Abstract:
Tool for joining two or several sheet formed members, comprising two separate tool parts, a first tool-part with a punch and a second tool-part provided with a die which co-operate for producing said joint, the punch is arranged to be driven in a linear movement is in the direction of the co-axial die provided with a die cavity at the bottom of which an anvil is arranged, the die is further provided with movable die elements ( 108, 208, 208′, 208″ ) arranged sliding laterally on a support surface ( 105 ) against the forces from a spring element ( 303, 303′ ), said die comprises at least two movable die elements ( 108, 208, 208′, 208″ ), the die is provided with at least one support element ( 103, 203, 203′, 203 ″) provided with an essentially horizontal support surface ( 110, 210 ) for said sheet formed members and said support elements ( 103, 203, 203′, 203″ ) are not forming part of the sidewall ( 109 ) of the die opening in its initial closed position.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a tool for making joints of the so called clinch type between two or several sheet formed members of metal or non-metal. 
       BACKGROUND ART 
       [0002]    This technique is well known in the art. A suitable tool comprises generally two separate tool parts which co-operate for producing said joint. A first tool part has the form of a punch which in a linear movement is driven in the direction of a co-axial second tool part in the form of a die with a die cavity at the bottom of which an anvil is arranged. 
         [0003]    For making the joint the sheet formed members are positioned against the second tool part, the die, provided with movable die elements arranged sliding laterally on a support surface against the forces from a spring element. The spring element is generally constituted by a ring made of an elastomer or a toroid formed metal spring surrounding the movable die elements. 
         [0004]    The approaching punch impacts on the surface of one of the members to be joined. The material of the two members is first drawn into the die cavity and subsequently due to the interaction between the punch and the anvil at the bottom of the cavity laterally extruded thereby displacing the movable die elements outwardly creating in the sheet formed members a mushroom formed button which interlocks the members. 
         [0005]    One of the problems with this type of it joint is to achieve sufficient strength against both shear forces and peeling forces. A number of tools exist which are more or less efficient when it comes to producing acceptable joints. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    The invention is related to a complete tool with a punch-die combination, a separate die and a special form of the spring element used in this type of tool. In the following the main part of the description will be attributed to the special characteristics of the die and the spring element. 
         [0007]    The punch could be of the conventional type on which the active free end has a cylindrical form, but other forms could be envisaged as well, e.g. slightly conical forms. 
         [0008]    One of the objects of the present invention is to provide a very robust and wear resistant tool. A tool according to the invention is possible to realise with very small dimensions especially in the embodiment with only two movable die elements which makes it suitable for use in narrow environments. 
         [0009]    A further object of the invention is to provide a die element on which the movable die elements are very precisely and efficiently guided in their reciprocating movent at the same time as they are efficiently locked against vertical movement. Vertical forces are applied on the die elements at the end of the procedure when the punch and the joint are retracted from the die cavity. 
         [0010]    A still further object of the invention is to provide a new type of spring element which has decisive advantages over spring elements known in the prior art. 
         [0011]    With the support surfaces close to the centre of the die unwanted deformations of the sheet formed members especially the one in contact with the support surfaces will be kept at a minimum. Additional extruded material will therefore instead go into the mushroom formed button which will increase the strength of the joint. This is especially true when the clamping device used with this kind of tool acting on the sheet formed members from the same side as the punch, having the form of a sleeve surrounding the punch, has been given a contact surface in a form corresponding to the top surface of the support elements. Additional increase of this effect will be reached by treating the top surface of the support elements to give higher friction against the sheet formed member in contact with the same. 
