Patent Publication Number: US-2022234218-A1

Title: Tool changer for a robot and changing system therefor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a National Stage Application filed under 35 U.S.C. 371 based on International Patent Application No. PCT/EP2020/070214, filed on Jul. 16, 2020, which claims priority to German Patent Application 10 2019 119 657.4 filed Jul. 19, 2019. The entire disclosures of each of the foregoing are hereby incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     Field of Invention 
     The invention relates to a tool changer for a robot, comprising a base unit, a changing unit which can be locked on the base unit, movable locking elements which are provided on the base unit, and receptacles which are provided on the changing unit, the locking elements interacting with the receptacles in a locking position in order to lock the changing unit on the base unit and releasing the receptacles in an unlocking position, said tool changer also comprising a rotary element which is provided on the base unit and rotatably mounted about its longitudinal axis, the locking elements being movement-coupled to the rotary element in such a way that the locking elements are moved when the rotary element is rotated. 
     The base unit is in particular designed in such a way that it can be arranged on the free end of a robot arm. The changing unit is in particular designed in such a way that it is configured for arrangement on a tool or gripping unit. 
     Description of Prior Art 
     Robots are used in industrial assembly lines and for other manufacturing applications to perform repetitive tasks with a high degree of accuracy. For example, robots are commonly used in the automotive industry to perform a number of tasks such as material handling, cutting, welding, joining, and the like. 
     A tool changer as mentioned at the outset is known, for example, from DE 112009002163 T5. The locking elements are designed as rolling bodies here. In this case, a piston with cam faces having several facets that act against the rolling bodies is known as a rotary element for activating the locking elements. 
     Furthermore, a machine tool having a tool changing device is known from DE 33 46 467 A1. The tool changing device has a double-ended changing arm which is arranged so as to be pivotable about an axis parallel to the spindle axis and is provided with a tool gripper at each end. 
     A tool changing apparatus for a welding robot is known from DE 40 10 070 C1. Two closure hooks are provided as locking elements. A piston acts on a toggle joint in a spring-loaded manner such that the closure hooks are spread apart and two base plates are oriented and braced against one another in a locking position. In order to release the connection, pressure is applied to the piston counter to the spring force. 
     A gripper changing coupling is known from DE 37 13 619 A1. The locking mechanism comprises an adapter plate on which two centering pegs are provided. These are received in a centering bore and locked with a perpendicularly movable locking plate, the locking plate having two recesses, the wheels of which engage lockingly in undercuts on the centering pegs upon perpendicular movement. 
     SUMMARY OF THE INVENTION 
     The problem addressed by the present invention is that of providing a tool changer of the type mentioned at the outset in which the locking elements act against the receptacles in the locking position with a relatively high degree of force. The locking elements should be moved as quickly as possible at the same time. 
     This problem is solved by a tool changer having the features of claim  1 . In a tool changer of this kind, the rotary element is in particular movement-coupled to a rotationally fixed and axially movable actuation element such that, when the rotary element is rotated, the actuation element changes its position in the axial direction. The rotary element as such can also change its axial position; however, it is also conceivable for the rotary element and the actuation element to be movement-coupled to one another in such a way that the rotary element does not change its axial position when it is rotated. Furthermore, the actuation element is movement-coupled to or forms a pivot pin which extends perpendicularly to the longitudinal axis of the actuation element, a joint pin is provided on each of the locking elements, and, between the pivot pin and each joint pin, at least one lever arm is provided. Each lever arm is designed in such a way that, when the pivot pin is moved in the axial direction, the joint pins and thus also the locking elements are moved in a perpendicular direction running perpendicularly to the axial direction. A plurality of lever arms can also be provided between the pivot pin and each joint pin. Providing such an activation mechanism for the locking elements has the advantage that, by using the lever arms, the locking elements can cover relatively long distances with relatively little force as long as they are not in the locking position. Then, when the locking elements come into the region of the locking position, they cover relatively short distances while providing a relatively high degree of force. By providing the lever arms, the movement of the actuation element in the axial direction can also be advantageously deflected into a movement of the locking elements in the perpendicular direction. Overall, the movement of the pivot pin and the joint pin can also take place in relatively wear-free manner. 
     It is advantageous for the joint pin and the pivot pin to be circular-cylindrical and arranged so as to run parallel to one another. 
     In contrast to the known prior art as represented by DE 11 2009 002 163 T5, no rolling bodies which are exposed to high loads and high wear due to the relative movements of the components movement-coupled thereto are used. 
