WO2012098080A2

WO2012098080A2 - Crossbar member, crossbar and method for manufacturing a crossbar member

Info

Publication number: WO2012098080A2
Application number: PCT/EP2012/050576
Authority: WO
Inventors: Michael Clade
Original assignee: B&K Braun Gmbh
Priority date: 2011-01-18
Filing date: 2012-01-16
Publication date: 2012-07-26
Also published as: WO2012098080A3; DE102011003316A1

Abstract

A crossbar member includes a first chord element (10) and a second chord element (12) and a bracing (14, 15) connected to the first chord element and the second chord element at one connecting point each, wherein the connecting point includes a section (18) of the chord element (10) and a section (19) of the bracing, wherein the section of the chord element comprises a feature (18) integrally formed with the chord element. The section of the chord element may also be connected to the chord element by a press connection. Apart from that, the bracing may be connected to the section of the chord element in a releasable or non-destructive releasable way.

Description

Crossbar member, crossbar and method for manufacturing a crossbar member

Description

The present invention relates to members for crossbars and crossbars as they may, for example, be applied in stage technique or for any other fields in which crossbars are required for mounting loudspeakers, spotlights or other design elements, etc.

Crossbars are used in the setup of scaffoldings mounting lights, loudspeakers and other stage-related means. Crossbar are here used vertically and horizontally in order to produce suitable structures. Such crossbars which are also referred to as modular lattice girders or "truss" consist of elements welded together, like it is, for example, illustrated in Fig. 1 1 , wherein elements are the so called chord tubes 1 , which are connected via bracings, wherein these bracings are designated by 2. Apart from that, each chord tube 1 is typically provided with connector elements 3, 4, wherein at 3 stud-shaped connector elements are illustrated, while at 4 fork-shaped connector elements are illustrated. The connector elements 3 and 4 engage into corresponding complementary connector elements of neighbouring crossbars, so that a crossbar tower may be set up.

The strength or loading capacity of such a crossbar or crossbar construction is limited depending on the support span or spacing. If a higher loading capacity of the supporting construction is required, either the support spacing has to be reduced or the cross-section of the chord tubes has to be increased. The chord tubes 1 here carry the main load and are thus of a great importance with respect to stability on the one hand and geometrical accuracy of the crossbar on the other hand.

Crossbars, as illustrated in Fig. 12, are manufactured by welding the chords 1 to the bracings 2 and the connector elements 3 and 4 so that a compact crossbar results which may be connected to other compact crossbars into a construction.

It is a disadvantage of this concept that by welding individual crossbar elements, for example, chord tube 1, bracings 2, connector elements 3, 4 so called heat influence zones result. The original characteristics of material are changed by heating, typically to the worse, whereby the stability of the individual crossbar is reduced. At the same time, these heat influence zones may in particular cause the chords to somewhat warp. This may not be critical for a single crossbar. If, however, several crossbars warped by welding are connected using the connector elements 3, 4 of Fig. 12, it may well be the case that the error of alignment accumulates and finally problems in the complete construction result due to alignment inaccuracies which may lead to instabilities. In order to prevent such alignment inaccuracies, each crossbar may be aligned or straightened directly after manufacturing. This, however, requires a cost and time consuming procedure and postprocessing which leads to the increase of costs.

In order to increase stability so that disadvantageous effects of heat influence zones may be compensated, stronger profiles may be used, i.e. for example chord tubes with a larger diameter, etc. Apart from additional costs which result, the use of stronger profiles also has the disadvantage that handling during assembly and transport is made more difficult by these crossbars, as the weight of an individual crossbar is increased. Apart from that, also the transport volume is increased. Due to the permanently connected or welded individual elements (chord tube, bracings and connector elements) of a crossbar, the same is implemented as a massive supporting structure and is accordingly bulky and unhandy.

It is thus the object of the present invention to provide an improved crossbar concept.

This object is achieved by a crossbar member according to claim 1 or according to claim 26, a method for manufacturing a crossbar member according to claim 15 or by a crossbar according to claim 17 or claim 18.

