Control of trailer brakes

Abstract

An antisway control system for a towed vehicle, having an actuator (20) for one or more hydraulically operated trailer wheels on the left and right sides of the towed vehicle (10), operated by a hydraulic pump via hydraulic flowlines (18, 19) capable of connecting the hydraulic pump to each hydraulically operated brake. A pair of electrically operated valves (22, 23) are capable of opening or closing one or other or both flowlines to a hydraulically operated brake, in response to a brake controller which can sense a sway condition and operate the left and right brakes alternatively to minimise or eliminate the sway condition, or in response to a braking signal from the towing vehicle.

Description

[0001] CONTROL OF TRAILER BRAKES

[0002] Field of the Invention

[0003] The invention relates to trailer brakes and control systems used in anti-sway systems and an actuator for use with such trailer brakes.

[0004] Background of Invention

[0005] There is a problem with existing trailer brakes used with anti-sway systems for trailers, and especially for larger trailers such as caravans.

[0006] Towed vehicles, such as trailers and in particular caravans, often face stability and braking issues. Because the wheels on a trailer need to be activated under a number of different conditions including (1) brake control from the towing vehicle to the trailer wheels, (2) emergency braking in a "breakaway condition" in which the towed vehicle becomes unhitched from the towing vehicle, and in some cases, (3) an antisway controller to operate the trailer brakes in the event of the detection of a sway event.

[0007] Previously these trailer brakes have been electrically operated drum brakes so that electrical signals can be sent direct to each brake. Whilst this allows for a fast response time when braking is required, electrically operated drum brakes are not suited to larger towed vehicles. They have various disadvantages as noted below.

[0008] There have been many attempts to prevent or minimise the sway of towed vehicles. Some systems use simultaneous braking of the wheels on both sides of the trailer when a sway event is detected, and some systems use asymmetric braking in which the wheels on one side of the trailer are braked and then released and the wheels on the other side the trader are then braked and released so that braking can occur alternately on each side of the trailer. An example of asymmetric braking with electrically operated drum brake is shown in Tuson AU 2014204434 Prior References:

[0009] All references, including any patents or patent applications cited in this specification are hereby incorporated by reference. No admission is made that any reference constitutes prior art. The discussion of the references states what their authors assert, and the applicants reserve the right to challenge the accuracy and pertinency of the cited documents. It will be clearly understood that, although a number of prior art publications may be referred to herein; this reference does not constitute an admission that any of these documents form part of the common general knowledge in the art, in New Zealand or in any other country.

[0010] Examples of various antisway systems are shown in the following Patents:

[0011] Bosch US 2011029210

[0012] Tuson AU 2014204434

[0013] Tuson AU 2016204948

[0014] AL-KO US 9168901

[0015] Lippert AU 2015287913

[0016] Each of these is incorporated herein by way of reference.

[0017] AL-KO in their patent specification make use of an accelerometer to detect unwanted sway of the towed vehicle. If angular deflection of the towed vehicle exceeds a predetermined threshold, then they apply the brakes on both sides of the towed vehicle.

[0018] The Lippert patent describes the use an angular rate detector system made up of a gyroscope and an accelerometer and applies brakes to both sides of the trailer in the event of a sway event.

[0019] The Tuson patents make use of a gyroscope to measure angular deflection of the towed vehicle and if this exceeds a preset threshold the controller then applies the electrically operated drum brakes alternatively to minimise or eliminate trailer sway. Our tests have shown that an alternate braking regime is more effective than other systems which apply the brakes simultaneously. Bosch also describe the use of asymmetric braking in response to a sway event.

[0020] All of these patents describe the use of electrically operated drum brakes.

[0021] HYDRAULICALLY OPERATED BRAKES:

[0022] The following are reasons why we consider hydraulically operated brakes (especially hydraulically operate disc brakes) are more advantageous for larger trailers with some form of anti-sway control, than electrically operated drum brakes.

