Abstract:
An assembly with a lower steering arm has a strut  1  and an attaching end  16.  To achieve a cost-effective design while at the same time reducing the play between the attaching end  16  and the end of the strut  1  received therein, the attaching end  16  includes a base member  18  and a cover  19.  A blocking pawl  34  is supported in the base member  18.  The cover  19  is welded to the base member  18  and comprises a stop face  30  for the end face  10  of the strut  1.  Thus, any tolerances in the region of the base member  18  provided in the form of a forging do not affect the position of the stop face  30.  The latter can be aligned when connecting the base member  18  and the cover  19.  Because of its setting contour, the actuating lever  43  can be used for both the right hand and the left hand lower steering arm.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority upon German application 198 49 070.4 filed Oct. 24, 1998, which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The invention relates to a lower steering arm assembly for an implement attaching device. The assembly includes a strut pivotably attachable to a tractor or a self-driving working machine. An attaching end is removably fixed to the free end of the strut. The attaching end provides a connection with an implement. 
     EP0 608 750 A1 describes a lower steering arm assembly for a three-point attaching device of a tractor. A forged strut, at one end, has a ball eye to be connected to a pivot pin at the rear of the tractor. The strut has a rectangular cross-section and is stepped. Near its free end, the strut is forged to be U-shaped. A cover is welded to the arms of the U-shaped portion forming a closed chamber. The forged web of the strut has a formed-in pocket. A blocking pawl is pivotably arranged around a pin connection in the pocket. The blocking pawl is spring loaded into the blocking position where it is pivoted out of the chamber. Two further pins are provided at a distance from the pivot pins. One of the pins is guided outwardly through an opening in one of the arms of the U-shaped portion. A knob is on the end of the pin to enable manual manipulation of the pawl. Thus, it is possible to move the blocking pawl, loaded by the spring, into a position which is withdrawn into the pocket. A stop face is provided at the end of the chamber of the forged strut. An insertable end is inserted into the chamber. The end has a substantially rectangular cross-section. A recess extends through the entire side face of its shank. The end has a supporting face for the locking face of the blocking pawl. The supporting face extends substantially transversely to the longitudinal axis of the insertable end. The end face of the insertable end comes to rest against the stop face of the chamber. At its end projecting from the chamber, the insertable end has a ball eye. The ball eye provides a connection with a corresponding attaching pin of the implement. After the blocking pawl has been retracted, the insertable end may at least be partially extracted from the chamber to facilitate the coupling operation. The setting recesses in the shank enable angular adjustment relative to the strut remaining at the tractor in order to facilitate the coupling operation. By reversing the tractor, the insertable end can be driven into the chamber. As this occurs, the blocking pawl, after the end face of the shank of the insertable end has stopped against the stop face of the chamber, drops into the recess in the side face of the shank. 
     The stop face at the end of the U-shaped recess of the strut must be machined to be able to observe the tolerances required for accurate locking. The stop face is adapted to the distance between the end face of the shank of the insertable end and the blocking face of the recess, and also to the locking face of the blocking pawl. In practice, close tolerances cannot be observed because subsequent machining, when the cover has already been associated with the U-shaped region, is not possible. This design makes it necessary for the entire strut to be forged, which, in turn, means high costs. 
     Furthermore, since the blocking pawl is supported by a journal, a great deal of machining is required. Finally, the actuating knob has to be associated with different parts, depending on whether it is used for the left-hand or right-hand steering arm. In addition, due to the direction of the force acting on the actuating knob, remote actuation, by a cable operated from the tractor seat, is not possible. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a lower steering arm assembly with an actuator for the locking mechanism between the attaching end and the strut. The actuator is suitable for a right-hand and a left-hand lower steering arm without modification. 
