Self-tapping screw

Abstract

The invention relates to a self-tapping screw (1) having a cylindrical shaft (2) with a central axis (3), to which a conical tip (5) is coaxially connected, and having radially projecting cutting edges (6), which extend helically on the shaft (2) and the tip (5) into a plurality of windings (W), the distance between two adjacent windings (W) in the axial direction (R) being the pitch (H) of the screw (1), and wherein the shank (2) is provided with a transverse recess (7) which interrupts at least one winding (W) of the cutting edge (6) and cuts into the shank (2) up to half of its diameter (D1); and wherein the tip (5) is free of any recess (7) and the end (9) of the recess (7) facing away from the tip (5) has a distance (C1) from the tip (5), which distance is at most five pitches (H).

Description

Technical Field

[0001] The present invention relates to a self-tapping screw having a cylindrical shank with a central axis and radially protruding cutting edges, a conical tip coaxially connected to the cylindrical shank, the cutting edges extending helically on the shank and the tip into a plurality of windings, wherein the distance between two adjacent windings in the axial direction is the screw pitch, and wherein the shank is provided with a transverse recess that interrupts at least one winding of the cutting edges and cuts into the shank to at most half its diameter. Background Technology

[0002] This type of screw is known, for example, from documents AU200027716A1 and CN201747735U. The recessed section interrupts the cutting edge with each turn, creating a sharp cutting tip that acts in the circumferential direction and helps to cut the thread into the component as the screw is being screwed in.

[0003] Various embodiments of such cutting recesses are known in the prior art. Known solutions have the following drawbacks: they either excessively weaken the screw, providing insufficient cutting support, or they cause the screw to become misaligned while being screwed in. The object of the present invention is to overcome these drawbacks and create an improved self-tapping screw. Summary of the Invention

[0004] This objective is achieved by the type of self-tapping screw described at the beginning, which, according to the present invention, is distinguished by having no recess at the tip and having a distance from the tip at the end of the recess facing away from the tip, which is at most five pitches.

[0005] The cutting recess according to the present invention solves several problems of self-tapping screws. Since the recess does not extend to the tip, the centering effect of the tip is not compromised when the screw is being screwed in. Furthermore, the recess is located just behind the tip, i.e., its position on the screw is sufficiently forward to minimize the reduction in torsional strength during screwing and tensile strength in the screwed-in state. The portion of the screw located between the recess and the tip, connected via the weakened area of ​​the shank left by the recess, is also minimized, as is the number of windings present in this portion that are subjected to circumferential friction during screwing. Simultaneously, the recess's position behind the tip ensures that the cutting edge cuts the thread into the component at full outer diameter, improving the cutting effect.

[0006] The screws according to the invention cut the threads into the component particularly gently, thereby reducing the risk of cracking or breaking of the component during screwing, especially when the component is made of wood. This means that the minimum distance to be maintained from the edge of the component can be reduced. This has particular advantages in timber engineering, such as when connecting main beams, secondary beams or crossbeams, cross braces, trusses, supports, columns, walls, and other components. The components to be connected herein are typically made of glued laminated lumber (GLT), and adhering to the minimum edge distance for screw connections to prevent wood cracking is crucial. A smaller minimum edge distance allows for the use of smaller timber sections with the same strength, resulting in reduced costs and simplified operation.

[0007] Preferably, the end of the recess facing away from the tip has a distance from the tip that is at most four pitches. Thus, the recess is positioned particularly close to the tip, ensuring that the torsional and tensile strength of the largest possible portion of the screw is not compromised by the recess.

[0008] In a particularly advantageous embodiment, the recessed end facing the tip has a distance from the tip that is at least half a pitch and at most three pitches, particularly preferably one or two pitches. This leaves a very short area between the tip and the recess, in which only a very small but sufficient number of full-diameter windings with cutting edges exist, which helps to center the screw during screwing.

[0009] When viewed along the axial direction, the recess can, for example, have the shape of a circular arc. This shape can be produced particularly easily by grinding, milling, rolling, stamping, or upsetting. Alternatively, when viewed along the axial direction, the recess can have the shape of a circular sector, such as one-third, one-quarter, or one-fifth of a circle. For example, multiple recesses can be provided at different circumferential positions on the rod.

[0010] Preferably, when viewed perpendicular to a plane containing the axis, the recess has a rectangular, circular, or elliptical shape. These shapes can also be easily produced by milling, grinding, rolling, stamping, or upsetting.

[0011] In another preferred embodiment of the invention, the protrusion height of the cutting edge at the tip gradually decreases towards the tip. This measure helps with centering when the screw is screwed in and with the thread cutting the component, while protecting the component as much as possible.

