Related Art Numerous types of vehicles employ what is called an"air parking brake". Simply put, an air parking brake system is comprised of three main parts: an air source, a valve and the air brake itself. When the valve is open, called a loading valve, air is supplied to the air brake, thereby releasing the air brake and allowing movement of the wheels of the vehicle.

When the valve is closed, air pressure is relieved from the air brake through an exhaust vent and the air brake engages, thereby inhibiting movement of the wheels of the vehicle.

An example of such an air parking brake system exists in commonly used commercial vehicles, such as trucks, commercial buses, or school buses. In such vehicles, an air compressor compresses air, which is stored in a reservoir or tank. This air is then directed to a loading valve through a supply hose and on to the parking brake mechanism through a delivery hose. This loading valve has a handle that extends from the dashboard of the vehicle, allowing the vehicle operator to"Pull To Apply"or"Push To Release"the parking brake.

"Pulling"the loading valve handle closes the loading valve, cutting off the air pressure coming from the reservoir or tank. Air pressure in the delivery hose (between the loading valve and the parking air brake) is released automatically through use of an exhaust vent built into the loading valve. When air pressure is absent from the air parking brake, brake springs hold the brake pads against the brake drum, thereby inhibiting the rotation of the vehicle's wheel (s).

"Pushing"the loading valve handle opens the loading valve, allowing air pressure to reach the air parking brake. When air pressure is applied to the air parking brake, the air

pressure overcomes the tension of the brake springs holding the brake pads on the brake drum, and the air parking brake is released, allowing rotation of the wheel.

A problem arises when an engaged air parking brake is accidentally released by bumping into the loading valve handle or through inadvertently"pushing"the loading valve handle. For instance, if a vehicle were to be parked on a hill and someone accidentally, inadvertently, or even intentionally disengaged the air parking brake, the vehicle could roll down the hill.

One patent shows an invention for keeping an air parking break from being accidentally, inadvertently, or intentionally disengaged. U. S. Patent No. 5,688,027 (Johnson) discloses a"control valve lock for a vehicle air brake system."Essentially, Johnson describes a box that locks over the top of the valve handle impeding the release of the parking break until the box is unlocked. Disadvantage of the Johnson invention are that the operator must take separate steps each time the brake is to be locked, through the use of the box and the additional key.

There are inventions for the automatic engagement of parking brakes upon the turning off of an ignition or engine key switch. U. S. Patent No. 5,624,352 (Smale) discloses an "ignition-controlled parking brake interlock."This lever and latch interlock invention is activated by turning off the vehicle ignition key. U. S. Patent No. 5,675,190 (Morita) discloses an"operating apparatus for parking brake and method for releasing parking brake." The Morita invention uses a combination of the vehicle ignition key switch, with ON-OFF positions and a three-way parking brake switch with ON-OFF-RESET positions to engage the parking brake. A drawback of the Morita invention is the complexity incumbent in the use of multiple switches.

Some vehicle anti-theft devices are designed to prevent brake disengagement by unauthorized persons. U. S. Patent No. 3,579,285 (Verdier) discloses such a system, entitled "hydraulic antitheft system for vehicles."The Verdier invention comprises an additional key operated switch, other than the ignition switch, which works to maintain fluid in the brake lines and subsequently pressure on the brakes. A disadvantage of Verdier is the use of an additional key. Another, U. S. Patent No. 3,174,502 (Howarth) discloses a"theft prevention apparatus."This apparatus employs a ignition switch which, when closed, engages a hydraulic brake system.

While inventions exist for the locking brakes in general, none combine ease of use and simplicity of manufacture/installation with both safety and theft deterrence.

SUMMARY OF THE INVENTION The present invention is an automatic air parking brake lock system that allows the operator to safely secure a vehicle employing air parking brakes in a way that eliminates accidental and inadvertent disengagement of the air parking brake, for example, by a passenger or a prankster. The lock system is electrically connected to the ignition key switch, so that the locking of the air parking brake becomes automatic upon turning the ignition to "OFF"position. The present invention has application in vehicles which employ air parking brakes, for example, school buses and other commercial passenger buses.

The major benefits of the present invention are safety and theft deterrence. By locking the air parking brake to prevent disengagement, it is less likely that a vehicle will be moved due accidental and/or incidental release of the parking brake while the ignition key switch is in the open or"OFF"position, for example, when the vehicle is parked and the driver is out of the vehicle and is helping to load or unload the vehicle. By operatively connecting the disengagement of the air parking brake to turning the vehicle's ignition key switch into the closed or"ON"position, the present invention helps prevent unauthorized persons from moving the vehicle.