The present invention is based on the finding that by preventing the heat influence zones or heat influence zones, i.e. by preventing welds or weld seams, in particular at the chord or belt elements, two substantial disadvantages of the prior art are eliminated. On the one hand, by avoiding weld seams, weakening due to heat influence zones is reduced. On the other hand, by preventing heat influence zones the danger of warping of the chord tubes during welding is eliminated. In order to be able to mount struts or bracings, the chord tubes are provided with features implemented integrally with the chord element. In other words, the material of the feature which may, for example, be a bridge or a groove, is implemented as a material connection with the chord element and not, like with welding, put together from two different parts, wherein the connection is made between the two different parts via a weld seam. According to the invention, the chord elements are manufactured with these features such that these integrally formed features are already manufactured in manufacturing, for example, when pressing or casting or in a different manufacturing of the tube. Thus, due to the mounting features no heat influence zones result. It is apart from that preferred not to weld the bracings with the feature to the chord elements but to screw, bolt or rivet the same or to connect the same by another non- destructive, detachable or releasable connection. Thus, also thermal stress remote from the chord element is prevented and also a stress of the bracings by welding is prevented. Apart from that, an individual crossbar member may be repaired to the effect that a bent chord element may simply be exchanged by detaching the connection with the bracings and exchanging the bent or defect chord or belt element by a straight or intact chord element.

In a further embodiment of the present invention, an integer connection of the section or feature to the chord element is not strictly necessary. Instead, instead of the integer connection also a press or crimp connection may exist. This means, that also with the press connection which is, for example, produced by screws or bolts, either connected directly to the chord element or passing through the chord element and existing in a further connecting element like for example a plain cylinder. Thus, in the section of the chord element boreholes are required. However, the weakening of the chord element by such boreholes is substantially less critical than the weakening by a welding treatment. Apart from that, boreholes may easily be produced without leading to the problem of warping which exists when welding. In one special embodiment, the main chord tube is thus implemented as a normal tube. The section or the feature of the section is implemented as a bridge and this bridge is mounted to a plain cylinder by means of screws or bolts which extend through the boreholes in the chord element such that a press connection is acquired between the chord element and the bridge.

A further embodiment of the present invention relates to a crossbar member having a first chord element and a second chord element as well as a bracing connected to the first chord element and the second chord element at one connecting point each. The connecting point includes a section of the chord element and a section of the bracing. The section of the chord element comprises a feature by which the bracing is detachably connected to the chord element. These detachable connection may, for example, be acquired by a screw, a bolt, a rivet, a pin or another non-destructive detachable coupling. Thus, in this embodiment, the feature may not necessarily be implemented integrally with the chord element but may also be coupled to the chord element in a different way, like for example by a welding connection or a press connection. However, thermal stress onto the complete crossbar member is still at least reduced by the fact that the bracing is not attached to the chord element by welding, i.e. non-detachably, or non-destructively detachably removable, but is attached by a detachable connection, for example a screwed connection.

In the following, preferred embodiments of the present invention are explained in more detail with reference to the accompanying drawings, in which: Fig. 1 shows a basic diagram of a crossbar member according to one embodiment of the present invention;

Fig. 2 shows a perspective view of a foldable crossbar in operating position;

Fig. 3a shows a cross-section of a chord element with a bridge as a connecting feature; Fig. 3b shows a cross-section of a chord element with a groove as a connecting feature; Fig. 4a shows a bracing with a fork head for connecting to the bridge in Fig, 3a; Fig. 4b shows a bracing with a stud head for connecting to the groove in Fig. 3b; Fig. 5 shows an alternative implementation of the bracing as an integrally formed bracing;

Fig. 6 shows a perspective view of the integrally formed bracing;

Fig. 7 shows a chord tube with a connected bracing, connected connector and connected hinged or joint elements;

Fig. 8 shows an illustration of a chord element with a stud-shaped connector element, two mounted bracings and a swivel joint section;

Fig. 9 shows an illustration of a pivot or swivel element screwed to the chord element and of two bracings in an inside position;

Fig. 10 shows an illustration of a cylinder as a mounting member for a swivel joint section for the inside position mounting for Fig. 9; Fig. 1 1 shows an illustration of a swivel joint in its mounted state connected with a screw;

Fig. 12 shows a known welded crossbar;

Fig. 13 shows a cross-section through a main chord tube according to a further embodiment of the present invention;

Fig. 14 shows a perspective view of a bridge according to a further embodiment of the present invention; Fig. 15 shows a perspective view of a plain cylinder with a screwed bridge according to a further embodiment of the present invention; and Fig. 16 shows a perspective view of the screwed bridge construction at the main chord tube of Fig. 13.

Fig. 1 shows a crossbar member with a first chord element 10 and a second chord element 12. The two chord elements 10, 12 are connected to each other by means of a bracing 14 and a further bracing 15. In particular, the connection between the bracing 14 and the chord element 10 or 12 is in a connecting point 17, wherein the connecting point includes a section 18 of the chord element and a section of the bracing, wherein the section 18 of the chord element comprises a feature which is implemented integrally or as a material connection to the first or second chord element. Preferably, the chord element is implemented as a chord tube with a round or angular cross-section, and the feature is a section of the tube which is geometrically different from the tube shape, like, for example, a tongue 18a illustrated in Fig. 3a or a groove 18b illustrated in Fig. 3b. Further features may exist at the chord element, like for example a restricted change of the cross-section, wherein, for example, a round cross-section is changed into a square cross-section so that a bracing provided with a corresponding head may be screwed to the section of the square cross-section while the chord element otherwise is a round tube. Further constrictions or enlargements may also be used as a connection point section of the chord element in order to generate a feature of material connection by which it is enabled to mount the bracings without a weld seam. Particularly advantageous, however, are the implementations illustrated in Fig. 13a and 13b in the form of the bridge 18a of Fig. 3a or the groove 18b in Fig. 3b.

