AU757765B2 - Powered trailer jacking system - Google Patents

Description

PCT/AU00/0 0 1 5 3 WO 00/51859 1 Title powered trailer jacking system Field of Invention The present invention relates to landing gear (alternatively known as jacking legs) for articulated trailers.

Background Art Landing gear for articulated trailers allows the raising, XLanding gear for a: n of the trailer in lowering and support of the forward end of e er the engagement and disengagement from the prime mover (alternatively known as the tractor or truck) and allows the trailer to be freestanding whilst not in transit. In Smost instances the trailer itself is decoupled from a prime most nstand then recoupled to either the same prime mover or an another depending on the logistics appropriate to the use.

A typical scenario is where a trailer is delivered to a loading dock for loading. The trailer will typically be loaded up to twenty tonnes in weight, and in some instances up to twenty five tonnes, on one trailer. The prime mover positions the trailer in the loading dock. The operatively will de-latch the kingpin from the turntable (alternatively known as the fifth wheel) and disconnect the service lines.

The operator will then manually lower the legs of the landing gear. First the landing gear will be lowered to ground level in the higher speed selection of the typically two-speed geared landing gear arr angement once engaged with the ground the operator generall has tion e other than to change to the lower speed selection where the operator will enjoy the significant increase in mechanical advantage afforded by the higher gear ratio. T e oe o will then with significant effort raise the forward end on the trailer to clear the trailer kingin from the turntable of the prime mover. Once the trailer king pin is clear of II WO 00/51859 PCT/AUOO/00153 -2the prime mover turntable the prime mover can be driven clear of the trailer to leave the trailer freestanding.

The prime mover is then typically utilised elsewhere in a more productive role than being idle whilst the trailer is loaded.

The trailer will then be loaded which may take a portion of an hour or it may take several days. Once the trailer is loaded a prime mover will then return to the trailer for the removal from the loading dock. In many instances the prime mover will not be the same unit. In such cases the turntable height may not be identical or in other instances due to the poor stability of the ground on which the landing gear rests the trailer may have sunk. In either of these instances the height of the trailer will need to be adjusted to mate with the prime mover. The operator has the onerous task of manually winding the trailer either up or down to the necessary height. Once the trailer is at the correct height for engagement with the prime mover the operator can then locate the prime mover under the trailer, mating the kingpin with the turntable.

To prepare the trailer for transport the legs are manually raised in low speed until they are once again clear of the ground. Having cleared the ground the weight of the loaded trailer is transferred from the landing gear to the prime mover this then allows the landing gear to be changed by the operator to high speed for the legs to be raised to their full height. Raising to full height is necessary to allow ground clearance for traveling both on the road system and in some instances off the road system. Most known landing gear utilises a two-speed operation and typically the increase in mechanical advantage enjoyed in low speed is in the order of ten to one over the high speed. Even with the advantages afforded by the two-speed operation the time to couple a trailer with a prime mover will find 15 minutes as not atypical. This is particularly PCT/AUO01/00153 WO 00/51859 3 so when a trailer is loaded to its limits which generally requires the operator to rest due to the physical fatigue associated with the manual effort required.

There are several teaching of prior art documenting many There are several teachngs t to existing variations of powered drives thatcan be added t existing landing gear jacking legs at either the time of installation of the leg or a subseuent time. S patent number 5,451,076 to Burkhead, U patent number 5,299,829 to Rivers, Jr, et al, US patent number 5,050845 Aline, et and US Patent number 5,004,267 to Busby teach of a pneumatic motor to provide the necessary motive force to rotate the crank shaft (drive shaft) of the landing gear prior art. Us Patent number 4,466,637 to Nelson teaches of a drive motor such as an electric motor whilst we learn from US patent 4097840 to Chappelle of an electric e motor. It is noted that all of this prior art has existed for some time yet there is no significant commercialisation of this art. The pneumatic teachings have not beenf their accepted due their complexity and expensive nature of their accepted due their cop o teachings of pneumatic componentrY The prior art teachings of nemactic is cumbersome, weight and dated in electrical A the prior art tends to be overly complex technology. All the to all commercial landing and does not readily mount up o othe truciing gear currently available and used within the trucking industry. Most of the prior art requires a strong dependence onthe ustry.rovision of power from the prime mover, ndence eired t o b e coup led to the that is, the prime mover is required to trailer for the prior art to function.

It is these problems that have brought about the present invention.

Summary of the Inventiof According to the present invention there is provided a demountable drive mechanism for the landing gear of a semi- 1 WO 00/51859 PCT/AUOO/00153 -4trailer, the landing gear including legs that are extendable and retractable by rotation of a drive shaft through a gear mechanism, the drive shaft being axially displaceable to change the ratio of the gear mechanism, the drive mechanism comprising an electric motor having an output shaft adapted to be coupled to the drive shaft of the landing gear assembly, the electric motor being coupled to the landing gear through a torque arm so that the electric motor can impart torque to the drive shaft, means to axially displace the drive shaft to change the gear ratio, and means to control operation of the electric motor and axial displacement of the drive shaft.

Description of the Drawings Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 is a side elevational view of a truck and trailer, Figure 2 is a side elevational view of the trailer when detached from the truck, Figures 3a and 3b are elevational views of a common form of trailers landing gear used with the trailer of Figure 2, Figure 3c is a perspective view of a gear change mechanism of the landing gear of Figures 3a and 3b, Figure 4 is a side elevational view of landing gear in accordance with an embodiment of the invention, Figure 5a is a side elevational view of part of the landing gear of Figure 4 in a first speed mode, Figure 5b is a side elevational view of the landing gear in a second speed mode, Figure 6 is an exploded perspective view of the landing gear, Figure 7 is a diagram of the circuit associated with the landing gear, Figure 8 is a perspective view of a landing gear with N I -I PCT/AU00/ 0 0 15 3 WO 00/51859 5 demountable drive system in accordance with the second embodiment, ew of the landing Figure 9 is an exploded perspective view of the landing gear of Figure 8, Figure 10 is an end on elevation view of a gearbox of the landing gear shown in Figure 9, Figure 11 is a cross sectional view taken along the lines 11-11 of Figure Figure 12 is a cross sectional view taken along the lines 12-12 of Figure Figure 13 is a cross sectional view taken along the lines 13-13 of Figure 10, Figure 14 is a cross sectional view similar to Figure 13 illustrating a limit switch operation, and Figure 15 is a schematic illustration of the wiring associated with the circuit of the second embodiment Detailed Description of the Embodiments The use of landing gear for trailers according to the present invention is illustrated in Figures and 2.

