POWER TRANSMISSION ARRANGEMENT AND INSERT

Description

[0001] The invention relates to an insert according to the preamble of claim 1 and a force transmission arrangement into which such an insert is inserted.

[0002] Particularly in the automotive and aerospace industries, there has been a demand for several years to replace conventional steel or aluminum components with lightweight parts, thereby reducing the overall weight of the vehicle / aircraft or other machine structures. Carbon fiber reinforced plastic (CFRP) sandwich components are frequently used for this purpose. These components feature a lightweight core, for example, made of a foamed material or a honeycomb structure, which is faced on both sides with CFRP or other rigid material face sheets. The core creates a distance between the two face sheets and the component's neutral axis, resulting in higher bending stiffness. A challenge lies in the mechanical coupling of these lightweight components to adjacent parts to transfer the applied forces into the sandwich structure.This introduction of forces into the CFRP sandwich structure, as described, for example, in US 8,777,193 B2, is achieved via an insert that is placed into the sandwich structure and to which a fastener for mechanical coupling to the connecting component is assigned. The reason for using such an insert lies in the heterogeneity of the composite material. The fibers, which are crucial for the strength and stiffness of the component, can only be used in combination with the respective matrix material, for example, epoxy resin. This matrix material itself is significantly less stiff and strong than the fibers. The insert ensures that the forces are introduced into the composite material, so that this interface does not represent a weak point. Force introduction is typically considered from the perspective of strength.There are numerous proposals for designing such force-transmitting inserts to achieve the highest possible strength, which plays a crucial role in many CFRP applications, such as in aircraft and vehicle construction or sporting goods. Stiffness is another requirement, but of secondary importance.

[0003] When optimizing the strength of a sandwich structure, the focus is on the maximum achievable stress, above which fracture occurs, typically a brittle fracture at the point of highest stress. A strength-optimized design, therefore, uses the stress-strain diagram of the respective material / component to determine the maximum achievable stress and the associated strain. A stiffness-optimized design focuses on a maximum modulus of elasticity, which in the stress-strain diagram corresponds to the slope of the tangent at the zero point of the stress distribution. The force application should be such that both stiffness and strength are ensured within a predetermined range.

[0004] The core material, selected for its lightweight construction, can be readily adapted to the specific shape requirements, either through manual shaping or relatively cost-effective milling. Numerous solutions exist for this core material and its processing. A common feature of all these methods is that the core material thickness is subject to a certain degree of uncertainty, ranging from 0.1 mm to several millimeters. When applying the aforementioned force to a sandwich structure, this thickness tolerance of the core, and consequently of the entire sandwich assembly, must be taken into account.

[0005] Another characteristic of core materials is that they are not designed to withstand high point forces, as the cover layers distribute the forces for the core over larger areas or volumes.

[0006] A fastening element for sandwich structures is known from DE 17 50 818 A. The fastening element, consisting of a blind rivet nut with an internal and an external thread, and a plastic screw with an internal thread that engages with the external thread of the blind rivet nut, is inserted into the sandwich structure. Both the plastic screw and the blind rivet nut have flange-like surfaces that bear against the outer layers of the sandwich structure to distribute the forces of an applied load over larger areas or volumes of the core. A further screw, which has a hook for receiving the load, is inserted into the internal thread of the blind rivet nut.

[0007] US Patent 2006 / 0182513A1 discloses a fastening device for furniture assembly, consisting of a receiving nut and a reducing screw, wherein the reducing screw has a through-hole with an internal thread. This internal thread accepts a screw inserted from the side of the receiving nut, which secures a component adjacent to the fastening device.

[0008] US patent 6 736 577 B2 describes a cylindrical receptacle in the form of a sleeve for a dowel pin for the quick mounting and dismounting of a baby travel cot on partition walls in passenger aircraft.

[0009] WO 82 / 02821 A1 shows a bearing arrangement for a storage compartment, wherein an axle bolt connects a storage compartment and an arm to each other via this bearing arrangement.

[0010] The printed document DE 2 81 30 98 A1 describes a two-part insert mounted on a plate, with bushing sections that can be moved relative to each other and are fixed in position relative to each other and with reference to the plate by means of a potting compound.

