locking washer

Abstract

A locking washer for securing a screw connection, wherein the locking washer (2, 3) has a first flat side and a second flat side and at least one of the two flat sides of the locking washer (2, 3) has a clamping structure (9, 9.1) provided by a plurality of radial ribs, characterized in that a first number of radial ribs R1) have a first height and a second number of radial ribs (R2, R3) have a second height, wherein the second height is less than the first height, and that the radial ribs (R1) of the first number are separated from each other individually or in groups by at least one radial rib (R2, R3) of the second number.

Description

[0001] The invention relates to a locking washer for securing a screw connection, wherein the locking washer has a first flat side and a second flat side and at least one of the two flat sides of the locking washer has a clamping structure provided by a plurality of radial ribs.

[0002] Screw connections often need to be secured against accidental loosening, especially those subject to dynamic loads. For this purpose, lock washers are used that are either structured with clamping structures or have clamping structures on at least one of the two flat sides. The purpose of these clamping structures is to press them at least partially into the surface of the adjacent abutment, for example the underside of a screw head or part of a clamping arrangement. In addition to lock washers made of spring steel and having clamping elements formed by incisions and exposed relative to the washer plane, lock washers are also known whose at least one flat side has clamping structures formed by embossing.The embossed interlocking structures of previously known lock washers consist of radial ribs that protrude from the surface of the lock washer. It is also known to structure the flat side bearing the interlocking structures with a multitude of such ribs, each of which has a radial extension. These ribs have an asymmetric cross-sectional geometry when viewed in the circumferential direction. Radial ribs are interlocking structures that extend in the radial direction of the lock washer. This creates a clamping edge directed in the screwing direction. During the screwing process, this edge is pressed into the abutment, for example, into the underside of a screw head, so that loosening is only possible against the opposing clamping edge.In order for such a clamping structure to be pressed into the surface of an abutment during the process of tightening the screw connection, either the entire locking washer is made of a material that is harder than the abutment or at least the surface of the washer with the surface of the clamping structure is hardened and thus harder than the material into which the clamping structure is to be pressed to effect the desired anti-rotation lock.

[0003] Lock washers which have radial ribs as clamping structures on one of their flat sides can, if they are intended for use in a pair of wedge lock washers, have wedge surfaces on their other washers surface.

[0004] In such lock washers, the clamping structure serves the purpose of creating a positive connection with the adjacent part of a clamping connection. For example, with wedge lock washers, it is desirable that when the clamping connection is clamped, the wedge lock washer that rests against the stationary part of the clamping connection presses its clamping structure into the material of the adjacent part right at the beginning of the clamping process, thus providing a positive connection and thus preventing the wedge lock washer from rotating during the clamping process.To optimize this, US 2021 / 372442 A1 proposes that the radial ribs be located only in a radially limited annular section on the lock washer, in order to achieve a force concentration with the aim of ensuring that even at a low applied clamping force, these radial ribs press into the upper side of the part of the clamping connection that is in contact with them. However, the positive locking effect provided in this way sometimes does not meet the requirements placed on a clamping connection using such a lock washer or such a pair of lock washers with regard to the breakaway torque.

[0005] Based on this discussed prior art, the invention is therefore based on the object of proposing a locking washer of the type mentioned at the outset, with which a positive connection with the part lying on the clamping structure can be produced even at a low applied torque, but which also meets the requirements of a high breakaway torque.

[0006] This object is achieved according to the invention by a generic locking washer mentioned at the outset, in which a first number of radial ribs have a first height and a second number of radial ribs have a second height, the second height being less than the first height, and in which the radial ribs of the first number are separated from one another individually or in groups by at least one radial rib of the second number.

