Patent Publication Number: US-10307928-B2

Title: Device for punching an opening into a lightweight metal sheet and a method for performing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims foreign priority to German patent application serial no. DE 102014105056.8, filed Apr. 9, 2014, the entire contents of which is hereby incorporated by reference herein. 
     FIELD 
     This disclosure relates to a device for punching an opening into a lightweight metal sheet, a robot with such a device, a punch for such a device and a method for punching an opening into a lightweight metal sheet. 
     BACKGROUND 
     Lightweight metal sheets are known from the prior art and preferably comprise at least two metallic outer layers, between which at least one nonmetallic core layer is arranged. In spite of their low weight, such lightweight metal sheets have high local stiffness and are able to provide effective sound damping. Many applications require that these lightweight metal sheets can be connected to other sheet-metal parts or components. However, the joining methods that are often used for metal sheets, such as fusion welding or soldering, cause problems on account of their high heat input. The reason for this is that a thermoplastic material is preferably used as the plastic for the core layer, which has the effect that the core layer produced from this plastic melts during joining, or is damaged in some other way. 
     It is therefore advantageous for connecting a lightweight metal sheet to another component to provide a frictionally engaging and/or interlocking connection via an opening in the lightweight metal sheet by using a connecting element, such as a screw or a rivet. On account of the flow behaviour of the non-metallic core layer, preferably consisting of plastic, this cannot however ensure lasting strength of the connection. One cause for this can be seen in a decreasing holding force over time, on account of the flow behaviour. As a consequence, the connection between the lightweight metal sheet and the component, for example a metal sheet, loosens. 
     SUMMARY 
     An object of the present invention is to provide a device for punching an opening into a lightweight metal sheet, a robot with such a device, a punch for such a device and a method whereby an opening can be punched into a lightweight metal sheet effectively. In one aspect of the present disclosure, it is possible for a part of a core layer of the lightweight metal sheet in a peripheral region of the opening to be removed, and subsequently, the outer layers of the lightweight metal sheet may be brought into contact with each other in the peripheral region of the opening. It is also intended at the same time that different openings can be flexibly provided in a wide variety of lightweight metal sheets. 
     In one aspect of the present disclosure, a device for punching an opening into a lightweight metal sheet having at least two metallic outer layers and at least one non-metallic inner core layer disposed between the metallic outer layers, is disclosed. In one embodiment, such a device includes a quill having a heat source integrated therewith, a punch coupled to the quill and configured to be heated by said heat source, and a means for moving the punch in a first direction relative to the lightweight metal sheet. The quill, punch, and means for moving the punch form a punching device. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described in detail below with reference to the attached drawing figures, wherein: 
         FIG. 1  is a series of partial cross section views through a lightweight metal sheet depicting steps of an embodiment of a method of the present disclosure for punching an opening into the lightweight metal sheet; 
         FIG. 2  is an isometric view of an embodiment of a quill and a range of punches for a device as disclosed herein for punching an opening into a lightweight metal sheet; 
         FIG. 3  is an isometric view of an embodiment of a device of the present disclosure for punching an opening into a lightweight metal sheet; 
         FIG. 4  is an isometric view of an embodiment of a device of the present disclosure for punching an opening into a lightweight metal sheet. 
     
    
    
     DETAILED DESCRIPTION 
     Disclosed herein is a device for punching an opening into a lightweight metal sheet, a robot with such a device, a punch for such a device, and a method for punching an opening into a lightweight metal sheet that has at least two metallic outer layers and at least one non-metallic core layer disposed between the metallic outer layers. The punching device is configured to move a punch with respect to the lightweight metal sheet and includes a quill with an integrated heat source, wherein the punch may be heated up by the heat source. 
     A device as presently disclosed herein has the advantage of a heat source that can indirectly or directly control the thermal state of the punch, which according to a preferred embodiment is exchangeable, and which for this purpose is integrated in the quill. The thermal energy taken up by the punch is essential here for removing and/or deforming the non-metallic core layer in a peripheral region of the punched opening. By removing or deforming the non-metallic core layer and establishing electrical contact, it is possible to provide an opening in the lightweight metal sheet that is particularly well-suited for a durable connection between the lightweight metal sheet and another component by a connecting element, such as for example a screw or rivet. The thermal energy is in this case preferably adapted to the melting temperature of the non-metallic core layer. Furthermore, the punches mounted on the quill can be exchanged, which makes the device particularly flexible for punching a wide variety of openings into different lightweight metal sheets. For this purpose, a range of punches is provided, from which the desired punch can be chosen. 
