AT526020B1 - ridge/hip cover element - Google Patents

Abstract

Ridge/hip covering element (1) with a ridge/hip stone (10) for attachment to a ridge (5) or hip of a roof (3) covered with roof covering elements (2, 2'). In order to achieve a ventilation function and a relatively simple attachment to the roof peak and assembly with a short expenditure of time, but at the same time to achieve protection against extreme weather influences, it is provided that the ridge/hip covering element (1) comprises a ventilation insert (4, 4') which is mounted at the factory on the inside of the ridge/hip stone (10) and is inserted in a force-fitting and/or form-fitting manner and is designed such that, when the ridge/hip covering element (1) is installed, it creates a ventilation gap (6, 7) between the ridge/hip stone (10) and the roof covering elements (2, 2') arranged in the area of the ridge/hip (5) and forms ventilation communication between a roof interior (109) and an environment (11).

Description

Description

[0001] The invention relates to a ridge/hip covering element with a ridge/hip stone for attachment to a ridge or hip of a roof covered with roof covering elements.

[0002] In many cases, roof ridges or hips are provided with ventilation elements to enable sufficient ventilation of the interior of the roof. Ridge covering elements with a ventilation function are already known in a wide variety of designs, but the installation of ventilation grilles or air openings requires a relatively high level of technical effort compared to the actual process of roof covering, since corresponding openings for ventilation elements have to be cut out or prepared in another way.

[0003] Fig. 1 of GB 2176002 A shows a fastening process in which an elongated ventilation element is fixed to the ridge and then the ridge stones (without ventilation insert) are attached to the roof one after the other, with the ridge stones being placed on the ventilation element placed on the roof and then nailed into place. The assembly personnel must therefore always ensure that the ventilation element and ridge stone are correctly positioned relative to one another and at the same time carry out the fastening process on the roof. Figs. 1 and 2 of this document show the final assembled state of the ventilation element and ridge stone, but these are brought to the assembly site separately and the ridge stone does not have a separate ventilation insert. It is clear from the illustrations in GB 2176002 A that the ventilation element is first attached to the ridge and only then is the ridge stone placed on top.

[0004] In the case of the ridge tile according to DE 20 2018 000 451 U1 with a profile element on the underside that has surfaces with a spring effect, an intermediate step of mounting an elongated profile element on the roof ridge must be carried out when attaching it to the roof before the ridge tile can be attached, whereby it must be pressed down against the spring effect and moved into a locking position. Direct attachment to the roof is not intended and is not suggested anywhere in this document. The fastening method specified in DE 20 2018 000 451 U1 is very complex in terms of construction, but not very reliable due to the spring effect decreasing over time. Attaching a separate profile rail increases the workload, as it must be aligned exactly opposite the last row of roof tiles and the battens. Ventilation openings are provided in the profile parts, but a ventilation gap between the ridge tile and the roof tile is not described.

[0005] EP 1 378 616 A1 discloses a V-shaped fiber cement roof tile which has a recessed U-overlap section with a transverse drainage slot at one end to drain penetrating rainwater. A molded, transverse thickening is provided on the underside, which, however, has no ventilation function whatsoever.

[0006] The object of the invention is therefore to provide a ridge/hip cover element with a ventilation function, which can be attached to the roof peak relatively easily and the installation can be carried out with little expenditure of time, but at the same time protection against extreme weather influences can be achieved.

[0007] Another object of the invention is to enable the ridge/hip covering element to be laid flush in the ridge/hip longitudinal direction.

[0008] This is achieved according to the invention in that the ridge/hip covering element comprises a ventilation insert which is factory-mounted on the inside of the ridge/hip stone and is inserted in a force-fitting and/or form-fitting manner and is designed such that, when the ridge/hip covering element is installed, it creates a ventilation gap between the ridge/hip stone and the roof covering elements arranged in the area of the ridge/hip and forms ventilation communication between a roof interior and an environment.

[0009] During the manufacturing process, the ridge/hip stone is first covered with a half-shell type

by an injection molding process and then the ventilation insert is attached to the inside opposite the weather side, which can be done by form fit, friction fit or a combination of these. The advantage of the ventilation insert provided according to the invention in this way is the factory assembly on the ridge/hip stone, so that the ridge/hip covering element according to the invention assembled in this way can be immediately attached to the installation point on the roof to be covered on the ridge without intermediate steps and the ventilation of the interior of the roof can also be created in one operation, with the ventilation insert acting as a spacer between the ridge/hip stone and the roof covering elements in order to form the ventilation gap. This simplifies delivery logistics and reduces the amount of work involved.

