Abstract:
This application is directed to groove milling devices for milling a groove in a component. In one example, a groove milling device includes a milling disk which is rotatable about a rotational axis, wherein the groove milling device comprises a displacement device for moving the milling disk along the rotational axis during the milling process. In an example, the groove milling device may include a control device which actuates the displacement device automatically when a predetermined depth of the milled groove is reached during the milling process. In an example, the groove milling device may include a switch for activating the displacement device by an operator during the milling process. In an example, the energy required for actuating the displacement device may be generated by a generator coupled to a main drive spindle of the groove milling device.

Description:
RELATED APPLICATION 
     This patent is a divisional of U.S. patent application Ser. No. 12/611,748, filed Nov. 3, 2009, which is a continuation of PCT/EP2008/003575 filed May 3, 2008, which claims priority to European Patent Application No. 07 009 267.1, filed on May 8, 2007, each of which are hereby incorporated herein by reference in their entireties. 
    
    
     FIELD OF THE DISCLOSURE 
     The present invention relates to a connecting means for connecting a first component and a second component, and in particular, for connecting furniture parts or machine parts, comprising 
     a first connecting element arranged on the first component in the connected state of the components and 
     a second connecting element arranged on the second component in the connected state of the components. 
     BACKGROUND 
     Such a connecting means is known from DE 196 04 243 C2 for example. 
     DE 196 04 243 C2 discloses a fitting for connecting components, said fitting consisting of two half-fittings which are each fixed to a respective one of the components that are to be connected and comprise elements that are adapted to be brought into engagement with one another for establishing the connection between the components, wherein each of the half-fittings comprises a section in the form of a segment of a circle having self-cutting protruding edges so that each half-fitting is adapted to anchor itself in the relevant component by virtue of being driven into its respectively associated component along the self-cutting edges. In the case of hard materials such as a hardwood or metallic materials for example, the process of driving the half-fittings into the components along the self-cutting edges is extremely difficult or even completely impossible. In addition, there is a danger with the fitting in accordance with DE 196 04 243 C2 that the lateral walls of the respective component could break away when driving-in the half-fittings as a result of the forces arising due to the protruding self-cutting edges. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a connecting means of the type mentioned hereinabove which will enable two components consisting of a plurality of materials to be securely connected to one another without giving rise to the danger of damaging the two components during the assembly process. 
     In accordance with the invention, this object is achieved in the case of a connecting means comprising the features indicated in the first part of claim  1  in that at least one of the connecting elements comprises at least one non self-cutting holding projection which comprises a curved supporting surface that is in the form of an arc of a circle in longitudinal section, wherein the holding projection can be inserted into a groove which is provided in one of the components and has a curved undercut surface that is in the form of an arc of a circle in longitudinal section. 
     The concept underlying the solution in accordance with the invention is that the connecting element having the at least one holding projection is to be pushed into a groove which had already been produced in the component prior to the insertion of the connecting element and which has an undercut section in the relevant component in the longitudinal direction of the groove. Hereby, the holding projection can be pushed into the undercut section of the groove in the tangential direction using just a small amount of force so that the connecting element still has a certain degree of freedom of movement in this direction and thus corrections with respect to their mutual positioning are still possible when connecting the components. 
     Furthermore, with the aid of a curved supporting surface thereon, the holding projection can be supported on the likewise curved undercut surface of the undercut section of the groove in the associated component, whereby this undercut surface is likewise in the form of an arc of a circle in longitudinal section and has the same radius of curvature as the curved supporting surface of the holding projection. A positive connection between the component and the connecting element is produced as a result of the engagement between the holding projection and the undercut section of the groove. 
     Hereby, particularly effective anchoring of at least one of the connecting elements in the associated component is obtained without having to use a large amount of force when inserting the connecting element into the associated component which could lead to the component being damaged. 
     In contrast thereto, holding grooves for the half-fittings must first be reamed out by means of the self-cutting protruding edges by forcing the half-fittings into the components when inserting the half-fittings of the fitting known from DE 196 04 243 C2 into the components. For this purpose, it is necessary to exert quite a substantial amount of force. Furthermore, the self-cutting protruding edges must be geometrically optimised for the self-cutting action, and in particular, they need to be sufficiently thin in order to make it possible to force out the reamed-out material. Furthermore, when driving the half-fittings into the components, material can easily be chipped off the outer edges of the component, especially when the half-fittings are being driven-in at the edge of the component. In the case of solid materials such as a hardwood for example, the process of driving-in the half-fittings is extremely difficult; in the case of other materials such as plexiglass for example or in the case of metallic materials, the self-cutting process for driving-in the half-fittings fails completely. Furthermore, after being driven into the respective component, the half-fittings are stuck immovably therein and can no longer be shifted along the holding groove in order to enable corrections in the positioning thereof to be made and thus compensation for tolerances to be effected. 
     By contrast, the connecting means in accordance with the invention can be used for connecting components of any type of material such as especially hardwood, plexiglass or metallic materials and, due to the fact that at least one of the connecting elements is adapted to be displaced in the longitudinal direction of the groove in which the connecting element is accommodated, it is possible to make positional corrections and thus compensate for the positional tolerances of the grooves in the components and/or compensate for manufacturing tolerances of the connecting elements. 
     Furthermore, at least one of the connecting elements preferably comprises a curved bearing surface which is in the form of an arc of a circle in longitudinal section so that this bearing surface can slide on a groove base surface that is likewise in the form of an arc of a circle in longitudinal section of a groove that is provided in one of the components, whereby the alignment of the connecting element concerned relative to the other respective connecting element can be changed within certain limits in the course of connecting the connecting elements in order to compensate for the positional tolerances of the grooves in which the connecting elements are arranged, and/or manufacturing tolerances of the connecting elements. 
     Due to this additional degree of freedom of movement, further corrections with respect to their mutual positioning are possible when assembling the two components, this thereby significantly reducing the need for precision with regard to the location of the grooves in the components and thus leads to it being considerably easier for the user to use. 
     In particular, the holding projection may comprise stub-like ends and/or have rounded-off, bevelled edges at its end regions. 
     The cross-sectional area of a non self-cutting holding projection may be of any desired size in order to increase the mechanical stability of the holding projection. 
     In particular, the cross-sectional area of the holding projection can amount to at least 1 mm 2 . 
     The holding projection may have a substantially rectangular or a substantially trapezoidal cross section. 
     As an alternative or in addition thereto, provision may be made for at least one holding projection to taper with increasing spacing from a base body of the respective connecting element. 
     On the other hand, provision may be made for at least one holding projection to taper with decreasing spacing from a base body of the respective connecting element. 
     As an alternative or in addition thereto, it is also conceivable for the cross section of at least one holding projection to have an outer contour which is curved at least in sections thereof. 
     In a preferred embodiment of the invention, provision is made for the surface of at least one holding projection to be substantially flush with a curved bearing surface of a base body of the respective connecting element. Thus, in this case, the holding projection is arranged on the outermost edge of the associated connecting element facing the groove base. 
     As an alternative or in addition thereto, provision may also be made for at least one holding projection to be arranged such that it is offset with respect to the curved bearing surface of a base body of the respective connecting element. Thus, in particular, the holding projection may have a smaller radius of curvature than the curved bearing surface of the respective connecting element. 
     Furthermore, provision may be made for several holding projections having differing radii of curvature to be arranged on the same connecting element. 
     In particular, a plurality of holding projections having differing radii of curvature can be arranged on the same side of the respective connecting element. 
     In particular, the curved bearing surface of the base body of the respective connecting element may be in the form of an arc of a circle in longitudinal section. 
     In particular, the curved bearing surface of at least one connecting element can be substantially in the form of a section of the surface of a regular cylinder. 
     In a preferred embodiment of the invention, provision is made for the first connecting element and the second connecting element to be connected to one another in releasable manner in the connected state of the components and for at least the first connecting element to comprise at least one holding element which is moveable relative to a housing of the first connecting element and which, in a holding position, cooperates with the second connecting element in such a way that a relative movement of the first connecting element and the second connecting element along the direction of connection is prevented, and which, in a release position, permits a relative movement of the first connecting element and the second connecting element along the direction of connection, 
     whereby at least one holding element is movable from the holding position into the release position and/or from the release position into the holding position by means of an action occurring outside the connecting means. 
     In this embodiment, the connection of the two connecting elements is not established by a relative displacement of the two connecting elements as a whole but rather, by means of a relative movement of the holding element relative to a housing of the first connecting element from the release position into the holding position. As an alternative or in addition thereto, the connection between the connecting elements can be released by a movement of the holding element relative to the housing of the first connecting element from the holding position into the release position. 
     When the connecting elements are locked together by the movement of the holding element into the holding position, then, due to the tensile forces which are act on the connecting elements in a direction of connection that is oriented transversely and preferably perpendicularly to the bearing surfaces of the connecting elements, so much friction will be activated that the ability to displace the holding projection within the undercut section of the groove is annulled and an extremely firm connection between the components that are to be connected is established. 
     The connecting elements of the connecting means in accordance with the invention are placed into pre-existing grooves in the components so that a large amount of force is not necessary to insert the connecting elements into the components and consequently there is no danger of damage to these components. 
