Abstract:
Tubular structure having at least two tubes ( 20, 20′ ) and a plug-in tube connection ( 10 ) which comprises a flange ( 1 ), wherein said flange ( 1 ) serves as an axial stop surface for terminal ends ( 21, 21′ ) of the two tubes ( 20, 20′ ). Each side of the flange ( 1 ) is equipped with at least one lug ( 3 ) in order to engage in a corresponding cutout ( 22 ) in the terminal end ( 21, 21′ ) of the respective tube ( 20, 20′ ), wherein the lugs ( 3 ) engaging in the cutouts ( 22 ) prevent the tubes ( 20, 20′ ) from twisting relative to one another. On each side of the flange ( 1 ) is provided a cylinder portion ( 5, 5′ ) which can be plugged into the inside of the respective tube ( 20, 20′ ). In addition, each cylinder portion ( 5 ) has an axial gap ( 7 ), resulting in flexible endpieces ( 9 A,  9 B) above and below the gap. The first flexible endpiece ( 9 A) has a radial bore ( 11 ) with a screw element ( 13 ) for tightly clamping the tube connection ( 10 ) in the tube ( 20, 20′ ).

Description:
[0001]    The present invention relates to a tube connection for connecting different tubes, in order to form a self-supporting tubular structure, such as a tent structure, stand building structure for example. 
         [0002]    In the field of tent structures and tubular structures within stand building, there are various methods for connecting the tubes of these structures. The simplest of these methods is to insert an end of a tube with a smaller diameter in the corresponding end with a larger diameter of a next tube. However, this method has various limitations as regards the profile of the end of the tubes and can not simultaneously guarantee a solid connection and a simple, easy disassembly. In addition, if the tubes are flexible, such a connection is not reliable because the tubes can become loose. 
         [0003]    Other tube connections are also known which are inserted between two tubes and keep the two tubes together by friction. It is a disadvantage of these usually elongated connections that they also can not guarantee a reliable and stable connection and, above all, that they can not prevent the tubes twisting against each other “shear effect”. 
         [0004]    The object of the present invention is therefore to provide a tube connection for a tube-like structure which allows a very solid, secure but still easy connection of tubes and can also prevent twisting of the tubes against each other. 
         [0005]    This object is solved according to the invention through a cylindrical tube connection, comprising a circumferential flange which acts as an axial stop surface for terminal ends of two tubes and on each side at least one step engaging in a corresponding cutout on the terminal end of the tube to prevent twisting of the tubes against each other. The strength of the connection is guaranteed in that flexible end pieces are provided, which result from gaps provided in the terminal ends of the end pieces. The end pieces each include a radial bore which each receive a screw element. To clamp the tube connection in the interior of the tubes, these screw elements can be screwed through openings in the cylindrical surface of the tube, in order to bend the flexible end pieces apart. The screw elements can also be screwed out a little to attach the tube connection in the cylinder wall. 
         [0006]    The main advantage of the invention is that the tube connection can be employed very easily and quickly, and that the connection between the tubes themselves and with the tube connection is still very firm and reliable. Additionally, the tube connection can be easily pulled out from inside the tubes, after the screw element has been screwed in or screwed out. 
         [0007]    Another advantage of the invention is the large number of different possible applications where the tube connection may be used. Furthermore, the inventive tube connection can be made in very different sizes and from different materials. For example, if the tubes, which the tube connection is to connect, are flexible and if the whole structure should be flexible, then one can manufacture the tube connection of flexible plastics. This way one can guarantee the flexibility of the entire structure. On the other hand, in very stable structures, such as stages or similar structures and scaffolding, the tube connections are preferably made of metal or fibre reinforced plastic. 
     
    
     
         [0008]    Further details and advantages of the invention are described below with reference to embodiments and with reference to the drawing. They show: 
           [0009]      FIG. 1  a schematic perspective view of the tube connection according to the invention; 
           [0010]      FIG. 2  a schematic side view of the tube connection according to the invention; 
           [0011]      FIG. 3  a schematic perspective view which illustrates how the tube connection connects two tubes, according to the invention; 
           [0012]      FIG. 4  a schematic perspective view for illustrating a possible use of a multitude of tube connections according to the invention; 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The invention relates to a tube connection  10  for the simple, fast and secure connection of tubes  20 ,  20 ′, rods or of generally elongated hollow construction elements. For simplicity, the tubes, rods or generally elongated hollow construction elements shall be referenced in the following with tubes  20 ,  20 ′. The invention is particularly suitable for the connection of two hollow tent tubes of larger tents, wherein a multitude of tubes  20 ,  20 ′ are connected with several tube connections, in order to build a self-sustaining construction  30  (see for example  FIG. 4 ). According to the invention it relates to one-piece elements (preferably plastic or metal elements) which act as tube connections  10 . 
