Self-adjusting electric park brake assembly

Abstract

The present invention relates to an electric, self-adjusting park brake assembly for locking a wheel hub of a stationary towed vehicle in a substantially motionless state. The park brake assembly includes a brake drum configured to rotate correspondingly with the wheel hub, and one or more brake shoes located internally or externally of the brake drum and configured to be operated such that the minimum pressing force required to engage and thereby lock the brake drum is consistently applied by the brake shoe(s) irrespective of the wear rate of the brake shoe(s). A radial pressing force is applied on a surface of the drum by moving the shoe(s) radially until they frictionally engage the surface to an extent that substantially prevents rotation of the wheel hub. The assembly further includes one or more electric motors configured to activate the brake shoe(s), and a switch electrically connected to the electric motor(s).

Description

SELF-ADJUSTING ELECTRIC PARK BRAKE ASSEMBLYFIELD OF THE INVENTION

[0001] The present invention relates to a self-adjusting electric park brake assembly and, in particular, to an electric park brake assembly for use on towed vehicles such as caravans, campers and trailers. The assembly includes one or more brake shoes mounted internally or externally of a brake drum and controlled such that the minimum pressing force required to engage and thereby lock the brake drum is consistently applied by the brake shoe(s) irrespective of the wear rate of the brake shoe(s).BACKGROUND OF THE INVENTION

[0002] Park brake assemblies in towed vehicles such as caravans, campers and trailers, also known as park brakes, parking brakes, and handbrakes, are assemblies used to lock one or more of the vehicle wheels to secure the towed vehicle in a parked (i.e. motionless) state. Such assemblies are typically operated after a self-propelled (also referred to herein as towing) vehicle has been parked and it is not uncommon for drivers to engage the park brake of both the towing and towed vehicles. A driver would typically utilise a park brake when the driver prefers to utilise a wheel lock mechanism to ensure that the towed vehicle is prevented from moving whilst in the parked state.

[0003] In an example, a driver may elect to operate a park brake assembly after parking their vehicle on a sloping surface. However, even when a vehicle is parked on a flat surface, it is generally considered good practice to operate the park braking system(s) in view of the potential for the regular brakes of the towing vehicle to fail, e.g. due to stress, another vehicle colliding with the parked vehicle, etc.

[0004] Conventional park brake assemblies are typically associated with the regular brake system of the towing vehicle (i.e. the brake system used to slow or stop the vehicle when the vehicle is in motion), although they operate to bypass the regular brake system. For example, a vehicle may include a drum brake on each rear wheel where each drum brake includes a drum that rotates together with the wheel. The drum brake further includes two internal, crescent-shaped brake shoes having a curvature that substantially corresponds with that of the internal surface of the drum. Each shoe includes heatresistant material on its outer surface and is configured to be moved outwardly, in opposite radial directions, towards the inner surface of the drum until the heat resistant material fictionally contacts the drum inner surface to an extent that slows the rate of rotation of the drum (and hence the wheel and vehicle).

[0005] The park brake of a towing vehicle may be a mechanism incorporated into the drum brakes. In an example, the park brake includes a lever operatively positioned inside the drum that when actuated compresses the brake shoes and locks the brake shoes in their compressed position. A mechanical actuator, such as a manually operated handbrake or a park brake pedal located inside the vehicle cabin, is typically used to trigger the lever from within the vehicle cabin, which in turn causes the necessary force to be transmitted through hydraulic cables to the lever. In particular, when the cables are tightened, the lever is triggered, and the brake shoes are compressed as described above.

[0006] In the case of caravans, campers and trailers, which are towed rather than self-propelled vehicles, there is typically a drum park brake installed on one or more of the rear wheels to secure the caravan, camper or trailer, particularly for when the towed vehicle is detached from a towing vehicle. Whilst such drum brakes are not the same as the towing vehicle brakes since they are not actuated from inside the towing vehicle cabin, they work in a similar manner as described above in that they include a drum and typically two internal, crescent-shaped shoes configured to make contact with and thereby lock the drum and hence the wheel when actuated. The mechanical actuator for applying the park brake is typically a park brake lever provided on a frame member of the caravan, camper or trailer (eg. the A-frame draw bar of a trailer) to allow operators to manually operate the park brake.

