Countersunk screw

The present invention relates to a countersunk head screw with a threaded shank and a countersunk head, in the direction of the threaded shank with a one countersinking angle has tapered conical surface, said conical surface having a plurality on the Circumferentially arranged distributed together a conical enveloping surface with a having cone angle defining ribbed protrusions, wherein the angle of depression of is cone surface is smaller than the cone angle of the ribbed protrusions.

Countersunk screws are known in numerous designs. The countersunk head can be used as Flat or Raised be formed. Such screws are on the one hand for fixing of fittings or like components in particular made of metal used, with the respective component for each screw a countersunk mounting hole , whose angle of depression is generally in accordance with standards or approximately 90 °. On the other hand, such countersunk screws are also available in large numbers for so-called wood-wood connections used by screwed directly without pre-drilling will. Here, the flat head is automatically in the respective material Push and sink. In the latter application, but occurs because of Countersinking angle of 90 ° in wood-wood joints splicing on the wood. This is avoided by means of screws with a correspondingly smaller (steeper) angle of depression; However, these screws are not for mounting of components with 90 ° -Senklöchem suitable because they are not having a sufficiently large area in the Senkloch come to plant what has disadvantages for the mounting of the component.

Such countersunk the type just described, the generic is in EP 0781382 B1. The trained on the relatively steep angle of depression Conical surface provided, very narrow ribs have countersinking , So that the screw is to be able by means of the ribs in a workpiece a cutting free-cutting for the countersunk head. This screw therefore not suitable for fixing of fittings or the like with 90 ° -Senklöchem because while the cause ribs with their countersinking surface damage and would press with their very narrow surfaces.

The present invention is based on the object, a countersunk screw of to create the type mentioned which - virtually as a "universal screw" - for both Applications described is suitable with good performance characteristics.

This is achieved by the features of claim 1. According to the invention. More advantageous design features of the invention are in the dependent claims contain.

Accordingly, the conical surface distributed over the circumference of at least three arranged, that is, spaced in the peripheral direction, rib-like Ribbed protrusions with outer together a conical enveloping surface with a defining cone angle and inventively dimensonierten relatively large Plant surfaces. This means that according to the invention the area ratio of Sum of the bearing surfaces of all the ribbed projections to the sum of each intermediate spaces of the conical surface is designed such that on the one hand the ribbed protrusions not a direct sinking of the countersunk head in wood or like hinder soft material, and on the other hand when attaching Components with countersunk holes between the rib attachments and each Senkloch a certain material-specific or function of the Material combination screw component (especially metal-metal) thus conceived Surface pressure is achieved that damage to the surface of the area Countersunk opening of the component can be avoided. In this case, when tightening the Screw a high holding force without risk of damage on the contact surfaces in the component itself can be initiated. Simultaneously, the rib-shaped projections are such designed to in the former application with direct, countersinking Screwing in a relatively soft material, in particular wood or similar soft material, a cutting action (scraping) have. This contributes to a good sinking of the head with minimal risk of splicing and low Insertion torque at. Because of the inventive design of the contact surfaces the ribbed protrusions does not occur this milling effect at the fitting attachment or insignificant on.

The countersinking angle of the conical surface is smaller than the cone angle of the envelope surface of the Ribbed protrusions. In a preferred embodiment the angle of depression is relatively small or steeply formed; it lies approximately in the range of 50 ° to 60 °, and in particular about 53 ° to 55 °. This countersink angle is particularly advantageous for a direct Screwing into wood with reduced risk of splicing the sinking. In contrast, is the cone angle of the ribbed protrusions about 90 °, resulting in the beneficial Attachment of fittings and the like components with countersunk Mounting holes having a countersinking angle of also approximately 90 °.