[0010] The ventilation insert is made of a different material than the ridge/hip stone, preferably a light, flexible material such as sheet metal, in order to enable a low weight of the ridge/hip covering element according to the invention. According to one embodiment of the invention, the ventilation insert can therefore be made of sheet metal or plastic, in particular the ventilation insert can be formed from a bent sheet metal part which is inserted resiliently into the ridge/hip covering element.

[0011] There are no restrictions on the design of the ventilation insert other than fulfilling the ventilation and spacer function.

[0012] According to a further embodiment of the invention, the ventilation insert can have at least one longitudinal outer wall with first ventilation openings so that air can circulate between a roof interior and the environment.

[0013] In a further embodiment of the invention, the at least one longitudinal outer wall can form a peripheral support edge for support on the roof covering elements arranged in the region of the ridge/hip, thereby enabling stable support of the ventilation insert on the roof covering elements and secure positioning of the ridge/hip covering element according to the invention.

[0014] In order to avoid shear stress on the roof covering elements, in a further embodiment of the invention the at least one longitudinal outer wall can be oriented such that, in the installed state of the ridge/hip covering element, it runs at a right angle to the roof covering elements arranged in the region of the ridge/hip.

[0015] According to a further variant of the invention, the at least one longitudinal outer wall can form an insertion engagement edge for inserting the ventilation insert into the ridge/hip stone, so that the ventilation insert can be inserted into the ridge/hip stone with this insertion engagement edge in order to bring about the positive and/or frictional connection with it.

[0016] In order to prevent moisture or foreign bodies from penetrating the interior of the roof during extreme weather conditions such as storms, driving rain or snowdrifts, according to a further embodiment of the invention the ventilation insert can have at least one longitudinal intermediate wall inclined relative to the longitudinal outer wall with second ventilation openings.

[0017] In a further embodiment of the invention, the at least one longitudinal outer wall and the at least one inclined longitudinal intermediate wall can be connected to one another by a connecting wall with an L-shaped profile. This results in even better repellency of particles, droplets, snow, etc. penetrating from the outside.

[0018] In addition, according to a further embodiment of the invention, the at least one inclined partition wall can form a central bearing edge for support on the ridge/hip stone, so that no separate element has to be provided for this purpose.

[0019] A symmetrical design of the ridge/hip cover element according to the invention is preferred for reasons of universal applicability.

[0020] In a further embodiment of the invention, the ridge/hip covering element can therefore have a longitudinal center plane which, when installed, is separated by an uppermost ridge/hip edge.

runs, whereby the ridge/hip cover element is designed symmetrically to the longitudinal center plane.

[0021] In this context, it may be advantageous that the at least one longitudinal outer wall is formed by a first and a second longitudinal outer wall which are arranged symmetrically to the longitudinal center plane, and the at least one inclined longitudinal intermediate wall is formed by a first and a second longitudinal intermediate wall which are arranged symmetrically to the longitudinal center plane.

[0022] In a further embodiment of the invention, the ridge/hip cover element can - seen in cross section - have an arcuate central section, at the opposite ends of which slanted side parts are formed, so that an obtuse angle is formed at the transition points between the ends of the arcuate central section and the slanted side parts on the inside of the ridge/hip stone, so that insertion engagement positions are formed at these transition points, which enable the ventilation insert to be inserted and engaged.

[0023] When laying the roof, a sufficient number of ridge/hip covering elements are lined up in a row in the longitudinal direction of the ridge or hip, depending on the length of the roof, whereby adjacent covering elements must be arranged in such a way that no precipitation can penetrate into the interior of the roof.

[0024] In order to achieve a flush and at the same time sealing closure of the ridge/hip covering elements according to the invention, according to a further embodiment of the invention, a tapered covering area can be formed at a longitudinal end of the ridge/hip stone, on the outside of which at least two spaced-apart sealing beads are formed or applied, which run parallel to the front end of the covering area, wherein in the covered state, successive ridge/hip stones in the longitudinal direction are flush with one another.

