Rotatable connector assembly with radial locking mechanism

Abstract

A rotatable connector assembly comprising a first connector element and a second connector element, the latter comprising a substantially circular hollow cylindrical section. The first connector element and the second connector element can be at least partially nested within one another in a connected state and are rotatable relative to each other in this connected state. The substantially circular hollow cylindrical section of the second connector element has locking teeth on its circumference, which, in the connected state, face the first connector element. The first connector element includes at least one spring element comprising a plurality of spring lugs, each configured to engage between two adjacent locking teeth of the second connector element in the connected state.The second connector element comprises a retaining ring which includes a ring-shaped and radially inward-pointing retaining section which, in the connected state, engages in a groove provided on an outside of the circular hollow cylindrical section of the second connector element.

Description

Background of the invention

[0001] The invention relates to a rotatable connector assembly with radial locking, such as those used, for example, in angled connector housings that are attached to a unit.

[0002] Angled connector housings consist of a connector part on the unit side, which is attached to a unit, and an output connector part arranged at an angle to it. The output connector part is rotatable around the longitudinal axis of the connector part on the unit side. In operation, the rotational position of the output connector part must be adjustable to adapt the angled connector housing to the respective operating conditions. Furthermore, the selected rotational position must be held securely and insensitive to vibrations. Consequently, a certain minimum torque must be required to rotate the output connector part, and a secure locking mechanism must be maintained in the selected rotational position. This secure locking mechanism and the minimum torque requirement must be maintained even after numerous rotations. State of the art

[0003] From DE 298 13 455 U1, a rotatable connector assembly is known, comprising an outer connector part with a polygonal cross-section along its inner circumference, the polygonal surfaces of which are fitted with leaf springs, and an inner connector part with a polygonal cross-section along its outer circumference, which is arranged within the outer connector part. In a locked position, the polygonal surfaces of the inner connector part rest against the leaf springs. Depending on the selected spring force, this produces only a conditionally stable locking action. When the two connector parts are rotated relative to each other, outer edges of the inner connector part press against the leaf springs, causing wear and leading to rounding of the inner connector part. Due to the rounding of the inner polygonal connector part, the torque required for rotation decreases, and consequently, a stable locking action can no longer be guaranteed.Furthermore, twisting the plug parts creates abrasion that can damage the unit.

[0004] From EP 1 753 092 A1, a rotatable connector assembly is known, comprising a first connector element and a second connector element, which is essentially circular and hollow cylindrical in shape. The first connector element and the second connector element are at least partially nested and rotatable relative to each other. The second connector element has locking teeth on its circumference facing the first connector element. A plurality of radially movable locking pins and a plurality of spring elements are arranged in the first connector element, each spring element pressing a locking pin radially towards the locking teeth of the second connector element. The provision of multiple spring elements and multiple locking pins makes the assembly of the connector assembly relatively complex.Furthermore, a retaining ring is required to axially secure the first and second connector elements; this ring is held in place solely by spring tension, which may result in insufficient securing. Additionally, disassembly of the connector assembly is either impossible or only possible with considerable effort and without causing damage.

[0005] Document EP 1 465 293 A2 discloses an angled connector comprising a plug part and a flange part, wherein the plug part is rotatable relative to the flange part to determine the exit direction. The plug part is attached to the flange with rotational resistance by means of at least one retaining ring which engages in an annular groove. For this purpose, the annular groove has circumferentially extending ridges on both opposite sides, which force the retaining ring into the shape formed by the ridges and deform the retaining ring according to the ridge shape during rotation. Object of the invention

[0006] It is an object of the invention to provide a rotatable connector assembly that solves at least one of the problems described above and / or a related problem. Inventive solution

[0007] According to the invention, the problem is solved by a rotatable connector assembly comprising a first connector element and a second connector element, the latter comprising a substantially circular hollow cylindrical section. The first connector element and the second connector element can be at least partially arranged one inside the other in a connected state and can be rotated relative to each other in this connected state. The substantially circular hollow cylindrical section of the second connector element has locking teeth on its circumference, which face the first connector element in the connected state. The first connector element includes at least one spring element comprising a plurality of spring lugs, each configured to engage between two adjacent locking teeth of the second connector element in the connected state.The second connector element comprises a retaining ring which includes a ring-shaped and radially inward-pointing retaining section which, in the connected state, engages in a groove provided on an outside of the circular hollow cylindrical section of the second connector element. Advantages, design and further development of the invention

[0008] Because the spring element comprises multiple locking lugs, no additional pins are required, and the number of spring elements needed can be reduced (for example, to one). This can simplify the manufacturing, assembly, and / or disassembly of the connector assembly. In particular, non-destructive disassembly may be possible. Replacing the spring element, including its locking lugs, for example, to change a minimum torque, can also be simplified.