     When the holding element of the connecting means in accordance with the invention has been moved from the holding position into the release position, the connecting elements can be moved away from each other in a direction of connection that is oriented perpendicularly to the bearing surfaces of the connecting elements with which the connecting elements abut one another in the connected state of the components, without the connecting elements having to be previously moved relative to each other in a direction parallel to the bearing surfaces. 
     In a preferred embodiment of the invention, provision is made for the housing of the first connecting element to have a curved bearing surface that is in the form of an arc of a circle in longitudinal section, and a substantially flat bearing surface which is located opposite the aforesaid bearing surface and is adapted to be placed on the second connecting element. 
     In particular, provision may be made for the substantially flat bearing surface of the first connecting element to be able to abut a likewise substantially flat bearing surface of the second connecting element. 
     The substantially flat bearing surface of the first connecting element and/or the second connecting element is preferably oriented substantially parallel to contact areas of the components with which the components abut one another in the connected state of the components. 
     Furthermore, the curved bearing surface and the substantially flat bearing surface of the first connecting element and/or the second connecting element are oriented substantially perpendicularly to the direction of the connection in the connected state of the components. 
     In a preferred embodiment of the invention, provision is made for at least one holding element to be held such as to be pivotal on the first connecting element. 
     In order to effect the connection of the two connecting elements in the holding position of the holding element, provision may be made for at least one holding element to have a first holding contour which engages behind a second holding contour provided on the second connecting element in the holding position. 
     The first holding contour and/or the second holding contour can be formed such as to be arc-shaped. 
     In particular, provision may be made for the first holding contour and the second holding contour to be formed such that they are not mutually concentric so that the two connecting elements are pulled against each other when moving the holding element from the release position into the holding position. 
     Until now, no detailed indications have been given as to the manner in which the holding element is movable from the holding position into the release position or in the reverse direction by means of an action occurring outside the connecting means. 
     For example, provision may be made for at least one holding element to be movable from the holding position into the release position and/or from the release position into the holding position by means of a mechanical actuating means that can be moved into engagement with the holding element from outside the connecting element. 
     For this purpose, it is expedient if at least one holding element comprises a seating for an actuating section of a mechanical actuating means. 
     In particular, provision may be made for at least one holding element to comprise a seating for a polygonal key, an Allen key and/or a screwdriver. 
     In order to enable the mechanical actuating means to act on the holding element, provision may be made for the first connecting element to comprise a housing having a passage opening for the passage of a mechanical actuating means to a holding element. 
     In particular, provision may be made for the housing to comprise a side wall which extends transversely to the curved bearing surface of the first connecting element and for the passage opening to be arranged in the side wall. 
     As an alternative thereto, provision may also be made for the passage opening to be arranged in the curved bearing surface of the first connecting element. 
     In a special embodiment of the invention, provision may be made for at least the first connecting element to comprise at least two holding elements which are held such as to be pivotal on the first connecting element. 
     In order to ensure the connection of the two connecting elements in the holding position of the holding elements, provision may be made for at least two holding elements to each engage behind a respective restraining element which is arranged on the second connecting element in the holding position. 
     In order to enable the holding elements to be pivoted from the release position into the holding position, provision may be made, in particular, for a support region of a first holding element and a support region of a second holding element to be movable relative to each other by means of a spreading mechanism. 
     Such a spreading mechanism could comprise a magnet element which is adapted to be driven such that it moves within the connecting means by means of a time varying magnetic drive field which acts on the magnet element from outside the connecting means. 
     In a preferred embodiment of the invention, provision is made for the spreading mechanism to comprise at least two spreading elements which are in engagement with one another. 
     In particular, the spreading elements may be held in engagement with one another by means of two mutually complementary threads. 
     It is particularly expedient, if at least one of the spreading elements is adapted to be driven into rotational movement relative to the other spreading element by means of the magnet element. 
     In particular, the magnet element may comprise a driver element which acts on a driven element on one of the spreading elements. 
     Furthermore, provision may be made in a special embodiment of the invention for at least one holding element to have a thread. 
     Provision may be made for at least one holding element to be in engagement with a restraining element in the holding position, wherein said restraining element is arranged on the second connecting element and the restraining element has a thread that is complementary to the thread of the holding element. 
     In order to facilitate the process of bringing the holding element into engagement with the restraining element, provision may be made for the connecting means to comprises at least one resilient element, and in particular a spring, by means of which the holding element and the restraining element are biased against each other. 
     Furthermore, a thread axis of the holding element can be oriented substantially parallel to the direction of the connection in the connected state of the components. 
     In a special embodiment of the invention, provision may be made for the connecting means to comprise a magnet element which can be driven into a rotational movement within the connecting means by means of a time varying magnetic drive field that acts on the magnet element from outside the connecting means. 
     In particular, by means of such a magnet element, at least one holding element can be adapted to be driven into a rotational movement relative to the housing of the first connecting element. 
     Hereby, the magnet element may comprise a driver element which acts on a driven element on the holding element. 
     In order to enable shearing stresses to be removed as well by means of the connection between the connecting elements, it is of advantage if at least one of the connecting elements comprises at least one insertible projection and if the other respective connecting element comprises at least one seating pocket for accommodating the insertible projection in the connected state of the components. Thereby, additional dowel pins such as are necessary with most other connecting means can be dispensed with. 
     If at least one seating pocket extends to a greater extent in the longitudinal direction of the connecting means than the insertible projection accommodated therein, then this offers the advantage that the first connecting element and the second connecting element are mutually displaceable in the longitudinal direction in order to enable tolerances in the connection between the components to be compensated for in this manner. 
     As an alternative to a connection between the two connecting elements by means of a moveable holding element, provision may also be made for the first connecting element and the second connecting element to be connected to one another in the connected state of the components by an integral bond. 
     In particular, provision may be made for the first connecting element and the second connecting element to be glued to one another in the connected state of the components. 
     Furthermore, the present invention relates to a method of producing a connection between a first component and a second component, in particular, a connection between furniture parts or machine parts. 
     The object of the present invention is to provide a method which is such as to enable two components consisting of a multiplicity of materials to be securely connected together without giving rise to the danger of damage to one of the components. 
     This object is achieved by a method which comprises the following method steps:
         producing a respective groove in a contact area of the first component and in a contact area of the second component, wherein at least one of the grooves comprises at least one undercut section having a curved undercut surface which is in the form of an arc of a circle in longitudinal section;   inserting a first connecting element into the groove in the first component and a second connecting element into the groove in the second component, wherein at least one of the connecting elements comprises at least one holding projection which has a curved supporting surface that is in the form of an arc of a circle in longitudinal section;   connecting the first connecting element and the second connecting element.       

     Special embodiments of the method in accordance with the invention form the subject matter of claims  41  to  60 , the advantages thereof having already been explained hereinabove in connection with the special embodiments of the connecting means in accordance with the invention. 
     Furthermore, the present invention relates to a groove milling device for milling a groove in a component, wherein said device comprises a milling disk which is rotatable about a rotational axis and is used, in particular, for carrying out the method in accordance with any of the claims  40  to  60 . 
     The object of the present invention is to provide such a groove milling device with the aid of which a groove can be produced in a simple and precise manner and wherein said groove comprises at least one undercut section having a curved undercut surface. 
     In accordance with the invention, this object is achieved in the case of a groove milling device incorporating the features of the first part of claim  61  in that the groove milling device comprises a displacement device for moving the milling disk along the rotational axle during the milling process. 
     By means of such a groove milling device, a base section of the groove can first be milled and then, when the base section has reached a given depth, the milling disk can be moved along the axis of rotation in order to mill at least one undercut section. 
     In particular, the groove milling device in accordance with the invention may comprise a stop means for limiting the depth of the milled groove. 
     Furthermore, the groove milling device may comprise a switch for actuating the displacement device by an operator during the milling process in order to enable the movement of the milling disk along the axis of rotation to be initiated manually. 
     As an alternative or in addition thereto, provision may also be made for the groove milling device to comprise a control device which automatically actuates the displacement device when the milled groove has reached a given depth during the milling process. In this way, the effect is achieved that the milling disk can be immediately moved along the axis of rotation for producing the undercut section as soon as the given groove depth has been reached; this can shorten the time needed for the entire milling process by a considerable amount. 
     In a preferred embodiment of the invention, provision is made for the milling disk to be caused to move along the rotational axis by means of the displacement device from a basic position into a first undercut position and afterwards, in the opposite direction, into a second undercut position beyond the basic position. In this way, a groove can be produced with two undercut sections which project from a base section of the groove in mutually opposite directions. 
     Preferably, the length of path over which the milling disk is movable along the rotational axis by means of the displacement device is adjustable to various values. 
     The energy required for the actuation of the displacement device can be generated by means of a generator which is coupled to a main drive spindle of the groove milling device for example. 
     In particular hereby, the generator can be in the form of an eddy-current coupling. 
     Furthermore, the present invention relates to a groove milling device for milling a groove in a component which comprises a T-groove cutter that is rotatable about a radial direction of the groove, and in particular, a device for carrying out the method in accordance with any of the claims  40  to  60 . 