     The non-metallic core layer preferably comprises a thermoplastic material, to which the capacity of the heat source is adapted. It is also conceivable that the heat source is designed in such a way that a heat output emanating from it is controllable. For this purpose, the heat source comprises for example a heating pin, the heat output of which can be controlled by way of an electric current. As a result, the heat output can be set such that the required thermal energy is transferred to the punch. With a controllable heat source, it could also be ensured that the punch changes its temperature during and/or after the punching of the opening, in order then to have in certain intervals the thermal energy required for removing and/or deforming the non-metallic core layer. In particular, it is provided that the punch is mounted on the quill in such a way that thermal energy can be transferred directly or indirectly from the heat source to the punch. It is also conceivable that the lightweight metal sheet already has an opening, and the device is used for at least partially removing and/or deforming the non-metallic core layer in the peripheral region of the opening and subsequently bringing the outer layers into contact. It is also provided that the relative movement takes place along a direction running parallel to the axis of the quill. 
     In a further embodiment it is provided that the heat source is at least partially arranged within the quill. In particular, the quill comprises a hollow body serving as a receptacle, in which the heat source is received. As a consequence of this, the heat source can be placed as close as possible to the punch, whereby the thermal energy emanating from the heat source has to cover a smaller distance. It is consequently possible for the thermal energy in the punch to be kept under control quickly and as far as possible without any losses by way of the heat source. 
     In a further embodiment it is provided that the quill has auxiliary means for arresting the punch on the quill. In particular, the auxiliary means are designed in such a way that they allow secure fixing of the punch to the quill with complementary auxiliary means on the punch. For example, a system made up of auxiliary means and complementary auxiliary means comprises interlocking and/or frictionally engaging means, which fix the punch releasably to the quill. In particular, the auxiliary means and the complementary auxiliary means snap and/or engage in one another when the punch is pulled onto the quill. It is also conceivable that the system made up of auxiliary means and complementary auxiliary means is designed in such a way that it contributes to aligning or orienting the punch. In particular, the quill only has the auxiliary means in one region along its circumference. In order to fix the punch successfully on the quill, the punch must then be aligned in such a way that the complementary auxiliary means can enter into an effective connection after the pulling on of the punch. 
     In a further embodiment it is provided that the quill has a conical or frustoconical neck for an interlocking connection between the quill and the punch. In particular, a conical or frustoconical neck is arranged at one end of the quill. The end of the quill then forms a receiving region for the punch, by way of which the punch is pulled on in an easy and uncomplicated way. The neck thereby preferably engages in the punch. The design as a conical or frustoconical neck even allows the punch to be offset a little in relation to the axis of the quill when it is being pulled on, to then be centred or aligned as it is being pulled on. As a result, the pulling on is advantageously made easier. 
     In a further embodiment it is provided that the punch has a punching region and a stamping region, the stamping region at least partially surrounding the punching region in a peripheral manner. It is provided in this respect that the punching region punches the opening into the lightweight metal sheet and the stamping region is responsible for bringing the respective outer layers into contact with each other. It is also conceivable that different thermal energies are provided for the stamping region and the punching region. It can correspondingly be envisaged that the stamping region and the punching region are made from different materials with different thermal conductivities, which allow the punching region and the stamping region to be at different temperatures. 
     In a further embodiment it is provided that the stamping region is offset from the punching region. An offset makes it possible to provide a punch which, in its relative movement with respect to the lightweight metal sheet, first punches the opening by the punching region and subsequently, as the relative movement continues, brings the outer layers into contact by the stamping region. 
     In a further embodiment it is provided that the device has a flat matrix for supporting the lightweight metal sheet, the flat matrix being arranged opposite the quill in the direction of the relative movement. In particular, the flat matrix acts as an abutment for the lightweight metal sheet when the opening is being punched. Use of the flat matrix as an abutment advantageously means that a punch imprint is only visible on one side. 
     In a further embodiment it is provided that the flat matrix has a suction-extraction opening for extracting a part of the core layer that is displaced during the punching. It is preferably provided in this respect that the suction-extraction opening is arranged in the device opposite the quill with the mounted punch. The suction-extraction opening is used in particular for extracting the displaced part of the core layer in the case of pre-punched lightweight metal sheets. The suction extraction means that the displaced part is advantageously removed cleanly, whereby unwanted soiling of the lightweight metal sheet with the displaced part of the core layer is prevented. 