         [0012]    The present invention, which provides a solution to the said technical problems, is characterised according to the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0013]    Other objects and advantages of this invention will be apparent from the reading of this description which proceeds with reference to the accompanying drawings forming part thereof and wherein: 
           [0014]      FIGS. 1A-D  show in different views a first embodiment of the second tool part according to the invention without the movable die elements, 
           [0015]      FIGS. 2A-D  show in different views the first embodiment of the second tool part according to the invention including the movable die elements in the closed position, 
           [0016]      FIGS. 3A-D  show in different views the first embodiment of the second tool part according to the invention including the movable die elements in the open position, 
           [0017]      FIGS. 4A-D  show in different views the first embodiment of the second tool part according to the invention including the movable die elements in the closed position and additionally provided with a spring element according to the invention, 
           [0018]      FIGS. 5A-D  show in different views the embodiment according to  FIGS. 1A-D  additionally provided with air channels in the body of the tool part, 
           [0019]      FIGS. 6A-D  show in different views the first embodiment of the second tool part according to the invention including the movable die elements in the closed position and additionally provided with a spring element according to the invention and air channels in the body of the tool part, 
           [0020]      FIGS. 7A-D  show in different views a second embodiment of the second tool part according to the invention without the movable die elements, 
           [0021]      FIGS. 8A-D  show in different views the second embodiment of the second tool part according to the invention including the movable die elements in the closed position, 
           [0022]      FIGS. 9A-D  show in different views the second embodiment of the second tool part according to the invention including the movable die elements in the open position, 
           [0023]      FIGS. 10A-D  show in different views the embodiment according to  FIGS. 7A-D  additionally provided with air channels in the body of the tool part, 
           [0024]      FIG. 11A-D  show in different views said spring element separately, 
           [0025]      FIG. 12  A-F show an embodiment according to which the movable die elements have been provided with an end stop in the form of a heel formed element at the rear end of the of the movable die elements, 
           [0026]      FIG. 13  A-F show an embodiment according to which the movable die elements have been provided with an end stop in the form of an expanded rear portion of the element. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]      FIGS. 1A-D  show in different views a first embodiment of the second tool part according to the invention without the movable die elements  108 , cf. for instance  FIG. 2A .  FIG. 1A  shows the tool part in a perspective view. The tool part body  101  carries on its upper surface in this embodiment four support elements  103  arranged on one hand to support, by means of their upper surfaces  110 , the sheet formed members (not shown) to be joined together during the joining process, and on the other hand to support and guide the movable die elements  108  in their lateral movement. The four support elements  103  are in this embodiment arranged symmetrically around, and at a certain distance from, an anvil  102  having an upper generally flat surface  106 . The space between the support elements  103  has been given a form such that it in co-operation with the form of the movable die elements  108  will block the vertical movement of the elements  108 , i.e. in the direction parallel to the axis of the tool part  101 . The side walls  104  of the support elements  103  are generally flat and parallel to the same axis and are stabilising and guiding the movable elements in their lateral movement. The vertical blocking can be achieved by giving the elements  108  a somewhat larger section at their lower part which co-operates with a corresponding grove  107  at the lower part of the space between the support elements  103 . The horizontal generally flat surface  105  supports the sliding movement of the elements  108 . 
         [0028]      FIG. 1B  shows a side view of the same embodiment. The form of the grove  107  is here clearly visible. However, it should be noted that the arrangement for the vertical blocking could be realised in other ways, e.g. by means of a classical dovetailed grove. The grove could alternatively be arranged in the movable element  108  co-operating with a rim arranged on the sidewall  104 , etc. 
         [0029]      FIG. 1C  shows a section through the tool part  101  along the line A-A of  FIG. 1D . The anvil  102  is here represented as a separate part inserted in a dead-end hole at the centre of the tool part  101 . This arrangement makes it easy to change the anvil and adjust the depth of the die cavity depending on e.g. the thickness of the sheet formed members to be joined. 
         [0030]    Further below a second embodiment will be described in detail but it should be mentioned that the inventive idea could be realised on tool parts having at least two movable elements  108 . 
         [0031]      FIGS. 2A-D  show in different views the first embodiment of the second tool part according to the invention including the movable die elements  108  in the initial closed position. This is the position at the start of a joining procedure. The die elements  108  are kept in position by means of some spring element, an example of which will be described more in detail below. It should be noted, however, that traditional spring elements like elastomeric spring sleeves and toroid formed metal springs could be used. 
         [0032]    As can be seen in  FIG. 2A and 2D  the die cavity has a generally cylindrical form defined by the upper generally flat surface  106  on the anvil and the side walls  109  of the four die elements  108 . The sidewalls  109  are here illustrated as vertical but could in other embodiments have a somewhat conical form creating a die cavity with different diameters at the top and the bottom. 
         [0033]    As mentioned the sheet formed members (not shown) to be joined together are supported by the upper surfaces  110  on the support elements  103  during the joining process. The vertical forces on the tool part will, during the formation of the joint, be considerable. In order to facilitate the sliding lateral movement of the elements  108  which take place during the formation of the joint the vertical dimension of the elements  108  could advantageously be chosen so that the upper generally flat surface  111  of the elements  108  will be somewhat lower than the upper surface  110  on the support elements  103 . 
