DE9100658U1 - Screw for fastening flexible materials to a base layer at risk of thread damage - Google Patents

Description

Screw for fastening flexible materials to a thread at risk of damage

Base layer

The subject of the innovation is a screw for fastening more or less flexible materials, preferably insulating and/or insulating materials, to a supporting layer at risk of thread damage, preferably made of concrete or aerated concrete, with a screw shaft that has a supporting thread for screwing into the supporting layer and an engagement section for a turning tool with a lower contact surface for contact with the flexible material.

Screw fastenings, especially of insulation layers

Patent Attorneys · European Patent Attorneys · Authorized Representatives before the European Patent Office Attorney: admitted to the Hamburg courts

Deutsche Sank AC- HpKbürg: Ni'£J5/2Si97=^LZ?iÖQ 7G.Q 0°!' Poslgiro Hamburg 28 42-206 Dresdner ßanfc AP I;ja&ib3r j," NSr. 932C6ÖJ5S (BLZ 200 800 OPI

with a roof covering on roofs made of concrete or aerated concrete are at risk of thread damage caused by over-tightening the screw in the brittle and less durable material of the base layer. Similar problems occur, for example, when fastening wooden parts to metal sheets. As soon as :■ the attack section with its contact surface

.V... · _ rests on the flexible material , is supported by the

>, ' screw shaft a force is introduced into the supporting thread,

i'l which can lead to thread destruction. This force increases

i. , /'- with the screw-in depth. The above effects ^are not only caused by particularly brittle base layers , especially made of aerated concrete or masonry, but also by re-

relatively rigid materials such as polystyrene are required, t
f where the pull-out force increases with increasing screw-in depth

" ^f rises particularly steeply. Therefore, conventional

Dowel fastenings for insulating materials on aerated concrete base layers are mainly used.

Y ₁ ' From the &Xgr;&Rgr;-&Agr;-0 394 604 is already a thread-forming

Screw of the type mentioned above has become known,

which has a first and a second thread

-. Bind, which extends almost over the entire length of the shaft.

- stretch, whereby the tip diameter of the first thread

^¥ ' thread decreases evenly from the head end to the inlet end, the thread with the larger tip diameter

has circumferentially spaced increments and the tip diameter of the second thread essentially corresponds to the diameter of the pre-drilled hole into which the screw can be inserted. At the same time, the publication discloses a method for forming a thread using the screw, whereby the screw is set in rotation in pulses using a motorized screwing tool. This screw does indeed have all the properties required to securely fasten an object to a component, i.e. it can be driven into a drill hole to any screw depth using moderately high torques, forming a thread, without being subjected to undue stress, and it nevertheless takes up a secure seat in the drill hole that ensures a high pull-out torque. In the case of vulnerable base layers, thread damage can still occur after the engagement section has been created before the screwing process is aborted.

Based on this, the innovation is based on the task of creating an improved screw of the type mentioned above, which reduces the risk of damage to the base layer thread.

To solve this problem, the new

Il ■ · · * .

The screw mentioned above is provided with a contact surface | provided with radial ribs, that a screw guided inside the screw shaft rests against the contact surface with a counter-contact surface, and that the counter-contact surface has corresponding radial grooves for receiving the ribs.

The washer significantly increases the effective contact surface of the screw on the flexible material, so that a better secured fastening and a more uniform force transfer are achieved. At the same time, the radial ribs of the contact surface of the engaging section and the corresponding radial grooves of the counter-contact surface of the washer create a locking mechanism that prevents the screw from being screwed further into the supporting layer before a dangerous pull-out force can build up. The prerequisite for this is that the washer is of a sufficient size, which, in conjunction with the friction on the flexible material, prevents it from turning after the ribs have engaged in the grooves, at the latest when the screw pull-out force approaches a critical value. With a screw in line with the innovation, even a slightly flexible material layer can be reliably fastened to a supporting layer that is at considerable risk of damage.

&igr;&ogr;&igr; ·

An impact wrench can even be used, which switches off immediately when the engaging section and the disk are locked due to the suddenly increased torque.

According to one embodiment, the contact surface of the engaging section and the counter-contact surface of the [disk taper conically towards the screw shaft, so that a relatively large contact surface and a good mutual locking of the engaging section and disk result. An outstanding locking effect is achieved if, according to a further development, the contact surface has six ribs and the counter-contact surface has six corresponding grooves ! for receiving the ribs.

According to a further development, the disk has a pot-like recess to accommodate the gripping section. This means that the gripping section can be completely sunk into the disk and is still accessible for gripping a tool.

Furthermore, the disc advantageously has a circumferential bead on the underside, which, when the screw is tightened, rests against the flexible material with increased line pressure and counteracts rotation of the disc.