[0007] In this lock washer, the radial ribs are designed with different heights when viewed in the circumferential direction. A first number of radial ribs have a first height, while a second number of radial ribs have a second height which is, however, less than the first height. The height of a radial rib is measured by the distance of the highest point of such a radial rib from the adjacent recess. The deepest point of the recess separating two radial ribs is preferably located in a common washer plane. One or more radial ribs of the first number are arranged in an alternating sequence with one or more radial ribs of the second number, so that the flat side of the lock washer having the clamping structure rests evenly around the circumference on the surface of an adjacent part, for example a first component of a clamping arrangement.Because only a portion of the radial ribs are in contact with the surface of the component adjacent to the lock washer at the beginning of a clamping process, the clamping force caused by the applied torque is concentrated on this portion of the radial ribs. Consequently, these ribs can be pressed into the surface of the adjacent part even with a significantly lower clamping force acting on the lock washer, compared to a conventional design of such a lock washer, in which the radial ribs all have the same height in the circumferential direction.The radial ribs of the second number or, if the second number of radial ribs again has radial ribs of different heights, those with the greatest height of this number are only pressed into the surface of the adjacent part once the radial ribs of the first number have already formed a positive connection with the adjacent component. These ribs have been pressed in so far that when a higher clamping force is applied, the next higher radial ribs of the second number are also pressed into the material to reinforce the positive connection. In this way, with increasing clamping force, the positive connection is reinforced via an increasing number of radial ribs. With such a lock washer, the entire radial extent of the flat side of the lock washer can be used to form the radial ribs and thus for the positive connection.This positive locking effect, formed in the circumferential direction of the lock washer, is much more effective than a positive locking effect formed by radial ribs, which only extend over a relatively small portion of the lock washer's radial extent. By separating the radial ribs or grouped radial ribs of the first number from one another by interposing one or more radial ribs of the second number, the risk of shearing off the material of the adjacent part when a corresponding loosening torque is applied is significantly reduced.

[0008] A particular advantage of this type of clamping structure on the flat side of the lock washer is that, as the clamping force increases, additional radial ribs can be used successively in several steps to achieve the desired form fit with the part resting against the clamping structure. It is entirely possible that, in addition to the radial ribs of the first number with their greatest height, radial ribs of the second number with stepped heights viewed in the circumferential direction can be provided between these. With such a configuration, viewed in the circumferential direction, a radial rib of the first number is followed by a radial rib of the second number, specifically one that has the greatest height within the second number. This, in turn, can be followed by another radial rib of the second number that has a lower height than the one preceding it in the sequence.With such a stepped design, care is taken to ensure that the shorter radial ribs are only used for the positive locking action once the taller radial ribs have already been pressed into the adjacent part to a certain depth of penetration. In this way, with increasing clamping force and thus higher torque acting on the clamping device, such as a bolt head or nut, the positive locking action is improved by increasing numbers of radial ribs being pressed into the adjacent material. At the same time, the penetration depth of the taller radial ribs is increased.

[0009] The height differences between the different heights of the radial ribs do not need to be excessively large. Even a height difference of a few hundredths of a millimeter, for example, 2 / 100 - 3 / 100 mm, is sufficient to benefit from the advantages of this lock washer.

[0010] The clamping structure of this lock washer can be specifically adapted to the desired securing purpose. For example, the number of radial ribs in the first set can be fewer than that of the radial ribs in the second set. This allows for a precise adjustment of the force required to press the lock washer into the adjacent material to achieve an initial positive fit and prevent rotation during clamping. The height difference between the radial ribs in the first set can also be greater than the height difference between the radial ribs in the second set if this second set includes radial ribs of different heights.

[0011] If the second number of radial ribs comprises ribs of different heights, the sequence of the radial ribs differing in height can be designed to be the same in both circumferential directions of the lock washer.

[0012] In principle, it is preferred that the radial ribs with their different heights are arranged evenly distributed in the circumferential direction on the flat side of the locking washer carrying the clamping structure.

[0013] The radial ribs can have a straight extension in the radial direction. It is also possible for the radial ribs to have a vertex directed in the securing direction along their radial extension, for example, to be curved in this direction. Examples of the geometry of such clamping structures are disclosed in DE 20 2012 104 410 U1 of the applicant. By explicitly referring to the geometry of these previously known clamping structures, they are simultaneously made the subject of these explanations with regard to their geometry.

[0014] According to a preferred embodiment, the cross-sectional area of ​​the radial ribs is asymmetrical, with the steeper flank pointing in the desired securing direction.

[0015] The previously described clamping structure of the lock washer can be used through additional measures for the initial clamping force concentration. In one exemplary embodiment of such a lock washer, the material thickness is greater in an axially outer ring section than in a radially inner ring section. This means that at the beginning of a clamping process, the flat side of this lock washer bearing the clamping structure only rests on the surface of the adjacent part with the radially outer ring section. In this respect, when a clamping connection is clamped using such a lock washer, the clamping force is additionally concentrated on this axially outer ring section. As the clamping force increases, the radial rib sections further inward are also pressed into the material of the adjacent part.The decrease in material thickness from the axially outer ring section to the inner ring section preferably occurs continuously.