     In a further embodiment it is provided that the device has a gripper, on the first gripper jaw of which the quill is arranged and on the second gripper jaw of which the flat matrix for mounting the lightweight metal sheet is arranged. The gripper has in particular a gripper opening for receiving the lightweight metal sheet between the two gripper jaws. It can be envisaged in this respect that the gripper is designed in such a way that its gripper opening changes, and can consequently be adapted to a thickness of the lightweight metal sheet. It is also provided that the relative movement for the punching of the opening is brought about by the moving together of the gripper jaws. For this purpose, the flat matrix and the quill are arranged opposite one another in the gripper. 
     In a further embodiment it is provided that the first gripper jaw is manually or automatically movable in relation to the second gripper jaw by way of a lever means. A manually operated device is particularly advantageously suitable for mobile use. In the case of an automatically operated lever means, the device is preferably attached to a robot, in particular to a robot arm. The moving together of the gripper jaws is preferably kept under control in a motor-controlled manner by way of a drive. As a result, a movement that can be particularly kept under control can be obtained during the punching of the opening. 
     In a further embodiment it is provided that the quill can be exchangeably mounted on the first gripper jaw by way of a sleeve. By exchanging the quill, the range of the possible gripper opening can be changed, if for example a different quill of a different length is inserted into the device. Furthermore, the quill can be easily taken out of the device and exchanged in the event of defects or other complications. 
     In a further embodiment it is provided that the device is arranged on a robot, by which the device can be transferred to a changing table for a punch change, it being possible that the quill with the punch can be moved on the changing table up to a stop in such a way that the punch is released from the quill. It is also provided that the device, controlled by the robot, can be moved to another punch and pulls this punch onto the quill by an axial compressive force. With the aid of the auxiliary means, the punch can then also be fixed in such a way that the device can be used for punching the opening. In such an embodiment, the punch can be advantageously changed fully automatically, which makes it particularly suitable for production lines on which lightweight metal sheets are used. 
     A further subject of the present invention is a robot with a device such as that described above. Such a robot may be integrated in a production line on which lightweight metal sheets are processed. The uncomplicated fully automatic changing of the punches allows the robot to be used for punching a wide variety of openings into different lightweight metal sheets. 
     A further subject of the present invention is a punch for a device such as that described above. In particular, the punch is adapted to the device and can only be pulled on when the punch and the device have been made to match one another on the basis of a lock-and-key principle. It is also conceivable that the punch is part of a range of punches. The punches of the range of punches preferably differ in the geometry of the punches, the number of openings that can be made with the punch, and/or the design of the punching region and the stamping region. 
     A further subject of the present disclosure is a method for punching an opening into a lightweight metal sheet by a device as disclosed herein. Using the device described above advantageously allows the making of openings that allow a durable, i.e. long-term, connection between the lightweight metal sheet and another component. 
     In an embodiment of the method it is provided that in a first method step the opening is punched by the relative movement of the punch with respect to the lightweight metal sheet, in a second method step the non-metallic core layer being at least partially displaced by the thermal energy taken up from the heat source and in a third method step the metallic outer layers being brought into contact in a region adjacent to the opening. It is also provided that the punch is changed at a time before the first method step and/or at a time after the third method step, preferably fully automatically. For this purpose, the device is preferably moved onto a changing table with a stop. The punch is pushed out with the aid of the stop. It is also provided that, for the punch change, the device is moved in such a way that an interlocking engagement with the quill is brought about for another punch, by a compressive force acting axially on it, with the effect that the punch is firmly connected to the quill without any further effort. 
     Further details, features and advantages of the invention emerge from the drawings, and also from the following description of various embodiments with reference to the attached drawing figures. The drawings thereby merely illustrate exemplary embodiments of the invention that do not restrict the scope of the concept of the invention. 
     In the various drawing figures, the same parts are always provided with the same designations, and are therefore in each case also generally only referred to or mentioned once. 