Preferably , the disk is approximately rectangular and its transverse and longitudinal dimensions exceed the diameter of the screw shaft by several times, in particular by five times. The rectangular shape counteracts any undesirable rotation of the disk. Furthermore, the size ratios result in the desired uniform transfer of force between the screw and the underlying material layer, which also prevents the disk from rotating when the locking mechanism takes effect. For this purpose, the transverse dimensions are preferably approximately half the longitudinal dimensions.

However, even with a round shape, rotation of the disc can be counteracted by claws on the underside.

Particularly for manufacturing reasons, a threadless cylindrical shaft section can be formed between the supporting thread and the engaging section. Preferably, the screw shaft has a disk thread section next to the engaging section, which enables the disk to be screwed on, and an annular rotation groove for the disk is formed on the screw shaft between the disk thread section and the engaging section. The disk thread section enables the disk to be pre-assembled.

• I »

on the screw, which can rotate relative to the disc when screwed into the base layer due to the annular groove.

It goes without saying that the rotation groove is wide enough to allow rotation before the ribs engage in the grooves. At the same time, the disc thread section supports the disc on the screw shaft, which, for example, makes it easier to walk on a layered structure.

According to a practical development, the supporting thread has a first and a second thread that extend almost over the entire length of the shaft, with the tip diameter of the first thread decreasing evenly towards the free end, the thread with the larger tip diameter having incisions spaced apart in the circumferential direction and the tip diameter of the second thread essentially corresponding in diameter to the pre-drilled hole into which the screw can be inserted. This enables the thread to be formed with a significantly reduced risk of damage, even if the screwing in is carried out in pulses using a motorized screwing tool. Advantageously, the tip diameter of the thread with the larger tip diameter reaches a

•#

• *

Fig. 2 a modified screw with external attack surface without washer in plan view;

Fig. 3 Ribs of the same screw in enlarged cross-section;

Fig. 4 the same screw in a section along the line IV-IV of Fig. 1;

up to three thread pitches. This means that a high extraction value is achieved even with a relatively low screw-in depth.

Finally, according to one embodiment, a rod tip is provided at the free end of the screw shaft, which facilitates the driving of the screw into an inaccurately prefabricated hole.

tion is made easier.

^Further details and advantages of the innovation are apparent from the following description of the accompanying drawings, which show a preferred embodiment of the invention.

-,show the screw according to the invention. In the drawings show: -5

Fig. 1 a thread-forming screw with internal attack surface and nail point in side view; ty

-S-

Fig. 5 The same screw in the fastening of an insulation layer to a concrete layer in cross section.

The screw 1 for a concrete layer shown in Fig. 1 has an engagement section 2 with a not shown

-th internal engagement surface for a tool as well as a so-called nail point 4. Fig. 2 shows a top view of a slightly modified screw with an external hexagon 3 for the tool engagement. The screw shaft 5 has a supporting thread 6 adjacent to the nail point 4, next to it a threadless cylindrical shaft section 7 and a

3: bordering disc thread 8. A torsion groove 9 is formed between disc thread 8 and engagement section 2.

The supporting thread 6 is double-started and has a first thread 10 and a second thread 11, the latter having a larger diameter than the former. The diameter of the first thread 10 corresponds to the diameter of a core hole that is pre-drilled in concrete or a similar material into which the screw 1 is to be screwed. The counter thread in the wall of the core hole or core bore is therefore only created by the thread 11, while the thread 10 has an exclusively centering effect. In aerated concrete, the screw 1 is screwed in without a pre-drill.

.../10

- 1Ü -

As can be seen better from Fig. 4, the thread 11 has notches 12 which serve for clearing purposes. Furthermore, it can be seen from Fig. 1 that the tip diameter of the thread 11 is somewhat smaller near the tip 4. It gradually increases from the tip 4, but after two pitches ^it already reaches the

^ iji V- 'Outer diameter which it has throughout its remaining X ^ "" course.

Fig. 1 and 3 show that the engagement section 1 has ribs with an acute angle cC of approximately 100° on a contact surface 13 which is conically inclined towards the screw shaft 5. Six of these are evenly distributed over the circumference of the screw.

The twisting groove 9 is inserted into a central bore 15 of a disk 16, which has a conical counter-contact surface 17 for the contact surface 13. Radially extending grooves 18 are incorporated into the counter-contact surface 17, which correspond to the ribs 14 and accommodate them in the locking position shown. If the disk 16 is lowered slightly in the twisting groove 9, it can rotate freely relative to the screw shaft 7. On the outside, the disk 16 is provided with a circumferential and downwardly projecting bead 19.

