Spring element for a snap connection in a housing of a field device, and snap connection
Patent Information
- Application Number
- PCT/EP2026/058168
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-04-15
- Filing Date
- 2026-03-23
- Publication Date
- 2026-10-22
Smart Images
Figure EP2026058168_22102026_PF_FP_ABST
Abstract
Description
[0001] Spring element for a snap connection in a housing of a field device and snap connection
[0002] The invention relates to a spring element for a snap connection in a housing of a field device and to a snap connection.
[0003] Field device enclosures are used to house electronic measuring and operating circuits. Because these electronic circuits are particularly sensitive and critical components of field devices, the enclosures must meet exceptionally high standards. Furthermore, the enclosures must be able to withstand harsh environments, such as those with very high or very low temperatures. Therefore, a particularly reliable design for all enclosure components is essential.
[0004] Snap-fit connections are a simple and secure mechanical connection type also used in the housings of field devices. In many applications, snap-fit connections exert a preload on other components even when assembled, i.e., when the connection is snapped into place. This improves, for example, the vibration resistance of the other components, as they rub against each other less, resulting in less abrasion over time. This preload must, of course, be maintained across the entire operating range, especially at higher ambient temperatures. Particularly with plastics, there is a risk of "creep" or deformation, i.e., a reduction in clamping force, at elevated temperatures. Therefore, snap-fit connections are often designed to ensure sufficient preload even at high temperatures.However, this can lead to very high stresses occurring in the snap connection at low temperatures.
[0005] It is therefore an object of the invention to propose a spring element for a snap connection which is stable and reliable over the entire operating range and simultaneously optimizes material stresses. This object is achieved according to the invention by a spring element for a snap connection in a housing of a field device according to claim 1.
[0006] The spring element according to the invention comprises
[0007] a spring beam extending along a longitudinal axis between a first beam end and a second beam end, the spring beam having a front and a back opposite the front, a stiffening element arranged on the back and extending along the longitudinal axis between a first stiffening end and a second stiffening end,
[0008] wherein the stiffening element extends between the first stiffening end and the second stiffening end such that the stiffening element alternately reaches a first edge of the back and a second edge of the back opposite the first edge along a transverse axis arranged perpendicular to the longitudinal axis.
[0009] The spring element according to the invention enables a snap connection equipped with the spring element to function stably and reliably over a wide temperature range while simultaneously optimizing material stresses. This is achieved by the special shape of the stiffening element, which extends alternately between the edge regions of the spring beam. Thanks to the one-piece construction of the stiffening element, forces acting on the spring beam are absorbed and distributed by the stiffening element. Furthermore, the buckling load of the spring element is increased by the stiffening element.
[0010] According to one embodiment of the invention, the stiffening element has at the first stiffening end a first height extending along a load axis arranged transversely to the longitudinal axis and transversely to the transverse axis, and has at the second stiffening end a second height extending along the load axis, wherein the second height is greater than the first height, and / or wherein the first edge and the second edge taper conically towards the first stiffening end, and / or wherein the stiffening element tapers conically towards the first stiffening end.
[0011] According to a further embodiment of the invention, the stiffening element runs in a meandering shape from the first stiffening end to the second stiffening end.
[0012] According to one embodiment of the invention, the stiffening element forms several connected loops along the longitudinal axis, each loop having a loop curvature, the loop curvatures having opposite directions in successive loops.
[0013] According to one embodiment of the invention, each loop has a loop radius, and those loops which have the same direction with respect to the loop curvature are spaced apart from each other by a loop spacing, wherein the loop radius is greater than the loop spacing.
[0014] According to one embodiment of the invention, the loop radius of each loop and the loop spacing of each loop are identical.
[0015] According to one embodiment of the invention, the loop radius of each loop and the loop spacing of each loop are different.
[0016] According to one embodiment of the invention, the height of the stiffening element increases steadily from the first height to the second height.
[0017] According to one embodiment of the invention, the spring beam is formed in one piece with the stiffening element.
[0018] According to one embodiment of the invention, the spring element is made of an injection-moldable plastic.
[0019] According to one embodiment of the invention, the spring beam is welded, glued, or mechanically connected to the stiffening element. The aforementioned problem is further solved by a snap connection for a housing of a field device according to claim 12.
[0020] The snap connection according to the invention comprises:
[0021] a spring element according to the invention,
[0022] wherein a hook is arranged at the first beam end and the first stiffening end is arranged at the first beam end.