[0023] Disadvantages of electric drum brakes and or integrated with anti-sway devices

[0024] 1. Old technology

[0025] 2. Overheating a common occurrence

[0026] 3. Brake fading, especially larger heavier caravans

[0027] 4. High magnet wear and drum damage

[0028] 5. Requires regular adjustment for brakes to be effective

[0029] 6. Requires regular maintenance

[0030] 7. Drum brakes are far heavier than disc brakes, contributing to higher un-sprung suspension load

[0031] 8. Not suitable for water use (river crossings / boat trailers / off road use)

[0032] 9. Collects harmful debris, sand / stones create higher wear and damage issues

[0033] Advantages of hydraulic disc brake technology

[0034] 1. Proven use in the automotive industry.

[0035] 2. Efficient and effective braking almost double that of electric drum braking.

[0036] 3. Minimum routine maintenance.

[0037] 4. No brake adjustment required as they are self-adjusting.

[0038] 5. Lightweight compared to drum brakes.

[0039] 6. Suitable for boat trailers and off-road use.

[0040] However, attempts to integrate hydraulically operated brakes, especially hydraulically operated disc brakes, with an antisway control system pose installation and operational challenges. Previous attempts to overcome the problem required two actuators. The disadvantages were cost; excessive amperage draw on the trailer battery and / or towing vehicle battery.

[0041] Definitions:

[0042] It is acknowledged that the term 'comprise' may, under varying jurisdictions, be attributed with either an exclusive or an inclusive meaning. For the purpose of this specification, and unless otherwise noted, the term 'comprise' shall have an inclusive meaning - i.e. that it will be taken to mean an inclusion of not only the listed components it directly references, but also other nonspecified components or elements. This rationale will also be used when the term 'comprised' or 'comprising' is used in relation to one or more steps in a method or process.

[0043] "Driver side" and "Passenger side" can be USED synonymously with right or left sides of the trailer, or vice-versa depending on the country.

[0044] OBJECT OF THE INVENTION

[0045] It is an object of the invention to provide a trailer brake control unit and a system of operating trailer brakes that ameliorates some of the disadvantages and limitations of the known art or at least provide the public with a useful choice.

[0046] SUMMARY OF INVENTION

[0047] In one aspect the invention provides an actuator for hydraulically operated trailer brakes, said actuator having a body, the body having an inlet port to receive pressurised fluid, at least two outlet ports, and a return path to a reservoir, each outlet port capable of being connected to a hydraulic line to a hydraulically operated brake on a trailer wheel, each port capable of being opened or closed by activation of an electrically operated valve, so that in use (a) activation of both valves will allow all outlet ports to be open and the return path to the reservoir to be closed to thereby direct hydraulic fluid to each brake, or (b) alternate operation of the valves will allow hydraulic fluid to be alternately directed to each brake or (c) when the valves are closed the return path to the reservoir is opened and the brakes are released.

[0048] Preferably the valves are solenoid operated valves.

[0049] Preferably said inlet port is connected to an electrically operated pump.

[0050] Alternatively said inlet port is supplied by hydraulic fluid pressurised by the release of compressed air acting on a piston to immediately supply pressurized hydraulic fluid to the inlet port.

[0051] Preferably the electrically operated pump is housed within the actuator body and is connected between a hydraulic reservoir and the inlet port.

[0052] Preferably a fluid reservoir is contained within the actuator body.

[0053] Preferably the actuator body includes a proportional valve for regulating pressure of the hydraulic output.

[0054] In another aspect the invention provides a trailer having an actuator of the above type connected to hydraulically operated brakes on either side of the trailer, an electrical controller for the actuator, and a battery connected to the controller and the electrically operated pump.

[0055] Preferably the controller can detect a sway event and send an electrical signal to the actuator to direct pressurised hydraulic fluid (a) to all brakes, or (b) allow hydraulic fluid to be alternately directed to the brake or brakes on each side of the trailer.

[0056] In another aspect the invention provides an antisway control system for a towed vehicle, such as trailers, caravans, or the like, having one or more trailer wheels on the left and right sides of the towed vehicle, comprising: a) Hydraulically operated brakes for use on each trailer wheel, b) An electrically operated hydraulic pump, c) Hydraulic flowlines capable of connecting the hydraulic pump to each hydraulically operated brake, d) Each hydraulic flowline having an electrically operated valve capable of opening or closing the flowline to a hydraulically operated brake, and e) A brake controller capable of electrically activating the hydraulic pump and / or one or more of the electrically operated valves.