[0007] A problem with existing manual park brake systems such as those described above is that when the brake shoes of the drum brake start to wear, the holding ability of the park brake is adversely affected since the worn shoes are positioned further away from the inner surface of the drum and hence have to be moved further before they touch the drum. This poses a safety risk since the user is required to manually actuate such movement and may not have the strength nor an appreciation of how much force needs to be applied in order to ensure that the vehicle is properly secured. In addition, since manual park brakes involve the use of exposed cables to transmit lever movement, suchbrakes tend to develop stretched cables which are unsightly and can also pose a safety risk.

[0008] An existing method of addressing the shoe wear issue described above includes replacing the park brake shoes, although this can be a costly solution. Drum brakes also commonly include a self-adjusting pulley inside the drum that takes and adjusts the shoes out further in circumstances where the shoe is moving too far before it touches the internal drum surface. However, such mechanical self-adjusting components can be prone to malfunction, wear and rust and hence are not very reliable. In addition, whilst manual adjustment of the position of each shoe is possible, this requires some level of skill and hence is not an option that is available to all operators. Another known method of attempting to address this issue is by ensuring that an appropriate amount of force is applied by the operator when manually actuating the park brake lever, ie. a force sufficient to ensure that the shoes move sufficiently to appropriately engage the drum internal surface. However, as mentioned earlier, ensuring that a sufficient application of strength is applied to the lever can be difficult for some operators.

[0009] Accordingly, the Applicant has recognised a need for an improved park brake assembly for use in drum type brakes of towed vehicles such as caravans, campers and trailers that does not rely on an operator to apply the park brake manually, addresses the issue of brake shoes being out of adjustment due to wear, and does not require the use of cables.

[0010] It is an object of the present invention to overcome at least some of the aforementioned problems or to provide the public with a useful alternative.

[0011] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any suggestion, that the prior art forms part of the common general knowledge.SUMMARY OF THE INVENTION

[0012] In a first aspect, the present invention provides an electric, self-adjusting park brake assembly for locking a wheel hub of a stationary towed vehicle in a substantially motionless state, the park brake assembly including: a brake drum configured to rotate correspondingly with the wheel hub; one or more brake shoes located internally or externally of the brake drum and configured to be operated to apply a radial pressing force on a surface of the drum by being moved radially until the shoe(s) fictionally engage the surface to an extent that substantially prevents rotation of the wheel hub; one or more electric motors configured to activate the brake shoe(s); and a switch electrically connected to the one or more electric motors such that operation of the switch causes the one or more electric motors to activate the brake shoe(s).

[0013] In an embodiment, a minimum radial pressing force that is required to be exerted on the surface of the brake drum to substantially prevent rotation of the wheel hub is predefined.

[0014] In an embodiment, the pressing force applied by the brake shoe(s) on the surface of the brake drum is monitored in substantially real time, and the brake shoe(s) are configured to be moved radially to apply said radial pressing force on the surface until the predefined minimum pressing force has been detected on the brake drum surface. In other words, radial movement of the brake shoe(s) continues and does not cease until such time that the predefined pressing force required to substantially prevent rotation of the brake drum has been detected. This ensures that the park brake assembly is “self- adjusting” since there is a consistent amount of force applied on the brake drum during each use irrespective of the wear rate of the brake shoe lining. In other words, all take up caused by wear is self-adjusted by the preset electric clamping force. Whether the wear rate is low or high, the shoe will be radially moved in the direction and to the extent required to achieve the predefined pressing force.

[0015] In an embodiment, the brake drum is included as a component of the wheel hub. In an alternative embodiment, the brake drum is included as a component of the park brake assembly and requires installation onto the wheel hub.

[0016] In an embodiment, the wheel hub is mounted at the free end of a wheel axle of the stationary towed vehicle, and components of the park brake assembly including the one or more electric motors are mounted to the wheel axle using a bracket and hence are rotatable therewith.

[0017] In an embodiment in which there are two brake shoes located externally of the brake drum, the one or more electric motors are configured to cause a worm drive to rotate, which in turn causes associated gears attached to the brake shoes to initiate compression of the brake shoes and thereby enable said brake shoes to apply said radial pressing force around the external surface of the wheel drum.

