Abstract:
The subject of the patent is a quick-change coupling for attaching work tools to an excavator boom, in which a respective coupling body part ( 1, 2 ) is disposed on the work tool and on the excavator boom, the two coupling body parts being mutually securable by a hook connection ( 3 ) and a wedge lock ( 4 ) having mutual bearing surfaces ( 5 ), and at least one coupling plate ( 14, 14 ′) being respectively provided on the work tool, on both sides of the longitudinal center plane and parallel to the latter, which coupling plates have, congruent with each other, the receiving recesses both of the hook connection ( 3 ) and of the wedge connection ( 4 ).

Description:
BACKGROUND OF THE INVENTION 
   Field of the Invention  
   The invention relates to a quick-change coupling for attaching work tools to an excavator boom, in which a respective coupling body part is disposed on the work tool and on the excavator boom, the two coupling body parts being mutually securable by a hook connection and a wedge lock having mutual bearing surfaces. 
   In a known configuration of this type, the receiving recesses of the hook connections, and the bearing surface, as well as the wedge lock, are disposed on the work tool in offset arrangement in a plane parallel to the transverse center plane, the hooks of the hook connection being provided symmetrical to the transverse center plane on the work tool and the bearing surface and the wedge lock acting essentially in the region of the transverse center plane. Such a configuration has the drawback that a plurality of different receiving members have to be provided, which, because of the lateral offset one to the other, are subjected to strong bending forces if the work tool is placed under uneven load. 
   SUMMARY OF THE INVENTION 
   According to the invention, these stated drawbacks are avoided by the fact that on the work tool, on both sides of the longitudinal center plane and parallel to the latter, there is respectively provided at least one coupling plate, which coupling plates have, congruent with each other, the receiving recesses both of the hook connection and of the wedge connection. The fact that the receiving recesses both for the hook connection and for the wedge connection are provided congruent with each other on either side of the longitudinal center plane means that the forces which arise are imparted evenly to the coupling plates, the coupling plates between the hook connection and the wedge connection being respectively subjected only to tensile load. This is because the hook connection, on the one hand, and the bearing surfaces, on the other hand, are oppositely directed and the wedge connection causes the bearing surfaces to be mutually displaced in such a way that the receiving recess of the wedge connection, in relation to the hook connection, and the bearing surfaces are forced away from each other. 
   Advantageously, on the excavator boom, on both sides of the plane of inflexion of the boom in the state coupled to the coupling plates, support plates can be provided, running parallel on the tool, for the counterparts which are to be hung or secured in the recesses of the coupling plates. Thus, the transfer of force to the support plates attached to the excavator boom is also realized essentially in respectively one plane, so that these support plates, too, can disperse the imparted forces within the planes of the support plate. The counterpart for the wedge lock can herein be formed by a wedge bar running transversely to the planes of the support plates, which is guided in a track rising obliquely away from the work tool. It is thus easily brought about that, when the wedge member is displaced in the support plates, these are pulled in the direction of the work tool, whereby the corresponding pressing of the bearing surfaces and thus also of the hook connection is obtained. The wedge bar can then pass through the support plates and protrude on those outer sides of the support plates which are facing away from the excavator boom, the wedge profile being provided on both sides of each of the support plates. It is thus possible, with one and the same coupling part attached to the excavator boom, to receive work tools in which the coupling plates are fitted to the work tool either within the support plates, or, indeed, outside of the plate, i.e. distanced further apart. This is achieved in identical manner for the hook connection by the fact that the counterparts for the hook connection are formed by a transverse bar which passes through the support plates and protrudes on those outer sides of the support plates which are facing away from the excavator boom. For the actuation of the wedge bar, a hydraulic piston-cylinder unit can preferably be provided, which, when the wedge lock is unlocked, is fully extended. This has the advantage that the piston area which is available in the locking of the wedge connection, because of the fitted piston rod, is less than for the release of the wedge lock, thereby preventing possible jamming of the wedge connection inasmuch as greater forces can be applied in the release operation than in the locking operation. 