Figure 1 the landing gear 100 is illustrated in the position it occupies when the truck T and trailer 1 are in motion. In Figure 2, the landing gear00 iler e in the position it occupies to upport the trailer 1 when the prime mover (truck T) has been decoupled from the trailer 1.

3b a conventional well known As shown in Figures 3a and 3b, a conventional well knwn form of landing gear includes a pair of telescoping legs 101 and 102. Each leg includes an upper portion 2, 3 and a lower portion 4, 5 which telescopes into the upper portion 2 or 4 respectively. Each upper portion 2 and 3 is secured one to a side of the trailer chassis 1 with multiple bolts 9. The upper portions 2 and 3 of the telescoping legs are braced to each other with crossbracing members 6 and 7.

Each upper portion 2 and 3 of the telescoping legs 101 and PCT/AU00/0 0 1 53 WO 00/51859 6 102 respectively is braced to the chassis by diagonal bracing members 8.

The driver's side leg 01 of the landing gear houses a two- The driver's side leg 101 generally as 103 as speed reduction gear head illustrated general as 103 as illustrated in Figures 3c. In the conventional mode of operation of the landing gear, the legs 01 and 102 are operated by a manual crank handle 10 which is removably attachable to the drive shaft 13 via a bolt. The leg 101 which houses the two-speed gear head 103 could also be mounted on the non driver's side.

Figure 3c illustrates the operation of the two-speed reduction gear 103. It is preferred that the gear head 103 is housed within the upper telescoping leg 2. in an alternative form, the gear head 103 is housed external to the upper leg section 2 and is arranged such that the gear the upper leg section 2 and For clarity reduction in one mode is not directly coupled. For clarity the gear head housing is not shown in Figure 3c. The purpose of the mechanics of the gear train is to afford the rpoe otheechadv ereuired when a human significant mechanical advantage required wea ha operator is manually raising or lowering a loaded trailer.

The two-speed feature of the drive head of the landing gear is to allow a rapid motion of the telescoing legs 4 and in either the up o down mode whilst they are not loaded with the trailer and/or its load.

The motive power for raising or lowering the telescoping legs 4 and 5 is usually from a human source or from a powered source. In the arrangement as shown in Figure 3a, the landing gear is powered by a human operator. The rotary motion (winding) of the crank handle 10 is imparted to the drive shaft 13 through the coupling bolt 12. When the drive shaft 13 is in th inboard position not shown in Figure 3c, the gear head is in the high speed mode where Figure 3c the gear eis in toe the least mechanical advantage is provided. The power is transmitted from drive shaft 13 to the spur gear 14 which (U VVlOJ7 PCT/AU00/00153 WO 00/51859 7 is solidly attached to the drive shaft 13. In the inboard is solidly attached to th d r tedainternally within the position the spur gear 14 is nested internall within the spur gear 18 and provides a direct drive to spur gear 18 which is solidly mounted to the shaft 19. The bevel gear 20 is also solidly mounted to the shaft 19. Drive is therefore from spur gear 18 throgh shaft 19 to bevel gear Bevel gear 20 is permanently engaged with the mating bevel gear 21 which is affixed to the screw shaft 22.

Screw shaft 22 provides the vertical motion to the telescoping legs 4 and 5 (not shown) via a mating nut (not shown) which is attached to the telescoping legs 4 and When transmission of power in low speed with the higher mechanical advantage is required the drive shaft 13 is in mechanical advantage is r e qu r e 3c and lears the the outboard position shown in Figure 3c and clears the spur gear 18 and engages with the spur gear 15. Spur gear is fixed to the lay shaft 16 which has gear 17 fixed to it. The drive is transmitted from drive shaft 13 to spur gear 14 to spur gear 15 through lay shaft 16 to spur gear gear 1 4 to spu r gear18. The tranmision of power from spur 17 to spur gear 18. ht 2 i in high speed gear 18 to the screw shaft 22 is identical as in high speed as described above.

electrical motor This invention relates to the use of an electrical motor and associated control mechanism to provide drive to the output shaft to operate the landing gear. The control mechanism also provides means to efect the speed change mechanism by displacing the output shaft axially.e e assembly has been specifically designed to be retrofitted to the most common forms of landing gear Ths, the assembly is adapted to drive the output shaft both in term of rotation and axial displacement for speed change. The landing gear assembly and speed change mechanism described above is the commonly used system in the trucking industry ccording to one configuration of the apparatus according to the present invention shown in igures 4 to 7, the to the present invention shown in n WO 00/51859

PCT/AUOO/

0 0 15 3 8 manual crank handle 10 and is not used and motive power is provided by an electronically controlled geared electric motor. preferably electrical energy is the power source and it is derived and converted from the prime mover's own internal combustion engine which is ultimately provided by the fuel that energises that said engine. In alternative preferred embodiments, electrical energy is externally provided from other than the prime mover. A preferred power source for primarily stationary applications is the local civilian electricity grid. This power source is converted to the mechanical energy required to raise and lower the trailer complete with load as necessary. For the purpose of describing the invention electrical power is provided by the prime mover's own reticulated low voltage electrical system.

Energy is stored within the trailer in preferably two batteries 36 and 37. Two batteries are used to provide the necessarY twenty-four volt operating electric potential that is used to power the electric motor 23. The batteries 36 and 37 are deep cycle heavy duty batteries that are capable of withstanding the duties appropriate to this rigorous invention. From Figure 7 it can be seen that the batteries 36 and 37 are electrically in series and are coupled together with conductor 71 being connected to the negative and positive terminals of batteries 36 and 37 respectively. The positive terminal of battery 36 is connected to the electronic controller 24 with conductor 72 via the single pin connector 81. The conductors 70, 71 and 72 are fixed to the terminals of the batteries 36 and 37 with bolts 38. The negative polarity of the battery 37 is coupled to ground, being the trailer chassis, via conductor These batteries 36 and 37 are mounted within a battery case 40 which is secured to the landing gear. The battery case is enclosed with a sliding lid 43 which is capable of being secured through the inclusion of a lug 44 to prevent theft or tampering. The batteries 36 and 37 are snugly WO 00/51859 PCT/AUOO/0 0 15 3 9 located by the use of a pliant membrane 39 that insulates the batteries 36 and 37 from the battery case 40. This membrane 39 could typically be an expanded urethane sheet material. The battery case is secured to the leg of the landing gear with multiple self taping screws 42 which are accessed when the batteries 36 and 37 are not in place via the clearance apertures 41. Alternative methods, locations and fixing for the batteries 36 and 37 may be appropriate for certain applications and as such are included in this invention. To minimise the distances of the high current electrical conductor 72 the batteries 36 and 37 are mounted adjacent the demountable geared motor assemblY 104. The arrangement of batteries 36 and 37 battery case sliding lid 43, lug 44, pliant membranes 39 and self taping screws 42 form the battery assembly 105 as depicted in Figures 5a and The electronic controller 24 is mounted adjacent the electric motor 23 with multiple bolts 34. The electronic controller 24 chassis is earthed to the trailer chassis through conductor 73. The electric motor 23 is connected to the electronic controller 24 through conductors 79 and via the two pin connector 82. The raise/lower switch 48 is directly connected to the electronic controller 24 through conductors 76 and 77. The common terminal of the raise/lower switch 48 is connected to earth via the conductor 78. The positive polarity of the trailer derived power supply (not illustrated) to the electronic controller 24 is feed through conductor 75 via the two pin connector 83 with the negative polarity being connected to ground through conductor 74.

