Abstract:
A method and an apparatus serve to secure a gripper tool detachably to a movable crossbar of a transfer press. The gripper tool has two saddles, with spacing between them, which are brought into engagement with two bearings mounted on the crossbar and locked in a defined engagement position. To attain faster, simpler assembly, the gripper tool is introduced in an inclined position relative to the crossbar, by at least one protrusion of rounded longitudinal section or tapering in wedgelike fashion, on the first saddle, into a correspondingly rounded or V-shaped narrowing recess in the first bearing. The second saddle is then pivoted toward the crossbar. In the process, wedge faces on the second saddle and on the second bearing press the protrusion axially against the wall of the recess by the force of gravity. In the end position, the second saddle is locked to the second bearing.

Description:
FIELD OF THE INVENTION 
   The invention relates to a method for detachably securing a gripper tool to a movable transverse beam, normally called crossbar, of a transfer press, which gripper tool has two saddles disposed with spacing between them and with them is brought into engagement with two bearings mounted on the crossbar and is locked in a defined engagement position, and to a bearing assembly for performing such a method. 
   BACKGROUND OF THE INVENTION 
   From U.S. Pat. No. 5,746,567, it is known for a gripper tool, comprising two saddles and two supporting tubes to which suction grippers are secured, to be placed first with both saddles on the crossbar of a transfer press and then displaced along the crossbar, overcoming friction, by means of a clamping and locking lever in order to bring parallel wedge faces on both sides simultaneously into contact with corresponding wedge faces on bearings fixedly connected to the crossbar, and furthermore during this motion to introduce centering bolts into fitting centering bores on the saddles and bearings, respectively. The time and force required for horizontally displacing the gripper tool on the crossbar and forcing it between the crossbars is problematic. 
   OBJECT AND SUMMARY OF THE INVENTION 
   It is therefore the object of the invention to make a method and a bearing assembly of the type defined above available that permit faster, simpler, positionally precise fastening and fixation of the gripper tool to the crossbar. 
   This object is attained in terms of the method, as proposed by the invention, in that the gripper tool, in an inclined position relative to the center longitudinal axis of the crossbar, is introduced, with at least one protrusion of rounded longitudinal section or tapering in wedgelike fashion, on the first saddle into a correspondingly rounded or V-shaped narrowing recess in the first bearing and is then pivoted with the second saddle toward the crossbar, whereupon wedge faces on the second saddle and on the second bearing press the protrusion by the force of gravity axially against the wall of the recess, and then the second saddle is locked to the second bearing. 
   The invention offers the advantage that for precise positioning of the gripper tool, it suffices to introduce one end of it, having the protrusion, into the associated recess in the first bearing and then to lower the other end of the gripper tool or let it drop. During this pivoting motion, the cooperating wedge faces on the second saddle and on the second bearing come into contact with one another and automatically push the gripper tool into its predetermined position relative to the crossbar. In this end position, the gripper tool is clamped between the wedge face on the second bearing and the recess on the first bearing. Next, this end position of the gripper tool merely needs to be secured by locking the second saddle to the second bearing. To that end, preferably at least one locking bolt, axially guided in the second bearing, is introduced, in the direction parallel to the center longitudinal axis of the crossbar, into a fitting bore in the second saddle. In the process, by means of cooperating wedge or conical faces on the locking bolt and on the bore, it can be assured that in a case where the gripper tool is not yet aligned precisely parallel to the center longitudinal axis of the crossbar, it is pivoted a little farther during the locking until it reaches the predetermined end position. 
   In a further preferred feature of the invention, in the pivoting of the gripper tool into the predetermined end position, underpressure supply lines are connected to underpressure lines on the tool via cooperating pneumatic couplings on the second bearing and on the second saddle. Since the pivoting of the gripper tool takes place automatically by gravity, for this coupling operation as well no additional manipulation or expenditure of force is needed. 