     In accordance with the invention, a lower steering arm assembly includes a strut and an attaching end. The strut constitutes one component and the attaching end a further component. One of the components includes a blocking pawl. With the help of an actuator, the blocking pawl is pivotable between a locked position and an open position. In the locked position, the blocking pawl engages a recess of the other component. In the open position, the blocking pawl is disengaged from the recess. The blocking pawl is loaded by a spring to assume the locked position. The actuator includes an actuating lever. The lever is pivotable around a pivot axis and includes at least one actuating arm which extends radially from the pivot axis. The actuator includes a setting contour on which the actuating arm is at least partially supported. The contour includes an indentation with a base. Setting faces risingly extend in opposing directions of the actuating lever in the supporting region. A connecting element connects the actuating lever with the blocking pawl at a distance from the pivot axis of the blocking pawl. 
     The setting contour is of a symmetric design. Accordingly, when the actuating arm moves in one of the pivoting directions, whether it is a right-hand or left-hand steering arm, a displacement takes place which is followed, in the opening sense, by the blocking pawl articulating at the actuating lever via the connecting element. Thus, it is possible to associate the actuating arm with a towing element which can be gripped and actuated from the tractor seat. Thus, an unlocking operation can be carried out when depositing or uncoupling the implement. To facilitate the uncoupling operation, the connecting ball joint eye, at the attaching end, is able to carry out vertical movements relative to the strut. In this way, distortion cannot occur. The ball joint eye and the attaching end are load-free so that the operative is able to unfasten the connection between the attaching end and the implement without having to apply any force. 
     In a preferred embodiment, the connecting element is in the form of a tow bar. The actuating lever is pivotally arranged on the tow bar. The longitudinal axis of the tow bar forms the axis of rotation of the actuating lever. The actuating lever, in at least one direction of the longitudinal axis which corresponds to the direction of movement of the tow bar into the open position, is firmly supported on the tow bar. 
     Particularly advantageous actuating conditions are obtained if two actuating levers are provided. The levers extend diametrically from the pivot axis of the actuating lever. Both levers are associated with a setting contour. This results in the connecting element being symmetrically loaded. The load on the guiding means for the connecting element is reduced. Accordingly, canting or jamming cannot occur. In a further embodiment of the invention, the blocking pawl is additionally secured by a pre-tensioned spring. The spring holds the blocking pawl in the recess. The actuating lever is associated with at least one securing arm. The securing arm is arranged to be circumferentially offset relative to the actuating arm. Thus, when the actuating arm is in the locked position, the securing arm is in contact with the base of the setting contour. Also, the securing arm is covered by a fixed securing projection which prevents the blocking pawl from being displaced into the open position. 
     To achieve symmetric loading, two securing arms are provided. The securing arms extend diametrically away from the pivot axis. An advantageous assembly is obtained if the recess of the strut and the blocking pawl, the actuating lever, the connecting element and the setting contour are associated with the attaching end which can be plugged onto the second end of the strut. In this case, the blocking pawl is received in a pocket of the attaching end. The connecting element, in the form of a tow bar, is guided outwardly and, on its outside, rotatably carries the actuating lever. 
     To secure the blocking pawl in the locked position, a stop bushing is provided. The stop bushing is arranged co-axially around the tow bar. The stop bushing is displaceably accommodated in the bore. On the one hand, the stop bushing is axially supported on the actuating lever held at the tow bar in only one longitudinal direction. On the other hand, the other end serves as a securing stop for the blocking pawl. 
     A spring disc is provided to load the actuating lever so that it is always held in contact with the setting contour. 
     Alternatively, the blocking pawl can be secured. Here, the actuating lever is connected to the tow bar so that it is axially unmovable. 
     From the following detailed description, taken in conjunction with the accompanying drawings and subjoined claims, other objects and advantages of the present invention will become apparent to those skilled in the art. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side plan view of a first lower steering arm assembly in accordance with the invention. 
     FIG. 2 is a plan view partially in section, and rotated ninety (90°) degrees, according to FIG.  1 . 
     FIG. 3 is an enlarged plan view of the attaching end according to FIG.  1 . 