         [0034]      FIGS. 3A-D  show in different views the first embodiment of the second tool part according to the invention including the movable die elements  108  in the open position. The elements  108  are retained in place by means of the spring means e.g. of the type shown in the  FIGS. 4 and 6 . It should be noted that the joining procedure not necessarily open the die cavity as much as shown in  FIG. 3  and could be finalized before the deformed material in the joint touches the support elements  103 . 
         [0035]    Experiments have shown that an efficient clamping of the sheet formed members as close as possible to the centre of the joint will contribute to greater strength of the joint. Therefore, the form of the support elements according to the invention is very advantageous. In order to minimise the sliding of the material over the surface  110  this surface could be treated to give enhanced friction. 
         [0036]      FIGS. 4A-D  show in different views the first embodiment of the second tool part according to the invention including the movable die elements  108  in the closed position and additionally provided with a spring element  301  according to the invention. The element  301  has the general form of a cylindrical cage the surface of which has been provided with four slots having an acute angle, not necessarily constant, relative the axis of the cage to form four long elastic arms or blades  303  equally partitioned around the circumference with their free ends at the upper edge of the cage. The free end of each blade  303  is in this embodiment provided with a bent flange  304  arranged to bear against the movable element  108  to transfer the spring force to said element. It is understood that the bent flange  304  or another means for transferring the spring force is not always necessary. The inner diameter of the cage corresponds to the outer diameter of the tool part body  101  and the positioning of the cage is made by sliding the cage over the tool part body. The cage is made of some suitable resilient material such as spring steel and the material the form and length of the blades are chosen to give the appropriate spring force for the movable elements  108 . The spring element according to the invention is very compact, easy to change and has excellent properties. 
         [0037]      FIGS. 5A-D  show in different views the embodiment according to  FIGS. 1A-D  additionally provided with channels  112  for compressed air in the body of the tool part  101 .  FIGS. 5C and 5D  show advantageous positions of the outlets  113  from the channels. 
         [0038]      FIGS. 6A-D  show in different views the first embodiment of the second tool part according to the invention including the movable die elements  108  in the closed position and additionally provided with a spring element  303  according to the invention and air channels  112  in the body of the tool part  101 . The lower end portion  302  of the slots has been given a form to leave the openings of the air channels  112  free. 
         [0039]      FIGS. 7A-D  show in different views a second embodiment of the second tool part according to the invention without the movable die elements.  FIG. 7A  shows the tool part in a perspective view. The tool part body  201  carries on its upper surface in this embodiment four support elements  203  arranged on one hand to support, by means of their upper surfaces  210 , the sheet formed members (not shown) to be joined together during the joining process, and on the other hand to support and guide the movable die elements  208  in their lateral movement. 
         [0040]    The four support elements  203  are in this embodiment arranged symmetrically along the circumference of the tool part body  201  and are protruding from a generally flat surface which at the same time in its central part constitutes the anvil  202  and the surface  205  on which the movable elements are displaced. The space between the support elements  203  has in this embodiment too been given a form such that it in co-operation with the form of the movable die elements  208 , cf.  FIG. 8 , will block the vertical movement of the elements  208 , i.e. in the direction parallel to the axis of the tool part  201 . The vertical blocking is achieved by giving the elements  208  a somewhat larger section at their lower part which co-operates with a corresponding grove  207  at the lower part of the space between the support elements  203 . The horizontal generally flat surface  205  supports the sliding movement of the elements  208 . 
         [0041]      FIG. 7B  shows a side view of the same embodiment. Alternative arrangements for the vertical blocking could be realised in the same ways as for the first embodiment. 
         [0042]      FIGS. 8A-D  show in different views the second embodiment of the second tool part according to the invention including the movable die elements  208  in the initial closed position. This is the position at the start of a joining procedure. The die elements  208  are kept in position by means of some spring element, an example of which has been described above. It should be noted, however, that traditional spring elements like spring sleeves of for instance elastomeric material and toroid formed metal springs could be used. 
         [0043]    As can be seen in  FIG. 8A and 8D  the die cavity has a generally cylindrical form defined by the generally flat surface  202  on the anvil and the side walls  209  of the four die elements  208 . The sidewalls  209  are here illustrated as vertical but could in other embodiments have a somewhat conical form creating a die cavity with different diameters at the top and the bottom. 