   The bearing assembly of the invention is distinguished in that the first saddle can be introduced, with at least one protrusion mounted on it and having a rounded longitudinal section or tapering in wedgelike fashion, already in an inclined position of the gripper tool relative to the center longitudinal axis of the crossbar, into a correspondingly rounded or V-shaped narrowing recess in the first bearing, and in the engagement position the gripper tool can be pivoted with the second saddle toward the crossbar; that the second saddle and the second bearing are provided with wedge faces, which in the course of the pivoting motion come to rest on one another, by which faces the protrusion can be pressed axially against the wall of the recess by the force of gravity; and that in this braced position, the second saddle can be locked to the second bearing. 
   On its free end the protrusion may have an approximately semicylindrical shape, for example, with a cylinder axis that in the mounted state of the gripper tool extends horizontally. In that case, the rounded recess should be embodied correspondingly hollow-cylindrically, expediently with a widened entrance region. Alternatively, the free end of the protrusion could be embodied with an upper and a lower wedge face, and the recess could be designed with complementary counterpart faces. In the preferred embodiment, however, two protrusions which on the free end are substantially in the shape of a spherical cap are mounted on the axially outer side of the first saddle and can be introduced into corresponding spherical caplike concave recesses with a conically widened entrance region in parts of the first bearing that are mounted on the side faces of the crossbar. The two spherical caplike protrusions, which in the mounted state are located horizontally side by side, permit simple introduction into the spherical cap shaped concave recesses with a widened entrance region, but then guide the gripper tool reliably into a position aligned with the longitudinal center plane of the crossbar, in which position the end phase of the pivoting motion occurs as the gripper tool is set down onto the crossbar. 
   On the end of the gripper tool opposite from the spherical caplike protrusions, in a further preferred feature of the invention, two wedges are mounted, with space between them, side by side on the axially outer side of the second saddle, and their effective outer wedge faces recede axially from top to bottom and come to rest on corresponding wedge faces, which are embodied on parts of the second bearing that are mounted on the side faces of the crossbar. Once again, the paired arrangement of wedge faces with a relatively great spacing between them is favorable for automatically aligning the gripper tool with the center longitudinal plane of the crossbar. For the same reason, if possible, the two wedge faces on the second saddle should be located in the same straight plane. 
   The locking of the gripper tool in its predetermined position is intended to cause it to maintain its position on the crossbar. In a preferred feature of the invention, this is attained in a simple way by providing that on each of the two lateral parts of the second bearing, one locking bolt each, extending in the longitudinal direction of the crossbar, is supported axially displaceably and in the wedged position can be introduced through the wedge faces into an aligned bore in the associated wedge on the second saddle. Because in this version the free end of the locking bolt and/or the entrance region of the bore is embodied as wedge-shaped or conical, it is attained that the locking bolt contributes to pulling the second saddle into the predetermined end position on the crossbar. Moreover, by a suitable disposition and dimensioning of the parts, it is attained that the wedges connected to the second saddle, as they are lowered or dropped down, automatically press the locking bolts, which are preferably prestressed in the locking direction by springs, back until they snap into the associated bores and lock there. 
   In the same way as the automatic positioning and locking are attained, the pneumatic connections of the gripper tool can also be automatically connected to one or more supply lines, in that the second bearing and the second saddle are provided with coupling parts, fitting one another, of pneumatic couplings of one or more underpressure lines, which enter into coupling engagement upon pivoting of the gripper tool into the wedged position. 