[0018] In this embodiment, the brake drum has a cylindrical shape such that the external surface thereof is substantially circular, and the brake shoes are correspondingly shaped such that the brake shoes are annular and journal around the external perimeter of the brake drum. In the activated mode, the brake shoes are in contact with the external surface of the brake drum, and in the deactivated mode, the brake shoes are spaced apart from the external surface of the brake drum such that there is no contact therebetween.

[0019] In this embodiment, each brake shoe includes a pivot mechanism which allows the brake shoe to compress inwardly based on rotation of the gears.

[0020] In an alternative embodiment in which there are two brake shoes located internally of the brake drum, the electric motor is configured to cause a link that connects the electric motor to a mechanical park brake actuation lever (also known as a strut or “dog bone”) to move in a linear direction, wherein such linear movement causes the actuation lever which extends between the two brake shoes to rotate about a pivot axis in a configuration that causes a first member of the lever to move in one direction to cause a first brake shoe to apply said radial pressing force to the internal surface of the brake drum, and a second member of the lever to move in an opposite direction to the first member to cause a second brake shoe to simultaneously apply an equal and opposite force to the opposed internal surface of the brake drum.

[0021] In this alternative embodiment, the brake drum has a cylindrical shape such that the internal surface thereof is substantially circular, and the brake shoes are substantially crescent shaped and extend along the internal perimeter of the brake drum. In the activated mode, each brake shoe is in contact with the internal surface of the brake drum, and in the deactivated mode, each brake shoe is spaced away from the internal surface of the brake drum such that there is no contact therebetween.

[0022] In this alternative embodiment, each brake shoe includes a pivot axis which allows the brake shoes to rotate about the pivot axis when actuated to thereby extend radially outwardly.

[0023] In this alternative embodiment, the brake shoes further include a brake shoe adjuster that is used to maintain the correct distance between the brake shoes and the brake drum in circumstances where the brake drum also provides a service brake function (ie. when the brake drum is used two purposes, namely, to provide the towed vehicle with capacity to brake in tandem with the brake system of the towing vehicle, and to also provide park brake functionality when the vehicles become stationary.

[0024] In an embodiment, the extent to which the brake shoe is moved radially inwardly or outwardly to apply said minimum radial pressing force on the surface of the brake drum is controlled using a control module. In this regard, the control module is configured to detect when the minimum amount of pressure is being applied against the surface of the brake drum and then at that point cease operation of the electric motor in order to stop the shoes from further radial movement.

[0025] In an embodiment, when the switch is operated to deactivate the park brake assembly, the motor(s) are operated to release the pressing force on the drum surface. In this regard, the control module is configured to operate the electric motor in order to cause the shoes to move in the opposite direction until they have arrived back in their rest positions in which they make no contact with the internal surface of the brake drum.

[0026] In an embodiment, the control module further controls the timed activation and deactivation of the radial pressing force.

[0027] In an embodiment, the switch, control module and one or more electric motors are electrically connected through a wiring harness.

[0028] In an embodiment, the vehicle is a towed vehicle such as a caravan, campervan or trailer configured to be transported by a towing vehicle, the towed vehicle including a structural frame including a draw bar.

[0029] In an embodiment, the switch and control module are mounted to the draw bar of the towed vehicle to enable operation of the switch from outside of the vehicle.

[0030] In an embodiment, the one or more electric motors are powered by the towing vehicle (eg. supplied with 12 or 24 volts of electricity from the battery of the towing vehicle).

[0031] In an embodiment, the control module is further configured to monitor when the towed vehicle is detached from the towing vehicle and to automatically operate the park brake assembly.

[0032] In an embodiment, the brake drum is a 10 inch or a 12 inch brake drum.

[0033] According to a further aspect, the present invention provides a towed vehicle wheel hub including an electric, self-adjusting park brake assembly configured in accordance with one or more of the preceding statements.