[0012] Particularly advantageous is that the depth of the recess is 10% to 50% of the diameter of the rod, preferably 35% to 45%. This achieves an excellent compromise between minimizing the weakening effect of the recess on the one hand and maximizing its cutting effect on the other.

[0013] In all these embodiments, it is preferred that the shank transitions to a cylindrical portion at its end away from the tip via an enlarged transition portion having a diameter larger than that of the shank, to which a head for engaging the tool is connected. The enlarged cylindrical portion can serve as a guide portion for screws in fittings with cylindrical bores, and provides good force transmission from the head to the shank during screwing.

[0014] Preferably, the head has a diameter larger than that of the cylindrical portion, and a shoulder is formed between the head and the cylindrical portion. The shoulder can serve as a support surface for fittings that are screwed onto the component. At the same time, the enlarged head provides sufficient space for engagement of corresponding tools such as hexagonal sockets, hexagonal flower-shaped tool interfaces, etc. Attached Figure Description

[0015] The present invention will now be described in more detail based on exemplary embodiments shown in the accompanying drawings. In the drawings:

[0016] Figure 1 A side view of a first embodiment of the screw of the present invention is shown;

[0017] Figure 2 It shows Figure 1 A top-view perspective of the screw;

[0018] Figure 3 An axial normal cross-sectional view at the height of the recess is shown for a second embodiment of the screw of the present invention;

[0019] Figure 4 The third embodiment of the screw of the present invention is shown with Figure 3 Similar axial normal section diagrams; and

[0020] Figure 5 A side view of a fourth embodiment of the screw of the present invention is shown. Detailed Implementation

[0021] Figure 1 and Figure 2 A self-tapping screw 1, to be screwed or screwed into a component (not shown), is shown. The component is made of, for example, wood or plastic. The screw 1 has a cylindrical shank 2 with a central axis 3. At one (rear) end, a head 4 is connected to the shank 2, and at the other (front) end, a conical tip 5 with a base ring B and a apex S is connected to the shank. A cutting edge 6 extends helically around the shank 2 and tip 5, forming several windings W. Each winding W extends 360° around the axis 3 when viewed along the direction of the axis 3 (which is the axial direction R). The distance between two adjacent windings W in the axial direction R is the pitch H of the screw 1.

[0022] In the longitudinal section including axis 3, the cutting edge 6 has a generally triangular or trapezoidal shape and protrudes from the surface of the shank 2 or the surface of the tip 5 with a protrusion height A measured perpendicular to axis 3. The protrusion height A from the shank 2 is 5% to 20% of the diameter D1 of the shank 2. At the tip 5, the cutting edge 6 gradually tapers towards the apex S, that is, its protrusion height A at the tip 5 gradually decreases from the base B connected to the shank 2 towards the tip S of the tip 5, wherein, as shown in the attached... Figure 1 As shown, it is able to reach the zero value before the top S.

[0023] The rod portion 2, including a spiral cutting edge 6 extending therefrom, is provided with a transverse recess 7, wherein at least one winding W of the cutting edge 6 is interrupted.

[0024] like Figure 2 As shown, the recess 7 leaves a cutting tip SP from the cutting edge 7 at the point where it is interrupted.

[0025] The depth E of the recess 7 into the rod 2, measured perpendicular to axis 3 and the deepest region of the recess 7, is 10 to 50% of the diameter D1 of the rod 2, preferably 35 to 45%, and particularly preferably about 40%. Therefore, the minimum thickness of the region 8 left by the rod 2 at the height of the recess 7 is 90 to 50% of the diameter D1 of the rod 2, preferably 65 to 55%, and particularly preferably about 60%.

[0026] There is no recess 7 in the tip 5, that is, even in the case of multiple recesses 7 as described later, the tip 5 has no recesses 7. However, the recesses 7 are very close to the tip 5, that is, arranged as close as possible behind the tip 5. For example, the end 9 of the recess 7 facing away from the tip 5 has a distance C1 from the tip 5, i.e., its base B, which is at most five pitches H, preferably at most four pitches H. The end 10 of the recess 7 facing the tip 5 has a distance C2 from the tip 5, which is at least zero and at most four pitches H, preferably at least half a pitch and at most three pitches H, and especially preferably one or two pitches H.