   An exemplary embodiment of the invention will be described in further detail below in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a plan view on a movable crossbar of a transfer press, with two gripper tools secured to it, whose suction grippers in this example support a side panel of a motor vehicle; 
       FIG. 2  is an oblique view of the inside of a first saddle of one of the two gripper tools of  FIG. 1 , immediately before it is connected to the crossbar; 
       FIG. 3  is an oblique view of the outside of the first saddle of  FIG. 2 , after its connection to the crossbar; 
       FIG. 4  is an oblique view of the outside of the second saddle of one of the gripper tools of  FIG. 1  in the mounted state; 
       FIG. 5  is a side view, partly in longitudinal section through the second bearing with a locking bolt and through the parts that are secured to the second saddle and cooperate with the second bearing; as in  FIGS. 2 through 4 , for the sake of clarity of the drawing, neither the crossbar nor in this case the second saddle either is shown; 
       FIG. 6  is a cross sectional view of the first saddle of one of the two gripper tools taken along line  6 - 6  of  FIG. 2 ; and 
       FIG. 7  is a cross sectional view of another first saddle of one of the two gripper tools in accordance with an alternative embodiment in accordance with the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows only schematically, and not in detail, the attachment of two gripper tools according to the invention to the transversely movable crossbar  10  of a large-scale transfer press. The gripper tools, identified overall by reference numeral  12  (and also known as suction bridges), each comprise two axially spaced-apart saddles  14 ,  16 , which are solidly joined to two axially extending tubes  18 , for instance of aluminum, and form an intrinsically rigid unit. Suction grippers  20  connected to a source of underpressure are secured to the tubes  18  in such a form and arrangement that overall they can grasp and hold a certain workpiece  22  at predetermined points, in order to transport it from one processing station of the large-scale transfer press to the next. If a workpiece of a different shape is then to be formed on the press, the gripper tools  12  are replaced by the same kind of gripper tools, which can be secured in the same way to the same point of the crossbar, but which differ only in the shape and disposition of the section grippers  20 . 
   Because of the high capital investment costs of large-scale transfer presses, the changeover times for removing certain gripper tools and installing gripper tools adapted to the next workpiece to be processed or machined must be as short as possible. Moreover, despite short changeover times, the system for securing the gripper tools  12  must assure very precise positioning and reliable locking in the predetermined position. 
   As in the fastening system described in U.S. Pat. No. 5,746,567, the gripper tools  12  are set down from above onto the crossbar  10  with their saddles  14 ,  16 , so that in the mounted state, the essentially U-shaped saddles  14 ,  16  are seated on the top of the crossbar  10  and embrace its upper side edges. For precise positioning and locking of the saddles  14 ,  16 , a first bearing  24 , shown in  FIGS. 2 and 3 , and a second bearing  26 , shown in  FIGS. 4 and 5 , are fixedly attached to the crossbar  10 , spaced apart from one another. The proposed, novel method and the novel bearing assembly proposed for performing it differ from the known bearing assembly of U.S. Pat. No. 5,746,567 in the type of positioning and fastening means mounted on the respective cooperating bearings and saddles and in the manipulation during the changeover. 
   In  FIGS. 2 ,  3  and  6  with reference to the gripper tool  12  shown on the left in  FIG. 1 , the outer, first saddle  14  is shown with details, along with the first bearing  24  secured to the crossbar  10 , not shown. The U-shaped recess through which the crossbar  10  extends is identified by reference numeral  28 . For connection to the tubes  18 , the saddle  14  is embodied with longitudinally divided fitting bores on the sides. The divided outer side parts  30  of the saddle  14  are joined to its middle part by clamping screws  32 . The tubes  18  are firmly fastened in the bores that receive them by tightening the clamping screws  32 . 
   The bearing  24 , cooperating with the first saddle  14  and secured to the crossbar  10 , comprises two bearing halves of matching shape, each of which is mounted on one side of the crossbar  10 . The two halves of the bearing  24 , in this example, are screwed together via bolts  34  that extend horizontally crosswise through the crossbar  10 . As a result of the bracing to the crossbar  10  via the bolts  34  or corresponding tubes, the two halves of the first bearing  24  are seated immovably firmly in a parallel arrangement on the side faces of the crossbar  10 . Alternatively, the bearing halves could be screwed individually to the side faces of the crossbar. 
