AU739951B2 - Coupling purlin consisting of two or more wooden beams adjoining and overlapping each other longitudinally, as well as fastening element for joining two overlapping end areas of wooden beams for use as a coupling purlin - Google Patents

Abstract

The invention relates to a coupling purlin (1) for which two wooden beams (2, 3) adjoining and overlapping each other longitudinally are connected to each other by fastening elements. The overlapping end areas of the wooden beams (2, 3) are connected by means of screws (5) which are positioned at an acute angle in relation to the adjoining surfaces (6, 7) of the wooden beams (2, 3). Said screws (5) are screwed in along a plane situated at a right angle to the surfaces (6, 7).

Description

Coupling purlin consisting of two or more wooden beams adjoining and overlapping each other longitudinally, as well as fastening element for joining two overlapping end areas of wooden beams for use as a coupling purlin The invention relates to a coupling purlin comprising two or more wooden beams adjoining overlappingly in longitudinal direction, the overlapping end regions being joined to each other by fastening elements, as well as to a fastening element for joining two overlapping end regions of wooden beams for insertion in a coupling purlin.

Coupling purlins, otherwise known as rafter purlins, are formed from individual lengths of load-bearing members, which are joined together as i continuous flexurally stiff load-bearing members by the supports, for example the main trusses, by nailing or doweling. The individual load-bearing 15 members formed as wooden beams are disposed lengthwise, in such a way that they offset from each other by the beam width, and usually overlap in the region of the supports or main trusses disposed thereunder. Since a mutual flexurally stiff joint between the overlapping end regions is required, pins alone are normally not permitted as the connecting means, because of their flexibility. In this context, it has already been proposed that recesses be provided in the adjoining surfaces of the overlapping end regions of the wooden beams, washer-like connecting elements being inserted in these OVo recesses to absorb the shear forces between the two overlapping end regions of the wooden beams. Each two overlapping end regions of wooden beams are held together by additional tie rods passing through the end regions of the wooden beams and the washer-like parts. When such fastening elements are used, primarily shearing and bending stresses and strains are developed. The fastening elements to be inserted must therefore have appropriately large dimensions.

It is an advantage of the present invention to provide a coupling purlin of the type mentioned in the introduction as well as a fastening element for joining wooden beams as a coupling purlin, with which the coupling purlin and fastening element substantially improve mutual fastening of the overlapping end regions of wooden beams.

According to the invention, there is provided a coupling purlin comprising a plurality of wooden beams adjoining overlappingly in longitudinal direction at their end regions and joined with one another in a flexurally stiff manner by means of screws, wherein the screws are arranged at least approximately at right angle to the surfaces of the wooden beams abutting against one another, in planes running at least approximately at right angle to the longitudinal axes of the wooden beams, characterised in that the screws in the planes running at least approximately at right angle to the longitudinal axes of the wooden beams are oriented at acute angle to the surfaces of the wooden beams abutting against one another and that the screws are screwed in without predrilling holes in the wooden beams.

By these features according to the invention, the inserted fastening elements in the form of screws are subjected to a combination of tensile and compressive stress and strain, the forces being transmitted by the thread provided on the screws. In such a coupling purlin, virtually no preparatory work is necessary, since the operation of driving in the screws, which are driven in at an acute angle to the adjoining surfaces of the wooden beams, can be performed on the spot on the building. With such a procedure, virtually no bending and shearing stress and strain, but instead almost exclusively tensile and compressive stress and strain are developed. This is achieved both by the use of screws as fastening elements and by the special manner of driving in along a plane running transversely relative to the surface. The operation of driving in at an acute angle achieves a particularly good effect. In addition, wooden beams can usually also be mutually fastened rapidly and in particular securely, since there is no need for predrilling for such screws.

A further improved embodiment is achieved by inserting screws in pairs wherein the screws are oriented parallel to each other with space therebetween, or else in pairs wherein the screws are oriented in crosswise directions and disposed in successive planes having a small space therebetween. Thereby an optimum joint is produced between the overlapping end regions of wooden beams, tensile and compressive forces then being transmitted in the same way to both end regions of the wooden beams.