[0034] According to a still further aspect, the present invention provides a towed vehicle, such as a caravan, campervan or trailer, including at least one electric, self- adjusting park brake assembly configured in accordance with one or more of the preceding statements.BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Features of the present disclosure are illustrated by way of example and not limited in the following figure(s), in which like numerals indicate like elements, in which:

[0036] Figure 1 illustrates a top view of components of a park brake assembly configured in accordance with the present invention, including an electric park brake switch, control module and wiring harness, mounted to the draw bar of a towed trailer;

[0037] Figure 2 illustrates a side view of a wheel axle I hub and components of a park brake assembly configured in accordance with a first embodiment of the present invention, the components including an electric park brake motor, worm drive, gears, and external brake shoes;

[0038] Figure 3 illustrates a side view of the wheel axle / hub and components of the park brake assembly shown in Figure 2;

[0039] Figure 4 illustrates a rear perspective view of a park brake assembly configured in accordance with a second embodiment of the present invention, the assembly including internal brake shoes; and

[0040] Figure 5 illustrates a front perspective view of the park brake assembly of Figure 4.DETAILED DESCRIPTION OF EMBODIMENT(S) OF THE INVENTION

[0041] For simplicity and illustrative purposes, the present disclosure is described by referring to embodiment(s) thereof. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the disclosure. It will be readily apparent, however, that the current disclosure may be practised without limitation to the specific details disclosed herein. In other instances, some features have not been described in detail to avoid obscuring the disclosure.

[0042] The present invention relates to an electric, self-adjusting park brake assembly (100) for locking a wheel hub (1 10) of a stationary towed vehicle (120), such as a caravan, campervan or trailer, in a substantially motionless state.

[0043] According to each of the embodiments described herein, the park brake assembly (100) relies upon a brake drum (130A, 130B) (which may form part of the assembly (100) or may be pre-existing on the wheel hub (1 10)) which is configured to rotate correspondingly with the wheel hub (110), and one or more brake shoes (140A, MOB) located internally or externally of the brake drum (130). In the first embodiment shown in Figures 2 and 3, there are two externally located brake shoes (140A) shaped such that the brake shoes (140A) extend around an external surface (150A) of the brake drum (130A), and in the second embodiment shown in Figures 4 and 5, there are two internally located brake shoes (MOB) shaped such that the brake shoes (MOB) extend along internal surface (150B) of the brake drum (130B). The brake shoes (140A, MOB) are configured to be operated to apply a radial pressing force on the surface (150A, 150B) of the drum (130A, 130B) by applying a radial compressive force towards the surface (150A, 150B) until the shoe(s) (140A, MOB), or a lining thereof that is made of heat resistant material, fictionally engages the surface (150A, 150B) to an extent that substantially prevents rotation of the wheel hub (1 10). It will be appreciated that preventing rotation of at least one wheel hub (1 10) of a towed vehicle (120) substantially secures the towed vehicle (120) (ie. prevents the vehicle from moving) since the at least one wheel hub (1 10) is prevented from rotating.

[0044] Each assembly (100) further includes one or more electric motors (160) configured to activate the brake shoe(s) (140A, MOB), and a switch (170) electrically connected to the one or more electric motors (160) such that operation of the switch (170)causes the one or more electric motors (160) to activate or deactivate the brake shoe(s) (140A, 140B).

[0045] As mentioned above, the vehicle (120) to which the assembly (100) may be installed is a towed vehicle such as a caravan, campervan or trailer. It will be appreciated that such vehicles may already have a brake assembly installed, such as a drum brake assembly, and such existing assemblies may be modified in order to incorporate the brake assembly (100) of the present invention. In other words, each park brake assembly (100) of the present invention may be utilised in either scenario since a brake drum (130) will either already be installed to the wheel hub (1 10) or can easily be fitted thereto.

[0046] In the general example shown in Figure 1 , the vehicle (120) is a trailer configured to be towed by a self-propelled vehicle (not shown). Shown in Figure 1 is the drawbar (230) of the trailer and some components of each park brake assembly (100) mounted thereto. In particular, mounted to the drawbar (230) are the electric switch (170) and the control module (210) as well as the wiring harness (220) electrically connecting these components to the one or more electric motors (160) positioned adjacent the wheel hub (110) as shown in the embodiments of Figures 2 to 5.