[0016] The locking washer according to the invention can, for example, be a wedge-lock washer. The flat side opposite the clamping structure is then structured with wedge surfaces. Typically, such a locking washer is used together with another such locking washer as a pair, thus forming a wedge-lock washer pair, in which the flat sides bearing the wedge surfaces are engaged with each other.

[0017] In a further development of such a pair of wedge lock washers, the two lock washers (wedge lock washers) have different outer diameters. The lock washer with the larger diameter bears the above-described clamping structure on its flat side facing away from the wedge lock washer with the smaller diameter. The lock washer with the larger diameter preferably has a rotary drive contour provided radially on the outside. This serves to support the torque of a clamping tool. The lock washer that is smaller than the lock washer with the larger diameter can also bear a similar clamping structure on its outside.

[0018] Regardless of its design, whether designed as a wedge lock washer or not, such a lock washer is typically manufactured from a ferrous metal, particularly steel or stainless steel, using a stamping and pressing process. If necessary, the lock washer can be hardened either entirely or at least on its flat side bearing the clamping structure.

[0019] The invention is described below using an exemplary embodiment with reference to the accompanying figures. They show: Fig. 1: A perspective view of a pair of locking washers designed as wedge lock washers, the locking washers of which are equipped with the clamping structure according to the invention on their flat sides facing away from each other, Fig. 2: an enlarged side view of the Fig. 1 upper locking washer in a development, Fig. 3: a cross-sectional view of the wedge lock washer pair of the Fig. 1 and Fig. 4: an enlarged detail of the cross-section of the Fig. 4.

[0020] A pair of wedge-lock washers 1 comprises two individually manufactured wedge-lock washers 2, 3. Each of the two wedge-lock washers 2, 3 has, on its side facing the other wedge-lock washers 3 or 2, the wedge-surface structuring with wedge surfaces typical of such wedge-lock washers. The wedge surfaces extend over the entire radial extent of the respective wedge-lock washers 2, 3. The wedge-surface structuring of the two wedge-lock washers 2, 3 is designed as is known for wedge-lock washers per se. The wedge-surface structuring is not tapered in the radial direction. The orientation of the wedge surfaces is designed such that the short flanks abut one another in the clamping direction (here: clockwise). The vertices formed by the wedge-surface structuring as positive structures of the wedge-surface structuring are each located in the same plane with regard to their radial extent.Both wedge-lock washers 2, 3 have a fastener opening 6, 6.1. The two wedge-lock washers 2, 3 are aligned with their fastener opening 6, 6.1 with their wedge surfaces facing each other and in the direction shown in . Fig. 1, the wedge-lock washers are connected to each other by an adhesive bond in the illustrated embodiment. The adhesive bond is designed to yield or break under shear stress. Such a shear stress occurs when at least one of the two wedge-lock washers 2, 3 is moved counter to the clamping direction. Thus, despite the adhesive bond between the two wedge-lock washers, the wedge-lock washers' functionality is maintained.

[0021] The wedge lock washer 2 has a larger outer diameter than the wedge lock washer 3. Its outer radial edge is structured by a rotational drive contour 7. The rotational drive contour 7 of the illustrated embodiment is designed in the manner of a toothing. The negative structures 8 serve to engage a torque support of a clamping tool. In this respect, the wedge lock washer 2 assumes the functionality of a reaction washer. Reaction washer types are known per se and therefore need not be explained in more detail in this context.

[0022] Both wedge-lock washers 2, 3 each have clamping structures 9, 9.1 on their flat sides facing away from each other. In the illustrated embodiment, the clamping structures 9, 9.1 are radial ribs, specifically those with an asymmetric cross-sectional geometry. The flatter flanks of these radial ribs are aligned in the opposite direction to the wedge surfaces on the other side of the washer. While the clamping structure 9 serves the purpose of being pressed and thus imprinted into the material surface of the adjacent component when clamping a clamping arrangement into which the pair of wedge-lock washers 1 is inserted, the clamping structure 9.1 of the wedge-lock washer 3 serves to provide friction-increasing means, which make it more difficult to loosen the adjacent clamping or abutment, i.e., a clamping nut, a bolt head, or a component.This does not exclude the possibility that this can also be embossed into the material of the counter bearing.