The invented lock system comprises tying the operation of the ignition key to blocking of the parking brake air supply and to venting of the parking brake air pressure, in order to engage or maintain engagement of the parking brake. The preferred lock system comprises an air supply block and a vent for the air downstream of the air supply block, which are added to a conventional air parking brake system and which are actuated by turning off of the ignition switch. A single ignition key, therefore, turns off the engine, automatically engages the parking brake, and/or prevents disengagement of the brake when it has been pulled on by the driver. The block and vent are preferably accomplished by a single valving mechanism, such as a solenoid valve, but they may also be designed to be separate, cooperating valves, or may be incorporated in a single loading valve that cooperates with the ignition switch.

The preferred locking of the parking brake is done by placing a solenoid valve in-line between the existing air source and loading valve of the vehicle parking brake system. The preferred solenoid valve has an exhaust vent which may vent air pressure from the middle air hose running between the solenoid valve and the loading valve. The solenoid valve is wired into the ignition key switch so that, when the ignition key switch is turned to the open or "OFF"position, the solenoid valve is de-energized, which closes the solenoid valve to block

or"sever"the air supply to the loading valve and to vent the middle air hose. If the parking brake has not been engaged by the driver when the ignition is switched off (that is, the loading valve is open) the loading valve responds to the low upstream pressure, created by the solenoid, by"tripping"closed. When the loading valve closes, the air pressure in the delivery hose and in the air brake mechanism vents through the loading valve exhaust vent, causing the parking brake mechanism to then engage and inhibit movement of the wheel (s) of the vehicle. If the parking brake has already been engaged by the driver when the ignition is switched off (that is, the loading valve is closed) the parking brake cannot be disengaged by accidental or intentional pushing of the dashboard handle, because the air pressure supply to the loading valve is blocked by the solenoid valve. Thus, whether the hand-operated parking brake is"off'of"on"when the ignition is switched off, the invented lock system automatically establishes engagement, or maintains engagement, respectively, of the brake mechanism.

The present invention, unlike prior systems, is very easy to use. There need to be no additional locks (Johnson, Verdier), or switches to use (Morita) in order to lock the air parking brake. The present invention is also very simple to install and implement in a vehicle, unlike Howarth and Smale. The applicant envisions that the present invention may be packaged either as a modular retrofit unit which can be simply installed by the vehicle owner into existing vehicles.

BRIEF DESCRIPTION OF THE DRAWING', ; Fig. 1 is a schematic diagram view of one embodiment of the prior art showing an air parking brake system generally including: an air source, a loading valve, and an air parking brake mechanism. This figure shows the loading valve open, allowing air pressure to be supplied from the air source to the air parking brake mechanism, thereby disengaging the air parking brake.

Fig. 2 is a schematic diagram view of the prior art embodiment of Fig. 1. This figure shows the loading valve closed, severing the air pressure supply coming from the air source, the air pressure remaining in the air hose running from the loading valve to the air parking brake mechanism being allowed to vent through the loading valve's exhaust vent, thereby engaging the air parking brake.

Fig. 3 is a schematic diagram view of one embodiment of the present invention showing an air parking brake system generally including: an air source, a solenoid valve, a

loading valve, and an air parking brake mechanism. This figure shows the ignition switch closed, the solenoid valve open and the loading valve open (manual handle pushed inward).

This allows air pressure from the air source to reach the air parking brake mechanism, thereby disengaging the air parking brake.

Fig. 4 is a schematic diagram view of the embodiment of Fig. 3, showing the ignition switch open, the solenoid valve closed, and the loading valve closed (manual handle pulled outward). This severs the air pressure supply coming from the air source, causing the air pressure remaining in the middle air hose to vent through the solenoid valves's exhaust vent, and the pressure in the delivery hose, running from the loading valve to the air parking brake mechanism, to vent through the loading valve vent, thereby engaging the parking brake.

Fig. 5 is a schematic diagram view of the embodiment of Figs. 3 and 4, showing the ignition switch closed, the solenoid valve open, and the loading valve closed. This severs the air pressure supply coming to the loading valve, and causes the air pressure remaining in the delivery hose to the brake mechanism to vent through the loading valve's exhaust vent, thereby engaging the air parking brake.

Fig. 6 is a schematic top view of an installation kit according to one embodiment of the invention.

Fig 7 is a schematic diagram of a commercial vehicle brake system, indicating the location for installation of one embodiment of the invented lock system.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the aforementioned Figures 3-5, there is shown one, but not the only, embodiment of the invented automatic air parking brake system. The invented automatic air parking brake system is used to automatically engage the air parking brake of a vehicle upon the turning of the ignition key switch of the vehicle to the open or"OFF"position by the vehicle operator. The preferred embodiment of the present invention is an automatic air parking brake system, as shown in Figs. 3-5, including all of the specified aspects of the invention described herein and claimed below.