In the embodiment as illustrated in Figure 7 the brake air pressure interlock switch 64 is connected to the electronic controller 24 through conductor 84 via the two pin connector 83. The brake air pressure interlock switch 64 common terminal is connected to ground through conductor ~r.n.o i. i. PCT/AU00/00153 WO 00/51859 10 7 two bi-directional electric As illustrated in Figure 7 two directi electric solenoids 54 and 55 are connected to the electronic controller 24 through conductors 86 and 87 with the third necessary conductor from the electric bidirectional solenoids 54 and 55 connected to earth thrugh connected 88. The turntable clear interlock switch 65 is connected 88. The turntable car hrough conductor 91 with to the electronic controller The legs up the common earthed through conductor 92.

the comon eared o the electronic interlock switch 66 is connected to the electron earthed controller 24 through conductor 89 with the common earthed ntro conductor 90. The two bidirectional solenoids 54 through conductor 90. e interlock switch 65 and the and 55, the turntable clear interloc c ndto the legs up interlock switch 66 are pin connector te.

electronic controller 24 via the As one of the objectives of this invention is to be universally mounted, either a twelve volt or a twenty four volt trailer operating voltage can be received by the electronic controller 24. The electronic controller 24 electronic controller range from 10 volts will typically accept a voltage inut ranger to t to 30 volts DC which is electronically converted tO the necessary battery charging voltage to ensure the batteries are maintained at their peak operating condition Charging is achieved at the operators discretion by providing the is achieved at the operators tenuconnector 83 of trailers reticulated voltage to the input connector 83 of the invention through conductors 75, 74 and 73. The electronic controller 24 includes circuitry to prevent 30 failure of any of the electronic components should the failure of any s y (not illustrated) be batteries 36 and 37 or supply oltage ot illtrat inadvertently connected in the reverse polarity.

indication from the The electronic controller 24 receives indication from the 35 raise/lower switch 48 as to the desired operation. This is raise/lower switch 48 as t conductors 76 or 77 to achieved by effectively connecting conductors 76 or 77 to earth via the raise/lower switch 48 and conductor 78 for i WO 00/51859 PCT/AUOO/001 3 11 raise and lower modes respectively. The electronic controller 24 uses the indication as abovementioned from raise/lower switch 48 to undertake the necessary high current voltage switching to operate the invention from the off to either the raise or lower modes. In effect the voltage as fed through the conductors 79 and 80 via connector 82 to the electric motor 23 is the battery voltage (in series) for the raise mode with the polaritY being reversed across the conductors 79 and 80 and the electric motor 23 for the lower mode. connector 82 is included to ensure that the electric motor 23 can be readily disconnected in the event of failure of the electric motor 23.

In this embodiment the electronic controller 24 includes an electronic circuit to ensure the electric motor 23 current is limited to a set value. If the load is such that the electric motor 23 attempts to use excessive current the electronic controller will de-energise the voltage being feed to conductors 79 and 80. The supply will not be reenergised until both a short time delay has passed and the raise/lower switch 48 has been cycled through the off position. Such over current conditions will arise where the end of the stroke of the landing gear legs 4 and 5 has been reached and the electric motor 23 is left oerating.

preferably when the landing gear legs are being lowered in high speed the invention allows the operator to undertake other routine duties as the overload protection component of the invention will stop the motor once the telescoping legs 4 and 5 have engaged the ground. The electronic controller 24 is configured so that the change from high speed to low speed will take place automaticallY as described elsewhere in these teachings.

From Figure 7 the raise and lower modes can be understood.

The raise/lower switch 48 when in the raise mode effectively connects the conductor 77 to ground through I-1. pCT/AUoo/001 3 WO 00/51859 12 -7t Whereas in the raise/lower switch 48 and conductor 78 Whereas in through lower mode the conductor 76 is conducted t round through raise/lower switch 48 and conductor 78. The raise/lower switch 48 as described herein has three ositions. In the raise position the raise mode is energised,in the lower position the lower mode is energised and in the central off position the electric motor 23 is not activated. The raise/lower switch is a spring return centralising type switch.

1 0 illustrates a trailer brake air pressure interlock switch 64. This switch is closed when the brake air pressure drops to a oint where the trailer brakes (not illustrated) are positively engaged. The inclusion of this element of the circuit design is optional and at the discretion of the operator as some hindered by the inclusion of such an interlock.

In an alternative embodiment (not illustrated) the conductor 84 is connected to ground. If the brake air pressure interlock switch 64 is not installed the conductor 84 is required to be connected to ground, as such the electronic controller 24 will interpret the imaginary switch as being on.

n this embdiment sensors and actuators are included along with electronic control circuitry to allow the gear change in the trailer landing gear to be undertaken automatically The turntable clear interlock switch 65 and the legs up interlock switch 66 are used to sense the completed lower and raise automatic cycles respectively of this embodiment and raise automatic As described elsewhere in these of this invention. As oids 54 and teachings the bi-directional electric solenoids 54 and are used to activate the change in gears within the trailer landing gear gear head 103 The electric circuit as herein described is one of several

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pCTIAU00O00153 WO 00/51859 13 possible solutions to provide an operating system in a twelve or twenty four volt environment. other options and variations, such as relays, may be equally suitable and inclusive in this invention.

The demountable geared electric motor assembly 104 comprises a drive motor that is preferably a direct current electric motor. The electric motor 23 is close coupled to a worm reduction gearbox 31. However it is understood that other reduction mechanisms could be deployed. Planetary gear trains, spur gear reduction and chain drives and combinations thereof are all considered suitable alternatives to the worm reduction gearbox described herein. The output male shaft 27 of the motor is positively coupled via a key 28 to the female input shaft of the gearbox 31. The electric motor 23 is secured to the mating gearbox flange 29 with multiple bolts 30. The gearbox 31 includes a hollow output shaft which is sized to be a slide fit on the landing gear drive shaft 13. This be a slide fit on theto the next size may vary from one commercial landing gear to the next.