In such an alternative it is proposed that the screws inserted in pairs while having crosswise orientation if applicable and being disposed successively with space therebetween be screwed in starting from the same external surface of a wooden beam. In this case, each of the screws is driven in from the same side, one at right angles or in the oblique upward direction and the other at right angles or in the oblique downward direction, which is probably the simplest method from the handling viewpoint. In this way, mutual joining of wooden beams to form coupling purlins can always be undertaking from the same side.

a *e o *oo o WO 98/57005 PCT/EP98/03376 -3- It is also possible, however, that each of the screws inserted in pairs while having crosswise orientation if applicable and being disposed successively with space therebetween can be screwed in starting from diametrically opposite external surfaces of the two wooden beams to be joined to each other. Such an alternative embodiment may be advantageous depending on loading case and also depending on design of the screws to be inserted.

In this context, it is also possible that one or more pair(s) of screws inserted in crosswise orientation if applicable is inserted at a short distance from the respective end of a wooden beam. Such an alternative embodiment is preferably used especially for coupling purlins with large dimensions and Slong overlapping end regions of the wooden beams. A plurality of fastening portions is then provided over a relatively large region of the overlapping end regions.

By the use of screws as fastening elements, however, many more possibilities can be opened up by the present invention. For example, a special embodiment provides that one or more of the screws 1 driven in at an acute angle projects or project beyond the lower surface of the wooden beams to be joined to each other and engages or engage with its end or their ends in a wooden load-bearing member disposed thereunder. In the manner according to the invention, therefore, not only can mutual fastening of the overlapping end regions of wooden beams be achieved optimally, but also it is additionally possible, by means of the same screws, to join the coupling purlin formed from O wooden beams to the wooden load-bearing member disposed thereunder. Precisely when the span widths provided for the individual wooden beams of the coupling purlin are not too large, it could be sufficient under certain circumstances to join the two overlapping end regions of the wooden beams to each other in what for practical purposes is one working operation, and simultaneously to fasten the coupling purlin formed thereby to the wooden load-bearing member disposed thereunder. In this way it is always possible additionally to insert screws for mutual fastening at the immediate ends of the overlapping end regions of the wooden beams.

Another advantageous embodiment for fastening of a coupling purlin with the wooden load-bearing member disposed thereunder can also exist in that there is or are inserted, parallel to the facing 0 surfaces of the two overlapping end regions of the wooden beams, in the region of the intersection between a coupling purlin and a wooden load-bearing member disposed thereunder, one or more screws in addition to the screws inserted at an acute angle or in lieu thereof. The screw(s) inserted 7T U WO 98/57005 PCT/EP98/03376 -4parallel to the facing surfaces serves or serve for practical purposes only as mutual fastening of the coupling purlin with the wooden load-bearing member, the main concern here being that the coupling purlin does not tilt on the wooden load-bearing member running at an inclination corresponding to that of the roof. It is therefore necessary only to press the coupling purlin appropriately against the wooden load-bearing member.

In this context, it is advantageous for the additional screw(s) to be associated with the overlapping end region of the wooden beam which is higher in the direction of the roof slope. In this way a further improved feature as regards tilting moment is achieved, since fastening takes place in the uppermost portion relative to the roof slope, and the lowermost portion of the coupling purlin, as viewed in the direction of the roof slope, forms the additional bracing and thus represents a corresponding lever arm. Thereby only a relatively small force is needed by the screw to be inserted or the screws to be inserted in order to prevent tilting of the coupling purlin.

Optimal mutual fastening of the overlapping end regions of wooden beams to form a coupling purlin is achieved when the screws inserted at an acute angle relative to the surface of the wooden beams include an angle of approximately 450 with the surface, so that the screws disposed successively while having crosswise orientation with space therebetween are disposed at right angles to each other. In this way an extremely uniform distribution of forces over both end regions of the wooden -O beams is achieved, and in this case the two screws of each pair are also subjected in the same way to tensile and compressive stress and strain.