[0027] like Figure 2 As shown, when viewed along the axial direction R, the recess 7 can have the shape of a circular arc. Figure 3 and Figure 4 An alternative embodiment is shown, wherein each of the recesses 7 has the shape of a circular sector or an elliptical sector when viewed along the axial direction R. Figure 4An option is shown to provide more than one recess 7 distributed on the circumference of the rod portion 2. In the case of multiple recesses 7, each individual recess satisfies the conditions for recess 7 described above. In particular, each recess 7 remains away from the tip 5, and its respective tip-facing end 9 has a distance C1 not greater than five pitches H. However, the recesses 7 can also be constructed differently in other cases.

[0028] When viewed perpendicular to a plane containing axis 3, the recess 7 can have a rectangular shape, such as... Figure 1 As shown. Other shapes are also possible as alternatives, for example... Figure 5 The shape of the circular or elliptical bow shown.

[0029] The end of the rod 2 away from the tip 5 can be designed in various ways for engagement with tools or screwdrivers. For example, this end can be directly fitted with an internal hexagonal socket, etc. In the example shown, a frustum-shaped transition portion 11 connects to the end of the rod 2 away from the tip 5, and the transition portion 11 transitions to a cylindrical portion 12 having a diameter D2 larger than the diameter D1 of the rod. The cylindrical portion 12 can, for example, be used for guidance in a cylindrical hole of an accessory that is screwed into a component using a screw 1.

[0030] The head 4 can then be connected to the cylindrical portion 12. For example, the head 4 can then have a cylindrical portion 13 having a diameter D3 larger than the diameter D2 of the cylindrical portion 12, such that a shoulder 15 is formed between the two. An enlarged countersunk portion 14 is then connected to the cylindrical portion 13, the enlarged countersunk portion having a slotted or Phillips head recess for engaging a screwdriver, or having an internal hexagonal socket, internal hexagonal tip interface, or other type of interface 16 for engaging a tool for tightening the screw 1.

[0031] Screw 1 can be made of any material, such as plastic or metal, especially steel or stainless steel.

[0032] This invention is not limited to the embodiments shown, but covers all variations, modifications and combinations thereof that fall within the scope of the appended claims.

Claims

1. A self-tapping screw having a cylindrical shank (2) with a central axis (3) and radially projecting cutting edges (6), a conical tip (5) coaxially connected to the cylindrical shank, the cutting edges extending helically on the shank (2) and the tip (5) into a plurality of windings (W), wherein, The distance between two adjacent windings (W) in the axial direction (R) is the pitch (H) of the screw (1), and wherein the shank (2) is provided with a transverse recess (7) that interrupts at least one winding (W) of the cutting edge (6) and cuts into the shank (2) to at most half of its diameter (D1), characterized in that the tip (5) has no recess (7), and the end (9) of the recess (7) opposite to the tip (5) has a distance (C1) from the tip (5) that is at most five pitches (H).

2. The screw according to claim 1, characterized in that, The end (9) of the recess (7) facing away from the tip (5) has a distance (C1) from the tip (5) that is at most four pitches (H).

3. The screw according to claim 1 or 2, characterized in that, The end (10) of the recess (7) facing the tip (5) has a distance (C2) from the tip (5) that is at least half a pitch and at most three pitches (H).

4. The screw according to claim 3, characterized in that, The end portion (10) of the recess (7) facing the tip (5) has a distance (C2) from the tip (5) that is one to two pitches (H).

5. The screw according to any one of claims 1 to 4, characterized in that, When viewed along the axial direction (R), the recess (7) has the shape of a rounded bow.

6. The screw according to any one of claims 1 to 4, characterized in that, When viewed along the axial direction (R), the recess (7) has the shape of a circular sector or an elliptical sector.

7. The screw according to any one of claims 1 to 6, characterized in that, When viewed perpendicular to a plane containing the axis (3), the recess (7) has a rectangular shape.

8. The screw according to any one of claims 1 to 6, characterized in that, When viewed perpendicular to a plane containing the axis (3), the recess (7) has the shape of a circular bow or an elliptical bow.

9. The screw according to any one of claims 1 to 8, characterized in that, The protrusion height (A) of the cutting edge (6) on the tip (5) gradually decreases toward the tip (S) of the tip (5).

10. The screw according to any one of claims 1 to 9, characterized in that, The depth (E) of the recess (7) is 10-50% of the diameter (D1) of the rod (2), preferably 35-45%.

11. The screw according to any one of claims 1 to 10, characterized in that, The rod (2) transitions to a cylindrical portion (12) at its end away from the tip (5) via an enlarged transition portion (11), the cylindrical portion having a diameter (D2) larger than that of the rod (2), and a head (4) for engaging the tool is connected to the cylindrical portion (12).

12. The screw according to claim 11, characterized in that, The head (4) has a diameter (D3) larger than that of the part (12), and a shoulder (15) is formed between the head (4) and the part (12).

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