[0011] Document US 5 09 39 57 A shows a sandwich construction with an insert. Its bushing sections are also connected so that they can slide against each other and are fixed in position relative to each other and to the sandwich construction by means of a potting compound.

[0012] Document US 6 48 84 60 B1 shows a sandwich structure with an insert whose bushing sections are screwed together to a stop. Thus, the distance between the flanges of the bushing sections that are in contact with the surfaces of the sandwich structure is defined.

[0013] Document US 4 98 17 35 A describes a sandwich structure with an insert whose bushing sections are screwed together. The axial position of the bushing sections relative to each other is fixed by bonding flanges of the bushing sections to the surfaces of the sandwich structure.

[0014] A classic method of transferring forces from a rotating or cylindrical component, such as a shaft or tube, into a sandwich structure is via a flange that connects to the shaft / tube on one side and to the lightweight component on the other. This connection is typically made so that the flange joins both outer layers. A disadvantage of this type of flange is that it must be specifically designed for the thickness of the sandwich and the diameter of the interface. This results in a wide variety of sizes and designs, each tailored to the specific situation, which entails a correspondingly high level of tooling and cost complexity.

[0015] In the solution known from the aforementioned US 8,777,193 B2, the insert has two flange bushings, each comprising a support flange and a bushing section. The support flanges rest against the face sheets on both sides, and the two bushing sections are inserted into a recess in the sandwich structure and bonded in place. The connecting component or the fastener for coupling the connecting component is then appropriately attached to these flange bushings. This design also exhibits the aforementioned disadvantages, as the respective flange bushings must be individually adapted to the existing thickness of the sandwich structure, and there is also little scope for varying the fasteners for attaching the connecting components.

[0016] In contrast, the invention is based on the objective of creating an insert and a force transmission arrangement that enable optimized force application / transmission with minimal equipment effort.

[0017] This problem is solved with regard to the insert by the combination of features of claim 1 and with regard to the force transmission arrangement by the features of dependent claim 3.

[0018] Advantageous further developments of the invention are the subject of the dependent claims.

[0019] The insert according to the invention accordingly has two flange bushings, which are penetrated by a fastening element and are adjustably connected to each other. The insert is preferably designed with a device for clamping the connection of the two flange bushings. In the insert according to the invention, a hub-shaped contact projection is formed on one of the flange bushings, against the end face of which a radial strut, which is a section of the connecting component and which fastens the insert to a flange attached to a separate component, rests flat.

[0020] Further details of the insert are designed according to the following description of the power transmission arrangement and can be added at any time as subclaims.

[0021] The power transmission arrangement according to the invention has a sandwich structure with a lightweight core and rigid outer layers, into which at least one insert is inserted, via which a force-fit connection to a connecting component is achieved. Each insert has two flange bushings which bear against the outer layers on both sides with support flanges and are inserted into the core with bushing sections. Furthermore, a fastening element is provided, which is held on at least one of the flange bushings and which supports the connecting component. The flange bushings are adjustably connected to one another.

[0022] Such a design allows the flange bushings to be individually adjusted with regard to the wall thickness and geometry of the sandwich structure and then fixed in a suitable manner, so that one insert can be used for a variety of different applications.

[0023] The adjustability also makes it possible to readjust the insert during use, for example in the event of a certain amount of wear or a change in the geometry of the sandwich structure or the connecting component; however, bonding is preferably avoided or removed.

[0024] The power transmission is further optimized according to the invention, since the insert is tensioned after assembly.

[0025] In one possible embodiment, the bushing sections are threaded together. The thread is preferably a fine thread, allowing the relative position of the flange bushings to be precisely adjusted to the respective thickness of the sandwich structure. A fine thread is defined as a thread with a smaller pitch than a conventional metric thread.

[0026] In one embodiment of the invention, a threaded spindle or threaded rod is formed on one bushing section, which can be brought into thread engagement with an internal thread of the other bushing section.

[0027] The power transmission is further optimized when the flange bushings of the insert are clamped together after assembly.

[0028] Such tensioning can be achieved, for example, via the fastening device or an additional clamping screw, which clamps the two flange bushings together.

[0029] This tensioning ensures that, apart from external loads / forces, no or only minor forces are introduced into the sandwich.

