AU2002325670A1 - Turntable safety interlock system - Google Patents

Description

TURNTABLE SAFETY INTERLOCK SYSTEM

The invention relates to a turntable safety interlock system. In particular, although not exclusively, the invention relates to a turntable safety interlock system that ensures a trailer is properly coupled to the turntable before the trailer can be towed.

BACKGROUND TO THE INVENTION In the field of articulated trailers, such as trailers that are commonly used for road haulage, it is essential that the trailer is properly connected to the turntable, (also known as the fifth wheel). The turntable may be mounted on the prime mover or at the rear of a preceding trailer in a multiple trailer combination. Proper connection involves a skid plate of the trailer sitting down correctly on the turntable, which requires the trailer kingpin to be between the jaws of the turntable lock rather than, for example, the kingpin resting on the lockjaws. Proper connection also involves a turntable release handle being in a fully locked position such that the turntable lock fully engages the trailer kingpin ready for the trailer to be towed.

Numerous systems are commercially available which safeguard against the turntable release handle not being in a fully locked position. One such system working on this principle is disclosed in United States patent US 5,421 ,600 in the names of Jones, E. and Kane, J.E., wherein, if a latch mechanism on a trailer hitch is not properly closed, the brakes on the trailer are engaged to prevent the trailer from being towed. A warning device signals to the operator of the un-latched condition of the trailer hitch mechanism.

While US 5,421 ,600 addresses the problem of a lock for a trailer not being properly closed, this and other such systems do not indicate whether the trailer is sitting properly on the turntable. Such systems may give the false impression that a trailer is properly connected, providing the lock is fully closed, even though the trailer kingpin may be, for example, incorrectly and dangerously sitting on the jaws of the turntable lock.

Such systems comprising warning devices to indicate incorrect closure of the locking mechanism are also reliant on proper operation of the warning device. For example, a blown bulb in a warning light may prevent an operator from being alerted to incorrect closure of the locking mechanism.

Hence, there is a need for a system that ensures that a trailer kingpin is within the jaws of the turntable lock and thus sitting down correctly on the turntable and which also ensures that the turntable lock is fully engaged about the kingpin.

DISCLOSURE OF THE INVENTION In one form, although it need not be the only or indeed the broadest form, the invention resides in a turntable safety interlock system for coupling a trailer to a turntable, said system comprising: a fluid supply coupled via a fluid supply line to a first detection means and to a valve means; a second detection means coupled via said fluid supply line to said first detection means and to said valve means; said valve means coupled via said fluid supply line to a braking system of said trailer; wherein, upon detection by said first detection means of said trailer sitting correctly on said turntable and upon detection by said second detection means of a turntable lock being correctly closed, said valve means permits fluid flow to said braking system of said trailer.

The first detection means may be an actuator of a first limit switch and the second detection means may be an actuator of a second limit switch. The fluid may be air or may be hydraulic fluid. Accordingly, the braking system may be a pneumatic braking system or a hydraulic braking system.

The valve means may be a relay valve and in particular may be a spring loaded, high flow relay valve. Preferably, the second limit switch is coupled to a pilot section of the valve means, fluid flow through the pilot section permitting fluid flow through the valve means to the braking system.

Preferably, the first detection means is mounted as close as possible to a centre point of the turntable at a front of the turntable. The second detection means may be mounted adjacent a turntable lock release handle such that the second detection means detects when the release handle is in a fully locked position.

Alternatively, the second actuator may be mounted off a lock adjusting bolt of the turntable such that the second detection means detects when jaws of the turntable are fully closed. This may be when a locking yoke is fully home on either side of the jaws.

Suitably, the trailer is sitting correctly on the turntable when a trailer skid plate is in substantially full contact with the turntable.

Suitably, the turntable lock is correctly closed when jaws of the turntable lock are fully closed and are engaging a kingpin of the trailer.