   In order for the work tools to be able to be fitted both for low-level digging and for high-level digging, i.e. in oppositely directed arrangement, the receiving recesses of the coupling plate can be configured symmetrically in relation to the vertical center plane running transversely to the plane of the plate. Furthermore, on both sides of the longitudinal center plane two coupling plates can respectively be provided, the support plates being able to be inserted into the interspace between the adjacent coupling plates. For larger work tools, in particular, very stable coupling parts can thus be achieved on the work tool. In order to make the forces impact, as far as possible, only upon the connecting members, the hydraulic piston-cylinder unit can be supported, by its end facing away from the wedge bar, against the transverse bar belonging to the hook connection. Finally, for the support of the hydraulic piston-cylinder unit in the direction of fastening of the excavator boom, cranked links are provided, which are prevented from pivoting relative to the support plates. The effect is that the hydraulic piston-cylinder unit is aligned with its longitudinal axis directly in the motional direction of the beam having the wedge surfaces. In order to keep the reciprocally moving parts of the hydraulic piston-cylinder unit free from inadmissible forces, the connection between the hydraulic piston-cylinder unit and the wedge bar can be realized with a reserved clearance. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Various illustrative embodiments of the subject of the invention are represented in the drawing. 
       FIG. 1  shows a first embodiment in diagrammatic representation in the coupled state of the two coupling parts. 
       FIG. 2  is a side view, 
       FIG. 3  a front view and 
       FIG. 4  a top view of the configuration according to  FIG. 1 . In the representation, both the excavator boom and the work tool are in this case omitted, so as not to complicate the representation. 
       FIG. 5  shows the coupling part to be fitted to the excavator boom alone, without the coupling part present on the work tool, this in side view. 
       FIG. 6  is a top view of this coupling part, 
       FIG. 7  depicts a section along the line A—A of  FIG. 6 , and 
       FIG. 8  a section along the line C—C of  FIG. 6 . 
       FIG. 9  shows in diagrammatic representation a first embodiment of the coupling part to be fitted to the work tool. 
       FIG. 10  is a side view of this coupling part represented in  FIG. 9 . 
       FIG. 11  depicts a further embodiment of the coupling part to be fitted or present on the work tool, in diagrammatic representation. 
       FIG. 12  is an associated side view. 
   

   With respect to the coupling part to be fitted to the work tool, it should further be noted that the coupling parts jutting away from the work tool do not necessarily need to be plurally present on each side, as depicted in  FIGS. 9 and 11 , but rather it is also sufficient for certain usage variants for the vertical parts to be provided only individually on each side of the longitudinal center, in which case it is possible, according to requirement, for the corresponding vertical portions of the coupling part to be able to be disposed either on the inner sides or, indeed, on the outer sides of the coupling part, which coupling part is sunken relative to the excavator boom. 
   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The quick-change coupling according to the invention has a coupling part  1  to be attached to the excavator boom, and a coupling part  2  to be attached to the work tool, the two coupling parts being joined together, on the one hand, by a hook connection  3  and, on the other hand, by a wedge connection  4 , both coupling parts additionally being provided with mutually interacting, oblique stop-face bearing surfaces  5 , which are pressed one against the other by the wedge connection in order to obtain a play-free fit of the two coupling parts. 
   The coupling part  1  to be attached to the excavator boom has eyelets  6 ,  7 , through which the fastening bolts for the attachment to the excavator boom can be pushed and secured therein. 
