HK1161625A1

HK1161625A1 - Screw

Info

Publication number: HK1161625A1
Application number: HK12101762.0A
Authority: HK
Inventors: Werner Braun; Fabian Mohr
Original assignee: Fischerwerke Gmbh & Co. Kg
Priority date: 2008-09-24
Filing date: 2009-09-01
Publication date: 2012-07-27
Also published as: CN102165202A; PL2326848T3; DE102008048703A1; EP2326848A1; CN102165202B; EP2326848B1; DK2326848T3; WO2010034390A1; MY154450A; TWI467097B; TW201026968A; ES2421706T3

Abstract

The invention relates to a screw (1) comprising a shaft (2), a tip (3), a head (4) having rotary dog means (5), a primary thread (6) and a secondary thread (7), wherein the primary thread (6) has a lesser thread pitch than the secondary thread (7), wherein the primary thread (6) extends at least over a first partial length (22) of the shaft (2), and wherein the secondary thread (7) extends at least over a second partial length (23) of the shaft (2). In order to improve the user friendliness and the installation characteristics of the screw (1), the invention proposes for the primary thread (6) and the secondary thread (7) to extend up to a front end (10) of the tip (3) of the screw (1) and for the primary thread (6) to have thread flanks (11) over a substantial part of the length thereof, particularly in the region of the shaft (2), which are higher than the thread flanks (12) of the secondary thread (7).

Description

screw nail

Technical Field

The invention relates to a screw having a shank, a tip, a head with rotational synchronization means, and a main thread and a secondary thread.

Background

Such a screw relates, for example, to a wood screw or chipboard screw, which is known, for example, from document US 4874278. The screw known from fig. 1 of the document has a shank, a tip, a head with rotational synchronization means, and a main thread and a secondary thread, the pitch of the main thread being smaller than the pitch of the secondary thread. Further, the tip portion is denoted by "front end" and the tip portion is denoted by "rear end". The primary thread extends over a first length portion of the shank and the secondary thread extends over a second length portion of the shank. In this screw the secondary thread is provided on the shank portion near the conical tip. A second portion of the primary thread is provided on the tapered tip whereby the secondary thread interrupts the primary thread. The secondary thread is used to expel drilling mud. This prevents local deposits of drilling dust, which impede the screwing-in of the screw, cause friction, increase the screwing-in torque of the screw and cause compressive stresses, which can lead to cracks in the workpiece. The secondary thread does not consist of a circumferential thread but rather has a plurality of ribbed thread flanks.

Document EP 0939235 shows another such screw. As the secondary thread, a plurality of rib-like cutting edges are present, which extend over a part of the tip up to the rib section. The function of the cutting edge is to cut the wood fibers, reduce the screwing-in resistance of the screw and thus the screwing-in torque and prevent wood cracks. The main thread in the unbanded end section of the screw tip ensures a good and reliable introduction of the screw, unhindered by the cutting rib.

The known screws are high-performance wood or chipboard screws which, owing to the special secondary thread structure and their function of preventing cracking of the workpiece, can also be used in the region of the workpiece close to the edge. However, the known screws are a compromise solution, on the one hand they are to be quickly and fully driven into the workpiece and, on the other hand, to reduce the screwing-in torque of the screw and the risk of material cracks. This results in the screw not satisfying the first aspect completely nor the second aspect completely.

Disclosure of Invention

The object of the invention is therefore to further improve the known screws with regard to their ease of use and their assembly properties without increasing the risk of material cracks or the screwing-in torque of the screws.

To this end, the invention proposes a screw having a shank, a tip, a head with a rotational synchronization means, and a main thread and a secondary thread, wherein the main thread has a smaller pitch than the secondary thread, the main thread extends at least over a first length of the shank, wherein the secondary thread extends at least over a second length of the shank, characterized in that the main thread and the secondary thread extend up to the front end of the screw tip and start with a common starting thread at the front end, and in that the main thread has flanks over a major part of its length, in particular in the region of the shank, which are higher than the flanks of the secondary thread.