BRIEF DESCRIPTION OF THE DRAWINGS To assist in understanding of the invention and to enable the invention to be put into practical effect, preferred embodiments will now be described by way of example only and with reference to the accompanying drawings, wherein:

FIG 1 is a schematic drawing of the turntable safety interlock system according to the present invention employed with a conventional trailer braking system; FIG 2 is a schematic drawing showing mounting positions of first and second detection means on a first type of turntable;

FIG 3 is a side view of the turntable in FIG3; and, FIG 4 is a schematic drawing showing mounting positions of first and second detection means on a second type of turntable.

DETAILED DESCRIPTION OF THE INVENTION The system of the present invention prevents a trailer being towed unless a trailer is properly and securely connected to a turntable of the trailer because the trailer brakes will be engaged. A brief summary of the braking system of conventional trailers will now be described.

With reference to FIG 1 , in general, the parking brakes of a modern trailer 2 utilise a spring activated mechanical system irrespective of whether the trailer 2 comprises disc or drum brakes. A separate spring brake combination service brake chamber 4 is mounted at each wheel position. Wheels have been omitted from FIG 1 for the sake of clarity. The brakes 4 are usually either pneumatically or hydraulically controlled and the braking fluid is communicated by supply line 6. This is a safe system in which, in the absence of air or hydraulic fluid that is required to release the brakes, the brakes are engaged, thus preventing movement of the trailer 2. However, without the system of the present invention it is still possible to move the trailer 2 when the trailer is not correctly coupled to the turntable of, for example, the prime mover, as described hereinbefore.

In a pneumatic system, the brakes 4 require approximately 450kPa air pressure in the trailer braking system in order to overcome the spring force and release the brakes. However, the air pressure value required to overcome the spring force varies between different sizes and models of trailer.

The trailer 2 is fitted with its own fluid tank 7 and its own spring brake relay valve 8. The relay valve 8 ensures that the brakes are activated and released quickly upon the supply of the necessary fluid pressure. The relay valve 8 also ensures that if there is a break or loss in the fluid supply line, the brakes are instantly activated.

The supply of fluid from a prime mover 12 is coupled to the trailer 2 via coupling means 9 and the supply is conventionally controlled by one of two commonly utilised systems. A first system is commonly used in the United States, which employs a dash-mounted tractor protection valve switch 14. When the driver/operator believes the trailer to be properly connected, 5 the switch 14 is depressed to enable its associated valve to allow the flow of fluid from a fluid supply 16 directly to the trailer 2.

A second system is commonly utilised in Europe and employs a trailer control combination valve (not shown), which automatically controls the supply of fluid from the fluid supply 16 to the trailer 2, without the need for o the driver to press a switch. The system of the present invention may be employed with either of these fluid supply control systems and, it is envisaged, with alternative fluid supply control systems.

The turntable safety interlock system of the present invention may be fitted in the air or hydraulic fluid supply line 6 between the prime mover 12 s and the trailer 2. However, the system is not limited to being fitted to the prime mover 12. For example, the system may alternatively be fitted to the rear of a first trailer in a double trailer arrangement or to the first and/or second trailers of a triple trailer combination. Fluid coupling means 9a is shown in FIG 1 for such a purpose. Indeed, the system of the present o invention may be fitted to any turntable in a combination of trailers providing the trailer being towed relies on air or hydraulic fluid to release the brakes of the trailer.

With reference to FIG 1 , the system comprises first and second limit switches 18 and 20 respectively, each of which includes a detection means in the form of an actuator. The limit switches may be, for example, % inch (0.635cm) mechanical over air roller/spring 3/2 valves as manufactured by Norgren, or other suitable valves. With reference to FIG 3, the actuator 22 of the first limit switch 18 detects whether a trailer skid plate 34 is sitting correctly on the turntable 24 rather than, for example, incorrectly resting with a kingpin 26 of the trailer on jaws 28 of the turntable lock. The turntable 24 pivots about a bushing 29 such that when the trailer is correctly coupled to the turntable, actuator 22 is activated. With reference to FIGS 2 and 4, an actuator 30 of the second limit switch 20 detects whether the jaws 28 of the turntable lock is fully engaged about the trailer kingpin 26. The system also comprises a spring loaded, high flow relay valve 10 that includes a pilot section 11.

