Screw-locking washer

Abstract

The invention relates to a screw-locking washer for arrangement between a screw head of a screw and a flat support surface having an elongated hole through which the screw is guided, the screw-locking washer comprising a washer top side (2) and a washer bottom side (3) facing the support surface, wherein the washer body (1) is convex, characterised in that the washer top side (2) of the washer body (1) is provided at its outer periphery with a circumferential rib (5).

Description

[0001] Lawyer's file 25171

[0002] August 13, 2024

[0003] Screw locking washer

[0004] The invention relates to a screw locking washer for arrangement between a screw head of a screw and a flat surface which has an elongated hole through which the screw is guided.

[0005] The purpose of locking washers is to counteract loosening processes in bolted connections. Such loosening processes result from a loss of preload in the bolted connections, which occurs as a consequence of settling and / or creep processes in the bolted parts.

[0006] To counteract such loosening processes, screw locking washers have a spring effect, the spring force of which is dimensioned in such a way that they can compensate for a loss of preload caused by settling and / or creep processes to such an extent that the clamping force required for the operational safety of the screw connection is maintained.

[0007] Slotted screw connections are frequently used in practice. These are particularly useful during assembly to compensate for tolerances between the components being mounted. Locking washers according to DIN 6796-2009-08 are regularly used to secure the screw connection against loosening. Wedge washer pairs or thick locking washers are used to further prevent the screw connection from loosening on its own.

[0008] The particular challenge with slotted screw connections is that the locking element used should not deflect within the contact surface interrupted by the slot. Deflection of the locking element would result in the washer having only a linear contact surface with the mating surface. Consequently, the yield strength of the clamped materials would be exceeded, potentially leading to increased settling and creep, which could result in the screw connection loosening.

[0009] In electrical screw connections, a deflection of the screw locking element would result in an additional lack of a uniform pressure cone in the screw connection, which would impair the current transmission properties.

[0010] To prevent deflection of the locking elements, their thickness is dimensioned such that deflection in the interrupted bearing area of ​​the slotted hole is minimized by using more material. Often, additional washers are even used in slotted connections to prevent surface damage caused by the outer diameters being indented. Such a connection is not only very complex; it also has the disadvantage of limited suitability due to the increased settling caused by the additional gaps created by the washers.

[0011] This is where the present invention comes in. The invention is based on the objective of providing a screw locking washer for arrangement between the screw head of a screw and a flat surface having an elongated hole through which the screw is guided, which requires less material. According to the invention, this objective is achieved by a screw locking washer with the features of the characterizing part of claim 1.

[0012] The invention provides a screw-locking washer for placement between the head of a screw and a flat surface having a slot through which the screw is guided, requiring less material. Because the outer surface of the washer body is provided with a circumferential rib, deflection of the washer body is prevented even with reduced thickness. In a further development of the invention, the outer edge of the washer body transitions seamlessly into the circumferential rib. This ensures uniform force distribution across the washer body via the rib.

[0013] In this embodiment of the invention, the upper surface of the disc transitions into the web in an arc-shaped manner when viewed in cross-section. This reduces notch effects, thereby further promoting a uniform force distribution into the web.

[0014] In a further embodiment of the invention, the circumferential web has a concave groove on its inner side. This prevents notch effects that could lead to uneven force absorption by the disk body.

[0015] In a further development of the invention, the underside of the disc transitions into the outer edge in an arc-like fashion. This creates a skid-like support for the locking element in the untensioned state, enabling a sliding displacement along the support surface when the locking element is tensioned.

[0016] In one embodiment of the invention, the upper surface and / or the lower surface of the disc body are provided with a locking edge profile. This prevents the disc body from rotating. Preferably, the locking edge profile is formed by at least two concentric arrangements of wedge-shaped elements arranged in a ring.

[0017] Other embodiments and configurations of the invention are specified in the remaining dependent claims. An exemplary embodiment of the invention is illustrated in the drawings and is described in detail below. The drawings show:

[0018] Figure 1 shows a schematic spatial representation of a screw locking washer;

[0019] Figure 2 shows the screw locking washer from Figure 1 in a top view; Figure 3 shows a schematic three-dimensional representation of a section of the locking washer from Figure 1, and

[0020] Figure 4 shows another schematic spatial representation of a section of the locking washer from Figure 1.

[0021] The screw-locking washer chosen as an exemplary embodiment is made of spring steel and comprises an annular, convex washer body 1 with a material thickness of 2.1 mm. Alternatively, the screw-locking washer can also be made of stainless steel. The washer body 1 has a top surface 2, a bottom surface 3, and an outer edge 4. A web 5 is arranged circumferentially on the outer surface of the top surface 2, and is integral with the washer body 1. The outer edge 4 transitions seamlessly into the web 5, the outer surface of which forms a common plane with the outer edge surface.

[0022] In cross-sectional view, the underside surface of the disc transitions in an arc into the outer edge surface, forming a circumferential skid 6. Furthermore, in cross-sectional view, the upper surface of the disc transitions in an arc into the web 5, which in the exemplary embodiment has a concave groove 7 on its inner side (see Figures 3 and 4).

[0023] A locking edge profile 8 is incorporated into the upper surface of the disc 2, which is formed by four concentric arrangements of ring-shaped wedge bodies 81 arranged next to each other.

[0024] In an experiment, the behavior of the screw locking washer designed in this way was compared to the behavior of a clamping washer according to DIN 6796 - 2009-08 with a material thickness of 2.5 mm:

[0025] A 2 mm thick test plate with a slotted hole was screwed to both sides of a 2.5 mm thick clamping washer according to DIN 6796-2009-08 using a screw that passed through the slotted hole and the two clamping washer. An identical test plate was screwed to both sides of a 2.1 mm thick locking washer according to the invention using a screw that passed through the slotted hole and the two locking washer. The screw connections were made according to DIN 25201-3-2015-12 with a preload of 31 kN in each case. The distance between the two washers of each connection was then measured using a feeler gauge. The gap between the two clamping washer was 1.65 mm. For the locking washer according to the invention, the gap was 1.75 mm. This shows that the clamping washer—despite its greater material thickness—exhibits a greater deflection than the locking washer according to the invention.

Claims

Patent claims 1. Screw locking washer for arrangement between a screw head of a screw and a flat surface which has an elongated hole through which the screw is guided, with a washer top (2) and a washer bottom (3) facing the surface, wherein the washer body (1) is convex, characterized in that the washer top (2) of the washer body (1) is provided on the outside with a circumferential rib (5).

2. Screw locking washer according to claim 1, characterized in that the outer edge (4) of the washer body (1) transitions seamlessly into the circumferential web (5).

3. Screw locking washer according to claim 1 or 2, characterized in that the upper surface of the washer (2) transitions in cross-sectional view into the web (5) in an arc-shaped manner.

4. Screw locking washer according to one of the preceding claims, characterized in that the circumferential web (5) has a concave groove (7) on its inner side.

5. Screw locking washer according to one of the preceding claims, characterized in that the underside (3) of the washer transitions in a cross-sectional arc into the outer edge (4).

6. Screw locking washer according to one of the preceding claims, characterized in that the upper surface (2) and / or the lower surface (3) of the washer body (1) is provided with a locking edge profile (8).

7. Screw locking washer according to claim 6, characterized in that the locking edge profile (8) is formed by at least two concentric arrangements of ring-shaped wedge bodies (81 ) arranged next to each other.

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