Abstract:
A combination of a tractor unit ( 10 ) and a wheeled trailer combination, preferably a mobile screening plant ( 100 ), in which the tractor unit ( 10 ) has endless tracks ( 11 ) to render the combination highly maneuverable, and carries an upwardly and downwardly adjustable “fifth wheel coupling” ( 13 ) which pivotally connects the forward end ( 115 ) of the screening plant ( 100 ), the latter having a wheelset ( 118 ) at its rear end, and in which the screening plant ( 100 ) has an input hopper ( 114 ), an elevator ( 112 ) for conveying material to be screened from the hopper to a screen box ( 117 ), and one or more discharge conveyors ( 121, 123 ) for discharging screened material to form one or more stockpiles of screened material.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a tractor unit and wheeled trailer combination. 
     A tractor unit can be used to propel a wheeled vehicle, such as an articulated trailer, and usually is provided with a so-called “fifth wheel” coupling, to which the forward end of the trailed vehicle is detachably coupled. In order to un-couple the vehicle, it is necessary to extend temporary support legs which support the forward end of the vehicle, and then to allow the fifth wheel coupling and the trailer coupling to be un-coupled, whereby the tractor unit can move away while leaving the trailer stationary and in a safe and stable position e.g. at an unloading bay, or parked in a trailer park. 
     Known fifth wheel couplings can compensate for any minor vertical misalignment between a trailer coupling and the tractor coupling, in that if the trailer coupling is too high, the fifth wheel coupling can be reversed into a receiving position below the trailer coupling, and then the forward end of the trailer can be lowered until the trailer coupling can enter a mounting socket in the fifth wheel coupling, to complete the coupling connection. 
     In the event that the trailer coupling is too low (by a small amount), inclined guide surfaces on the fifth wheel coupling can engage the trailer coupling and progressively raise the forward end of the trailer until the trailer coupling is able to drop into the mounting socket, again to complete the coupling connection. 
     However, in the event that there is substantial vertical misalignment between the trailer coupling and the fifth wheel coupling, this will usually involve some substantial manual adjustment of the height of the forward end of the trailer, by suitable adjustment of the support legs, and with care being taken that this results in the height of the trailer coupling being suitable then to allow easy engagement between the fifth wheel coupling and the trailer coupling. 
     BRIEF SUMMARY OF THE INVENTION 
     In one aspect the present invention is concerned with an improved means of mounting a fifth wheel type coupling on a tractor unit, to permit its height to be adjusted to allow easy coupling together of the tractor unit and a wheeled vehicle to be coupled therewith, and without need to carry out any adjustment in the height of the coupling end of the wheeled vehicle. 
     According to one aspect of the invention there is provided a tractor unit for propelling a wheeled vehicle, when the latter is coupled therewith, said tractor unit having a vehicle coupling unit, and said wheeled vehicle having a coupling for co-operation therewith, and in which the coupling unit on the tractor unit is adjustably mounted on a supporting frame of the tractor unit, so as to be capable of being adjustable in height to align itself with the height of the coupling of the wheeled vehicle when the latter is free-standing in a separated position. 
     By providing an adjustable-in height coupling unit on the tractor unit, the tractor unit can be manoeuvred easily, with suitable adjustment of the height of the coupling unit, so as to bring the coupling unit of the tractor and the coupling of the vehicle into close co-operation with each other, and without need for any vertical adjustment of any usual temporary support legs at the coupling end of the wheeled vehicle. 
     The vehicle coupling unit on the tractor unit may be a female type of coupling plate, and the co-operative coupling on the vehicle may comprise a male type of coupling. 
     The female type of clamping plate on the tractor unit may take the form of a “fifth wheel” type of coupling, known per se, and any suitable lifting mechanism may interconnect the coupling and the supporting frame of the tractor unit, to provide necessary upward and downward adjustment of the height of the coupling. This may comprise a hydraulically operated actuator mechanism. 
     Evidently, in addition to facilitating coupling together of the tractor unit and a stationary wheeled vehicle e.g. an articulated trailer, when in the parked position, the facility to adjust the height of the coupling on the tractor unit will also facilitate un-coupling. Thus, the wheeled vehicle can be manoeuvred into a required parked position e.g. in a loading bay, and then suitable temporary support legs can be extended to support the coupling end of the trailer, and then the adjustable coupling on the tractor unit can be lowered thereby allowing the tractor unit to separate from the vehicle. 
     It should be understood that a tractor unit according to the invention may be coupled with any type of wheeled vehicle, to propel the latter, and including articulated trailers, mobile screening plants, and other mobile equipment of the type used in quarry sites e.g. a crushing plant, a crushing and screening plant, and a discharge conveyor or elevator. 
     Preferably, the tractor unit has a pair of endless tracks, to provide for easy manoeuvrability, and also to improve traction when hauling a wheeled vehicle (when coupled with it) over adverse ground conditions. 
