Abstract:
An implement interface for mounting on a chassis of a vehicle includes a telescopic boom pivotally coupled to the vehicle chassis so that the boom is pivotal about an essentially horizontal axis. The boom includes a housing which is pivotally coupled to the vehicle chassis and an arm which is slidably received by the housing. A carrier is mounted on a free end of the arm. A three-point hitch is mounted on the boom and has lower links coupled to the carrier, has an extendable upper linkage coupled to the boom, a lifting arm coupled to the carrier, a lifting brace connecting the lifting arm to one of the lower linkages, and a lift cylinder for vertically pivoting the lifting arm. A locking mechanism fixes the boom relative to the chassis. A hydraulic cylinder unit is coupled to the sliding arm and operable to move the sliding arm in a longitudinal direction. A pressure-operated piston/cylinder unit is coupled between the housing and the chassis and is operable to vertically pivot the boom.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to an implement interface for attaching an implement to the rear or front of a vehicle, such as an industrial or agricultural tractor. 
     Industrial or agricultural vehicles, such as tractors, in addition to performing transport tasks, are primarily used for carrying out tasks in the field. For this purpose, a suitable implement is attached to the working vehicle. 
     Since the tractor must be coupled to various implements in order to carry out different tasks, the implement interface between the motor vehicle and the implement is of particular importance. The term implement interface refers to all devices which are required for coupling the implements to the vehicle and, if so required, for supplying them with power. 
     A so-called three-point hitch, e.g., as defined by ISO 730 or DIN 9674, is a conventional implement interface provided on most modern tractors and similar agricultural vehicles includes. Such a hitch usually includes two lifting arms that are connected to one another by means of a lifting shaft, and a corresponding hydraulic lifting cylinder engages each of the lifting arms. Each lifting arm is connected to a corresponding lower linkage by means of a lifting rod or a lifting spindle, and the lower linkage carries a lower coupler. In addition, the three-point hitch includes an upper linkage with a third, central upper coupler. 
     Such a three-point hitch makes it possible to easily and rapidly attach implements to the tractor. First, the tractor is moved near the parked implement. The implement is then coupled to corresponding receptacles of the implement interface so that the vehicle and the implement form a functional unit. If so required, a power take-off shaft of the vehicle is connected to an input shaft of the implement. In addition, electric and hydraulic connections for transmitting power and signals can be provided between the working vehicle and the implement. The implement can be raised and adjusted with respect to its height within a limited range by actuating the lifting cylinders in order to move the implement between its transport position and the desired working position. In this case, the implement frequently does not require a separate chassis. Despite the fact that the three-point hitch can be used for many tasks, its functions are still limited. 
     SUMMARY OF THE INVENTION 
     objective of the present invention is to provide an implement interface which can perform functions not performed by a conventional three-point hitch. 
     These and other objects are achieved by the present invention wherein an implement interface includes a telescopic boom which is mounted on a vehicle chassis, frame or body and which is pivoted about a substantially horizontal axis. The boom includes an outer housing and an arm which slides telescopically in the housing. Lower linkages of a conventional three-point hitch are coupled to a free end of the boom. An extendable upper linkage is directly or indirectly coupled to the boom. This results in a pivotable implement interface which can be adjusted with respect to its height and which can perform all the tasks normally performed by a conventional three-point hitch. The telescopic boom makes it possible to lift an implement (or the like) very high compared to the lifting high of a normal 3-point hitch. This makes it possible to lift the implement and to load it on a trailer. Implements can be moved with expanded degrees of freedom and an expanded lifting range. With this interface, the vehicle may be used as a conventional towing vehicle with a customary implement interface or as a functional loader. If the implement is a plow, the plow can be raised after the normal working operation (plowing) to such a degree that the implement can be deposited on a trailer or an elevated storage platform without additional means. 
     Because of the simple and rapid loading of the implement, the vehicle can be moved rapidly between different working locations. For example, the implement may be loaded onto a trailer after the work at one location is completed, and then the trailer is attached to the vehicle and driven to a new location at a high speed. An implement may be raised to an elevation such that the implement can be placed on shelves or trailers without first separating the implements from the three-point hitch. 
