The present invention relates to a suspension system for a hitch and in particular to a suspension system for a trailer hitch.

In any towing arrangement, there exists the potential that forces from the towed apparatus are transferred into the towing vehicle. These forces can not only make the towing vehicle more uncomfortable to drive, but can actually be dangerous as sudden transfer of forces can cause a driver to lose control, in addition, the forces transferred from the towed apparatus are unpredictable and often sudden, making it impossible for the driver of the towing vehicle to rely on caution alone or assume that they can compensate for these transfers of forces as they arise. Moreover, the transfer of these forces can reduce the operational capability of the towing vehicle, causing the operator to operate at lower speeds in order to better manage the unpredictable forces that can affect the level of control he/she has over the towing vehicle. The forces transferred are partly dependant on the weight of the towed apparatus and as a result, the heavier the load, the greater the forces that will be transferred to the towing vehicle.

Additionally, the constant transfer of shock forces from the towed apparatus to the towing vehicle can cause fatigue of the mechanical components over time, resulting in possible ultimate failure of these components. Again, this problem intensifies as the weight of the towed apparatus and towing vehicle is increased and critical components experience significant loading during operation. The shock loading and associated fatigue not only affects the mechanical components, but can be transferred to many of the components of the towing vehicle and such loading can even manifest itself in additional tire wear or higher fuel consumption as the towing vehicle works to fight the forces transferred from the towed apparatus. Furthermore, it is a legal requirement that drivers of vehicles are not subjected to ongoing whole body vibrations for health considerations so there is a desire to reduce the vibrational forces transferred through the towing linkages to reduce this vibrational effect. It is an object of the present invention to obviate or mitigate the problem of forces transferred from a towed apparatus affecting the comfort, health and safety of an operator of the attached towing vehicle, and the effect of such transferred forces on the longevity of the component parts of both the towed apparatus and the towing vehicle.

Accordingly, the present invention provides a suspension system for a towing hitch of a vehicle for reducing the impact of forces transferred from a towed apparatus to a towing vehicle during operation, the towing hitch being movably mountabie on the towing vehicle, the suspension system comprising at least one damping means connectable at a first end to the towing vehicle and connected at a second end to the towing hitch so as to dampen relative movement between a hitch end of the towing hitch and the towing vehicle.

Ideally, the towing hitch is movably mountabie directly or indirectly on the towing vehicle.

Preferably, the towing hitch comprises any one of a tow ball, tow pin or piton and jaw, towing bar and ball and spoon arrangement. By towing hitch we mean any means for engaging a corresponding part of an apparatus to be towed.

Preferably, the damping means has a fluid circuit.

Ideally, the suspension system has a control system in operable engagement with the fluid circuit of the damping means for adjustable control of the damping means, the control system having a means for detecting a trigger load for activating the adjustable control of the damping means.

Ideally, the fluid circuit is a hydraulic circuit.

Advantageously, the control system automatically detects the presence of forces acting on the damping means in an upward or downward direction and manipulates fluid within the suspension system to dampen the forces experienced by the towing vehicle in the required direction. The manipulation of the fluid is dependent on the level and direction of the load experienced. Furthermore, the incorporation of the suspension system between the towing vehicle and the towed apparatus allows the vehicle to travel at greater speeds and therefore improves the productivity of the towing vehicle. An unexpected advantage of the present invention which has been discovered during testing is that the overall braking performance of the combined towing vehicle and towed apparatus is improved when the suspension system is engaged.

Ideally, the towing hitch is movab!y mountable on the towing vehicle for allowing generally vertical and/or horizontal movement of the hitch.

Preferably, the towing hitch is pivotaliy mountable on the towing vehicle.

Ideally, the towing hitch is movab!y mountable on the suspension system.

Preferably, the towing hitch is mounted on the damping means.

Ideally, the towing hitch is mounted on at least one actuating arm of the damping means.

Preferably, the towing hitch has an associated locking means.