[0057] Preferably the anti-sway control system includes an anti-sway controller capable of activating the hydraulic pump and or one or more of the electrically operated valves in both symmetric and asymmetric methods.

[0058] Preferably the anti-sway brake controller is programmed to turn ON the pump on detection of a sway event and to maintain the pump ON for about 20 seconds after the cessation of the sway event.

[0059] Preferably the electrically operated valves are solenoid-controlled valves.

[0060] Preferably the electrically operated pump and the solenoid-controlled valves are combined into one unit for ease of installation.

[0061] Preferably each brake is chosen from the group comprising hydraulically operated disc brakes or hydraulically operated drum brakes.

[0062] More preferably each brake is a hydraulically operated disc brake.

[0063] BRIEF DESCRIPTION

[0064] DRAWINGS

[0065] The invention will now be described, by way of example only, by reference to the accompanying drawings: Figure 1 shows an outline of a trailer and the hydraulic connections between the pump, the solenoid-controlled valves and the brake callipers (and a return line to a hydraulic reservoir).

[0066] Figure 2 shows a similar outline drawing but with the actuator body enlarged.

[0067] Figure 3 shows a cutaway side view through the actuator body.

[0068] Figure 4 shows a cutaway view on line D - D of figure 3, showing the 2 outlet ports in crosssection.

[0069] Figure 5 is a schematic hydraulic circuit diagram showing the different flow paths for the hydraulic fluid through the actuator and then to or from the brakes.

[0070] Figure 6 is a front elevation of the actuator showing the two external outlet ports.

[0071] Figure 7 is a front elevation of a solenoid cartridge valve, of the type used in this invention.

[0072] Figure 8 shows the internal flowlines in the actuator body 20, prior to insertion of the valve cartridges.

[0073] Figure 9 shows the electrical connections provided by a wiring loom on the trailer.

[0074] DESCRIPTION OF THE PREFERRED EMBODIMENT(S):

[0075] The following description will describe the invention in relation to preferred embodiments of the invention, namely an improved actuator for operating trailer brakes and its method of operation.

[0076] The invention is in no way limited to these preferred embodiments as they are purely to exemplify the invention only and that possible variations and modifications would be readily apparent without departing from the scope of the invention.

[0077] Overview of the preferred embodiment as shown in the drawings:

[0078] The present invention relates to an antisway control system designed for towed vehicles, including but not limited to trailers and caravans. The system is equipped with hydraulically operated disc brakes on each wheel of the towed vehicle and an electrically operated hydraulic pump. It further comprises hydraulic flowlines connecting the hydraulic pump to each hydraulically operated disc brake. Each hydraulic flowline is fitted with an electrically operated valve capable of opening or closing to control the flow of hydraulic fluid to the respective disc brake. Additionally, a brake controller 11 is provided, capable of activating the hydraulic pump and / or one or more of the electrically operated valves.

[0079] Electrical

[0080] Power for the electrically operated pump and valves is supplied by a dedicated battery (not shown). Which is preferably located on the towed vehicle. This battery is preferably a rechargeable battery, typically a lead acid battery, which is supplied by current from the vehicles alternator, so that it remains in a state of charge. This can be the main trailer battery (especially if the trailer is fitted out as a caravan with its own electrics) or a dedicated battery for the antisway control and activation.

[0081] For ease of installation a wiring loom can be provided capable of connecting the various components on the trailer and have provision for a multi-pin / socket connection to the towing vehicle. This wiring loom can include a power line from the towing vehicle to recharge the battery, and include a brake ON line from the towing vehicle.

[0082] The source of pressurised fluid is provided by a fast acting electrically operated pump 50. Alternatively, the pressurised fluid could be supplied by a source of compressed air acting on a suitable pump to pressurise the hydraulic fluid and activated by an electrically operated valve.

[0083] Preferably the pump is housed within the actuator body 20 and is connected to an internal reservoir within the actuator body 20.

[0084] In the case of an electrically operated pump, it is preferable that the electric motor is a brushless DC motor capable of fast activation coupled with a suitable hydraulic pump. An example is a mini cartridge pump. It may for example be an ironless brushless DC motor which is able to quickly reach operating speed.