Fig. 1 and Fig. 2 depict one embodiment of the prior art. This prior art is the conventional apparatus and method currently used in commercial vehicles, such as school buses, for air parking brakes. In the prior art, see Fig. 1, an air source 2 such as an air reservoir or air compressor supplies air pressure to the air parking brake system. This air pressure is conventionally used for the vehicle's air parking brakes, as well as the vehicle's

air brakes in general. This air pressure is then routed through a supply air hose 4 to a loading valve 6. A delivery air hose 12 routes the air pressure from the loading valve 6 to the air parking brake mechanism 100. The loading valve 6 has an attached valve handle 8 which is mounted on the dash of the vehicle. When the valve handle 8 is"pushed"by the vehicle's operator into an inner position, the loading valve 6 is open. When the loading valve 6 is open, as in Fig. 1, air is allowed to pass through the supply air hose 4, through the open loading valve 6, through the delivery air hose 12, and into the air parking brake mechanism 100. Air pressure thus supplied to the air parking brake mechanism 100 overcomes the brake spring tension which holds the air parking brake pads 14 against the brake drum 16, thereby inhibiting movement of the vehicle's wheel (s). This release of the brake spring tension disengages the air parking brake mechanism 100 and allows for free movement of the vehicle's wheel (s).

In the prior art, when the valve handle 8 is"pulled"by the vehicle's operator into an outer position, the loading valve 6 is closed. When the loading valve 6 is closed, as in Fig. 2, the air source 2 is cut off and air pressure in the delivery air hose 12 and the air parking brake mechanism 100 is vented through an exhaust vent 10 located on the loading valve 6. This release of air pressure from the air parking brake mechanism 100 allows the brake springs located within the air parking brake mechanism 100 to retract. This forces the air parking brake pads 14 to press against the brake drum 16, thereby engaging the air parking brake mechanism 100 and inhibiting movement of the vehicle's wheel (s).

In the invented parking brake system 11, see Figures 3-5, an air source 2, such as an air reservoir or air compressor supplies air pressure to the invented air parking brake lock system 50. The air is routed from the air source 2 through a supply air hose 4 to a solenoid valve 20. A middle air hose 40 connects the solenoid valve 20 to a loading valve 6. The loading valve is then connected to the air parking brake mechanism 100 through the use of a delivery air hose 12. The solenoid valve 20 is electrically grounded through the use of a ground wire 24 in contact with a ground screw 36. The solenoid valve 20 is electrically connected to the vehicle's ignition key switch 30 through the use of a connection wire 26.

When the vehicle's ignition key switch 30 is closed or"ON", then the solenoid valve 20 is energized, actuating the solenoid valve 20 to an"open"position. When the vehicles ignition key switch 30 is open or"OFF", then the solenoid valve 20 is de-energized, making the solenoid valve 20"closed."The vehicle's ignition key switch 30 is ultimately connected to the vehicle's battery 32, which itself is grounded 34.

Fig. 3 shows the invented automatic air parking brake system 11 during normal driving with the parking brake off. The ignition key switch 30 is closed or"ON", thereby energizing and opening the solenoid valve 20. The manual parking brake handle 8 is pushed into an inner position on the dashboard 9, so that the loading valve is open. When in this configuration, air pressure is allowed to travel from the air source 2, through the supply air hose 4, through the open solenoid valve 20, through the middle air hose 40, through the open loading valve 6, through the delivery air hose 12, and to the air parking brake mechanism 100. Within the air parking brake mechanism, this air pressure overcomes the brake spring tension biasing the the air parking brake pads 14 towards the brake drum 16. Thus moving the pads 14 away from the brake drum 16 results in"disengagement"of the air parking brake, thereby allowing for free movement of the vehicle's wheel (s).

Fig. 4 shows the invented automatic air parking brake system 11 with its lock system 50 when the vehicle's ignition key switch 30 is open or"OFF", thereby de-energizing and closing the solenoid valve 20. When in this configuration, air pressure within the solenoid valve 20 and within the middle air hose 40 is vented through the solenoid valve exhaust vent 22. Air pressure within the loading valve 6, within the delivery air hose 12, and within the air parking brake mechanism 100 is vented through the loading valve exhaust vent 10 of the closed loading valve 6. This release of air pressure allows the brake mechanism 100 to "engage", that is, allowing the brake springs 15 to retract, thereby bringing and holding the brake pads 14 into contact with the brake drum 16 and inhibiting movement of the vehicle's wheel (s).