Ideally, the locking means has a biasing means for biasing the locking means into a locking position under normal conditions. Advantageously, the biasing means ensures that the locking means is maintained in a position relative to the towing hitch for securely retaining a connector portion of the towed vehicle on the towing hitch during use.

Preferably, the locking means comprises a spring loaded lock keeper member normally protruding across the space of a towing hitch formed for receiving a towing ring or similar coupling means of a towed vehicle.

Ideally, the suspension system has a vehicle attachment means.

Preferably, the vehicle attachment means is a generally quadrangular attachment means.

Ideally, the generally quadrangular shape of the vehicle attachment means defines a generally quadrangular cavity thereunder.

Preferably, the suspension system has a drop base movab!y mounted thereto.

Preferably, the drop base is a generally quadrangular member.

Ideally, the drop base is an elongated tubular quadrangular member having an internal channel.

Ideally, the towing hitch and locking means are locatable on the drop base. Preferably, the drop base Is rotatabiy coupled to the suspension system at an end distal the end having the towing hitch thereon.

Ideally, the drop base is movably coupled to the vehicle attachment means.

Ideally, the drop base is rotatabiy coupled to the vehicle attachment means at an end distal the end having the towing hitch thereon.

Ideally, the drop base is formed such that it is insertabie into the cavity under the vehicle attachment means.

Preferably, the towing hitch and locking means are mountable on the drop base such that the towing hitch and/or locking means are movable relative to each other.

Advantageously, as the towing hitch and lock means are mountable on the drop base and move together as the drop base is moved, the towing ring or similar coupling means of a towed vehicle cannot become wedged beneath the locking means or suspension system as the drop base is moved towards the suspension system.

Ideally, the towing hitch is movable relative to the locking means.

Preferably, the towing hitch is movable relative to the drop base.

Ideally, the locking means is movable relative to the drop base.

Ideally, the towing hitch is slidably mountable to the drop base.

Preferably, the towing hitch has a drop base mounting means.

Ideally, the drop base mounting means is a generally quadrangular mounting means. Ideally, the drop base mounting means is insertabie into the channel of the drop base.

Advantageously, the channel of the drop base is formed for guiding the motion of the towing hitch.

Preferably, the drop base mounting means is siidabie within the channel of the drop base.

Ideally, the locking means is locatable on a surface of the drop base defining the channel thereof. Preferably, the locking means is locaiable on the same surface of the drop base proximal to the towing hitch.

Advantageously, the towing hitch can be moved away from the locking means to allow engagement with a towing ring or similar coupling means of a towed vehicle, and subsequently moved towards the locking means to secure the towing ring or similar coupling means of a towed vehicle for towing.

Further advantageously, as there is no relative vertical movement between the towing hitch and the locking means, there is no risk that the towing ring or similar coupling means of a towed vehicle will become wedged between the drop base and the suspension system.

Ideally, the control system has a load compensation means for the compensation of minor loads and a load compensation means, preferably separate, for the compensation of major loads.

Ideally, the detecting means comprises a sensor.

Preferably, the sensor is a pressure or flow rate sensor in fluid communication with the circuit.

Ideally, the control system comprises an electronic control unit in operable engagement with the sensor and a means for supplying fluid to the circuit.

Ideally, the means for supplying fluid is a pump.

Preferably, the control system acts as the load compensation means for the compensation of major loads.

Preferably, the pump is in fluid communication with a reservoir of the circuit.

Preferably, a control valve block is operably engaged with the fluid circuit.

Ideally, the control valve block is designed to handle flow rates in the range of 0 to 200 litres per minute.

Preferably, the means for supplying fluid is capable of supplying the barrel end of the cylinder with fluid.

Ideally, the means for supplying fluid is capable of supplying the annuius end of the cylinder with fluid. Preferably, the electronic control unit has a software control program executable thereon.

Ideally, the software control program has a module with means for generating control signals to the power supply of the pump for controlling the flow of fluid to each end of the cylinder in response to signals from the detecting means.