[0085] Normally the electric motor will not be running and hence the hydraulic fluid will not be pressurised. However, if a sway event is detected or one of the other control or emergency states is sensed, such as activation of the brakes on the towing vehicle or a breakaway condition, then the electric motor turns on and quickly pressurises the hydraulic fluid. But "quickly" is a relative term, and there may be a slight lag in detecting a first sway event. To compensate for this, the system preferably has a built-in run-on time so that after detecting a sway event, the controller 11 keeps the pump on even though the trailer is no longer in a sway event. Preferably this pump on-time is of the order of 20 seconds after the end of a sway event. This allows the hydraulic fluid to remain in a pressurised state, so that if a subsequent sway event is detected, the brakes will be able to operate more quickly than the first sway event.

[0086] Optionally, there may be a manual override controlled from the towing vehicle to enable the driver to activate the pump in anticipation of future braking or sway events.

[0087] Optionally, there may also be an ABS electronic control unit 14 provided on the towed vehicle, as shown in figure 1. In this event the trailer needs to be equipped with additional wheel sensors 15 to detect wheelspin or wheel lock or other uncontrolled conditions, so that the status of the individual wheels can be sent to this ABS unit, and this can be used to provide an output to the actuator body 20 to control the braking to individual wheels (this may involve additional outlet ports or more likely additional valves on each of the hydraulic brakes or brake lines). Though in some cases this may be the braking of the wheels on one side of the vehicle. If such an optional ABS unit is to be provided on the trailer. It is most likely that this will be an off-the-shelf ABS controller 11 and off-the-shelf ABS sensors 15. But this is not the main purpose of the actuator body. It is simply that the actuator body 20 with its at least 2 outlet ports can be used in conjunction with an ABS control unit, although its main purpose is to provide for the safe control of hydraulically operated trailer brakes, and to allow for the possibility of asymmetric braking to minimise or prevent the uncontrolled sway of the towed vehicle.

[0088] The ABS sensors if fitted can detect the wheel spinning by any conventional means. For example, it could be by way of the rotor vents or a specially designed commutator ring on a disk hub. This system does not need to recognise speed only, and can provide various control signals to the ABS control unit 14. That ABS control unit 14 can then be used to activate the valves in the actuator body 20, and cause the brake pressure to be reduced (prevent lock-up) or modulated or increased as needed. Preferably the electrically operated pump has a rating of 1400-2000psi.

[0089] More preferably the two solenoids, the reservoir and the pump are packaged in one unit for ease of installation.

[0090] If a Tuson Electronic Sway Controller 11 (ESC) is use, we have found that the braking on-time per wheel needs to be increase compared to previous versions (previously used with electrically operated drum brakes).

[0091] The system is designed to detect undesirable trailer sway and send a signal to the brake controller 11, allowing it to take corrective action. In normal braking conditions, the hydraulically operated disc brakes can be activated simultaneously.

[0092] The system , which is integrated via a dedicated cable connection with the anti-sway device and makes use of a micro controller 11 circuit which activates the motor ON and also determines the direction of flow i.e. left or right solenoid valve (sometimes referred to in the drawings as driver-side or passenger-side hydraulic lines).

[0093] An additional flow pressure solenoid valve (total of 3 valves) determines the rate of flow pressure which in turn is determined by the number of volts released to the actuator generated by the anti-sway sensor. (Preferably this is a gyroscope as used in the Tuson sway controller 11, but the invention is not limited to a Tuson sway controller 11).

[0094] (In an anti-sway controller 11, the higher the g force detected, the higher the voltage, the harder the pressure is supplied to braking system).

[0095] This proportional braking is also adaptable for use with the factory supplied anti sway unit on a vehicle (tow vehicle) if wired through the brake control device. It works in both modes of symmetric braking for both braking and sway events as well as asymmetric in sway events.

[0096] Alternatively, the electrically operated valves can open or close as needed when the electrically operated pump is active, providing precise control over the braking force applied to the left and right sides of the towed vehicle.

[0097] This system makes use of multi valve technology, using solenoid valves to control flow for the control of hydraulic brakes. STATES:

[0098] Before considering the actuator in detail, the actuator has provision to provide a number of different states:

[0099] Port 1 is shown as physical port 22, and

[0100] Port 2 is shown as physical port 23.