The demountable geared assembly is mounted on and supported by the landing gear drive shaft 13 and includes a collar 32 which is an interference fit in the gearbox 31 hollow output shaft. The existing landing gear drive shaft 13 has a new hole 35 added to accept the pin 33 which passes through both the drive shaft 13 and the collar 32. This pin 33 is a press fit within the collar 32 and the hole A torque arm 45 is supported from the upper leg 2 via bolts 46. This torque arm 45 is a slide fit in the pliable bushing 26 which in turn is fitted within a fork flange protruding from the base of the electric motor 23 housing.

The torque arm 45 is preferably made of spring steel. The entire demountable geared electric motor assembly 104 includes and is enclosed within a cover 47. The cover is secured to the gearbox 31 housing with multiple bolts 53.

Spacers 52 are used as appropriate between the cover 47 and the gearbox housing. The electronic controller 24 is PCTIAUOO/00153 WO 00/51859 14 23 and is supported from housed adjacent the electric motor 23 and is supported from the cover 47 with bolts 63. Electrical conductors as elsewhere described extend from the electronic controller 24 to the battery assembly 105, the electric motor 23, the trailer power supply (not illustrated) and other field devices all as illustrated in the circuit diagram of Figure 7.

In this embodiment the demountable geared motor assembly 104 includes two bi-directional electric solenoids 54 and S104 incThese are locateo diametricall opposed about the drive These are located diametrcallytric solenoids 54 and shaft 13 and the bodies of the electrie s rolen 54. The are secured to the cover 47 with multiple screws 56. The are secured to the cover are connected to the electric solenoid shafts 57 and 58 are c eed t the landing gear upper leg 2. The landing gear upper leg 2 has a solenoid coupling bracket 61 which is secured to the landing gear upper leg 2 with screws 62. The electric solenoid shafts 57 and 58 are connected to the solenoid coupling bracket 61 via a pins 59 and 60. The electrical conductors as illustrated in Figure 7 connect the electric solenoids 54 and 55 to the electronic controller 24.

2> has a high energy density The preferred electric motor 23 has a high energ density ratio and is ideal in this application. It is compact and relatively light in weight which is a criterion in most freight applications. Drive from the electric motor 23 is freight aplications. the key 28 which in transmitted to the gearbox 31 through the key 28 which in turn is transmitted to the landing gear drive shaft 13 via the collar 32 and in 33. In addition to transmitting the the collar 32 and pin 33. the lateral fixing of the drive torque the pin 33 provides the lateral f the demountable geared electric motor aelyding gear drive landing gear. The torque applied resisted by the tore shaft 13 by the electric motor 23 is resisted by the torque haft 13 b he tore r i specifically so placed to react arm 45. The torque arm is the demountable to the torque applied in operation of the demountable geared electric motor assembly 104 to the landing gear drive shaft 13. The material used to manufacture the torque li:1 ~I~-ilril~~~i~i~l~i:i! i WO 00/51859 PCT/AU00/001 53 15 arm 45 provides a degree of flexibility. This flexibilitY allows any shock loading to the drive assembly to be minimised. When the demountable geared electric motor assemblY 104 is laterally moved as illustrated in Figures 5a and 5b the torque affords a minimal rotational allowance to allow the meshing of the gears as the high speed or low speed is engaged. To allow for the lateral movement when the gear change is undertaken the torque arm 45 is a slide fit in the pliable bushing 26.

The cover 47 provides the necessary minimal guarding required to ensure operator safety as well as providing a base for the mounting of the bi-directional electric solenoids 54 and 55 and the electronic controller 24. The cover 47 accommodates the mounting of the raise/lower switch 48.

In the embodiment of Figures 5a and 5b the bi-directional electric solenoids 54 and 55 are used to move the entire demountable geared electric motor assembly 104 inclusive of the drive shaft 13 laterally, that is, inboard and outboard. This lateral movement of the whole drive system reflects the change from high speed to low speed or vice versa within the geared head of the existing landing gear.

The force applied by the solenoids in conjunction with the rotational flexibility provided by the torque arm are sufficient to ensure the speed change is positive and complete. Figure 7 illustrates bi-directional electric solenoids 54 and 55 of this embodiment.

According to another embodiment of the invention (not illustrated) the gear change from high speed to low speed and back again within the landing gear is carried out independent of the drive system. The geared electric drive motor assembly position is fixed and the landing gear drive shaft 13 is acted on by a mechanism that allows the change from high speed to low speed independent of the geared WO 00/51859 PCT/AU00/001 53 16 electric motor drive assembly. In this embodiment the coupling between the landing gear drive shaft 13 and the demountable geared electric motor drive assemblY 104 is a keyed slide fit of the landing gear drive shaft 13 within the hollow shaft of the reduction gearbox 31.

A typical scenario for an automatic down cycle is initiated, when the system is not already operating, by the operator flicking the raise/lower switch 48 to the lower position for approximately one second. The electronic controller 24 then activates the bi-directional solenoids 54 and 55 to ensure the gear head 103 is in the high speed mode. The lower legs 4 and 5 are then lowered by the electric motor 23 as elsewhere described. When the landing gear lower legs 4 and 5 become engaged with the ground the electric motor 23 current eventually reaches its defined upper current limit and the electric motor 23 is stopped by the electronic controller 24. It should be noted at this point that in some circumstances the trailer and load may be so insignificant that the electric motor 23 current upper limit is not reached and the landing gear lower legs 4 and 5 can continue to be lowered in the high speed mode.

The bi-directional solenoids 54 and 55 are activated to change the gearing to the higher ratio where the improved mechanical advantage is enjoyed. Upon this gear change being effected the electric motor 23 is again energised to continue lowering the landing gear. The automatic lower cycle is concluded on reaching one of three conditions: The first condition being the electric motor 23 current has again reached the defined upper limit.

The second condition being that the turntable clear interlock switch has been activated.

The third condition is that the raise/lower switch 48 has been flicked to the raise position for approximately one second.

The automatic raise mode of this embodiment is activated, WO 00/51859 PCT/AUOO/0015 3 17 when the system is not already operating, and the raise/lower switch 48 is flicked to the raise position for approximately one second. The electronic controller 24 then activates the bi-directional solenoids 54 and 55 to ensure the gear head 103 is in the low speed mode. The lower legs 4 and 5 are then raised by the electric motor 23. When the turntable clear interlock switch is deactivated the electronic controller 24 stops the electric motor 23 after a short predefined period of time. The bi-directional solenoids 54 and 55 are activated to change the gearing to the lower ratio where the increased operation speed is enjoyed. Upon this gear change being affected the electric motor 23 is again energised to continue raising the landing gear. The automatic raise cycle is concluded on reaching one of three conditions: The first condition being the electric motor 23 current has again reached the defined upper limit.