     Furthermore, it is also advantageous for the rotary element to comprise a head and a threaded rod, the head being rotatable by means of a rotary tool and the threaded rod being rotatably mounted in a threaded sleeve that is arranged on the base unit in a rotationally fixed manner. The threaded rod and the threaded sleeve can interact directly; the thread of the threaded rod then engages in a thread of the threaded sleeve. However, it is also conceivable for rolling bodies to be provided between the threaded rod and the threaded sleeve in order to minimize the friction between the threaded rod and the threaded sleeve. The rotary tool can be a hand-operated rotary tool or a machine-operated rotary tool. Providing a machine-operated rotary tool has the advantage that the rotary element can be operated in an automated manner. 
     The actuation element is advantageously provided on the rotary element on the side of the rotary element facing away from the head so as to be rotationally decoupled in the axial direction. The rotational decoupling can be implemented, for example, in such a way that the actuation element passes through and undercuts a coupling portion of the rotary element. 
     In a further advantageous embodiment, the head has an engagement surface for the rotary tool and a securing element which interacts with the engagement surface to secure the rotary element against rotation is provided on the base unit. The securing element is designed in such a way that it disengages from a securing position into a release position when the rotary tool is placed on the head or when the rotary tool is rotated. The securing element can, for example, be a securing wedge which is spring-loaded in the axial direction and which abuts a flat portion of the head and thereby prevents the rotary element from rotating. When the rotary tool is attached, this securing wedge can be moved backward in the axial direction from the securing position into the release position, as a result of which the rotary element can be rotated. 
     Furthermore, the two lever arms are preferably arranged one above the other and/or so as to adjoin one another, at least in portions. This results in a space-saving arrangement. 
     It is also advantageous for the locking elements to be designed as slide elements mounted in the base unit in a guided manner. The slide elements are in particular mounted so as to be guided in such a way that they can only move in the direction of rotation. In this way, a clear direction of movement of the slide elements can be specified. 
     The slide elements can in particular provide wedge portions on the side facing the respective receptacles. The receptacles can in particular be designed as complementary wedge receptacles. 
     It is also advantageous for the receptacles to be designed to be at least partially elastically yielding and/or to be arranged on the changing unit so as to be at least partially elastic. The receptacles can thus be deflected in an elastically yielding manner when the locking position is reached, as a result of which the locking elements act against the receptacles under a preload in the locking position. The advantage of providing such a preload is that it is possible to compensate for play resulting in particular from manufacturing tolerances. 
     It is advantageous if spring elements are provided which act on the receptacles against the changing unit in a spring-preloaded manner. In particular, spiral or disc springs can be used as spring elements. 
     It has also proven to be advantageous if, in the unlocking position, the connecting axes between the respective joint pins and the pivot pin form an angle α with the axial direction in the range of from 30° to 60°, and preferably in the range of from 40° to 50°, and/or if, in the locking position, the connecting axes between the respective joint pins and the pivot pin form an angle α with the axial direction in the range of from under 94° to over 90°. This ensures that a high degree of force transmission can be provided by the lever arms, particularly in the locking position; consequently, locking takes place with a relatively high degree of force overall. 
     It is also advantageous for a displaceable axial stop to be provided for adjusting the end position of the actuation element in the axial direction. When the end position is adjusted, the angle α can ultimately also be adjusted in the locking position. 
     According to a further embodiment of the invention, it is conceivable for positioning recesses or positioning rods by means of which the changing unit can be precisely positioned at a changing station to be provided on the changing unit. This makes it possible to ensure that the changing unit, in particular when it is detached from the base unit, can be mounted at a changing station. 
     The aforementioned problem is also solved by a changing system comprising a tool changer according to the invention, also comprising a changing station, wherein the changing station has a rotary tool for rotating the rotary element and wherein the changing station has positioning rods or positioning recesses by means of which the changing unit can be positioned at the changing station. A fully automated activation of the tool changer can therefore be achieved by such a changing system. 
     Further details and advantageous embodiments of the invention can be found in the following description, on the basis of which one embodiment of the invention will be described and explained in more detail. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  shows a changing system comprising a tool changer and comprising a changing station; 
         FIG. 2  shows the tool changer according to  FIG. 1 ; 
         FIG. 3  shows the changing system according to  FIG. 2  with the changing unit unlocked; 
         FIG. 4  is a section from the changing system according to  FIG. 1  when moving the tool changer to the changing station; 
         FIG. 5  is the view according to  FIG. 4  with the tool changer arranged at the changing station; 
         FIG. 6  is a longitudinal section through the changing system according to  FIG. 3 ; 
         FIG. 7  is a cross section through the changing system according to  FIG. 8 ; 
         FIG. 8  is a cross section corresponding to  FIG. 7  in the locking position; 
         FIG. 9  is a detail of a plan view of the base part without the housing; 
         FIG. 10  shows the locking elements of the base unit with the associated movement mechanism in the unlocking position; and 
         FIG. 11  is a view corresponding to  FIG. 10  in the locking position. 