When the system of the present invention is employed with the United States-type fluid supply system, fluid is supplied from a fluid supply 16, which may be located on the prime mover 12 as shown in FIG 1 , once the aforementioned dash-mounted tractor protection valve switch 14 is depressed by the driver/operator. In accordance with the invention, fluid is diverted from the supply line 6 at a point prior to the spring loaded, high flow relay valve 10 to the first limit switch 18. The relay valve 10 may be, for example, a fully pneumatic 1 inch (1.270cm) pilot/spring 3/2 valve as manufactured by Norgren, or any other suitable alternative known relay valve.

At the point in the supply line 6 where the fluid supply is diverted to the first limit switch 18, a pressure protection valve 32 is fitted that cuts the fluid supply to the first limit switch 18 in the event of a leak in the supply line. The pressure protection valve 32 is actuated when the pressure drops to, with reference to the above example, approximately 65 psi (approximately 445kPa) as a result of a leak. In order for fluid to pass through valves (not shown) of limit switches

18 and 20, naturally the limit switch valves must be open. For the first limit switch 18 to allow passage of fluid, the trailer skid plate 34 must be correctly seated on and in substantially full contact with the turntable 24, which requires that the trailer kingpin 26 is between the jaws 28 of the turntable lock. With reference to FIGS 2 and 4, for the second limit switch 20 to allow passage of fluid, a turntable locking release handle 36 must be in a fully locked position, which ensures that the lock jaws 28 are in a fully closed position and that the kingpin 26 is fully engaged by the lockjaws 28.

Hence, correct positioning of the trailer 2 on the turntable 24 is required before fluid may pass to the second limit switch 20. Once the trailer is correctly positioned, the jaws 28 of the turntable lock may be fully locked, thus allowing passage of fluid through a valve (not shown) of second limit switch 20. Fluid then feeds from the second limit switch 20 to a pilot section 11 of the relay valve 10. The pilot section operates/opens the relay valve 10 allowing fluid to flow from the supply line 6 to the braking system of the trailer 2 thus enabling release of the trailer brakes 4. The relay valve 10 will not allow the passage of fluid to the trailer brakes 4 unless the trailer is correctly positioned on the turntable 24 and correctly secured by the turntable jaws 28, as detected by actuators 22 and 30 respectively of limit switches 18 and 20. It is envisaged that the turntable safety interlock system may be used with any type of conventional turntable and is described below with reference to FIGS 2-4 fitted to two of the most commonly encountered turntable types - namely turntables manufactured by Jost and those manufactured by Holland. With reference to FIG 2 showing a Jost type turntable, the first limit switch 18, for ensuring that the trailer skid plate 34 is sitting correctly on and substantially in full contact with the turntable 24, is mounted as close as possible to a centre point of the turntable and at the front of the turntable. Its mounting position is such that when the trailer skid plate 34 is correctly mounted on the turntable 24, the actuator 22 of the first limit switch 18 is triggered and the valve of the first limit switch 18 opens to allow the passage of fluid therethrough. This may be achieved by any suitable/convenient mounting method in accordance with the specific type of limit switch employed. Regarding the second limit switch 20, which detects whether the locking jaws 28 are fully closed, with the Jost type turntable shown in FIG 2, the second limit switch 20 is mounted by any suitable means adjacent locking release handle 36 such that actuator 30 of the second limit switch 20 detects when the release handle 36 is in a fully locked position. In FIG 2, the release handle 36 is shown in an unlocked position causing the jaws 28 to be in an open position. Actuator 30 of second limit switch 20 detects locking of the release handle 36, which opens a valve in switch 20 to allow passage of fluid therethrough to the pilot section 11 of the relay valve 10, as shown in FIG 1. The pilot section operates/opens the relay valve 10 allowing fluid to flow to the braking system of the trailer 2 thus enabling release of the trailer brakes 4.

Many of the Jost turntables also feature a protected locking mechanism, which safeguards against the illusion of the jaws being locked, thus enhancing the reliability of the system of the present invention.