[0009] In the rotatable connector assembly, the first connector element and the second connector element can be designed in such a way that, in the connected state, a positive locking connection between the first connector element and the second connector element is ensured with respect to an axially acting force.

[0010] In the rotatable connector assembly, the second connector element comprises a retaining ring with an annular, radially inward-projecting retaining section. When connected, this section engages in a groove on the outer side of the circular hollow cylindrical section of the second connector element. The retaining section can, for example, have a rectangular cross-section or a rectangular cross-section with rounded corners. Alternatively, the retaining section can be configured as an annular projection extending radially inward from an annular base section of the retaining ring. Thus, the retaining ring can, for example, have a substantially L-shaped cross-section. However, the retaining ring can also be configured with a rectangular cross-section. The provision of the retaining ring and the associated groove ensures axial locking.

[0011] The retaining ring can be designed either as a completely closed ring or as an open ring. If the retaining ring is provided as a ring with an opening, its radius can be more easily increased, if necessary, to insert the second connector element into the first.

[0012] In the rotatable connector assembly, the engagement of the retaining section in the groove creates a positive-locking connection between the first and second connector elements with respect to an axially acting force. Overcoming a predetermined minimum axial force releases the positive-locking connection, separating the second connector element from the first and thus disengaging the connected element.

[0013] In the rotatable connector assembly, the groove can be located within the locking teeth. The locking teeth can run perpendicular to the groove, with the locking teeth running axially and the groove circumferentially. The groove can be designed such that a bottom section of the groove is radially at the same level as a bottom section of the spaces between the locking teeth. However, the groove can also be deeper or shallower.

[0014] The locking teeth can be located on either side of the groove when viewed axially (i.e., along an insertion direction). In particular, the locking teeth can also be located on one side of the groove corresponding to an end face of the second connector element. In this case, inserting the first connector element into the second connector element can be facilitated, as the spring lugs can immediately slide axially into the spaces between the locking teeth. This allows for guided connection of the connector assembly.

[0015] In the rotatable connector assembly, the first connector element can include an O-ring that runs ring-shaped around the retaining ring and is designed to press it radially inwards. The O-ring can thus be positioned between the base body of the first connector element and the retaining ring. When the second connector element is inserted, the retaining ring is pressed radially outwards against the O-ring, which deforms elastically and thus exerts an elastic restoring force radially against the retaining ring. This force ensures that the retaining ring can securely engage in the groove of the second connector element.

[0016] In the rotatable connector assembly, the first connector element can be opened axially on the side facing away from the second connector element when connected, allowing the retaining ring and O-ring to be removed axially. This facilitates assembly and / or disassembly of the connector assembly.

[0017] In the rotatable connector assembly, the first connector element can include a flange with screw holes for attaching it to a flat surface. When the first connector element is screwed in, the O-ring and retaining ring are clamped between the flat surface and the first connector element. This securely holds the O-ring and retaining ring in place. These components can be removed by unscrewing the first connector element.

[0018] In the rotatable connector assembly, the first connector element can contain exactly one integral spring element comprising a plurality of spring lugs. The plurality of spring lugs can be, in particular, two, three, or four. If only one integral spring element is provided in the first connector element, assembly and / or disassembly can be significantly simplified compared to a case where multiple spring elements are provided. If the spring element comprises a plurality of spring lugs, no additional pins or locking pins are required, which can simplify manufacturing, assembly, and / or disassembly. In particular, if four spring lugs are provided, two spring lugs can be arranged opposite each other so that their radial forces act in opposite directions.

[0019] The spring element can be provided, for example, as a completely closed corrugated ring. Alternatively, the spring element can be provided as a corrugated ring with an opening. In this case, the spring element can be easily manufactured from a sheet of metal, for example. Unless explicitly stated otherwise, the terms "ring" or "ring-shaped" here generally also refer to a ring that is not closed and therefore has an opening. Of course, a closed ring is also implied unless explicitly excluded.