Fig. 2 shows a perspective view of a crossbar which is foldable, consists of all in all four crossbar members of Fig. 1 and is shown in its operating position, without stabilization, however. In particular, Fig. 2 is a modular single crossbar having four individual crossbar members or side sections which are implemented with the bracings as a framework, which are each screwed or riveted to the main chord tube. Each side section consists of two chord elements between which the bracings extend. The main chords of neighbouring side sections are provided with joints (for folding) and thus form a so-called double chord tube. In particular, the crossbar member of Fig. 1 may form the front upstanding side part with chord elements 10, 12. The chord elements 10, 12 are connected to each other via the bracings 14, 15 and further bracings 21. The bracings 21 , 14, 15 are each connected to the two chord elements, 10, 12, as illustrated in Fig. 2, via the connecting points 17, wherein each connecting point comprises one respective feature 18 (of Fig. 1). Apart from this, each chord element in Fig. 2 each comprises a mortise joint 23 for a chord element of another crossbar and a fork connector 24 at the other end of the chord element. Apart from this, a further crossbar member is provided with the chord elements 20, 22, which may be set up just as the crossbar member with the chord elements 10, 12. However, the framework implementation as it is illustrated in Fig. 2 may also be implemented alternatively. In particular, the second crossbar member with the chord elements 20, 22 is connected to the first crossbar member with the chord elements 10, 12 via respective swivel joints 26. This way, in the embodiment illustrated in Fig. 2, four individual crossbar members each are connected to each other and neighbouring chord tubes, like for example the chord tubes 12, 20 then form the double chord tube having an increased stability as compared to a single chord crossbar, as it is illustrated in Fig. 12.

Apart from that, the crossbar in Fig. 2 may be folded by releasing or loosening the individual swivel joints 26. Alternatively, however, also side parts like, for example, the side part 20, 22 may be removed by releasing the swivel joints, so that the chord elements 27 of the back crossbar member consisting of the chord elements 27 and 28 is screwed directly to the tube 12 via the swivel joints so that a triangular crossbar results. This flexible connectability is enabled by the special asymmetric implementation of the swivel joints explained with reference to Figs. 7 to 1 1. This implementation of the swivel joints also enables any design of further geometries apart from the three-point-crossbar or a four- point-crossbar. If the chord element 20 is detached from the chord element 12 by unscrewing the swivel joints 26, and if a further crossbar part is used, thus a five-point- crossbar having five side parts results. Thus, any geometries may be formed for crossbars by any combinations of the individual crossbar members.

By the use of double chord tubes the crossbar system as it is, for example, illustrated in Fig. 2 may be stressed a lot more than systems of the same type having simple chord tubes having the same dimension. Apart from that, a higher strength results as the heat influence zones have no negative effects on the material of the chord elements as they were not generated during manufacturing. According to the invention, a soldering- or welding-free way of manufacturing is used to prevent stability problems and problems of geometrical alignment. A further advantage of the system in Fig. 2 is the folding mechanism in order to reduce the transport volume. A foldable crossbar is also illustrated in the German utility patent DE 202004004942 Ul . When the crossbar is in its transport position or in its stocking position, the side sections are lying close on top of each other whereby the transport volume is reduced by up to 60% and thus reduced loading capacities result.

Fig. 3a shows a preferred implementation of a cross-section of the first or second chord elements 10, 12, where bridge 18a is implemented as a feature of the connecting point. To the bridge which was pressed already in the manufacturing process of the chord tube, in a preferred embodiment, the bracings are screwed or pinned using hollow dowel pins. That the bridge comprises a corresponding borehole is symbolically illustrated by the dashed line 18c. Thus, the main chord tube is not weakened by a heat influence zone as the bracings and also the swivel joints and fork/mortise or stud joints, which are illustrated with respect to Figs. 7 and 8, are not welded but also screwed or pinned or otherwise connected by a non-destructive releasable or detachable coupling.

Apart from that, the inventive concept enables the simple exchange or replacement of defective or bent single bracings or chord elements. When one single bracing has, for example, been bent or broken not the complete crossbar has to be replaced, but this bracing may easily be exchanged.