The screw according to the invention can be used in general in preformed materials such as wood, wood fibre press plates, similar materials or plastics, which have a shank, a tip, a head with rotational synchronization means and a main thread and a secondary thread, the main thread having a smaller pitch than the secondary thread. The primary thread extends over at least a first length of the shank and the secondary thread extends over at least a second length of the shank. The screw according to the invention is characterized in that the main thread and the secondary thread extend as far as the front end of the screw tip, and the main thread has thread flanks over a major part of its length, in particular in the region of the shank, which are substantially higher than the thread flanks of the secondary thread. The main thread is formed by a circumferential helical thread. The "front end" of the screw tip refers to the front end of the screw which points in the screwing direction toward the workpiece, i.e. the side opposite the screw head. "height of the flanks" means the height of the flanks of the main and secondary threads in the same cross-section of the screw, with the longitudinal axis of the screw perpendicular to the respective cross-sectional surface. The screw head can be formed, for example, by a countersunk, hexagonal or oblate head, for example with a straight slit, a cross or a quincunx head, which forms the rotational synchronization means. If the screw according to the invention is placed on a workpiece for screwing, the arrangement according to the invention of the main thread and the secondary thread (both of which reach as far as the front end of the screw tip) results in the main thread of the screw already engaging with a minimum rotational movement and causing the screw to be introduced into the workpiece. The pressing force is very slight, and the tip of the screw must be pressed against the workpiece with this pressing force. This results from the fact that both the primary thread and the secondary thread extend as far as the front end of the screw tip and it is not necessary to press the unthreaded tip into the material, thereby bringing the thread flanks into contact with the workpiece. Since the main threads have thread flanks which are higher than the thread flanks of the secondary threads, the secondary threads do not interfere with the screwing of the screw into the workpiece. In contrast, the secondary thread structure, which is formed by a circumferential thread with a greater pitch than the primary thread, results in the primary thread being pressed in the direction of the workpiece by the secondary thread, which facilitates the quick screwing of the screw into the wood. Furthermore, the drilling dust produced by the secondary thread is removed, which significantly reduces the tendency of the wood to crack. Compared to the screws known from the prior art (which have a relatively high secondary thread based on the main thread, which disturbs their function due to its size despite the cutting of wood fibers), the screw according to the invention is significantly improved with regard to its application-friendliness and its assembly properties, in particular when being placed on a workpiece and when screwing in the screw during the first rotation.

The primary and secondary threads preferably have the same orientation, i.e. for example two right-hand threads.

In order to improve the assembly properties of the screw even further after it has been placed directly on the workpiece, in a preferred embodiment of the screw according to the invention the main thread and the secondary thread start with a common starting thread on the front end of the screw tip. The screw therefore has a defined setting point at its front end, at which two threads start. The two threads thus cut into the material jointly, uniformly and for the same time. Screw slippage due to the offset arrangement of the two thread leads in time is therefore precluded. The secondary thread supports the screwing-in of the main thread, in which drilling dust is carried out and, due to the greater pitch of the secondary thread, presses the main thread into the material.

According to an advantageous embodiment of the screw according to the invention, the pitch of the secondary thread is 2 to 4 times, in particular 3 times, the pitch of the primary thread. In a further advantageous embodiment of the screw according to the invention, the height of the thread flank of the main thread is substantially 1.5 to 4.0 times, in particular 1.8 to 3.5 times, the height of the secondary thread. This embodiment has proven to be particularly application-friendly and assembly-friendly. The values are approximate values within +/-20% of the error range due to the machining process.

In a further advantageous embodiment of the screw according to the invention, the secondary thread is interrupted in a region of the shank. The secondary thread thus has, for example, a first partial thread in the region of the screw tip and a shank portion at the front end in the screwing-in direction, and a second partial thread at the rear end of the shank. The interruption of the secondary thread prevents the drill hole produced by the screw from drilling into the wood less strongly, which may contribute to the fastening force of the screw in the wood. The drilling dust is transported away from the screw tip by the first part of the secondary thread, whereby the screw can be easily pushed into the material and the wood is prevented from cracking. The secondary thread of the second part has the effect that drilling dust transported by the main thread is not deposited behind the main thread and locally pressed, which may increase the friction between the thread flanks and the material and thus the screwing-in torque and may cause material cracks.