     FIG. 4 is an enlarged section view of the selected region of FIG.  2 . 
     FIG. 5 is a partially in section diagrammatic view of the possible movements of the attaching end relative to the strut. 
     FIG. 6 is a section view like FIG. 4 of the attaching end relative to the strut in an extracted position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A first embodiment will be explained in greater detail with reference to FIGS. 1 to  6 . The lower steering arm assembly includes a strut  1  which is produced from a flat material. The strut  1  has two narrow faces  2  and the two side faces  3 ,  4 . A ball joint eye  6  is welded to the first end  5  of the strut  1 . The ball joint eye is pivotably secured to the tractor or to a self-driving implement. 
     The strut  1  defines a longitudinal axis  7  and has a second end  8  remote from its first end  5 . Towards the second end  8 , setting recesses  9  are worked into the strut  1 . The setting recesses  9  start from the narrow faces  2  and are positioned at a distance from the end face  10  at the second end  8 . Narrow faces  2   a  are in the region between the end of the setting recesses  9  and the end face  10 . The narrow faces  2   a  are stepped relative to the narrow faces  2 . The height of the strut  1  in the region between the narrow faces  2  is greater  10  than between the two narrow faces  2   a.    
     Two inclined faces  11  start at the end face  10 . The two inclined faces  11  end in the stepped narrow faces  2   a  and serve to center an attaching end  16 . A recess  12  is worked into the side face  3  of the strut, at a distance from the end face  10 . In the plan view, the recess  12  is circular. The recess  12  includes a longitudinal axis  12   a.  The recess  12  is in the form of a truncated, cone-shaped indentation. The inner face of the recess  12  forms the blocking face  13 . The blocking face  13  extends at an angle relative to the longitudinal axis  12   a  and ends with a curvature  14  in the bottom  15 . 
     The attaching end  16 , plugged onto to the second end  8  of the strut  1 , also includes a ball joint eye  17 . The eye  17  is connected to an implement to be attached or to be carried by the two lower steering arms arranged in parallel relative to one another at the tractor. The attaching end  16  includes two parts, a base member  18  and a cover  19 . The base member  18  is provided in the form of a forging. A pocket  21  starts from a planar face  20  of the forging. The pocket is limited by an outwardly directed curvature. The pocket  21  defines a bearing face  22  which is delimited by part of the inner face of a cylinder having an axis  33 . The pocket  21  provides support for a blocking pawl  34 . The base member  18  has a bearing recess  23  which accommodates a bearing ball  24 . The bearing ball  24  has a through-bore  25 . The through-bore  25  receives a receiving pin of the implement to be attached. 
     The cover  19  has a U-shaped cross-section and the two arms  26 ,  28 . The arms  26 ,  28  are connected to one another by a web  27 . The arms  26 ,  28  receive the base member  18  between them and are welded thereto. Towards the ball joint eye  17 , the cover  19  is provided with an end wall  29 . The inside of the end wall  29  forms the stop face  30 . An indentation  31  is provided in the area of transition between the inner face of the web  27  and the stop face  30 . The planar face  20  of the base member  18 , the inner faces of the two arms  26 ,  28  and of the web  27 , as well as the stop face  30  of the end wall  29  of the cover  19 , define a chamber  32 . The second end  8  of the strut is received in the chamber  32 . FIGS. 3 and 4 show the inserted condition. The attaching end  16  is fully plugged into the second end  8  of the strut  1 . The end face  10  of the strut  1  is in contact with the stop face  30 . The indentation  31  ensures that the end face  10  fully rests against the stop face  30 . Thus, positive supporting conditions exist. In addition, the two faces  10 ,  30  are locked to one another by a blocking pawl  34 . 
     The blocking pawl  34  has a supporting face  35 . The supporting face  35  is adapted to the inner face, blocking face  13 , and corresponds to the bearing face  22 . Thus, the blocking pawl  34  is pivotable around the pivot axis  33  which forms the cylinder axis. It can be seen that the pivot axis  33  is arranged at a distance from the longitudinal axis  12   a  of the recess  12  and intersects same at a right angle. 
