AU2012371535B2 - Actuator assembly for a vehicle - Google Patents

Abstract

An actuator assembly (10) for a vehicle, the assembly including a housing (14) for containing an actuator (17) for controlling vehicle function and a plunger (18) which extends into the housing (14) via an opening (24) so as to be communicable with the actuator (17), wherein the plunger (18) and the opening (24) are each formed of dissimilar metal based materials so as to inhibit friction between the plunger (18) and the opening (24).

Description

PCT/AU2012/000202 WO 2013/126941 -1 -

ACTUATOR ASSEMBLY FOR A VEHICLE

Technical Field [001] The invention generally relates to an actuator assembly, in particular, an actuator assembly for a vehicle.

Background [002] Vehicles such as mining vehicles generally include a hand or foot operatable actuator assembly, such as a pedal assembly, for controlling the operation of the vehicle. Such pedal assemblies generally includes a pedal which is operable by the hand or foot and a linkage between the pedal and a sensor for determining the position of the pedal, for example, when the pedal is moved between depressed or released positions. The sensor then communicates the position of the pedal to a controller which in turn sends a drive signal to a motor or other similar component of the vehicle.

[003] For safety purposes in an underground mining environment at least the sensor and associated electrical components are generally required to be shielded or encased, such as by way of a flame proof casing, to inhibit a spark or fire generated within the casing by, for example, the sensor or associated electrical components, igniting the air in the underground mining environment which may, for example, contain an explosive mix methane or other flammable gases. Accordingly, the linkage is required to pass as least partially into and out of the flame proof casing via an opening to communicate die position of the pedal with the sensor.

[004] To maintain the integrity of the flame proof casing, the fit between the linkage and the opening of the flame proof casing is generally required to be a relatively tight fit. However, the fit must also allow for the passage of the linkage to ensure the linkage does not become impeded, for example, if the linkage were to become caught the pedal is in effect likewise caught which may result in the vehicle becoming uncontrollable. C:\NRPortbl\DCC\HFS\4882948_l.DOC-21/10/2016 2012371535 21 Oct 2016 -2- [005] Accordingly, there is a need for an actuator, in particular, a pedal assembly in which the at least the sensor is protected by a casing, such as a flame proof casing, whilst the linkage and hence the pedal is free to move between the depressed and released positions.

Summary [006] In accordance with a first aspect there is provided, an actuator assembly for a vehicle, the assembly including a housing for containing an actuator for controlling vehicle function and a plunger which extends into the housing via an opening so as to be communicable with the actuator, wherein the plunger and the opening are each formed of dissimilar metal based materials so as to inhibit friction between the plunger and the opening, and wherein the fit between an inside diameter of the opening and an outside diameter of the plunger is sufficiency tight to inhibit the passage of fire or spark.

[007] This paragraph has been deleted.

[008] In one form, one of the plunger and the opening is formed from a steel alloy and the other of the plunger and the opening is formed from a copper alloy.

[009] In one form, the copper alloy is an aluminium bronze alloy.

[0010] In one form, the aluminium bronze alloy includes in the range of approximately 80 and 88 weight % copper and approximately 8 to 10.5 % aluminium.

[011] In one form, the steel alloy is a stainless steel alloy having approximately at least 11 wt % chromium.

[012] In one form, the stainless steel includes in the range of approximately 16 to 18 wt % chromium and in the range of approximately 10 to 14 wt % nickel.

[013] In one form, the opening is provided by a bush fitted to the housing. 2012371535 21 Oct 2016 C:\NRPortbl\DCC\HFS\4882948_l.DOC-21/10/2016 -3 - [014] In one form, there is a maximum 0.4 mm concentric gap between the inside diameter of the opening and the outside diameter of the plunger.

[015] In one form, the plunger is an elongate rod adapted to move linearly relative the opening.

[016] In one form, the housing is a fire resistant housing formed from steel.

[017] In one form, the actuator includes a sensor and controller.

[018] In one form, the assembly further includes a pedal adapted to mechanically communicate with the plunger, the pedal being moveable between a released position, in which the plunger is in a retracted condition relative the opening and a depressed position, in which the plunger is in an extended condition extending relative the opening into the housing.