     The object of the present invention is to provide such a groove milling device with the aid of which a groove having at least one undercut section having a curved undercut surface which is in the form of an arc of a circle in longitudinal section can be produced in a simple and precise manner. 
     In accordance with the invention, this object is achieved in the case of a groove milling device incorporating the features indicated in the first part of claim  69  in that the groove milling device comprises a guidance device for guiding the groove milling device in a pre-milled guide groove having a curved groove base surface which is in the form of an arc of a circle in a longitudinal section. 
     A pre-milled guide groove without undercut sections can be widened into the desired groove with undercut sections with the aid of this groove milling device in accordance with the invention. 
     Hereby, the guide groove can be pre-milled using a conventional groove milling device. 
     In a preferred embodiment of the groove milling device in accordance with the invention, provision is made for the guidance device to comprise a front guide element which is in the form of a section of a substantially circular disk and is arranged in front of the T-groove cutter in the direction of movement of the groove milling device during the milling process. 
     In order to obtain stable guidance of the groove milling device in the pre-milled guide groove by means of the front guide element, it is expedient if the thickness of the front guide element is of substantially the same size as the width of the pre-milled guide groove. 
     Furthermore, it is expedient if the guidance device comprises a rear guide element which is in the form of a section of a substantially circular disk and is arranged behind the T-groove cutter in the direction of movement of the groove milling device during the milling process. In this way, it is possible to obtain additional guidance for the groove milling device in the groove produced by means of the T-groove cutter. 
     In order to enable particularly stable guidance on the base section of the groove milled by the T-groove cutter to be obtained, it is expedient if the thickness of the rear guide element is of substantially equal to the width of a base section of the groove milled by the T-groove cutter. 
     Furthermore, the rear guide element can be provided with at least one guide tooth which engages in an undercut section of the groove milled by the T-groove cutter during the milling process and thus guides the groove milling device. This thereby provides particularly stable guidance for the groove milling device on the undercut section milled by the T-groove cutter. 
     Further features and advantages of the invention form the subject matter of the following description and the graphical illustration of exemplary embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic perspective illustration of two components that are to be connected whilst they are in the unconnected state, wherein each component comprises a respective groove having a central base section and two arc-shaped undercut sections protruding from the base section; 
         FIG. 2  a schematic perspective illustration corresponding to  FIG. 1  in which the non visible edges are additionally drawn-in in broken lines; 
         FIG. 3  a schematic cross section through the first component depicted in  FIGS. 1 and 2  in the vicinity of an access boring; 
         FIG. 4  a schematic side view of the first component depicted in  FIGS. 1 and 2 ; 
         FIG. 5  a schematic perspective illustration of a connecting means for connecting the two components depicted in  FIGS. 1 to 4 , which comprises a first connecting element having a holding element and a second connecting element having a seating for the holding element; 
         FIG. 6  a schematic perspective illustration corresponding to  FIG. 5  in which the non visible edges are additionally drawn-in in broken lines; 
         FIG. 7  a schematic perspective side view of the components connected by the connecting means depicted in  FIGS. 5 and 6 ; 
         FIG. 8  a schematic perspective illustration of the two components that are to be connected together whilst they are in the unconnected state wherein a respective one of the connecting elements is inserted into the groove in each component; 
         FIG. 9  a schematic perspective illustration corresponding to  FIG. 8  in which the non visible edges are additionally drawn-in in broken lines; 
         FIG. 10  a schematic perspective illustration of a groove cutting device including a displacement device, wherein a rotatable milling disk of the groove cutting device is withdrawn into a housing of the groove cutting device; 
         FIG. 11  a schematic perspective illustration of the groove cutting device corresponding to  FIG. 10  wherein the rotatable milling disk has been partly extended from the housing of the groove cutting device; 
         FIGS. 12 to 15  a sequence of schematic cross sections through a component in which a groove incorporating a base section and two undercut sections protruding from the base section is being milled by means of the groove cutting device depicted in  FIGS. 10 and 11 ; 
         FIG. 16  a schematic perspective illustration of a groove cutting device incorporating a T-groove cutter and a guidance device for guiding the groove cutting device in a pre-milled guide groove; 
         FIGS. 17 ,  19  and  21  schematic side views of a component in which a groove having a base section and two arc-shaped undercut sections protruding from the base section is milled by means of the groove cutting device depicted in  FIG. 16 ; 
         FIGS. 18 ,  20  and  22  schematic cross sections corresponding to  FIGS. 17 ,  19  and  21  through the groove formed in the component; 
         FIG. 23  a schematic side view of the first component into the groove of which the first connecting element is inserted; 
         FIG. 24  a schematic side view of both components with inserted connecting elements which are to be moved towards one another; 
         FIG. 25  a schematic side view of the components with the contact areas thereof lying close together and a polygonal key which is in engagement with the holding element of the first connecting element through an access boring; 
         FIG. 26  a schematic side view of the two components and the polygonal key by means of which the holding element is moved from a release position into a holding position; 
         FIG. 27  a schematic side view of a housing of the first connecting element; 
         FIG. 28  a schematic section through the housing of the connecting element depicted in  FIG. 27 , along the line  28 - 28  in  FIG. 27 ; 
         FIGS. 29 to 31  schematic cross sections corresponding to  FIG. 28  through the housing of the connecting element depicted in  FIG. 27 , wherein holding projections of the housing each have different profiles; 
         FIG. 32  a schematic perspective illustration of a second embodiment of the connecting means in which the holding part of the first connecting element is in the form of a threaded element which can engage in a restraining element provided on the second connecting element; 
         FIG. 33  a schematic perspective illustration corresponding to  FIG. 32  in which the non visible edges are additionally drawn-in in broken lines; 
         FIG. 34  a schematic side view of the two components which are connected together by means of the second embodiment of the connecting means; 
         FIG. 35  a schematic perspective illustration of a third embodiment of the connecting means in which a magnet element is provided in the first connecting element for causing a holding element to execute a rotational movement; 
         FIG. 36  a schematic perspective illustration corresponding to  FIG. 35  in which the non visible edges are additionally drawn-in in broken lines; 
         FIG. 37  a schematic side view of the two components which are connected together by means of the third embodiment of the connecting means; 
         FIG. 38  a schematic side view of a magnet element and a holding element of the third embodiment of the connecting means depicted in  FIGS. 35 to 37  and a drive unit for producing a rotational movement of the magnet element; 
         FIG. 39  a schematic plan view from below of the magnet element and the drive unit depicted in  FIG. 38  along the line of sight indicated by the direction of the arrow  39  in  FIG. 38 ; 
         FIG. 40  a schematic perspective illustration of a fourth embodiment of the connecting means in which two pivotal holding elements and a spreading mechanism for separating apart the end regions of the holding elements are provided in the first connecting element; 
         FIG. 41  a schematic side view of the fourth embodiment of the connecting means in the unconnected state of the components; 
         FIG. 42  a schematic side view corresponding to  FIG. 41  wherein the components that are to be connected together are located against one another and the holding elements are in their release position; 
         FIG. 43  a schematic side view of the fourth embodiment of the connecting means corresponding to  FIG. 42  wherein the holding elements are in the holding position; 
         FIG. 44  a schematic side view of the fourth embodiment of the connecting means, of a magnet element of the spreading mechanism and of a drive unit for causing rotation of the magnet element; 
         FIG. 45  a schematic plan view of the magnet element and the drive unit depicted in  FIG. 44  along the line of sight indicated by the direction of the arrow  45  in  FIG. 44 ; 
         FIG. 46  a schematic perspective illustration of a fifth embodiment of the connecting means in which the first connecting element and the second connecting element are glued to one another; 
         FIG. 47  a schematic perspective illustration corresponding to  FIG. 46  in which the non visible edges are additionally drawn-in in broken lines; and 
         FIG. 48  a schematic side view of the connecting means depicted in  FIGS. 46 and 47  in the connected state of the components. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Similar or functionally equivalent elements are designated by the same reference symbols in each of the Figures. 
     A first embodiment of a connecting means which is illustrated in  FIGS. 1 to 9  and bears the general reference  100  is explained in the following using the example of the connection of a first substantially plate-like component  102  to a second likewise substantially plate-like component  104  (see  FIGS. 1 to 4 ). 
     The two components  102  and  104  consist for example of wood or plywood, but could consist of any other type of material, for example, of a metallic material or a synthetic material (for example plexiglass). Furthermore, provision may be made for the first component  102  and the second component  104  to consist of materials differing from each other. 
     In the connected state of the two components  102  and  104  which is illustrated in  FIG. 7 , a contact area  106  forming a narrow side of the first component  102  abuts a contact area  108  of the second component  104  which forms a major face of the plate-like second component  104 . 
     A respective groove  110 , which is formed in the relevant component  102  and  104  and comprises a base section  112  in the form of a segment of a regular cylinder or a section of a regular cylinder and two undercut sections  114  extending away from the base section  112  in the thickness direction  116 , opens out into each of the contact areas  106 ,  108 . 
     The radius of curvature of the base section  112  is larger than the groove depth T (see  FIG. 4 ), so that the arched groove base surface  118  intersects the respective contact area  106 ,  108  at an acute angle. 