The fastening element according to the invention for joining two overlapping end regions of wooden beams for insertion in a coupling purlin is characterized by a screw with a shank, which is provided ,6 at least at its two end regions with a threaded portion, wherein two portions of different diameter but the same thread pitch are disposed successively, and wherein the portion with the larger diameter has a minor diameter corresponding at least approximately to the major diameter of the portion with the smaller diameter. By these features according to the invention, it is ensured that the overlappingly adjoining end regions of wooden beams are joined to each other in this adjoining position, without 0 being pulled toward each other or even forced apart from each other by application of sufficient force.

the same thread pitch is achieved throughout, and so threaded regions already completed in the wooden beams-are not destroyed even in the case of two separate threaded portions with 57 C WO 98/57005 PCT/EP98/03376 different diameter, but at worst merely become enlarged in diameter under certain conditions.

Precisely by this fact is it also possible to allow optimally for combined tensile and compressive stress and strain during use of coupling purlins.

From the viewpoint of manufacture of the screw, and also of insertion of the screw in wood, a particularly advantageous feature lies in matching the diameters of the two threaded portions. In this case the forming conditions encountered in the manufacture of such screws are not too severe. When such screws are driven into wood, it proves advantageous that the already formed thread is for practical purposes pressed flat by the body cross section following the portion with the smaller O diameter, and so only the thread turns in the wood, and not the entire cross section of the largerdiameter portion have or has to be compressed. The thread with the larger diameter then forms a thread of correspondingly larger cross section, and even greater compaction of the wood around the screw therefore takes place, especially in this region. Splitting at the end regions of the wooden beams is already prevented, however, by the fact that a threaded portion with smaller diameter was made immediately beforehand by the screwing-in operation. In this way it is naturally also possible to insert such screws without predrilling, and so an additional working operation can be avoided in any case.

Advantageously, an internal drive for a driving tool is formed at the free end of the portion with larger aO diameter. Thereby the necessary torque can be transmitted, although the possibility nevertheless exists that this portion with the internal drive can be countersunk to below the external surface of the wooden beam.

The process of countersinking the screw head is facilitated by these features. Furthermore, the last Spair of thread turns is pressed flat in the wooden beam, thus achieving additional compaction of the wood in this region.

WO 98/57005 PCT/EP98/03376 -6- Further features according to the invention and special advantages will be explained in more detail in the description hereinafter with reference to the drawings, wherein: Fig. 1 shows a section through a coupling purlin in the region of an inserted fastening element; Fig. 2 shows a view of a screw used as a fastening element; Fig. 3 shows a coupling purlin formed from two overlappingly adjoining wooden beams and bearing on a wooden load-bearing member, the mutual fastening of the wooden beams by screws being schematically illustrated; Fig. 4 shows a diagram similar to that of Fig. 3, except that the joint between the coupling purlin and the wooden beam is schematically illustrated.

Fig. 5 shows a section through a coupling purlin with a joint according to the prior art method; Fig. 6 shows an oblique view of a coupling purlin with a wooden load-bearing member disposed thereunder, wherein both the joint between the wooden beams and the coupling purlin and the joint between the coupling purlin and the wooden load-bearing member are illustrated in 0 the manner which has been standard heretofore.

Fig. 7 shows a further practical example of a coupling purlin formed from two overlappingly adjoining wooden beams, which purlin bears on a wooden load-bearing member, the mutual fastening of the wooden beams by screws being schematically illustrated; Fig. 8 shows a diagram similar to that of Fig. 7, except that the joining of the wooden beams by nails known heretofore is schematically illustrated.