The second condition being that the legs up interlock switch 66 has been activated.

The third condition is that the raise/lower switch 48 has been flicked to the lower position for approximately one second.

In this embodiment of automatic gear changing there will be times when the landing gear lower leg 4 and 5 extension needs to be adjusted. This is achieved by holding the raise/lower switch 48 in either the raise or lower position for a period greater that two seconds. The electronic controller 24 will recognise this holding of the raise/lower switch 48 and not continue in an automatic mode but only raise or lower the legs for the period that the raise/lower switch 48 is held in either the raise or lower position respectively. Manual gear change can still be undertaken and is consistent with the non-automatic gear change embodiment in that the gear change is effected by the operator manually acting on the demountable geared motor assembly 104.

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PCT/AU00/00 153 WO 00/51859 18 According to yet another embodiment (not illustrated), the gear change is manually operated.

In this embodiment the gear change is manually undertaken by the operator acting on the demountable geared motor by the operator act ng handles 50 and 51.

assembly 104 which includes operator handles 50 and 51table The operator either ushes or pulls the whole demountable geared motor assembly 10 inboard or outboardeecting the i0 laterally shifting the drive shaft 13 and effecting the gear change in the gear head 103 of the landing gear.

A typical scenario of the operation of the system in a nonautomatic mode is described as follows. The operator having positioned the trailer in the area ready for decoupling from the prime mover will, after having secured the brakes on the trailer, ensure the gear head is in the the brakes on t r a i l e r nthis position the raise/lower high speed disposition. In this p osition tan the switch 48 will be activated to the lower position and the 0 inner telescoping legs 4 and 5 of the landing gear will uickly lower to the ground The operator has the option i c k l y lo eohehisoccu or he may elect to to wait at the legs until this occurs or he may elect to undertake a few other duties that are part of his routine. When the legs make contact with the decoupling routine. es not return t h e raise/lower ground if the operator does not return i or switch 48 to the off position the electronic motor controller 24 will prevent the drive from over loading and switc itsraise/lower switch will then need switch itself Off- The raise/rower to be returned to the central off position. After engaging to be returned to themceeh change to low the ground the operator will then make the change to low speed by grasping the handles 50 and 51 and dertaking the minimal lateral movement to engage low speed. In low speed a significant mechanical advantage is provided by the landing gear gear head 103 and the oerator can now reenergise the system in the lower mode by activating the energise the system in h 4 Once the trailer lower mode of the raise/lower switch 48. nce the trailer has been raised so that the trailer kingpin is clear of the 4 WO 00/51859 PCT/AUOO/0015 3 19 prime mover turntable the raise/lower switch is returned to the off position. When the operator has undertaken all other service disconnection's between the prime mover and the trailer the prime mover can be driven clear and the trailer left as a freestanding unit.

When the freestanding trailer is required to re-coupled to a prime mover the operator will assess if the trailer is at the appropriate height. If not then the operator will ensure the low speed is engaged within the gear head of the landing gear. The height of the trailer can be adjusted by operating the raise/lower switch 48 as appropriate. Once the trailer is at the correct height the prime mover can be located under the trailer. The trailer landing gear legs 4 and 5 can now be raised to be clear of the ground by operating the raise/lower switch 48. Once clear of the ground the operator can engage the high speed mode within the landing gear and continue to raise the legs until they are in the fully retracted position. Once the legs are fully retracted in the raised position the raise/lower switch 48 is returned to the central off position. If the operator does not turn off the raise mode before the landing gear has reached its uppermost position the electronic controller 24 will take over and de-energise the electric motor 23. After completing all other couplings between the trailer and the prime mover the trailer is then ready to be removed from its freestanding position.

As in all mechanical and electrical mechanisms failure can occur and the system caters for this in that the demountable geared electric motor assembly 104 is readily removed. The procedure for removal of the drive assembly is as follows: The electrical connectors 81 and 83 are disconnected, in an alternative embodiment connector 93 it is also disconnected. The pin 33 is removed and the whole drive assembly can be demounted by sliding the assembly outboard and off both the landing gear drive shaft 13 and PCT/AU00/0 0 1 5 3 WO 00/51859 20 the torque arm 45. Once this is carried out the original manual crank handle 10 is remounted to the landing gear drive shaft 13 with a bolt nut (not illustrated). The operator can then operate the landing gear in the traditional manner. The manual crank handle 10 is separately stored on the trailer in the advent that a failure was forthcoming.

St-o 15, a more compact In the embodiment shown in Figures 8 to a more compact t drive the landing gear.

system 200 is used to driebed ve y utilising is similar to the embodiments described above by utilisng an electric motor 201 that is supported in a housing 202 that in turn supports a gearbox 203 positioned between the output shaft 204 of the electric motor and a drive shaft 205 which is in turn coupled to the drive shaft 13 of the landing gear. As shown in Figure 8 the motor 201 is positioned with its axis parallel tO the drive shaft 205 and the gearbox 203 is located at the outboard end 207 of the assembly. The lower rear face of the ouing 202 has a 20 projecting spigot (not shown) that is a sliding fit within projecting spigot rod 209 that is secured a torque arm in the form of a steel rod tat ec to the leg of the landing gear via an angled bracet 206.

The torque arm 209 facilitates transfer of torque from the electric motor 201 to rotate the shaft 13 of the landing gear. This embodiment also includes an automatic gear change facility, except in this casethe gear change facility is pneumatically driven by the air pressure that emanates from the trailer's air braking system.

30 As shown in Figures 9 and 11, the housing 202 is split into As shown in gures211 that can be bolted to a two parts, namely a front cover 211 t e bo rear part 212 of the casing that houses the gearbox 203.

The upper part of the housing defines a sub-comartment 215 which is sealed from the remainder of the housing and which contains a circuit board 216. A main oerator nel 217 is attached to the exterior surface of the sub-compartmented 215. The output shaft 205 of the gearbox has an enlarged 2- pCTIAUoo00153 WO 00/51859 21 hollow spigot 218 which extends co-axiallY into a cylindrical drum 220 that is sealed by an end plate 221 to define an air chamber.