[0030] As explained earlier, manufacturing a sandwich structure with tight tolerances is relatively difficult, so it can happen that the sandwich geometry differs slightly from the geometry of the connecting component. In this case, it can be advantageous to make the connection of the fastener to the connecting component flexible in order to compensate for these deviations in shape. This can be achieved, for example, using elastic bearings or similar devices.

[0031] The insert can be fitted into the sandwich structure. Alternatively, the insert, especially its flange bushings, can also be bonded to the sandwich structure after adjustment and clamping.

[0032] To compensate for the geometric deviations described above, the fit or bonding can be selected to allow a certain degree of compliance and thus a certain tolerance compensation. This helps to reduce stress peaks acting on the individual inserts.

[0033] When large forces are introduced, a large number of inserts are preferably arranged in a sandwich structure. The connecting component then has a corresponding hole pattern for connection with the inserts.

[0034] In one embodiment of the invention, at least one support flange of the insert has a hub-shaped contact projection for the connecting component on the connection side.

[0035] To optimize strength and weight, the support flange can be tapered towards its circumference. Additionally or alternatively, the support flange can have a bearing surface with a circular or oval outer circumference. The bearing surface can also be designed, for example, as a circular segment, with a section omitted to reduce the diameter inwards or outwards. It can also be advantageous if one side is circular and the other side has a different shape. This allows, for example, the flange on one side of the coupling assembly to be larger without colliding. It is sufficient to be able to tighten on the side with the circular surfaces; on the other side, the bearing surface can be freely selected and optimized.

[0036] To ensure an optimal bonding surface, grooves or raised areas can be provided on the contact surface of the support flange.

[0037] The applicant reserves the right to make further aspects the subject of dependent or independent claims.

[0038] It is therefore preferred if the insert is designed with stiffness in mind. Preferably, stainless steel is used to ensure a flawless and durable bond and to distribute the forces as evenly as possible across the entire bonded area. For the connecting structure (connecting component), another material, for example aluminum, can also be used. This freedom of choice reveals a further advantage of the solution according to the invention. With a direct connection of the sandwich structure to a flange, the same material must be used for the force transmission and the connecting structure, typically aluminum or steel. However, with aluminum, the stiffness and fatigue strength are unsatisfactory, and with steel, the high density limits the possibilities for lightweight construction. This disadvantage does not exist with the solution described above, since the material of the insert and the connecting component, respectively, is the same.The connection design can be individually selected according to the specific task.

[0039] The inserts according to the invention are preferably designed and manufactured as cost-effective turned parts.

[0040] The force application can be scaled by varying the number of inserts.

[0041] As mentioned above, the connection of the inserts to the connecting structure may, under certain circumstances, involve targeted compliance in one or more degrees of freedom in order to prevent / minimize stress concentrations in the individual inserts as a result of mechanical or assembly-related defects.

[0042] Another advantage of the design according to the invention is that the design of the connection structure is standardized and simplified, and the costs for development and implementation are correspondingly lower.

[0043] Advantageous embodiments of the invention are explained in more detail below with reference to schematic drawings. These show: Figure 1 an embodiment of a power transmission arrangement according to the invention; Figure 2 a sandwich structure of the power transmission arrangement according to Figure 1 with inserted inserts; Figures 3, 4 Views of an insert of the power transmission arrangement according to the Figures 1 and 2 and Figures 5, 6 Variants of the geometric design of the insert according to the Figures 3 and 4 .

[0044] One in Figure 1 The force transmission arrangement 1 shown serves to introduce / transmit force between an approximately cylindrical component, for example a shaft or a tube (not shown) via a connecting component group 2, in this case a flange on a sandwich structure 4, wherein the force transmission from or into the sandwich structure 4 takes place via a plurality of inserts 6. Figure 2shows a single representation of the sandwich structure 4 with the inserts 6.

[0045] The sandwich structure 4, for example, consists of a CFRP sandwich with a foamed core 8 and two CFRP face sheets 10, 12. As explained, a honeycomb structure can also be used instead of the foamed core 8. Naturally, the sandwich structure can also be made with additional layers. The inserts 6, which will be explained in more detail below, penetrate the layered structure and are located on both sides of the two face sheets 10, 12. Fasteners, in this case a fastening screw 14, are assigned to each insert. These fasteners serve two purposes: firstly, they clamp the insert 6, and secondly, they force-fit the connecting component group 2 to the insert 6 and thus to the sandwich structure 4.