[019] In one form, the pedal is pivotally coupled to the housing.

[020] In one form, the pedal supports a bearing which is arranged to bear on an end of plunger so as to reduce lateral forces applied from the pedal to the plunger.

[021] In one form, the end of the plunger includes at least one collar to dimensioned to provide an end of travel stop for the elongate rod.

[022] In one form, the assembly further includes a spring arranged to return the pedal to the released position.

[023] In one form, the spring is arranged between the housing and the collar of the PCT/AU2012/000202 WO 2013/126941 -4- plunger such that elongate rod is urged toward the retracted condition which in turn urges the pedal toward the released position.

[024] In one form, a seal is provided between the collar and the housing to cover the elongate rod and opening.

[025] In one form, the seal is provided in the form of a flexible cylindrical boot concentrically arranged around the elongate rod so as to extend between the collar and the housing. i [026] In one form, the boot includes an aperture to allow the passage of a gas into and out of the boot.

[027] In one form, the aperture is fitted with a breather assembly.

[028] In one form, the breather assembly includes at least one of a filter and a silencer. Brief Description of the Figures [006] The invention is described, by way of non-limiting example only, by reference to the accompanying figures, in which;

Figure 1 is an exploded parts perspective view illustrating an actuator assembly;

Figure 2 is another exploded parts perspective view illustrating the actuator assembly;

Figure 3 is a perspective view illustrating the actuator assembly;

Figure 4 is another perspective view illustrating the actuator assembly; PCT/AU2012/000202 WO 2013/126941 -5-

Figure 5A is a side view illustrating the sensor and control housing;

Figure SB is a schematic diagram illustrating sensors and a controller associated with the sensor and control housing of Figure 5 A; and

Figure 6 is a perspective view of a bush, rod and housing of the actuator assembly. Detailed Description [007] Referring to Figures 1 and 2, there is shown an exploded view of an actuator assembly 10, in this example, shown as a pedal assembly 12, suitable for use, but not limited to, controlling a vehicle, in particular, a mining vehicle (not shown). Assembled views of the pedal assembly 12 are shown in Figures 3 and 4.

[008] Turning firstly to Figure 1, the pedal assembly 12 includes a housing 14, for containing an actuator 17 which in this example is provided in the form of a control and sensor assembly 16 and linkage or plunger 18 which extends into the housing 14 through a bush 20 which is fitted to aperture 22 of the housing 14. In this example, the linkage or plunger 18 is a unitary elongate rod 19 and the bush 20 provides an opening 24 dimensioned to allow the rod 19 to be communicable with the control and sensor assembly 16 within the housing 14.

[009] ' A foot pedal 26 is pivotally coupled to the housing 14 via a base plate 28 which in turn is connected to a front face 30 of the housing 14. The foot pedal 26 is arranged to mechanically communicate with the elongate rod 19 to linearly move the elongate rod 19 relative to the control and sensor assembly 16 to communicate the position of pedal 26 to the control and drive the vehicle.

[010] More specifically, the pedal 26 is moveable between a released position, in which the elongate rod 19 is in a retracted condition relative to the opening 24 and a depressed position, in which the elongate rod 19 is in an extended condition extending PCT/AU2012/000202 WO 2013/126941 -6- relative the opening 24 into the housing 14 so as to communicate with the control and sensor assembly 16.

[011] The elongate rod 19 includes a first end 29 having a flange 32 dimensioned to inhibit the first end 29 passing through the bush 20 to thereby retain at least the first end 29 of the rod 19 generally within the housing 14, for example, when the rod 19 is in the retracted condition. A second end 34 of rod 19 includes a collar 40 dimensioned to inhibit the second end 34 passing through the bush 20 to thereby retain at least the second end 34 generally outside the housing 14, for example, when the rod 19 is in the extended condition. The collar 40 is fitted to the second end 34 of the rod 19 by a pin 38 which passes through corresponding bores 36, 37 of the rod 19 and the collar 36, respectively. A ring 42 is fitted over the collar 40 to retain the pin 38.