[0025] In order to fasten adjacent ridge/hip stones in the longitudinal direction with little effort, only one longitudinal end can be fixed to the roof at a time and the opposite longitudinal end of the adjacent ridge/hip stone can be fixed by engaging it with the end region of the ridge/hip stone already fixed to the roof.

[0026] In this regard, a variant of the invention can consist in that the end of the ventilation insert is set back at the longitudinal end of the ridge/hip stone opposite the covering area and has a protruding tab that can be brought into engagement with the ventilation insert of the longitudinally adjacent ridge/hip stone in order to hold the ridge/hip stone down in the covered state. This form of fixation has the advantage that it does not impair the external appearance of the ridge or hip top edge.

[0027] Another variant of the invention can consist in that in the overlapping area of the ridge/hip stone, by attaching a ridge clamp, the longitudinally adjacent ridge/hip stone can be inserted into the ridge clamp and fixed with the longitudinal end opposite to its overlapping area when covering. As a result, one end area of the adjacent ridge/hip stone is held directly by the clamp of the end area of the ridge/hip stone that is already fixed to the roof, resulting in a very secure attachment to the roof.

[0028] Furthermore, the invention relates to a fastening arrangement with a ridge/hip covering element according to the invention, wherein it is provided according to the invention that a screw spring strip element is provided with which the ridge/hip stone and the ventilation insert are brought into engagement together with a supporting batten of a roof. In contrast to the prior art, fastening to the ridge/hip stones is avoided here and this is carried out on the supporting batten, whereby the load on the uppermost ridge/hip stones is reduced.

[0029] According to a further embodiment of the invention, it can be provided that the spring strip element is oriented transversely to the longitudinal axis of the screw element and has barbs at its ends as anti-twist protection in order to enable a secure fixing of the ridge/hip stone together with the ventilation insert.

[0030] The invention is explained in detail below with reference to the embodiments shown in the drawings. It shows

[0031] Fig. 1 is a cross-section through an embodiment of a ridge/hip covering element according to the invention mounted on a roof;

[0032] Fig.2 shows a cross section through another embodiment of a

ridge/hip covering element according to the invention mounted on a roof;

[0033] Fig.3, 4, 5, 6 and 7 show a side view, top view, detail view, oblique view and cross section of the ridge/hip stone of the embodiment according to

Fig. 1;

[0034] Fig. 8 shows a cross section of the ridge/hip covering element according to Fig. 1 with fastening elements;

[0035] Fig. 9 a cross-section of the ridge/hip covering element according to Fig. 2

with fastening elements;

[0036] Fig.10 and 11 show a front and a side view of ridge/hip cover elements mounted on the roof according to Fig.1 with a variant of a fastening arrangement according to the invention;

[0037] Fig.12 shows a detail according to Fig.11;

[0038] Fig.13 and 14 show a front and a side view of ridge/hip cover elements mounted on the roof according to Fig.1 with a further variant of the fastening arrangement according to the invention; and

[0039] Fig.15 a detail according to Fig.14.

[0040] Fig.1 shows the upper part of a roof 3 covered in a known manner with rafters 100, a wooden formwork 101, a preliminary covering 102, a counter batten 103 and a supporting batten 104. Roof covering elements 2 are fastened to the supporting batten 104, which are made of fiber cement, but are not limited to this material.

[0041] Within the scope of the invention, however, a roof covering can also be carried out on the wooden formwork.

[0042] The gap between two upper roof side ends that is created during roof covering is closed off by a ridge/hip covering element 1 attached to the top of the roof 3 with a half-shell-like curved ridge/hip stone 10, whereby the ridge/hip covering element 1 serves to form a roof ridge 5 as shown in Fig.1, but it can also form a roof ridge with a ridge stone.

[0043] Fig.3 to 7 show longitudinal views and a cross section BB of the ridge/hip stone 10 shown in Fig.1.

[0044] According to the invention, the ridge/hip covering element 1 comprises a ventilation insert 4 which is inserted in a force-fitting and/or form-fitting manner on the inside of the ridge/hip stone 10 and which, when the ridge/hip covering element 1 is installed, creates a ventilation gap 6, 7 on both sides of the roof 3 between the ridge/hip stone 10 and the roof covering elements 2 arranged in the area of the ridge 5 and forms ventilation communication between a roof interior 109 and an environment 11, whereby air from the roof interior 109 can penetrate into the environment 11 along paths shown by looped arrows 70, 71 or, conversely, air can also flow from the outside to the inside.

