braking pressure when the pressurised air is supplied thereto;

- a parking control valve operable to control the supply of pressurised air to the parking brake and repositionable between an air supply position and an air venting position;

2017268605 30 Nov 2017 wherein the interlock includes a logic processor configured to control the parking brake control valve to automatically remove the pressurised air from the parking brake based upon at least one indication of operator absence.

[0022] In a second aspect of embodiments described herein there is provided a pneumatic parking brake interlock system that includes a logic processor operatively connected to:

(i) at least one sensor operable to generate a signal indicative of an unsafe condition, and (ii) a parking brake actuation mechanism, wherein the interlock issues an output signal to the parking brake actuation mechanism to automatically remove pressurised air from a parking brake in response to a signal input from the aforesaid sensor.

[0023] The logic processor may be in operative connection with two or more sensors, each capable of providing at least one input to the logic processor.

[0024] For example, one input to the logic processor may indicate operator absence. This input may be derived from a sensor that detects whether the operator seat is occupied or vacant. Another possible input to the logic processor may comprise a door status signal from a sensor that senses whether a door is open or closed. A possible third input to the logic processor may comprise a sensor that indicates whether the ignition is active or inactive.

[0025] The logic processor may use one input alone as indicative of an unsafe condition, or respond to a particular combination of sensor inputs. Typically, once the logic processor has detected an unsafe vehicle condition and set the parking brake, d will not allow the parking brake to be released by an operator until the unsafe condition is rectified.

[0026] In a third aspect of embodiments described herein there is provided a pneumatic parking brake interlock system that includes a logic processor operatively connected to;

2017268605 30 Nov 2017 (i) a first sensor operable to generate a first signal indicative of operator absence from a driving seat, a second sensor operable to generate a second signal indicative of a vehicle door being open, and (ii) a parking brake actuation mechanism, wherein the interlock issues an output signal to the parking brake actuation mechanism to automatically remove pressurised air from a parking brake in response to a signal input from both the first sensor and the second sensor.

[0027] Other sensors may provide inputs to the logic processor that are not associated with operator absence, but may indicate unsafe movement of the vehicle. For example, one such input may be a signal from a vehicle speed sensor such as a radar that measures the ground speed below the vehicle when it is moving in a forward or reverse direction. Once the vehicle exceeds 5 km/hr the interlock cannot apply the parking brake.

[0028] Typically, the parking brake interlock system includes a parking brake actuation mechanism comprising a TR3 inversion valve, in signal communication with a pilot air solenoid. The pilot air solenoid acts on the TR3 inversion valve which in turn shuts off air supply and vents the system aft of the TR3 inversion valve.

[0029] Typically, the parking brake actuation mechanism includes a solenoid valve connected to the regulated air source and operable to act on the TR3 inversion valve which in turn vents spring brake lines while shutting off the supply air. The park brake manual control (eg button or lever) must be repositioned to vent supply air before pilot air will be removed from the TR3 inversion valve.

[0030] A TR3 inversion valve is an air operated control valve. Unlike other valves, it is normally open. It is closed by using air pressure from another source. TR3 inversion valves are primarily used in emergency or parking brake systems and operate with air from a reservoir isolated by a check valve, from the air brake system. They can also be used in

2017268605 30 Nov 2017 interlocking and sequencing applications, where operations of components must take place in a specific sequence.

[0031 ] The interlock may include a bypass switch to disengage the interlock or disable one or more sensors. The interlock may also include relevant audible or visual alarms to indicate that the interlock is engaged or disengaged.

[0032] Preferably the present system is connected in parallel to the existing electrical system of the vehicle. For example, the sensors may be connected in parallel to the existing operator seat switch, door switch, and ignition. Other aspects of the system can be connected in parallel to the existing service braking system.

[0033] A method of modifying an existing original equipment manufacture pneumatic braking system of a vehicle comprising the step of connecting the parking brake interlock system of the present invention in parallel to the braking system.

[0034] Other aspects and preferred forms are disclosed in the specification and/or defined in the appended claims, forming a part of the description of the invention.

[0035] In essence, embodiments of the present invention stem from the realization that it is possible to create a modification by connection of an interlock in parallel with the existing vehicle pneumatic systems. The interlock uses the fact that air pressure must be used to apply a service brake and concomitantly release a parking brakes.

[0036] Advantages provided by the present invention comprise the following:

• can be fitted to vehicles as a post-OEM modification, • improves vehicle safety, • exhibits simple construction, installation and operation.