Fig. 3b shows an alternative implementation of the feature 18 of Fig. 1 as a groove in the tube. This groove 18b is also generated already during manufacturing of the chord element in the form of the chord tube, for example, by pressing or a corresponding drawing of the tube.

Fig. 4a shows a bracing 14, 15 with inserted and pinned fork heads 40a, 40b. The fork heads 40a, 40b have a borehole 41 via which they may be connected to a corresponding borehole of the bridge 18a (Fig. 3a) or the groove (Fig. 3b) via screws, pins, bolts, rivets, etc. Apart from this, in the chord element also a corresponding borehole is provided for each fork head which is designated by 42 in Fig. 4a, through which the fork heads comprising a cylinder extending into the tube 14, 15, the cylinder also having a borehole aligned with the borehole 42, are pinned, screwed, riveted, bolted or otherwise connected in a non-destructing releasable way.

Fig. 4b shows a bracing 14, 15 connected instead to a fork head 40a, 40b to a stud head 43 inserted into the bracing tube 14, 15 and for example pinned via a borehole 44. The stud head 43 is implemented such that it may engage into the groove 18b of Fig. 3b. Further, the stud head 43 is provided with a borehole 45 which is dimensioned so that it may be aligned with a borehole schematically indicated by 18c in Fig. 3b in the groove, so that bracing and chord element may be connected to each other without a weld seam or a solder connection or any other heat connection stressing the material having to be used.

It is to be noted that, as indicated by the groove in Fig. 3b, the borehole 18c is implemented both through the exterior wall of the chord element, through both groove walls and through the opposing exterior wall of the tube. Alternatively, it would, however, also be sufficient for the borehole only to be implemented on one wall and extending through both walls of the groove, wherein then in one groove wall, for example, a thread exists so that a screw may be screwed through both groove walls and through the bore 45 of an inserted stud head. Alternative mounting possibilities of the stud to the groove and further implementations of the groove, for example, insofar that the area 18d between the groove and the sidewall is implemented massively as it is illustrated in dashed lines in Fig. 3b, etc., may be implemented. In Figs. 5 and 6 an alternative bracing 14, 15 is illustrated which is implemented integrally in contrast to the bracing 4a and Fig. 4b. In particular, these bracings 14, 15 of Figs. 5 and 6 are manufactured from an especially pressed profile whose cross-section is illustrated in Fig. 5, wherein these bracings are brought into shape using a corresponding milling post processing to generate correspondingly rounded ends as they are for example illustrated in Fig. 6. One end includes a distance 60 between two material areas 61, 62 and a borehole 63. The material sections 61 , 62 represent the fork head of Fig. 4a and the borehole 63 corresponds to the borehole 41 of Fig. 4a. Thus, the bracing illustrated schematically in Fig. 6 may be mounted detachably to a bridge 18a, as it is illustrated in Fig. 3a. An alternative implementation in which the areas 61 , 62 do not exist and area 60 in Fig. 6 is implemented with a material, corresponds to the bracing of Fig. 4b, which may be introduced and mounted in the chord element 10, 12 of Fig. 3b with the groove 18b.

Fig. 2 shows a preferred implementation of how the bracings are attached to the individual side parts. On two opposing side sections each the frameworks with the bracings are set up equally. This means that the bracings of the side part with the chord elements 10, 12 of Fig. 2 are set up equal to the bracings which belong to the crossbar member which comprises the chord elements 27, 28. For the other side part with the chord elements 20, 22 an alternative framework is used, like for example an arrangement with one diagonal bracing instead of the two diagonal bracings of the side part with the chord elements 10, 12.

Fig. 1 1 shows a detailed view of the area 1 10 of Fig. 2, wherein in particular a swivel joint 70 is illustrated consisting of a first swivel joint section 71 , a second swivel joint section 72, a screw 73 and a nut 74. The two swivel joint sections 71, 72 are identical to each other, are set up asymmetrically, however, such that the two noses which each section comprises are on the one joint side 72 arranged on the left in Fig. 1 1 and on the other joint side 71 on the right in Fig. 1 1. Thus, on the one hand a stable joint and on the other hand a particularly flexible joint is provided as it will be explained below. Further, in Fig. 11 the chord elements 22, 27 of Fig. 2 and the bracings 75, 76, 77 of Fig. 2 are illustrated. Further, in Fig. 1 1 also feature 18, i.e. the bridge in Fig. 3a is illustrated at which the bracings 75, 76 are implemented as illustrated in Fig. 4a. Further, it is illustrated in Fig. 1 1 that the feature 18 is not provided across the complete length of the chord element 22 but exists only where bracings 75, 76 are actually to be connected. It is thus preferred to manufacture the bridge across the complete length of the chord elements when manufacturing the chord elements, for manufacturing reasons. After the manufacturing of the chord element or chord tube formed in such a way it is preferred, however, to remove the bridge everywhere where no connecting section is to exist. Removing is preferably done by a machining method like, for example, milling wherein machining methods are advantageous insofar that no heat zones result which would lead to a structural stress for the chord element.