[0045] The ventilation insert 4 is designed such that it is already inserted into the ridge/hip stone 10 during the manufacture of the ridge/hip cover element 1 according to the invention, whereby there are no restrictions on the type of fixation to the ridge/hip stone 10 and this can be done, for example, by gluing, clamping, snapping or the like.

[0046] The ridge/hip covering element 1 according to the invention has a longitudinal center plane 24 which, when installed, runs through an uppermost ridge/hip edge, the ridge/hip covering element 1 being designed symmetrically to the longitudinal center plane 24. However, within the scope of the invention, an asymmetrical shape of the ridge/hip covering element 1 could also be provided.

[0047] The ridge/hip stone 10 is - like the roof covering elements 2 - preferably made of fiber cement, but can also be made of other equivalent materials.

[0048] There are also no restrictions on the shape of the ridge/hip stone 10; in the embodiment shown in Fig. 1, the ridge/hip stone 10 has - seen in cross section - an arcuate central section 25, e.g. in the form of a circular segment, at the opposite ends of which slanted side parts 26, 27 are formed, so that an obtuse angle a is formed at the transition points between the ends of the arcuate central section 25 and the slanted side parts 26, 27 on the inside of the ridge/hip stone 10, wherein the ventilation insert 4 is engaged in these transition points, so that the ventilation insert 4 is connected to the ridge/hip stone 10.

[0049] In the manufacture of the ridge/ridge cover element 1 according to the invention, the ridge/ridge stone 10 is first formed with the profile shown in Fig. 1, e.g. by injection molding, and then the ventilation insert 4 is inserted into this ridge/ridge stone 10.

[0050] The ventilation insert 4 is formed from a bent sheet metal part, but can also be made of other, equivalent materials, and in the embodiment shown in Fig.1 is inserted resiliently into the ridge/hip stone 10.

[0051] The ventilation insert 4 has a first and a second longitudinal outer wall 8, 9 with first ventilation openings 12, 13, each symmetrical to the longitudinal center plane 24, so that air can circulate between the roof interior 109 and the environment 11.

[0052] The first and the second longitudinal outer walls 8, 9 each form a peripheral support edge 14, 15 in the lower region for supporting the roof covering elements 2 arranged in the region of the ridge 5.

[0053] During assembly, the ridge/hip covering element 1 according to the invention is placed with the support edges 14, 15 on the upper roof covering elements 2 and the ridge/hip covering element 1 is fixed with nails, screws or the like, e.g. on a ridge batten (not shown).

[0054] When the Firs’Grat covering element 1 is installed, the longitudinal outer walls 8, 9 of the ventilation insert 4 run approximately at a right angle to the roof covering elements 2 arranged in the area of the ridge/hip 5.

[0055] In the upper region, the longitudinal outer walls 8,9 each form an insertion engagement edge 16, 17 for inserting the ventilation insert 4 into the ridge/hip stone 10 during the manufacturing process.

[0056] To reduce weather influences such as driving rain or snowstorms, the ventilation insert 4 has two longitudinal intermediate walls 18, 19 inclined by approximately 70° relative to the longitudinal outer walls 8, 9 with second ventilation openings 20, 21, whereby the looped air guide path shown in Fig.1 by the arrows 70, 71 is created, which prevents rain or snow from being introduced into the roof interior 109 from the outside.

[0057] The two inclined longitudinal partition walls 18, 19 arranged symmetrically to the central plane 24 are connected to each other at their upper ends and form a central bearing edge 22 at this connection point for support on the ridge/hip stone 10.

[0058] The longitudinal outer walls 8, 9 and the inclined longitudinal intermediate walls 18, 19 are connected to each other by connecting walls with L-shaped profile 200, 210, thereby preventing particles and/or drops from entering the roof interior 109.

[0059] Fig.2 shows a further embodiment of the ridge/hip covering element 1 according to the invention with the ventilation insert 4', whereby, in contrast to the embodiment according to Fig. 1, profiled roof covering elements 2' are used for roof covering and therefore the

The arrangement of the walls of the ventilation insert 2 is slightly different from Fig.1.