Advantageously, when a large downward load is experienced by the damping means of the suspension system, this is detected by the sensing means and as a result, the electronic control unit commands the means for supplying fluid to provide additional fluid to the barrel end of the cylinder, providing the necessary damping effect. When a large upward load is experienced by the damping means of the suspension system, this is detected by the sensing means and as a result, the electronic control unit commands the means for supplying fluid to provide additional fluid to the annulus end of the cylinder, providing the necessary damping effect.

Further advantageously, after the load has been detected and the fluid provided to the correct end of the cylinder, the sensing means continues to monitor the fluid pressures and, if necessary, fluid can be provided to the end of the cylinder opposite the end that received the initial infusion of fluid to further balance the system and provide the ongoing desired damping effect.

Ideally, when the loads experienced by the damping means of the suspension system are relatively low, load compensation means for the compensation of minor loads provides the damping effect.

Preferably, the load compensation means for the compensation of minor loads comprises the piston and cylinder arrangement and/or an accumulator operably coupled to the fluid circuit.

Advantageously, in the event of minor loads no assistance or fluid balancing is provided by the electronic control unit.

Advantageously, where the loads experienced by the apparatus are low, the absorption and damping is provided by the existing fluid within the cylinder and/or the accumulator, in this case, the sensing means stili detects the ievei but the electronic control unit does not take any action as the measured value does not reach the trigger value.

Ideally, the electronic control unit is in operable engagement with a system status display means,

Preferably, the electronic control unit transfers information to the system status display means via a wired connection.

Preferably, the electronic control unit transfers information to the system status display means via a wireless connection.

Preferably, the system status display means is a visual display unit.

ideally, the visual display unit is iocatabie within easy viewing distance of a driver of the towing vehicle.

Preferably, the output of the sensing means is used to form the basis of a status display on the system status display means.

Advantageously, the driver of the towing vehicle can monitor the operating conditions of the suspension system during use.

ideally, sensing means utilized to display information on the visual display unit comprise pressure, temperature, and/or flow rate sensing means.

Ideally, the damping means are designed to absorb generally vertical and/or horizontal forces.

Preferably, the damping cylinder has at least one sensing means for sensing measurable parameters of the fluid.

ideally, the at least one sensing means is Iocatabie within the damping cylinder. Preferably, the at least one sensing means is Iocatabie at or about the end of the cylinder distal the annulus end.

Ideally, the at least one sensing means is a pressure sensor.

Preferably, more than one pressure sensor is provided.

Advantageously, the pressure sensors can measure the pressure of the fluid at different points within the cylinder. Preferably, additional sensing means are provided for sensing flow rate and temperature of the fluid.

Ideally, the sensing means are in operable engagement with an electronic control unit.

Preferably, the sensing means has means for generating an output signal.

Ideally, the software control program has a module for receiving output signals from the sensing means for identifying information representing the operating conditions in the fluid.

Preferably, the output signal of the sensing means is transferred to the means for receiving the output signal of the sensing means via a wired connection.

Alternatively, the output signal of the sensing means is transferred to the means for receiving the output signal of the sensing means via a wireless connection.

Preferably, the damping means comprises a damping cylinder.

Preferably, the damping means comprises a dual action damping cylinder.

Ideally, the damping means comprises a fluid damping cylinder.

Preferably, the damping means comprises a hydraulic damping cylinder.

Ideally, the suspension system comprises more than one damping means.

Preferably, the suspension system comprises two damping means.

Ideally, the damping means comprises a cylinder and a piston.

Preferably, the damping means comprises two or more cylinders.

Preferably, the piston is movably attachable at a first end to the towing vehicle or intermediate component thereof.

Ideally, the piston is pivotably attachable at a first end to the towing vehicle or intermediate component thereof.

Alternatively, the piston is movably attachable to the towing hitch.

Ideally, the piston is movably attachable at a first end to a back plate of the towing hitch. Preferably, the back plate of the towing hitch is movably attachable to the towing vehicle or an intermediate component thereof.

ideally, the damping means comprises a cylinder.

Ideally, an annulus end of the cylinder provides an opening for receiving a shaft of the piston.

Preferably, the piston comprises a head and a shaft.