Based on illustrated in the drawing, preferred embodiments The invention will be explained in detail. They show:<dl tsize="6"><dt>Fig. 1</dt><dd>a partial side view of a countersunk screw according to the invention Area of ​​the countersunk head and a portion of the adjoining Threaded shank,</dd><dt>FIG. 2</dt><dd>a sectional view taken in the direction of arrow II - II of Figure 1.</dd><dt>Fig. 3</dt><dd>a partial section through the region of one of the invention Rib-shaped projections in the plane III - III of FIG 2 and.</dd><dt>Fig. 4</dt><dd>a representation analogous to FIG. 2 in an embodiment variant.</dd></dl>

A countersunk screw according to the invention 1 comprises a threaded shaft 2 with a Countersunk 4. At the other end is the threaded shaft 2 in a non-illustrated Screw tip over. The countersunk head 4 has a towards the threaded shank 2 with a specific countersink angle α tapered conical surface 6 on.

In the illustrated embodiment, is in the countersunk head 4 a flat countersunk, the opposite to its threaded shank 2 having a flat surface. 8 Alternatively, the countersunk head 4 can also be as so-called Linsensenkopf be designed with a convexly curved surface. In both cases, the countersunk head 4 preferably one indicated by dashed lines in Fig. 1 Force application 10 comprise, in particular in the form of a cross slot or Innenstemangriffs, preferably with key guide.

The threaded shaft 2 consists of a cylindrical core at least in sections, 12 and a helically extending as an elevation over the core 12, one- or multiple thread 14. The thread 14 defines with its outer Thread edge a thread nominal diameter D. The pitch is in FIG. 1 drawn with S.

According to the invention on the conical surface 6 at least three ribbed protrusions 16 on distributed circumferentially and each spaced apart. These Ribbed protrusions 16 have outer contact surfaces 18, which together form a conical Enveloping surface with a cone angle β define (Fig. 1). The contact surface 18 of each Cone lug 16 thus forms a part of a conical surface with the cone angle β. Here, the invention provides that the angle of depression α of the conical surface 6 smaller than the cone angle β of the envelope surface of the ribbed protrusions 16 is. For a universal or optional application of countersunk screw 1 in the above Applications described, it is advantageous if the angle of depression α relatively steep and is approximately in the range of 50 ° to 60 °. For direct screwing into wood with Sinking of the countersunk head 4 with no or at least reduced risk of splicing is a Value of the countersinking angle α of 53 ° to 55 ° is particularly advantageous. The cone angle β is 90 ° and corresponds to the usual or standardized countersink angle of countersunk fixing holes of fittings or like components.

This should on the one hand the total (sum) of all the bearing surfaces 18 of the Ribbed protrusions 16 not be too large so that the sinking in the soft material Ribbed protrusions 16 can miteinsenken well. Here, according to the invention the Ribbed protrusions 16 designed so that they participate in this application of the screw direct, countersinking screwing especially in wood or similar Soft fabrics have a milling effect (scraping) have. This significantly reduces the Of splicing. On the other hand, the rib-shaped projections 16 with respect to the Surface area of ​​the bearing surfaces 18 in response to a material-specific Surface pressure designed so large that from when applying for fixing Fittings or the like by screwing into a sinkhole between Rib attachments 16 and the respective sinkhole such a sized Surface pressure occurs that damages in the area of ​​sinkhole be avoided. For this, the sum of the contact surfaces should be 18 all the ribbed protrusions 16 in the region of at least 40% to a maximum of about 60% of the whole Peripheral related conical envelope surface. The minimum size of Bearing surfaces 18 of the ribbed protrusions 16 of about 40% of the total area in FIG. 2 shown. For this purpose, the circumferential angular extent of the ribbed protrusions 16 with W1 in while the angular extent of the intervening spaces is denoted by W2. In the example shown, the angles are about 24 ° and W1 the angle W2 approximately 36 °. Thus, W1 is about 40% of the overall angle of 60 °. Preferably, the total size of all contact surfaces 18 should, however, about 50% of be whole envelope. This means that the sum of the contact surface 18 all the ribbed protrusions 16 approximately equal to the sum of the approaches between the ribs 16 surfaces lying is.