[0023] The invention is explained in more detail with reference to the following description of figures. The figures show:
[0024] - Fig. 1 : a perspective view of a spring element according to the invention,
[0025] - Fig. 2: a top view of the spring element shown in Figure 1,
[0026] - Fig. 3: a perspective view of the spring element shown in Figure 1 under force.
[0027] The spring element 1 according to the invention is suitable for use in a snap connection 2 in the housing of a field device 100. If the spring element 1 is used for a snap connection 2, the spring element 1 has a hook 4. First, however, the spring element 1 will be discussed in detail.
[0028] As shown in Figure 1, the spring element 1 comprises a spring beam 10 and a stiffening element 20.
[0029] The spring beam 10 extends along a longitudinal axis X between a first beam end 11 and a second beam end 12. The spring beam 10 has a front face 13 and a back face 14 opposite the front face 13. Preferably, the front face 13 and back face 14 are parallel to each other. However, it is also possible for the front face 13 and back face 14 to be arranged such that they taper to a point towards the first beam end 11. This increases the deformability of the spring beam 10 in the region of the first beam end 11. The spring beam 10 is made, for example, of a plastic, in particular an injection-moldable plastic, or of a readily bendable metal, i.e., a metal with high elasticity, or of a combination of these materials.
[0030] The stiffening element 20 is arranged on the rear side 14 of the spring beam 10 and extends along the longitudinal axis X between a first stiffening end 21 and a second stiffening end 22. The first stiffening end 21 is located in the region of the first beam end 11, preferably exactly at the first beam end 11. The second stiffening end 22 is located in the region of the second beam end 12, preferably exactly at the second beam end 12. When the first stiffening end 21 is flush with the first beam end 11 and the second stiffening end 22 is flush with the second beam end 12, the spring beam 10 is stiffened to its maximum extent by the stiffening element 20. If the first stiffening end 21 and / or the second stiffening end 22 are not flush with the first / second beam end, this results in a more easily deformable spring beam 10 in the area of the first and / or second beam end.
[0031] Preferably, the stiffening element 20 is formed integrally with the spring beam 10. This has the advantage that forces acting on the spring beam 10 are optimally transferred to the stiffening element 20. The stiffening element 20 is preferably made of plastic, in particular an injection-moldable plastic, or of a slightly flexible metal, i.e., a metal with high elasticity. Of course, it is also possible for the stiffening element 20 to be connected to the spring beam 10, for example, by gluing, welding, or mechanical joining.
[0032] As can be clearly seen in Figure 2, the stiffening element 20 extends between the first stiffening end 21 and the second stiffening end 22 such that the stiffening element 20 alternately reaches a first edge 15 of the back surface 14 and a second edge 16 of the back surface 14 opposite the first edge 15. The first edge 15 and the second edge 16 are preferably parallel to the longitudinal axis X. Of course, it is also possible that the first edge 15 and the second edge 16 are not parallel to each other, for example, tapering conically towards the first stiffening end 21. In other words, in this embodiment, the spring element 1, in particular the spring bar 10 and / or the stiffening element 20, has a conical shape in the direction of the longitudinal axis X, i.e., a shape that tapers towards the first stiffening end 21.In this case, the spring element 1 is more elastic at the first stiffening end 21 than at the second stiffening end 22. The conical taper of the stiffening element 20 means that its extension along the transverse axis Y decreases as the distance to the first stiffening end 21 decreases. In other words, the amplitude of the stiffening element 20 decreases in the direction of the first stiffening end 21. Amplitude is understood as an alternating propagation of the stiffening element 20 in the direction of the transverse axis Y (see Figure 2).
[0033] Alternatively, the first edge 15 is understood to be a first edge line parallel to the longitudinal axis X, and the second edge 16 is understood to be a second edge line parallel to the longitudinal axis X. In other words, in this alternative, the stiffening element 20 does not extend along the transverse axis Y to the lateral edge of the spring bar 10 (not shown). The first edge line is therefore spaced apart from the actual first edge 15 of the spring bar 10. The second edge line is therefore spaced apart from the actual second edge 16 of the spring bar 10.