[0060] Fig.3 to 7 show the ridge/hip stone 10 used in Fig.1 and 2 in a longitudinal view, wherein a step-shaped tapered covering area 30 is formed at one longitudinal end on the weather side of the ridge/hip stone 10, on the outside of which spaced-apart sealing beads 31, 32, 33, 34 are formed or applied, which run parallel to the front end of the covering area 30, so that in the covered state, successive ridge/hip stones in the longitudinal direction are flush with one another and, for example, a horizontal uppermost ridge/hip line is created. For production-technical reasons, the step-shaped transition to the tapered covering area 30 is provided with a slope.

[0061] Fig.8 and 9 show a variant of a fastening arrangement of the ridge/hip stone 10 for the ventilation inserts 4, 4' according to the embodiments shown in Fig.1 and 2.

[0062] For fastening to the roof 1, a screw-spring strip element 120, 121 formed from a screw 120 and a spring strip element 121 is provided in Fig.8 for each ridge/hip stone 10, with which the ridge/hip stone 10 and the ventilation insert 4 are brought into engagement together with the supporting battens 104 of the roof 1. The screw 120 runs from above through the apex of the cross-section of the ridge/hip stone 10 and the upper support edge 22 of the ventilation insert 4 along the longitudinal center plane 24 downwards to the height of the support battens 104, where the spring strip element 121 oriented transversely to the longitudinal axis of the screw 120 rests on the underside of the two uppermost battens of the support battens 104 and is tightened by a threaded section of the screw 120 that engages in a threaded hole of the spring strip element 121. The spring strip element 121 has barbs 131, 132 at its ends to prevent rotation, which are clawed into the underside of the two upper battens when the ridge/hip stone 10 is screwed tight.

[0063] Fig.9 shows this fastening arrangement for the profiled roof covering elements 2' of the embodiment according to Fig.2, which are screwed to the support battens 104 with screws 170. The ridge/hip stone 10 with its ventilation insert 4' arranged on the underside is fastened to the support battens 104 via the screw spring strip element 120, 121.

[0064] Fig.10, 11 and 12 show the ridge/hip stones 10, 10' fastened with a fastening arrangement according to Fig.8 and 9, which have a ventilation insert 4 according to the invention inserted on their inner side.

[0065] Fig.12 shows in detail the covering area 30 of the ridge/hip stone 10 and an end 39 of the longitudinally adjacent ridge/hip stone 10' opposite the covering area, the ventilation insert 4' of which is set back by the length of the covering area 30 and has a protruding tab 151 which can be brought into engagement with the ventilation insert 4 of the ridge/hip stone 10 by moving the ridge/hip stone 10' in the direction of the arrow in order to hold the ridge/hip stone 10' down at this end in the covered state, whereupon its covering area (not shown in Fig.12) can be screwed tight at the opposite end in the same way as the ridge/hip stone 10.

[0066] Fig. 13, 14 and 15 show a further variant of the fastening arrangement according to the invention, whereby in the overlap area 30 of the ridge/hip stone 10 by attaching a ridge clamp 160 in the form of a hook-shaped bent sheet metal part, the longitudinally adjacent ridge/hip stone 10' can be inserted and fixed in the ridge clamp with the longitudinal end 39 opposite to its overlap area when covering it. The ridge clamp 160 is designed in such a way that it is placed on the outside of the ridge/hip stone 10 and screwed in during the fastening process with the screw spring strip element.

Claims (18)