In a coupling purlin 1, two wooden beams 2 and 3 adjoining overlappingly in longitudinal direction are mutually joined by fastening elements. Coupling purlins 1 then bear on appropriate supports or on Q ooden load-bearing members 4, which are oriented horizontally or disposed at an inclination cong to that of the roof. In the description hereinafter, reference will always be made to two crresponding to that of the roof. In the description hereinafter, reference will always be made to two WO 98/57005 PCT/EP98/03376 -7wooden beams 2 and 3 which form a coupling purlin when joined to one another. Within the scope of the invention, however, it would be entirely conceivable to provide more than two wooden beams adjoining each other overlappingly, the end regions of the wooden beams then alternating, for example, from one side to the other. In such a case it would also be conceivable, once two overlapping end regions of wooden beams had been mutually fastened, to add the next wooden beam and to fasten this overlapping end region once again with the next wooden beam in sequence. In this way the directly adjoining, overlapping end regions of two wooden beams would always be joined to one another.

\O Mutual joining is achieved by fastening elements in the form of screws 5, which are oriented at an acute angle relative to adjoining surfaces 6, 7 of wooden beams 2, 3 and are driven in at least approximately in a plane running transversely relative to these surfaces 6, 7.

As is evident from Figs. 1 and 3 in particular, such screws 5 are inserted in pairs, and are oriented IS in crosswise directions and disposed in successive planes having a small space therebetween. In this way it is possible for only one pair of such screws 5 to be disposed at each of the two immediate ends of the end regions of wooden beams 2 and 3. Depending on the forces to be transmitted, however, it may also be useful to provide two of such pairs 8 of screws 5, as illustrated in Fig. 3, or even more than two of such pairs 8 of screws 5. In the embodiment illustrated in Fig. 1, each one of 1O the screws 5 inserted in pairs while having crosswise orientation and being disposed successively with space therebetween is screwed in starting from diametrically opposite external surfaces 9 and of the two wooden beams 2, 3 to be joined to each other. It would also be possible, however, for the screws inserted in pairs while having crosswise orientation and being disposed successively with space therebetween to be screwed in starting from the same external surface 9 or 10 of one of wooden beams 2 and 3.

The angle at which screws 5 are screwed in will be selected to reflect the particular loading cases, but an embodiment will prove particularly advantageous in which screws 5 inserted at an acute angle 3 relative to surface 6, 7 of wooden beams 2, 3 include an angle a of approximately 450 with surface WO 98/57005 PCT/EP98/03376 -8- 6, 7. Thereby screws 5 disposed successively while having crosswise orientation with space therebetween are oriented approximately at right angles to each other, whereby the tensile and compressive forces on the two wooden beams 2, 3 are transmitted equally and load absorption is ensured over the entire height of wooden beams 2, 3.

In this context, it must be pointed out that it is not absolutely necessary for screws 5 to be screwed in starting from surfaces 9 and 10 of wooden beams 2, 3. It would also be conceivable to start these screws on upper side 11 or lower side 12 of the coupling purlin, although in this case a region disposed relatively far toward the outside must of course be selected to ensure that both wooden 1O beams 2, 3 can be appropriately engaged if the screwing-in process takes place at an acute angle.

One possible alternative embodiment of screw 5 to be inserted as fastening element is shown in Fig.

2. In this screw 5, threaded portions 13 and 14 with different diameters D1 and 02 respectively but with the same thread pitch are provided at least at the two free end regions of a shank. Portion 14 with larger diameter D2 has a minor diameter D3 which corresponds at least approximately to the major diameter D1 of portion 13. An internal drive 15 for a driving tool is formed at the free end of portion 14 with larger diameter D2. Of course, the configuration of the drive for a driving tool can have the most diverse shape and form. In the illustrated configuration, a cylindrical screw head 16 with diameter D4, which is larger than that of the threaded portion, is provided at the end of the shank equipped with internal drive 15. Transition 17 between threaded portion 14 and screw head 16 has flaring frustoconical shape. Thereby the capability of countersinking screw head 16 has been created in simple manner, without requiring excessive widening of the threaded hole and thus tearing in the region of wooden beams 2, 3.