[0034] The stiffening element 20 has a first height H1 at its first stiffening end 21, extending parallel to a load axis Z arranged transversely to the longitudinal axis X and transversely to the transverse axis Y. The stiffening element 20 has a second height H2 at its second stiffening end 22, extending parallel to the load axis Z. The second height H2 is preferably greater than the first height H1. Preferably, the height of the stiffening element 20 is designed such that there is a gradual, i.e., continuous, increase in height between the first stiffening end 21 and the second stiffening end 22 (see Figure 1). This has the advantage that the spring beam 10 is less stiff in the region of the first stiffening end 21 than in the region of the second stiffening end 22.If a force is applied to the spring beam 10 at the first beam end 11 along the load axis Z, the spring beam 10 deforms more in the region of the first beam end 11 than in the region of the second beam end 12 (see Figure 3). The force is preferably always applied to the front 13, as shown in Figure 4, so that the stiffening element 20 on the back 14 supports the spring beam 10. In other words, the spring beam 10 bends more at the first beam end 11 than at the second beam end 12. The gradually increasing thickness of the stiffening element also ensures varying stiffness along the spring beam. In particular, this results in the spring beam being more easily deformed at its thinner first beam end than at its thicker second beam end.
[0035] Preferably, the stiffening element 20 runs in a meandering shape between the first stiffening end 21 and the second stiffening end 22 (see Figure 2). Of course, it is also possible for the stiffening element 20 to form, for example, a sawtooth shape, a sinusoidal shape, or other continuous and alternating shapes.
[0036] Preferably, the stiffening element 20 forms several interconnected loops S1, S2, Si along the longitudinal axis X. The number i of loops naturally depends, among other things, on the length of the spring beam 10. The number i of loops also depends on the desired stiffness of the spring beam 10. This means that the more loops are formed on the spring beam 10, the stiffer, and thus more resistant to deformation along the load axis Z, the spring beam 10 becomes. As can be seen in Figure 2, the stiffening element 20 preferably terminates centrally on the back side 14 at the first stiffening end 21 and at the second stiffening end 22. Additionally, the direction of the stiffening element 20 at the first stiffening end 21 and at the second stiffening end 22 is parallel to the longitudinal axis X (see Figure 2).
[0037] Each loop S1, S2, Si has a loop curvature SK1, SK2, SKi. The loop curvatures SK1, SK2, SKi have opposite directions in successive loops S1, S2, Si. This means that, for example, the first loop curvature SK1 is mathematically negative, i.e., counterclockwise, when following the path of the stiffening element 20 starting from the first stiffening end 21, and the second loop curvature SK2 has a mathematically positive, i.e., clockwise, curvature. The same applies to the third loop curvature SK3 as to the first loop curvature SK1, and the same applies to the fourth loop curvature SK4 as to the second loop curvature SK2, and so on. Thus, a center line located centrally on the back side 14 is crossed by the stiffening element 20 with each loop S1, S2, Si.Thanks to this sinusoidal curve, an optimal distribution of forces acting along the load axis Z on the spring beam 10 and the stiffening element 20 is possible.
[0038] Each loop S1, S2, Si has a loop radius SR1, SR2, SRi. Preferably, the loop radius SR1, SR2, SRi is the same for all loops S1, S2, Si. Of course, it is also possible that, for example, every second loop has an identical loop radius. Furthermore, those loops S1, S2, Si that have the same direction with respect to the loop curvature SK1, SK2, SKi have a loop spacing SA1, SA2, SAi from each other. In other words, the first loop S1 and the third loop S3 are spaced apart by the first loop spacing SA1 (see Figure 2). The loop spacing is therefore measured at so-called constrictions between the loops along the longitudinal axis X.
[0039] According to an alternative embodiment (not shown), the loop radii are different from one another. This ensures that when the loops touch during bending about the transverse axis Y, a deformation or bending of the spring element 1 about the load axis Z occurs. Thus, the shape of the loops or ribs influences the shape of the spring element 1 under load.
[0040] Preferably, the loop radius SR1, SR2, SRi is larger than the loop spacing SA1, SA2, SAi. Preferably, the first height H1 and the second height H2 are equal to or greater than the first loop spacing SA1. Preferably, the loop radius, the loop spacing, and the height of the stiffening element 20 are selected such that, when a force F is applied along the load axis Z, the spring element 1 bends about the transverse axis Y such that the loop spacing is reduced to zero. In other words, from a predetermined force, the first loop S1 and the third loop S3, as well as the second loop S2 and the fourth loop S4, etc., touch. Preferably, the height of each loop is selected in such a gradual manner that from a predetermined force, i.e., a specific bending of the spring element 1, all numerically even loops S2, S4 and all numerically odd loops S1, S3 touch.This results in the spring element 1 exhibiting increased stiffness, and thus increased resistance, beyond a certain bending point. The spring element 1 therefore displays a progressive force curve under a steadily increasing load. Figure 3 illustrates the reduced loop spacing during bending.
[0041] Thanks to the stiffening element 20, the buckling load of the spring element 1 is increased.