     Hitch lower linkages, and if required, other attachments and towing implements, may be coupled or mounted on a carrier which is attached a free end of the boom. Different carriers can be mounted on the boom in order to adapt to different requirements, without modification or changing of the boom. 
     Preferably, the interface includes a locking device which is operable to selectively fix the free end of the boom and/or the carrier relative to the vehicle chassis, such as when the boom is in a lowered work position. If this locking device is engaged, the hitch forces are transmitted directly to the rear axle or to the vehicle chassis, without being transmitted to the boom. Thus, the boom can be designed for relatively small loads. 
     The interface may include a lifting arm is coupled to the free end of the boom or to the carrier, and the lifting arm can be vertically pivoted by a lifting cylinder. This lifting arm is connected to one of the lower linkages by lifting brace, rod or cylinder, and the lower linkages retain their conventional functions. 
     Additional attachments may be coupled to the free end of the boom or on the carrier so that towed implements or trailers can be attached to the vehicle. For example, a trailer drawbar may be grasped while on the ground and hydraulically moved into the operating position. Electric and/or hydraulic connections which are used to transmit power or signals may also be provided on the boom or the carrier. 
     In a preferred embodiment, the boom may guide a arm which is coupled to the upper linkage, and which can be displaced in the longitudinal direction of the boom. An upper linkage coupled to the free end of the arm may be extended and retracted by means of the arm, and the arm can be oriented essentially parallel to the boom. The telescopic guidance of the arm in the boom results in a stable double-telescopic rear interface. 
     Preferably, double-acting hydraulic piston/cylinder units are used to pivot the boom and extend the arm, and are coupled between the vehicle chassis and the boom, and between the boom and the arm, and are supplied with hydraulic fluid from the vehicle hydraulic system. Preferably, two pivoting cylinders are arranged parallel to one another, and have one end coupled to the vehicle chassis and an upper end coupled to the boom housing so that the implement can be moved vertically. 
     An upper linkage cylinder may be integrated into the upper linkage and/or into the arm in order to extend and retract the coupler of the upper linkage relative to the boom. The length of the upper linkage may be adjusted with such an upper linkage. In this case, the implement may be maintained in a horizontal position within a lower lifting range by correspondingly controlling the upper linkage cylinder, and within an upper lifting range by correspondingly controlling the arm cylinder. 
     In order to raise the implement interface to a substantial height, the boom of one preferred embodiment includes a housing which is pivotally coupled to the vehicle chassis and an extendable insert that is guided by the housing and is used to extend the length of the boom. A carrier is preferably mounted within the free end of the insert and carries a three-point hitch and, if required, other attachments and towing implements. 
     Preferably, the insert is telescopically guided within the housing, and both have rectangular profiles for structural rigidity. In certain applications, the boom may have three sections that are concentrically inserted into one another. With such a telescopic boom, the coupling of implements and digging with an earth scoop can be achieved by horizontal extension and retraction of the telescopic arm, without having to move the tractor. A hydraulic piston/cylinder unit may be coupled between the housing of the boom and an extendable insert or between the respective sections of the boom in order to extend and retract the sections. 
     An adapter can be mounted on the three-point hitch and used to receive special implements that require special implement interfaces and which cannot be attached to a conventional three-point hitch. With an appropriate adapter, this interface may be used as a conventional front-end loader, and front-end loader tools, such as an earth scoop, the fork of a forklift, etc., can be attached to the three-point hitch. 