     The base section  112  of the groove  110  has a width B in the thickness direction  116  of approximately 8 mm for example. 
     Each of the undercut sections  114  of the groove  110  is bounded on the side thereof remote from the respective contact area  106  and  108  by a base surface  120  which is flush with the groove base surface  118  and is in the form of a section of the surface of a regular cylinder and has the same radius of curvature as the groove base surface  118  of the base section  112 . 
     In the direction toward the contact area  106  or  108 , each undercut section  114  is bounded by an undercut surface  122  which is likewise in the form of a section of the surface of a regular cylinder and is formed such as to be concentric with the base surface  120  and has a smaller radius of curvature. 
     In the lateral direction, each of the undercut sections  114  is bounded by a lateral boundary surface  124  running perpendicularly relative to the respective contact area  106  and  108 . 
     The width b i.e. the extent thereof in the thickness direction  116 , for each of the undercut sections  114  amounts to approximately 1 mm for example. 
     The height h, i.e. the distance between the base surface  120  and the undercut surface  122 , for each of the undercut sections  114  amounts to approximately 2 mm for example. 
     The base section  112  of each groove  110  is bounded by lateral boundary walls  126  which run substantially perpendicularly relative to the respective contact area  106  or  108  and are spaced from each other by the groove width B. 
     As can be seen from  FIG. 3  for example, a substantially cylindrical access boring  128  opens out into the groove  110  of the first component  102 , said boring running perpendicularly relative to one of the lateral boundary walls  126  and the other end thereof opening out at a major face  129  of the plate-like first component  102 , this thereby enabling access to the base section  112  of the groove  110  to be made from the exterior of the first component  102 . 
     In order to form the previously described grooves  110  in the components  102  and  104 , the groove cutting device  130  schematically illustrated in  FIGS. 10 and 11  can be used for example. 
     This groove cutting device  130  comprises an electrically insulated housing  132  which has a substantially flat lower bearing surface  134  and, oriented at right-angles thereto, a substantially flat front bearing surface  136 . 
     The front bearing surface  136  comprises a passage slot  138  through which a section of a milling disk  140  can pass, said disk being held such that it can rotate about a vertical rotational axis  142  in the interior of the housing  132  and it is caused to make such a rotational movement about the rotational axis  142  by means of an electrical drive motor  144 . 
     The milling disk  140  comprises radially projecting milling teeth  146  around its periphery for milling the base section  112  of a groove  110  and annular groove teeth  148  which project in the axial direction and serve for milling the undercut sections  114 . 
     The drive motor  144  and the milling disk  140  attached thereto can be raised or lowered automatically along the axial direction  151  of the milling disk  140  by means of a displacement device  150 . The displacement device  150  and the drive motor  144  are accommodated in a drive unit  152  of the groove cutting device  130  which is displaceable relative to the housing  132 , by means of a handle  154  arranged thereon, in a displacement direction  156  running radially relative to the rotational axis  142  of the milling disk  140  and perpendicularly relative to the front stop surface  136 . 
     The displacement device  150  for the axial movement of the milling disk  140  can be implemented as a normal electric motor and associated transmission or as a stepping motor. 
     The necessary energy for the displacement movement can be produced by means of a mains power pack or a generator which is coupled to the main drive spindle of the groove cutting device  130 . 
     In particular, the generator can be implemented as an electrically controllable eddy-current coupling wherein an arbitrarily adjustable torque can be transferred to a reciprocating means which can mechanically convert this torque into a reciprocating movement of the milling disk  140  without the use of an additional motor, for example, by means of a crank drive arrangement or with the help of an adjustable swash plate. 
     The stroke path, over which the milling disk  140  is raised or lowered in the axial direction  151  by the actuation of the displacement device  150 , is manually selectable by means of a selector switch or by means of a CNC control system. 
     The manner of functioning of the previously described groove cutting device  130  is as follows: 
     The front bearing surface  136  of the groove cutting device  130  is placed on the contact area  106  of that component (for example the first component  102 ) in which the groove  110  is intended to be formed. 
     Subsequently, the milling disk  140  is set into rotational movement and is pushed out of the housing  132  against the component  102  that is to be worked upon by means of the handle  154  so that the milling disk  140  mills out from the component  102  a base section  112  which is in the form of a section of a regular cylinder having an increasing groove depth (see  FIG. 12 ). 
     When the desired groove depth T is reached, a displacement process of the milling disk  140  is initiated by means of the displacement device  150 , whereupon the milling disk  140  is moved upwardly in the axial direction  151  by the desired width b of the undercut section  114  and the upper undercut section  114  of the groove  110  is then milled by means of the annular groove teeth  148  (see  FIG. 13 ). 
     Subsequently, the milling disk  140  is moved downwardly in the opposite direction back into the initial position and then continues to be moved further downwardly by the desired width b of the undercut section  114 , whereby the annular groove teeth  148  of the milling disk  140  now mill the lower undercut section  114  (see  FIG. 14 ). 
     When the lower undercut section  114  has also been milled, the milling disk  140  is moved back upwardly along the axial direction  151  into its initial position and is withdrawn from the finished groove  110  in the direction of displacement  156  by pulling back the handle  154  (see  FIG. 15 ). 
     Initiation of the displacement process can be effected by means of a manually operated switch on the groove cutting device  130  for example. 
     As an alternative thereto, provision may also be made for the groove cutting device  130  to comprise a depth probe which automatically initiates the displacement process of the displacement device  150  when the desired groove depth T is reached i.e. when the milling disk  140  has moved out from the housing  132  by a predetermined distance. 
     Once the displacement process has been initiated, the further time sequence of the displacement process, i.e. the movement of the milling disk  140  upwardly by the distance b, the subsequent movement of the milling disk  140  downwardly by the distance  2   b  and the concluding movement of the milling disk  140  upwardly by the distance b into the starting position is effected automatically by appropriately controlling the displacement device by means of a (not illustrated) control device of the groove cutting device  130 . 
     In this way, the groove  110  including the undercut sections  114  can be produced in a simple manner in just a single processing step. 
     As an alternative to the groove cutting device  130  illustrated in  FIGS. 10 and 11 , the groove cutting device  158  illustrated in  FIG. 16  could also be used for the production of the grooves  110  in the components  102  and  104 . 
     This groove cutting device  158  comprises an electrical drive unit in an insulated housing  160  and a machining head  162  which is mounted thereon and comprises a T-groove cutter  164  that is rotatable about a rotational axis  166 . 
     The T-groove cutter  164  comprises a shank part  168  having a diameter which corresponds to the diameter B of the base section  112  of the groove  110  that is to be milled, and a head part  170  the diameter of which corresponds to the sum, B+2b, of the widths of the base section  112  and the undercut sections  114 . 
     Furthermore, the groove cutting device  158  comprises a guidance device  172  for guiding the groove cutting device  158  in a pre-milled guide groove  174  (see  FIGS. 17 and 18 ). 
     This guidance device  174  comprises a quarter-circular disk-shaped front guide element  174  which is arranged in front of the T-groove cutter  164  in the direction of movement of the groove cutting device  158  during the milling process and the thickness thereof is substantially equal to the width B′ of the pre-milled guide groove  174 . 
     Furthermore, the guidance device  172  comprises a substantially quarter-circular disk-shaped rear guide element  178  which is arranged behind the T-groove cutter  164  in the direction of movement of the groove cutting device  158  during the milling process and the thickness thereof corresponds substantially to the width B of the base section  112  of the groove  110  that is to be milled. 
     Furthermore, the rear guide element  178  is provided with two guide teeth  180  which are arranged directly behind the head part  170  of the T-groove cutter  164  and which extend respectively upwardly and downwardly in the thickness direction of the rear guide element  178  by the desired width b of the undercut sections  114  of the groove  110  that is to be milled. 
     The groove  110  is produced in the contact area  106  of the first component  102  for example using the previously described groove cutting device  158  as follows: 
     Firstly, a guide groove  174  in the form of a section of a regular cylinder the groove depth T of which corresponds to the groove depth of the groove  110  that is to be produced and the width B′ of which is smaller than the width B of the base section  112  of the groove  110  that is to be formed is produced by means of a groove cutting device which is known and does not therefore need to be described in detail here (see  FIGS. 17 and 18 ). 
     In particular, the width B′ of the guide groove  174  may amount to approximately 4 mm for example. 
     Subsequently, the guide groove  174  is widened out to form the desired groove  110  with the undercut sections  114  by means of the groove cutting device  158 . 
     For this purpose, the front guide element  176  of the guidance device  172  is entered into the guide groove  174  until such time as the outer surface  182  of the front guide element  176 , which is in the form of a section of the surface of a regular cylinder and has the same radius of curvature as the guide groove  174 , abuts flush against the groove base surface of the guide groove  174  and the T-groove cutter  164  is still located in front of the contact area  106 . 
     Subsequently, the groove cutting device  158  is pivoted in such a way that the outer surface  182  of the front guide element  176  slides along the arc-shaped curved groove base surface of the guide groove  174  and the T-groove cutter  164  thereby enters into the first component  102  and mills both the widened base section  112  of the groove  110  as well as its undercut sections  114  (see  FIGS. 19 and 20 ). 