[0042] Thanks to the spring element 1, the preload can be adjusted. A certain stiffness is achieved by selecting the loop radius, loop spacing, and loop height. This ensures the desired stiffness is maintained even at higher temperatures. Furthermore, the appropriate selection of loop spacing and loop height allows for additional stiffness to be achieved beyond a certain bending point of the spring element 1, specifically when the loops touch each other. The spring element 1 thus exhibits graduated stiffness. This is because, when the loops touch, a greater force is required to bend the spring element 1 further. [Reference numeral list]
[0043] 1 spring element
[0044] 2 Snap connection
[0045] 10 spring beams
[0046] 11 first beam end
[0047] 12 second beam end
[0048] 13 Front
[0049] 14 Back
[0050] 15 first marginal area
[0051] 16 second border area
[0052] 20 stiffening element
[0053] 21 first stiffening end
[0054] 22 second stiffening end
[0055] 100 field devices
[0056] H1 first height
[0057] H2 second height
[0058] 51 first loop
[0059] 52 second loop
[0060] SK1 loop curvature
[0061] SR1 Loop radius
[0062] SA1 Loop spacing
[0063] X Longitudinal axis
[0064] Y transverse axis
[0065] Z load axis
Claims
Patent claims 1. Spring element (1 ) for a snap connection (2) in a housing of a field device (100), comprising: - a spring beam (10) extending along a longitudinal axis (X) between a first beam end (11) and a second beam end (12), wherein the spring beam (10) has a front (13) and a back (14) opposite the front (13), - a stiffening element (20) arranged on the rear side (12) and extending along the longitudinal axis (X) between a first stiffening end (21) and a second stiffening end (22), wherein the stiffening element (20) extends between the first stiffening end (21) and the second stiffening end (22) such that the stiffening element (20) alternately reaches a first edge (15) of the back side (14) and a second edge (16) of the back side (14) opposite the first edge (15) along a transverse axis (Y) arranged perpendicular to the longitudinal axis (X).
2. Spring element (1) according to claim 1, wherein the stiffening element (20) has at the first stiffening end (21) a first height (H1) extending along a load axis (Z) arranged transversely to the longitudinal axis (X) and transversely to the transverse axis (Y), and at the second stiffening end (22) has a second height (H2) extending along the load axis (Z), wherein the second height (H2) is greater than the first height (H1), and / or wherein the first edge (15) and the second edge (16) taper conically towards the first stiffening end (21), and / or wherein the stiffening element (20) tapers conically towards the first stiffening end (21).
3. Spring element (1) according to claim 1 or 2, wherein the stiffening element (20) extends in a meandering shape from the first stiffening end (21) to the second stiffening end (22).
4. Spring element (1) according to claims 1 to 3, wherein the stiffening element (20) forms several connected loops (S1, S2, Si) along the longitudinal axis (X), each loop (S1, S2, Si) having a loop curvature (SK1, SK2, SKi), wherein the loop curvatures (SK1, SK2, SKi) have opposite directions in successive loops (S1, S2, Si).
5. Spring element (1) according to claim 4, wherein each loop (S1 , S2, Si) has a loop radius (SR1, SR2, SRi), and those loops (S1, S2, Si) which have the same direction with respect to the loop curvature (SK1, SK2, SKi) are spaced apart from each other by a loop spacing (SA1, SA2, SAi), wherein the loop radius (SR1, SR2, SRi) is greater than the loop spacing (SA1 , SA2, SAi).
6. Spring element (1 ) according to claim 5, wherein the loop radius (SR1 , SR2, SRi) of each loop (S1 , S2, Si) and the loop spacing (SA1 , SA2, SAi) of each loop (S1, S2, Si) are identical.
7. Spring element (1 ) according to claim 5, wherein the loop radius (SR1 , SR2, SRi) of each loop (S1 , S2, Si) and the loop spacing (SA1 , SA2, SAi) of each loop (S1, S2, Si) are different.
8. Spring element (1 ) according to one of the preceding claims, wherein the height of the stiffening element (20) increases continuously from the first height (H1) to the second height (H2).
9. Spring element (1 ) according to one of the preceding claims, wherein the spring beam (10) is formed integrally with the stiffening element (20).
10. Spring element (1) according to any one of the preceding claims, wherein the spring element (1) is made of an injection-moldable plastic.
11. Spring element (1) according to any one of claims 1 to 8, wherein the spring bar (10) is welded, bonded or mechanically connected to the stiffening element (20).
12. Snap connection (2) for a housing of a field device (100), comprising: - a spring element (1 ) according to one of the preceding claims, - wherein a hook is arranged at the first beam end (11 ) and the first stiffening end (21) is arranged at the first beam end (11).