A further preferred embodiment of the screw according to the invention provides that the first section of the secondary thread has a distance of at least 2, in particular substantially 4, main thread leads from the second section of the secondary thread. The lead describes the axial travel, into or out of which the screw thread is screwed when rotating. An embodiment of the screw according to the invention is particularly advantageous in which the first section of the secondary thread extends over 2 to 6, in particular over 4, of the primary thread leads from the tip. This value may vary by +/-20% due to production conditions. This embodiment has a secondary thread leading on the 4 main thread leads from the tip and a secondary thread interruption connected thereto, which likewise extends over the 4 main thread leads, which brings about outstanding effects in terms of assembly friendliness and holding value.

Another preferred embodiment of the screw according to the invention has cut grooves on its main thread which remove material from the lead, possibly other milling cutters intersecting the lead and thereby reducing the resistance to the thread engaging in the screwing-in direction. The cutting flutes may be disposed back and forth parallel to the longitudinal axis of the screw. Alternatively, the mutually adjoining cutting grooves can be arranged offset in the circumferential direction. The cutting grooves reduce the resistance to screwing into the wood and enable easy screwing of the screws.

In order to further reduce the screwing-in resistance of the screw, a shank milling rib is provided on the shank of a further preferred embodiment of the screw according to the invention. These beads, which are located behind the main thread in the screwing-in direction, expand the bore hole produced by the screw. Thereby reducing friction between the wood and the unthreaded portion of the screw between the shank bead and the screw head. Furthermore, the stresses in the workpiece, which may occur as a result of the enlarged screw core in the shank, are reduced. A further embodiment of the screw according to the invention is advantageously at least partially coated with a slip wax. The wax slide further reduces the resistance to screwing into the material, with the aim of making it possible to screw in the screw quickly and in a time-saving manner.

In order to be able to drive the screw into the material in such a way that the screw tip does not protrude from the workpiece surface, a further preferred embodiment of the screw according to the invention provides the bottom surface of the screw tip with a tip milling. The material is removed by the end milling ribs when screwing in the screw in order to create a space in which the screw end can be sunk. This enables a flush closure of the screw head with the workpiece surface. Furthermore, the risk of workpiece cracking during the sinking of the screw head is reduced.

The screw shank according to the invention advantageously has a cross section at the transition to the screw head which is enlarged compared to the thickened cross section. The torsional resistance torque is increased at this point by the locally enlarged cross section and the stresses occurring at the transition to the end head are reduced. This better prevents the screw head from twisting, which is particularly important for hard materials with high screwing resistance or in screwing from metal to wood, for example in wood connections or profiles. In the case of a countersunk-head screw, the screw head can be formed, for example, as a double cone, i.e., the screw head, which expands conically in the rearward direction, has an enlargement at the transition to the shank, which likewise expands conically in the rearward direction.

Drawings

The invention is explained in detail below with the aid of examples. In the drawings:

figure 1 shows a side view of a screw according to the invention,

fig. 2 shows an enlarged view of the front end of the screw according to the invention.

Detailed Description

Fig. 1 and 2 show a screw 1 according to the invention, having a shank 2, a conical tip 3 and a head 4 with a rotation synchronization means 5, which is not shown in detail. The screw 1 also has a main thread 6 and a secondary thread 7. The thread-free portion 18 of the shank 2 with the shank bead 19 is located between the head 4 and a first length 22 of the shank 2, on which the main thread 6 is arranged. The shape and function of the shank milling flutes 19 are also described. The primary thread 6 has a smaller thread lead than the secondary thread 7. The lead q of the secondary thread 7 in this screw 1 is 3 times the lead p of the primary thread 6.