     Referring to  FIG. 1 , a method for punching an opening  8  into a lightweight metal sheet  2  as provided by the present invention is disclosed. Lightweight metal sheets  2  preferably comprise at least two metallic outer layers  31 , between which at least one non-metallic core layer  32  is disposed. In spite of their low weight, such lightweight metal sheets  2  have high local stiffness and are able to provide effective sound damping. Many applications require that these lightweight metal sheets  2  can be connected to other sheet-metal parts or components. However, the joining methods that are often used for metal sheets, such as fusion welding or soldering, often cause problems on account of their high heat input. The reason for this is that a thermoplastic material is preferably used as the plastic for the core layer, which has the effect that the core layer  32  produced from this plastic melts during joining, or is damaged in some other way. It is therefore advantageous for connecting a lightweight metal sheet  2  to another component to provide a frictionally engaging and/or interlocking connection via an opening  8  in the lightweight metal sheet  2  by using a connecting element, such as a screw or a rivet. On account of the flow behaviour of the non-metallic core layer  32 , preferably consisting of plastic, this cannot however ensure lasting strength of the connection. One cause for this can be seen in a decreasing holding force over time, on account of the flow behaviour. As a consequence, the connection between the lightweight metal sheet  2  and the component, for example a metal sheet, loosens. 
     In order to counter this problem, preferably in a peripheral region around the opening  8  that is intended for the frictionally engaging and/or interlocking connection, the non-metallic core layer  32  between at least two metallic outer layers  31  is removed and contact between these outer layers  31  is established. With such contact, a durable frictionally engaging and/or interlocking connection can be provided.  FIG. 1  shows a method in which an opening  8  is punched into a lightweight metal sheet  2  by a punch  5  with a punching region  5 ′ and a stamping region  5 ″ being moved in relation to the lightweight metal sheet  2 . The relative movement has the effect that first a part  33  is first pushed out from the lightweight metal sheet  2  with the aid of the punching region  5 ′, in order to form the opening. It is also provided that the punch  5  has so much surplus thermal energy that the peripheral region of the opening created is heated up and deformed during and/or after the punching of the lightweight metal sheet  2  in such a way that the non-metallic core layer  32  is at least partially displaced along the circumference of the opening. In particular, the relative movement of the punch  5  is continued in such a way that the stamping region  5 ″ of the punch  5  ensures that the outer layers  31  are brought into contact with one another. 
     Referring to  FIG. 2 , a quill  1  with a range of punches  5   a - 5   h  for a device  100  for punching an opening  8  according to a first exemplary embodiment of the present disclosure is shown. It is in this case provided that the quill  1  is designed in such a way that it can receive or integrate a heat source  3 . In particular, it is provided that the quill  1  has a hollow space in which the heat source  3  is at least partially arranged. For example, the quill  1  encloses the heat source  3 . It is conceivable in this respect that the heat source  3  is a heating pin, the thermal capacity of which is electrically controllable and is adapted to the temperature that is optimal for the respective punching process. It is also provided that the punch  5 , which is intended for forming the opening  8  and removing or deforming a part of the non-metallic core layer  31 , can be exchangeably mounted on the quill  1 . In the representation of  FIG. 2 , the punch  5  is illustrated as detached from the quill  1 . It is provided in particular in this respect that there is the possibility of selecting the desired punch  5  from the range of punches  5   a - 5   h  and attaching it to the quill  1 . For example, it is possible to choose between punches  5  that make different openings  8  or in each case make a multiplicity of openings  8 . It is also conceivable that it is possible to choose between punches  5  of different sizes, in order to adapt the punch  5  to the thickness of the lightweight metal sheet  2 . Furthermore, the punch  5  may be formed in such a way that different openings  8  can be made in the lightweight metal sheet  2  in a desired or intended arrangement. 
     For the mounting of the punch  5  on the quill  1 , the latter has at its one end a conical neck for an interlocking connection with the punch  5 . The conical shape advantageously helps when the punch  5  is being pulled onto the quill  1 . It is also provided that the quill  1  has an auxiliary means  10  for arresting the punch  5 . The auxiliary means  10  may thereby help to fix the punch  5  appropriately for its use. Furthermore, the auxiliary means  10  may align the punch  5  in an orientation that is preferred for the punching, if for example the punch  5  is asymmetrical in its basic shape. In particular, it can be envisaged that the punch  5  engages or snaps into the auxiliary means while it is being pulled onto the quill  1 . The punch preferably comprises an auxiliary means that is complementary to the auxiliary means  10  and with which the auxiliary means  10  fixes the punch on the quill. It is also conceivable that the auxiliary means  10  and/or the complementary auxiliary means have a spring element. 