[0023] The following is with reference to Fig. 2, the clamping structure 9 of the larger-diameter wedge-lock washer 2 is explained. The clamping structure 9.1 of the smaller-diameter wedge-lock washer 3 is designed in the same way; only the shorter flank of this clamping structure 9.1 points in the opposite direction. The clamping structure 9 is formed by radial ribs R1, R2, R3 of different heights. The radial ribs R1 are the ones with the greatest height. The height of the radial ribs R1 is in Fig. 2 indicated by the dot-dash line. The outer end of the radial ribs R1 is located in a common disc plane. The radial ribs R2, R3 have a lower height and are the radial ribs belonging to the second number. The second number of radial ribs is divided into the radial ribs R2 and R3, whereby these radial ribs R2, R3 have a different height. The radial ribs R2, R3 of the second number have a lower height than the radial ribs R1. The radial ribs R2 have the greater height of the group of radial ribs of the second number. The height of the radial ribs R1, R2, R3 is measured from the common base (in Fig. 2 shown in dashed lines). Thus, the lowest point lies between two adjacent radial ribs in a common disc plane. Fig. The developed side view of the lock washer 2 shown in Figure 2 shows that adjacent to a radial rib R1 in both directions, there is a radial rib of the second number, namely a radial rib R2. This is followed by a radial rib R3, thus a radial rib with the smallest height. This alternating sequence is the same in both directions, viewed in the circumferential direction, and extends over the entire circumference of the wedge lock washer 2. To illustrate the height difference, Fig. 2 also indicates the height level of the radial ribs R3 (dash-two-dot signature).

[0024] In the wedge-lock washer 3, which is the smaller diameter washer in the illustrated embodiment, the two flat sides are arranged in parallel planes. This means that the clamping structures 9.1 have the same height across their radial extent.

[0025] Even if the wedge-locking washer 2, which in the illustrated embodiment is the larger one in diameter, has the vertices 5 of the wedge-surface structuring in one plane, the opposite flat side of this wedge-locking washer 2 is designed differently with regard to the height of the clamping structuring 9 in the radial direction. The height of the radial ribs serving as clamping structuring 9 decreases in the radial direction from the outside to the inside towards the fastener opening 6. This is shown in the detailed illustration of the Fig. 4. In an outer radial washer region 10, the height of such a radial rib remains constant. In this figure, the apex of the radial rib shown in section is identified by the reference symbol S. In the washer region 11, which borders the washer region 10 on the inside in the radial direction, the height of the radial ribs decreases in the direction of the fastener opening 6. Thus, the outer radial washer region 10 is located at a small but certain axial distance (distance in the axial direction) from the inner washer region 12. This distance is identified in this figure by "a". If the wedge-lock washer 2 contacts the surface of a component with its clamping structure 9, it only rests on the surface of the component with the radially outer washer region 10. In the Fig. 4, this disc region 10 ends in the radial outward direction due to the position of the section shown in the apex of a negative structure 8 of the rotational driving contour 7. In the sections of the wedge-lock disc 2 in which the positive structures of the rotational driving contour 7 are arranged, this outer disc region 10 extends into the region of the radially outer end of the wedge-lock disc 2.

[0026] In Fig. In Figure 4, the dashed line 13 indicates the trace of the continuation of the section of the apex S of the radial rib shown, located at the same height within the radially outer disk area 10. Also shown in this figure is a dash-dotted line 14, the depth line of the radial rib; thus, line 14 defines the virtual disk surface that remains unstructured.

[0027] The sectional views of the Fig. 3 and Fig.4 it can be seen that the radial extension of the wedge-locking washer 3 with a smaller diameter, starting from the fastener openings 6, 6.1 arranged in alignment with one another, extends approximately to the radial extension of the area 11 of the wedge-locking washer 2 and thus reaches approximately to the radially outer washer area 10.