     Preferably, the pivoting system is designed so that the coupling plane is maintained vertical or in another desired alignment independently of the incline of the boom, so that the implement maintains a certain desired alignment relative to the ground during a series of tasks, even if the boom has been pivoted vertically. A level control unit is provided for controlling the pivoting cylinder, arm cylinder, upper linkage cylinder, lifting cylinder and/or extension cylinder so that the implement is maintained in the desired alignment relative to the ground independently of the incline of the boom. The implement alignment and position can be monitored by a suitable sensor in order to determine an actual value signal for the level control. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view of the rear region of a vehicle with an implement interface according to the present invention shown in a lowered, work position; 
     FIG. 2 is a side view of the implement interface of FIG. 1, with the implement interface in a raised position; 
     FIG. 3 is a side view of the rear region of a vehicle with an implement interface according to an alternate embodiment of the present invention shown in a lowered, work position; 
     FIG. 4 is a side view of the implement interface of FIG. 3, with the implement interface in a raised position; 
     FIG. 5 is a side view of the rear region of a vehicle with an implement interface according to the present invention with a locking device for a three-point hitch; 
     FIG. 6 is a side view of an implement interface according to the invention with a towing implement mounted on the vehicle chassis; 
     FIG. 7 is a rear view of the implement interface of FIG. 6; 
     FIG. 8 is a side view of an implement interface according to the invention with a towing implement mounted on a three-point hitch, and 
     FIG. 9 is a rear view of the implement interface of FIG.  8 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The Figures show the rear portion of a vehicle with a rear implement interface which is adjustable in height. The vehicle may be a conventional towing vehicle with a center or front seat and with four wheels of similar size, such as conventional Fasttrac or MBtrac. As shown in FIGS. 1 and 2, a boom  16  is mounted on the vehicle between the driver&#39;s cab  12  and the rear axle, and in the center relative to the width of the vehicle, and is pivotally coupled to a coupling point or pivot support  26  which is fixed rigidly to the chassis  14 . This boom  16  is pivoted in the vertical direction by two pivoting cylinders  28  which are arranged on both sides of the boom  16 . Each cylinder  28  has one end coupled to the chassis  14  and a second end coupled to an outer surface of the boom  16 . 
     A carrier  22  is rigidly mounted on the free end of the boom  16 . Two lateral lower rearwardly extending linkages  46  are pivotally coupled to the carrier  22  at coupling points  32 . The lower linkages  46  can be raised and lowered by corresponding lifting arms  48  and lifting braces  50  which are coupled to the carrier  22 . At their free ends, the respective lower linkages contain couplers  49 . 
     The lifting arms  48  are actuated by lifting cylinders  52 , wherein one end  53  of each cylinder is pivotally coupled to the carrier  22 , and the other end of each lifting cylinder engages a coupling point  54  of the corresponding lifting arm  48  in an articulated fashion. The transverse movement of the lower linkages  46  can be limited by conventional stabilizer linkage  47 . 
     The boom  16  includes a housing  15  and an arm  20 . The arm  20  is slidably received by the housing  15 , and is axially extended and retracted by an arm cylinder  30 . One end  31  of cylinder  30  is coupled to the housing  15 , and the other end  33  is coupled to the arm  20 . To save space, the cylinder  30  is mounted inside the housing  15  and the arm  20 . As best seen in FIG. 2, the arm  20  has a free end which projects out of the housing  15  and carries an upwardly projecting bearing block  35 , to which is coupled an upper linkage  44 . The upper linkage  44  integrally includes a hydraulically actuated upper linkage cylinder  45  which is operable to adjust the length of the upper linkage  44 . A coupler  51  is mounted on the free end of the upper linkage  44 . The arm  20  can be extended and retracted relative to the boom housing  15  together with the upper linkage  44  by actuating the arm cylinder  30 . Consequently, the position of the coupler  51  of the upper linkage  44  can be changed by actuating the arm cylinder  30  as well as by actuating the upper linkage cylinder  45 . 
     The couplers  49  of the lower linkages  46  and the coupler  51  of the upper linkage  44  form an implement interface configured as a three-point hitch  24  which is able to receive implements (not shown) or adapters (not shown) for mounting special implements (not shown). The couplers  49  of the lower linkages  46  may also be connected to the coupler  51  of the upper linkage  44  by a mast that lies in the coupling plane  56 . Additional implements (not shown) may also be directly mounted to the vehicle chassis  14 . 