[0101] If pump ON, then

[0102] If Both Ports 1 & 2 open = conventional braking on both sides of the trailer

[0103] If Port 1 OPEN - Port 2 CLOSED - left brake activated only - other wheel is free.

[0104] If Port 2 OPEN - Port 1 CLOSED - right brake activated only - other wheel is free.

[0105] Controller 11 switches activation of ports alternatively = asymmetric braking achieved.

[0106] If BOTH Ports CLOSED - no braking, and fluid pressure drops at the wheel brake cylinder as the internal return line is connected to the internal reservoir. This return line is switched OFF if either port is open, so all fluid pressure is applied direct to the relevant brake(s).

[0107] The master controller 11 can accept a braking signal from the towing vehicle (represented by the arrow 12) in which case the pump is immediately activated, and the solenoids are in the open valve positions to apply fluid pressure to each brake calliper.

[0108] If the sway senor detects an undesirable sway condition it can send an activation signal to the master controller 11 which in turn activates the pump (if not already on) and switches the solenoid-controlled valves on or off in a predetermined manner to alternately brake the left or the right wheels.

[0109] These states can best be understood by reference to figure 5, described below, which shows the hydraulic flowlines. Note that in figure 4, either or both hydraulic valves, 35, 36 can be operated by the solenoids 25, 26. Figure 3 helps to understand the operation of just one of these solenoid operated valves. With the prior art electric drum brake system, the speed at which electricity flows is far faster than that of hydraulic fluid. Existing sway controller are designed with a specific "on time" after activation of the sensor in a sway controller 11 detecting a sway event.

[0110] Allowing for the continued voltage to be supplied to the braking system for 0.75 seconds before deactivation from the sensor. Whilst this works with electric drum brakes the "on time" needed for disc braking would need to be on for a period of 1.0 - 1.2 seconds to achieve the same results.

[0111] For example, even with the hydraulic system fully blead, the actual process flow is as follows (in sway event) all this must happen in .75 sec

[0112] • Electrically turn on 12v motor from signal from the sway sensor 11

[0113] • Motor starts to load up pump 50 (builds up pressure)

[0114] • Brake lines reach pressure, hoses expand under load

[0115] • Brake calliper piston is pushed forward against brake pad rotor

[0116] • Build-up of desired pressure against the rotor to slow / brake the wheel speed

[0117] Given that the on time is 0.75 sec one can understand that whilst the process of hydraulic is fast there is more time needed to reach the desired outcome of at least 800 psi / wheel in a fastacting sway event, as typically hydraulic brakes operate best at a pressure of 1600 psi.

[0118] Figure 1

[0119] As shown in figure 1, there is an antisway sensor / controller 11 on the towed trailer 10, which is connected to the actuator body 20, the actuator body 20 being connected to or incorporating a source of pressurised hydraulic fluid and having at least two output ports each connected to hydraulic line to the brake or brakes on the wheels 17 on one side of the trailer. In this drawing, the towing vehicle is represented by arrow 10 A.

[0120] In this figure 1, these hydraulic lines 18, 19 are designated driver-side hydraulic line 18 (i.e. the right-hand side, in this Australian view, although it will be noted that the driver-side will vary from country to country), and the left-hand side hydraulic line 19 is designated the "passenger side hydraulic line". This drawing also shows an optional ABS electronic control unit 14 mentioned below. The anti-say sway sensor 11 is connected to the actuator by a pair of electrical wires 12,13. The reason for this is that the antisway sensor is designed for asymmetric braking, and sends a signal to activate either the left-hand side or right-hand side brakes.

[0121] The actuator body 20 is shown in more detail in figures 2, 3, 4 and 6.

[0122] Figure 2 shows the actuator body 20 having a pair of outlet ports 22, 23 , and a solenoid 25, 26 associated with each valve leading to an outlet port 42,43 to open or close the relevant hydraulic line. Note that in this drawing the right-hand side wheels are shown as operated by port 22 and the left hand side is operated by port 23. For the purpose of this specification is easier to describe the right-hand side wheels and flowline being relative to the direction of travel of the trailer, i.e. from left to right in figure 2. Normally the actuator and its associated battery will be installed on the trailer. However, it is possible to instal it on the towing vehicle and connect the actuator to the trailer brakes by suitable hydraulic lines.