Within the scope of the invention it is entirely conceivable to insert screws 5 of different configuration.

The only requirement to be met is that screw 5 must have a threaded portion at both end regions of the shank, so that sufficient threaded engagement for transmission of the necessary tensile and Scompressive forces is present in the two wooden beams 2, 3 to be joined to each other. In this respect, it is also possible for two threaded portions to have matching profiles, or in other words for WO 98/57005 PCT/EP98/03376 -9the same thread pitch to be present throughout regardless of whether a thread-free shank is present between the threaded portions. It is also conceivable, however, to provide a threaded portion continuously over the entire length of screw A penetrating point 18 resembling the point of a wood screw is formed at the free end of screw Within the scope of the invention it is also conceivable to provide here a kind of boring point or a corresponding boring part, to bring about not only widening of the wooden beams for receiving screw but also cutting away of chips to form a corresponding opening for receiving screw 5. In such a case, the fibers are severed while screw 5 is being driven in, thus reducing the danger of splitting if I0 necessary.

From the diagram according to Fig. 4 it can be seen that, in addition to the fastening between individual wooden beams 2, 3, which form coupling purlin 1, fastening can also be achieved between coupling purlin 1 and the wooden load-bearing member disposed thereunder. In this case screws driven in at an acute angle project beyond lower surface 12 of the two overlapping end regions of wooden beams 2, 3 and engage with their ends in wooden load-bearing member 4 disposed thereunder. By means of this type of fastening, there can also be simultaneously achieved proper fastening between coupling purlin 1 and wooden load-bearing member 4. In this context, it is also possible for one or more screws aligned parallel to facing surfaces 6, 7 to be inserted in the region ,O of the intersection between coupling purlin 1 and a wooden load-bearing member 4 instead of or in addition to screws 5 inserted at an acute angle. Such additional screws are advantageously allocated to the overlapping end region of wooden beam 2 which is higher in the direction of the roof slope.

Thereby tilting of the coupling purlin is adequately prevented.

'dS Figs. 5 and 6 illustrate how heretofore, with relatively laborious work, the overlapping end regions of wooden beams were fastened to form coupling purlins and how fastening of the coupling purlins with wooden load-bearing members disposed thereunder was achieved. To join two wooden beams 2 and 3, it was necessary to make recesses 19 in two facing surfaces 6 and 7, in order that there could be inserted a washer-like part 20, which then absorbed the necessary shearing and bending stresses OJW* and strains. The two wooden beams 2 and 3 were then held together by additional tie rods 21 WO 98/57005 PCT/EP98/03376 passing through wooden beams 2 and 3. To fasten coupling purlin 1 with wooden load-bearing member 4 disposed thereunder, there were usually used angle brackets 22 formed from sheet-metal parts and fastened by screws both to coupling purlin 1 and wooden load-bearing member 4.

S In the practical example according to Figs. 7 and 8, screws 5 are inserted in pairs wherein the screws are disposed parallel to each other with a small space therebetween. Under these conditions it is possible that only one pair of such screws 5 is disposed at each of the two immediate ends of the end regions of wooden beams 2 and 3. Depending on the forces to be transmitted, however, it may also be useful to provide two or more of such pairs of screws 5. Screws 5 inserted beside each other with space therebetween can be screwed in starting from diametrically opposite external surfaces 9 and 10 of the two wooden beams 2, 3 to be joined to one another. As is evident from Fig. 1, however, it is also possible that the screws inserted in pairs while being disposed parallel to each other with space therebetween can be screwed in starting from the same external surface 9 or 10 of one of wooden beams 2 or 3.

Fig. 8 illustrates how heretofore, with relatively laborious work, the overlapping end regions of wooden beams were fastened to form coupling purlins. To join two wooden beams 2 and 3, it was necessary to hammer in a plurality of nails 23 at two adjacent surfaces 6 and 7, but these nails were capable of absorbing only shearing and bending stresses and strains.