[0046] In the illustrated embodiment, the connecting component group 2 has a plurality of radial struts 16, which are connected on one side to the respective insert 6 and on the other side to a flange 18, which in turn is fixed to the associated component, for example, the shaft or the tube. In the exemplary embodiment shown, the radial struts 16 are screwed to the flange 18 along a widened base by means of two screws 20 each. An opening is formed in an end section that tapers relative to this base, through which the fastening screw 14 passes. A clamping nut 22 or the like is then attached to the end section of the fastening screw 14. A screw head 24 of the fastening screw 14 rests against a rear flange shoulder 26 or a correspondingly shaped radial strut (not shown).In the illustrated embodiment, this flange shoulder extends between the screw head 24 and the adjacent end section of the insert.

[0047] Figure 3 shows a single representation of an insert 6 according to the Figures 1 and 2 . In Figure 4 This insert 6 is shown in longitudinal section. Accordingly, the insert 6 has two flange bushings 28, 30 which are threaded together. The in Figure 3 The flange bushing 28 shown on the right has a radially projecting support flange 32, which is connected to its Figure 3 The annular support surface 34, facing the viewer, is designed with concentric projections 36, which – as explained in more detail below – enable a uniform application of adhesive. The flange bushing 28 has a bushing section 38 at its end section facing the other flange bushing 30, on which an internal thread 40 (see Figure 4). The axial length of this bushing section 38 is significantly less than the thickness of the sandwich structure. On the connection side, a hub-shaped contact projection 42 is formed on the flange bushing 28, against whose end face 43 the previously described radial strut 16 bears flat.

[0048] The flange bushing 30 also has a support flange 44 designed according to the above specifications, on whose annular support surface 46 the projections 48 are also formed. The outer contour 50 of the support flange 44, facing the viewer, is approximately pyramidal and ends at a flattened section 52, which in the Figure 1 In the illustrated embodiment, the flange shoulder 26 rests flat against the flange shoulder or (not shown) against the screw head 24 or another connecting component.

[0049] Towards the flange bushing 28, a bushing section 54 is formed on the flange bushing 30, the axial length of which is significantly shorter than that of the bushing section 38 and which carries a threaded rod 56 that can be screwed into the internal thread of the bushing section 38. The thread is designed as a fine thread, which has a smaller thread pitch than conventional metric threads. As shown in particular in the section in Figure 4 Removable, the flange bushings 28, 30 are each penetrated by a longitudinal bore 58, 60, which in turn is penetrated by the fastening screw 14 or another fastening means during assembly.

[0050] By adjusting the threaded rod 56, the support width S of the insert 6, or more precisely the distance between the support surfaces 34, 46, can be adjusted according to the thickness of the sandwich structure.

[0051] Furthermore Figure 4As can be seen, the diameters D of the two bushing sections 38 and 54 are approximately equal. The axial length of the threaded rod 56, and correspondingly the axial length of the internal thread 40, are selected to allow for easy adaptation to different sandwich thicknesses. The minimum support distance S is determined by the end-face contact of the two bushing sections 38 and 54, which then merge flush into one another. The diameter D of the bushing section is matched to the diameter B of a bore 61 in the sandwich structure 4, so that the forces are transferred into the fibers of the face sheets by means of a fit or a thin adhesive bond.

[0052] In the illustrated embodiment, the circumference of the two support flanges 32, 44 is approximately the same diameter and circular, so that the same force application surfaces are formed on both sides, independent of the rotational position of the flange bushings 28, 30.

[0053] As well as the Figure 4 Since it is removable, both support flanges 32, 44 taper towards their outer circumference, resulting in an approximately trapezoidal flange cross-section in cross-section.

[0054] During the assembly of the in Figure 1 The connection assembly 2 shown is initially arranged according to Figure 2The inserts 6 are inserted into the sandwich structure 4, with the threaded rod 56 being screwed into the internal thread 40 until the support surfaces 34, 46 come into contact with the outer facing layers 10, 12. However, no tension is applied via the fine thread to prevent point loads from being introduced into the sandwich structure. The support surfaces 34 are selected such that the forces can be distributed over a large area.