[0020] In the rotatable connector assembly, the spring tabs of the spring element can be configured to make direct contact with the locking teeth of the second connector element when connected. The spring tabs thus directly touch the locking teeth, eliminating the need for additional pins or locking pins.

[0021] In the rotatable connector assembly, the spring element can be designed as a single, corrugated spring sheet, with the spring lugs formed by bending the spring sheet and thus becoming an integral part of it. A single-piece design of the spring sheet can simplify manufacturing, assembly, and / or disassembly. When the spring lugs are formed by bending the spring sheet, a controlled spring force can be adjusted, and the manufacturing of the spring lugs is straightforward.

[0022] In the rotatable connector assembly, the spring plate can have a constant thickness. Specifically, in this case, the spring plate has the same thickness in the area of ​​the locking lugs as in the other areas of the spring plate. Thickness here refers to the sheet thickness, i.e., the thickness of the spring plate perpendicular to a corrugated surface of the spring plate. If the thickness is constant, the spring plate, including the locking lugs, can be easily manufactured from a sheet of constant thickness. By replacing the spring element with one of a different thickness, particularly one of a different constant thickness, the torque required to rotate the connector elements relative to each other can be easily changed.

[0023] In the rotatable connector assembly, the spring element can be held under preload in a receiving recess of the first connector element. The receiving recess for each of the spring lugs can have a radial opening through which the respective spring lug projects radially inward. The preload ensures that the spring element is securely held in the receiving recess and cannot fall out. The radial opening can include an axially extending slot. The radial opening can be essentially rectangular. If only the locking lugs of the spring plate project inward through their respective openings, secure radial engagement of the second connector element can be ensured, while simultaneously holding the spring plate securely in place.

[0024] The rotatable connector assembly can further include a sealing ring that runs in a ring shape on the inner side of the first connector element and, when connected, creates a seal between the first and second connector elements. Additional sealing rings may be provided. This seal can, in particular, prevent the ingress of liquids into the connector assembly or between the two connector elements, thus ensuring reliable operation.

[0025] In the rotatable connector assembly, the locking teeth of the second connector element can have a substantially trapezoidal cross-section. This can reduce wear on the locking teeth when the second connector element is rotated and / or facilitate rotation.

[0026] In the rotatable connector assembly, the first connector element and the second connector element can be configured such that, in the connected state, the second connector element is at least partially located inside the first connector element, an outer circumferential surface of the second connector element faces an inner circumferential surface of the first connector element, and the spring lugs of the spring element are pressed radially inwards by the spring element against the locking teeth formed on the outer circumference of the second connector element. Brief description of the drawing

[0027] Exemplary embodiments of the invention are described in more detail below with reference to the drawings. Fig. Figure 1 shows a perspective view of a first connector element of a rotatable connector assembly according to the invention. Fig. Figure 2 shows a perspective view of a first connector element of a further rotatable connector assembly according to the invention. Fig. Figure 3 shows a perspective view of a second connector element of a rotatable connector assembly according to the invention. Fig. Figure 4 shows a sectional view of the interaction of the first and second connector elements of a rotatable connector assembly according to the invention in the connected state. Fig. Figure 5 shows a perspective view of a rotatable connector assembly according to the invention in the connected state. Detailed description of the embodiments

[0028] In the following, spatial relationships, such as above, below, inside, outside, etc., are used to illustrate the embodiments. Those skilled in the art understand that this serves for illustrative purposes and is not to be understood as a limitation.

[0029] Fig. Figure 1 shows a perspective view of a first connector element 2 of a rotatable connector assembly according to the invention. Fig. Figure 2 also shows a perspective view of a first connector element 2 of a rotatable connector assembly according to the invention. Fig. 1 and Fig. 2 can either be considered as different embodiments of the connector assemblies according to the invention. In this case, the embodiment of the Fig. 1. One in which the first connector element has no retaining ring and no sealing ring. The first connector element 1 of the exemplary embodiment of Fig. However, part 2 has a retaining ring 20 and a sealing ring 22. In an alternative view, the Fig. 1 a state of the first plug element 2 the Fig. 2 shows, in which the retaining ring 20 and the sealing ring 22 are not yet mounted.