Alternatively, the bridge may remain, however, for example, to generate further connecting points later on. With respect to the implementation having a groove as a feature, as illustrated in Fig. 13b, the groove is preferably not filled or removed but maintained.

Fig. 7 shows the upper part of the swivel joint with the chord element of Fig. 1 1, i.e. the chord element 27, the fork connector 78, the bracing 77 and the swivel joint section 71. It is further illustrated that the swivel joint section 71 is, for example, mounted via screws 81 to the chord element 27. The screws 81 are implemented such that they, for example, engage into an inside cylinder of the fork section 78 such that by the screws 81 so to speak three elements are mounted to each other, i.e. the fork section 78, the chord tube 27 and the connecting section 71. Alternatively, the fork section 78 may additionally be pinned, that is through the borehole 82. The integrally formed swivel joints are thus screwed at the front sides of the main chord tubes, as illustrated in Fig. 7, to the inserted fork connector or, as illustrated in Fig. 8, to an inserted stud connecter. Preferably, the connectors 78 and 83 are, however, separately connected to hollow dowel pins via the boreholes 82 of Fig. 7 or 84 of Fig. 8 at the chord elements 27. In particular, Fig. 8 shows the section 85 of Fig. 2, but now with a joint section of the swivel joint 86.

As it is illustrated in Fig. 2, joints also exist at the interior side, like, for example, the joint 87. Mounting this joint to the chord tubes, for example the first joint section 88 to the chord element 27, is illustrated in Fig. 9. As the swivel joint 87 or the top swivel joint section 88 is not present at one end of the chord element 27, but in an inside position where no fork connector or stud connector exists, a mounting as illustrated in Fig. 10 is used. In particular, a mounting member 89 is used, which is implemented for example in the form of a massive or partially massive cylinder. The mouthing member 89 is inserted from one side into the tube and then connected via boreholes 90 into which the screws 91 of Fig. 9 engage. The mounting member does not necessarily have to comprise a complete circle diameter, but may also be formed by other elements which may be inserted into the tube 27 and to which the screws 91 may be connected, like for example simple nuts. As it may be gathered from Figs. 7 to 10, each swivel joint which is asymmetrical in the longitudinal direction is provided with two tabs or tongues 92. The same are each arranged laterally at the chord and opposingly on the top side on the neighboring chord, as it was explained with reference to Fig. 1 1. The joints of a side or lateral section are also screwed opposingly in the transverse direction. By this, a side section may be removed and from the remaining three side sections a crossbar formed as a triangle in cross-section may be formed (also called three-point-crossbar). Further, by inserting or removing individual side sections different crossbar geometries may be built.

The swivel joints are connected to each other by means of a pivot bolt or the pivot screw 73 with nut 74. In order to optimally distribute forces applied to the swivel joints, opposite joints of each side section are connected to each other with a bar profile passing transverse across the side section, like, for example, by the bracing 76. In the upfolded position, i.e. the operating position, differently formed stiffening profiles may be used for stabilizing.

Thus, for example, at the connecting points of two crossbar elements each a cross of welded round tubes may be inserted which is fixed with the help of the connecting bolts.

By this, on the one hand, the operating position is fixed and on the other hand the torsional strength of the crossbar is all in all increased.

As it was already illustrated with reference to Fig. 3b, the main chord tube is not implemented as a bridge profile, but as a groove profile. The bracings within a side section are inserted with the main chord tube via a screwing or pin connection, wherein the individual bracing is fixed via a stud connector instead of a fork connector to the main chord. One aspect of the present invention relates to a crossbar having four individual side sections implemented with framework bracings (bracings), wherein each side section has two main cords and is connected via swivel joints to the neighboring side sections and thus may be brought into a folded down transport position or into an upright operating position. In a further implementation, the swivel joints are attached to each or at least every second node point of a side section.

In a further aspect, each swivel joint within a side section is connected to the respectively opposite swivel joint via a bar profile.

In a further aspect, the swivel joints are oppositely screwed to the main chord with the same mutual distance of neighboring swivel joints. In a further aspect, the oppositely connected swivel joints of two neighboring main cords are each screwed laterally to the chord and on the top side to the neighboring cord. The individual swivel joints are connected via a screw connection to the main cord. In a further aspect, the bracings within a side section are screwed or pinned to the chord tube especially manufactured regarding its cross-section.