[0055] In one embodiment, the support surfaces 34, 46 are provided with an adhesive layer during assembly, the minimum thickness of which is determined by the protrusions 36, 48. In this case, the insert 6 is bonded to the cover layers 10, 12. Alternatively or additionally, the bonding can also take place along the bushing sections 38, 54, resulting in a bond within the core 8. Bonding to the cover layers 10, 12 is advantageous because the force is then transmitted directly into the (cut) fibers of the cover layers 10, 12.

[0056] In principle, however, it is also possible to accommodate the inserts 6 in the bore 61 using only a suitable press fit or clearance fit, whereby this fit is particularly important in the area of ​​the cover layers 10, 12 in order to be able to introduce the forces.

[0057] It can be advantageous to incorporate a certain degree of play or flexibility in the adhesive bond or the fit to compensate for dimensional deviations in the layer structure relative to the connecting components. Additionally or alternatively, it may also be possible to provide such flexibility and compliance in the area of ​​the connecting components.

[0058] In the illustrated embodiment, the inserts 6 lie on a pitch circle that corresponds to the pitch circle of the hole pattern of the connecting component group 2, in this case the flange 18 and / or its radial struts 16.

[0059] The sandwich structure 4 with the inserts 6 is then used in the Figure 1In the illustrated embodiment, the insert 6 is pushed axially onto the flange 18 until the flat surface 52 comes into contact with the flange shoulder 26. The fastening screws 14 are then inserted, bearing against the radial shoulder 26 as described above and passing through the radial struts 16, which, in the illustrated embodiment, are mounted on the flange 18 after the sandwich structure 4 has been attached. A clamping nut 22 is then placed on the projecting end section of each fastening screw 14. This nut serves to clamp the respective insert 6 and to create a force-fit connection to the respective radial struts 16 and the flange 18.

[0060] Since the two flange bushings 28, 30 are threaded together, no force is applied to the sandwich structure by this tension of the inserts 6. This is important because otherwise, especially in the edge region, there would be a risk of the core yielding elastically and / or plastically – a disadvantage of conventional solutions.

[0061] As mentioned at the outset, the inserts 6 and the fastening screws 14 are preferably made of stainless steel to ensure a reliable and durable bond. The other connection components, such as the flange 18 and / or the radial struts 16, may be made of a different, weight-optimized material, for example, an aluminum alloy or another lightweight metal.

[0062] Of course, the use of high-strength composite material is also possible.

[0063] The inserts 6 can be easily manufactured as turned parts, thus ensuring a cost-effective solution.

[0064] As explained above, in the illustrated embodiment, tensioning is achieved by means of the fastening screw 14. However, in principle, this tensioning can also be achieved using a clamping screw, which, for example, engages from one of the bushing sections 38, 54 into the other bushing section to clamp them together. In this case, a continuous fastening screw 14 can be omitted, so that the connecting components can then be connected to the support flanges 32, 44 via other fasteners.

[0065] As explained above, in the embodiments described above, the circumferential surfaces of the support flanges 32, 44 are circular. Such a design is Figure 5As indicated above. However, in deviation from this circular structure, it is also possible, as shown in Figure 5 As shown below, the support flanges 32, 44 are designed to be elliptical or otherwise deviating from the circular base. It is preferred that the support flanges 32 are designed such that the respective support surfaces are of the same size. As shown in Figure 5 As indicated by dashed lines, a circular segment-shaped support surface can also be used. The geometries of the support surfaces 34, 46 of the two support flanges 32, 44 can also be chosen differently.

[0066] As further explained, in the previously described embodiment, the support flanges 32, 44 are reduced towards their outer circumference - such a variant is in Figure 6 arranged at the bottom. Naturally, this tapering can be relatively acute-angled, as in Figure 6 as shown below, or at a relatively obtuse angle, as in Figure 4 as shown, executed. Alternatively, a constant wall thickness of the support flange 32, 44 can be chosen, as is the case, for example, in Figure 6 shown above.