   Each of the two halves of the first bearing  24  comprises a solid L-shaped angle piece of steel, whose lower leg  36 , in the mounted state, extends horizontally in the longitudinal direction of the crossbar  10 . At its axially outer end, it changes over into a vertically upward-extending leg  38 . In the mounted state of the gripper tool  12 , it is located on the axially outer side of the first saddle  14 . A rounded recess  40  is machined into the vertical leg  38 , on its axially inner side, toward the saddle  14 . In this example, this recess has the form of a circular, axially extending blind bore, with a not entirely hemispherical caplike concave inner region and with an entrance region that widens conically toward the outside. 
   For cooperation with the bearing  24  having the two rounded recesses  40 , two spherically rounded protrusions  42  are mounted on the outside of the first saddle  14 , with the same transverse spacing as the recesses  40  in the bearing  24  and adapted to the spherical caplike concave cross section of those recesses. (See, e.g.  FIG. 6 .) Behind the approximately hemispherical outer end, the cross section of the protrusions  42  tapers. This tapering, like the widening of the entrance region of the recesses  40 , serves the purpose of being able to introduce the protrusions  42  into the recesses  40  in a position of the gripper tool  12  that is inclined, obliquely dropping, toward the first saddle  14 , while the saddle  14  is braced on the horizontal legs  36  of the bearing  24 . In the lowering of the second saddle  16 , the rounded protrusion  42  can penetrate all the way into the rounded recess  40 . At the end, the saddle  14  is centered relative to the cross section of the crossbar  10  by the engagement of the protrusions  42  with the recesses  40 , or in other words is aligned precisely in terms of both level and laterally. 
   The second saddle  16 , shown in its details in  FIGS. 4 and 5  along with the second bearing  26 , is solidly joined to the tubes  18  in the same way as the first saddle  14 . The U-shaped inner recess for receiving the crossbar  10  also matches the corresponding recess  28  of the first saddle  14 . In a distinction from it, however, on the axially outer side of the second saddle  16  to both sides of the U-shaped recess, a respective wedge  44  is mounted, whose axially outer effective wedge face  44 ′, in the mounted state, approaches the axially outer face of the second saddle  16  from the top, moving downward. As seen from  FIG. 5 , each wedge  44  is solidly connected to a solid, L-shaped angle piece  48  and braced via screw bolts  46 , which extend axially through the second saddle  16 ; this angle piece has coupling halves, not shown, of pneumatic couplings and also has line connections  50  for underpressure lines, which supply the suction grippers  20  with underpressure. 
   The second bearing  26 , in a way corresponding to the first bearing  24 , comprises two L-shaped angle pieces, mounted on the side faces of the crossbar  10  and joined to one another and to the crossbar  10  by screw bolts  34 , each with one horizontal leg  51 , extending in the longitudinal direction of the crossbar  10  in the mounted state, and one vertical leg  52 , rising in front of the axially outer side of the second saddle  16 . The axially inner side of each vertical leg  52  is provided with a wedge face  52 ′ that fits the axially outer wedge face  44 ′ of the wedge  44 . In the mounted state of the gripper tool shown in  FIGS. 4 and 5 , the wedge faces  44 ′ and  52 ′ rest flatly on one another, while the tubes  18  extend parallel to the center longitudinal axis of the crossbar  10 . This mounted end position is secured by two locking bolts  54 , which extend, likewise each parallel to the center longitudinal axis of the crossbar  10 , through the associated wedgelike vertical leg  52  of the second bearing  26  and engage a fitting axial bore  56  in the wedge  44 . Each locking bolt  54  is embodied with a conical oblique face on its free end, and the entrance region of the bore  56  in this example is also provided with a conical widening. Each locking bolt  54  is prestressed in the locking direction by a spring, not shown, but may also be retracted to a neutral position by means of a handle  58  mounted on it, by rotation via a cam guide, in which neutral position the handle  58 , which points downward in the locking position, points vertically upward. 