In a further aspect, the bracings within a side section are manufactured from a profile specially manufactured in cross-section, without the bracings having to be manufactured as several parts. In one method for manufacturing the crossbar member, the features of the connecting sections are manufactured integrally or as a material connection with the chord element, wherein the chord elements are connected to the bracings using the section of the connecting point by pins, screws, rivets, bolts or another non-destructive releasable connection. The features for connecting, like for example the bridge are, in one implementation, in the manufacturing of the chord element, formed in the shape of a tube across the complete tube length and subsequently removed by machining, for example, everywhere where no connection of the chord element to a bracing will take place.

Figs. 13 to 16 show a further implementation of the present invention wherein the feature is not implemented integrally with the chord element, but wherein the feature is connected to the chord element by a press connection or fitting. Thus, Fig. 13 shows a cross-section through the first or second chord element 10 or 12 implemented as a tube section or tube in the embodiment illustrated in Fig. 13. In contrast to the implementations according to Fig. 3a or Fig. 3b, the main chord tube now does not comprise the integrally formed bridge 18a or the integrally implemented groove 18b anymore, but is implemented as a conventional main chord tube. Apart from that, Fig. 14 shows a perspective view of the section 18e, which is implemented as a bracing and in this embodiment comprises two boreholes 18f. Fig. 15 shows the same bridge 18e, but now attached to a connecting element 150, wherein the connecting element 150 is in this embodiment implemented as a massive cylinder. The connecting element includes three boreholes through which three screws 151 pass and are screwed into three boreholes which are not illustrated in Fig. 15 which are attached in the bridge 18e. For this purpose, the boreholes in the bridge 18e each have an internal thread. Other mountings of the screws, elements or pins or the like 151 to the bridge, like for example press fits are also sensible. The boreholes in the connecting element 150 are preferably implemented such that they have a diameter which is smaller than a screw head of the respective screw 151. Fig. 16 shows a perspective view of the screwed bridge construction. As it may be seen from Fig. 16, after inserting the connecting element into the tube, the screws 151 are screwed into an internal thread in the bridge 18e. For this purpose, corresponding first boreholes 154 are arranged in the main chord tube 10, 12 where the bridge has to be mounted. Apart from that, opposite boreholes 156 exist in the tube section to insert screws through these boreholes 156 into the boreholes 151 and corresponding boreholes 153 of the bridge 18e after inserting the connecting element 150 in order to finally screw the same to the internal threads in the boreholes 153. As the head of the respective screw 151 is larger than the borehole in the plain cylinder 150, but smaller than the diameter of the borehole 156 in the main chord tube, the screws may be inserted and screwed in until the tube 10, 12 is held between the connecting element 150 and the bridge by a press fit or press connection or is connected to the bridge and the plain cylinder 150 via a press fitting. The further implementation of this invention thus provides to implement the cross section of the main chord tube of Fig. 13 as a standard round tube. The particularity is that the bridges to which the diagonal bracings are screwed or pinned and which are illustrated in Fig. 14 and 15 are implemented as a single part. The bridges are screwed to the main chord tube via the inserted, preferably massive cylinder 150 as it is illustrated in Fig. 15. The total assembly of main chord tube, inserted cylinder and screwed bridge is illustrated in Fig. 16.

The advantages of this construction again result from the missing heat influence zone. The main chord tube is not weakened by the missing heat influence zone as the bridges and bracings and also the swivel joints and possibly existing fork/stud connectors of the bracings are not welded, but screwed or pinned. Also, the possibility to exchange defective bridges individually is a further advantage. In a further embodiment of the present invention, again a first chord element 10 and further a second chord element 12 are present. Apart from this, at least one bracing 14, 15 is present, which is connected to the first chord element 10 and the second chord element 12 at one connecting point 17 each. The connecting point includes a section 18 of the chord element 10 and a section 19 of the bracing 14, 15. According to this embodiment, the crossbar member comprises a feature at section 18 of the chord element by which is detachably fixed to the chord element the bracing 14 or 15. In particular, this feature is implemented as a borehole 18f, as illustrated in Fig. 14, or generally such that the bracing and the first and second chord elements are connected via the connecting point by at least one screw or one pin or one rivet or one bolt or another non-destructive releasable coupling. This embodiment is useful in particular with modular lattice girders or beams regarding which a load capacity or carrying capacity is required, which is not too high, like for example with decoration crossbars. Here, the bridge may also be welded to the chord tube, which is why the inserted cylinder is omitted. Although the welding may present a weakening of the chord element, it is still guaranteed compared to a conventional crossbar as it is illustrated in Fig. 12, that only a minimum amount of welding energy or welding problems are introduced as the bracing is not welded to the chord element, but detachably fixed to the chord element. Thus, compared to a standard crossbar according to Fig. 12, the thermal budget and thus the problems of material weakness and material warping are clearly reduced, as bracings are detachably connected to the chord elements and not welded. This enables to exchange defective bracings by releasing the detachable connection and a defective bracing or a defective chord element may be replaced by an intact bracing or by an intact chord element.