Ideally, the head of the piston is slidably mounted within the cylinder at a second end of the shaft.

Preferably, the head of the piston creates two isolated chambers within the cylinder. Ideally, each chamber has fluid, preferably hydraulic therein.

Preferably, the cylinder has a barrel end distal the annulus end, which is movably attachable to the towing hitch or intermediate component thereof.

Ideally, the cylinder is pivotably attachable to the towing vehicle or an intermediate component thereof.

Preferably, the intermediate component is a suspension mount frame.

Ideally, the suspension mount frame is fixably attachable to the towing apparatus. Alternatively, the cylinder is movably attachable to the towing hitch or intermediate component thereof.

Ideally, the damping means comprises a shock absorption means.

Preferably, the shock absorption means comprises a mechanical shock absorber.

Ideally, the mechanical shock absorber comprises a spring.

The invention will now be described with reference to the accompanying drawings which show by way of example only one embodiment of a suspension system for a towing hitch of a vehicle in accordance with the invention.

Figure 1 is a schematic view of a hydraulic circuit and control system;

Figure 2 is a side view of the suspension system for a towing hitch attached to the towing vehicle and the towing hitch ; Figure 3 is a disassembled view showing the damping members and the attachment frames;

Figure 4 is a perspective view of one damping member in operable engagement with the towing hitch and the towing vehicle;

Figure 5 is a side view of a second embodiment of suspension system for a towing hitch ;

Figure 6 is a third embodiment of suspension system in accordance with the invention;

Figure 7 is a perspective view of a fourth embodiment of the suspension system wherein the towing hitch has a corresponding locking means for a towing ring;

Figure 8 is a perspective view of a fourth embodiment of the suspension system wherein the towing hitch has a corresponding locking means for a towing bail fitting;

Figure 9 is a perspective view of a fourth embodiment of the suspension system wherein the towing hitch is a towing bar;

Figure 1 0 is a perspective view of a fifth embodiment of the suspension system wherein the towing hitch is slidably movable with respect to the locking means and showing the towing hitch and the drop base in a retracted position ;

Figure 1 1 is a perspective view of a fifth embodiment of the suspension system wherein the towing hitch is slidably movable with respect to the locking means and showing the towing hitch in a retracted position and drop base in a lowered position; and

Figure 1 2 is a perspective view of a fifth embodiment of the suspension system wherein the towing hitch is slidably movable with respect to the locking means and showing the towing hitch in an extended position and the drop base in a lowered position.

In the drawings, there is shown a suspension system for a towing hitch indicated generally by the reference numeral 1 for reducing the impact of forces transferred from a towed apparatus to a towing vehicle during operation. The suspension system 1 has two damping members 2 connectab!e at a first end 3 to the towing hitch 33, and connected at a second end 4 to the towing apparatus 31 . The suspension system 1 has a control system 5 (see Figure 1 ) in operable engagement with a circuit 32 of the system 1 for adjustably controlling the damping members 2. The control system 5 has a sensor 8 for detecting a trigger value for activating adjustable control of the damping member 2.

The sensor 6 automatically detects the presence of forces acting on the hitch 33 in an upward or downward direction and signals the control system 5 to manipulate the fluid 7 within the suspension system 1 to dampen the forces experienced by the towing vehicle 31 in the required direction. The manipulation of the fluid 7 is dependent on the level and direction of the load experienced by the hitch 33.

The sensor 6 is in fluid communication with the circuit 32 and the control system 5 comprises an electronic control unit 8 operably engaged with the sensor 6 and a pump 9. The pump 9 is in fluid communication with a reservoir 10 of the circuit 32 to which the damping members 2 are coupled. A control valve block 41 is operably engaged with the fluid circuit 32. The control valve block 41 is designed to handle flow rates in the range of 0 to 200 litres per minute.

