EP2568487A1

EP2568487A1 - Linear motion electrical contact spring

Info

Publication number: EP2568487A1
Application number: EP11180646A
Authority: EP
Inventors: Jacobus Nicolaas Tuin
Original assignee: Tyco Electronics Nederland BV
Current assignee: TE Connectivity Nederland BV
Priority date: 2011-09-08
Filing date: 2011-09-08
Publication date: 2013-03-13

Abstract

The present invention relates to a contact spring (1) for contacting a mating contact in an electrically conductive manner, comprising a contact portion (2) adapted to contact the mating contact in a contact direction (C'), a base portion (3) adapted to be fixed to a substrate, and a spring portion (4) resiliently connecting the contact portion (2) to the base portion (3) and defining a deflection path (D) along which the contact portion (2) is deflectable in relation to the base portion (3). In order to provide an essentially linear deflection path (D), the spring portion (4) comprises at least a first and a second spring section (7a, 7b, 7c) which at least in an uncompressed state (U) of the contact spring (1) are arranged symmetrically to each other and essentially balance any forces acting transversally to the deflection path when a contact force (F_c) acts upon the contact portion (2) against the contact direction (C').

Description

The present invention relates to a contact spring for contacting a mating contact in an electrically conductive manner, comprising a contact portion adapted to contact the mating contact in a contact direction, a base portion adapted to be fixed to a substrate, and a spring portion resiliently connecting the contact portion to the base portion and defining a deflection path, along which the contact portion is deflectable in relation to the base portion.
Further, the present invention relates to a substrate for an electrical sensor arrangement and a kit for an electrical sensor arrangement comprising at least one contact spring and at least one substrate.
Contact springs, substrates for electrical sensor arrangements and kits for electrical sensor arrangements as mentioned above are known from the prior art. The contact springs are affixed to the substrate and protrude therefrom in a contact direction in order to contact a mating contact which is to be pressed onto the contact portion of the contact spring. The contact portion may then be pressed down in a compression direction of the contact spring which generates a spring force pressing the contact portion against the mating contact in order to assure a stable electrical contact between the contact portion and the mating contact. Thereby, vibrations acting upon the mating contact and/or the substrate may be absorbed without breaking the contact within the working range of the contact spring. Further, variations in distance between the contact portion and the mating contact may be compensated.
Contact springs known from the prior art suffer from the disadvantage that the deflection paths are not linear because e.g. their contact portions are pivoted about an axis of rotation defined by their spring sections. This may lead to sliding motions between the contact portion and the mating contact during compression of the contact spring which introduces noise and may damage the contact surfaces of the contact portion and/or the mating contact. The sliding motion between the contact portion and the mating contact is especially of disadvantage if the contact spring is used for contacting sensors for sound, especially impact sound, structure-born sound and acceleration. The measurements carried out with these sensors may be impaired by noises introduced into the sensor due to sliding motions between the contact portion of the contact spring and the mating contact associated with the sensor.
A way to minimize relative motions between the contact portion and the mating contact is realised in rigid needle adapters, which are also known as pogo-pins. In these adapters, a rod-like contact is led within a shaft and supported by a helical spring. However, especially for sensors measuring sound, the rigid needle adapters may not be applied because the rod and/or the spring may introduce noise due to their sliding motions with relation to the shaft. Further, manufacturing of the rigid needle adapters is rather expensive and time-consuming, since they consist of several parts which have to be provided and assembled.
Hence, in view of the disadvantages of contacts known from the prior art, it is an object of the present invention to provide a contact spring which avoids sliding motion between the contact portion and a mating contact, does not generate any noise and is easy to manufacture.
