DE102021126035A1 - wood screw - Google Patents

Abstract

A wood screw (1) is presented, which comprises a screw shank (2), which has a screw head (3) and a screw tip (4) on the side opposite the screw head (3), with at least one to threaded section (5, 6, 7, 8) running towards the screw tip (4).
The invention is characterized in that a thread root (10) is formed between the thread flanks (9) of the thread section (5) of the screw tip (4) and has a concave groove (11) in the longitudinal direction of the screw shank (2).

Description

The invention relates to a wood screw according to the preamble of patent claim 1.

Wood screws are slightly conical and are mainly screwed into wood, in which they cut a mating thread. The specific material properties of wood require special attention when designing such wood screws, since wood tends to splinter due to its fiber structure. Wood screws of the type in question comprise a screw shank which has a screw head and a screw tip on the side opposite the screw head. The tip of the screw is usually designed like a needle or nail, i.e. designed as a tip in the true sense of the word, in order to allow the screw to pierce the comparatively softer wood-based material before screwing in, and thus to fix the wood screw in the wood. In the case of wood screws, at least one threaded section extending up to the tip of the screw and thus a thread extending up to the tip of the screw is formed on the screw shank. Previously known wood screws can have differently designed threaded sections along the screw shank, as well as unthreaded sections and/or a continuous thread from the screw head to the screw tip.

The EP 2 224 142 B1 discloses a thread-forming screw with a pre-thread present at the screw tip. In the area of the pre-thread, several chip pockets are distributed along the circumference, so that the cross-sectional shape of the screw shank in this area has a geometry that deviates from the circular-cylindrical shape. The pre-thread is also divided into several thread segments in the area of the chip pockets.

In DE 33 37 534 A1 describes a universal screw that can be used for wood-based materials and has a thread pitch that extends to the tip of the screw. Viewed in the circumferential direction, the screw tip has discontinuous, in particular convex and concave shaped sections following one another.

From the DE 93 07 816 U1 discloses a screw for wood-based materials, which has a flute running in the longitudinal direction of the screw on a screw tip section on two opposite sides. The chip flutes extend over several thread turns of the thread present in the area of the screw tip section and intersect the thread turns. The chip flutes have in the side view, as in the 2 shown is a trough-shaped concave shape.

The EP 3 040 563 B1 discloses a wood screw with a root between two threads. In particular from the 6 it can be seen that in the area of the thread root there is a discontinuity in the form of a kink with an inclined section or a stepped groove. When screwing in, displaced material from the subsoil is conveyed into the discontinuity.

A self-tapping drilling screw goes beyond that EP 0 012 441 A1 out. The self-drilling screw has a cylindrical base body with threads in the holding part. A constriction is provided in the thread root between the threads, wherein, starting from the flanks of the threads, an overall conical or roof-shaped bevel is provided to form the constriction. The bevels converge at a sharp angle in the area of the constriction.

The DE 699 15 254 T2 describes a bone screw which has a cylindrical shank and a threaded section which tapers or tapers towards the tip. At the root of the thread, i.e. between two adjacent threads, there is a defined profile that is also conical. This design makes it possible to keep the specific pressure under load and the torque when screwing in low.

In the WO 2020/060902 A1 discloses a screw in which a helical indentation is provided in the shank between the threads, which is rounded off into separate, flat edge regions.

Out of U.S. 2008/008953 A1 Finally, a screw emerges that is particularly suitable for plastics and has a shank and an adjoining screw tip that tapers to a point. A thread is provided, which runs from the tip of the screw with the tapering section to the cylindrical shank to a screw head. Between two turns of the thread there is a constriction, which is formed by two flanks of the thread root running towards one another and having a conical course. The constriction is also present in the area of the screw tip.

Ultimately, the DE 10 2017 208 282 A1 a wood screw with a thread running along the cylindrical shank. there is only a central area between two flanks of the thread is concave with a radius R, which is followed by inclined surfaces on both sides. This is a particularly stretchable screw.