   In order to obtain the hook connection  3 , a transverse bar  8 , for engagement in the hooks provided on the coupling part  2  to be attached to the work tool, is disposed on the coupling part  1  to be attached to the excavator boom. The wedge connection is formed by a bar  10 , which runs parallel to the transverse bar  8  and is truncated in a wedge shape in the region of the wedge connection, as counterfaces on the coupling part  2  stop faces  11  being provided, along which the wedge bar  10  can be moved such that the coupling part  1  is pulled into the coupling part  2 . For the mutual securement of the two coupling parts, the mutual bearing surfaces  5  are formed by the provision on the coupling part  1  of a pressure plate  12 , which can be brought to bear against corresponding opposing contact surfaces  13  on the coupling part  2 . The inclination of the pressure plate  12  roughly corresponds, in the coupled state, to the inclination of the opposing bearing surface  13 , so that, when the wedge connection is actuated, a mutual tensioning is obtained between the wedge connection and the bearing surfaces, which tensioning additionally has the effect, due to the inclination of the bearing surfaces  5 , of forcing the transverse bar  8  into the hooks  9 . For the displacement of the wedge bar  10 , a hydraulic piston-cylinder unit  15  is provided, which is arranged such that, for the insertion of the wedge bar  10  on the corresponding opposing wedge surfaces  11 , the hydraulic piston-cylinder unit is pressurized in the direction of a shortening of the same. This has the advantage that a higher pressure can be applied for opening purposes than for the insertion of the wedge connection, whereby possible jams can be prevented or such jams can be more easily resolved. For the configuration of the hook  9 , of the wedge stop face  11  and of the opposing bearing surface  13 , the coupling part  2  to be attached to the work tool is formed by coupling plates  14 ,  14 ′, which are disposed symmetrically in relation to the longitudinal center plane of the work tool. These coupling plates  14 ,  14 ′ stand parallel to each other and are attached to a support plate  18 . Cross connections for connecting the plates one to another are not provided. 
   In the case of the coupling part  1  to be attached to the excavator boom, support plates  16  are provided, which, on the one hand, support the eyelets  6 ,  7  and, on the other hand, support the transverse bar  8  for hanging the coupling part  1  in the hooks  9  of the coupling part  2 , the transverse bar  8  joining together the two support plates  16  and jutting beyond these on their outer side on both sides. Furthermore, the two support plates  16 , which likewise run parallel to each other and are disposed symmetrically to the longitudinal center plane of the work tool and also to the plane of inflexion of the excavator boom, are further joined together by the pressure plate  12 . 
   Additionally provided between these two support plates  16  is a connecting web  17 , which is hung by a middle link  20  from the transverse bar  8  and to which, jutting away therefrom, on the side facing away from the link  12 , two mounting links  21  are fitted, between which the hydraulic piston-cylinder unit  15  is pivotably fastened. The connecting link  20 , and also the two mounting links  21 , are respectively cranked in the direction of the retaining eyelets  6 ,  7 , whereby the longitudinal axis of the hydraulic piston-cylinder unit  15  comes to lie roughly in the motional direction of the wedge bar  10 . The wedge bar  10  is guided in the support plates  16  by means of slots  23  and juts over the support plates on both sides on their outer side. The wedge surfaces on the wedge bar  10  are here provided both at the regions located between and adjacent to the support plates  16  and at the regions jutting externally over the support plates  16 . The hydraulic piston-cylinder unit  15  engages centrally on the wedge bar  10 , the wedge bar  10  being guided in the axial direction by a guide plate  22 . As a result of the connection, it is possible for no moments whatsoever to be transmitted to the hydraulic piston-cylinder unit by possible wedge movements, e.g. pivoting about its longitudinal axis. Apart from the pivotable mounting of the hydraulic piston-cylinder unit, this is additionally achieved by the fact that the piston rod is connected to the wedge bar  10  with play and, to be precise, in such a way that, on the one hand, the inner diameter of the eyelet of the piston rod is greater than the outer diameter of the wedge bar  10  (approximately 1 mm difference) and that, on the other hand, the holding plates provided for the axial securement of the eye of the piston rod to the wedge bar are attached to the wedge bar at a distance (approximately 2 mm) from the eyelet. Fitted to these holding plates are the guide plates  22 . Thus, if the wedge is slightly slanted, for example, the reciprocally moving parts of the hydraulic piston-cylinder unit are not placed under inadmissible load. 
   The wedge bar  10  is continuously configured such that it is kept solid, i.e. circular, in the region of the fitting of the hydraulic piston-cylinder unit and is truncated to form a wedge surface on both sides of the connecting link of the hydraulic piston-cylinder unit. 