The input shaft 13 of the landing gear locates coaxially in a fixed collar 225 that is mounted to the leg of the landing gear. The collar 225 steps down to an elongate sleeve. The sleeve 226 has an axially hollow projection 227 that terminates in an annular face plate 230. As shown 227 that terminates in an locates within the in Figures 11 and 12, the input shaft 13 ocate e spigot 218 of the outpUt shaft 205 of the gearbox 203. As spigot 218 of e t t 218 and input shaft 13 are shown in Figure 12, the spigot 218 vd inut shaft 13 are secured together by a tranverse inas axial dilacement to transfer of axial rotation as well the input shaft of the landing gear.

The arrangement is such that the housing 202 together with the electric motor 201, gearbox 203 and drum 220 can move axially relative to the collar 225, sleeve 226, limit switch actuating arm and face plate 230 to displace the input shaft 13 to effect a speed change. The face plate 230 contacts the interior of the drum 220 and extei the spigot 218 via ring seals 232, 233 to divide the air chamber into two sub-chambers 235, 236 on either side of the face plate 230. An rng seal 234 also acts between the end plate 221 and the sleeve 226 allows relative movement whilst maintaining air pressure within the sub-chamber 236.

The comartment of the houing 202 that houses the gearbox The compartment of the housingtrailer's air brakes to act 203 can be pressurised from the trailer's air brakes to act as an air pressure reservoir that can contain enoughange pressurised air to facilitate operation of the speed chnge mechanism. The air pressure within the gearbox housing 202 mechanism. The air pressure 3 236 via solenoid is transmitted to the sub-chabers 235, 236 a The controlled valves 240, 241 own in Figure 12 and co13.ses a left hand valve 240 is shown in Figure 12 and comprises a PCTIAUOO00153 WO 00/51859 22 valve member 242 urged outwardly by a spring 243. The solenoid 154 drives the valve member 242 inwardl against the spring 243 to allow air to flow into the sub-chamber 235 on the left hand side of the face plate 230. In the neutral position, the spring 243 pushes the valve member 242 to the left as shown in Figure 12 which allows the subchamber 235 to vent to atmosphere through a small bleed aperture 248 shown in Figure 12. The sub-chamber 236 on the other side of the face plate can also bleed to 1 0 atmosphere via bleed aperture 249 and the other solenoid controlled valve 241 shown in Figure 13.

By actuation of either valve through the solenoids 154, 155 the sub-chambers 235, 236 are pressurised to cause the housing 202 to be displaced relative to the fixed sleeve 226 and face plate 230. This displacement of 22 to 25mm is 226 and face plate 230. The suball that is required to effect the speed change. The subchambers can be vented to atmosphere in the neutral positions of the valves to ensure that there is a simple opportunity for manual override should there be a lons of air pressure. The gearbox enclosureis an elegant means of air •ressure. that the speed providing a reserve of air pressure so t ith t the change mechanism can operate a number of times without the need for further pressurised air from the prime mover.

In this embodiment the pneumatic actuation of the speed change is at low pressure, approximatel 15i flexible compressed air is supplied to the housing 202 via flexible piping (not shown) from the existing compressed air system that is used to actuate the trailer's braking system. The air pressure is regulated to the desired low pressure by an inline pressure regulator. A check valve (not shown) is incorporated in the supply line to enure against inadvertent loss of air pressure from the housing. Whilst the housing of the gearbox 203 is used as a low pressure air reservoir, it is understood that a safety over pressure relief valve (not shown) is fitted to the ouing to ensure

I

WO 00/51859 PCT/AU00/00 1 53 23 against over inadvertent increase of air pressure within the housing that might blow the seals.

The narrow bleed apertures 248, 249 that cause the subchambers 235, 236 to vent to atmosphere in the neutral position of the valves are specifically designed to slow down the release of air to act as a device that cushions the travel of the face plate 230 in either direction.

It is understood that instead of using the gearbox housing 202 as an air pressure reservoir, a separate tank or cylinder could be utilised in line with the air supPlY.

The pneumatic system provides a smooth and positive speed change facility which can be finely tuned by controlling the air pressures to ensure efficient operation. The assembly has been specifically designed to be reduced to the competitive cost for a minimum weight and complexity.

As shown in Figure 14, a limit switch actuating arm 250 of offset section is solidly mounted on the collar 225 to extend towards the exterior of the drum 220. A pair of limit switches 167 and 168 are mounted on the circuit board 216 to be activated by contact with the end 251 of the arm 250 as the housing moves relative to the collar 225. As the axial movement of the system 200 reflecting a gear change is undertaken the actuating arm acts on the miniature limit switches 167 and 168. Miniature limit switches 167 and 168 are electrically connected to the circuit board 216 as described later in the specification.

A0 shown in Figure 15, energY is stored within the trailer in preferably at least one batterY 136. A batterY 136 is used to provide the necessary twelve volt operating electric potential that is used to power the electric motor 201. From Figure 15 it can be seen that the positive and negative terminals of battery 136 are connected to the circuit board 216 with dual conductor 170 and a multiple PCTIAUOO00153 WO 00/51859 24 core conductor 171 via a dual pin connector 181 and connector 186. The connector 186 is directly mounted on the circuit board 216. The dual conductor 170 is fixed to the terminals of the battery 136 with bolts (not shown).

The conductor from the positive polaritY of the battery 136 includes an in-line thermally acting fuse 137. The battery 136 is mounted within a battery cradle (not shown) which is secured to the landing gear 2.

The circuit board 216 is mounted within the housing subcompartment 215 of the system 200 and is located via a snug fit within two parallel slots on either internal side of the housing sub-compartment 215. The electric motor 201 is connected to the circuit board 216 through dual conductor 172 which is directly affixed to the circuit board 216.

The main operator panel 217 is electricallY coupled to the circuit board 216 with the multiple core conductor 173 via the circuit board 216 mounted connector 187. The positive and negative polarity of the trailer derived power supply (not illustrated) is coupled to the circuit board 216 through the dual conductor 178 via the multiple pin connector 189, the multiple core conductor 171 and the circuit board 216 mounted connector 186.

In the embodiment as illustrated in Figure 15 the brake air pressure interlock switch 164 is connected to the circuit board 216 through conductors 182, 179 and 171 via the connectors 191, 189 and 186. Two electric solenoids 154 and 155 are connected to the circuit board 216 through conductors 174 and 175 which are directly affixed tO the circuit board 216. The turntable clear interlock switch 165 is connected to the circuit board 216 through conductors 183, 180 and 171 connectors 192, 189 and 186.