Claims

1. A crossbar member, comprising: a first chord element (10) and a second chord element (12); at least one bracing (14, 15) connected to the first chord element (10) and the second chord element (12) at one connecting point (17) each, the connecting point (17) including a section (18) of the chord element (10) and a section (19) of the bracing (14, 15), and wherein the section (18) of the chord element comprises a feature integrally implemented with the chord element (10, 12) or connected to the chord element (10, 12) by a press connection.

2. The crossbar member according to claim 1, wherein the feature (18) comprises a bridge (18a) protruding from the chord element (10, 12) which was formed with the chord element, and wherein in connecting point (19) of the bracing comprises a fork-shaped feature (40a, 40b) for engaging the bridge (18a), or wherein the feature (18) is a groove (18b) in the chord element (10, 12) which was formed with the chord element (10, 12), and wherein the connecting point (19) of the bracing comprises a stud-shaped feature (43) for engaging the groove (18b).

3. The crossbar member according to claims 1 or 2, wherein the connecting point (17) of the bracing and the first or second chord elements are connected by at least one screw or a pin or a rivet or a bolt or another non-destructive releasable coupling.

4. The crossbar member according to one of the preceding claims, wherein the first chord element (10) or the second chord element (12) is each a chord tube, wherein the connecting point (17) is a feature (18) integrally formed with the tube or wherein the bracing (14, 15) comprises a tube to which the section (19) of the connecting point is mounted or which is worked at its end so that the section of the connecting point is integrally formed with the tube (60, 61, 62).

5. The crossbar member according to one of the preceding claims, wherein the first chord element (10) or the second chord element (12) comprises no weld seam, no soldered seam or no otherwise generated fusion connection.

6. The crossbar member according to one of the preceding claims, wherein the section of the chord element (18) of the connecting point was pressed together with the manufacturing of the chord element and trimmed using a machining method.

7. The crossbar member according to one of the preceding claims, wherein the section of the chord element comprises a bridge (18a) which was removed by a machining method in an area of the chord element which is no section of the connecting point.

8. The crossbar member according to one of the preceding claims, wherein an upper or lower end of the first or second chord element (10, 12) comprises a stud connector (83) or a fork connector (78) to a further crossbar member.

9. The crossbar member according to claim 8, wherein the stud connector (83) or the fork connector (78) is implemented separately from the first or second chord element or connected by at least one screw or one pin or one rivet or one bolt or another nondestructive releasable coupling.

10. The crossbar member according to one of the preceding claims, which may be mounted into a foldable crossbar, wherein the first chord element (10) or the second chord element (12) comprises a section (71,72) of a swivel joint (70), wherein the section (71 , 72) is implemented separately from the first and second chord element (10, 12) and connected by at least one screw or one pin or one rivet or one bolt or another non-destructive releasable coupling.

1 1. The crossbar member according to one of the preceding claims, wherein the section of the swivel joint comprises two spaced apart tongues (92) provided with a borehole each.

12. The crossbar member according to claim 10 or 12, wherein the swivel joint (70) comprises at least one borehole, wherein the first or second chord element (10, 12) is a tube with an inside diameter and comprises at least one borehole, and wherein further a mounting member (89) is implemented which is dimensioned so that it fits into the tube with the inside diameter, wherein the mounting member (81 ) comprises a borehole, and wherein the section (71 , 72) of the swivel joint is connected by a pin, a screw, a rivet, a bolt or another non-destructive releasable connection using the borehole in the swivel joint section (71 , 72), the borehole in the tube (10, 12) and the borehole in the mounting member (89), to the first or second chord element (10, 12).

13. The crossbar member according to claims 10, 1 1 or 12, wherein a swivel joint section (71 , 72) comprises at least one borehole, wherein the first or second chord element (10, 12) is a tube with an inside diameter and comprises at least one borehole, wherein further a separate connector (78, 83) to a further crossbar member is provided with a borehole, wherein the section (71 , 72) of the swivel joint is connected by a pin, a screw or a rivet or a bolt or another non-destructive releasable connection using the borehole in the tube, using the borehole in the swivel joint section (71, 72) and using the borehole in the separate connector (78, 83).

14. The crossbar member according to one of claims 1 to 13, wherein the first chord element (10) and the second chord element (12) are each implemented as a tube and the feature (18) is a section of the tube which is geometrically different from the tube shape.

