Title

TOOL FOR MAKING JOINTS OF CLINCH TYPE

Technical field

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

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

The present invention, which provides a solution to the said technical problems, is characterised according to the appended claims.

Brief description of the figures

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:

Figures 1A-D show in different views a first embodiment of the second tool part according to the invention without the movable die elements,

Figures 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,

Figures 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,

Figures 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,

Figures 5A-D show in different views the embodiment according to figures 1A-D additionally provided with air channels in the body of the tool part,

Figures 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,

Figures 7A-D show in different views a second embodiment of the second tool part according to the invention without the movable die elements,

Figures 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,

Figures 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,

Figures 10A-D show in different views the embodiment according to figures 7A- D additionally provided with air channels in the body of the tool part,

Figure 11A-D show in different views said spring element separately,

Figure 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,

Figure 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

Figures 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 figure 2A. Figure 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.

Figure 1 B 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..

Figure 1 C shows a section through the tool part 101 along the line A-A of figure 1 D. 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.

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.

Figures 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.

As can be seen in figure 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.

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.

Figures 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 figures 4 and 6. It should be noted that the joining procedure not necessarily open the die cavity as much as shown in figure 3 and could be finalized before the deformed material in the joint touches the support elements 103.

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.

Figures 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.

Figures 5A-D show in different views the embodiment according to figures 1A-D additionally provided with channels 112 for compressed air in the body of the tool part 101. Figures 5C and 5D show advantageous positions of the outlets 113 from the channels.

Figures 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.

Figures 7A-D show in different views a second embodiment of the second tool part according to the invention without the movable die elements. Figure 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.

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. figure 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.

Figure 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.

Figures 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.

As can be seen in figure 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.

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.

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 figure 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 figures 13 A-F, cf. below.

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.

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.

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.

Figures 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 figures 4 and 6. It should be noted that the joining procedure not necessarily open the die cavity as much as shown in figure 9 and could be finalized before the deformed material in the joint touches the support elements 203.

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.

Figures 10A-D show in different views the embodiment according to figures 7A- D additionally provided with channels 212 for compressed air in the body of the tool part 201. Figures 10C and 10D show advantageous positions of the outlets 213 from the channels.

Figure 11A-D show in different views said spring element separately. This element has been described in detail in relation to figures 4A-D.

Figure 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 figure 12B the heel element is co-operating with a corresponding recess 214 in the tool part body 201 '. The figures 12A-C show the die-anvil combination in its open position and the figures 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.

Figure 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 figures 13A-C show the die-anvil combination in its open position and the figures 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 figure 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.