Abstract:
A fastener system for connecting and releasing two elements. The system comprises a rod-shaped product with a male part and a female part, in which the male part is sized to be receivable in the female part. Either the male or female part is provided with a screw thread and the other is provided with at least one tooth such that, when the male and female parts are assembled, the tooth is engaged with the screw thread. The part equipped with the tooth comprises a strip extending in the longitudinal direction thereof, so that when the male part is pressed into the female part, the tooth is elastically distorted axially onto the screw thread, and the tooth shape and the screw thread prevent axial movement in the opposite direction.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of International Application No. PCT/EP01/00616, filed Jan. 17, 2001. 
   BACKGROUND OF THE INVENTION 
   The present invention relates to a system for connecting releasingly two elements with each other, comprising a male part being integral or connectable with a first element, and a female part being integral or connectable with the second element, wherein one of the parts, the male or female one, has a round section and is provided with a screw thread and the other part is provided with at least one protruding tooth, being engaged into the screw thread with the male and female parts being inserted into each other. 
   Such a connecting system is generally known. In practice, a metal part is used on the one hand, and on the other hand, a synthetic part having such a shape that the synthetic part or at least parts thereof can be elastically or plastically distorted. So-called nail plugs are well known, being made of a synthetic sheath-shaped part in which inwardly protruding edges are formed, and a nail or dowel part partially provided with a screw thread. After sticking the nail part into the sheath, the nail part may be unscrewed again. However, the sheath is not to be used again since it has suffered from permanent damages. When sticking the nail part, quite strong forces are applied. 
   BRIEF SUMMARY OF THE INVENTION 
   The aim of the present invention is to provide a system of the type as described in the opening paragraph, so overcoming the above-mentioned disadvantages. 
   This object is reached according to the invention in that the longitudinal direction of the connecting element comprises a rod on which protruding teeth are provided, in such a way that, when the male and female parts are being pressed into each other, the teeth can be pressed through an elastic distortion on the screw thread and that the tooth shape and the screw thread are chosen in such a way that an axial movement in the opposite direction is prevented. 
   Using the teeth makes it possible to make the female and the male parts engaged into one another so that at least one tooth is always active in the connection. The mutual distance between the teeth is generally chosen so that, for example, when axially pressed together for every ⅓ of the pitch, at least one tooth is active. When distorting elastically the teeth upon the connection, the teeth are not damaged and can be used repeatedly. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features and advantages of the invention will become evident from the following description referring to the accompanying drawings in which: 
       FIG. 1  is a side view, partially in section of a connecting element according to the invention, 
       FIG. 2  is a section along line II—II in  FIG. 1 , 
       FIG. 3  is a section along line III—III in  FIG. 1 , 
       FIG. 4  is a section of a connection by means of the connecting element according to  FIG. 1 , 
       FIG. 5  is a diagrammatic section showing two parts connected through an element according to  FIG. 1 , 
       FIG. 6  is a side view, partially in section of a modified embodiment of a connecting element according to the invention, 
       FIG. 7  is a side view, partially in section of a third modified embodiment of a connecting element according to the invention, 
       FIG. 8  is a top view showing some teeth of the connecting element according to  FIG. 7 , 
       FIG. 9  is a section along line IX—IX in  FIG. 8 , 
       FIG. 10  is a section along line X—X in  FIG. 7 , and 
       FIG. 11  is a diagrammatic illustration, partially in section of a fourth embodiment of the invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a connecting element  1  according to the invention, comprising a female part  2 , a rod  3 , the length of which may vary, and a male part  4 . 
   The female part  2  comprises a cylindrical portion  14  that is provided, near one end, with a ring-shaped flange  5 . The cylindrical portion  14  is provided with a bore  6  being inwardly provided with a screw thread. In the illustrated embodiment, the bore  6  is provided with an appropriate screw thread with a determined pitch. The screw thread is preferably of a type being also convenient for use in combination with parts having a standard screw thread. The other end of the cylindrical portion  14  is conical and forms thereby a passage and a connection towards the rod  3 . 
   In the embodiment shown in  FIG. 2 , the rod  3  has a cross-shaped section, but the rod  3  may obviously have different shapes. The most important is that the rod  3  should form a spacer between the male part  4  and the female part  2  and should therefore be sufficiently rigid in order to be able to transfer the desired forces. 
   The other end of the rod  3  is connected with the male part  4  which, in the illustrated embodiment, is made of a rod  8  provided with a number of teeth  9  disposed along its axial length so as to define multiple levels of teeth  9  in the axial direction of the rod  8 . The teeth  9  are preferably specially formed with free ends extending in the direction of the female part  2 . 
   In substance the teeth  9  can be shaped as truncated cone-shaped envelopes which each time extend over the whole periphery of the rod  8 . The teeth are however, so to speak, preferably made with cone-shaped envelopes whereby, seen in the periphery direction, a portion of the truncated cone-shaped envelopes is repeatedly cut off at regular distances or, as shown in  FIG. 3 , only two oppositely-disposed teeth remain within each level along the length of rod  8 . 
   In order to be able to press the male part  4  with a small force onto the appropriate screw thread in the female part  2 , the teeth  9  are elastically distorted and should therefore have a low wall thickness  7 , which is at the cost of the authorized connecting force. When loaded, the teeth  9  are prone to bend out, but due to the tooth shape shown in  FIG. 4 , bending out is recovered at  12  by the lower tooth whereby the authorised bending force becomes approximately four times greater. In order to prevent the rod  8  from bending, if a tooth  9  of a given level is active, the opposite tooth  9  is also active to provide at least two active teeth  9  within that level as shown in  FIG. 4 . 
