Abstract:
The invention constitutes of a system for detachable joining of beams with square and/or rectangular cross-section. The system comprises for respective beams, two or more fixing plates mounted in pairs on opposite sides of the beam and fixed along the beam by a friction joint maintained by tightening bolts. Respective fixing plate comprises a first surface the extension of which in at least one direction corresponds to a multiple of a beam width and a second surface turned away from the beam. The system is characterised in that two or more beams are arranged to be joined in perpendicular and/or parrallel directions by at least two opposite each other arranged fixing plates. These fixing plates are arranged to bear on each other along respective second surface. The mutual positions of the fixing plates are fixed by locking elements in through recesses in the each other facing second sides of the fixing plates. These locking elements also constitute anchoring of the tightening bolts.

Description:
TECHNICAL FIELD  
       [0001]     The invention relates to a system for detachable joining of beams with square or rectangular cross-sections in accordance with the preamble of claim  1 .  
       STATE OF THE ART  
       [0002]     Steel beams with square or rectangular cross-sections are common construction elements in high performance static frameworks. In the automotive industry, such beams are used in the foundations of special machines for metal cutting. In the aerospace industry applications are found in jigs for assembling fuselage and wing sections of airplanes. In the processing industry such steel beams are used to support vessels and pipes in specific positions.  
         [0003]     Advantageous for said kind of steel beams is: 
        1. high strength and stiffness relative to their weight     2. smooth surfaces facilitating cleaning.     3. availability on the market in a great number of sizes.     4. relatively low prices.        
 
         [0008]     Disadvantageous for this kind of steel beams is that joints of the beams into frameworks have, until now, not been possible to make with strength values comparable to the capability of the beams, when used in applications where claims also are put on good possibilities of reconstruction and adjustment. It is then a requirement that the fixing devices comply with a combination of properties implying that: 
        1. they reach a strength comparable with the beams to be joined     2. they are detachable.     3. they are adjustable.     4. they are able to join beams of significantly different dimensions     5. they allow different perpendicular or parallel mounting positions     6. they are preferably available in the shape of cheap standard components in stock        
 
         [0015]     At present, welded joints is the most common type of joints for tubular steel beams. They are of high strength and could be made at relatively low cost. However, they are not detachable and therefore they don&#39;t comply with the requirements for reconstruction. Bolt joints are also common and provide joints of high strength as well. The can be made with bolts through holes in the sides of the beams or through holes in flanges welded to the sides of the beams. The possibility of reconstruction will, however, be heavily restricted by that as a rule new holes have to be drilled for every new mounting position. Thus they don&#39;t comply with the requirements for reconstruction.  
         [0016]     Friction joints, the field of the present invention, principally result in good possibilities of reconstruction and adjustment. Several successful construction kits for aluminium profiles utilizes friction joints to assemble the parts, which is illustrated in US2001/0025406A1.  
         [0017]     In these profiles fixing devices in the shape of for instance anchoring nuts with fastening elements are engaging grooves extending in the longitudinal direction of the profile. The fixing devices can be displaced into optional positions leading to good possibility of reconstruction.  
         [0018]     However, the types of friction joints having been developed for joining aluminium profiles cannot be used with steel profiles having square or rectangular cross-section. These profiles are missing the longitudinal grooves where fixing devices can engage. As an alternative for the steel profiles in question friction joints have sometimes been designed with encircling devices that apply force across the cross-section of the beams and thereby create the required friction forces.  
         [0019]     Such wholly or partially encircling fixing devices are in some cases formed like yokes that keep steel beams pressed against each other by means of tightening bolts. They are also applied by means of common clamps pressing beams against each other and thereby keeping them interlocked by friction.  
         [0020]     The problem with the aforementioned fixing devices is that in the present shape they have large dimensions relative their strength. Therefore in most cases one hasn&#39;t been able to provide them with strength values equal to the beams. It hasn&#39;t either been possible to give them a general shape to correspond to the demands for variation in applications where possibilities of reconstruction are required. The requirement of connecting a large number of beams of varying dimensions in different mounting positions with a reasonable number of different fixing devices has not been met. For the same reasons keeping prefabricated fixing for this purpose devices in stock hasn&#39;t been possible.  