[0047] It will be appreciated that the wheel hub (1 10) is mounted at the free end of a wheel axle (180) of the trailer (120), as shown by way of example in Figure 2, and is configured to rotate together with the wheel axle (180. Some components of the park brake assembly (100A) shown in Figures 2 and 3 including the one or more electric motors (160) are illustrated as being mounted to the wheel axle using a bracket (190). Accordingly, components of the park brake assembly (100) shown in Figure 2, including the bracket (190), electric motor (160), worm drive (195), associated gears (200) and brake shoes (140A), will also rotate together with the wheel axle (180). The same applies to the electric motor (160) and brake shoes (MOB) of the park brake assembly (100B) shown in Figures 4 and 5, although in this second embodiment there is no requirement to use a bracket to support components since the motor and shoes are components of the brake drum (130B).

[0048] The function of the worm drive (195) and gear (200) in the first embodiment would be well known to those skilled in the art. A worm drive (195) includes a spiral thread (198) that engages with and drives the gears (200) which in the embodiment showncomprise two perpendicularly disposed toothed wheels (202) and (204). The first toothed wheel (202) has a pivot axis that extends perpendicularly to the axis of rotation of the worm drive (195) and changes the rotational movement by 90 degrees, and the second toothed wheel (204) engages with the first toothed wheel (202) in a manner that changes the rotational movement again by 90 degrees. This configuration allows the worm drive (195) and gears (200) to extend over the wheel hub (1 10) and then radially inwardly towards the brake drum (130A) where the second gear (204) engages with the top of the brake shoes (140A). For example, the second toothed wheel (204) may engage with geared teeth (not shown) associated with an external surface of the brake shoes (140A), such that the geared teeth mesh at all times with the second toothed wheel (204). Accordingly, the gears (200) and external brake shoes (140A) interact in such a way that rotation of the worm drive (195) and toothed wheels (202) and (204) initiates movement of the brake shoes (140A) in a radially inward direction, as explained in greater detail below. Such movement of the brake shoes (140A) enables the brake shoes (140A) to apply a radial pressing force around the external surface (150A) of the brake drum (130A).

[0049] In most applications, the brake drum (130A) will have a cylindrical shape such that the external surface (150) with which the brake shoes (140A) engage is substantially circular. As shown in Figure 2, the brake shoes (140A) are correspondingly annular such that the brake shoes (140A) journal around the external perimeter of the brake drum (130A). In this regard, it will be appreciated that in order for the annular brake shoes (140A) to move in a manner that causes a radial pressing force to be applied against the external surface (150) of the brake drum (130A), the annular brake shoes (140A) will include a feature which allows for the brake shoes (140A) to compress inwardly.

[0050] Figure 3 shows one example of how this may be achieved. In particular, Figure 3 illustrates a configuration in which rotation of the worm drive (195) and gears (200) in one direction will cause areas (240) and (250) of each brake shoe (140A) to make the most prominent frictional contact with the external surface (150A) of the brake drum. This interaction is caused by the brake shoes (140A) having fixed ends (260) positioned radially opposite (at substantially 180 degrees from) where the shoes (140A) engage with the second toothed wheel (204), wherein each first end (260) represents a pivot point for each respective brake shoe (140A). Since the ends (260) are secured to a backing plate associated with the brake drum (130A), they are fixed in place and hence the second(free) end of each shoe (140A) which interacts with the gear (204) is only capable of pivotal motion about the point. The free end of each shoe (140A) interacts with the gears (200) in a configuration whereby the pivotal motion caused by rotation of the worm drive (195) and gears (200) is sufficient to allow the range of motion required of the brake shoes (140A) to cause its internal lining to make frictional contact with the brake drum external surface (150A) along at least the areas (240) or (250) of each brake shoe. In order to deactivate the brake assembly (100A), the worm drive (195) and gears (200) would be rotated to cause the brake shoes (140A) to move radially outwardly such that the internal lining thereof is no longer making contact with the external surface (150A).

[0051] It will be appreciated therefore that reference to “compress” or “compression” herein when describing the movement of the brake shoes (140A) to engage with the external surface (150A) of the brake drum (130A) does not necessarily require the entire surface area of the shoe’s internal lining to move inwardly and make contact with the external surface (150A) since, as per the embodiment described above, a portion ((240) or (250)) of the internal lining may be caused to make frictional contact. Of course, it will also be appreciated that this represents but one technique that may be utilised to cause the brake shoe internal linings to fictionally engage the external surface (150A) of the brake drum (130A), and that other configurations may be possible.