This object is achieved according to the present invention in that the spring portion comprises at least a first and a second spring section which, at least in an uncompressed state of the contact spring, are arranged symmetrically to each other and essentially balance any forces acting transversally to the deflection path when a contact force acts upon the contact portion against the contact direction. By balancing the forces acting within the spring transversally to the compression direction and/or deflection path, due to the symmetrical arrangement of at least a first and a second contact spring, an essentially linear deflection path is provided. Hence, there are no movements between the mating contact and the contact portion transversally to the compression direction. Thus, the generation of any sliding noises between the contact portion and the mating contact is avoided.
For the substrate mentioned above, the object is achieved in that the substrate is adapted to support a contact spring according to an embodiment of the present invention. This may be especially realised in that support and/or fixation areas provided on the substrate for bearing the contact spring are formed, shaped and arranged complementary to the base portion of the contact spring.
For the kit mentioned in the beginning of the description, the object is solved in that the contact spring is designed according to an embodiment of the present invention and/or the substrate is designed according to an embodiment of the present invention. Thereby, a user of the contact spring may assemble the sensor arrangement on site. He can therefore use the kit for complementing a substrate which he has at hand with the inventive contact spring. For example, the substrate could also be a sensor, such as a piezo-sensor. The kit could comprise the sensor and one contact spring or a plurality of contact springs could be attached thereto. A kit could then be applied by a user in that he affixes, e.g. glues, the sensor to a display and mates a contact point of the contact spring or contact points of each of the contact springs with an electrical conductor, e.g. on a PCB.
The above-mentioned solutions according to the present invention may be combined in any way with any one of the following advantageous embodiments of the present invention respectively and thus further improved.
According to a first improvement, at least in the uncompressed state, the first and the second spring sections are arranged symmetrically with respect to a point of symmetry lying on the deflection path or a line of symmetry which may equal the deflection path. Hence, the first and the second spring sections are arranged on two opposing sides of the deflection path and the forces exerted by the springs onto the contact portion transversally to the compression direction may be equalled out. Therefore, the first and the second spring sections may also be formed such that they are symmetrical with respect to the point of symmetry.
In order to improve the symmetry and therefore the balancing of any forces acting transversally to the compression direction, it may be provided that in a projection along the compression direction of the contact spring, at least in the uncompressed state, the first and the second spring sections are arranged symmetrically with respect to a contact point of the contact spring facing into the contact direction. The contact point may define a precise contact area, such as a zenith of the contact point, with which the contact spring may contact the mating contact.
Equalling out the forces acting transversally to the compression direction during compression may be further improved in that the contact spring may comprise at least two groups of spring sections arranged on opposite sides of the deflection path. The groups may further by formed symmetrically and/or symmetrically to each other. The groups of spring sections may comprise several spring sections which may each be formed symmetrically to the respective spring sections of the other group.
Spring forces exerted by the contact spring onto the contact may be homogenised along the deflection path of the spring and any forces acting transversally to the compression direction may be further balanced in that, at least in the uncompressed state, the spring is formed essentially symmetrical with a horizontal plane of symmetry, a normal vector of which is running essentially in parallel to the contact direction. Also, at least in the uncompressed state, the contact spring may be formed essentially symmetrical with at least one vertical plane of symmetry, a normal vector of which runs essentially perpendicularly to the contact direction. Thereby, at least in the uncompressed state, the contact spring may have a perfect symmetry which may or may not include the contact point because the contact point may be rather designed for an optimisation of the electrical contact and may therefore be free of mechanical stresses, i.e. the contact point does not necessarily have to be regarded in the symmetry of the rest of the contact portion, the base portion and the spring portion because the contact point itself does not need to be resilient.