       DESCRIPTION OF THE INVENTION  
       [0021]     An object with the invention is to solve the problems existing in known solutions for detachable joining of steel beams. This is carried out by a system according to claim  1 .  
         [0022]     The present invention relates to a modular fixing system for joining steel beams of square or rectangular cross-section for frameworks for supporting functions in machines and other industrial equipment.  
         [0023]     Through a combination of locking by friction and locking by shape the fixing system provides a possibility to achieve the strength values corresponding to the requirements in demanding industrial applications. At the same time it gives possibility to detach the joints so that the frameworks can be reconstructed into new structures and also be adjusted to an increased accuracy. Beams of different dimensions and different perpendicular mounting positions can thanks to the modular design according to the thought of the invention be joined into extensive variations of structures for frameworks. By this modular design a reasonable number of different components required in the system can be achieved. In turn this results in that the parts of the fixing system can be manufactured as standard products, whereby the manufacturing cost will be reduced and storing facilitated. The parts can even be stored whereby access for use is achieved at short notice.  
         [0024]     The invention is composed of a system of fixing devices for joining beams into frameworks of variable structures for industrial applications. The beams consist of square or rectangular profiles of steel with edge lengths being multiples of a certain module length.  
         [0025]     The fixing devices comprises specifically designed fixing plates whose main dimensions constitutes multiples of half the module length. They are mounted in pairs on opposite sides of the beams and are tightened by bolts. The thrust in the bolts provides holding friction forces on the contacting surfaces between the fixing plates and the beams. The holding is further strengthened by stop screws or wedge devices extending from protruding edges or shoulders at the fixing plates and provide a shape determined locking of the beams. Joining locations for beams in frameworks are created by fixing plates at respective beam are put into contact with each other and locked in perpendicular or parallel positions by means of locking elements in the neutral plane between the contacting fixing plates. These locking elements are made of internal threaded sleeves fitting recesses in the fixing plates. At the same time the sleeves provide anchoring of the bolts that tightens the fixing plates to the respective beam.  
         [0026]     The invention enables frameworks of high quality to be constructed in variable embodiments by means of a small number of fixing elements of different sizes. They will thereby be of low cost and quickly available for use. 
     
    
     SHORT DESCRIPTION OF THE FIGURES  
       [0027]      FIG. 1  shows in a perspective view an embodiment of a fixing device in the system according to the invention  
         [0028]      FIG. 2  shows the same fixing device in cross-section  
         [0029]      FIG. 3  shows in a perspective view different embodiments of locking devices  
         [0030]      FIG. 4  shows in a perspective view a first embodiment of a fixing plate  
         [0031]      FIG. 5  shows in a perspective view fixing plates mounted opposite each other  
         [0032]      FIG. 6  shows in a perspective view two beams joined with the system according to the invention  
         [0033]      FIG. 7  shows in a perspective view three beams joined with the system according to the invention  
         [0034]      FIG. 8  shows in a perspective view a framework according to the invention  
         [0035]      FIG. 9  shows alternative embodiments of locking elements  
         [0036]      FIG. 10  shows an alternative of a locking element  
         [0037]      FIG. 11  shows in a perspective view a second embodiment of a fixing plate  
         [0038]      FIG. 12  shows a second embodiment of locking the fixing plate to the beam  
         [0039]      FIG. 13  shows in a top view the second embodiment 
     
    
     DESCRIPTION OF EMBODIMENTS  
       [0040]     The design of the invention and further advantages are described more in detail below in connection with the  FIGS. 1-13 .  
         [0041]      FIG. 1  illustrates a recommended embodiment of a fixing device in the system according to the invention. Four fixing plates  1  of different kinds are in pairs holding two crossing beams  2 , fixed between them by means of tightening bolts  3  and  9 . From the sides of the fixing plate longitudinal strips  4  extend in the main directions of the beams.  
         [0042]      FIG. 2  illustrates the same montage of the fixing device seen in cross-section. The thrust in the bolts  3  and  9  causes fastening friction forces in the contact surfaces  21  between the fixing plates and the beams. The resistance against side movements is strengthened by stop screws  5 , according to a recommended design, extends from de longitudinal strips  4  and provide a shape determined locking of the beams. The stop screws are also used to temporarily keep the fixing plates  1  in position during the mounting. The stop screws  5  are also used to adjust the side position of the fixing plates with respect to the beams.  