In Figure 4, the manual handle 8 is shown in the"pulled"outer position, and the loading valve is closed. This loading valve position may result from either of two cases. If the vehicle operator pulls the handle 8 before turning off the ignition switch, the loading valve closes and vents. Or, if the ignition switch is turned off first, the solenoid valve 20 lowers the pressure directly upstream (in middle hose 40) of the loading valve, and this lowering of pressure automatically"pops"or closes the loading valve. This is due to the loading valve being designed to be fail-safe by releasing pressure on the brake springs and thereby applying the parking brake in the event of an air source failure. Depending on the particular design, the loading valves are designed to automatically close when upstream pressure drops below about 60 psi, for example.

Fig. 5 shows the invented automatic air parking brake system 11 when the vehicle's ignition key switch 30 is closed or"on", so that the engine is running, but the parking brake is

engaged. The solenoid valve 20 is energized and open, pressurizing middle hose 40. The loading valve is closed, with the handle 8 in the"pulled"position. When in this configuration, air pressure within the loading valve 6, within the delivery air hose 12 and within the air parking brake mechanism 100 is vented through the loading valve exhaust vent 10. This release of air pressure engages the brake mechanism 100.

In Figure 5, the position of the loading valve may be for two reasons, both of which result in the safe condition of brake engagement. First, Figure 5 may represent the situation in which the vehicle has been restarted after being parked and turned off, and the engaged parking brake has not yet been released by pushing in the handle 8. Also, Figure 5 may represent the situation in which the operator is parked and idling the engine, but has purposely applied the parking brake by pulling out the handle 8. In either case, if the operator turns off the ignition switch, the lock system will go into the mode shown in Figure 4, in which the solenoid valve 20 maintains a low pressure upstream of the loading valve and maintains it in a closed position.

Use of the preferred embodiment allows the vehicle operator to automatically"lock" the parking break by turning the ignition key switch 30 of the vehicle to the open or"OFF" position. Being"locked"means that, no matter what position the parking brake dashboard handle is in, the vehicle's air parking brake cannot be disengaged until the ignition key switch 30 is moved out of the"OFF"position.

For example, the operator stops the vehicle, parks the vehicle on a hill and engages the air parking brake. When the operator turns the ignition key switch 30 to the"OFF" position, the air parking brake mechanism 100 will not be able to be disengaged until the ignition key switch 30 is moved again to the"ON"position. Therefore, while the key is in the"OFF"position, the air parking brake mechanism 100 will not be able to be accidentally and/or incidentally released by the"pushing"of the loading valve handle 8. If someone falls against the handle or a child or person pushes the handle, the situation is still safe.

If, on the other hand, the operator parks the vehicle and turns off the ignition, but does not pull the parking brake, the system 11 will automatically engage the parking brake, as in Fig. 4. The parking brake will remain engaged until the ignition switch is turned on and the handle 8 is pushed in.

A major benefit of this invention is safety: regardless of whether the vehicle operator remembered to"set"the air parking brake, the air parking brake is engaged automatically when the operator turns off the ignition key switch 30.

Another benefit of this invention is theft deterrence. By locking the air parking brake, the vehicle will not be able to be moved by a thief absent turning the ignition key switch 30 to the"ON"position.

The invented lock system 50 may be formed into a retrofit kit 60 for adaptation of existing air parking brake systems. The kit 60, shown schematically in Figure 6, may include a Horton brand 993281 solenoid valve 20, with its 3/64 inch diameter air passages and ports.

Other diameters of air passages and ports may also work well, for example, about 3/64-1/8 inch diameters, as long as they are preferably 3/64 or larger, in order to allow sufficient flow through the valve. Also, the kit 60 may contain 4-6 fittings 64, to connect the cut ends of the original supply hose to the solenoid, or to connect a new air hose 66 (or"line", supplied in the kit in about a 3 ft. length) to the solenoid, and/or to connect/reconnect the appropriate hoses to the loading valve. Also, the kit may contain two electrical wires 68, for grounding the solenoid and for connecting the solenoid to the switch circuit. Such a kit works well with the typical loading valve that is standard in many vehicle parking brake systems, such as the Bendix brand control valve No. 287238.

Such a kit 60 may work well to retrofit the lock system into an existing commercial vehicle, for example, those which have a brake diagram similar to that shown in Fig. 7. The location for insertion of the lock system solenoid valve 20 into the conventional parking brake system is marked in Fig. 7 with dashed lines. Such a kit 60 does not disrupt or lower the integrity of the main (driving) brake system, as it is installed in lines separate from the main system.

Alternatively, other switch systems may be wired to the solenoid valve to act as a safety lock. For example, a switch on a bus wheelchair lift may alternatively or additionally be wired to the solenoid, so that the brakes will automatically be engaged when the lift is used. Also, a switch on the bus door might be wired to the solenoid to engage the brake any time the door is open.

Although this invention has been described above with reference to particular means, materials and embodiments, it is to be understood that the invention is not limited to these disclosed particulars, but extends instead to all equivalents within the scope of the following claims.