The legs up interlock switch 166 is connected to the circuit board 216 through conductors 184, 181 and 171 with connectors 193, 189 and 186. The alternate operator panel 169 acts identically to the main operator panel 217 and is -1 '1 PCT/AU00/0 0 15 3 WO 00/51859 25 electrically connected in parallel with the main operator panel 217. The alternate operator panel 169 is connected to the circuit board 216 with the multiple conductors 177 and 176 and multiple connectors 190 an 188. Two industry standard miniature limit switches 16 an 168 are mountedting directly to the circuit board 216. Two light mitti diodes 194 and 195 are mounted directly tO the circuit board 216. Both diodes emit light through apertures in the main operating panel 217. Multiple pin connectors 186 and main operating panel 217 the circuit board 188 are mounted electrically directly t the ciar ocuit boardusing 216 and physically to apertures in the rear of the includedsing sub-compartment 215. onnectors 186 and 188 are included disc o n ectedto ensure that the system 200 can be readily disconnected in the event of failure of any of the componentsultiple conductors 171 and 176 and their associated Multiple conductors 171 endecively form connectors and downstream conductors effectively form electrical looms and are used to connect to all electrical electrical looms and are use 200 using nd the enclosed devices remote from the system 200 housing and the enclosed circuit board 216. The connectors 186 and 188 are environmentally sealed at the interface with the housing sub-compartment 215.

of various standard The control circuitry is made up of various standard industrial electrical and electronic omponents mounted directly on the circuit board 216. As one of the objectives of this system is to be universally mounted, either a twelve volt or a twenty four volt trailer operating voltage can be received by the control circuitry The control circuitry will typically accept a voltage input range from 10 volts to 30 volts DC which is electronically range from 10 volts te 0charging voltage to converted to the necessary battery charging voltage to ensure the battery 136 is maintained at its peak operating condition. This is achieved through the inclusion of an industry standard isolated flyback power converter which acts as a trickle charging circuit allowing the battery to be charged. Charging is achieved at the operator's WO 00/51859 PCT/AUOO/00153 26discretion by providing the trailer's reticulated voltage to the input dual conductor 178. Standard industrial relays which are mounted on the circuit board 216 are included to allow for the high current forward and reverse switching of the electric motor 201. The electric motor 201 current is monitored via the amplified voltage across a circuit board 216 mounted resistor and feed to the microprocessor.

Circuitry is included to prevent failure of any of the electronic components should the battery 136 or supply voltage (not illustrated) be inadvertently connected in the reverse polarity. The microprocessor which is mounted on the circuit board 216 is programmable and includes the logic to control the system 200. All the devices electrically connected to the circuit board 216 as described in this art provides either input to or is operated via outputs from the circuit board 216 and its microprocessor. The logic includes failure algorithms which are indicated by a light emitting diode 195. Light emitting diode 194 is used to indicate the auto/manual status of the system.

The circuit board 216 and its microprocessor receives signals from the main operator panel 217 or the alternate operating panel 169 indicating the desired operation. Each panel allows for the automatic raise or lower cycle to be initiated by activating the raise or lower buttons respectively. A stop button is also included on each operator panel 217 and 169 to allow for the immediate stopping of either automatic cycle. The control circuitry uses the indication as abovementioned from the main operator panel 217 and the alternate operating panel 169 to undertake the necessary high current voltage switching to operate the system from the of f to either the raise or lower modes. In effect the voltage as fed through the dual conductor 172 to the electric motor 201 is the battery voltage for the raise mode with the polarity being reversed across the dual conductor 172 and the electric motor 201 WO 00/51859 PCT/AUOO/00153 27 for the lower mode.

In this embodiment the control circuitry ensures the electric motor 23 current is limited to a set value. If the load is such that the electric motor 201 attempts to use excessive current the logic of the microprocessor will de-energise the voltage being feed to dual conductor 172.

The supply will not be re-energised until both a short time delay has passed and the stop button of the main or alternate operator panel 217 and 169 has been operated.

Such over current conditions will arise where the end of the stroke of the landing gear legs 4 and 5 has been reached and the electric motor 217 is left operating.

Preferably when the landing gear legs are being lowered in high speed the system allows the operator to undertake other routine duties as the overload protection component of the system will stop the motor once the telescoping legs 4 and 5 have engaged the ground. In this embodiment the control circuitry is configured so that the change from high speed to low speed can take place automatically as described elsewhere in these teachings.

From Figure 15 of this embodiment it can be seen that the control circuitry includes a trailer brake air pressure interlock switch 164. This switch is closed when the brake air pressure drops to a point where the trailer brakes (not illustrated) are positively engaged. The inclusion of this element of the circuit design is optional and at the discretion of the operator as some applications would be hindered by the inclusion of such an interlock.

In an alternative embodiment not illustrated the dual conductor 179 is connected together, that is, electrically bridged out. This allows for the brake air pressure interlock switch 164 to be eliminated from the system.

In this embodiment sensors and actuators are included along ^&ajg-.Mtf'*^ j-*ig- WO 00/51859 PCT/AU00/00 1 5 3 28 with the control circuitry to allow the gear change in the trailer landing gear to be undertaken automatically. The turntable clear interlock switch 165 and the legs up interlock switch 166 are used to sense the completed lower and raise automatic cycles respectively. The solenoids 154 and 155 are used to activate the change in gears within the trailer landing gear gear head 103. This is undertaken when the solenoids 154 and 155 act on the pneumatic valves 240 and 241 respectively. In this embodiment two miniature limit switches 167 and 168 are included which are mounted directly to the circuit board 216. These miniature limit switches 167 and 168 are activated by a gear position activating arm 250. When the miniature limit switches 167 and 168 are not operated then the microprocessor logic understands that the landing gear gear head 103 is in the low speed position. When the miniature limit switches 167 and 168 are both operated then the microprocessor logic understands that the landing gear gear head 103 is in the high speed position. When the miniature limit switch 168 only is operated then the microprocessor logic understands that the landing gear gear head 103 is not in either of the low or high speed positions and if a gear change is not in process then manual intervention may need to be undertaken.

This embodiment also sees the main and location operator panels 217 and 169 being of a pressure return membrane button type.

In the embodiment as illustrated in Figures 8 to 15 a typical scenario for an automatic legs down cycle is initiated, when the system is not already operating, by the operator momentarily pressing the lower button on either the main operating panel 217 or the alternate operating panel 169 for less than three seconds. This signal is received by the microprocessor which after ensuring the gear head 103 is in the high speed mode via miniature limit switches 167 and 168 then starts the electric motor. The lower legs 4 and 5 are then lowered by the electric motor r PCT/AUOO/00 1 53 WO 00/51859 29 201 as elsewhere described- When the landing gear lower 201 as elsewhere describedground the electric legs 4 and 5 become engaged with the ground thes el etric motor 201 electrical current eventually reaches its preset upper current limit and the electric motor 201 is stopped.