The pump 9 is capable of supplying both ends 1 1 , 12 of the cylinder 1 3 with fluid. The electronic control unit 8 has a software control program with a module for generating control signals for controlling the flow of fluid 7 to each end 1 1 , 12 of the cylinder 1 3 in response to signals from the sensor 8. Alternatively, the electronic control unit 8 is implemented using hardware. When a large downward load is experienced by the hitch 33 of the suspension system 1 , this is detected by the sensor 6 and as a result, the electronic control unit 8 commands the pump 9 to provide additional fluid 7 to the barrel end 1 2 of the cylinder 1 3, providing the necessary damping effect. When a large upward load is experienced by the hitch 33 of the suspension system 1 , this is detected by the sensor 6 and as a result, the electronic control unit 8 commands the pump 9 to provide additional fluid 7 to the annu!us 1 1 end of the cylinder 1 3, providing the necessary damping effect. After the load has been detected and the fluid 7 provided to the correct end of the cylinder 1 3, the sensor 6 continues to monitor the fluid and, if necessary, fluid 7 can be provided to the end of the cylinder 13 opposite the end that received the initial infusion of fluid 7 to further balance the system 5 and provide the ongoing desired damping effect.

When the loads experienced by the hitch 33 of the suspension system 1 are relatively low, load compensation is provided by the piston 14 and cylinder 1 3 arrangement and/or the accumulator 1 5 if required, with no assistance or fluid balancing provided by the electronic control unit 8. The sensor 6 still detects measurable fluid parameters but the electronic control unit 8 does not take any action.

The electronic control unit 8 is in operable engagement with a visual display unit 1 8 via a wired connection 17. The visual display unit 1 6 is located within easy viewing distance of a driver of the towing vehicle and the output of the sensor 8 is used to form the basis of a status display on the visual display unit 18 so that the driver of the towing vehicle 31 can monitor the operating conditions of the suspension system 1 during use.

The damping member 2 has a damping cylinder 1 3 and a piston 14 which is pivotaliy attached at a first end 19 to a back plate 20 of the towing hitch 33 which is movably mounted to the towing vehicle 31 .

The annu!us end 1 1 of the cylinder provides an opening 21 for receiving a shaft 22 of the piston 14. The piston has a head 23 which is slidably mounted within the cylinder 1 3 at a second end 24 of the shaft 22. The head 23 of the piston 14 creates two isolated chambers 25. 26 within the cylinder 13, each with fluid 7 therein.

The barrel end 1 2 of the cylinder 13 is pivotaliy attached to a suspension mount frame 27, which is in turn fixed to the towing vehicle 31 .

In Figure 5, there is shown as second embodiment of suspension system having the same overall structure of the system 1 shown in Figure 2. The only feature differing from the system 1 shown in Figure 2 is that the cylinder and piston with a fluid circuit has been replaced with a mechanical shock absorber 51 having a spring 51 . The spring 51 is designed for absorbing and damping the generally vertical forced being transferred from the towed vehicle through the towing hitch and suspension system to the towing vehicle. In Figure 7, 8 and 9 there is shown a further embodiment of suspension system indicated genera!iy by the reference numeral 61 . In this embodiment, the towing hitch 62 is movabiy mounted on the suspension system 61 . The towing hitch 62 is mounted on the damping member 63. The damping member 63 is provided by a pair of cylinders 64 spaced apart from one another on a mounting frame 65 which is mechanically fixed to the towing vehicle. The towing hitch 62 also has a mounting frame 66 which is connected to a pair of arms 67 protruding from the cylinders 64. it will of course be appreciated that a mechanical damping system such as shown in Figure 5 can be provided between the arms 67 and the cylinders 64 or alternatively a fluid damping system such as the system described with reference to Figures 1 to 4 could equally be utilized. The towing hitch 62 of Figure 7 has an associated locking arrangement 68 shown in detail in Figure 6. The locking arrangement 68 has a biasing member 69 for biasing the locking arrangement 68 into a locking position under normal conditions. Advantageously, the biasing member 69 ensures that the locking arrangement 68 is maintained in a position relative to the towing hitch 62 for securely retaining a connector portion 71 of the towed vehicle on the towing hitch 62 during use.