.../11

V: :K

The disc gets into the twist groove 9 by turning it over the supporting thread 10, 11, pushing the cylindrical shaft section and turning it over the disc thread 8 until it reaches the twist groove 9. The outside diameter of the disc thread 8 exceeds that of the supporting thread 10, 11/ so that the disc 16 can be easily conveyed to the disc thread 8 and held securely in the twist groove 9 by it. The supporting thread 6 and the disc thread 8 rise in the same direction so that the disc 16 cannot accidentally move out of the twist groove 9 when the supporting thread 10, 11 is screwed in and rests against the layer to be fastened. The insulation layer 20 is also provided with a hole 23 for the screw 1 when the core hole 22 is drilled in concrete.

For the function of the screw 1 according to the invention, reference is made to Fig. 5, which shows the fastening of an insulating layer 20 to a concrete supporting layer 21. The supporting layer 21 has a pre-drilled core hole 22, the diameter of which corresponds approximately to the diameter of the first thread 10. The second thread 11 has created a counter thread in the supporting layer.

The engaging section 2 is locked via its ribs 14 with the grooves 18 of the disk 16. The plate 16 is

.../12

on the insulation layer 20 or a roof covering placed on top, whereby the bead 19 digs into the insulation layer 20. Together with the rectangular shape

&iacgr; of the disc 16 this causes a considerable resistance

against twisting on the insulation layer. As soon as the screw 1 is locked with its washer 16, it is

is therefore prevented from screwing further into the supporting layer 21, thereby preventing the build-up of a tear-out force that could destroy the formed thread.

Claims (1)

ti« · · If III * · * * · - 13 A &eegr; s &rgr; r ü he 1. Screw for fastening flexible materials (20), preferably insulation and/or insulating materials, to a supporting layer (21) at risk of thread damage, preferably made of concrete or aerated concrete, with a screw shaft (5) which has a supporting thread (6) for screwing into the supporting layer and an engagement section (2) for a turning tool with a lower contact surface (13) for contact with the flexible material, characterized in that the contact surface (13) is provided with radial ribs (14), that a disk (16) guided inside the screw shaft (5) with a counter contact surface (17) rests on the contact surface, and that the counter contact surface has radial grooves (18) for receiving the ribs. 2. Screw according to claim 1, characterized in that the contact surface (13) of the engagement section (2) and the counter-contact surface (17) of the disk (16) taper conically towards the screw shaft (5). 3. Screw according to one of claims 1 or 2, characterized in that the contact surface (13) has six ribs (14) and the counter-contact surface (17) has six corresponding .../14 ding grooves (18) for receiving the ribs. Jg'
4vi Screw according to one of claims 1 to 3, characterized in that the disk (la) has a hollow-like recess for receiving the engaging step (2). 5. Screw according to one of claims 1 to 4, characterized in that the disc (16) has a circumferential bead (19) on the underside. 6. Screw according to one of claims 1 to 5, characterized in that the disc (16) is approximately rectangular and its transverse and longitudinal dimensions correspond to the diameter - diameter of the screw shaft (5) by several times, in particular by five times. 7. Screw according to claim 6, characterized in that the transverse dimensions of the disc (16) are approximately half of its longitudinal dimensions. 8. Screw according to one of claims 1 to 7, characterized in that the disc has claws on its underside. ,../15 III &igr;&igr; ·· * · · ·· Il IJI · &bgr; . -»» ·· ··· ♦♦ 9. Screw according to one of claims 1 to 8, characterized in that a threadless cylindrical shaft section (7) is formed between the supporting thread (6) and the engagement section (2). 10. Screw according to one of claims 1 to 9, characterized in that I indicates that the screw shaft (5) is located next to the &igr; engaging portion (2) has a disc thread (8) which ~Γ f allows the disc (16) to be screwed on, and that * between the disc thread (8) and the engaging section (2) ' _f * an annular torsion groove (9) for the disc (16) ^r ' j is formed on the screw shaft (5). >£ 11. Screw according to one of claims 1 to 10, characterized in that the supporting thread (6) has a first and . J a second thread (10, 11) which extend ^almost over the entire length of the shaft, the 1 tip diameter of the first thread (10) being
decreases evenly towards the free end, the thread
(11) having the larger tip diameter in the circumferential direction spaced incisions (12) and \ the tip diameter of the second thread (11) \ substantially in the diameter of the pre-drilled bore i,
tion into which the screw can be inserted. .../16 12. Screw according to claim 11, characterized in that seen from the free end, the tip diameter of the thread (11) with the larger tip diameter reaches its final value after one to three thread pitches. "— J. . S e 13'. Screw according to one of claims 1 to 12, characterized in that a nail tip (4) is provided at the free end of the screw shaft (5).