The screw 1 is made, for most applications, including for the attachment of Fittings of metal (steel, aluminum or other non-ferrous metals), universally from a standard for steel screws.

The countersunk head 4 has, starting from the conical surface 6 at its side facing the threaded shaft 2 opposite side a projecting peripheral edge 19 with an outer Periphery 20 which is larger in diameter compared to the conical surface 6 (Fig. 1). This is on the underside between the peripheral edge 19 and the conical surface 6, a transition 21 is formed. This transition 21 is practically in the range of Ribbed protrusions "filled" so that the rib-shaped projections 16 with the contact surfaces 18 of FIG. 1 from the outer periphery 20 corresponding to the angle β to the conical surface 6 extend. According to FIG. 2, the rib-shaped projections 16 extend starting from the outer periphery 20 of the countersunk head 4 substantially in the radial direction at least up to the region of an axial projection of the outer thread edge of Thread 14 of the threaded shaft 2. In the example shown forming the rib-shaped projections 16 approximately at a rate determined by the threaded axial projection and thus the nominal thread diameter D corresponding circle 22 (Figs. 2 and 4), they but could also be further inward in direction of the cylindrical Kems 12, d. h. extend in the threaded shell region inside.

Further, in the illustrated embodiments, six ribbed protrusions 16 similar design and in uniform, radially symmetrical peripheral distribution provided. but the number of the ribbed protrusions 16 may also range from three to eight, for example, are. Here each ribbed protrusion 16 is shown in FIG. 2 and 4 with respect to the shape of its bearing surface 18 substantially as a circular ring segment (Sector) with approximately radially extending flanks 24, 26 are formed (see also FIG. 3). In the embodiment shown in Fig. 4, the flanks run 24, 26, however, such a minor "via radial", ie more or from the inside to the outside stronger than at exactly radial flanks diverge, that each ribbed protrusion 16 in Compared to a model with exactly radially extending edges (as shown in Fig. 2 and shown in Fig. 4 based on dot-dash lines 28 in phantom) on the inner periphery is narrower (or wider on the outer periphery). This is in contrast to FIG. 2 according to FIG. 4, an intersection 30 of two by the flanks 24, 26 certain Boundary lines not (shown in dashed lines) 32 in the axial center X the screw (as is the case in Fig. 2) but radially between this and the respective ribbed protrusion 16th

As further seen in FIG. 3, close to the respective ribbed protrusion 16 in Circumferentially delimiting flanks 24, 26 with the respective foot of the fin approach 16 adjacent surface (conical surface 6) has a flank angle φ greater than / equal 90 °. Here it is preferably provided that during rotation in a screwing- (Arrow 34) forwardly facing edge 24 a steeper flank angle φ₁ which lies between 90 ° and maximum 95 °, while the other flank 26 preferably has a flatter flank angle φ₂ of greater than / equal to 95 °. By the steeper flank angle φ₁ forming the front edge 24 advantageously a kind Milling edge, which improves the milling effect when sinking. The flatter flank angle φ₂ the other flank 26 allows easier unscrewing the Countersunk. 1

In a further advantageous embodiment of the countersunk screw 1, the thread 14 FIG. 1 is a flank angle γ in the range of about 35 °. The slope S of Thread 14 hanging from the thread nominal diameter D, and is, in particular, about 60% of the nominal diameter D.

The invention is not shown to the embodiments described and limited, but includes all the same effect within the meaning of the invention Versions. Furthermore, the invention has so far not yet in the claim 1 defined combination of features, but may also be any other combination of specific features of all disclosed Individual features to be defined. This means that in principle, virtually any Individual feature of claim 1 is omitted or a by at least somewhere else Place of registration individual feature disclosed may be replaced. insofar is the claim 1 merely as a first attempt at formulating an invention to understand.