         [0043]      FIG. 2  further shows how the fixing plates  1 , on each side of the beams, can be tightened according to two alternatives. The primary alternative is shown to the left in  FIG. 2 . In this case the tightening bolts  3  engage the threaded sleeves  6  that are common to the two beams  2  and are located at the surfaces  30  opposite to each other of the two adjacent fixing plates. These sleeves  6 , shown enlarged in detail B of  FIG. 2 , have internal threads  8  fitting with the bolts  3 . The sleeves  6  fits into recesses  10  in the fixing plates and cause that both the adjacent fixing plates  1  shape determined are kept fixed against side movements with respect to each other along the parting line  7 .  
         [0044]     The secondary alternative for tightening the fixing plates towards each other is illustrated to the right in  FIG. 2 . In this case longer tightening bolts  9  are used, which extends through the whole joint and tighten it. These bolts are anchored in threaded sleeves  12 , which are shown enlarged in Detail C in  FIG. 2  and, which similar to the sleeves  6 , fit into the recesses  10  in the fixing plate. In the recesses  10  in the surfaces  30  opposite to each other in the adjacent fixing plates  1  sleeves  13  are used that similar to the sleeves  6  fits into the recesses  10  but have clearance holes  22  without any thread. These sleeves  13  thereby hold both fixing plates  1  shape determined fixed against side movements along the parting line  7 .  
         [0045]     Through the secondary joining alternative mounting of beam joints on locations accessible from only one direction is enabled. It also enables that by means of further lengthened bolts joint corners with three or more joined beams can be constructed.  
         [0046]      FIG. 3  illustrates, more in detail how the sleeves  6 ,  12  and  13  according to the recommended alternative are designed. They have a cylindrical outer surface  11  and a longitudinal slot  17  to absorb the minor differences in positions and diameters that can exist between the sleeves and their connecting recesses in the fixing plates. The sleeves can of course be designed without a longitudinal slot, which then requires higher accuracy in manufacturing the parts but instead lead to improved stiffness and strength in the joint.  
         [0047]     The length of the sleeves  6  and  13  are in the recommended design somewhat shorter than the added up depths of the recesses  10 , where they are located. A minor axial play  20  is thus created at the end surfaces  31  of the sleeves  6  and  13  with respect to the bottom surface  32  of the recesses  10 . The resisting force to the tightening force in the bolts  3  or  9  will thus in the recommended embodiment of the invention not pass through the sleeves  6  and  13 . Instead it passes over the outer surfaces  30  of the adjacent fixing plates and makes these surfaces contacting each other in the parting plane  7 . Thereby the position of the beams  2  with respect to their mutual distance is determined by the thickness of the fixing plates. Friction forces are created between the two outer surfaces  30 , which contribute to the strength of the joint.  
         [0048]     The components of the fixing system are comprised in a superior modular system that increases the possibilities of combinations and reduces the number of varieties of components in the system. This modular system has a common module length m, which in practice can be an even dimension, for instance 50 mm. The width of the beams and a height should be multiples of the chosen module length m and can then be expressed as m*B respective m*H.  
         [0049]      FIG. 4  shows the nominal dimensions for a fixing plate being designed in accordance with the rules of the modular system. The width of the plate is m*(B+1) and its length is likewise a multiple of L of the module length, i.e. it has the length m*L. It is evident that the holes for the joining bolts  3  or  9  lies with a distance that in breadth can be expressed with the formula m*(B+1)−2*G, where G is the distance from the centre of the holes to the edge of the plate. The distance between the holes in the longitudinal direction can in a corresponding way be expressed with m*L−2*G.  
         [0050]     From  FIG. 4  is also evident that the nominal material thickness of the plate is m*0.5 and that the distance between the two strips  4  is m*B+T. The distance T is a small play enabling that fixing plates can be mounted at the beams even when these have certain over-dimensions with respect to the nominal dimensions. The play T also enables certain minor sideward position displacements of the fixing plates by means of the stop screws  5 .  