[0123] Figure 3 shows the reservoir return line 30 to the internal reservoir 32 at top left of this this figure for one of the valves. (The output line from the reservoir to the inlet of the pump is not shown). Each valve can operate in the same way - either allowing pressurised fluid connection to the relevant hydraulic brake line (brake is ON) or the valve is de-energised and the brake is OFF with fluid pressure dropping to the reservoir level. See figure 5 for the hydraulic connections.

[0124] The actuator body 20 contains a pair of hydraulic valves 35, 36 , each of which is operated by a separate electrically operated solenoid 25, 26.

[0125] A suitable solenoid cartridge valve 25 Is shown in figure 7.

[0126] Figure 3 should also be considered in conjunction with figure 8. In figure 3, only one solenoid operated cartridge valve is visible, in order to illustrate the flow, either out of port 42 (connected to hydraulic flowline 18) or out of port 30 (leading to internal reservoir 32). The internal flowlines are better seen in figure 8, in which a cross-section of the body 20 shows a hole 80 leading to the proportional valve 51 in order to regulate the pressure of the hydraulic fluid applied to the brakes. Drilled into the body 20 are directional valve cavities 81 and 87. Each of these cavities can receive the solenoid cartridge valve of the type shown in figure 7. These directional valve cavities are configured in such a way as to allow the fluid to be directed through the valve to the brakes or back through the valve to the reservoir.

[0127] Figure 4 shows the two output valves 31, 32 (to the brake lines) and a proportional valve 35 to control the output pressure.

[0128] Figure 5 is a hydraulic circuit diagram.

[0129] Flow connections are shown schematically in Figure 5. In this example the pump 50 when ON draws fluid from the reservoir 32 and supplies it as pressurised hydraulic fluid to brakes on either side of the vehicle (to one or more braked wheels). The output fluid pressure is controlled by a proportional valve 51 to prevent over pressure damage to the hydraulic lines or the brakes.

[0130] In this figure the driver side "direction valve" 35 is ON allowing brake fluid to be directed to the driver side brakes 54. This directional valve is the solenoid-controlled valve inside the actuator body 20. On the other side of the drawing the passenger side direction Valve 36 is in the OFF position allowing fluid to return to the reservoir along line 19 (so the passenger side brakes are un-pressurised). One-way flow valves, 57, 58 prevent fluid from returning to the pump 50.

[0131] Figure 6 is a front elevation of the actuator showing the two external outlet ports 42, 43.

[0132] Figure 7 is a front elevation of a suitable cartridge valve body 25.

[0133] We have used an off-the-shelf solenoid cartridge valve, as shown in Figure 7, which allows three- way flow from two physical positions, available as Hydraforce cartridge valve SV08 - 33. It has ports, labelled 1, 2 and 3 and moves between 2 physical positions. The solenoid is operated by a 12 V DC coil, with a minimum pull in voltage of 10.2 V DC. When de-energised, the cartridge valve SV08 - 33 allows flow from port 3 to port 1, while at the same time blocking the flow at port 2. When energised, the cartridge's spool shifts to open the line from port 2 to port 1, while blocking flow out of port 3. We have found these cartridge valves to be particular suited to quickly open or close the hydraulic lines to the brakes, operating when under pressure from the pump. Full details of these valves can be found at hydraforce.com.

[0134] Figure 8 shows the internal flowlines in the actuator body 20, prior to insertion of the valve cartridges. The internal flowlines are shown in figure 8, in which a cross-section of the body 20 shows a hole 80 leading to the proportional valve 51 in order to regulate the pressure of the hydraulic fluid applied to the brakes.

[0135] Drilled into the body 20 are directional valve cavities 81 and 87. Each of these cavities can receive the solenoid cartridge valve of the type shown in figure 7.

[0136] These directional valve cavities are configured in such a way as to allow the fluid to be directed through the valve to the brakes or back through the valve to the reservoir. This is the key to isolating the brakes from each side while allowing depressurisation of the relevant brake line.

[0137] Hole 82 is drilled to allow for source pressure from the pump to the interior of the actuator and hence to the valves. Hole 86 is drilled and leads to the pump from the reservoir.