[012] Referring now additionally to Figure 2, the collar 40 is generally cylindrically shaped having an axial bore 57, best shown in Figure 2, in which the rod 19 is fitted, a skirting flange 58 against which the ring 42 is fitted, a stepped recess 56 located on one end 58 and a substantially flat face 60 located at an opposing end 59.

[013] A seal 44, provided in this example in the form of a flexible boot 46, is fitted between the housing 14, more specifically the base plate 28, and the collar 40. The boot 46 is generally hollow as to define a void 69 which extends around and covers the rod 19, the bush 20 and the associated opening 24. The boot 46 is cylindrical in shape having multiple rubber or similar flexible sections which concertina relative to one another when the boot 46 is expand and collapsed.

[014] The boot 46 includes a first end 48 which is sealed and fitted against the base plate 28 and a second end 50 which sealed and fitted with the collar 40. The second end 50 of the boot 46 includes a neck 52 which is received by the stepped recess 56 of the collar 40.

[015] The boot 46 includes an aperture 62, best shown in Figure 3, to which a PCT/AU2012/000202 WO 2013/126941 -7- breather assembly 64 is fitted to allow the passage of air between the void 69 inside the boot 46 and the external environment. This inhibits a pressure build up within the void 69 of the boot 46 when the pedal is moved to the depressed position and inhibits the formation of a vacuum within the void 69 of the boot 46, when the pedal is released, which may prevent the pedal 46 returning to the released position.

[016] A spring arrangement 100 is concentrically fitted over the rod 19 so as to be located within the void 69 of the boot 46. The spring arrangement 100 includes an inner and outer helical springs 102 and 104, respectively, which are arranged to extend between the collar 40 and the housing 14, more specifically the bush 20, so as to bias or urge the collar 40 away from the bush 20 and thereby keeping the rod 19 in the retracted condition relative the bush 20 and hence retracted relative to the sensor and control assembly 16.

[017] The housing 14, is provided in this example, as a fire resistant or flame resistant housing 106, also commonly known a flame proof housing, with a square face 108 for connecting to the base plate 28 via fasteners 117. The housing 106 is preferably formed from K1045 Carbon steel which is a steel of slightly higher grade than mild steel.

[018] The flame resistant housing 106 includes a cylindrical hollow body 110 in which the control and sensor assembly 16 is located and end cap 112. An O-ring 114 is located between the end cap 112 and the body 110 to assist to seal the flame resistant housing 106. The body 110 includes ports 115 in which sealed fittings 116 are located to convey electrical cables (not shown) between the control and sensor assembly 16 and the external environment, more specifically, the associated drive systems, such as a motor, of the vehicle.

[019] The actuator 17, more specifically the control and sensor 16 assembly, includes a cylindrical control and sensor housing 120 which a central aperture 122 arranged to receive the rod 19 in at least the extended condition. The control and sensor housing 120 is attached to and supported by the flame proof housing 106 by fasteners 107 which pass through apertures 124 of the control and sensor housing 120 and attach to corresponding PCT/AU2012/000202 WO 2013/126941 -8- apertures located on an inside face of the flame resistant housing 106.

[020] Referring to Figures 3 and 4, the breather assembly 64 includes a conduit arrangement 66 and a filter 68 fitted to the conduit arrangement 66 to inhibit dust or other similar material from entering the void 69 of the boot 46. A silencer 70 is also provided, separately, or integrally formed with the filter 68. More specifically, the aperture 62 of the boot is provided at the first end 48 of the boot 46 to minimise movement of the boot 46 relative to the housing 14. The conduit arrangement 66 includes a series of conduits 72 and elbows 74 which extend from the aperture 62 of the boot 46, through an aperture 76 of the base plate 28, and rearward and laterally of the base plate 28 such that the filter 68 and die silencer 70 are located generally away from the pedal 26.

[021] The pedal 26 includes a body section 80 and a leg section 82 extending at an angle from the body section 80. The body section 80 includes opposing walls 84 which have upper apertures 86 for receiving a fastener 88 to pivotally couple the foot pedal 26 to a bracket 90 with corresponding apertures 92 of the base plate 28. The opposing walls 84 also include lower apertures 94 for receiving a shaft 96 which supports a bearing 98, better shown in Figures 1,2 and 4.