With a Holland type turntable, as shown in FIG 4, the first limit switch 18 is again mounted close to the centre of the turntable to enable the actuator 22 to detect when the trailer skid plate 34 is correctly sat on the turntable 14. The second limit switch 20 is mounted off a lock adjusting bolt 38 located at the front of the turntable 24. The actuator 30 of the second limit switch 20 is then only activated when a locking yoke is fully home on either side of the jaws 28. Once again, the jaws 28 in FIG 4 are shown in an open position because locking release handle 36 is shown in an unlocked position. If the system of the present invention was employed in, for example, a triple trailer combination and only the third trailer was incorrectly connected, the brakes would be released on the first and second trailers, but not on the third trailer, which would alert the driver that the third trailer was not properly connected. The driver/operator would be unable to tow the third trailer, which would prevent the triple trailer combination from being towed until all trailers are correctly and safely connected to their respective turntables.

Although the invention has been described in relation to articulated trailers that are utilised, for example, for road haulage, it is envisaged that the invention may also be utilised with railway rolling stock or the like wherein the correct hitching of rolling stock and the secure interlocking thereof is also of paramount importance. The invention may also be utilised with so-called bimodal semi-trailers, which may be transported over highways and the like or on railway lines. When such trailers are connected for use on railway lines, trailers are coupled to each other or to a railway bogie adapter. In either event, a coupling mechanism with which the present invention may be employed is provided.

It will be appreciated that the present invention is applicable to trailer systems employing either an air-powered braking system or a hydraulic braking system and the types of limit switches, valves and the like employed in such systems will be familiar to those skilled in the art.

Throughout the specification the aim has been to describe the invention without limiting the invention to any one embodiment or specific collection of features. Persons skilled in the relevant art may realize variations from the specific embodiments that will nonetheless fall within the scope of the invention.

Claims (16)

1 . A turntable safety interlock system for coupling a trailer to a turntable, said system comprising: a fluid supply coupled via a fluid supply line to a first detection means and to a valve means; a second detection means coupled via said fluid supply line to said first detection means and to said valve means; said valve means coupled via said fluid supply line to a braking system of said trailer; wherein, upon detection by said first detection means of said trailer sitting correctly on said turntable and upon detection by said second detection means of a turntable lock being correctly closed, said valve means permits fluid flow to said braking system of said trailer.

2. The turntable safety interlock system of claim 1 , wherein the first detection means is an actuator of a first limit switch.

3. The turntable safety interlock system of claim 1 , wherein the second detection means is an actuator of a second limit switch.

4. The turntable safety interlock system of claim 1 , wherein the fluid is air.

5. The turntable safety interlock system of claim 1 , wherein the fluid is hydraulic fluid.

6. The turntable safety interlock system of claim 1 , wherein the braking system is a pneumatic braking system.

7. The turntable safety interlock system of claim 1 , wherein the braking system is a hydraulic braking system.

8. The turntable safety interlock system of claim 1 , wherein the valve means is a relay valve.

9. The turntable safety interlock system of claim 8, wherein the relay valve is a spring loaded, high flow relay valve.

10. The turntable safety interlock system of claim 32, wherein the second limit switch is coupled to a pilot section of the valve means, fluid flow through the pilot section permitting fluid flow through the valve means to the braking system.

11. The turntable safety interlock system of claim 1 , wherein the first detection means is mounted as close as possible to a centre point of the turntable at the front of the turntable.

12. The turntable safety interlock system of claim 1 , wherein the second detection means is mounted adjacent a turntable lock release handle such that the second detection means detects when the release handle is in a fully locked position.

13. The turntable safety interlock system of claim 1 , wherein the second detection means is mounted off a lock adjusting bolt of the turntable such that the second detection means detects when jaws of the turntable are fully closed.

14. The turntable safety interlock system of claim 13, wherein the second detection means detects when a locking yoke is fully home on either side of the jaws.

15. The turntable safety interlock system of claim 1 , wherein the trailer is sitting correctly on the turntable when a trailer skid plate is in substantially full contact with the turntable.

16. The turntable safety interlock system of claim 1 , wherein the turntable lock is correctly closed when jaws of the turntable lock are fully closed around a kingpin of the trailer.

Dated this Fifth day of September 2002

DAXROSE PTY LTD

&

P & A MORGAN PTY LTD

By their Patent Attorneys FISHER ADAMS KELLY