[0138] This drawing also shows plugs 83 and 84, which are there to allow the internal machining, and then the access holes for that machining to be blocked by suitable plugs 83 and 84. Another such plug is shown in figure 3, as plug 88.

[0139] Figure 9 shows the electrical connections provided by a wiring loom on the trailer.

[0140] The brakes on each side of the trailer are controlled by the actuator 106 as described above. There is a battery 102 mounted on the trailer 120 to supply power to the actuator. In this example the battery is a 12 volt lead / acid battery but other types of batteries can be used and the invention can be used with other voltages (preferably the same as the voltage used on the towing vehicle). Wire 100 shows the negative / earth wire to the battery 102. Wire 110 is the connection to the positive battery terminal. The battery can be used to power the breakaway switch and hydraulic actuator and the anti-sway controller.

[0141] There is a breakaway switch 101 having an input electrical wire from the battery and an output wire 104 to the hydraulic actuator 20 installed on the trailer 120.

[0142] Most basic models of breakaway switch only have 2 wires as shown; one wire would go to an output of the battery system (as shown) then in the event of separation from the tow vehicle this pulls a mechanism (not shown) that allows power from the switch to go to the hydraulic actuator via wire 104. The activator may be part of the typical trailer plug and socket arrangement 107 between the tow vehicle and the trailer, allowing the trailer to be disconnected from the tow vehicle when not in use but if it is disconnected as in a trailer breakaway situation then the breakaway switch is activated and an electrical signal is can be sent directly to the hydraulic actuator (as shown) via wire 104 to activate all brakes or indirectly via the antisway controller 106 to activate all brakes. The hydraulic actuator is the same as that shown in Figure 1 and the two output arrows in Figure 9 correspond to the hydraulic lines 18 and 19 of Figure 1 and shown in the hydraulic circuit of figure 5. The output of the anti-sway controller is via left and / or right wires 109 to the hydraulic actuator to activate the solenoid valves described above.

[0143] A separate circuit 105 is connectable to the tow vehicle 119 via the trailer plug and socket arrangement 107, this circuit 105 is connected at the other end to the asymmetric antisway controller 106 to allow the trailer brakes to be activated by the tow vehicle 119 when needed.

[0144] ADVANTAGES OF THE PREFERRED EMBODIMENTS:

[0145] This patent application outlines an innovative antisway control system that integrates hydraulically operated disc brakes with electrically operated valves and a brake controller 11. This system improves the braking performance and stability of towed vehicles, particularly large trailers and caravans, enhancing road safety and driver confidence allowing for much greater braking power than with conventional electrically operated drum brakes.

[0146] The preferred actuator has two external ports connectible to the hydraulic lines to the brakes on each side of the trailer, with an internal third passageway providing a return path for the hydraulic fluid to the internal reservoir, making installation easy.

[0147] This avoids the dollar cost and more importantly the additional energy cost of the use of two separate hydraulic actuators connected to the same power supply but each supplying braking to one side of the trailer, e.g. a caravan, on the left or right of the trailer. Amperage draw in braking applications is doubled considering each actuator could potentially be drawing 25amps to 40 amps each (depending on make and design) VARIATIONS

[0148] Hydraulically operated disc brakes are our preferred type of brakes for trailers in Australia but we recognise that in some markets there is a preference for drum brakes, especially in the North American market and our invention applies equally to hydraulically operated drum brakes.

[0149] Optional addition of an ABS for use in connection with the actuator unit.

[0150] Combination of a source of compressed air in combination with an electrically operated pump. This could be compressed air used for initial pressurisation, or a hybrid system in which the pump is used as needed to refresh the compressed air reservoir, and the source of compressed air is then used to quickly pressurise the hydraulic fluid entering the actuator body 20.

[0151] Whilst it is more practical (and safer) to mount the battery 102 on the trailer, it is possible that the controllers and electrically operated valves could be powered from the tow vehicle.

[0152] The simple breakaway switch could be replaced by a more complex breakaway switch as there are several types of switch on the market. This may necessitate changing the wiring diagram to accommodate a different breakaway switch.

[0153] It will of course be realised that while the foregoing has been given by way of illustrative example of this invention, all such and other modifications and variations thereto as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of this invention as is hereinbefore described.

