Screw

The subject of the invention is a screw, in particular a self-drilling screw.

It is known that, to facilitate screwing into wood or wood-like material, milling ribs are placed on the drilling tips of the screws, which usually run in the longitudinal direction, i.e. transversely to the movement of the screw tip relative to the wood. These milling ribs are also provided to reduce the risk of cracks due to splitting or external splintering.

Document US 2,263,137 discloses a bolt having the features of the spare part of claim 1.

In a known bolt of this kind (DE 19525732), with a cone-shaped tip, the milling ribs lie in a cone forming, in other words, they run in the longitudinal median plane containing the longitudinal axis of the bolt.

A screw (EP 939235 A) is also known in which a plurality of milling ribs run obliquely, namely at an angle of inclination relative to the longitudinal axis, lying in the range of about 15 °.

The object of the invention is to create a screw, especially a self-drilling screw, with improved screwing properties, especially in terms of splitting wood.

In order to solve this task, the invention proposes a screw with the features listed in claim 1. Further developments of the invention are the subject of the dependent claims.

In the production of the hole into which the screw is to be screwed then, the counter-thread, which extends only over a certain part of the thread, creates a particularly advantageous opportunity to prevent splitting, so that the screw can also be used in the area of ​​the edge of the wood, without the risk of milling tearing there wood and a screw cannot be screwed in exactly then.

It has proved particularly sensible to shape the scraper thread so that it extends through two to three turns, so that also in this way, with this scraper thread, a continuous scraper edge is formed, possibly interrupted by a screw thread.

In a further development of the invention, the height of the scraper thread can be chosen such that it lies between 0 mm and the maximum height of the screw thread.

It follows from claim 1 that the scraper thread does not start exactly at the front sharp end of the screw tip. This ensures that the wood first enters, to generate feed, a screw thread extending to the front end. According to the invention, it can be provided that the height of the thread s of crackers remains constant from its front area, assigned to the tip of the screw, to its end. This applies especially if the height of the scraper thread is smaller than the height of the screw thread.

However, it is also possible and it is within the scope of the invention that the height of the scraper thread from its beginning assigned to the tip of the screw to its opposite end decreases continuously.

According to the invention, it can be provided in a further development that the pitch of the scraper thread is less than or equal to the pitch of the helical thread.

Scraper thread pitch equal to the pitch of the screw thread has proved to be particularly advantageous.

The screw thread may be a chipboard thread or also a wood thread. It can be single-turn or multi-turn.

The tip of the screw may be a drilling tip, i.e. the conical shape of the tip of the screw with the screw thread running up to the top. But the invention can also be applied to a screw that has a cutting tip at its front end, in particular an extruded cutting tip, with cutting edges.

While at the drilling tip, the scraper thread already starts inside the conical area, for example in the middle of the length of the conical area, in the case of a cutting tip, the scraper thread only begins after the cutting tip.

The screw proposed by the invention is not only suitable for wood or wood-like materials, but is also suitable for use as a sheet metal screw.

Further features, details and advantages of the invention result from the claims and the abbreviation, the sound of which is formed by reference to the content of the following description, a preferred embodiment of the invention and based on the drawing. They show:

1 is a side view of a first embodiment of a screw according to the invention;

2 shows a side view of a second embodiment of the invention.

The screw shown in figures 1 and 2 comprises a cylindrical shank 1 of a screw which in its lower end in figure 1 goes to the tip of the 2 screws. In the embodiment of figure 1, the tip of the screw 2 has a conical shape with a sharp peak 3. The angle of the cone is about 30 °. At the opposite end a pipe with 4 screws is formed, in the example shown it is a recessed pipe. From the free, for example flat end 5 of the countersunk head 4, a cavity for driving the screw leads into its interior, for screwing the screw with a suitable tool.

A screw thread 6 is formed on the shank 1 of the screw, made for example by rolling. The example shown is a single-turn thread. In the embodiment according to figure 1, this thread 6 extends to the sharp top 3 of the tip 2 of the screw.

At the same time, in the front area, there is a countercurrent thread 7, which starts approximately half the length of the tip of the tip of the 2 bolt and which extends approximately by three turns. This thread 7 forms a thread edge that is shaped and acts as a scraping edge. From figure 1, but also from figure 2 it follows that this counter-rotating scraper thread has the same pitch as the screw thread 6. The height of this thread, i.e. the distance of its scraping edge from the surface of the stem 1 of the screw, is approximately half the height of the screw thread 6.

In the embodiment according to figure 2, the tip of the screw 2 is shaped as the cutting tip 8, which is formed by the extrusion process. It comprises two front cutting edges 9 which perform the proper drilling process and two side cutting edges 10 which run parallel to the longitudinal direction of the axis. Also here, between the screw thread 6, there is a scraper thread 7, which again has the same pitch as the screw thread 6, but has a smaller thread height.

1. SWG Schraubenwerk Gaisbach GmbH

2. Adolf Wiirth GmbH & Co. KG

Proxy:

42Ρ26276EN00 ΕΡ 1 925 828 Bl