[0037] Further scope of applicability of embodiments of the present invention will become apparent from the detailed description given hereinafter. However, it should be

2017268605 30 Nov 2017 understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure herein will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS [0038] Further disclosure, objects, advantages and aspects of preferred and other embodiments of the present application may be better understood by those skilled in the relevant art by reference to the following description of embodiments taken in conjunction with the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the disclosure herein, and in which FIG. 1 illustrates the interlock system of the present invention.

DETAILED DESCRIPTION [0039] It is to be understood that the specific devices and processes illustrated in the attached drawing, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. Additionally, unless otherwise specified, it is to be understood that discussion of a particular feature of component extending in or along a given direction or the like does not mean that the feature or component follows a straight line or axis in such a direction or that it only extends in such direction or on such a plane without other directional components or deviations, unless otherwise specified.

[0040] In this specification:

FIG. 1 is a high level illustration of a pneumatic parking brake interlock system according to one embodiment of the present invention, and

FIG 2 is a more detailed illustration of a pneumatic parking brake interlock system according to one embodiment of the present invention.

2017268605 30 Nov 2017 [0041 ] Included within the area defined by the broken line are the major components of the OEM pneumatic brake system 21 including the compressed air tank 3, an air line passing to the service brake 7 and parking brake 9 and a solenoid 19 for control of air pressure in the air line. An operator normally uses a manual activator 1 in the form of a lever or actuator button located in the vehicle cabin.

[0042] The invention of the present system can be installed post-OEM and includes a logic processor 5 operatively connected to various sensors, each operable to generate a signal. Each signal alone, or in combination with one or more other sensors are indicative of an unsafe condition. These include a seat sensor 13 indicative of presence or absence of an operator, a door sensor 17 indicative of an open or closed condition of the operator door, a park brake sensor 15 indicative of the status (on or off) of the parking brake actuator, and a motion sensor 11 indicative of vehicle speed.

[0043] In the event of an unsafe condition, the logic processor 5 issues an output signal to the solenoid 19 to vent pressurised air from the air line. When the pressure is reduced in the air line, the spring in the parking brake 7 urges a pair of callipers to squeeze a pair of pads against disc on the wheel axle, or urges a pad to press outwards on a cylindrical, drum-shaped part of the wheel axle. This creates friction that resists rotation of the wheel axle.

[0044] In a particularly preferred embodiment the system of the present invention includes a safety feature to avoid unwanted application of the parking brake, particularly when the vehicle is being driven normally at speed. Specifically, once the vehicle has attained a speed of at least 5 km/hr, a velocity sensor issues a signal to isolate the electronic system of the interlock.

[0045] As a further safety feature, the interlock of the present invention preferably also includes a pressure protection valve in the air line. The pressure protection valve would typically be set at about 4 bar (400 KPa/ 58 psi). If the vehicle has an air leak and has been sitting for a time sufficient to drain the compressed air tanks, the operator typically enters the vehicle cabin and turns on the vehicle ignition to begin the process of re-filling the compressed air tanks. If the operator then exits the cabin, without setting the parking

2017268605 30 Nov 2017 brake, the interlock system will activate at 4 bar. Typically, the springs of the parking brake release at less than 6 bar, so the interlock will prevent the vehicle rolling away.

[0046] When the operator re-enters the cabin, they can manually set the parking brake, wait for a predetermined period of time, then release the parking brake again. This routine will re-set the interlock and the parking brake.

[0047] The system may include any useful software or hardware. For example, the system may include a global positioning system/global navigation satellite (GPS/GNSS) receiver and appropriate software to allow real-time tracking, geofencing and driver behaviour reporting. This feature may also be useful for communicating, recording and logging information such as time, date and location of the interlock when it performs a specific activity. Such information can be viewed using any basic web service such TelemetryHost™ software and the output saved and imported into Excel as a comma separated values (CSV) file, which allows data to be saved in a table structured format.

[0048] The system may also include appropriate interfaces such a modem to allow convenient communication including data upload (such as to a cloud back end), remote control and standard communication modes such as short message service (SMS) and email.

[0049] A suitable motion sensor may be provided, such as a K-band based radar module with signal-processing for precise distance measurement for stationary or slow moving objects. For example, an iSYS radar interface RS485 with a general purpose input/output (GPIO) would be suitable for automated or remote calibration and configuration of relevant parts of the system.

[0050] A suitable bus (such as an RS485 bus) may be provided to allow expansion to input/output devices such as display units or to interface with other pieces of hardware.