Claims

CLAIMS:

1. An actuator for hydraulically operated trailer brakes, said actuator having a body, the body having an inlet port to receive pressurised hydraulic fluid, at least two outlet ports, and a return path to a reservoir, each outlet port capable of being connected to a hydraulic line to a hydraulically operated brake on a trailer wheel, each port capable of being opened or closed by activation of an electrically operated valve, so that in use (a) activation of both valves will allow all outlet ports to be open and the return path to the reservoir to be closed to thereby direct hydraulic fluid to each brake, or (b) alternate operation of the valves will allow hydraulic fluid to be alternately directed to each brake or (c) when the valves are closed the return path to the reservoir is opened and the brakes are released.

2. An actuator for hydraulically operated trailer brakes, as claimed in claim 1 wherein each electrically operated valve is a solenoid valve.

3. An actuator for hydraulically operated trailer brakes as claimed in claim 1 or 2, wherein said inlet port is connected to a hydraulic pump.

4. An actuator for hydraulically operated trailer brakes, as claimed in claim 3, wherein the source of pressurised hydraulic fluid is provided by a hydraulic pump connected to the actuator and the hydraulic pump is powered by an electric motor so that it is an electrically operated hydraulic pump.

5. An actuator for hydraulically operated trailer brakes as claimed in claim 3, wherein source of pressurised hydraulic fluid is provided by hydraulic fluid pressurised by the release of compressed air acting on a piston within the actuator to immediately supply pressurized hydraulic fluid to the inlet port.

6. An actuator for hydraulically operated trailer brakes as claimed in claim 4, wherein a reservoir and the electrically operated pump are housed within the actuator body and theelectrically operated hydraulic pump is connected between a hydraulic reservoir and the inlet port.

7. An actuator for hydraulically operated trailer brakes as claimed in any one of claims 1 to 6, wherein the actuator body includes a proportional valve for regulating pressure of the hydraulic output.

8. A trailer having an actuator as claimed in any one of claims 1 to 7 , connected to hydraulically operated brakes on either side of the trailer, an electrical controller for the actuator, and a battery connected to the controller and to the actuator.

9. A trailer as claimed in claim 8, wherein the controller can detect a sway event and send an electrical signal to the actuator to direct pressurised hydraulic fluid (a) to all brakes, or (b) allow hydraulic fluid to be alternately directed to the brake or brakes on each side of the trailer.

10. A trailer as claimed in claim 8 or 9, wherein the trailer also includes an anti-skid braking system capable of detecting and controlling skid events.

11. An antisway control system for a towed vehicle, such as trailers, caravans, or the like, having one or more trailer wheels on the left and right sides of the towed vehicle, comprising:• Hydraulically operated brakes for use on each trailer wheel,• A hydraulic pump,• Hydraulic flowlines capable of connecting the hydraulic pump to each hydraulically operated brake,• Each hydraulic flowline having an electrically operated valve capable of opening or closing the flowline to a hydraulically operated brake, and• A brake controller capable of electrically activating the hydraulic pump and / or one or more of the electrically operated valves in response to the detection of a sway condition.

12. An antisway control system for a towed vehicle as claimed in claim 11, wherein the hydraulic pump is powered by an electric motor.

13. An antisway control system for a towed vehicle as claimed in claim 11 or 12, further comprising a anti sway controller capable of activating the hydraulic pump and / or one or more of the electrically operated valves in both symmetric and asymmetric modes.

14. An antisway control system for a towed vehicle, as claimed in any one of claims 11 to 13, wherein the electrically operated valves are solenoid-controlled valves.

15. An antisway control system for a towed vehicle, as claimed in in any one of claims 11 to14, wherein the electrically operated pump and a pair of solenoid-controlled valves are combined into one unit for ease of installation.

16. An antisway control system for a towed vehicle, as claimed in in any one of claims 11 to15, wherein the brake controller is programmed to turn ON the pump on detection of a sway event and to maintain the pump ON for at least 20 seconds after the cessation of the sway event.

17. An antisway control system for a towed vehicle, as claimed in any one of claims 11 to 16, wherein each brake is chosen from the group comprising hydraulically operated disc brakes or hydraulically operated drum brakes.

18. An antisway control system for a towed vehicle, as claimed in claim 17, wherein each brake is a hydraulically operated disc brake.

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