The main thread 6 extends over a first length portion 22 of the shank 2. The secondary thread 7 extends over a second length portion 23 of the shank 2. Two length sections 22 and 23 extend from the tip 3 of the screw 1 along the shank 2, wherein this first length section 22 is larger than the second length section 23. The main thread 6 is essentially provided as a thread around the tip 3 and the shank 2 of the screw 1, which is not interrupted by the secondary thread 7. While the secondary thread 7 is interrupted by the primary thread 6. The secondary thread 7 is guided in this way, however, the screw 1 is described by a continuous screw line despite the interruption by the primary thread 6. The secondary thread 7 does not interrupt the primary thread 6, but starts on both sides of the primary thread 6 at the intersection of the two threads 6, 7 by two respective sections 9. There is thus the impression that the secondary thread 7 tunnels across the primary thread 6.

The feature of the screw 1 according to the invention is that the main thread 6 and the secondary thread 7 extend as far as the front end 10 of the tip 3 of the screw 1, and that the main thread 6 has thread flanks 11 over a substantial part of the length 22, in particular in the region of the shank 2, which are substantially higher than the height of the secondary thread 7 in the same cross section. For example, the main thread 6 has a height h in the cross section A-A of the thread flank 11₁Is greater than the height h of the flanks 12 of the secondary thread 7₂. Height h of main thread 6 in cross section A-A₁About twice the height h of the flanks 12 of the secondary thread 7₂。

Since the two threads 6, 7 extend as far as the front end 10 of the tip 3 of the screw 1, the two threads 6, 7 already bite into the workpiece, not shown, directly after the setting of the screw 1 and during a first rotation of the screw 1. This ensures a good and reliable introduction of the screw 1 into the workpiece, the minor thread 7 being formed by the slight height h of its thread flank 12₂It does not interfere but facilitates the run-in of the flanks 11 of the main thread 6. The secondary thread 7 displaces drilling dust, not shown, and supports the feed of the primary thread 6 due to its larger thread lead. By the greater height h of the flanks 11 of the main thread 6₁This main thread can be formed into a well-loaded thread groove and thus a stable feed is ensured. It is therefore evident that by setting the screw 1 it has been shown that the main thread 6 cuts, carries and drives, the secondary thread 7 mills and expels drilling dust. This significantly improves the assembly properties of the screw 1 according to the invention compared to screws known from the prior art.

The arrangement of the screw 1 according to the invention on the workpiece is also improved in that both the main thread 6 and the auxiliary thread 7 start with a common thread start 24 on the front end 10 of the tip 3 of the screw 1. This prevents the screw 1 from slipping from a workpiece, not shown, which may occur if, for example, the primary thread 8 is first brought into contact with the workpiece and then the secondary thread 7 is brought into contact with the workpiece.

The secondary thread 7 is interrupted in the region of the shank 2. It extends in a first section 13 from the front end 10 of the tip 3 of the screw 1 over the second length 23 of the shank 2 and over the four thread leads of the main thread 6. On which is engaged an intermediate section 14, which is free of secondary threads 7. This intermediate section 14 extends over at least two, in the illustrated screw, four thread leads of the main thread. The intermediate section 14 is connected to a second section 15, on which the secondary thread 7 is again arranged. The length L of the second section 15 of the secondary thread₃In this case three pitches of the main thread 6.

In order to reduce the screwing-in resistance of the screw 1, the screw 1 according to the invention has a cut-out groove 16. The cutting groove 16 is formed by a triangular, locally provided recess on the thread flank 11 of the main thread 6. The cutting grooves 16 are arranged in the middle section 14 without the secondary thread 7 on three middle thread leads 17 of this middle section, wherein each thread lead 17 has three cutting grooves 16 which are distributed evenly over the circumference, i.e. offset by 120 °. The cutting grooves 16 of two mutually adjoining thread leads 17 are also offset in the circumferential direction by 60 ° with respect to the longitudinal axis of the screw 1. The function of the cutting groove 16 is, for example, to remove material from the workpiece when the screw 1 is screwed in, thereby expanding the channel formed by the main thread 6 and reducing the screwing resistance of the screw.