[022] The bearing 98 is cylindrical in shape and is concentrically mounted on the shaft 96 such that the bearing 98 rotates about the elongate axis of the shaft 96. Accordingly, in use, the outer circumference of the bearing 98 bears on the substantially flat face 60 of the collar 40, as is best shown in Figure 1, and as the pedal 26 is depressed and released the bearing 98 rolls along the face 60 of the collar 40.

[023] As may be appreciated, there is no direct connection between the pedal 26 and the collar 40. This inhibits lateral loading being applied to the rod 19 and results in substantially only linear forces that is - forces aligned with the elongate axis of the rod 19, being applied to the rod 19. The inhibiting of lateral loading is advantageous, as will be further later described, because the fit between the rod 19 and the bush 20 is relatively tight and any lateral loading may increase wear between the rod 19 and bush 20 and the PCT/AU2012/000202 WO 2013/126941 -9- likelihood of the rod 19 and bush 20 becoming in high friction contact or locking relative to one another.

[024] Accordingly, in operation, the pedal 26 may be depressed which results in the bearing 98 urging on the collar 40 which in turn linearly moves the rod 19 into the bush 20 to an extended position within the housing 14. As the rod 19 moves into the bush 20, the spring arrangement 100 becomes compressed and energised. Accordingly, when the pedal 26 is released, the reverse operation occurs, and the spring arrangement 100 urges the collar 40 away from the housing 14 which retracts the rod 19 from the bush 20 and the bearing 98, in turn, urges the pedal 26 back to the released position.

[025] Referring to the Figures SA and SB, which shows simplified schematics of the actuator 17, more specifically the control and sensor assembly 16, the control and sensor assembly 16 includes sensors 130, more specifically an induction sensor 131 and optical sensors 132, and a PIC controller 133, which are located within the control and sensor housing 120. The sensors 130 are arranged to determine if the pedal 26 is in the depressed position, the released position, or a position there between by measuring the relative position of the rod 19. The PIC controller 133 is located on a disk shaped printed circuit board, PCB, (not shown), which includes circuitry which ultimately interconnects the sensors 130 and the PIC controller 133 with electric caballing which exists the flame resistant housing 106 via the ports 114.

[026] The induction sensor 131 includes an oscillator coil 135 which is configured to generate an oscillator signal proportional length of the rod 19 extending into oscillator coil 135. The oscillator signal is received by the PIC controller 133.

[027] Two optical sensors 132 are positioned at the entry 136 of the central aperture 122 of the control and sensor housing 120. The optical sensors may be provided by LED emitters and receivers located on opposing side of the central aperture. The optical sensors 132 detect when the rod 19 has entered the control and sensor housing 120. Each optical sensor 132 provides a digital signal which a received by the PIC controller 133 to verify, PCT/AU2012/000202 WO 2013/126941 -10- calibrate and cross-check the oscillator signal received by the controller 133.

[028] If the verification between oscillator signal and the digital signals is successful, the PIC controller 133 in association with induction sensor 131 generates a suitable analogue signal 137, proportional to the position of the pedal 26, and the two digital signals 138 along with the analogue signal 137 are outputted from the pedal assembly 12. These signal are ultimately received by control and drive systems of the vehicle such that a user moving the pedal between the released and depressed positions causes a corresponding action of the vehicle, for example, driving forward or reversing.

[029] Referring now to Figure 6, the opening 24 of the bush 20 is elongate and extends between a first end 33 and a second ends 39 of the bush 20. Accordingly, in this example, the opening 24 is provided in the form of an elongate bore 125. The elongate bore 125 has a length which is non-insubstantial in comparison to the length of the rod 19. In this example, the elongate bore is at least 10% of the length of the rod 19. This provides a substantial surface area between the bore 125 and the bush 20, which assist to maintain the alignment of the rod 19. However, the substantial surface area between the bore 125 and the bush 20 also provides a potentially large wear and frictional surface that may restrict or inhibit the free movement of the rod 19 relative to the bore 125. Accordingly, the material selection of the rod 19 and bush 20 is important, as is further detailed below. The bush 20 may be fitted the housing by a treaded connection 41 and includes a hexagonal central flange 43 for gripping the bush 20 for installation and removal.