The object of the invention is to provide a wood screw whose screwing torque is low, whose screwing behavior is constant and which can be optimally centered at the screwing point, thereby improving the screwing process overall and saving time when assembling wooden components.

The invention solves this problem with the features of patent claim 1.

Further configurations of the invention are the subject matter of the subsequent dependent claims.

A wood screw with a screw shank, which has a screw head and a screw tip on the side opposite the screw head, with at least one threaded section running up to the screw tip being formed on the screw shank, was further developed according to the invention such that there is a thread base between the thread flanks of the threaded section of the screw tip is formed, which has a concave groove in the longitudinal direction of the screw shank.

In other words, the invention is such that a concave constriction is formed between two flanks of the thread of the screw tip that are arranged side by side in the side view of the wood screw. The invention thus relates to the concave, i.e. inwardly curved core diameter of the screw tip, which decisively favors screwing in and centering, also known as “biting”, of the wood screw at the screwing point. Since the screwing-in time also largely depends on the "bite" of the screw, the new design of the screw tip also offers a corresponding advantage. When screwing in, wood screws displace the wood material, which in the case of a wood screw according to the invention means that the volume of the wood material to be displaced is smaller and the torque to be applied in the screwing bevel is reduced. The cutting of the thread flanks and its "screw pull-in force" is optimized so that deeper penetration and continuous and stable screwing behavior of the wood screw is achieved. As a result of the concave groove, viewed from the screw tip in the direction of the screw head, the increase in the core diameter is accompanied by a reduction in the wedge effect, so that the wood screw exerts less of a splitting effect on the wood-based material. The invention consequently provides a wood screw whose screwing torque is low, whose screwing behavior is constant and which can be optimally centered at the screwing point, thereby improving the screwing process overall and saving time when assembling wooden components.

According to a first embodiment of the invention, it is proposed that the concave groove has a radius R for which, based on the nominal diameter d of the thread of the wood screw, the following applies: d/R=1.2 to 2.0. Preferably the ratio d/R=1.714. To give an example of this, assume that the nominal diameter of the bolt shank is 6 mm. According to this proposed solution of the invention, a radius of 3.5 mm results for this case example. The radius is the same on all thread bases of the threaded section of the screw tip.

A further development of the invention can also be seen in the fact that the thread base of the threaded section of the screw tip is composed of two areas that follow one another in the direction of the screw tip, so that the concave groove is adjoined by an area with an inclined surface. This very special design of the thread base creates a homogeneous transition between the fillet and the adjoining inclined surface, which leads to an optimization of the material displacement of the wood-based material during the screwing process.

It is also a particular advantage if the length (L) of the threaded section of the screw tip is L=2×d, ie twice the nominal diameter of the wood screw. Continuing with the example given above where the nominal diameter is 6mm, in this case the screw tip length would be 12mm. This already shows that the tip of the screw is relatively long, which also results in a significant improvement in the screwing behavior.

In addition to the length of the screw tip, the design of the screw tip itself is also important. To this end, a further suggestion of the invention is that the screw tip has a tip angle α between α=15° and α=25°. A preferred tip angle here is 20°. So that's the screws tip of a wood screw according to the invention is designed like a needle or nail and thus allows piercing into the comparatively softer wood material before the screwing begins. In this way, the fixation of the wood screw in the subsurface has been optimized.

Wood screws according to the invention can have a continuous thread over the entire screw shank. However, the peculiarities of the wood-based material mean that it is advantageous if the wood screw has different threaded sections or also unthreaded sections, starting from the screw tip and running in the direction towards the screw head. According to one embodiment of the invention, it is proposed that the wood screw has a second thread section which follows the threaded section of the screw tip in the direction of the screw head and has at least one peeling rib, which is formed between the flanks of the thread. Such a peeling rib serves in particular to shred the wood-based material. This effectively counteracts unwanted splitting of the wood during screwing.