[0052] In the second embodiment shown in Figures 4 and 5, the brake drum (130B) includes two crescent-shaped brake shoes (MOB) located internally of the brake drum (130B) and configured to apply a radially outward pressure against the internal surface of the drum (not shown) to prevent rotation of the wheel hub (110). The electric motor (160) is configured to cause a link (265) that connects the electric motor (160) to a mechanical park brake actuation lever (270) (also known as a strut or “dog bone”) to move in a linear direction (268) when the park brake is actuated, wherein such linear movement of the link (265) causes corresponding linear movement of a first member (271 ) of the actuation lever (270) and hence a first brake shoe to which the first member (271 ) is fixed thereby causing the first brake shoe to apply a radial pressing force against the internal surface of the brake drum (130A). Such movement causes a second member (273) of the lever (270), which is fixed to the second brake shoe and connected to the first member (271 ) via a pivot pin (275), to move in an opposite direction (274) to the first member (271 ) which causes the second brake shoe to simultaneously apply an equal and opposite forceagainst the internal surface of the brake drum (130A). The relative motion between the two members of a “dog bone” lever as described above is known in the art and hence won’t be described in greater detail herein.

[0053] In this alternative embodiment, the brake drum has a cylindrical shape such that the internal surface thereof is substantially circular, and the two brake shoes (MOB) are substantially crescent shaped and extend along the internal perimeter of the brake drum. In the activated mode, each brake shoes (MOB) are in frictional contact with the internal surface of the brake drum, and in the deactivated mode, each brake shoe (MOB) is spaced inwardly away from the internal surface of the brake drum such that there is no contact therebetween. The common pivot point (275) between the shoes (MOB) allows the brake shoes (MOB) to rotate about the pivot point (275) when actuated to thereby extend radially outwardly (when the assembly (100B) is activated) and inwardly (when the assembly (100B) is deactivated).

[0054] The brake shoes (MOB) further include a brake shoe adjuster (280) that is used to maintain the correct distance between the brake shoes (MOB) and the brake drum internal surface in circumstances where the brake drum also provides a service brake function (ie. when the brake drum is used for two purposes, namely, to provide the towed vehicle with capacity to brake in tandem with the brake system of the towing vehicle, and to also provide park brake functionality when the vehicles are stationary as described herein.

[0055] In each of the above-described embodiments, the minimum radial pressing force required to be exerted on the brake drum (130A, 130B) to substantially prevent rotation of the wheel hub (1 10) is predetermined. The radial pressing force that is applied by the brake shoe(s) (140A, 140B) on the surface (150A, 150B) of the brake drum (130A, 130B) is monitored in substantially real time, and the brake shoe(s) (140A, MOB) are configured to be moved radially to apply the radial pressing force on the surface (150A, 150B) until the predetermined minimum radial pressing force has been detected on the brake drum surface (150A, 150B). In other words, radial movement of the brake shoe(s) (140A, MOB) continues and does not cease until such time that the predefined pressing force required to substantially prevent rotation of the brake drum (130A, 130B) has been detected. This will ensure that the park brake assembly (100A, 100B) is self-adjusting since there will be a consistent amount of force applied on the brake drum (130A, 130B)during each use, irrespective of the wear rate of the brake shoe lining. In other words, all take up caused by wear will be self-adjusted by the preset electric clamping force. Whether the wear rate is low or high, the shoes (140A, 140B) will be radially moved to the extent required to achieve the predefined pressing force.

[0056] In the event that the heat-resistant lining of the brake shoe(s) (140A, MOB) become excessively worn such that the shoe(s) (140A, 140B) can no longer perform their function of gripping the surface (150A, 150B) of the brake drum (130A, 130B), then at that stage the lining, or the brake shoes (140A, MOB) themselves, will require replacement.