[0028] Both wedge-lock washers 2, 3 are made of a steel material. At least the two flat sides, but typically the entire wedge-lock washers 2, 3, are coated with a zinc flake coating. The two wedge-lock washers 2, 3 are punched out of a blank in a first manufacturing step. The punching process provides the external shape of the two wedge-lock washers 2, 3. This also includes the provision of the fastener openings 6, 6.1. The flat sides are structured by a subsequent pressing process, whereby the structuring on both flat sides of each wedge-lock washers 2, 3 is created in a single pressing step. This takes place in a press equipped with appropriate forming tools.As a result, the surface material of the punched-out press blank is reshaped in order to form the wedge surface structuring on one flat side and the respective clamping structures 9, 9.1 on the other flat side. This reshaping leads to work hardening of the produced structures, which is particularly advantageous for the clamping structures 9, 9.1, as these are not only formed by this reshaping process, but are also hardened compared to the remaining material of the respective wedge-locking disc 2, 3. The zinc flake coating was naturally only applied to each wedge-locking disc 2 or 3 after the forming process was completed. In the illustrated embodiment, the discs structured by embossing were hardened by heat treatment. The disc is thus hardened as a whole and has been brought to a hardness that significantly exceeds that which can be achieved solely by work hardening.In a subsequent step, the two wedge-lock washers 2, 3 were each bonded together by an adhesive bond with their flat sides bearing the wedge surface structure facing each other.

[0029] The invention has been described using exemplary embodiments. Without departing from the scope of protection described by the applicable claims, numerous further embodiments for implementing the inventive concept will become apparent to those skilled in the art without the need for further explanation within the scope of these statements. List of reference symbols 1 pair of wedge lock washers 2 wedge lock washers 3 wedge lock washer 6, 6.1 Fastener opening 7 Rotary driving contour 8 Negative structure 9, 9.1 Bracketing structuring 10 outer disc area 11 Disc area 12 inner disc area 13 Line 14 Line S vertex a distance QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 2021 / 372442 A1

[0004] DE 20 2012 104 410 U1

[0013]

Claims

[1] Locking washer for securing a screw connection, wherein the locking washer (2, 3) has a first flat side and a second flat side and at least one of the two flat sides of the locking washer (2, 3) has a clamping structure (9, 9.1) provided by a plurality of radial ribs, characterized by that a first number of radial ribs (R1) have a first height and a second number of radial ribs (R2, R3) have a second height, wherein the second height is less than the first height, and that the radial ribs (R1) of the first number are separated from one another individually or in groups by at least one radial rib (R2, R3) of the second number. [2] Locking washer according to claim 1, characterized by that the second number of radial ribs (R2, R3) consists of radial ribs with at least two different heights. [3] Locking washer according to claim 2, characterized bythat, viewed in the circumferential direction of the locking washer (2, 3), starting from a radial rib (R1) of the first number, a radial rib of the second number with the greatest height follows, followed by one with the next lower height, until a radial rib (R3) with the lowest height from the second number of radial ribs (R2, R3) ends the above-described sequence of radial ribs (R1, R2, R3) with decreasing height. [4] Locking washer according to claim 3, characterized by that the sequence of radial ribs (R1, R2, R3) of varying height is the same in both circumferential directions of the lock washer (2, 3). [5] Locking washer according to one of claims 1 to 4, characterized by that the radial ribs (R1, R2, R3) are designed with an asymmetrical cross-sectional geometry, with the steeper flank pointing in the desired securing direction. [6] Locking washer according to one of claims 1 to 5, characterized bythat the material thickness of the locking washer (2) is greater in a radially outer washer area (10) than in a radially inner washer area (12). [7] Locking washer according to claim 6, characterized by that the material thickness of the locking washer (2) decreases continuously from the axially outer washer area (10) to the radially inner washer area (12). [8] Locking washer according to one of claims 1 to 7, characterized by that the locking washer (2, 3) is a wedge locking washer and that the flat side opposite the flat side with the clamping structure (9, 9.1) carries the wedge surfaces. [9] Locking washer according to claim 8, characterized by that the locking washer (2, 3) together with another washer (3, 2) designed as a wedge locking washer forms a pair of wedge locking washers (1) which are arranged so as to cooperate with their wedge surfaces. [10] Locking washer according to claim 9, characterized by that the two locking washers (2, 3) have a different outer diameter and the locking washer (2) with the larger diameter carries the clamping structure (9) on its flat side facing away from the locking washer (3) with the smaller outer diameter. [11] Locking washer according to claim 10, characterized by that the locking washer (2) with the larger outer diameter is structured radially on the outside by a rotary driving contour (7) for torque support of a clamping tool.

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