The peeling rib formed as a raised structure at the root of the thread can be designed in different ways. It is thus possible, for example, for the peeling rib to run helically around the screw shank of the wood screw. Thus, the peeling rib runs independently of the threads of the wood screw, for example in the opposite direction.

An alternative embodiment variant of the peeling rib is that it runs in a straight line along the screw shank, enclosing an acute angle β with the central axis of rotation of the wood screw. According to a further proposal of the invention, the angle β can be between β=10° and β=40°, but preferably 30°.

If a wood screw according to the invention is divided into several threaded sections, the object of a design measure is that the wood screw has a third threaded section which follows the second threaded section in the direction of the screw head and consists exclusively of a screw thread with thread flanks formed along the shank of the wood screw are.

Starting from the tip of the screw and viewed in the direction of the screw head, according to a further development of the invention it is further proposed that the wood screw has a fourth thread section following the third thread section in the direction of the screw head, the thread flanks of which, deviating from the thread flanks of the remaining thread turns of the thread sections, are designed as peeling cutters. Such a paring cutter consists of threads arranged helically around the core diameter of the wood screw, the diameter of which is slightly larger than the diameter of the screw shank. The milling cutter performs a scraping function and is particularly important when, for example, two boards are screwed together. The drill hole in the upper board is widened by the paring cutter, so that the screwing resistance of the wood screw is reduced. However, such a milling cutter is usually only used when wood screws with a partial thread are used. In the case of wood screws with a full thread, the milling cutter is regularly omitted.

According to a further proposal, the wood screw according to the invention is also characterized in that the wood screw has a thread-free section following the fourth threaded section in the direction of the screw head, which section extends to the screw head and has a circular-cylindrical diameter. This thread-free section preferably corresponds to the core diameter of the wood screw and also reduces the resistance when screwing the wood screw into the wood material.

The wood screws according to the invention can be equipped with a screw head which is designed as a countersunk head, a plate head, a cylinder head or a pan head. Other screw head shapes can of course also be used and are within the scope of the invention. If one considers, for example, a wood screw with a screw head designed as a countersunk head, it represents a particular advantage of the invention if the screw head of the wood screw has at least two milling ribs on its underside facing the screw tip, which are distributed symmetrically along the circumference of the screw head. The milling ribs have the task of making it easier for the screw head to penetrate the wood-based material if there is no pre-drilling in the sense of a countersink.

In a particularly preferred manner, the screw head has 6 to 8 milling ribs on its underside, which are distributed evenly along the circumference. In this way, an optimal milling of the recess for the countersunk head of the wood screw is achieved.

In a manner known per se, a wood screw according to the invention is also provided with a screw equipped benkopf, which has a tool engagement surface or a tool engagement surface on its top side of the screw head, which is suitable, for example, for inserting or attaching a screwdriver or a screwing tool in general.

According to one embodiment of this proposed solution, the tool engagement surface or tool application surface is a screw slot, a Phillips head, an external hexagon, an inner key surface or an outer key surface.

The invention is explained in more detail below with reference to the accompanying drawings. The exemplary embodiment shown does not represent any restriction to the variant shown, but only serves to explain a principle of the invention.

Identical or similar components are always denoted by the same reference numbers. In order to be able to illustrate the mode of operation according to the invention, the figures only show greatly simplified basic representations, in which the components which are not essential for the invention have been omitted. However, this does not mean that such components are not present in a solution according to the invention.

• 1: eine Holzschraube in der Seitenansicht,
• 2: einen vergrößerten Ausschnitt des Gewindeabschnittes der Schraubenspitze der Holzschraube aus 1 und
• 3: den Schnittverlauf III-III aus 1.

It shows:

• 1 : a wood screw in side view,
• 2 : an enlarged section of the threaded section of the screw tip of the wood screw 1 and
• 3 : the cutting course III-III 1 .