   Coupling halves, not shown, of pneumatic couplings are mounted on the horizontal legs  51  of the second bearing  26 ; in the mounted position shown in  FIGS. 4 and 5 , they are in aligned engagement with the correspondingly embodied halves, mounted on the second saddle  16 , of the pneumatic couplings, so that the aforementioned underpressure lines of the suction grippers  20  are connected to underpressure supply lines, not shown, via the connections  50 , the pneumatic couplings, not shown, and line connections  60  disposed on the underside of the horizontal legs  51  of the second bearing  26 . 
   Mounting the gripper tools  12  on the crossbar  10  is very simple and proceeds largely automatically, despite the simple mechanical means described. At the beginning of the assembly process it suffices to set the first saddle  14  down on the horizontal legs  36  of the first bearing  24  and, in a slanting position of the tubes  18  relative to this bearing, to introduce the rounded protrusions  42  into the rounded recesses  40 . After that, one need merely allow the other end of the gripper tool  12 , that is, the second saddle  16 , to drop from a low height onto the second bearing  26 . In the falling motion, the lower ends of the wedges  44  press the locking bolts  54  axially outward back; the wedge faces  44 ′ and  52 ′ come to rest on one another, and as a result of the wedging action, the overall gripper tool  12  is displaced axially farther toward the first bearing  24 , so that there the protrusions  42 , with their hemispherical free ends, come into contact with the hemispherical concave bottom faces of the recesses  40 , and the gripper tool  12  is axially firmly fastened between this axial bearing point and the wedge faces  52 ′ and is thereby exactly positioned. The locking bolts  54  in cooperation with their receiving bores  56  provide for the maintaining of this situation. Normally, the second saddle  16  drops on its own far enough that the locking bolts  54  are aligned with the receiving bores  56 . Should that not yet be entirely the case, a sufficiently strong spring prestressing of the locking bolts, optionally supplemented by manual pressure, forces their conical free end into the associated receiving bore and thus forces the second saddle  16  into the predetermined mounted position, in which the tubes  18  extend horizontally and parallel to the center longitudinal axis of the crossbar  10 . 
   It is understood that the locking bolt may engage the second saddle  16 , or some part connected to it, in a different position and/or at a different point. However, the locking arrangement proposed in the exemplary embodiment on the wedge faces  44 ′,  52 ′ which are required anyway for precise positioning is more economical than another version, with which the attempt is again made to cause the locking bolts to engage automatically. A further consideration is that the locking bolts  54  in cooperation with the receiving bores  56  assure a precise lateral alignment of the second saddle/16 relative to the crossbar  10 . 
   Alternative embodiments are also possible in the design of the rounded protrusions  42  and of the recesses  40 . Instead of a hemispherical free end of the protrusions  42 , a semicylindrical free end of the protrusions  42 , for example, with a horizontal cylinder axis extending crosswise to the longitudinal direction of the crossbar  10 , or a wedge, or a wedgelike free end with one upper and one lower wedge face, could be employed. For example, referring to  FIG. 7 , with a wedgelike shaped free end or protrusion  42 ′ and corresponding recess  40 ′, the functionally required pivoting motion of the gripper tool  12  in the assembly on the crossbar  10  can also be executed. 
   It is understood that furthermore the external shape of the saddles  14 ,  16 , their connection to the tubes  18 , and the external shape of the bearings  24 ,  26  and their connection to the crossbar  10  allow many different variant embodiments. For instance, the protrusions  42  may be mounted on the bearing  24  and the recesses  40  on the saddle  14 , and they can equally well, as optionally can the wedge faces  44 ′,  52 ′, be located on the axially inner side of the respective saddle  14  or  16 . Such modifications are no problem, as long as the inward pivoting of the gripper tool  12  as shown and described above into the predetermined position on the crossbar  10  can be executed.