It should be noted at this point that in some circumstances the trailer and load may be so insignificant that the electric motor 201 electrical current preset upper limit is not reached and the landing gear lower legs 4 and 5 can n o t r e a h to be lowered in the high speed mode. The electric solenoid 154 is energised to activate the pneumatic valve 240. This valve passes pressurised air to pneumatic valve 240. e from high speed the sub-chamber 235 to effect a gear change from high speed to low speed. The electric motor is pulsed in the raise direction to ensure meshing of the non synchronous gears in the gear head 103. When the low speed gears are engaged which is acknowledged via the miniature limit switches 167 and 168 the electric motor 201 is again energised to continue the lower legs 4 and 5 on their downward path thus raising the trailer. The automatic lower cycle is concluded on reaching one of three conditions: The first condition being the electric motor 201 current has again reached the preset upper limit.

The second condition being that the turntable clear interlock switch 165 has been activated.

The third condition is that stop or raise buttons on either the main operating panel 217 or the alternate operating panel 169 has been operated.

The automatic raise cycle is activated, when the system is not already operating, and the raise button of either the main operating panel 217 or the alternate operating panel 169 is momentarily activated for less than three seconds.

This signal is received by the microprocessor which after ensuring the gear head 103 is in the low speed mode via miniature limit switches 167 and 168 then starts the electric motor. The lower legs 4 and 5 are then raised by the electric motor 201 as elsewhere described. When and Cf.. g.

pCTIAUOO/00153 WO 00/51859 30 the turntable clear interlock switch 165 is deactivated and the landing gear lower legs 4 and 5 become clear of the ground the electric motor 201 electrical current eventually drops to its preset lower current limit then the electric drops to its rese e eleri olenoi 5 is motor 201 is stopped. The electric olenoid 55 is energised to activate the pneumatic valve 241. This valve energised to activate tmubchambeer 236 to effect a passes pressurised air to the ubchaer 236 to eect a gear change from low speed to high speed. The electric motor is pulsed in the raise direction to ensure meshing of the non synchronous gears in the gear head 103. When the high speed gears are engaged which is acknowledged via the miniature limit switches 167 and 168 the electric motor 201 is again energised to continue the lower legs 4 and 5 on their upward path thus lowering the trailer. The autotic raise cycle is concluded on reaching one of three conditions: The first condition being the electric motor 201 current has reached the preset upper limit.

The second condition being that the legs up interlock switch 166 has been activated.

The third condition is that stop or lower buttons on either the main operating panel 217 or the alte operating panel 169 has been operated.

In this second embodiment there will be times when the landing gear lower leg 4 and 5 extension needs to be adjusted. This is achieved by holding the raise or lower buttons of either the main operator panel 217 or the alternate operator panel 169 for a period greater that three seconds. The logic of the microrocessor will recognise this holding of the raise or lowerbuttons and not continue in an automatic mode but only raise or lower the legs respectively for the period that the raise or lower buttons are activated. Gear change can still be undertaken manually and is effected by the operator manually acting on the system 200 to effect he axally displacement about the drive shaft 13 of the system 200 f WO 00/51859 WO 00/ 1859PCT/AUOO/00153 31 relative to the trailer landing gear.

t

Claims (14)

1. A demountable drive mechanism for the landing gear of a semi-trailer, the landing gear including legs that are extendable and retractable by rotation of a drive shaft through a gear mechanism, the drive shaft being axially displaceable to change the ratio of the gear mechanism, the drive mechanism comprising an electric motor having an output shaft adapted to be coupled to the drive shaft of the landing gear assembly, the electric motor being coupled to the landing gear through a torque arm so that the electric motor can impart torque to the drive shaft, means to axially displace the drive shaft t hange the gear ratio, and means to control operation of the electric motor and axial displacement of the drive shaft.

2. A demountable drive mechanism according to claim 1 wherein the means to control operation of the electric motor includes a current sensor to sense changes in current, to start or stop or effect a change of gear ratio, the change in current being dependent on load changes on the drive mechanism.

3. The demountable drive mechanism according to claim 1 wherein the torque arm comprises a flange secured to the landing gear that engages a sleeve that can move axially relative to the flange but transfers torque from the flange to the sleeve.

4. The demountable drive mechanism according to any one of the preceding claims wherein the electric motor is powered by at least one battery carried by the trailer. The demountable drive mechanism according to any one of claims 1 to 3 wherein the electric motor is driven by the power source of the prime mover that is adapted to be attached to the semi trailer.

PCT/AU00/0 0 15 3 WO 00/51859 33

6. The demountable drive mechanism according to any one of claims 1 to 3 wherein the electric motor is driven by a source of mains electricity from a stepdown transformer.

7. The demountable drive mechanism according to any one of the preceding claims wherein the means to control operation of the electric motor includes a sensor to operation of the electic to braking system of the determine the air pressure in the braking system f the trailer to ensure that the trailer brakes are on during operation of the drive mechanism.

The demountable drive mechanism according to any one of the preceding claims wherein the torque arm allows a degree of relative radial movement between the electric motor and the drive shaft to ensure meshing of the gears as the drive shaft is axially displaced to effect a change of ratio.

9. The demountable drive mechanism according to an one of the preceding claims wherein the meanstio coaxiay displace the drive shaft to change the gear rtio co at least one solenoid mounted between the electric motor 25 and the landing gear actuation of the solenoid being and t hd tand agearo eorand drive shaft adapted to axially move the electric motor and drive shaft of the landing gear to change the gear ratio.

The demountable drive mechanism according to any one of Claims 1 to 8 wherein the means to axially displace the drive shaft comprises a pneumatic actuator adapted to displace the electric motor and drive means relative to the landing gear to axially displace the input shaft.

11. The demountable drive mechanism according to any one of Claims 1 to 8 wherein a pneumatic piston and cylinder assembly is coupled to an air reservoir via valves PCT/AU00/00 15 3 WO 00/51859 34 whereby operation of the valve pressurises either side of the piston to cause relative displacement of the piston relative to the cylinder, the input shaft being coupled to either the piston or cylinder to be displaced relative to the lending gear to effect speed change.

12. The demountable drive mechanism according to Claim 11 wherein the valves are biased to a neutral position in which both sides of the piston are vented to atmosphere to facilitate manual override.

13. The demountable drive mechanism according to Claim 12 wherein each side of the piston is vented through a narrow bore to delay escape of pressurised air to act as a damper against the movement between the piston and cylinder.

14. The demountable drive mechanism according to any one of the preceding claims having limit switches providing an indication of any one or more of the following parameters: a) upper position of landing gear in up' position, b) lower position of landing gear in 'down' position, c) trailer clear of an associated prime mover, d) limit positions of axial displacement of drive shaft to effect change gear ratio.