patent claims 1. Ridge/hip covering element (1) with a ridge/hip stone (10) for attachment to a ridge (5) or ridge of a roof (3) covered with roof covering elements (2, 2"), characterized in that the ridge/hip covering element (1) comprises a ventilation insert (4, 4') which is factory-mounted on the inside of the ridge/hip stone (10) and inserted in a force-fitting and/or form-fitting manner and is designed such that, when the ridge/hip covering element (1) is installed, it creates a ventilation gap (6, 7) between the ridge/hip stone (10) and the roof covering elements (2, 2') arranged in the area of the ridge/hip (5) and forms ventilation communication between a roof interior (109) and an environment (11). 2. Ridge/hip covering element according to claim 1, characterized in that the ventilation insert (4, 4') has at least one longitudinal outer wall (8, 9) with first ventilation openings (12, 13) so that air can circulate between the roof interior (109) and the environment (11). 3. Ridge/hip covering element according to claim 1 or 2, characterized in that the at least one longitudinal outer wall (8, 9) of the ventilation insert (4) forms a peripheral support edge (14, 15) for supporting the roof covering elements (2) arranged in the region of the ridge/hip (5). 4. Ridge/hip covering element according to one of claims 1 to 3, characterized in that the at least one longitudinal outer wall (8, 9) in the laid state of the ridge/hip covering element (1) runs at a right angle to the roof covering elements (2) arranged in the region of the ridge/hip (5). 5. Ridge/hip covering element according to one of claims 1 to 4, characterized in that the at least one longitudinal outer wall (8, 9) forms an insertion engagement edge (16, 17) for inserting the ventilation insert (4) into the ridge/hip stone (10). 6. Ridge/hip covering element according to one of claims 1 to 5, characterized in that the ventilation insert (4) has at least one longitudinal intermediate wall (18, 19) inclined relative to the longitudinal outer wall (8, 9) with second ventilation openings (20, 21). 7. Ridge/hip covering element according to one of claims 1 to 6, characterized in that the at least one longitudinal outer wall (8, 9) and the at least one inclined longitudinal intermediate wall (18, 19) are connected to one another by a connecting wall with an L-shaped profile (200, 210). 8. Ridge/hip covering element according to one of claims 1 to 7, characterized in that the at least one inclined intermediate wall (18, 19) forms a central bearing edge (22) for support on the ridge/hip covering element. 9. Ridge/hip covering element according to one of claims 1 to 8, characterized in that the ridge/hip covering element (1) has a longitudinal center plane (24) which, in the laid state, runs through an uppermost ridge/hip edge, and that the ridge/hip covering element (1) is designed symmetrically to the longitudinal center plane (24). 10. Ridge/hip covering element according to claim 9, characterized in that the at least one longitudinal outer wall is formed by a first (8) and a second (9) longitudinal outer wall which are arranged symmetrically to the longitudinal center plane (24), and that the at least one inclined longitudinal intermediate wall is formed by a first (18) and a second (19) longitudinal intermediate wall which are arranged symmetrically to the longitudinal center plane (24). 11. Ridge/hip covering element according to one of claims 1 to 10, characterized in that the ridge/hip stone (10) - seen in cross section - has an arcuate central section (25), at the opposite ends of which inclined side parts (26, 27) are formed, so that an obtuse angle (a) is formed at the transition points between the ends of the arcuate central section (25) and the inclined side parts (26, 27) on the inside of the ridge/hip stone (10). 71717 12. Ridge/hip cover element according to one of claims 1 to 11, characterized in that the ventilation insert (4) is made of sheet metal or plastic. 13. Ridge/hip covering element according to one of claims 1 to 12, characterized in that the ventilation insert (4) is formed from a bent sheet metal part which is resiliently inserted into the ridge/hip stone (10). 14. Ridge/hip covering element according to one of claims 1 to 13, characterized in that a tapered covering region (30) is formed on a longitudinal end of the ridge/hip stone (10), on the outside of which at least two spaced-apart sealing beads (31, 32, 33, 34) are formed or applied, which run parallel to the front end of the covering region (30), wherein in the covered state, successive ridge/hip stones in the longitudinal direction are flush with one another. 15. Ridge/hip covering element according to claim 14, characterized in that at the longitudinal end of the ridge/hip stone (10') opposite the covering area (30), the end of the ventilation insert (4) is set back and has a protruding tab (151) which can be brought into engagement with the ventilation insert (4) of the longitudinally adjacent ridge/hip stone (10) in order to hold down the ridge/hip stone (10') in the covered state. 16. Ridge/hip covering element according to claim 14, characterized in that in the covering area (30) of the ridge/hip stone (10) by attaching a ridge clamp (160) the longitudinally adjacent ridge/hip stone (10') can be inserted and fixed in the ridge clamp (160) when covering with the longitudinal end opposite to its covering area. 17. Fastening arrangement with a ridge/hip covering element according to one of the preceding claims 1 to 16, characterized in that a screw spring strip element (120, 121) is provided, with which the ridge/hip stone (10) and the ventilation insert (4) are brought into engagement together with a supporting batten (104) of a roof. 18. Fastening arrangement according to claim 17, characterized in that the spring strip element (121) is oriented transversely to the longitudinal axis of the screw element (120) and has barbs (131, 132) at its ends as anti-twist devices. 9 sheets of drawings