     Thereby, the guide teeth  180  arranged on the rear guide element  178  run in the undercut sections  114  of the groove  110  that were produced by the T-groove cutter  164  and therefore provide additional guidance for the groove cutting device  158 . 
     The groove cutting device  158  continues to be pivoted along the guide groove  174  until such time as the T-groove cutter  164  emerges from the component  102  at the end of the guide groove  174  opposite the starting point and the guide teeth  180  are also no longer in engagement with the undercut sections  114  of the groove  110  that has been produced. 
     The groove cutting device  158  can now be withdrawn from the component  102 , and the groove  110  including its undercut sections  114  is finished (see  FIGS. 21 and 22 ). 
     After the grooves  110  in the first component  102  and the second component  104  have been produced, the access boring  128  connecting the one major face  129  to the base section  112  of the groove  110  is then produced in the first component  102 . 
     The connecting means  100  which connects the two components  102  and  104  together comprises a first connecting element  184  for insertion into the groove in the first component  102  and a second connecting element  186  for insertion into the groove  110  in the second component  104 , such as are illustrated in  FIGS. 5 to 7 . 
     The first connecting element  184  comprises a housing  188  that is substantially in the form of a section of a regular cylinder and includes an arc-shaped curved bearing surface  190  which is in the form of an arc of a circle in a longitudinal section taken in the longitudinal direction  192  of the connecting element  184 , and also a flat bearing surface  194  located opposite the curved bearing surface  190  as well as two lateral side faces  198  running substantially parallel to the direction of connection  196 . 
     A respective arc-shaped curved holding projection  200  protrudes from the lower edge of the side faces  198  in a thickness direction  202  which is perpendicular to the longitudinal direction  192  and the direction of connection  196 . 
     Each holding projection  200  is bounded in the direction towards the bearing surface  194  by an arc-shaped curved supporting surface  204  which is in the form of an arc of a circle in a longitudinal section taken along the longitudinal direction  192   
     Each holding projection  200  is bounded on the side remote from the bearing surface  194  by a likewise arc-shaped curved bearing surface which is in the form of an arc of a circle in a longitudinal section taken along the longitudinal direction  192  and adjoins the bearing surface  190  of the housing  188  in flush manner. 
     The supporting surface  204  and the bearing surface  206  of each holding projection  200  are connected to one another by a side face  208  which runs substantially parallel to the longitudinal direction  192  and is parallel with the direction of connection  196 . 
     The profile of each holding projection  200  substantially corresponds to the profile of the respectively associated undercut section  114  of the groove  110 , and the curvature of the holding projection  200  corresponds to the curvature of the associated undercut section  114  so that the holding projections  200  of the first connecting element  184  are insertible into the undercut sections  114  of the groove  110  and are adapted to be displaced therein in sliding manner. 
     Furthermore, the first connecting element  184  comprises a seating chamber  210  that is surrounded by the housing  188  for accommodating a holding element  212  which can emerge from the seating chamber  210  through a mouth  214  at which the seating chamber  210  opens out into the bearing surface  194  of the first connecting element  184 . 
     The seating chamber  210  can extend on the side thereof remote from its bearing surface  194  into the curved bearing surface  190 . 
     The holding element  212  comprises a plate-like base body  216  which, at one end, is provided with ring-like elevated portions  218  that surround a seating opening  220  having a polygonal cross section which is aligned with a substantially circular passage opening  222  in one of the side faces  198  of the housing  188 . 
     The ring-like elevated portions  218  are supported on abutments which are arranged in the seating chamber  210  so that the holding element  212  is held on the housing  188  such as to be rotatable about the central axis  224  of the seating opening  220 . 
     The free end of the holding element  212  remote from the ring-like elevated portions  218  is provided with arc-shaped projections  226  which project from the base body  216  on both sides thereof in the thickness direction  202 . 
     Furthermore, on both sides of the mouth  214  of the seating chamber  210 , the first connecting element  184  comprises a respective insertible projection  228  in the form of a substantially parallelepipedal dowel pin  230  which extends in the direction of the connection  196  commencing from the bearing surface  194  and tapers towards the end thereof remote from the bearing surface  194  in order to facilitate the insertion thereof into a respective seating pocket  232  of the second connecting element  186  that is complementary to the dowel pin  230 . 
     The insertible projections  228  of the first connecting element  184  fit very precisely into the seating pockets  232  of the second connecting element  186  in the thickness direction  202  so that the insertible projections  228  can accommodate the shear stresses of the connection between the components  102  and  104  in the thickness direction  202 , and, additional dowel pins, such as are necessary in the case of most other connecting means, can be dispensed with. 
     In the longitudinal direction  192  however, the seating pockets  232  have a greater extent than the insertible projections  228  so that the first connecting element  184  and the second connecting element  186  can be mutually displaced in the longitudinal direction  192  in order to enable the tolerances in the connection between the components  102  and  104  to be compensated for in this way. 
     The second connecting element  186  likewise comprises a housing  234  which is substantially in the form of a section of a regular cylinder and has an arc-shaped curved bearing surface  190  that is in the form of an arc of a circle in a longitudinal section taken along the longitudinal direction  192  of the connecting element  186 , a flat bearing surface  194  located opposite the curved bearing surface  190 , side faces  198  and holding projections  200  which protrude from the side faces  198  in the thickness direction  202 , said projections having a curved supporting surface  204  directed towards the bearing surface  194 , a curved bearing surface  206  that is flush with the bearing surface  190  and a side face  208 . 
     Furthermore, as can best be seen from  FIG. 6 , apart from the seating pockets  232  for the insertible projections  228  of the first connecting element  184 , the housing  234  of the second connecting element  186  also comprises a receiving chamber  236  which is arranged centrally between the seating pockets  233  and opens out into a mouth  238  in the bearing surface  194  and can extend into the bearing surface  190  on the opposite side. 
     Protruding into the interior of the receiving chamber  236  from both sides of the mouth  238 , there is a respective restraining projection  240  which is in the form of a section of a regular cylinder and has an arc-shaped curved restraining surface  242  in the thickness direction  202  so as to leave a gap between the two restraining projections  240  the width of which is slightly greater than the thickness of the base body  216  of the holding element  212  of the first connecting element  184 . 
     For the purposes of establishing the releasable connection between the first component  102  and the second component  104  by means of the connecting means  100  consisting of the first connecting element  184  and the second connecting element  186 , one proceeds as follows: 
     Firstly, as is illustrated in  FIG. 23 , the first connecting element  184  is pushed into the groove  110  in the first component  102  in such a way that the holding projections  200  of the first connecting element  184  engage in the undercut sections  114  of the groove  110  and the passage opening  222  in the side face  198  of the housing  188  aligns with the access boring  128  in the first component  102  (see  FIG. 24 ). 
     In like manner, the second connecting element  186  is pushed into the groove  110  in the second component  104  in such a way that its holding projections  200  engage in the undercut sections  114  of the groove  110  and the housing  234  of the second connecting element  186  is accommodated substantially entirely in the groove  110  (see  FIG. 24 ). 
     The holding element  212  of the first connecting element  184  is then pivoted completely into the seating chamber  210  of the first connecting element  184  (see  FIG. 24 ). 
     In this release position of the holding element  212 , the two components  102  and  104  can be moved against each other until their contact areas  106  and  108  as well as the bearing surfaces  194  of the connecting elements  184  and  186  fit together in flush manner and the insertible projections  228  of the first connecting element  184  engage in the seating pockets  232  of the second connecting element  186  (see  FIG. 25 ). 
     Then, the actuating end of a cranked polygonal key  244  is introduced through the access boring  128  in the first component  102  and the passage opening  222  in the housing  188  of the first connecting element  184  into the seating opening  220  of the holding element  212  and brought into engagement with the latter (see  FIG. 25 ). 
     Subsequently, the holding element  212  is pivoted out from the seating chamber  210  of the first connecting element  184  by means of the polygonal key  242  so that the arc-shaped projections  226  of the holding element  212  enter the receiving chamber  236  of the second connecting element  186  through the mouth  238  and thereby engage behind the restraining projections  240 . 
     The curvature of the arc-shaped projections  226  of the holding element  212  on the one hand and the curvature of the restraining surfaces  242  of the restraining projections  240  are matched to one another in such a way that the two connecting elements  184  and  186  are pulled against each other to an increasing extent in the direction of the connection  196  during the process of pivoting the holding element  212  into the receiving chamber  236  and there results as large a contact area as possible between the restraining surfaces  242  and the arc-shaped projections  226  of the holding element  212 . 
     In consequence, compression stress points in the contact areas between the restraining projections  240  and the arc-shaped projections  226  of the holding element  212  are prevented and the strength of the material from which the holding element  212  and the housing  234  of the second connecting element  186  are made is used as uniformly as possible. 
     The holding element  212  and the housings  188  and  234  of the respective connecting elements  184  and  186  can therefore be made, in particular, of an injection moulded synthetic material. 