[0030] Fig. Figure 3 shows a perspective view of a second connector element 4 of a rotatable connector assembly according to the invention. The second connector element 4 is suitable for axial insertion (defined here and according to the figures as the z-direction) into a substantially cylindrical opening of the first connector element 2 according to Fig. 2 to be introduced in order to form a connected state, which is used, for example, in the Fig. 4 and Fig. 5 is shown. The second connector element 4 of the Fig. Figure 3 forms a housing part of an angled connector of the connector assembly. Further elements of the angled connector are assumed to be known and are not shown in the figures for the sake of clarity, nor are they described herein.

[0031] The Fig. 4 and Fig. Figure 5 shows different views of the first connector element 2 of the Fig. 2 and the second plug element 4 of the Fig. 3 formed connector assembly 1 in the connected state. The Fig. 4 and Fig. Figure 5 thus shows a rotatable connector assembly 1 with the first connector element 2 and the second connector element 4. The second connector element 4 has a substantially circular hollow cylindrical section 24 (see Fig. 3), which defines a radial direction and an axial direction. According to the figures, the axial direction is defined as the z-direction. In the connected state according to the Fig. 4 and Fig. 5 is the second plug element 4 arranged in the first plug element 2.

[0032] The second connector element 4 essentially comprises trapezoidal locking teeth 10 in cross-section, which in the connected state face the first connector element 2 and extend axially along the outer circumference of the essentially circular hollow cylindrical section 24 of the second connector element 4.

[0033] The first connector element 2 comprises four spring lugs 6, which are an integral part of a spring element 14. The spring element 14 is designed as a single piece of corrugated spring steel. The spring lugs 6 are formed by bending the spring steel and are thus an integral part of the spring steel. The spring element 14 is arranged in a receiving recess 16 of the first connector element 2, where it is held independently by its preload. The receiving recess 16 extends essentially circumferentially around the circular cylindrical opening of the first connector element 2. Openings are provided at the positions of the spring lugs 6, extending from the receiving recess 16, through which the spring lugs 6 project radially towards a central axis of the circular cylindrical opening of the first connector element 2. The openings are provided in a frame element 12 of the first connector element 2.The spring element 14 is pre-tensioned such that it presses the locking lugs 6 radially against the second connector element 4. The locking lugs 6 can each be elastically deformed independently of one another by a radially acting force.

[0034] The number of spring lugs 6 is not limited to four and can be freely selected as required, with at least two spring lugs 6 being advantageous. Furthermore, the spring element 14 need not be formed in one piece. For example, two one-piece spring elements 14, each with two spring lugs 6, can be provided and located in a corresponding receiving recess 16.

[0035] The first connector element 2 is part of a (not shown) generator-side connector section that can be connected to a generator, and the second connector element 4 is part of a (not shown) output connector section. The generator-side connector section and the output connector section form the angled connector housing.

[0036] When the second connector element 4 is rotated relative to the first connector element 2, the inclined side surfaces of the essentially trapezoidal locking teeth 10 push the respective spring lug 6 radially outwards, generating a counterforce that acts against the locking tooth 10. This creates the torque required to rotate and disengage the first connector element 2. The force or torque can be determined, for example, by selecting a material for the spring element 14 and / or by selecting a thickness of the spring element 14 (i.e., material thickness), and can be changed, if necessary, by replacing the spring element 14.

[0037] The detent process is low-wear, as no plastic deformation occurs. The spring element 14 elastically absorbs the radial movement and any deformation of the spring nose 6, without any plastic deformation of the first connector element 2, the second connector element 4, or the locking teeth 10.

[0038] As the second connector element 4 is rotated further, so that the radially outer surface of the substantially trapezoidal detent tooth 10 facing the first connector element 2 contacts the spring lug 6, the spring lug 6 is in a position of large radial displacement, and the spring element 14 reaches a state of higher spring tension. As the second connector element 4 is rotated further, the spring element 14, due to its spring tension, forces the spring lug 6 into a substantially trapezoidal groove (i.e., into a gap) between two detent teeth 10. This achieves reliable detent engagement. Backlash-free detent engagement can be achieved if the spring lug 6, in its detent position, contacts the inclined side faces of two substantially trapezoidal detent teeth 10.