     At the end facing away from the supporting face  35 , the blocking pawl  34  has a locking face  36 . The locking face  36  is adapted to the shape of the inner face  13  forming the blocking face and to the curvature  14  of the recess  12 . By selecting this shape, the pivot movement into the recess  12  is facilitated. FIG. 4 shows the engaged position. The blocking pawl  34 , by its locking face  36 , engages the recess  12 . The blocking pawl  34  holds the attaching end  16  on the second end  8  of the strut  1 . Thus, the strut  1  is able to apply tensile forces to the ball joint eye  17 . 
     The cover  19  is in the form of a formed plate metal part or casting. The cover  19  may be produced more accurately than the forged base member  1 . Thus, by associating the stop face  30  with the cover  19 , it is possible, when producing the connection between the base member  18  and the cover  19 , to compensate for any deviations. Compensation occurs by displacing the cover  19  relative to the base member  18 . Thus, it is possible to transfer the exact distance measurements of the recess  12  relative to the end face  10 . The end face is machined in a chip-forming way to the attaching end  16  to ensure that the blocking pawl  34  locks in as play-free a way as possible. The blocking pawl  34  includes a yoke-shaped portion. A tow bar  38  is received between the two yoke arms. The tow bar  38  is pivotably connected to the blocking pawl  34  by a transversely extending pin  39 . The tow bar  38  is cylindrical and guided outwardly through a bore  40  in the wall of the base member  18 . The bore  40  is in the region of the pocket  21 , which receives the blocking pawl  34 . A stop bushing  41  is positioned co-axially around the tow bar  38 . The stop bushing  41  is displaceable by a limited amount. The stop bushing  41  projects inwardly into the pocket  21  onto the blocking pawl  34  in the locked condition of the blocking pawl  34 . The bushing  34  is prevented from unintentionally pivoting into the unlocked position wherein the locking face  36  is disengaged from the recess  12 . An actuating lever  43  is attached to the outside of the tow bar  38 . A bore holds the actuating lever on the tow bar so as to be rotatable around the axis of rotation  38   a.  The axis of rotation  38   a  is defined by the longitudinal axis of the tow bar  38 . Furthermore, the actuating lever  43  is secured on the tow bar  38  against axial displacement in at least one direction by a pin  53 . A spring disc  52  is positioned between the pin  53  and the outer face of the actuating lever  43 . The spring disc  52  suppresses any play, even in the locked condition, to prevent the actuating lever  43  from rattling. The stop bushing  41  is supported by its other end against the actuating lever  43 . 
     The actuating lever  43  has four arms, two actuating arms  44 ,  45  and two securing arms  46 ,  47 . Actuating arm  44  is provided with a bore  60  to enable the connection of towing means. The two securing arms  46 ,  47  are arranged at a right angle relative to the two actuating arms  44 ,  45 . Thus, a kind of cruciform shape is obtained. In addition, the two actuating arms  44 ,  45  are crimped twice. Thus, the arms  44 ,  45  project towards the outer face of the base member  18  in the region of the curved pocket  21 . The outer face of the base member  18  is provided with a setting contour in the region of the pocket  21 . For the locked condition as illustrated in FIGS. 3 and 4, an indentation is provided with base  54 ,  55  to the right and to the left of the tow bar  38 . The two actuating arms  44 ,  45  rest on the base  54 ,  55  in the locked condition as illustrated in FIGS. 3 and 4. The arms  44 ,  45  are aligned substantially in the direction of the longitudinal axis  7 . 