[0057] The extent to which the brake shoes (MOA, MOB) are moved radially inwardly or outwardly to apply the minimum radial pressing force on the brake drum (130) is controlled using the control module (210) mounted to drawbar (230) which provides current to the one or more electric motors (160). In this regard, the control module (210) is configured to detect when the minimum amount of pressure is being applied against the surface (150A, 150B) of the brake drum (130A, 130B) and then at that point cease operation of the electric motor (160) in order to stop the shoe(s) (MOA, 140B) from further radial movement. The control module (230) is further responsible for controlling the timed activation and deactivation of the radial pressing force based on operation of the switch (170), and it will be appreciated that in addition to activating the park brake assembly (100), the switch (170) is also used to deactivate the park brake assembly (100) by causing the pressing force on the drum surface (150A, 150B) to be released.

[0058] The one or more electric motors (160) used to drive the worm drive (195) and gears (200), and hence the compression and decompression of the brake shoes (MOA) in the first embodiment, and to drive the link (265) and hence the actuation lever (270) in the second embodiment, may be self-powered using a battery (205) that forms part of the brake assembly (100), as shown in Figure 1 , or may be powered by a battery (not shown) associated with an external source such as another vehicle, eg. a vehicle responsible for towing the towed vehicle (120). For example, in the latter example, the electric motor (160) may be supplied with 12 or 24 volts of electricity from the battery of the towing vehicle (not shown).

[0059] There may be applications that benefit from an automatic activation of the park brake assembly (100). In one example, the control module (210) may be configured to monitor when a towed vehicle (120) has been detached from a towing vehicle (eg. when a trailer has been detached from a towing automobile), and to automatically operate the park brake assembly (100) in order to secure the trailer (120).

[0060] It will be appreciated that the park brake assembly (100) may be a standalone product configured to be retrofitted to existing vehicles (120), i.e. provided as an aftermarket vehicle part or accessory. However, it will also be appreciated that the park brake assembly (100) can be offered pre-installed with new assemblies including but not limited to vehicle wheel hubs (110), vehicle axles (180), and towed or self-propelled vehicles (120).

[0061] The skilled addressee will appreciate the advantages of using a park brake assembly (100) in the manner described herein. By utilising an electric park brake, there is no longer a need for cables to be used. Further, there is no longer a need to manually adjust or prematurely replace or repair brake shoes since the park brake assembly (100) operates to apply the necessary radial pressing force against the brake drum (130A, 130B) to prevent movement of the wheel hub (110) irrespective of the level of wear associated with the brake shoe internal lining. In this way, the assembly (100) is self- adjusting and does not rely on an operator to apply the park brake manually or to make any manual adjustments to the brake shoe(s).

[0062] Throughout this specification and claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to mean the inclusion of a stated feature or step, or group of features or steps, but not the exclusion of any other feature or step, or group of features or steps.

[0063] The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any suggestion that the prior art forms part of the common general knowledge.

Claims

The claims defining the invention are as follows:1 . An electric, self-adjusting park brake assembly for locking a wheel hub of a stationary towed vehicle in a substantially motionless state, the park brake assembly including: a brake drum configured to rotate correspondingly with the wheel hub; one or more brake shoes located internally or externally of the brake drum and configured to be operated to apply a radial pressing force on a surface of the drum by being moved radially until the shoe(s) fictionally engage the surface to an extent that substantially prevents rotation of the wheel hub; one or more electric motors configured to activate the brake shoe(s); and a switch electrically connected to the one or more electric motors such that operation of the switch causes the one or more electric motors to activate the brake shoe(s).

2. An electric, self-adjusting park brake assembly according to claim 1 , wherein a minimum radial pressing force that is required to be exerted on the surface of the brake drum to substantially prevent rotation of the wheel hub is predefined.

3. An electric, self-adjusting park brake assembly according to claim 2, wherein the pressing force applied by the brake shoe(s) on the surface of the brake drum is monitored in substantially real time, and the brake shoe(s) are configured to be moved radially to apply said radial pressing force on the surface until the predefined minimum pressing force has been detected on the brake drum surface.

4. An electric, self-adjusting park brake assembly according to any one of the preceding claims, wherein the brake drum is included as a component of the wheel hub, or is included as a component of the park brake assembly and thereby requires installation onto the wheel hub.

5. An electric, self-adjusting park brake assembly according to any one of the preceding claims, wherein the wheel hub is mounted at the free end of a wheel axle of the stationary towed vehicle, and components of the park brake assembly including theone or more electric motors are mounted to the wheel axle using a bracket and hence are rotatable therewith.