   In the illustrative embodiment of the coupling part  2  to be attached to the work tool, according to  FIGS. 9 and 10 , this coupling part is configured symmetrically also in relation to the vertical longitudinal center plane of the work tool, i.e. on each coupling plate, a hook  9 ′, directed oppositely to the hook  9 , for the hook connection  3 , and corresponding oppositely directed counterfaces  11 ′ for the wedge connection  4 , and  13 ′ for the bearing contact of the pressure plate  12 , are provided. This is designed to allow, for example, an excavator bucket, on the one hand, for low-level operations with the opening downward or, on the other hand, for high-level operations with the opening upward, to be fitted using one and the same coupling tool. According to  FIG. 2 , in addition to the coupling plates  14 , coupling plates  19  are herein provided, which are configured and disposed congruent with the coupling plates  14 , the distance between the plates  14  and  19  being dimensioned such that the support plates  16  of the coupling part  1  can engage therebetween. The support plate  14  then engages respectively in those regions of the transverse bar  8 , of the wedge bar  10  and of the support plate  12  which are located on the outer sides of the support plate  16 , the plates  19  acting upon those regions of the transverse bar  8 , of the wedge bar  10  and of the support plate  12  which are located on the inner side of the support plate  16 . 
   The embodiment according to  FIGS. 11 and 12  is designed for simple fitting, i.e. such that the coupling part  2  is non-symmetrical in relation to the longitudinal center plane of the work tool, so that the relevant work tool can only be fitted in a certain direction. Accordingly, each coupling plate  14  of the coupling part  2  has only one hook region  9  and a wedge contact surface  11  and contact surface  13  for the pressure plate  12 . The additional hook coupling plates  19 ′ are provided only in the hook region, but not in the region of the wedge connection or pressure plate. 
   An essential feature of the fast-change coupling according to the invention lies in the fact that the mutual support for the individual parts of the hook connection in relation to the wedge connection runs respectively in mutually parallel planes, so that both the coupling plates  14  and  19  and the support plates  16  are respectively subjected only to tensile load, thereby preventing any bowing or curving of the plates. 
   Labeled  24  and  24 ′, a free space is respectively provided between the wedge stop face  11  and  11 ′ and the opposing bearing surface  13  and  13 ′, which free space is dimensioned such that the pressure plate  12  can be moved through simultaneously with the fully pushed-back wedge bar  10  in order to bring the pressure plate  12  to bear against the opposing pressure plate  13  and move the wedge bar  10  against the wedge stop face  11 . 
   In order to couple a tool to an excavator boom, the excavator boom with its coupling part  1  is lowered such that the transverse bar  8  engages in the hook  9  of the hook connection  3 , after which the pressure plate  12 , together with the wedge bar  10 , is then lowered, by pivoting of the coupling part  1 , through the free interspace  24 , until the pressure plate  12  comes to bear against the opposing bearing surface  13 . After this, the wedge bar  10  is moved in the direction of the wedge stop face  11  with the aid of the hydraulic piston-cylinder unit  15 , and following contact with the wedge bar  10 , is displaced on this wedge stop face  11  transversely to the longitudinal direction of the wedge bar until the pressure plate  12  bears tight against the opposing bearing surface  13 , whereupon, due to the inclination of the individual parts, the coupling part  1  is displaced along the opposing bearing surface  13  in such a way in the direction of the hook  9  that the transverse bar  8  is mounted in a play-free manner in the hook  9 . The hydraulic piston-cylinder unit is then fixed in this position and the pressure maintained until such time as decoupling is due to take place. 
   When the work activity is completed, the work tool is set up on the ground, after which the hydraulic piston-cylinder unit  15  is pressurized in the direction of an extension, the effect of which is that the wedge bar  10  is now moved away from the wedge stop face  11 , to be precise to the point where the wedge bar  10  ends up in the region of the free interspace  24 . After this, through pivoting of the coupling part  1  about the transverse bar  8  in the hook  9  of the hook connection  3 , the coupling part  1  can be released from the coupling part  2  in the region of the bearing surfaces  5  and of the wedge connection  4  and the transverse bar  8  can then be moved out of the hook  9  of the hook connection  3 . 
   If, in the illustrative embodiment according to  FIGS. 9 and 10 , the work tool is intended to be coupled to the excavator boom such that it is differently directed, i.e. twisted by 180°, then the coupling is realized via the hooks  9 ′, the wedge stop faces  11 ′ and the opposing bearing surface  13 ′, in which case the hooks  9 , the wedge stop faces  11  and the opposing bearing surface  13  are redundant.