[030] The plunger 18, in this example provided as the rod 19, and the opening 24, provided in this example by the bush 20, are formed of dissimilar metal materials so as to inhibit frictional build up, otherwise known as adhesion, caused by so called “galling” or similar frictional mechanism between the rod 19 and the bush 20.

[031] Before describing the dissimilar metal materials in more detail, the phenomena of “galling” will be further described. The American Society of Testing and Materials (ASTM) defines galling as “a form of surface damage arising between sliding solids, PCT/AU2012/000202 WO 2013/126941 -11- distinguished by microscopic, usually localized, roughening and creation of protrusions, (i.e. lumps), above the original surface".

[032] Galling appears to be the most prevalent in solid sliding contact between stainless steels, aluminums, titaniums, and other alloys which self-generate an oxide surface film for corrosion protection. In use, the contact of sliding surfaces results in the protective oxide film being breached, possibly removed, and interface high points of the metal sliding surfaces may shear or lock together. This cumulative clogging-shearinglocking action causes increasing adhesion. In some cases, galling may lead to seizing - the actual freezing together of the two sliding metal parts. It is noted that galling is sometimes referred to “cold welding” in particular in relation to the freezing together of stainless steel components.

[033] The fit between an inside diameter of the opening 24 of the bush 20 and an outside diameter of the rod 19 is sufficiency tight to inhibit the passage of fire, associated flame, or spark from the housing 14. For example, the control and sensor assembly 16 or associated electrical components may generate a spark or flame which is required to be substantially contained within the housing 14 to prevent potential ignition of the environment surrounding the housing 14, which in the underground mining environment may include methane or other flammable substances.

[034] More specifically, in this example, there is a maximum 0.4 mm concentric gap between the inside diameter of the opening 24 of the bush 20 and the outside diameter of the rod 19. The opening 24 and the rod 19 are generally manufactured such that there is between a 0.06 mm and 0.1 mm concentric gap between the inside diameter of the opening 24 of the bush 20 and the outside diameter of the rod 19.

[033] In use, the opening 24 and the rod 19 undergo wear and the concentric gap may increase from the manufactured range of 0.06 mm and 0.1 mm. However, as will be further discussed below, in addition to inhibiting galling, the dissimilar metal materials of the rod 19 and the opening 24 of the bush 20 are also preferably required to have sufficient wear PCT/AU2012/000202 WO 2013/126941 -12- properties, such as hardness (HB), to inhibit the rod 19 and/or the opening 24 of the bush 20 from substantial wearing over the product life cycle, for example 1 million cycles, which may result in the concentric gap exceeding the maximum 0.4 mm.

[036] Accordingly, due the tight fit, any surface imperfections caused by galling or similar process, or ingress of direct between the rod 19 and the bush 20, may results in the rod 19 and bush 20 becoming seized and locked together. This may result in the rod 19 being trapped or frozen inside the sensor and control assmeblyl6, likewise freezing the pedal 26 in a depressed position, which in turn results in the vehicle becoming potentially uncontrollable, which may have catastrophic consequences, particularly in an underground mining environment.

[037] Typically, in these types of pedal assemblies 12, both the bush 20 and the rod 19, have been traditionally been formed from similar materials, in particular, stainless steel. However, if the bush 20 and rod 19 both formed from stainless steel, the bush 20 and rod 19 wear on each other and may suffer from galling or cold welding, for example, the sliding of the rod 19 relative the bush 20 may cause surface damage which may result in high point protrusions on one or both of the rod 19 and bush 20 which may rub earning an increase in friction or ultimately bind with one another so as to adhere or freeze the rod 19 and bush 20 with one another.

[038] To address the problem of galling, in this example, the rod 19 is formed from a steel or iron based alloy and the bush 20 is formed from a copper based alloy. However, it should be appreciated that the configuration could be reversed with the rod 19 being formed from the copper based alloy and the bush 20 being formed from the steel or iron based alloy.