Nails used for coupling purlins must inherently be of the smooth-shank type. Because the roof inclination causes stresses and strains which continuously tend to cause extraction, however, predrilling is not permitted if smooth-shank nails are used. In the case of high stresses and strains, there are used special nails (screw nails, grooved nails) which, up to a diameter of 5 mm and up to Sa maximum length of 160 mm, can be driven in with pneumatic nail guns. Nails with larger diameter or greater length must be driven in manually, in which case predrilling is again not permitted. Such work is laborious and under certain circumstances is also dangerous, since it must usually be R erformed at high elevations on a construction site.

Ss illustrates that a substantial improvement is achieved by the described features in mutual joining is illustrates that a substantial improvement is achieved by the described features in mutual joining WO 98/57005 PCT/EP98/03376 -11 of wooden beams to form coupling purlins and also between coupling purlins and wooden loadbearing members. Not only the joint in itself but also the handling, especially handling on the construction site, is improved, since no exactly fitting recesses have to be prepared in the wooden beams and no holes have to be predrilled.

Claims (8)

1. A coupling purlin comprising a plurality of wooden beams adjoining overlappingly in longitudinal direction at their end regions and joined with one another in a flexurally stiff manner by means of screws, wherein the screws are arranged at least approximately at right angle to the surfaces of the wooden beams abutting against one another, in planes running at least approximately at right angle to the longitudinal axes of the wooden beams, characterised in that the screws in the planes running at least approximately at right angle to the longitudinal axes of the wooden beams are oriented at acute angle to the surfaces of the wooden beams abutting against one another and that the screws are screwed in without predrilling holes in the wooden beams. 15 2. A coupling purlin according to claim 1, characterised in that screws are inserted in pairs, the screws being oriented in crosswise directions and disposed in successive planes having a space between them.

3. A coupling purlin according to claim 2, characterised in that the screws are inserted in pairs while having crosswise orientation and being disposed successively with space between them are screwed starting from the same external surface of a wooden beam.

4. A coupling purlin according to claim 2, characterised in that one of the screws inserted in pairs while having crosswise orientation and being "II: disposed successively with space between them are screwed in starting from external surfaces averted from another of the two wooden beams to be joined to one another. A coupling purlin according to any one of claims 2 to 4, characterised in that at least one pair of screws inserted in crosswise orientation is spaced from the respective end of a wooden beam.

6. A coupling purlin according to any one of claims 2 to 5, characterised in that the screws inserted inclined at an acute angle to the surface of the wooden beams include an angle approximately 450 with the surface, so that the screws following one another in succession at a distance are provided at right angles to one another.

7. A coupling purlin according to any one of claims 1 to 6, characterised in that one or more of the screws screwed in at an acute angle projects or 13 project beyond the lower surface of the wooden beams to be joined with one another and engages or engage with its end or their ends a wooden load- bearing member disposed thereunder.

8. A coupling purlin according to claim 7, characterised in that in the region of the intersection between a coupling purlin and a wooden load- bearing member disposed thereunder one or more additional screws is or are inserted in addition to the screws inserted at an acute angle parallel to the abutting surfaces of the two overlapping end regions of the wooden beams.

9. A coupling purlin according to claim 8, characterised in that the additional screw(s) is or are allocated to the overlapping end region of the wooden beam which is higher in the direction of the slope of the roof. 0. A coupling purlin screw for a coupling purlin according to any one of claims 1 to 9, characterised by a shank, that has at least at both end regions a threaded portion each, wherein both threaded portions have different 'i 15 diameters, adjoin to one another and have the same pitch and wherein the threaded section with the larger diameter has a root diameter corresponding at least approximately to the outside thread diameter of the portion with the smaller diameter. *oo

11. A coupling purlin substantially as described herein with reference to Figures 1 to 4 and 7. Dated this thirty-first day of August 2001 SFS Industrie Holding AG Patent Attorneys for the Applicant: FB RICE CO