     When the connection between the connecting elements  184  and  186  is loaded in the direction of connection  196 , the holding element  212  experiences substantially only tension and thrust forces, but only to a negligibly small degree, bending moments. 
     The seating chamber  210  of the first connecting element  184 , the receiving chamber  236  of the second connecting element  186  and the outer contours of the connecting elements  184  and  186  are formed in such a way that they can be manufactured in one-piece manner. 
     The holding element  212  can be pushed into the seating chamber  210  through the mouth of the seating chamber  210  onto the bearing surface  190  of the first connecting element  184  so that the housing  188  of the first connecting element  184  does not need to be separable. 
     Consequently, one can dispense with constructing the housing  188  of the first connecting element  184  in the form of two half-shells, this thereby increasing the rigidity of the first connecting element  184 . 
     Since the curved bearing surfaces  190  of the connecting elements  184  and  186  have the same radius of curvature as the groove base surfaces  118  of the grooves  110  upon which the bearing surfaces  190  can slide and abut, and since the holding projections  200  of the connecting elements  184  and  186  in the form of an arc of a circle can be displaced tangentially in the respectively associated undercut sections  114  of the grooves  110  using just a small amount of force and hence the connecting elements  184  and  186  still have a certain degree of freedom of movement when establishing the connection, it is still possible to make corrections with respect to the mutual positioning of the connecting elements  184  and  186  during the process of connecting the components  102  and  104 . 
     This significantly reduces the need for precision in regard to the location of the grooves  110  in the components  102  and  104  and thus leads to it being considerably easier for the user to use. 
     When the holding element  212  is moved from the release position illustrated in  FIG. 25  into the holding position illustrated in  FIG. 26 , then, due to the tensile forces which act on the connecting elements  184  and  186  in the direction of connection  196 , such a large amount of static friction will be produced between the supporting surfaces  204  of the holding projections  200  on the one hand and the undercut surfaces  122  of the undercut sections  114  of the grooves  110  which are thereby in contact therewith on the other that the previously described remaining degree of freedom of movement is neutralised and an extremely firm connection between the components  102  and  104  is established. 
     As a result of the support for the holding projections  200  on the undercut surfaces  122  of the undercut sections  114  of the grooves  110  in the components  102  and  104 , the connecting elements  184  and  186  are thus securely anchored in the respectively associated component  102  and  104 . 
     In the holding position illustrated in  FIGS. 7 and 26 , the holding element  212  in cooperation with the restraining projections  240  prevents a relative movement of the first connecting element  184  and the second connecting element  186  along the direction of the connection  196 . 
     In order to then release the first component  102  and the second component  104  from each other, it is only necessary to again insert a polygonal key  244  through the access boring  128  in the first component  102  so as to engage with the seating opening  220  in the holding element  212  and then to move the holding element  212  by pivoting it in the opposite direction from the holding position into the release position illustrated in  FIG. 25  in which the arc-shaped projections  226  of the holding element  212  no longer engage behind the restraining projections  240  of the second connecting element  186  so that the connecting elements  184  and  186  can easily be moved apart along the direction of connection  196 . 
     As can be seen from  FIGS. 27 to 31 , the profiles of the holding projections  200  do not by any means always have to be formed such that they are exactly rectangular, as is illustrated in  FIG. 28 . 
     Rathermore, provision could also be made for the profile of the holding projections  200  to be trapezoidal, this then tapering with increasing spacing from the side faces  198  of the respective housing  188  and  234 , as is illustrated in  FIG. 29 . 
     As an alternative thereto, provision may also be made for the profile of the holding projections  200  to taper with decreasing spacing from the respectively associated side face  198 , as is illustrated in  FIG. 30 . 
     Furthermore, provision may be made for the profile of the holding projections  200  to have an outer contour which is curved at least in sections thereof, for example a semicircular outer contour, such as is illustrated in  FIG. 31 . 
     A second embodiment of a connecting means  100  which is illustrated in  FIGS. 32 to 34  differs from the previously described first embodiment in that the holding element  212  in the second embodiment is formed as a threaded element  246  having an external thread  248  which is brought into engagement with an internal thread  250  of a restraining element  252  of the second connecting element  186  for the purposes of connecting the two components  102 ,  104 . 
     As can best be seen from  FIG. 33 , the threaded element  246  of the first connecting element  184  comprises outside the external thread  248  a cylindrical head part  254  having a central seating  256  for an actuating section of a (not illustrated) actuating element such as a polygonal key or a screwdriver for example, wherein the seating  256  has a polygonal cross section complementary to the cross section of the actuating section. 
     Between the head part  254  and the external thread  248  of the threaded element  246 , there is arranged a cylindrical shank part  258  which has a smaller diameter than the head part  254 . 
     The head part  254  and the shank part  258  are arranged in a stepped seating chamber  260  of the housing  188  of the first connecting element  184  which has a lower chamber section  262  of greater diameter and an upper chamber section  264  of lesser diameter, wherein the two chamber sections  262 ,  264  merge into one another at a shoulder  266  on which the head part  254  of the threaded element  246  is supported. 
     The upper chamber section  264  extends upwardly along the direction of connection  196  and opens out into the bearing surface  194  of the first connecting element  184 . 
     The threaded element  246  serving as a holding element  212  is thus arranged on the first connecting element  184  such that it is rotatable about an axis of rotation  268  that is oriented parallel to the direction of connection  196 . 
     The restraining element  252  of the second connecting element  186  has a parallelepipedal outer contour and is held such that it is displaceable in the longitudinal direction  192  in non rotatable manner in a likewise parallelepipedal seating chamber  270  in the housing  234  of the second connecting element  186 . 
     The seating chamber  270  is pierced by an access channel  272  which extends along the direction of the connection  196  from the bearing surface  194  of the second connecting element  186  through the seating chamber  270  up to the curved bearing surface  190  of the second connecting element  186  and it has an elongate and in particular, oval cross section. 
     For the purposes of establishing the connection between the first component  102  and the second component  104 , the first connecting element  184  and the second connecting element  186  of the second embodiment of the connecting means  100  are inserted into the respective grooves  110  of the first component  102  and the second component  104 . 
     Then, the second component  104  with the second connecting element  186  is placed on the first component  102  with the first connecting element  184  in such a way that the external thread  248  of the threaded element  246  extends through the access channel  272  of the second connecting element  186  into the seating chamber  250  and comes into engagement with the internal thread  270  of the restraining element  252 . 
     Subsequently, the threaded element  246  is set into rotation about the rotational axis  268  by means of the (not illustrated) actuating element (a screwdriver for example) which engages in the seating  256  in the head part  254  of the threaded element  246  through an access boring in the first component  102  so that the external thread  248  of the threaded element  246  is screwed into the internal thread  250  of the restraining element  252  and hence the second connecting element  186  is pulled against the first connecting element  184  until the state illustrated in  FIG. 34  is reached, in which the bearing surfaces  194  of the two connecting elements  184 ,  186  fit flushly together and the external thread  248  extends beyond the seating chamber  270  into the section of the access channel  272  lying between the seating chamber  270  and the bearing surface  190  of the second connecting element  186 . 
     In order to enable the actuating element to engage in the seating  256  in the head part  254  of the threaded element  246 , the access boring in the first component  102  in the case of this embodiment is aligned coaxially with respect to the axis of rotation  268  of the threaded element  246  and thus parallel to the direction of the connection  196 . 
     In this embodiment, the separation of the two components  102  and  104  from each other is effected in that the external thread  248  is unscrewed from the internal thread  250  of the restraining element  252  by rotating the threaded element  246  in the opposite direction by means of the (not illustrated) actuating element until the threaded element  246  is no longer in engagement with the restraining element  252  and the second connecting element  186  can thus be removed from the first connecting element  184 . 
     Due to the displaceability of the restraining element  252  in the longitudinal direction  192  and as a result of the elongate cross section of the access channel  272 , it is possible to have a certain amount of relative movement between the threaded element  246  and the housing  234  of the second connecting element  186  when establishing the connection between the first component  102  and the second component  104  so that tolerances in the positioning of the grooves  110  in the components  102 ,  104  can thereby be compensated for. 
     The second embodiment of the connecting means  100  illustrated in  FIGS. 32 to 34  does not comprise insertible projections on the first connecting element  184 , but, in like manner to the first embodiment, it does comprise holding projections  200  on the connecting elements  184  and  186 . 
     In all other respects, the second embodiment of the connecting means  100  illustrated in  FIGS. 32 to 34  coincides in regards to the construction and manner of functioning thereof with the first embodiment illustrated in  FIGS. 1 to 31 , so that to this extent reference is made to the previous description thereof. 
     A third embodiment of the connecting means  100  illustrated in  FIGS. 35 to 39  differs from the previously described first embodiment in that the housing  188  of the first connecting element  184  comprises a hump-like elevated portion  274  between the two insertible projections  228 , said elevated portion engaging in a complementarily shaped depression  276  in the housing  234  of the second connecting element  186  in the connected state of the components  102 ,  104  (see  FIG. 37 ). 
     A certain amount of play is present in the longitudinal direction  192  between the elevated portion  274  and the depression  276  so that tolerances in the positioning between the grooves  110  and the components  102 ,  104  can be compensated for. 