[039] By using a combination of dissimilar steel based alloy and copper based alloy materials, it has been advantageously found that galling or cold welding is substantially inhibited which in turn inhibits friction or adhesion between the rod 19 and bush 20. This allows the tight fit of a maximum 0.4 mm concentric gap to be achieved whilst ensuring PCT/AU2012/000202 WO 2013/126941 -13- the linear plunger rod 19 is able to freely move relative the hole 24 of the bush 20.

[040] Copper based alloys such as aluminium bronze, as is further described below, generally have a lower hardness relative to a steel based alloy such a stainless steel. Therefore, the softer material, in this case the aluminium bronze wears relative to the stainless steel and, in effect, functions as a lubricating material to inhibit friction between the sliding steel parts, namely the linear plunger rod 19 and the hole 24 of the bush 20. However, if the wear is excessive, over the life cycle of the actuator assembly 10, the maximum 0.4 mm concentric fit will be exceeded. Therefore, the copper based alloy, such as aluminium bronze, is generally required to be relatively soft in comparison of the steel based alloy, such a stainless steel, to inhibit friction whilst having sufficient wear properties to inhibit the maximum 0.4 mm concentric fit will being exceeded over the product lift cycle.

[041] In this example, it has been found that the most advantageous copper alloy is an aluminium bronze alloy. In a preferred example, the aluminium bronze alloy includes in the range of approximately 80 and 88 weight % copper and approximately 8 to 10.5 % aluminium. An example of the chemical composition and mechanical properties of the most preferred aluminium bronze alloy, ALLOY ALBC2C, are detailed below in Tables 1 and 2, respectively.

[042] The wear characteristics of aluminium bronze alloy was tested over a product life cycle of 1 million cycles and it was found that the wear between the linear plunger rod 19, when formed of stainless steel, and the hole 24 of the bush 20, formed from aluminium bronze alloy was maintained below the 0.4 mm maximum concentric gap in the range of 0.3 to 0.34 mm.

[043] Other copper based alloys such as manganese bronze alloys were also trailed over a product life cycle of 1 million cycles. However, whilst galling was substantially inhibited, it was found that manganese bronze alloy, wore too quickly, possibly as a result of the manganese bronze being too soft relative to the stainless steel. The wearing resulted WO 2013/126941 PCT/AU2012/000202 -14- in the 0.4 mm maximum concentric gap being exceeded.

Tin (Sn) 0.1 Max Lead (Pb) 0.1 Max Zinc (Zn) 0.5 Max Nickel (Ni) 1.0 to 3.0 Iron (Fe) 2.5 to 5.0 Aluminium 8.0 to 10.5 Manganese (Mn) 0.1 to 1.5 Copper (Cu) 80.0 to 88.0

Table 1: ALLOY ALBC2C - Typical Chemical Composition (wt%)

Ultimate Tensile Strength 500 MPa Minimun Elongation 15% Minimum Typical Hardness HB 120 Minimum

Table 2: ALLOY ALBC2C - Typical Mechanical Properties [044] In this example, the steel alloy is a stainless steel alloy having approximately at least 11 wt % chromium. More specifically, the stainless steel is 316 stainless steel, which has a well know composition, including at in the range of approximately 16 to 18 wt % chromium and in the range of approximately 10 to 14 wt % nickel.

[045] Furthermore, it is noted that stainless steel 316 has a hardness of approximately 217 (HB) which is substantially greater than the hardness of a copper based alloy, such as aluminium bronze which has a hardness of approximately 120 (HB). Accordingly, it is noted the reduction of friction by galling may be at least partially attributed to the dissimilar metals of the hole 24 of the bush 20 and linear plunger rod 19 being of differing hardness such that the relative softer component, such as the aluminium bronze, is able to wear rather than bind and lock with the harder component, such as the stainless steel. For PCT/AU2012/000202 WO 2013/126941 -15- example, the hole 24 of the bush 20 may be formed from the aluminium bronze and undergo wear relative to the plunger 19 which may be formed from a harder steel such as stainless steel. Of course, the wearing of the hole 24 of the bush 20 cannot be excessive as the 0.4 mm concentric gap may be exceeded in use compromising the frame proof properties of the housing 14. Therefore, it should be appreciated that the combination of aluminium bronze and stainless steel provides a balance between inhibiting friction, for example friction or locking cause by galling, between the hole 24 of the bush 20 and the plunger 19 whilst having appropriate wear properties to ensure that the maximum 0.4 mm concentric gap between the inside diameter of the opening 24 of the bush 20 and the outside diameter of the rod 19 is not exceeded over the life cycle of the product.