         [0014]    The object of the invention is a tubular structure  30  with at least two tubes  20 ,  20 ′ and an elongated three-dimensional cylindrical element, the tube connection  10 , which is insertable into the inside of a tube  20 ,  20 ′. The tube connection  10  connects two tubes  20 ,  20 ′, in that one inserts it between two tubes  20 ,  20 ′ into the inside of the terminal ends of the tubes  21 ,  21 ′ and then, by means of methods described in following paragraphs, securing the tube connection in the inside of the terminal ends  21 ,  21 ′. 
         [0015]      FIG. 1  shows the preferred embodiment of the tube connection. As  FIG. 1  shows, the tube connection  10  comprises in a middle section a circumferential flange  1 . This flange  1  has preferably a height (d 1 −d 2 )/2 which is approximately identical with the thickness of the cylinder wall  26  (the wall thickness of the tube  20  or  20 ′), i.e. the diameter d 2  is approximately the outer diameter of the tubes  20 ,  20 ′. This is preferred in order to make a seamless transition between the tubes  20  and  20 ′ possible. In case the two tubes  20  and  20 ′ to be connected have different diameters, a further embodiment of the tube connection is used, which is not symmetrical, i.e. it comprises two cylinder portions  5 ,  5 ′ which have different diameters d 2 . In this case, the central circumferential flange  1  is conical and the diameter on the first side of the flange  1  corresponds to the diameter of the first tube  20  and the diameter on the other side of the flange  1  corresponds to the diameter of the second tube  20 ′. In this case the tube connection  10  can also be used as a transition element between two different tubes  20 ,  20 ′. 
         [0016]    The flange also acts as an axial stop surface for the terminal ends  21 ,  21 ′ of the tubes  20 ,  20 ′, i.e. the sides of the flanges should be adapted precisely to the terminal ends  21 ,  21 ′. In the preferred embodiment of the tube connection  10 , at least one, but preferably two, lugs  3  are provided on each side of the flange  3 . These lugs  3  are directly connected with the flange  1  and preferably have the same height as the flange  1 . These lugs  3  are constructed so that they engage in a corresponding cutout  22  on the terminal end  21 ,  21 ′ of the respective tube  20 ,  20 ′. This particular feature is very important because it solves one of the objectives of the invention. With these lugs  3  engaging in the cutouts  22 , a twisting of the tubes  20 ,  20 ′ against each other is prevented. The lugs  3  are axial extensions of the expansions of the flange  1  which engage in the corresponding cutouts  22 . If these lugs  3  are sufficiently long and firm and they can not move within the cutout  22 , then a twisting of the tube  20 ,  20 ′ against the tube connection itself is also not possible. 
         [0017]    In the most common embodiment of the invention, as  FIG. 1  shows, the tube connection  10  is constructed symmetrical to the circumferential flange  1 , i.e. the tube connection  10  has a cylinder portion  5 ,  5 ′ on each side of the flange  1 . These cylinder portions  5 .  5 ′ are insertable in the inside of the respective tubes  20  and  20 ′, i.e. the diameter d 2  of the cylinder portions  5 ,  5 ′ approximately corresponds with the inner diameter of the tubes  20 ,  20 ′. In order to be able to easily insert the cylinder portions  5 ,  5 ′ into the inside of the tubes  20 ,  20 ′, the diameter d 2  is a little smaller than the inner diameter of the tubes  20 ,  20 ′. 
         [0018]    In the case when the two tubes  20  and  20 ′ to be connected have different inner diameters, the two cylinder portions  5 ,  5 ′ are not symmetrical, i.e. they also have different diameters d 2 , so that each cylinder portion  5 ,  5 ′ fits into the corresponding tube  20 ,  20 ′. 