     The tractor unit may have a driver&#39;s cab, mounted on the support frame at any convenient point, preferably the forward end. However, the invention also includes possibility of the tractor unit being remotely controlled, via remote control from remote hand held control units and preferably by infra-red control. 
     In a separate aspect of the invention, a tractor unit and mobile screening plant combination is provided, and which optionally is provided with a coupling between the tractor unit and the mobile screening plant as defined in said one aspect of the invention above. 
     According to a further aspect of the invention, there is therefore provided a tractor unit and a mobile screening plant combination, in which the tractor unit is intended to propel the combination, and the mobile screening plant comprises a towable frame or chassis having one or more wheel sets at a rear end, and a coupling at its forward end by which it can be coupled, preferably detachably coupled, with a suitable coupling provided on the tractor unit. The screening plant is intended to screen particulate material, and having a screen box or screen grid, means for supplying bulk material thereto, and one or more discharge conveyors for discharging screened material, such discharge conveyor(s) being arranged to discharge in one or more of the following directions: 
     a) rearwardly of the plant 
     b) laterally to one side of the plant; 
     c) laterally to an opposite side of the plant; and 
     d) in all of these directions if required. 
     In a quarry or other environment, it is desirable to provide mobile screening plants, which can receive supplies of bulk material to be screened, eg from a tipper truck, a bucket loader, or a supply conveyor, and which can then screen the material into at least one screened fraction, although preferably more than one, and then can discharge the screened material to suitable stockpiles. In order to use up the space available for stock piling most advantageously, it will be highly desirable to provide a manoeuvrable tractor unit/screening plant combination, and the invention, in a further aspect, seeks to achieve this objective. In particular, the length of the tractor unit, relative to the overall length of the screening plant, is small, and with a pivotal coupling at the forward end of the screening plant, and one or more wheel set at the rear end, and also with preferred arrangement of endless tracks to propel the tractor unit, a highly manoeuvrable combination is obtained. The screening plant therefore can be caused to rotate about a generally vertical axis, passing generally in the region of the axle of the wheel set, and with one or more laterally projecting discharge conveyor deployed to discharge screened material, a progressively increasing circular array of stockpiles can be formed. 
     Alternatively, with at least one side discharge conveyor in the deployed position, and preferably with one projecting from each side, and optionally with a so called “tail conveyor” also deployed, the tractor unit may, for some requirements, be caused to move forwardly in intermittent steps, so that the discharge end of each conveyor discharges successive stock piles, so that two or three lines of progressively increasing length of stockpiles can be formed. This allows the available space to be used most efficiently, and the manoeuvrability of the combination contributes significantly to this advantage. 
     The tractor unit may have a driver&#39;s cab, or may be arranged to be remotely operable, eg by radio or preferably infra red remote control. 
     The engine to operate the tractor unit may be provided on the chassis of the tractor unit, and may also serve as a source of motive power to operate the screening components of the screening plant. Alternatively, a power plant may be provided on the chassis or frame of the screening plant, to operate the screening components, and means may be provided also to transmit power from this power plant, eg by operating a hydraulic pump and motor combination, to provide necessary power to operate the tractor unit, which as mentioned above, preferably has a pair of endless tracks. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A preferred embodiment of a tractor unit according to one aspect of the invention, and a tractor unit/screening plant combination according to a further aspect, will now be described in detail, by way of example, with reference to the accompanying drawings, in which: 
     FIG. 1 is a side view of a tractor unit according to the invention; 
     FIG. 2 is a side view of a towable screening plant which may be detachably coupled with the tractor unit, to form a tractor unit/screening plant combination according to the invention; 
     FIG. 3 is a side view showing a further embodiment of tractor unit/screening plant combination, showing possible mode of use; 
     FIG. 4 is a plan view of the combination shown in FIG. 3, showing a further mode of use; and 
     FIG. 5 is a plan view showing a still further mode of use of the combination shown in FIG.  3 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring first to FIG. 1 of the drawings, there is shown a preferred embodiment of tractor unit for propelling a wheeled vehicle, when the latter is coupled therewith. The wheeled vehicle may comprise an articulated trailer, or other types of vehicle, such as mobile screening plants, or other mobile equipment of the type used in quarry installations (e.g. combined crushing and screening plant, or a discharge conveyor or elevator) or at locations where crushing, shredding, and screening operations take place e.g. in connection with site clearance work, landfill sites, and soil excavation. 
     The tractor unit is designated generally by reference  10  and is a self-propelled unit having its own engine and drive train. The tractor unit  10  has a pair of endless tracks  11  which give the tractor unit  10  particular manoeuvrability, and also a powerful hauling action, which is particularly useful when pulling a trailed vehicle through/over adverse ground conditions. The tractor unit  10  has a forwardly mounted housing  12 , and which may house a suitable prime mover, and drive train to the endless tracks  11 . The housing  12  may incorporate a driver&#39;s cab, if driver operation is required. Alternatively, or additionally, the tractor unit  10  may be arranged to be capable of remote control via a manually operated remote control unit, or via an umbilical. Preferred means of exercising remote control is via radio control. 