The exemplary in the 1 The wood screw 1 shown consists essentially of the screw shank 2, which has a screw head 3 on one side and a screw tip 4 on the side opposite the screw head 3. Viewed in the longitudinal direction of the screw shank 2 , this has different threaded sections 5 , 6 , 7 , 8 and a section 16 without a thread. The thread section 5 that is relevant according to the invention ends in the thread tip 4, which in the present case tapers to a point like a needle or nail, so that the wood screw 1 can first be pierced with the screw tip 4 into the wood-based material before it is screwed in and can thus be loosely fixed at the screw-in point before the actual screwing process begins. The inventive features of the threaded portion 5 with the screw tip 4 is described in more detail below in connection with the description of FIG 2 received.

The threaded section 5, starting from the screw tip 4 in the direction of the screw head 3, is followed by a threaded section 6, between whose thread flanks 9 peeling ribs 13 are formed, which in the example shown have a rectilinear course at an angle β to the central axis of rotation 14 of the wood screw 1 exhibit. In the example shown, the angle β is approximately 20°. However, such peeling ribs 13 can not only be used in sections, as in the example in 1 shown wood screw 1, but also run over the entire length of the screw shank 2. The peeling ribs 13 have the task of fraying the wooden material in order to prevent the wood from splitting when the wood screw 1 is screwed in.

If one follows the screw shank 2 further in the direction of the screw head 3 , the previously described threaded section 6 is followed by a further threaded section 7 which merely has a conventional screw thread of a wood screw 1 .

The thread section 7 is followed by a differently designed thread section 8, the thread flanks 15 of which form a paring cutter, with the thread flanks 15 having a larger diameter than the shank diameter of the screw shank 2. When screwing two boards together, the paring cutter is used to drill the hole in the upper board expanded, so that overall the screwing resistance of the wooden hood 1 is reduced in this way.

In the direction of the screw head 3, the threaded section 8 is finally followed by an unthreaded section 16.

On the underside 17 of the screw head 3 facing the unthreaded section 16, several milling ribs 18 are distributed along the circumference, which allow the formation of a sink in the wood material when screwing in a countersunk screw, provided that such a sink was not previously introduced into the wood surface. In a manner known per se, the screw head 3 has a tool engagement surface 20 on its upper side 19, which serves to couple the screw head 3 to a suitable screwing tool. The tool engagement surface 20 can be a cross slot, for example.

From the 2 an enlarged section of the threaded section 5 containing the screw tip 4 is shown. This becomes verbes serter way than this in connection with the description of the 1 was possible, clearly where the inventive features of the threaded portion 5 of the screw tip 4 can be seen. A thread base 10 is formed between the individual thread flanks 9 and has a concave, ie rounded, groove 11 . The fillets 11 have a ratio of the nominal diameter d of the thread to the radius, which is 1.714 in the present case. Another special feature of the thread base 10 can also be seen in the fact that, viewed in the direction of the screw tip 4, the concave groove 11 is followed by an inclined surface 12, the width of which, viewed in the direction of the screw tip 4, increases with each thread turn. If the dimensions of the thread root 10 between two adjacent thread flanks 9 remain the same, the length of the concave groove 11 is consequently reduced 2 also the thread section 6 adjoining the thread section 5 with the peeling ribs 13 formed thereon.

The 3 finally shows the cutting line III-III 1 through the screw shank 2 of the wood screw 1. The section runs through the unthreaded section 16, which in this embodiment corresponds to the shank diameter of the wood screw and allows a view of the underside 17 of the screw head 3. Several milling ribs 18 are formed along the peripheral surface are distributed symmetrically over the circumference of the underside 17 of the screw head 3.

reference list

1

wood screw

2

screw shank

3

screw head

4

screw tip

5

threaded section (tip)