The locking arrangement 68 has a spring loaded lock keeper member 72 normally protruding above the space 73 of a towing hitch 62 formed for receiving a towing ring 71 or similar coupling of a towed vehicle.

The towing hitch 62 of Figure 8 is a tow ball 92 having an associated locking arrangement 88. The locking arrangement 88 has a biasing member 89 for biasing the locking arrangement 88 into a locking position under normal conditions. Advantageously, the biasing member 89 ensures that the locking arrangement 88 is maintained in a position relative to the towing hitch 62 for securely retaining a connector portion of the towed apparatus on the towing hitch 62 during use.

The locking arrangement 88 has a pair of arms 90 pivotaily mounted onto opposing sides of the tow bail 92 with a connecter member 91 joining the arms 90 and normally protruding above the space over the towing bail 92 formed for receiving a towing ring 71 or similar coupling of a towed vehicle. In Figure 9, the towing hitch 62 is a towing bar 95 with a pair of spaced apart jaws 96 each having an aligned 97 aperture formed for receiving a pin.

In figures 1 0, 1 1 , and 12 a fifth embodiment of the suspension system 1 01 is shown wherein the towing hitch 102 and locking arrangement 1 03 are located on a drop base 104. The drop base 104 is rotatably coupled to a vehicle attachment frame 108 at an end 1 05 distal the end having the towing hitch 102 thereon.

The vehicle attachment frame 108 is a generally quadrangular frame which has a cavity in its underside. The drop base 1 04 is also generally quadrangular in shape and is slightly smaller in size than the vehicle attachment frame 1 08, such that the drop base 104 is insertable into the cavity of the vehicle attachment frame 108. The drop base 104 is an elongated tubular member having an internal channel.

The towing hitch 1 02 and locking arrangement 103 are mounted on the drop base 104 with the towing hitch 1 02 being movable relative to the locking arrangement 103. As the towing hitch 1 02 and locking arrangement 1 03 are mountable on the drop base 1 04 and move vertically together as the drop base 104 is moved, the towing ring or similar coupling means (not shown) of a towed vehicle cannot become wedged beneath the locking arrangement 103 or suspension system 1 01 as the drop base 1 04 is moved towards the vehicle attachment portion 1 08.

The towing hitch 1 02 is movable relative to the locking arrangement 1 03 and the drop base 104 as it is slidably mounted via a drop base mounting member 106. The drop base mounting member 106 is generally quadrangular in shape and is slightly smaller than the drop base 1 04, such that the drop base mounting member 106 is slidably mountable within the channel of the drop base 104. The locking arrangement 103 is located on an upper surface 107 of the drop base 104.

The towing hitch 1 02 can be moved away from the locking arrangement 103 to allow engagement with a towing ring or similar coupling means of a towed vehicle (not shown), and subsequently moved towards the locking arrangement 103 to secure the towing ring or similar coupling means of a towed vehicle (not shown) for towing. As there is no relative vertical movement between the towing hitch 1 02 and the locking arrangement 1 03, there is no risk that the towing ring or similar coupling means of a towed vehicle (not shown) will become wedged between the drop base 1 04 and the vehicle attachment frame 108.

In relation to the detailed description of the different embodiments of the invention, it will be understood that one or more technical features of one embodiment can be used in combination with one or more technical features of any other embodiment where the transferred use of the one or more technical features would be immediately apparent to a person of ordinary skill in the art to carry out a similar function in a similar way on the other embodiment.

In the preceding discussion of the invention, unless stated to the contrary, the disclosure of alternative values for the upper or lower limit of the permitted range of a parameter, coupled with an indication that one of the said values is more highly preferred than the other, is to be construed as an implied statement that each intermediate value of said parameter, lying between the more preferred and the less preferred of said alternatives, is itself preferred to said less preferred value and also to each value lying between said less preferred value and said intermediate value.

The features disclosed in the foregoing description or the following drawings, expressed in their specific forms or in terms of a means for performing a disclosed function, or a method or a process of attaining the disclosed result, as appropriate, may separately, or in any combination of such features be utilised for realising the invention in diverse forms thereof as defined in the appended claims.