[0039] In the detent position of the connector assembly 1, all spring lugs 6 are in a detent position between two detent teeth 10, thus achieving a secure clamping. The torque required to rotate the second connector element 4 relative to the first connector element 2 generates a force on the detent teeth 10 via the spring lugs 6, disengaging the spring lugs 6. Since all spring lugs 6 are moved from their detent position during disengagement, the disengagement force exerted by a spring lug 6 on the respective detent tooth 10 is relatively low for a given torque required for rotation, as the disengagement force resulting from the torque is distributed across multiple spring lugs 6 and multiple detent teeth 10. This reduces wear. The detent teeth 10 and the spring lugs 6 extend axially, thus providing a larger contact area, which reduces wear.A larger contact area is created between them. The locking teeth 10 do not necessarily have to extend axially; they can also extend parallel to each other and obliquely to the axial direction.

[0040] The person skilled in the art recognizes that the essentially trapezoidal profile of the locking teeth 10 can be rounded to further minimize wear. Furthermore, the radially outer surface of the essentially trapezoidal locking tooth 10 can be reduced, resulting in a nearly triangular profile of the locking tooth 10, thereby reducing the distance between the locking positions. This configuration of the locking tooth 10 is considered equivalent. The essentially trapezoidal locking teeth 10 ensure that the connector assembly 1 is insensitive to manufacturing tolerances.

[0041] Friction, and therefore torque, can be reduced by a suitable surface coating of the detent teeth 10, the spring lugs 6 and / or the spring elements 14. Lubrication can also be provided.

[0042] The rotatable connector assembly 1 according to the invention has been described such that the second connector element 4 is located inside the first connector element 2 and the locking teeth 10 are directed radially outwards. However, those skilled in the art will recognize that such a rotatable connector assembly 1 can also be constructed in reverse.

[0043] In addition to the radial locking mechanism described above, connector assembly 1 of the Fig. 2, Fig. 3, Fig. 4 to Fig. 5. Additionally, the second connector element 4 has an axial locking mechanism relative to the first connector element 2. For this purpose, the first connector element 2 has a retaining ring 20. The retaining ring 20 of the first connector element 2 is designed to engage in a groove 26 of the second connector element 4 when connected. The retaining ring 20 of the illustrated embodiment has an opening or interruption, which allows or facilitates a change in the radius of the retaining ring 20. A radially inward force is exerted on the retaining ring 20 by an O-ring 28 of the first connector element 2, which is described below. This force must be overcome when the second connector element 4 is inserted until the retaining ring 20 can lock into the groove 26. During this process, the inner radius of the retaining ring 20 is temporarily increased.

[0044] As in Fig. As shown in Figure 4, the retaining ring has an annular retaining section 30 that extends radially inwards. The retaining section 30 is the portion of the retaining ring 20 that, in the connected state, is located within the groove 26. As shown in Fig. As shown in Figure 4, the retaining ring 20 can have a substantially L-shaped cross-section. The retaining section 30 accordingly has a substantially rectangular cross-section with rounded corners.

[0045] The engagement of the retaining section 30 in the groove 26 creates a positive-locking connection between the first connector element 2 and the second connector element 4 with respect to an axially acting force. By overcoming a predetermined minimum axial force, the positive-locking connection can be released, the second connector element 4 separated from the first connector element 2, and thus the connected state can be broken.

[0046] An O-ring 28 is provided to exert a radial force on the retaining ring 20 and to hold the retaining ring 20. The O-ring 28 is located between a base body of the first connector element 2 and the retaining ring 20.

[0047] The first connector element 2 is open axially on a side facing away from the second connector element 4 when connected, such that the retaining ring 20 and the O-ring 28 can be removed axially. This facilitates the assembly and / or disassembly of the connector assembly 1.

[0048] The first connector element 2 comprises a flange 32 with screw holes for attaching the first connector element 2 to a flat surface, such that when the first connector element 2 is screwed in, the O-ring 28 and the retaining ring 20 are clamped between the flat surface and the first connector element 2. This securely holds the O-ring 28 and the retaining ring 20 in place when the first connector element 2 is attached. These components can be removed by unscrewing the first connector element 2.

[0049] The rotatable connector assembly 1 includes a sealing ring 22, which runs annularly along the inner side of the first connector element 2 and, in the connected state, provides a seal between the first connector element 2 and the second connector element 4. Additional sealing rings may be provided. The seal can, in particular, prevent the ingress of liquids into the connector assembly 1 or between the two connector elements 2 and 4, thus ensuring safe operation.