     In this embodiment, the holding element  212  of the first connecting element  184  is formed as a threaded element  278  which comprises a hollow cylindrical socket section  280  having an internal thread  282  and a shaft section  284  that extends downwardly from the socket section  280  along the direction of connection  196  and has a smaller diameter than the socket section  280  as well as a driven element  286  which projects downwardly from the periphery of the socket section  280  in the axial direction (see in particular,  FIG. 38 ). 
     As can best be seen from  FIG. 36 , the threaded element  278  is arranged in a stepped seating chamber  288  of the housing  188  of the first connecting element  184 , said chamber comprising a lower chamber section  290  of greater diameter and an upper chamber section  292  of lesser diameter wherein these chambers merge into one another at a shoulder  294 . 
     The threaded element  278  is arranged in the seating chamber  288  such as to be rotatable about an axis of rotation  296  oriented parallel to the direction of connection  196 . 
     Furthermore, in order to be able to produce a rotational movement of the threaded element  278  about the axis of rotation  296 , there is provided in the lower chamber section  290  of the seating chamber  288  a hollow cylindrical magnet element  298  which is aligned coaxially with respect to the threaded element  278  and is pushed partially onto the shaft section  284  of the threaded element  278  and it is provided at the end face thereof facing the socket section  280  with an axially projecting driver element  300  (see in particular,  FIG. 38 ). 
     The magnet element  298  consists of a permanent magnet material which is magnetized substantially perpendicularly to its longitudinal axis and thus perpendicularly to the axis of rotation  296  (so-called diametrical magnetization). 
     The diametrically magnetized magnet element  298 , which is mounted on the shaft section  284  of the threaded element  278  such as to be rotatable about the axis of rotation  268 , can be caused to make an oscillatory rotational movement about the axis of rotation  296  by means of a time varying external magnetic drive field that acts on the magnet element  298  from outside the connecting means  100 , said movement producing a directed rotational movement of the threaded element  278  about the axis of rotation  296  due to the interaction between the driver element  300  of the magnet element  298  and the driven element  286  of the threaded element  278 . 
     For this purpose, there is used a drive unit  302  which is schematically illustrated in  FIGS. 38 and 39 , said drive unit comprising a housing  304 , which consists of a synthetic material for example, an electric motor  306  having a drive shaft  308  arranged in the housing  304 , and a drive magnet  310  connected in mutually non-rotatable manner to the drive shaft  308 . 
     The drive magnet  310  is formed as a cylindrical high power permanent magnet which is magnetized substantially perpendicularly to the longitudinal direction  312  of the drive shaft  308  (so-called diametrical magnetization). 
     For the purposes of establishing a rotational movement of the threaded element  278 , one now proceeds as follows: 
     The drive unit  302  is moved relative to the first connecting element  184  into a position in which the longitudinal direction  312  of the drive shaft  308  of the drive unit  302  and the axis of rotation  296  of the threaded element  278  are oriented parallel to each other and the spacing between the drive magnet  310  and the magnet element  298  is as small as possible in order to obtain as strong a mutual interaction of the magnets as possible. The location of the drive unit  302  and that of the magnet element  298  in this position are schematically illustrated in  FIGS. 38 and 39 . 
     If the electric motor  306  of the drive unit  302  is now operated in such a way that the drive shaft  308  and thus the drive magnet  310  rotate in the clockwise direction for example (when viewed along a line of sight indicated by the arrow  39  in  FIG. 38 ), then the north pole (N) and the south pole (S) of the drive magnet  310  thereby rotate in the clockwise direction due to the diametrical magnetization of the drive magnet  310 , as is to be seen in the schematic illustration of  FIG. 39 . 
     The rotational movement of the drive magnet  310  thus produces a rotating and hence time varying magnetic drive field. 
     In order to enable this magnetic drive field to penetrate into the interior of the first connecting element  184  and interact with the magnet element  298 , the housing  188  of the first connecting element  184  consists of a non-ferromagnetic material, for example, it consists of a synthetic material. 
     Since unlike poles of the magnet element  298  and the drive magnet  310  attract one another and like poles of these elements repel each other, the magnet element  298  in the seating chamber  288  rotates in the opposite direction of rotation due to the interaction with the drive magnet  310 , i.e. in the counter clockwise direction (in the line of sight indicated by the arrow  39  in  FIG. 38 ). 
     Due to this rotational movement, the driver element  300  of the magnet element  298  comes into contact with the driven element  286  of the threaded element  278  so that the threaded element  278  is forced by the magnet element  298  into making a rotational movement about the axis of rotation  296  in the same direction of rotation as that of the magnet element  298 . 
     The magnet element  298  and the threaded element  278  carried along thereby follow the rotational movement of the drive magnet  310  until such time as the resistance acting on the threaded element  278  (which, for example, is exerted due to the fact that the internal thread  282  of the threaded element  278  is rotated on a complementary external thread  314  of a restraining element  316  provided on the second connecting element  186 ) becomes so large that the torque being transferred by the rotary magnetic field produced by the drive magnet  310  is no longer sufficient to continue to rotate the threaded element  278 . When such a blockage point is reached, the threaded element  278  and the magnet element  298  then remain in the position they have reached, whilst the drive magnet  310  continues to rotate. 
     After the drive magnet  310  has continued to rotate through approximately 180° so that the like poles of the drive magnet  310  and the magnet element  298  are then located directly opposite each other, the magnet element  298  is again caused to move in a flip-over process, namely, in a direction of rotation having the same sense as the direction of rotation of the drive magnet  310  until the unlike poles of the drive magnet  310  and the magnet element  298  are located directly opposite each other once again. 
     Once this state is reached, the direction of rotation of the magnet element  298  then reverses again, and the magnet element  298  again rotates in the opposite sense to the drive magnet  310 , as occurred in the phase prior to the blockage of the threaded element  278 . 
     The magnet element  298  is now accelerated through approximately half a revolution by the rotating magnetic field of the drive magnet  310  until the driver element  300  again strikes the driven element  286  of the threaded element  278  and the impulse of the magnet element  298  is suddenly transferred to the driven element  286  and thus to the threaded element  278 . Due to this large impulse transmission, the threaded element  278  can release itself from its blockage position and continue to rotate through a certain angle into a position in which a renewed blockage of the threaded element  278  occurs. The magnet element  298  thus stops again in this new blockage position without being able to follow the drive magnet  310  any further until the like poles of the magnet element  298  and the drive magnet  310  are located directly opposite each other again and a renewed flip-over process of the magnet element  298  enables renewed reception of an impulse to occur. 
     The threaded element  278  continues to rotate from blockage position to blockage position in this periodically repeating manner. The repeated receipt of momentum and striking of the driver element  300  against the driven element  286  produce an impact hammer action which powerfully accelerates the rotational movement of the threaded element  278  about the axis of rotation  296  against a resistance. 
     Further details for the process of creating a rotational movement of the threaded element  278  by means of an external drive magnet  310  can be derived from DE 198 07 663 A1 to which reference in this connection is made and which is hereby incorporated as a component part of the present description. 
     Due to the rotational movement of the threaded element  278  that is produced in such a manner, the internal thread  282  of the threaded element  278  can be screwed to the external thread  314  of the restraining element  316  provided on the second connecting element  186  or it can be released from the external thread  314  (upon reversal of the direction of rotation of the drive magnet  310 ). 
     In this embodiment, the restraining element  316  comprises a square head  318  which is fed with a certain amount of play into a parallelepipedal seating chamber  320  within the housing  234  of the second connecting element  186  and thus prevented from rotating about the direction of the connection  196 . 
     From the lower surface of the square head  318 , the external thread  314  of the restraining element  316  extends through an access channel  322  running parallel to the direction of the connection  196  into the depression  276  of the second connecting element  186  so that this external thread  314  is then located opposite the internal thread  282  of the threaded element  278  on the first connecting element  184  (see  FIGS. 35 and 36 ). 
     Furthermore, as can be seen from  FIG. 37 , there is provided in the seating chamber  320  a compression spring  324  which biases the restraining element  316  against the first connecting element  184  in the direction of connection  196 . 
     For the purposes of establishing the connection between the first component  102  and the second component  104  by means of the third embodiment of the connecting means  100 , one proceeds as follows: 
     After the first connecting element  184  and the second connecting element  186  have been inserted into the respective grooves  110  of the first component  102  and the second component  104 , the second component  104  with the second connecting element  186  is moved against the first component  102  with the first connecting element  184  in such a way that the internal thread  282  of the threaded element  278  comes into engagement with the external thread  314  of the restraining element  316 . 
     The insertible projections  228  also penetrate the seating pockets  232  of the second connecting element  186  that are complementary thereto and the hump-like raised portion  274  of the first connecting element  184  enters the depression  276  in the second connecting element  186  that is complementary thereto. 
     Subsequently, in the manner already described hereinabove, the threaded element  278  is caused to effect a rotational movement about the axis of rotation  296  by means of the drive unit  302  in such a manner that the socket section  280  of the threaded element  278  having the internal thread  282  and the restraining element  316  having the external thread  314  are screwed together so that the second connecting element  186  is pulled against the first connecting element  184  and the connection between the components  102  and  104  is established. 