     A power take-off shaft  60  projects out of a power take-off shaft gear housing  62 . The power take-off shaft gear housing  62  is connected to a gear housing (not shown) of the vehicle. The power take-off shaft  60  is covered by a conventional power take-off shaft protection shield  64 . 
     The described implement interface is able to operate in two modes—a working or towing mode and a lifting mode. FIG. 1 shows the boom  16  in its lowered and locked position for the working mode. This position represents the transport position as well as the work position for all tasks performed with the three-point hitch  24 . The carrier  22  is rigidly connected and locked to the vehicle chassis  14  by means of a locking mechanism that is described in detail below. All loads are directly introduced into the vehicle chassis  14  from the carrier  22  via the locking mechanism such that the boom  16  is unloaded. In this position, the power take-off shaft  60  of the vehicle can be connected to an input shaft of the implement, and not-shown electric and/or hydraulic connections for transmitting power and signals between the vehicle and the implement can be produced. The working mode is activated after the implement is coupled to the vehicle by actuating the lock. The working mode corresponds to that of a conventional three-point hitch. 
     In the lifting mode, the boom  16  is unlocked and can be pivoted in the vertical direction by the pivoting cylinders  28 . FIG. 2 shows the boom  16  in a raised position. In the lifting mode, lifting and loading tasks can be carried out, and implements which were stored at a high elevation can be connected and disconnected. For example, implements can be loaded onto and unloaded from trailers or stored on shelves in this mode. 
     The alternative embodiment shown in FIGS. 3 and 4 essentially differs from that of FIGS. 1 and 2 only with respect to the design of the boom  16 , as described in greater detail below. Identical components or components that correspond to one another are identified by identical reference symbols in FIGS. 1-4. 
     Referring now to FIGS. 3 and 4, the boom  16  includes an outer housing  15  which is pivotally coupled to the chassis at pivot  26 , and an extendable insert or inner housing  17  that is guided inside the outer housing  15  in a telescopic fashion. The outer housing  15  can be pivoted in the vertical direction by pivoting cylinders  28 , similar to the housing  15  of FIGS. 1 and 2. The insert or inner housing  17  can be extended and retracted with respect to the outer housing  15  by an extension cylinder  19  which is mounted above the outer housing  15 . The cylinder  19  has one end coupled to the outer housing  15  and another end coupled to the inner housing  17 . A carrier  22  (similar to that of FIGS. 1 and 2) is mounted on the free end of the inner housing  17 , which protrudes out of the outer housing  15 . 
     An arm  20 , similar to the arm of FIGS. 1 and 2, is movably received inside the insert  17 . The arm  20  is extended and retracted in the axial direction inside the insert  17  by cylinder  30 . One end  27  of the cylinder  30  is coupled to the insert  17  and its other end ( 29 ) is coupled to the arm  20 . To save space, the cylinder  30  is also preferably arranged inside the insert  17  and the arm  20 . 
     In the embodiment of FIGS. 1 and 2, only a portion of the implement interface  24  is telescopically extendable. For example, the couplers  32  of the lower linkages on the side of the tractor cannot be extended, but only pivoted vertically by the lifting cylinders  52 . The coupling plane  56  is aligned by retracting and extending the upper linkage  44  by means of the arm cylinder  30  and/or the upper linkage cylinder  45 . In the embodiment of FIGS. 3 and 4, the entire implement interface  24  is telescopically extendable. For example, the lower linkages  46  and the upper linkage  44  can be collectively extended when cylinder  19  moves the insert  17 . This permits horizontal movement of the implement interface  24  and increases its lifting range. In the embodiment of FIGS. 3 and 4, the coupling plane  56  can also be aligned by retracting and extending the upper linkage  44  by means of the arm cylinder  30  and/or the upper linkage cylinder  45 . 