     Irrespective of in what way the punch  5  is mounted or fixed on the quill  1 , it is provided in particular that the mounted punch  5  indirectly or directly takes up the heat emanating from the heat source  3 , in order to itself be able to provide the thermal energy necessary for the removal or deforming of a part of the non-metallic core layer  32 , and transfer it to the lightweight metal sheet  2 . In this respect, the punch  5  may be designed in such a way that the stamping region  5 ″ and the punching region  5 ′ of the punch  5  can take up or store different amounts of thermal energy. For example, the punch  5  is of a multicomponent type of construction, the individual material components having different thermal conductivities, which ensure that the stamping region  5 ″ and the punching region  5 ′ assume different temperatures or take up different amounts of thermal energy from the heat source  3 . As a result, the punching can be flexibly adapted to the opening  8  to be respectively made in the lightweight metal sheet  2 . 
     Referring to  FIG. 3 , a device  100  for punching an opening  8  according to a first exemplary embodiment of the present disclosure is schematically represented. It is in this case provided that this device  100  is operated manually by way of a lever arm  15 . Such a device is intended in particular for mobile use. For this purpose, the device  100 , formed in the manner of a gripper, comprises a joint system  17 , with the aid of which a first gripper jaw  12  and a second gripper jaw  11  can be moved together by actuating the lever arm  15 . In particular, the quill  1  with the mounted punch  5  is arranged on the first gripper jaw  12  and a flat matrix  4  for supporting the lightweight metal sheet  2 , preferably with a core layer  32  of a thermoplastic material, is arranged on the second gripper jaw  11 . In this case, the quill  1  is preferably fastened to a sleeve, and is consequently exchangeable at any time. Arranged within the quill is the heat source  3 , which transfers thermal energy to a punch geometry. The moving together of the gripper jaws, i.e. the closing of a gripper opening  20  formed by the gripper jaws, then brings about that relative movement A of the heated-up punch  5  with respect to the lightweight metal sheet  2  placed on the flat matrix  4  that finally leads to the punching of the opening  8 , the partial removal of the core layer  32 , and the contact between the outer layers  31 . These method steps preferably take place in a flowing relative movement A of the two gripper jaws  11 ,  12  in relation to one another. However, it is also conceivable that the individual method steps take place at individual time intervals, in which the heat of the punch  5  is in each case adapted to the respective method step. For this purpose, a heating capacity of the heat source  3  is appropriately changed, by for example the heat source being exchanged or the current applied to a heating pin being varied. 
     The flat matrix  4  also serves as a planar abutment, which ensures that a punch imprint is only visible on one side after the punching on the lightweight metal sheet  2 . It is also provided that the device  100  has an adjusting screw  18 , by way of which the gripper opening  20  can be set. As a result, the gripper opening  20  can be advantageously adapted to the thickness of the lightweight metal sheet  2 , which allows the device  100  to be flexibly used. 
     Referring to  FIG. 4 , a device  100  for punching an opening  8  according to a second exemplary embodiment of the present disclosure is schematically represented. It is in this case provided that this device  100  is operated in an automated manner, for example by way of a robot. Correspondingly, the device  100  represented differs from that from  FIG. 3  in that the lever arm  15  with its joint system  17  is replaced here by an automatic, preferably motor-operated, drive  21  for the moving together of the gripper jaws. In particular, it is provided that a punch change can be made with the aid of the robot or robot arm on which the device is mounted. In this case, the device  100 —controlled by way of the robot or the robot arm—can be moved to a changing table  40 . For a changing mechanism, it is then provided that the first gripper jaw  12  with the quill  1  is moved against a stop  41  of the changing table  40  in such a way that the punch  5  is pushed out by the movement initiated by the robot. Thanks to the conical neck for the quill-punch connection, an easy and complete punch change is then possible when the device  100  is moved to another region of the changing table  40  or to another changing table for receiving another punch  6 . For this purpose, the quill  1  is first placed in front of the other punch  6  and subsequently moved in such a way that an interlocking engagement with the quill  1  is produced by way of an axially acting compressive force on the other punch  6 . Then the auxiliary means  10  for arresting is used to fix the punch  5  firmly in such a way that it can be used for punching openings  8  into a lightweight metal sheet  2 . For this purpose, the device  100  is moved, preferably fully automatically by the robot, until the gripper opening  20  has received a lightweight metal sheet  2  between the gripper jaws. After that, the punching process can then take place. 
     It is preferably provided that the flat matrix  4  has a suction-extraction opening  43 , which allows the extraction of the detached core layer, preferably in the case of pre-punched lightweight metal sheets. For this, it is preferably provided that the suction-extraction opening  43  is arranged in a region of the flat matrix  4  that is opposite the quill  1 .