Claims

[1] Rotatable connector assembly (1), with - a first plug element (2) and - a second plug element (4) comprising a substantially circular hollow cylindrical section (24), - wherein the first connector element (2) and the second connector element (4) can be arranged at least partially within each other in a connected state, and can be rotated relative to each other in the connected state, - the essentially circular hollow cylindrical section (24) of the second connector element (4) has locking teeth (10) on its circumference which, in the connected state, face the first connector element (2), and - in the first connector element (2) at least one spring element (14) is provided which comprises a plurality of spring lugs (6) which are each designed to engage between two adjacent locking teeth (10) of the second connector element (4) when connected, characterized by, that the second connector element (4) comprises a retaining ring (20) which includes an annularly extending and radially inwardly pointing retaining section (30) which, in the connected state, engages in a groove (26) provided on an outside of the circular hollow cylindrical section (24) of the second connector element. [2] Rotatable connector assembly (1) according to claim 1, wherein the first connector element (2) and the second connector element (4) are designed such that in the connected state a positive locking connection of the first connector element (2) and the second connector element (4) is ensured with respect to an axially acting force. [3] Rotatable connector assembly (1) according to claim 1, wherein the engagement of the retaining section (30) in the groove (26) causes a positive locking connection of the first connector element (2) and the second connector element (4) with respect to an axially acting force. [4] Rotatable connector assembly (1) according to one of claims 1 to 3, wherein the groove (26) is provided within the locking teeth (10). [5] Rotatable connector assembly (1) according to any one of claims 1 to 4, wherein the first connector element (2) comprises an O-ring (28) which extends in a ring shape around the retaining ring (20) and is designed to press the retaining ring radially inwards. [6] Rotatable connector assembly (1) according to claim 5, wherein the first connector element (2) is opened in the axial direction on a side facing away from the second connector element (4) in the connected state so that the retaining ring (20) and the O-ring (28) can be removed in the axial direction. [7] Rotatable connector assembly (1) according to claim 6, wherein the first connector element (2) comprises a flange (32) with screw openings for screwing the first connector element (2) onto a flat surface, such that in a screwed-on state of the first connector element (2) the O-ring (28) and the retaining ring (20) are clamped between the flat surface and the first connector element (2). [8] Rotatable connector assembly (1) according to one of claims 1 to 7, wherein in the first connector element (2) exactly one integrally formed spring element (14) is provided which comprises the plurality of spring lugs (6), wherein the plurality of spring lugs (6) is in particular 2, 3 or 4 spring lugs. [9] Rotatable connector assembly (1) according to any one of claims 1 to 8, wherein the spring lugs (6) of the spring element (14) are arranged to be in direct contact with the locking teeth (10) of the second connector element (4) when connected. [10] Rotatable connector assembly (1) according to any one of claims 1 to 9, wherein the spring element (14) is formed as a one-piece corrugated spring sheet, in particular of constant thickness, and the spring lugs (6) are formed by bending the spring sheet and are thus part of the spring sheet. [11] Rotatable connector assembly (1) according to any one of claims 1 to 10, wherein the spring element (14) is received under preload in a receiving recess (16) of the first connector element (2) and wherein the receiving recess (16) has a radial opening for each of the spring lugs (6) through which the respective spring lug (6) projects radially inwards. [12] Rotatable connector assembly (1) according to any one of claims 1 to 11, further comprising a sealing ring (22) which runs in an annular shape on an inside of the first connector element (2) and which, in the connected state, provides a seal between the first connector element (2) and the second connector element (4). [13] Rotatable connector assembly (1) according to any one of claims 1 to 12, wherein the locking teeth (10) of the second connector element (4) have a substantially trapezoidal cross-section. [14] Rotatable connector assembly (1) according to any one of claims 1 to 13, wherein the first connector element (2) and the second connector element (4) are configured such that, in the connected state, the second connector element (4) is at least partially located in the first connector element (2), an outer circumferential surface of the second connector element (4) faces an inner circumferential surface of the first connector element (2), and the spring lugs (6) of the spring element (14) are pressed radially inwards by the spring element (14) against the locking teeth (10) formed on the outer circumference of the second connector element (4).

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