A shank bead 19 arranged between the head 4 of the screw 1 and the main thread 6 fulfills a similar function. Six shank ribs 19 are arranged distributed over the circumference and are of substantially helical design. Other configurations, such as straight or wavy, may be selected. The shank ribs 19 each extend at 1/3 of the thread lead of the shank ribs 19, i.e. at 120 ° in the circumferential direction, wherein the distance between the individual shank ribs 19 is 1/6 ° of the circumference of the screw 1 or 60 ° in angular coordinate. The shank milling rib 19 has the task of discharging and diffusing drilling dust, not shown, generated by the screw 1, so that the shank 2 part 18 without thread can be screwed into the borehole without the screwing resistance being significantly increased by the friction between the workpiece and the shank 2 part 18 without thread. The screw 1 may also be coated with a slip wax, for example, at a slip modulus 615 of 1: 3.

A thickened cross section 20, which enlarges conically towards the head 4 of the screw 1, is connected to the shank 2 at the shank thread-free portion 18. The opening angle α 1 of the cone of the thickened cross section 20 is 45 ° half the opening angle α 2 of the likewise conically formed head 4, which is 90 °. The effect of the thickened cross section 20 is to increase the torsional resistance torque at this point and thus to prevent the head 4 from breaking at the transition between the shank 2 and the head 4. Furthermore, the cross section of the screw 1 is enlarged in this region, so that the not shown receiving body can be designed deeper as a rotational synchronization means 5, which improves the receiving of the tool. In the illustrated screw 1 with a countersunk head 4, the rotation synchronization means 5 is formed, for example, by a quincunx head or a cross-shaped receptacle. Of course, other rotational synchronization measures 5, such as an outer hexagon, are also conceivable in principle. A linearly extending end milling rib 21 is also provided on the bottom surface of the end 4. The end bead 21 expands in the workpiece through the hole produced by the screw 1 in such a way that the end 4 of the screw 1 can also sink into the hard material of the workpiece.

Each of the individual features described above improves the use-friendliness and assembly properties of the screw according to the invention in itself. The combination of the features described above results in the screw 1 shown in the exemplary embodiment, particularly application-friendly, having particularly user-friendly assembly properties.

In the following, typical embodiments of the screw according to the invention are given in the table. This screw corresponds substantially to the screw 1 shown in fig. 1 and 2:

Claims

1. A screw (1) having a shank (2), a tip (3), a head (4) with a rotational synchronization means (5) and a main thread (6) and a secondary thread (7),

-wherein the primary thread (6) has a smaller pitch than the secondary thread (7),

-wherein the main thread (6) extends at least over a first length portion (22) of the shank (2),

-wherein the secondary thread (7) extends at least over a second length portion (23) of the shank (2), characterized in that,

-said main thread (6) and secondary thread (7) extend up to the front end (10) of the tip (3) of the screw (1) and start with a common starting thread (24) on the front end (10), and

-said main thread (6) has, over a major part of its length, flanks (11) which are higher than flanks (12) of the secondary thread (7).

2. Screw according to claim 1, characterized in that said primary thread (6) and secondary thread (7) have the same orientation.

3. Screw according to claim 1 or 2, wherein the pitch of the secondary thread (7) is 2 to 4 times the pitch of the primary thread (6).

4. Screw according to claim 1 or 2, wherein the height of the thread flank (11) of the main thread (6) is substantially 1.5 to 4.0 times the height of the secondary thread (7).

5. Screw according to claim 1 or 2, characterized in that the secondary thread (7) is interrupted at one point of the shank (2).

6. The screw according to claim 5, characterized in that the first section (13) of the secondary thread (7) has a distance of at least 2 leads of the primary thread (6) from the second section (15) of the secondary thread (7).

7. The screw according to claim 1 or 2, characterized in that the first section (13) of the secondary thread (7) extends from the tip over 2 to 6 leads of the primary thread (6).

8. Screw according to claim 1 or 2, characterized in that the main thread (6) has a cutting groove (16).

9. Screw according to claim 1 or 2, wherein a shank milling rib (19) is provided on the shank (2).

10. Screw according to claim 1 or 2, characterized in that the screw (1) is at least partially coated with a slip wax.

11. Screw according to claim 1 or 2, wherein a head milling rib (21) is provided on the screw head (4).

12. Screw according to claim 1 or 2, wherein the shank (2) has an enlarged cross section in the transition to the screw head (4) compared to the thickened cross section (20).