     Setting faces rise from the base  54 ,  55 . Setting face  56  rises upwardly from the actuating arm  44 . Setting face  59  rises upwardly from the actuating arm  45 . Two rising setting faces  57 ,  58  are below the two actuating arms  44 ,  45 . As the two actuating arms  44 ,  45  are crimped twice, they rest against the setting contour of the outside of the base member  18  in the region of the second crimping. The actuating lever  43  is pivoted counter-clockwise around the axis of rotation  38   a  of the tow bar  38  due to a towing element being acted upon. Via the bore  60 , the lever  43  is articulated at the actuating arm  44 . The actuating arm  44  moves from the base  54  upwards on the rising setting face  56 . In order to achieve symmetric loading conditions, the second actuating arm  45  moves along the rising setting face  58  away from the base  55 . This means that a tensile force is applied to the tow bar  38 . The blocking pawl  34  is pivoted clockwise out of the recess  12  around the pivot axis  33  by its locking face  36 , into a position as shown in FIG.  6 . The stop bushing  41  also moves outwardly. 
     The blocking pawl  34  is additionally loaded towards its blocking position by a relatively strong leaf spring  31 . The pawl  34  is loaded counter-clockwise. At one end, the spring  37  is supported on the inner contour of the pocket  21 . The other end rests on the blocking pawl  34 . The spring  37  is connected thereto by a holding pin  42  inserted into a bore of the blocking pawl  34 . Furthermore, the spring  37  includes a slot through which the tow bar  38  is guided. Cams  48 ,  49  are on the outside of the base member  18 , in the region of the pocket  21  to secure the blocking pawl  34  in the locked position. The cams  48 ,  49  include projections in the form of securing pins  50 ,  51  projecting towards the tow bar  38 . In the locked condition, the securing arms  46 ,  47  are positioned underneath the securing pins  50 ,  51 . The stop bushing  41  is held in its inwardly displaced position because it is supported against the locked actuating lever  43  and cannot escape. The blocking pawl  34  is positioned in the recess  12 . When pivoted out of its engagement relative to the recess  12 , the blocking pawl  34  would stop against the stop bush  41 . When a tensile force acts on the actuating lever  43 , the tow bar  38  is not displaced and consequently neither is the blocking pawl  34 . In addition, this measure ensures that the blocking pawl  34  is locked. This means that even when vibrations occur, the blocking pawl  34  cannot pivot around the pivot axis  26  because its outer face comes to rest against the end face of the stop bushing  41 . The stop bushing  41  cannot escape outwardly. 
     After the blocking mechanism has been released, after the blocking pawl  34  has been transferred into a position as shown in FIG. 6, the attaching end  16  can be pulled forward, away from the second end  8 . FIG. 6 does not show the actual position of the actuating lever  43 . Instead, for the sake of clarity, the actuating lever  43  is shown in a fully displaced, outward position. The lever  43  is out of contact with the outer face of the base member  18 . FIG. 5, additionally, shows the attaching end  16  having been pivoted upwardly relative to the longitudinal axis  7  of the strut  1 . The two stepped blocking faces  2   a  extend in the region of the chamber  32 , while the faces of the shanks  26 ,  28  approach one another and change by following a constant course. 
     The inclined faces  11  assist centering onto this region. The extraction path of the attaching end  16  relative to the second end  8  is delimited by the stop pin  61 , which passes through the chamber  32 . The stop pin  61  is positioned in the region of a setting recess  9 . The setting recesses  9  enable the attaching end  16  to pivot, as illustrated in FIG.  5 . In addition, slight adjustment movements are possible in the horizontal direction. The pivoting possibility facilitates coupling of the implement to the tractor if there is a difference in height between the strut  1  and the attaching pin of the implement. After the implement has been coupled, it is possible, by reversing the tractor, to move the strut  1 , via its second end  8 , into the chamber  32  until the end face  10  comes to rest against the stop face  30  of the cover  19 . The blocking pawl  34  engages the recess  12  under the force of the spring  37 . The resistance required for driving in the strut  1  is provided by the weight of the implement to be coupled. 
     While the above detailed description describes the preferred embodiment of the present invention, the invention is susceptible to modification, variation and alteration without deviating from the scope and fair meaning of the subjoined claims.