[0051] FIG. 2 is a more detailed illustration of a pneumatic parking brake interlock system according to one embodiment the present invention including the following components:

2017268605 30 Nov 2017

20	Logic processor	36	Velocity sensor (Radar based)
22	Door sensor	38	Air valve
24	N.C.(normally closed) switch on	40	Pressure reducing valve
	operator door (Circuit is open when
	the door is closed).
26	Seat sensor	42	Pilot line
28	N.O. (normally open) switch on	44	Pressure switch
	operator seat pad
30	Fuse (5 amp)	46	Parking brake manual activator
			(lever or button)
32	Vehicle battery	48	TR3 Inversion Valve
34	Optional sensor inputs (+/- switching	50	Compressed air tank
	to remain looped when not in use)
		52	Spring assisted parking brakes

[0052] The arrows in FIG. 2 indicate the direction of air flow.

[0053] While this invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification(s). This application is intended to cover any variations uses or adaptations of the invention following in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth.

[0054] As the present invention may be embodied in several forms without departing from the spirit of the essential characteristics of the invention, it should be understood that the above described embodiments are not to limit the present invention unless otherwise specified, but rather should be construed broadly within the spirit and scope of the invention as defined in the appended claims. The described embodiments are to be considered in all respects as illustrative only and not restrictive.

[0055] Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention and appended claims. Therefore, the specific embodiments are to be understood to be illustrative of the many ways in which the

2017268605 30 Nov 2017 principles of the present invention may be practiced. In the following claims, means-plusfunction clauses are intended to cover structures as performing the defined function and not only structural equivalents, but also equivalent structures.

[0056] It should also be noted that where a flowchart is used herein to demonstrate various aspects of the invention, it should not be construed to limit the present invention to any particular logic flow or logic implementation. The described logic may be partitioned into different logic blocks (e.g., programs, modules, functions, or subroutines) without changing the overall results or otherwise departing from the true scope of the invention. Often, logic elements may be added, modified, omitted, performed in a different order, or implemented using different logic constructs (e.g., logic gates, looping primitives, conditional logic, and other logic constructs) without changing the overall results or otherwise departing from the true scope of the invention.

[0057] Various embodiments of the invention may be embodied in many different forms, including computer program logic for use with a processor (e.g., a microprocessor, microcontroller, digital signal processor, or general purpose computer and for that matter, any commercial processor may be used to implement the embodiments of the invention either as a single processor, serial or parallel set of processors in the system and, as such, examples of commercial processors include, but are not limited to Merced™, Pentium™, Pentium II™, Xeon™, Celeron™, Pentium Pro™, Efficeon™, Athlon™, AMD™ and the like), programmable logic for use with a programmable logic device (e.g., a Field Programmable Gate Array (FPGA) or other PLD), discrete components, integrated circuitry (e.g., an Application Specific Integrated Circuit (ASIC)), or any other means including any combination thereof. In an exemplary embodiment of the present invention, predominantly all of the communication between users and the server is implemented as a set of computer program instructions that is converted into a computer executable form, stored as such in a computer readable medium, and executed by a microprocessor under the control of an operating system.

[0058] Computer program logic implementing all or part of the functionality where described herein may be embodied in various forms, including a source code form, a computer executable form, and various intermediate forms (e.g., forms generated by an assembler, compiler, linker, or locator). Source code may include a series of computer

2017268605 30 Nov 2017 program instructions implemented in any of various programming languages (e.g., an object code, an assembly language, or a high-level language such as Fortran, C, C++, JAVA, or HTML. Moreover, there are hundreds of available computer languages that may be used to implement embodiments of the invention, among the more common being Ada; Algol; APL; awk; Basic; C; C++; Conol; Delphi; Eiffel; Euphoria; Forth; Fortran; HTML; Icon; Java; Javascript; Lisp; Logo; Mathematica; MatLab; Miranda; Modula-2; Oberon; Pascal; Perl; PL/I; Prolog; Python; Rexx; SAS; Scheme; sed; Simula; Smalltalk; Snobol; SQL; Visual Basic; Visual C++; Linux and XML.) for use with various operating systems or operating environments. The source code may define and use various data structures and communication messages. The source code may be in a computer executable form (e.g., via an interpreter), or the source code may be converted (e.g., via a translator, assembler, or compiler) into a computer executable form.

[0059] The computer program may be fixed in any form (e.g., source code form, computer executable form, or an intermediate form) either permanently or transitorily in a tangible storage medium, such as a semiconductor memory device (e.g, a RAM, ROM, PROM, EEPROM, or Flash-Programmable RAM), a magnetic memory device (e.g., a diskette or fixed disk), an optical memory device (e.g., a CD-ROM or DVD-ROM), a PC card (e.g., PCMCIA card), or other memory device. The computer program may be fixed in any form in a signal that is transmittable to a computer using any of various communication technologies, including, but in no way limited to, analog technologies, digital technologies, optical technologies, wireless technologies (e.g., Bluetooth), networking technologies, and inter-networking technologies. The computer program may be distributed in any form as a removable storage medium with accompanying printed or electronic documentation (e.g., shrink wrapped software), preloaded with a computer system (e.g., on system ROM or fixed disk), or distributed from a server or electronic bulletin board over the communication system (e.g., the Internet or World Wide Web).