     The wheeled vehicle to be coupled with the tractor unit  10  is not shown in FIG. 1, and may comprise e.g. an articulated trailer, having a suitable male type of coupling at its forward coupling end. The tractor unit  10  has a vehicle coupling unit in the form of a female type of coupling plate  13 , having a suitable mounting socket into which the male type trailer coupling can be received, in order to couple together the tractor and trailer. Preferably, the coupling  13  is effectively a “fifth wheel” type of coupling. However, by virtue of the means whereby the coupling  13  can be vertically adjusted in height, easy coupling together can take place, and any necessary manoeuvring of the tractor unit can be made, to bring the mounting socket into horizontal alignment with the trailer coupling, and with suitable final small adjustment in height of the coupling  13  to bring the two couplings into secure connection together. 
     The coupling plate  13  is vertically adjustably mounted on a support frame  14  of the tractor unit  10 , and can be raised or lowered to any required height by operation of a suitable actuating mechanism, shown generally by reference  15 , and which may be hydraulically operated mechanism. FIG. 1 shows both raised and lowered positions of the coupling plate  13 . 
     The tractor unit  10  which is illustrated in the drawing is particularly manoeuvrable, and can be easily coupled with, and uncoupled from even very long wheeled vehicles, such as mobile screening plants of the type used in quarries, and by virtue of the manoeuvrability of the tractor unit  10  with its endless tracks  11 , manoeuvring into position for coupling purposes can be easily carried out, and when coupled with a trailer vehicle, even one of great length, it can easily manoeuvre the vehicle even in relatively confined spaces. 
     Referring now to FIG. 2 of the drawings, there is shown, by way of example, a typical type of towable mobile screening plant which may be coupled with the tractor unit described above with reference to FIG.  1 . The screening plant is designated generally by reference  100 , and is intended to screen bulk material into one or more screened fractions of particulate material, and comprises a base frame  111 , an elevating conveyor  112 , and a conveyor carrying frame  113  adjustably mounted on the base frame  111  and arranged so as to be capable of moving the conveyor  112  generally lengthwise in order to adjust the position of an upper end  116  of the conveyor so as to vary the region of deposition of screenable material onto a vibratory screen box  117 . 
     The material falling under gravity from the upper discharge end  116  is received by the screen box  117 , and which may have one or more screen decks, so as to screen the material into one or more different sizes of screened fractions. In the illustrated embodiment, a rear conveyor, namely a so called tail conveyor  123  is arranged to discharge screened material in a rearward direction. Although not shown, preferably the base frame  111  of the screening plant  100  mounts one, and preferably a pair of side discharge conveyors, one on each side of the frame, and which can be deployed from transport positions running alongside the length of each side of the frame, to laterally outwardly projecting positions so as to discharge screened material laterally of the plant. 
     Loading of the screening plant with bulk material is preferably achieved by supplying the bulk material to an input hopper/preliminary screen  114  provided at the forward end of the elevating conveyor  112 . 
     The base frame  111  is supported at or near its rear end by a rear wheel set, and in the illustrated arrangement a tandem wheelset designated by reference  118 . The forward end of the base frame  111  has suitable pivot coupling mounted thereon, preferably by way of a male pin projecting downwardly from a base  115  of the hopper  114 , and which can be coupled with the fifth wheel coupling  15  of the tractor unit  10 . 
     FIG. 3 shows to a reduced scale, a similar type of screening plant to that described and shown in FIG. 2, and which is designated generally by reference  120 . Tractor unit  10  is coupled with the screening plant  120 , and since the screening plant  120  is provided with a pair of lateral or side discharge conveyors  121  (see in particular FIG.  4 ), as well as a rear or tail discharge conveyor  122 , this provides a range of options with regard to the discharge mode which may be required, depending on the space available. In the mode of use shown in FIG. 4, three progressively increasing lines of stockpiles can be formed, by discharge from the ends of the conveyors  121  and  122 , and with step wise forward movement of the tractor unit  10 , the lines of stockpiles can be progressively increased. 
     However, by virtue of the short overall length of the tractor unit  10 , relative to the length of the screening plant  120 , and by reason also of the pivotal coupling between the forward end of the frame of the screening plant to the coupling of the tractor unit plus the rear wheel set supporting the rear end of the screening plant, a very manoeuvrable combination is obtained. By suitable operation of the endless tracks driving the tractor unit, the trailed screening plant can be easily manoeuvred to take up any suitable discharge position (by rotation about a vertical axis passing generally through the wheel set). This is shown schematically in FIG. 5, which shows how, for example, a circular array of stock piles can be formed. 
     The tractor unit therefore is capable of carrying out screening and discharge of particulate material while on the move, when required, but of course also can be operated in a stationary mode when required.