6. An electric, self-adjusting park brake assembly according to claim 5, wherein the one or more brake shoes is located externally of the brake drum, and the one or more electric motors are configured to cause a worm drive to rotate, which in turn causes associated gears attached to the external brake shoes to initiate compression of the brake shoes and thereby enable said brake shoes to apply said radial pressing force around the external surface of the wheel drum.

7. An electric, self-adjusting park brake assembly according to either claim 5 or claim 6, wherein the brake drum has a cylindrical shape such that the external surface thereof is substantially circular, and the external brake shoes are correspondingly shaped such that the brake shoes are annular and journal around the external perimeter of the brake drum. In the activated mode, the brake shoes are in contact with the external surface of the brake drum, and in the deactivated mode, the brake shoes are spaced apart from the external surface of the brake drum such that there is no contact therebetween.

8. An electric, self-adjusting park brake assembly according to claim 7, wherein the brake shoes each include a pivot mechanism which allows each brake shoe to compress inwardly at least on one side of the brake drum based on rotation of the worm drive and gears.

9. An electric, self-adjusting park brake assembly according to any one of claims 1 to 4, wherein the assembly includes two brake shoes located internally of the brake drum, and the electric motor is configured to cause a link that connects the electric motor to a mechanical park brake actuation lever to move in a linear direction, wherein such linear movement causes the actuation lever which extends between the two brake shoes to rotate about a pivot axis in a configuration that causes the brake shoes to apply said radial pressing force to the internal surface of the brake drum.

10. An electric, self-adjusting park brake assembly according to claim 9, wherein the brake drum has a cylindrical shape such that the internal surface thereof issubstantially circular, and the brake shoes are substantially crescent shaped and extend inside the internal perimeter of the brake drum such that in an activated mode, each brake shoe is in contact with the internal surface of the brake drum, and in a deactivated mode, each brake shoe is spaced away from the internal surface of the brake drum such that there is no contact therebetween.1 1. An electric, self-adjusting park brake assembly according to claim 10, wherein each brake shoe includes a pivot axis which allows the brake shoes to rotate about the pivot axis when actuated to thereby extend radially outwardly.

12. An electric, self-adjusting park brake assembly according to any one of claims 9 to 1 1 , wherein the brake shoes further include a brake shoe adjuster used to maintain the correct distance between the brake shoes and the brake drum when the brake drum is also used as a service brake.

13. An electric, self-adjusting park brake assembly according to any one of the preceding claims, wherein the extent to which the brake shoe is moved radially inwardly or outwardly to apply said minimum radial pressing force on the surface of the brake drum is controlled using a control module.

14. An electric, self-adjusting park brake assembly according to claim 13, wherein the control module further controls the timed activation and deactivation of the radial pressing force.

15. An electric, self-adjusting park brake assembly according to either claim 13 or claim 14, wherein the control module is further configured to monitor when the towed vehicle is detached from a towing vehicle and to automatically operate the park brake assembly when detachment from the towing vehicle is detected.

16. An electric, self-adjusting park brake assembly according to any one of the preceding claims, wherein when the switch is operated to deactivate the park brake assembly, the motor(s) are operated to release the radial pressing force on the brake drum surface.

17. An electric, self-adjusting park brake assembly according to any one of the preceding claims, wherein the switch and control module are mounted to a draw bar associated with a structural frame of the towed vehicle to enable operation of the switch from outside of the towed and a towing vehicle, and the switch, control module and the one or more electric motors are electrically connected through a wiring harness.

18. An electric, self-adjusting park brake assembly according to claim 17, wherein the one or more electric motors are powered by the towing vehicle such that the electric motor(s) are supplied with 12 or 24 volts of electricity from a battery of the towing vehicle.

19. A vehicle wheel hub including an electric, self-adjusting park brake assembly configured in accordance with any one of the preceding claims.

20. A towed vehicle including at least one electric, self-adjusting park brake assembly configured in accordance with one or more of claims 1 to 17.21 . A self-propelled vehicle including at least one electric, self-adjusting park brake assembly configured in accordance with any one or more of claims 1 to 17.

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