6

threaded section

7

threaded section

8th

threaded section

9

thread flank

10

thread root

11

concave throat

12

bevel

13

peeling rib

14

central axis of rotation

15

thread flank

16

unthreaded section

17

bottom

18

milling rib

19

screw head top

20

tool engagement surface

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• EP 2224142 B1 [0003]
• DE 3337534 A1 [0004]
• DE 9307816 U1 [0005]
• EP 3040563 B1 [0006]
• EP 0012441 A1 [0007]
• DE 69915254 T2 [0008]
• WO 2020060902 A1 [0009]
• US2008008953A1[0010]
• DE 102017208282 A1 [0011]

Claims (17)

Wood screw (1), comprising a screw shank (2) which has a screw head (3) and a screw tip (4) on the side opposite the screw head (3), wherein on the screw shank (2) at least one screw tip (4) running threaded section (5, 6, 7, 8), characterized in that between the thread flanks (9) of the threaded section (5) of the screw tip (4) a thread root (10) is formed, which extends in the longitudinal direction of the screw shank (2nd ) has a concave groove (11). wood screw claim 1 , characterized in that the concave groove (11) has a radius (R) for which, based on the nominal diameter (d) of the thread of the wood screw (1), applies: d / R = 1.2 to 2.0. Wood screw according to one of the preceding claims, characterized in that the thread base (10) of the threaded section (5) of the screw tip (4) is composed of two areas (11 and 12) following one another in the direction of the screw tip (4), so that the concave groove (11) is followed by an area with an inclined surface (12). Wood screw according to one of the preceding claims, characterized in that the length (L) of the threaded section (5) of the screw tip (4) is L = 2 x d. Wood screw according to one of the preceding claims, characterized in that the screw tip (4) has a tip angle α between α = 15° and α = 25°. Wood screw according to one of the above claims, characterized in that the wood screw (1) has a second threaded section (6) with at least one peeling rib (13) following the threaded section (5) of the screw tip (4) in the direction of the screw head (3). , which is formed between the thread flanks (9). wood screw claim 6 , characterized in that the peeling rib (13) runs helically circumferentially along the screw shank (2) of the wood screw (1). wood screw claim 6 , characterized in that the peeling rib (13) runs in a straight line along the screw shank (2), enclosing an acute angle β with the central axis of rotation (14) of the wood screw (1). wood screw claim 8 , characterized in that the angle β is between β=10° and β=40°. Wood screw according to one of the preceding claims, characterized in that the wood screw (1) has a third threaded section (7) following the second threaded section (6) in the direction of the screw head (3), which consists exclusively of a screw thread with thread flanks (9) consists, which are formed along the screw shank (2) of the wood screw (1). Wood screw according to one of the above claims, characterized in that the wood screw (1) has a fourth thread section (8) following the third thread section (7) in the direction of the screw head (3), the thread flanks (15) of which deviate from the thread flanks (9) of the remaining threads of the threaded sections (5 to 7) are designed as peeling cutters. Wood screw according to one of the preceding claims, characterized in that the wood screw (1) has a thread-free section (16) which follows the fourth threaded section (8) in the direction of the screw head (3) and extends up to the screw head (3). and has a circular-cylindrical diameter. Wood screw according to one of the preceding claims, characterized in that the screw head (3) of the wood screw (1) has on its underside (17) facing the screw tip (4) at least two milling ribs (18) which are symmetrical along the circumference of the screw head ( 3) are distributed. wood screw Claim 13 , characterized in that the screw head (3) has 6 to 8 milling ribs (18) on its underside (17). Wood screw according to one of the preceding claims, characterized in that the screw head (3) of the wood screw (1) has a tool engagement surface (20) or a tool engagement surface on its upper side (19). wood screw claim 15 , characterized in that the tool engagement surface (20) or the tool engagement surface is a screw slot, a Phillips head, an external hexagon, an inner key surface or an outer key surface. Wood screw according to one of the preceding claims, characterized in that the screw head (3) is designed as a countersunk head, a plate head, a cylinder head or a pan head.

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