     
    
    
     DETAILED DESCRIPTION 
     A tool changer  10  which comprises a base unit  12  and a changing unit  14  is shown in the drawings. A changing station  16  at which the tool changer  10  can be docked in order to release the changing unit  14  from the base unit  12  is also shown, in particular in  FIGS. 1 to 5 . The tool changer  10  and the changing station together form a changing system  18 . 
     The base unit  12  can be arranged on the free end of a robot arm. Using the robot arm, which is not shown in the drawings, the base unit  12  can be moved freely in space and, inter alia, can also be moved toward the changing station  16 . During operation, in particular a tool or a handling system, such as a gripping device, is arranged on the changing unit  14  in order to process or handle components. The changing unit  14  can be detached from the base unit  12  in order to exchange the tool or the handling unit. For this purpose, the tool changer  10 , i.e. the base unit  12  together with the changing unit  14 , is moved to the changing station  16 , as is shown in  FIG. 2 . In order to achieve positionally accurate docking of the tool changer  10  at the changing station  16 , three positioning rods  20  are provided on the changing station  16 , which rods can enter the positioning recesses  22  provided on the changing unit  14 , as indicated in  FIG. 6 . 
     As can be seen in  FIGS. 1 to 5 , a rotary element  24 , which is mounted so as to be rotatable about its longitudinal axis  25 , is provided on the base unit  12 .  FIGS. 4 and 5  show the housing of the base unit  12  with dashed lines only in order to make the components within the base unit  12  visible. 
     As can be seen in particular from the section according to  FIG. 6 , the rotary element  24  comprises a head  26  and a threaded rod  28 . The head  26  has engagement surfaces on two opposite sides in the form of flat portions  30  for a rotatably drivable rotary tool  32 . As can be seen from  FIGS. 1 to 5  in particular, the rotary tool  32  has a fork-like design and is arranged on the changing station  16  so as to be rotatably drivable. The rotary tool  32  has engagement surfaces  34  which are formed parallel to the flat portions  30 . When the tool changer  10  is docked at the changing station  16 , the engagement surfaces  34  of the rotary tool  32  consequently abut the flat portions  30  of the head  26 , as can be seen from  FIGS. 2 and 5 . 
     As can be seen in particular from  FIGS. 4 and 5 , a securing element  36  is also provided on the base unit  12 , which securing element interacts with one of the flat portions  30  to secure the rotary element  24  against rotation. The securing element  36  is preloaded by means of spring elements  38  in the axial direction, i.e. in the direction of the longitudinal axis  25  toward the changing station  16 . Rotation of the rotary element  24  is thus not possible when the tool changer  10  is not docked at the changing station  16 . If the tool changer  10  is located at the changing station  16 , as shown in  FIG. 5 , the rotary tool  32  interacts with the securing element  36  in such a way that, when the rotary tool  32  is rotated, it disengages from the securing position of the securing element  36  shown in  FIG. 4  into a release position shown in  FIG. 5 . In order to achieve safe disengagement against the preloading force of the spring elements  38 , each of the mutually facing sides of the securing element  36  and of the rotary tool  32  is wedge-shaped. 
     As can be seen in particular from the section according to  FIG. 6 , the threaded rod  28  of the rotary element  24  is rotatably mounted in a threaded sleeve  40 . In order to achieve the smoothest possible rotation of the rotary element  24  in the threaded sleeve  40 , rolling bodies are provided between the threaded rod  28  and the threaded sleeve  40 . However, it is also conceivable for the threaded rod  28  to act directly against the threaded sleeve  40 . By providing the threaded sleeve  40 , it becomes possible for the rotary element  24  to change its position in the axial direction, i.e. in the direction along the longitudinal axis  25 , when the rotary element  24  is rotated about its longitudinal axis  25 . The axial direction is indicated by the double arrow  41 . 
     As can also be seen from  FIGS. 4 to 8 , the rotary element  24  is movement-coupled in the axial direction  41  to a rotationally fixed and axially movable actuation element  42 . The actuation element  42  adjoins the rotary element  24  on the side of the rotary element facing away from the head  26  so as to be rotationally decoupled in the axial direction  41 . For rotational decoupling and simultaneous axial movement coupling, the rotary element  24  has, as can be seen from  FIG. 6 , an undercut  44  which engages behind an opening  46  of the actuation element  42 , which opening faces the rotary element  24 . This ensures that rotation of the rotary element  24  results in movement of the actuation element in the axial direction  41  without the actuation element  42  being rotated about the longitudinal axis  25 . 