         [0019]    In order to achieve a firm connection between the tubes  20 ,  20 ′, it is preferred that the length l 1  equates to at least twice the diameter d 2 . The longer the cylinder portion  5 ,  5 ′ is, the smaller the possibility that the cylinder portion  5 ,  5 ′ of the tube connection  10  bends/moves in the tube  20 ,  20 ′. 
         [0020]    Each cylinder portion  5 ,  5 ′ features an axial gap  7 , which extends from a face surface of the cylinder portions  5 ,  5 ′ in the direction of a middle section. The role of this gap  7  is to provide a first flexible endpiece  9 A and a second flexible endpiece  9 B above and below the gap  7 . 
         [0021]    The first flexible endpiece  9 A is provided with a radial bore  11 . Through this radial bore  11 , a screw element  13  can be screwed in. For clamping the tube connection  10  in tube  20  or  20 ′ there are two different possibilities:
   a) in the preferred embodiment of the invention, the screw element  13  is screwed in so deep in the radial bore that it presses against the surface  16  of the second flexible endpiece  9 B. This pressure then bends the endpieces  9 A and  9 B apart, and thus the effective second diameter d 2  grows. When this pressure on the surface  16  of the second flexible endpiece  9 B is sufficiently high and the effective diameter d 2  has been sufficiently increased, then the tube connection  10  is firmly clamped within the inside of the tube  20 ,  20 ′. The rigidity of the material, out of which the tube connection  10  is manufactured from, determines the length l 2  and the height h 1  of the gap  7 . These parameters, the rigidity of the material, the length l 1  and the height h 1 , define the flexibility of the flexible endpieces  9 A,  9 B and therefore the increased second diameter d 1 . The outer surface of the cylinder portions  5 ,  5 ′ and the inner surface of the cylinder walls  26  also play a role in the firmness of the connection. The rougher these surfaces are, the firmer the connection between the tubes  20 ,  20 ′ and the tube connection  10  is.   b) in a further embodiment of the invention, after the cylinder portions  5 ,  5 ′ have been inserted into the inside of the tubes  20 ,  20 ′, the screw element  13  is screwed out in order to fix it in the cylinder wall  26 . In order to enable a firm connection, in this case the opening  24  can be provided with a thread.   
 
         [0024]    As an auxiliary measure, in case the roughness of the inner surface of the cylinder wall  26  is insufficient, the second flexible endpiece  9 B may be fitted with a ridge  19  which clamps into a corresponding dimple of the tube  20  or  20 ′. But this ridge  19  of the endpiece  9 B should not be too high, so as not to prevent the insertion of the cylinder portions  5  or  5 ′ in the inside of the tube  20  or  20 ′, i.e. that d 2  including this ridge  19  is not larger than the inner diameter of the tube  20 ,  20 ′, or if it is larger, then the flexibility of the endpieces  9 A,  9 B must compensate for this diameter difference. 
         [0025]      FIG. 2  shows that, in the preferred embodiment of the invention, the first flexible endpiece  9 A comprises a groove  15  which receives a screw nut  17 . The screw element  13  can be screwed into this screw nut  17 . This supplementary measure is particularly advantageous when the material out of which the tube connection  10  is made of is a soft material which does not allow a firm connection. This screw nut  17  is also required when the tube connection must be reusable, i.e. when the threads may not wear out. 
         [0026]      FIG. 3  shows the use of the tube connection  10 , after it has been inserted into the tubes  20 ,  20 ′. On the left side one can see based on case a) that the screw element  13  has been screwed in, in order to increase the effective diameter d 2  of the cylinder portion. On the right side case b) is shown. The screw element  23  has been screwed out here, in order to fix it within the cylinder wall  26 . 
         [0027]      FIG. 3  also shows how the lugs  3  engage into the corresponding cutouts  22  on the terminal ends  21 ,  21 ′ in the cylinder wall surfaces  26  of the respective tubes  20 ,  20 ′. This feature prevents that the tubes  20 ,  20 ′ twist against each other and gives the entire structure a great stability. 
         [0028]    A particularly advantageous use of the tube connection  10  is shown on  FIG. 4 . This figure shows multiple tubes  20 ,  20 ′ which are connected with multiple tube connections  10  and build a self-supporting load carrying structure  30 . According to the invention, such load carrying structures  30  can be employed to construct tents, parasols, pavilions, exposition stands or to build other constructions with elongated supporting elements, such as stages or scaffolding for example.