         [0051]      FIG. 5  shows how to combine two crossed beam sizes, the one with the width m*B and the other with the width m*B′. This is enabled by that the length of the first plate, which according to the module system can be written m*L, is chosen to fit with the width of the other plate, i.e. m*(B′+1). In the same way the length of the other plate is chosen, which can be written m*L′ to the width of the first plate m*B(B+1). The distance between the holes in the length direction for the first plate can then be expressed with the formula m*(B′+1)−2*G, which is the same formula that gives the distance between holes in breadth for the other plate. With the principle of the modular system the two contacting plates thus get coincident (coaxial) hole positions to enable fixing plates from the series of dimensions in the modular system to crate crossing points, where de tightening bolts  3 ,  9  and accompanying guiding sleeves have a common hole pattern determined by the module. Thereby the number of variants of fixing elements is reduced compared to what had been required without module determined series of dimensions and without the described uniform rule for the hole pattern and the dimensions of the fixing plates.  
         [0052]      FIG. 6  illustrates how the fixing plates according to the modular system can be located so that beams are held in parallel positions at a distance of one module and how fixing plates of larger sizes can be combined to join the beams in another main direction. Through these different ways of mounting the combinations can be extended without increasing the number of components in the modular fixing system.  
         [0053]      FIG. 7  shows how more small beams according to the dimension series, when necessary can be put close to each other to provide increased stiffness and strength.  
         [0054]      FIG. 8  shows in an overview further examples of how the fixing system can be used to combine beams of different sizes according to the rules of the modular system for frameworks according to specific needs.  
         [0055]      FIG. 9  illustrates a variant of the modular fixing system where the sleeves in  FIG. 3, 6 ,  12  and  13  are provided with a somewhat conical outer surface  14 ,  15  and  16 . This conical shape is of interest to simplify detachment of mounted joints. Connecting recesses  10  in the fixing plates should then be conical too.  
         [0056]      FIG. 10  illustrates an alternative embodiment of the modular fixing system that is obtained when the sleeves  6  and  13  are designed to not only keep the fixing plates located opposite to each other fixed against mutual side movements along the parting line  7 , but also keep their positions fixed perpendicular to this parting line. An embodiment according to this alternative is shown to the left in  FIG. 10 . The cylindrical sleeves  6  and  13  are here made so much longer that the axial play  20  is eliminated. At the same time the thickness of the material in the fixing plates is made smaller. A contact between end surfaces  31  at the sleeves  6 ,  13  and the bottom surfaces  32  in the recesses  10  then arises. At the same time a play arises between surfaces  30  on the adjacent fixing plates at the parting line  7 . This design has advantages in those cases when for strength reasons a smaller material thickness of the plates can be accepted and at the same time, for cost reasons, the requirements of flatness of the outer surfaces  30  of the plates along the parting line  7  can be reduced.  
         [0057]     Another design of the sleeves  6  and  13  that by the sleeves themselves gives a certain distance between the adjacent fixing plates is illustrated to the left in  FIG. 10 . Here the sleeves are provided with a central brim  22  with oppositely directed shoulders  23 , which acts against machined land surfaces  24  on the fixing plates  1 . This embodiment could have advantages from the manufacturing point of view.  
         [0058]      FIG. 11  shows a variant  25  of the fixing plate  1 , which instead of longitudinal strings  4  has corner projections  26  with a corresponding function. This embodiment enables each non square fixing plate according to the modular system to be used for two different beam sizes.  
         [0059]     The number of different fixing plates for covering of the size alternatives in crossing points for beams will thereby be further reduced.  
         [0060]     However, the space available for mounting stop screws for shape determined fixing at side forces of the kind described in connection with  FIG. 2  would be smaller. Stop screws  5 , essentially for fixation during mounting of the joint can as well be placed as illustrated at the projections  26  in  FIG. 11 .  
         [0061]      FIGS. 12 and 13  illustrates an alternative to the stop screws  5  in the form of wedges  27  that are pressed down against chamfered surfaces  28  at the corner projections  26  or, in a similar manner at the strings  4  illustrated in  FIG. 1 . These wedges can be knocked or pressed to a suitable depth by means of specific tools and can also be detached with specific tools. Within the scope of the invention there is a possibility to press down the wedges from other directions than the one illustrated in  FIG. 12 , which in certain cases has advantages from the accessibility point of view.