     For the purposes of releasing the connection between the components  102  and  104 , the screwed connection between the threaded element  278  and the restraining element  316  is undone by using the drive unit  302  with the opposite direction of rotation of the drive magnet  310 . 
     In all other respects, the third embodiment of the connecting means  100  illustrated in  FIGS. 35 to 39  coincides in regards to the construction and manner of functioning thereof with the first embodiment illustrated in  FIGS. 1 to 31 , so that to this extent reference is made to the previous description thereof. 
     A fourth embodiment of the connecting means  100  illustrated in  FIGS. 40 to 45  differs from the embodiment illustrated in  FIGS. 1 to 31  in that instead of having two insertible projections  228  on the first connecting element  184 , there is provided just a single central insertible projection  326  which engages in a seating pocket  328  of the second connecting element  186  that is complementary thereto in the connected state of the components  102 ,  104 . 
     Furthermore, in this embodiment, the first connecting element  184  does not comprise just a single holding element  212 , but rather, it comprise two holding elements  212  which are held such as to be pivotal on the housing  188  of the first connecting element  184 , these holding elements being in the form of hinged levers  330  of which one is arranged on each side of the central insertible projection  326 . 
     The inner end regions  332  of the hinged levers  330  which are mounted on bearing projections  335  such as to be pivotal about pivotal axes  333  engage in a seating chamber  334  within the housing  188  and are held at a distance from one another by means of a spreading mechanism  336 . 
     The spreading mechanism  336  itself comprises a first spreading element  338  having a square head  340 , a shank section  342  which extends from the square head  340  in the longitudinal direction  192  and a threaded section  344  having an external thread which adjoins the shank section  342 . 
     Furthermore, the spreading mechanism  336  comprises a second spreading element  346  having a cylindrical head section  348  and a hollow cylindrical socket section  350  which is provided with an internal thread and extends from the head section  348  in the longitudinal direction  192  such as to be coaxial with the shank section  342  of the first spreading element  338 . 
     The internal thread of the socket section  350  of the second spreading element  346  is now in engagement with the external thread of the threaded section  344  of the first spreading element  338 . 
     Furthermore, the socket section  350  is provided at the end thereof facing the square head  340  of the first spreading element  338  with a driven element  352  which projects in the radial direction. 
     Between the square head  340  of the first spreading element  338  and the socket section  350  of the second spreading element  346 , there is a hollow cylindrical magnet element  354  having diametrical magnetization which is arranged on the shank section  342  of the first spreading element  338  such as to be rotatable about the common longitudinal axis  356  of the two spreading elements  338  and  346 . 
     At the end face thereof facing the socket section  350  of the second spreading element  346 , the magnet element  354  is provided with a driver element  358  which projects in the axial direction and which can act on the driven element  352  on the socket section  350 . 
     Between the square head  340  of the first spreading element  338  and the end face of the magnet element  354  facing said square head, there is arranged a compression spring  360  which biases the magnet element  354  against the socket section  350  of the second spreading element  346 . 
     As can best be seen from  FIGS. 44 and 45 , the second spreading element  346  of the spreading mechanism  336  is adapted to be driven in like manner to the threaded element  278  of the previously described third embodiment of the connecting means  100 , by means of a drive unit  302  incorporating a rotary drive magnet  310  which interacts with the magnet element  354 , such as to execute a rotational movement about the longitudinal axis  356  relative to the first spreading element  338  which is held in a constant rotational position by its square head  340 . 
     To this end as illustrated in  FIGS. 44 and 45 , the drive unit  302  is oriented outside the connecting means  100  in such a way that the longitudinal direction  312  of the drive shaft  308  is oriented substantially parallel to the longitudinal axis  356  of the spreading elements  338 ,  346  and the spacing between the drive magnet  310  and the magnet element  354  is made as small as possible. 
     In the housing  234  of the second connecting element  186 , there are provided two receiving chambers  362  into which the outer end regions  364  of the hinged lever  330  can enter when the bearing surfaces  194  of the connecting elements  184  and  186  abut one another. 
     Furthermore, recesses  337  for seating the bearing projections  335  protruding from the housing  188  are provided in the housing  234 . 
     At the edges thereof facing the first connecting element  184 , the receiving chambers  362  are bounded in sectional manner by a respective restraining projection  366  which can be engaged behind by the respectively associated hinged lever  330  when the hinged lever  330  concerned is pivoted about its pivotal axis  333  from the release position illustrated in  FIG. 42  into the holding position illustrated in  FIG. 43 . 
     Such a pivotal action can be effected by means of the previously described spreading mechanism  336 . 
     In this embodiment, the respective housings  188  and  234  of the first connecting element  184  and the second connecting element  186  are preferably formed in two-piece manner, whereby the two parts fit together along the longitudinal centre plane of the respective housing. 
     For the purposes of establishing a connection between the first component  102  and the second component  104  by means of the fourth embodiment of the connecting means  100 , one proceeds as follows: 
     The first connecting element  184  and the second connecting element  186  are inserted into the respective groove  110  in the first component  102  and in the second component  104 . 
     Thereafter, the second component  104  with the second connecting element  186  is placed on the first component  102  with the first connecting element  184  in such a way that the outer end regions  364  of the hinged lever  330  which is located in the release position enter into the receiving chambers  362  of the second connecting element  186  and the central insertible projection  326  of the first connecting element  184  enters into the seating pocket  328  of the second connecting element  186 . 
     Subsequently, the second spreading element  346  is caused to effect a rotational movement about the longitudinal axis  356  by means of the drive unit  302  in such a manner that the head section  348  of the second spreading element  346  is removed from the square head  340  of the first spreading element  338  and hence the overall length of the spreading mechanism  336  increases, whereby the inner end regions  332  of the hinged lever  330  are moved away from each other, the hinged levers  330  are pivoted about their pivotal axes  333  and are thereby moved into the holding position illustrated in  FIG. 43  in which the outer end regions  364  of the hinged lever  330  engage behind the respectively associated restraining projections  366  of the second connecting element  186  and abut said projections so that the second connecting element  186  is locked onto the first connecting element  184  and the connecting elements  184 ,  186  can no longer be moved apart along the direction of connection  196 . 
     In order to release the connection of the components  102 ,  104 , the second spreading element  346  is rotated relative to the first spreading element  338  about the longitudinal axis  356  by means of the drive unit  302  in the reverse direction of rotation so that the head section  348  of the second spreading element  346  is moved towards the square head  340  of the first spreading element  338  and the overall length of the spreading mechanism  336  shortens. 
     The inner end regions  332  of the hinged lever  330  thereupon no longer lie on the square head  340  of the first spreading element  338  or on the head section  348  of the second spreading element  346  so that the spreading mechanism  336  no longer presents any resistance to a pivotal movement of the hinged levers  330  from the holding position illustrated in  FIG. 43  into the release position illustrated in  FIG. 42 . 
     After this process of unlocking the hinged levers  330 , the second connecting element  186  can then be removed from the first connecting element  184  along the direction of connection  196 . 
     In all other respects, the fourth embodiment of the connecting means  100  illustrated in  FIGS. 40 to 45  coincides in regards to the construction and manner of functioning thereof with the first embodiment illustrated in  FIGS. 1 to 31 , so that to this extent reference is made to the previous description thereof. 
     A fifth embodiment of the connecting means  100  which is illustrated in  FIGS. 46 to 48  differs from the first embodiment which is illustrated in  FIGS. 1 to 31  in that no pivotal holding element is provided and in that, instead of having the two insertible projections  228  on the first connecting element  184 , there is provided just a single central insertible projection  378  which is in the form of a substantially parallelepipedal block dowel  380  and projects upwardly from the bearing surface  194 . In the connected state of the components  102 ,  104 , the insertible projection  378  enters a complementary, substantially parallelepipedal seating pocket  382  which is formed in the housing  234  of the second connecting element  186 . 
     For the purposes of establishing a connection between the components  102  and  104  by means of the fifth embodiment of the connecting means  100 , one proceeds as follows. 
     The first connecting element  184  and the second connecting element  186  are inserted into the respective groove in the respective first component  102  and second component  104 . 
     Subsequently, the bearing surface  194  and the insertible projection  378  of the first connecting element  184  and/or the bearing surface  194  and the boundary surfaces of the seating pocket  382  of the second connecting element  186  are provided with a suitable adhesive. 
     Thereafter, the second component  104  with the second connecting element  186  is moved against the first component  102  with the first connecting element  184  in such a way that the insertible projection  378  of the first connecting element  184  enters the seating pocket  382  of the second connecting element  186  and the bearing surfaces  194  of the two connecting elements  184 ,  186  abut. 
     The two components  102 ,  104  are held in this position until the adhesive has hardened and hence an integral bond has been established between the first connecting element  184  and the second connecting element  186  and thus between the first component  102  and the second component  104 . 
     In all other respects, the fifth embodiment of the connecting means  100  illustrated in  FIGS. 46 to 48  coincides in regards to the construction and manner of functioning thereof with the first embodiment illustrated in  FIGS. 1 to 31 , so that to this extent reference is made to the previous description thereof.