     In addition to the towing mode and the lifting mode described above with reference to FIGS. 1 and 2, the embodiment of FIGS. 3 and 4 allows another operating mode that is not illustrated in detail. In this operating mode, the boom  16  may be unlocked analogously to the lifting mode. The insert  17  can be extended and retracted while the boom  16  (housing  15 ) is lowered. Consequently, this lowered position makes it possible to move the implement interface  24  into the vicinity of implements and to receive these implements without having to move the vehicle. For example, the coupling of an implement or trailer on the ground can be grasped in this position. Consequently, the interface can function as tractor coupling and/or as a pick-up hitch. Depending on the design of the boom, the interface can function as a rigid tow-bar (by means of a partial extension), and the interface can function as a height-adjustable tractor coupling (by means of raising/lowering). If the insert  17  is extended and the pivotable arm  15  is in its lower position, the couplers  49  of the lower linkages  46  can, assume positions that are lower than the ground surface. Consequently, the embodiment shown in FIGS. 3 and 4 is also suitable for digging with earth scoops and the like, without moving the vehicle. 
     As mentioned previously, and as best seen in FIG. 5, the carrier  22  can be locked relative to the vehicle chassis  14 . This locking function may, for example, be realized with two catch hooks  40  that are open toward the top and fixed on each of the two axle hubs  42  such that they are laterally offset from the longitudinal axis of the vehicle. However, if the axle is mounted on springs, it is proposed to mount the catch hooks  40  on the vehicle chassis  14 . This locking mechanism may be also be used with the embodiments of FIGS. 1-4. 
     The hooks  40  include upwardly opening slots which receive two projections  38  which project laterally from the sides of the carrier  22 . The projections can also be locked into the slots of the catch hooks  40  by means of a locking mechanism (not shown). For example, locking mechanisms of the type used for rapid-action couplers of lower linkages may be used. Alternatively, bores and bolts (not shown) may be used to locking together the carrier  22  and the vehicle chassis  14 . When the carrier  22  is locked to the vehicle chassis  14 , the carrier  22  and the implement interface are fixed relative to the vehicle chassis  14  and unable to move relative to the vehicle chassis during transport or while performing tasks with a implement. This is useful for tasks involving a power take-off shaft. 
     Once the carrier and the vehicle are interlocked, the forces transmitted by the carrier  22  are transmitted directly to the rear axle or to the vehicle chassis  14 , without being applied to the boom  16  (or the housing  15  and the insert  17 ). Consequently, tensile stresses are directly transmitted to the vehicle chassis; in particular, during towing and transport tasks, so that the boom  16  (or the housing  15  and the insert  17 ) are unloaded in these operating modes. Consequently, the boom can be designed for relatively small loads. 
     In FIGS. 6 and 7 a coupler  70  is mounted on the power take-off shaft gear housing  62 . This coupler  70  is height-adjustable with two lateral guide rails  72  that guide a coupler member  74  which can be adjusted vertically and locked at different heights. Since the coupler  70  is mounted on the stationary power take-off shaft gear housing  62 , the vertically adjustable rear interface ( 22 ,  48 , etc.) is not stressed when implements are attached to coupler  70 . 
     FIGS. 8 and 9 show an alternative embodiment of a hitch  76  wherein a coupler  78  is mounted on the carrier  22 . This embodiment is simpler than the embodiment of FIGS. 6 and 7 because the guide rails  72  can be eliminated. In this case, the height of the coupler  78  is controlled by adjusting the height of the boom  16  with double acting cylinders  28 . Although not shown, the embodiment of FIGS. 8 and 9 also preferably includes a double-acting extension cylinder and a double-acting arm cylinder  30  which are supplied with hydraulic fluid from the vehicle hydraulic system (not shown). These hydraulic cylinders are preferably actuated by control units (not shown) located in the vehicle cabin  12  which operate hydraulic valves (not shown) to control the flow of hydraulic oil thereto. The lifting cylinders  52  may be conventionally actuated and controlled. A known level control (not shown in detail) may be used to control the cylinders  28 , the extension cylinder, the arm cylinder and, if required, an upper linkage cylinder, so as to maintain a coupling plane in a desired operating position while the implement interface is raised or lowered. 
     While the present invention has been described in conjunction with a specific embodiment, it is understood that many alternatives, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, this invention is intended to embrace all such alternatives, modifications and variations which fall within the spirit and scope of the appended claims.