[046] It is also noted the bush 20 may be removable from the housing 14. Accordingly, when the bush 20 is formed from the copper based alloy and hence provides a wear component, the bush 20 may be easily replaced.

[047] Many modifications will be apparent to those skilled in the art without departing from the scope of the present invention.

[048] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates.

[049] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims (20)

1. The Claims:

   1. An actuator assembly for a vehicle, the assembly including a housing for containing an actuator for controlling vehicle function and a plunger which extends into the housing via an opening so as to be communicable with the actuator, wherein the plunger and the opening are each formed of dissimilar metal based materials so as to inhibit friction between the plunger and the opening, and wherein the fit between an inside diameter of the opening and an outside diameter of the plunger is sufficiency tight to inhibit the passage of fire or spark.
2. 2. The actuator assembly in accordance with claim 1, wherein one of the plunger and the opening is formed from a steel alloy and the other of the plunger and the opening is formed from a copper alloy.
3. 3. The actuator assembly in accordance with claim 2, wherein the copper alloy is an aluminium bronze alloy.
4. 4. The actuator assembly in accordance with claim 4, wherein the aluminium bronze alloy includes in the range of approximately 80 and 88 weight % copper and approximately 8 to 10.5 % aluminium.
5. 5. The actuator assembly in accordance with claim 2, wherein the steel alloy is a stainless steel alloy having approximately at least 11 wt % chromium.
6. 6. The actuator assembly in accordance with claim 5, wherein the stainless steel includes in the range of approximately 16 to 18 wt % chromium and in the range of approximately 10 to 14 wt % nickel.
7. 7. The actuator assembly according to claim 1, wherein the opening is defined by a bush fitted to the housing.
8. 8. The actuator assembly according to claim 1, wherein there is a maximum 0.4 mm concentric gap between the inside diameter of the opening and the outside diameter of the plunger.
9. 9. The actuator assembly according to claim 1, wherein the housing is a fire resistant housing formed from steel.
10. 10. The actuator assembly according to claim 1, further including a pedal adapted to mechanically communicate with the plunger, the pedal being moveable between a released position, in which the plunger is in a retracted condition relative the opening and a depressed position, in which the plunger is in an extended condition extending relative the opening into the housing.
11. 11. The actuator assembly according to claim 10, wherein the pedal is pivotally coupled to the housing.
12. 12. The actuator assembly according to claim 10, wherein the pedal supports a bearing which is arranged to bear on an end of plunger so as to reduce lateral forces applied from the pedal to the plunger.
13. 13. The actuator assembly according to claim 10, wherein the end of the plunger includes at least one collar dimensioned to provide an end of travel stop for the elongate rod.
14. 14. The actuator assembly according to claim 13, further including a spring arranged to return the pedal to the released position.
15. 15. The actuator assembly according to claim 14, wherein the spring is arranged between the housing and the collar of the plunger such that the elongate rod is urged toward the retracted condition which in turn urges the pedal toward the released position.
16. 16. The actuator assembly according to claim 15, wherein a seal is provided between the collar and the housing to cover the elongate rod and opening.
17. 17. The actuator assembly according to claim 16, wherein the seal is provided in the form of a flexible cylindrical boot concentrically arranged around the elongate rod so as to extend between the collar and the housing.
18. 18. The actuator assembly according to claim 17, wherein the boot includes an aperture to allow the passage of a gas into and out of the boot.
19. 19. The actuator assembly according to claim 18, wherein the aperture is fitted with a breather assembly.
20. 20. The actuator assembly according to claim 19, wherein the breather assembly includes at least one of a filter and a silencer.