[0067] A power transmission arrangement and an insert for such a power transmission arrangement are disclosed, the insert having two flange bushings that are adjustable to each other and clamped to each other. Reference symbol list:

[0068] 1 Power transmission arrangement 2 Connection component group 4 Sandwich construction 6 Insert 8 Core 10 Cover layer 12 Cover layer 14 Fastening screw 16 Radial strut 18 Flange 20 Screw 22 Clamping nut 24 Screw head 26 Flange shoulder 28 Flange bushing 30 Flange bushing 32 Support flange 34 Support surface 36 Raise 38 Bushing section 40 Internal thread 42 Mounting projection 43 End face 44 Support flange 46 Support surface 48 Raise 50 Outer contour 52 Flattened 54 Bushing section 56 Threaded rod 58 Longitudinal bore 60 Longitudinal bore 61 Bore

Claims

1. An insert (6) for a force transmission assembly (1) with a sandwich configuration (4) comprising a comparatively light core (8) and two rigid cover layers (10, 12), wherein the insert (6) can be inserted into the sandwich configuration (4), wherein a force-fit connection to a force-applied connecting part can be established via the insert (6), with two flange bushings (28, 30) that can be fastened to both sides of the cover layers (10, 12) with support flanges (32, 44) and can be inserted into the core (8) with bushing sections (38, 54) and to which a fastening means (14) for fastening to the connecting part can be assigned, wherein the flange bushings (28, 30) are connected to each other in an adjustable manner, wherein the bushing sections (38, 54) are in threaded engagement, wherein the insert (6) is braceable, characterized in that a hub-shaped abutment projection (42) is formed on one of the flange bushings (28), wherein on an end face (43) of the abutment projection (42) a radial bracing (16), which is a section of the connecting part and fastens the insert (6) with a flange (18) fastened to a separate fastening element, can abut in a plane manner.

2. The insert (6) according to claim 2, with a device for bracing the two flange bushings (28, 30).

3. A force transmission assembly (1) with a sandwich structure (4) comprising a comparatively light core (8) and two rigid cover layers (10, 12) into which at least one insert (6) according to claim 1 or 2 is inserted, via which a force-fit connection to a force-applied connecting part is established, wherein each insert (6) has two flange bushings (28, 30) which are supported on both sides on the cover layers (10, 12) at support flanges (32, 44) and are inserted into the core (8) with bushing sections (38, 54) and to which a fastening means (14) for fastening to the connecting part is assigned, wherein the flange bushings (28, 30) are connected to each other in an adjustable manner, wherein the bushing sections (38, 54) are in threaded engagement, characterized in that the insert (6) is braced and wherein a hub-shaped abutment projection (42) is formed on one of the flange bushings (28), wherein on the end face (43) of the abutment projection (42) a radial bracing (16), which is a section of the connecting part and fastens the insert (6) to a flange (18) fastened to a separate fastening element, abuts in a plane manner.

4. The force transmission assembly (1) according to claim 3, wherein a threaded rod (56) is formed on one bushing section (54), which is associated with an internal thread (40) of the other bushing section (38).

5. The force transmission arrangement (1) according to claim 3 or 4, wherein the bracing is applied via the fastening means (14) or an additional tensioning screw.

6. The force transmission arrangement (1) according to one of the preceding claims, wherein the connection of the fastening means (14) to the connecting part is designed to be flexible in order to compensate for shape deviations of the sandwich configuration (4).

7. The force transmission arrangement (1) according to one of the preceding claims, wherein the insert (6) is received with a fitting in the sandwich configuration (4).

8. The force transmission arrangement (1) according to one of claims 3 to 5, wherein the flange bushings (38, 54) are adhered to the sandwich configuration (4) after the insert (6) has been adjusted.

9. The force transmission assembly (1) according to claim 7 or 8, wherein the fitting or the adhesion is selected such that a certain degree of flexibility is permissible.

10. The force transmission assembly (1) according to one of the preceding claims, wherein a plurality of inserts (6) is arranged in the sandwich configuration (4) and the connecting part has a corresponding hole pattern for connecting to the inserts (6).

11. The force transmission assembly (1) according to one of the preceding claims, wherein at least one support flange (32, 44) is tapered toward its periphery and / or the support flange (32, 44) has a support surface (34, 46) with a circular or non-circular outer periphery, for example a circular surface segment or an oval shape, wherein the support surface (34, 46) of one support flange (32, 44) may have a different geometry than the support surface (34, 46) of the other support flange (32, 44).

12. The force transmission assembly (1) according to one of the preceding claims, wherein grooves or protrusions (36) are formed on a support surface (34, 46) of the support flange (32, 44).