     As can also be seen in particular from  FIG. 6 , the actuation element  42  has a bore  48  which extends perpendicularly to the longitudinal axis  25  and in which a pivot pin  50  is provided. The pivot pin  50  consequently extends perpendicularly to the longitudinal axis  25  or perpendicularly to the axial direction  41 . 
     As can also be seen from  FIG. 6 , the pivot pin  50  extends not only through the bore  48  of the actuation element  42 , but also through two further bores  52 , which are provided on respective lever arms  54 ,  56 . The two lever arms  54  and  56 , which can be seen in particular in  FIGS. 9 to 11 , each interact with respective joint pins  58 , which are in turn provided on respective locking elements  60 ,  62 . 
     Receptacles  80  for locking the changing unit  14  to the base unit  12  are shown on the changing unit in  FIGS. 3, 6, and 7 , which receptacles are designed as wedge grooves  84  provided in bridge portions  82 . The locking elements  60 ,  62  that interact with the receptacles  80  are provided on the base unit  12  and each have a wedge portion  86 , which is designed to be complementary to the wedge grooves  84 , at the free ends thereof. The locking elements  60 ,  62  having the wedge portions  86  can be seen in particular in  FIGS. 9 and 10 . 
     By moving the actuation element  42  in the axial direction, as illustrated in  FIG. 10 , the two locking elements  60 ,  62  can be moved from an unlocking position shown in  FIG. 10  into a locking position shown in  FIG. 11 . For this purpose, the locking elements  60 ,  62  move along a perpendicular axis  64  that runs perpendicularly to the longitudinal axis  25  in a perpendicular direction indicated by the arrows  68 . If, according to  FIG. 10 , the actuation element  42  is moved in the direction of the arrow  66  along the longitudinal axis  25  in the axial direction  41 , the locking elements  60 ,  62  are moved along the perpendicular axis  64  in the perpendicular direction  68  due to the mechanism of the lever arms  54 ,  56 . 
     In the unlocking position of the locking elements  60 ,  62  shown in  FIG. 10 , the connecting axes  70 , which run between the centers of the joint pins  58  and the center of the pivot pin  50 , each form an angle α of 45° with the longitudinal axis  25 . In the locking position shown in  FIG. 11 , the axes  70  form an angle β of approximately 88° with the longitudinal axis  25 . This means that, proceeding from  FIG. 10 , the locking elements  60 ,  62  are first moved relatively quickly in the direction of the arrows  68  with relatively little force. When the locking position, as shown in  FIG. 11 , is reached, the movement of the locking elements  60 ,  62  is slowed down due to the kinematics provided, but the locking force is increased accordingly. The angle β is selected as to be less than 90°. 
     In order to ensure that the angle β is less than 90°, an axial stop  72  that is displaceable in the axial direction  41  is shown in  FIG. 11 . The axial stop  72  is designed here as a threaded pin which can be screwed into the housing of the base unit  12 , as shown in  FIG. 9 . 
     In order to ensure that the locking elements  60 ,  62  move along the perpendicular axis  64  when the actuation element  42  is moved, guide pockets  74 , shown in  FIG. 9 , in which the locking elements  60 ,  62  are slidably arranged are provided in the housing of the changing unit  14 . 
     If, proceeding from  FIG. 11 , the actuation element  42  is moved back, i.e. to the right, by rotation of the rotary element  24  in the other direction, the locking elements  60 ,  62  move from the locking position shown in  FIG. 11  back into the unlocking position shown in  FIG. 10  along the perpendicular axis  64  counter to the directions of the arrows  68  in  FIG. 10 . 
     In order to ensure a sufficient preloading force in the locking position, the bridge portions  82  together with the receptacles  80  are arranged on the changing unit  14  in a partially elastically yielding manner. In particular, the bridge portions  82  can be provided on the changing unit  14  such that they can be deflected by means of spring elements. If, as shown in  FIG. 8 , the locking elements  60 ,  62  are acted on along the arrows  68  against the receptacles  80  in the locking position, said receptacles are deflected into the deflection position  82 ′ shown by dashed lines in  FIG. 8 . The advantage of this is that it is possible to reliably compensate for play that occurs, for example, due to tolerances. The deflection of the bridge portions  82  or the receptacles  80  is greater than the overall tolerance.