[0060] Hardware logic (including programmable logic for use with a programmable logic device) implementing all or part of the functionality where described herein may be designed using traditional manual methods, or may be designed, captured, simulated, or documented electronically using various tools, such as Computer Aided Design (CAD), a hardware description language (e.g., VHDL or AHDL), or a PLD programming language (e.g., PALASM, ABEL, or CUPL). Hardware logic may also be incorporated into display

2017268605 30 Nov 2017 screens for implementing embodiments of the invention and which may be segmented display screens, analogue display screens, digital display screens, CRTs, LED screens,

Plasma screens, liquid crystal diode screen, and the like.

[0061 ] Programmable logic may be fixed either permanently or transitorily in a tangible storage medium, such as a semiconductor memory device (e.g., a RAM, ROM, PROM, EEPROM, or Flash-Programmable RAM), a magnetic memory device (e.g., a diskette or fixed disk), an optical memory device (e.g., a CD-ROM or DVD-ROM), or other memory device. The programmable logic may be fixed in a signal that is transmittable to a computer using any of various communication technologies, including, but in no way limited to, analog technologies, digital technologies, optical technologies, wireless technologies (e.g., Bluetooth), networking technologies, and internetworking technologies. The programmable logic may be distributed as a removable storage medium with accompanying printed or electronic documentation (e.g., shrink wrapped software), preloaded with a computer system (e.g., on system ROM or fixed disk), or distributed from a server or electronic bulletin board over the communication system (e.g., the Internet or World Wide Web).

[0062] “Comprises/comprising” and “includes/including” when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. Thus, unless the context clearly requires otherwise, throughout the description and the claims, the words ‘comprise’, ‘comprising’, ‘includes’, ‘including’ and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

Claims (7)

1. A vehicle parking brake interlock system comprising:

- a compressed air tank for supplying pressurised air;

- a service brake connected to the compressed air tank via a service control valve and operable to apply braking pressure when the pressurised air is supplied thereto;

- a parking brake connected to the compressed air tank and operable to remove braking pressure when the pressurised air is supplied thereto;

- a parking control valve operable to control the supply of pressurised air to the parking brake and repositionable between an air supply position and an air venting position;

wherein the interlock includes a logic processor configured to control the parking brake control valve to automatically remove the pressurised air from the parking brake based upon at least one indication of an unsafe condition.

2. A pneumatic parking brake interlock system that includes a logic processor operatively connected to:

(i) at least one sensor operable to generate a signal indicative of an unsafe condition, and (ii) a parking brake actuation mechanism, wherein the interlock issues an output signal to the parking brake actuation mechanism to automatically remove pressurised air from a parking brake in response to a signal input from the aforesaid sensor.

3. A pneumatic parking brake interlock system according to claim 2 wherein the logic processor is operatively connected to:

2017268605 30 Nov 2017 (i) a first sensor operable to generate a first signal indicative of operator absence from a driving seat, a second sensor operable to generate a second signal indicative of a vehicle door being open, and (ii) a parking brake actuation mechanism, wherein the interlock issues an output signal to the parking actuation mechanism to automatically remove pressurised air from a parking brake in response to a signal input from both the first sensor and the second sensor.

4. The parking brake interlock system of claim 2 wherein the parking brake actuation mechanism comprises a TR3 inversion valve in signal communication with a pilot air solenoid valve and operable to place the parking brake control valve in an air venting position.

5. The parking brake interlock system of claim 4 wherein the actuation mechanism includes a solenoid valve connected to compressed regulated air source and operable to act on a TR3 inversion valve.

6. A vehicle parking brake interlock system comprising:

- a compressed air tank for supplying pressurised air;

- a service brake connected to the compressed air tank via a service control valve and operable to apply braking pressure when the pressurised air is supplied thereto;

- a parking brake connected to the compressed air tank and operable to remove braking pressure when the pressurised air is supplied thereto;

- a parking control valve operable to control the supply of pressurised air to the parking brake and repositionable between an air supply position and an air venting position;

2017268605 30 Nov 2017

- a logic processor operatively connected to;

(i) at least one sensor operable to generate a signal indicative of an unsafe condition, and (ii) a parking brake actuation mechanism, wherein the interlock issues an output signal to the parking brake actuation mechanism to automatically remove pressurised air from a parking brake in response to a signal input from the aforesaid sensor.

7. A method of modifying an existing original equipment manufacture pneumatic braking system of a vehicle comprising the step of connecting the parking brake interlock system of claim 2 in parallel to the braking system.