         [0044]    As mentioned the sheet formed members (not shown) to be joined together are supported by the upper surfaces  210  on the support elements  203  during the joining process. The vertical forces on the tool part will, during the formation of the joint, be considerable. In order to facilitate the sliding lateral movement of the elements  208  which take place during the formation of the joint the vertical dimension of the elements  208  could advantageously be chosen so that the upper generally flat surface  211  of the elements  208  will be somewhat lower than the upper surface  210  on the support elements  203 . 
         [0045]    In order to make sure that the die cavity forms properly and centered in the starting position, i.e. the closed position as illustrated in  FIG. 8 , the displacement of the movable die elements  208  in the direction of the center of the tool part  201  could be limited by means of an end stop. Such an end stop could e.g. be implemented by an expanded rear portion of the element  208  in co-operation with a corresponding arrangement of the width of the guiding channel between the support elements  203 . An example of this type of end stop is illustrated in  FIGS. 13  A-F, cf. below. 
         [0046]    In the first embodiment described above the protruding anvil  102  also forms the end stop for the movable die elements  108  in the direction of the center of the tool part  101 . 
         [0047]    In some embodiments you would also wish to arrange an end stop for the movable die elements in their movement out from the centre of the respective tool part  101 ,  201  taking place during the lateral expansion of the compressed material. One way of achieving both types of end stops could be to arrange a pin or a screw (not shown) vertically through the movable die element reaching into a co-operating elongated groove (not shown) arranged in the sliding surface  105 ,  205 . 
         [0048]    In some embodiments the outward movement of the die elements  108 ,  208  will be stopped before the expanded material contacts the support elements  103 ,  203 . 
         [0049]      FIGS. 9A-D  show in different views the second embodiment of the second tool part according to the invention including the movable die elements  208  in the open position. The elements  208  are retained in place by means of the spring means e.g. of the type shown in the  FIGS. 4 and 6 . It should be noted that the joining procedure not necessarily open the die cavity as much as shown in  FIG. 9  and could be finalized before the deformed material in the joint touches the support elements  203 . 
         [0050]    Experiments have shown that an efficient clamping of the sheet formed members as close as possible to the centre of the joint will contribute to greater strength of the joint. Therefore, the form of the support elements according to the invention is very advantageous. In order to minimise the sliding of the material over the surface  210  this surface could be treated to give enhanced friction. 
         [0051]      FIGS. 10A-D  show in different views the embodiment according to  FIGS. 7A-D  additionally provided with channels  212  for compressed air in the body of the tool part  201 .  FIGS. 10C and 10D  show advantageous positions of the outlets  213  from the channels. 
         [0052]      FIG. 11A-D  show in different views said spring element separately. This element has been described in detail in relation to  FIGS. 4A-D . 
         [0053]      FIG. 12  A-F show an embodiment according to which the movable die elements  208 ′ have been provided with an end stop in the form of a vertical heel formed element  215  at the rear end of the elements. The heel element  215  could reach along the full width of the element  208 ′ or part of the width. As can be seen, especially in  FIG. 12B  the heel element is co-operating with a corresponding recess  214  in the tool part body  201 ′. The  FIGS. 12A-C  show the die-anvil combination in its open position and the  FIGS. 12D-F  in its closed position. It could also be noted that the spring element  301 ′ in this case has arms  303 ′ without a bent flange  304 . This is as described above an option. 
         [0054]      FIG. 13  A-F show an embodiment according to which the movable die elements  208 ″ have been provided with an end stop in the form of an laterally expanded rear portion  216  of the element. The  FIGS. 13A-C  show the die-anvil combination in its open position and the  FIGS. 13D-F  in its closed position. In this embodiment the side walls of the support elements  203 ″ have been arranged with a suitable recess co-operating with the enlarged rear portion of the movable elements. In principle it would be sufficient to arrange the expanded portion  216  only at one side of the movable element. In order to assure the best possible guiding of the elements  208 ″ double sided enlargements are however preferred. In  FIG. 13F  is illustrated how the support surfaces  210 ″ have been changed in relation to the surfaces  210 . The top surface  211 ″ of the elements  208 ″ has in this embodiment also a different form compared to the surface  211 .