15. A method for manufacturing a crossbar member, comprising: providing a first chord element (10) and a second chord element (20); and providing a bracing (14, 15), wherein in the step of providing the first chord element and the second chord element a section (18) of a connecting point (70) of the chord element and the bracing is manufactured integrally with the chord element or connected to the chord element (10, 12) by a press connection; and connecting the first chord element (10) or the second chord element (20) with the bracing (14, 15) using the section of the connecting point by a screw or a rivet or a pin or a bolt or another non-destructive releasable coupling.

16. The method according to claim 15, wherein the section (18) of the connecting point comprises a bridge (18a) formed across the complete length of the first or second chord element (10, 12) together with the manufacturing of the first or second chord element (10, 12), and wherein the step of providing the first or second chord element comprises a removal of the bridge by machining where no connecting section is present.

17. A crossbar, comprising: at least two crossbar members according to one of claims 1 to 14, wherein the at least two crossbar members are connected to each other by bracings or joints at connecting points, wherein each connecting point includes a section of the chord element and a section of the bracing and wherein the section of the chord element comprises a feature formed integrally with the chord element.

18. A crossbar, comprising: at least two crossbar members, wherein each crossbar member comprises a first chord element (10) and a second chord element (12) connected to the first chord element (10), wherein at a chord element of the first crossbar member a first section (71) of a swivel joint (70) is attached, wherein at a chord element of the second crossbar member a second section (72) of the swivel joint (70) is attached, wherein each of the sections comprises at least two spaced apart tongues (92) each provided with a borehole in the longitudinal direction of the swivel joint, and wherein the first section (71) and the second section (72) are assembled such that the swivel joint (70) is asymmetrical in the longitudinal direction.

19. The crossbar according to claim 18, wherein at the two chord elements of a crossbar member the two sections of the swivel joint are each attached at opposing sides opposite to each other so that by building in a further crossbar member using the swivel joint or by removing same and reassembling the remaining crossbar members a three-point-crossbar with three crossbar members, a four-point-crossbar with four crossbar members or a crossbar with more than four crossbar members may be assembled.

The crossbar member according to claim 1 , wherein the section of the chord element (10, 12) is connected to the chord element (10, 12) by screws or pins, or wherein the section of the chord element (10, 12) is connected to a further mounting element (150) by screws or pins, wherein the mounting element is arranged with respect to the chord element (10, 12) so that at least one section of the chord element (10, 12) is sandwiched between the section (18) of the chord element (10, 12) and the further mounting element (150).

The crossbar member according to claim 20, wherein the chord element (10, 12) is tube-shaped, wherein the further mounting element (150) comprises an inside cylinder which is introduced into the tube- shaped chord element (10, 12), and wherein one or several screws or pins extend from the section (18) through the chord element (10, 12) in the or through the inside cylinder to mount the section to the chord element.

The crossbar member according to claim 21 , wherein the inside cylinder is implemented massively.

The crossbar member according to claim 1, wherein the chord element comprises a tube section comprising at least one borehole each on opposite sides, wherein the section comprises a borehole (153) with an internal thread, wherein a connecting element (150) is implemented as a tube insert and comprises at least one borehole (151), and wherein at least one screw (151) is accessible via a borehole (156) in the tube section and extends through the borehole of the tube insert (150) and is accessible via a borehole (154) opposite to the borehole in the tube section and is screwed into the borehole (153) with the internal thread of section (18e) in order to mount section (18e) to the tube section of the chord element (10, 12) by the press connection.

24. The crossbar member according to claim 23, wherein the borehole (151) in the connecting element (150) comprises a smaller diameter than a borehole (156) in the tube section, wherein the screw (151) comprises a screw head whose diameter is smaller than the borehole (156) in the tube section but is greater than the borehole (151) in the connecting element (150).

25. The crossbar member according to claims 1, 20-24, wherein the section is implemented as a bridge (18e) having at least one borehole (18f) for mounting the bracing (14, 15).

26. A crossbar member, comprising: a first chord element (10) and a second chord element (12); at least one bracing (14, 15) connected to the first chord element (10) and the second chord element (12) at one connecting point (17) each, wherein the connecting point (17) includes a section (18) of the chord element (10) and a section (19) of the bracing (14, 15), and wherein the section (18) of the chord element (10, 12) comprises a feature by which the bracing (14, 15) is releasably attached to the chord element (10, 12).

27. The crossbar member according to claim 26, wherein the feature is a borehole (18f).

28. The crossbar member according to one of claims 26 or 27, wherein the connecting point (17) of the bracing and the section (18) of the chord element are connected by at least one screw or one pin or one rivet or one bolt or another non-destructive releasable coupling.