     FIG. 5  shows how by means of connecting elements  1 , in which the male part  4  has truncated cone-shaped envelopes, different parts of a construction, for instance building elements as disclosed in the Patent Application WO-A-98 48 126, can be connected together.  FIG. 5  schematically illustrates two parts  20  and  21 , wherein part  20  is provided with at least two continuous bores  22  and  23  and part  21  is provided with a continuous bore  24 . The bores  22 ,  23  and  24 , near the end illustrated in  FIG. 2  as above, are provided with a part  25 ,  26 , and  27  with a larger diameter in which the flange  5  of a connecting element  1  can be incorporated that can thereby lie against thus formed edges  28 ,  29  and  30 . The diameter of bores  22 ,  23  and  24  is mainly equal to the inner diameter of the female part  2  so that it can be slid inside with a small spacing. 
   In order to connect part  21  with part  20 , it should be proceeded as follows. Suppose that a connecting element  1  is mounted in the bore  22  wherein the other end of the male part  4  is anchored in any way, either on a (not shown) construction part or on a foundation. 
   The part  21  is put on the part  20  in such a way that the bore  24  lies in the extension of the bore  22 . In the illustrated embodiment, parts  21  and  22  are provided with projections  31  and  32  which fit into the parts  25 ,  26  and  27  with a larger diameter. This facilitates the positioning of parts  21  and  22  relative to one another, but is not necessary. 
   After the part  21  is thus mounted on part  20 , a connecting element  1  is pushed through the bore  24  until the male part  4  thereof lies on the female part  2  of the connecting element  1  belonging to the part  20 . 
   The male part  4  is subsequently slightly pressed into the female part  2 , which leads to a temporary elastic distortion of the teeth  9 , until the flange  5  of the connecting element  1  belonging to the part  21  lies against the edge  30 . Applying the necessary light force is done by hand. 
     FIG. 4  shows that, when using a number of independent teeth  9  on the male part  4 , it is possible to position the connecting element  1  very accurately in axial direction. When for example two teeth  9  per level are provided as shown in  FIGS. 3 and 4 , it is possible to shift the anchorage at 6 levels each time over a distance with a third pitch when further pushing the one connecting element in the other connecting element. If desired, the connection can be further enhanced by screwing the male part  4  further inside the female part  2 . 
   It is possible at any time to release the connection between two connecting elements  1 . This can be done by unscrewing, as in a common bolt and nut connection. The flange  5  may be therefor provided with a groove for a screw driver, or as illustrated in  FIG. 1 , with two openings  10  allowing to shift the element with the help of a special tool or with a screw driver being engaged onto/into the lower part of the bore  6 . 
     FIG. 6  shows a modified embodiment of a connecting element  41  according to the invention, with a construction part  40  which can essentially be equal to the construction parts  20  and  21  shown in  FIG. 5 . 
   The connecting element  41  also comprises a male part  42  and a female part  43 . The male part  42  comprises a bushing  44 A provided with an external screw thread ending with a flange  44 B having the same function as the flange  5  of the connecting element  1 . On the other side of the flange  44 B, two strips  45  extend, which are provided, near their free end, with an inwardly oriented edge  46  which, as shown in section in  FIG. 6 , has the shape of a saw tooth. The teeth  46  may be made as parts of a circle in order to fit better with the screw thread of the male part  42 . 
   It is obvious that when pushing the strips  45  with a slight force elastically outside, the male part  42  can be pressed into the female part  43  like the connecting element  1  in  FIG. 1 . The number of strips  45  should not necessarily be limited to two, but can be any desired number. 
   A modified embodiment of a connecting element according to the invention is shown in  FIG. 7  wherein the male part can be a standard screw thread  47  in a connection comprising two elements  48  and  49 , wherein the female part  50  is housed in the element  49 . The female part  50  is made of a specially formed right strip  51  with, at regular distances, teeth  52  as globally shown in  FIG. 8  with a section along IX—IX as shown in  FIG. 9 . 
   When spirally winding this strip  51  as a screw and optionally linking it, for example, with glue, the female part  50  in  FIG. 7  is created in which the teeth may be engaged into the screw thread of bolt  47  according to the description of  FIGS. 1 and 4 . Therefore, when the elements  48  and  49  are loaded, each tooth  52  engaged with the screw thread of the bolt  47  is prone to bending out, but is supported by its immediately adjacent tooth  52 , which is not engaged with the screw thread of the bolt  47  as shown in  FIG. 7 . The section of the spiral-shaped female part  50  is illustrated in  FIG. 10 , which is a view taken along X—X in  FIG. 7 . The strip  51  can also be provided opposite the teeth  52  with a screw thread shaped tooth (not shown) so that the female part can be screwed in a bore with a corresponding screw thread. Instead of a single tooth, multiple individual teeth  54  may also be provided which are shown in dashes in  FIG. 10 , and which can be fixed in a bore, provided or not with grooves. The screw thread  47  may be a part of a screw bolt to-connect two elements, but may also be some sort of an eye bolt in which an eccentric  56  is inserted through the eye  55 , which eccentric is rotatable in a yoke  58  and can be locked with a screw  57  so that, when rotating the eccentric  56  with a box spanner, the connection between the elements  48  and  49  may be secured after the eye bolt has been stuck into the female part  50  and thereby creates an “out of sight” connection. 
     FIG. 11  shows an alternative for an “out of sight” connection, wherein a thread end  59  is rotated into an element  60  and, when connecting with an element  61 , pressed into a female part  62  shown as comprising an elastic metal bushing with inserted teeth  63  which are able to grab into the screw thread of the thread end  59 . As shown in  FIG. 11 , the female part  62  can be secured to the element  61  by inserting a key  64  into the female part  62  through a keyway in the element  61 .