In order to better support the contact spring on a substrate in a balanced manner for avoiding any sliding movement to the mating contact and the contact portion, it may be provided that the base portion comprises at least two feet which are separated from each other and are connected to different spring sections. The feet may also be shaped and arranged symmetrically.
For maximising the working range of the contact spring, it may be provided that it has no parts overlapping along a projection in parallel to the deflection path. Thereby, the contact portion, the base portion and/or the spring portion may interleave in the uncompressed state and/or in the maximum compressed state, which leaves room for folding the contact spring during compression such that a preferable long working range is provided. For interleaving, the spring sections, as well as any bends, bows and curvatures may be arranged that they lie in each other's shadows in a projection along a cross-direction and/or along a length direction of the contact spring.
Avoiding an overlapping of parts of the contact spring along a projection in parallel to the deflection path also facilitates that the contact spring may be integrally formed of stamped and/or rolled sheet material. In other words, the contact spring may be manufactured in that it is integrally stamped and then formed of sheet material. In the following it will therefore be referred to a contact spring which may be made of stamped sheet material. By forming the contact spring of stamped sheet material, such as stainless steel, phosphor bronze and/or brass, the contact spring may be manufactured in a fast and cost-effective way. During manufacturing, any excessive bending may be avoided according to the inventive shape of the contact spring. That is, when the contact spring is stamped out, it is merely bent to have its desired height measured in its height direction and no further biasing members as known from contact springs according to the prior art are necessary because the contact spring according to the present invention already has its desired resiliency.
The resilient properties and characteristics of the contact spring may be further improved in that at least one of the spring sections may be tapering. The shape of the at least one spring section may taper in a projection along the compression direction, which makes the tapering easy to manufacture when the contact spring is made of stamped sheet material. The tapering can form a neck, i.e. an area where the cross-sectional area of the spring section is reduced with respect to other areas of the spring section, thus making it possible to homogenise the spring forces along the spring section. In other words, a contact spring according to the present invention enables that stresses are evenly distributed along the spring section, especially along a length direction of the spring section.
With a contact spring according to an embodiment of the present invention, it may be provided that a quotient of the spring's maximum height in the uncompressed state divided by its minimal height in a maximum compressed state exceeds the value of 3.5 and/or a quotient of its force range divided by a working range of the contact spring along the deflection path is below the value of 1. Thereby, the contact spring has a rather long working range with respect to its force range. The quotient or its height in the uncompressed state divided by its minimal height in the maximum compressed state may be 3.6 for example or at least 3. The shape of the spring may be such that no undesired peaks in forces occur along the deflection path and the forces rather increase on a diminishing scale along the deflection path.
For increasing the durability of the contact spring, it may be provided that under compression along the deflection path, the von Mises-Stress within the contact spring does not exceed 1200, 1000 or 750 MPa depending on the chosen material. For example, a maximum von Mises-Stress of 1000 MPa may be suitable for a contact spring made of steel whereas a maximum von Mises-Stress of 750 MPa may be suitable for phosphor bronze. Thereby, the contact spring is not prone to be accidentally irreversibly bent and therefore lose its resiliency or maximum height compared to the initial uncompressed state.
The invention will be described in more detail by way of example hereinafter with reference to the accompanying drawings which illustrate advantageous embodiments. The described embodiments are only possible configurations in which the individual features may, however, as described above, be implemented independently of each other or be omitted. Corresponding elements illustrated in the drawings are provided with the same reference signs. Parts of the description relating to the same elements in different drawings are omitted.
In the drawings:

Fig. 1: is a schematic perspective view of a contact spring according to an embodiment of the present invention in an uncompressed state;
Fig. 2: is a schematic top view of the contact spring shown in Fig. 1;
Fig. 3: is a schematic side view of the contact spring shown in Figs. 1 and 2;
Fig. 4: is a schematic perspective view of the contact spring shown in Figs. 1 to 3 in a maximum compressed state;
Fig. 5: is a schematic perspective view of spring sections of the contact spring illustrated in Figs. 1 to 4 in the uncompressed and in the maximum compressed state; wherein stress distributions within the contact spring in the maximum compressed state are schematically shown;
Fig. 6: is a schematic side view of the spring sections shown in Fig. 5;
Fig. 7: is a force over deflection diagram of the contact spring shown in Figs. 1 to 6; and
Fig. 8: is a schematic perspective view of a spring contact according to the prior art.

In the following, a contact spring 1, a substrate (not shown) for the contact spring 1 and a kit comprising at least one of the contact spring 1 and the substrate are explained with reference to the respective embodiments thereof shown in the figures. Fig. 1 is a schematic perspective view of the contact spring 1. The contact spring 1 comprises a contact portion 2, a base portion 3 and a spring portion 4.
The contact portion 2 protrudes from the base portion 3 in a height direction Z of the contact spring 1 and against a compression direction C of the contact spring, the compression direction running in parallel to the height direction Z. The contact portion 2 comprises a contact plate 5 and a contact point 6. The contact plate 5 extends along a length direction X and a cross-direction Y of the contact spring 1. The length direction X runs perpendicularly to the cross-direction Y and the height direction Z. In other words, the contact plate is aligned with a plane extending in the length direction X and the cross-direction Y.
The contact point 6 slightly protrudes from the contact plate in a contact direction C' of the contact spring 1. The contact direction C' runs reverse into the compression direction C, i.e. the contact direction C' in the embodiment shown in Fig. 1 is equivalent to the height direction Z. The contact point 6 is shaped like a lens or flat dome in order to provide a precise contacting of a mating contact (not shown).
The base portion 3 comprises two plate- like feet 3a, 3b which protrude from the contact spring in the compression direction C. The undersides of the feet 3a, 3b each provide a mounting surface or soldering area which may be soldered to a substrate or may be otherwise affixed thereto in a positive fit, friction fit, metallic continuity and/or adhesive bond. In other words, the feet 3a, 3b have a plate-like shape and are aligned with, i.e. coplanar to, a plane extending in the length direction X and the cross-direction Y.
The spring portion 4 comprises two groups of spring sections 4a, 4b. Each of the groups 4a, 4b comprises three spring sections 7a, 7b and 7c. The spring sections 7a, 7b are each connected to the feet 3a, 3b via bends 8a, 8b, respectively. The bends 8a, 8b on both sides of the feet 3a, 3b are curved in a projection along the cross-direction Y from in and against the length direction, respectively, towards the height direction Z such that the feet 3a, 3b slightly protrude from the spring sections 7a, 7b against the height direction Z, i.e. in the compression direction C. The spring sections 7c are connected to the contact plate 5 of the contact portion 2 via bends 8c. The bends 8c are curved in a projection along the cross-direction Y from the height direction in and against the length direction X, respectively, such that the contact plate 5 protrudes from the spring sections 7c in the contact direction C'.
The spring sections 7a are each connected to the spring sections 7c by a curvature 9a. The spring sections 7b are each connected to the spring sections 7c by a curvature 9b. In other words, the spring sections 7a, 7b yield into the spring section 7c via the curvatures 9a, 9b, respectively, which have an arch-like shape in a projection along the height direction Z. The curvatures 9a, 9b are arranged in a plane essentially extending in parallel to the length direction X and the cross-direction Y.
From an uncompressed state U shown in Fig. 1, the contact spring 1 may be compressed along a deflection path D in parallel to the compression direction C and against the contact direction C' by a contact force (not yet shown) impinging onto the contact point 6 in the compression direction C.
Fig. 2 is schematic top view of the contact spring 1 illustrated in Fig. 1. Here it becomes apparent that in a projection along the height direction Z, the spring section 7a of the group spring sections 4a is formed and arranged symmetrically to the spring section 7b of the group of spring sections 4b with respect to a point of symmetry P_xy lying on the deflection path D. The spring section 7b of the group of spring sections 4a is shaped and arranged symmetrically to the spring section 7a of the group of spring sections 4b. Analogously, the bend 8a and curvature 9a of the group of spring sections 4a are shaped and arranged symmetrically to the bend 8b and curvature 9b, respectively, of the group of spring sections 4b with respect to the point of symmetry P_xy.
In a projection along the height direction Z, the bend 8b and curvature 9b of the group of spring sections 4a are arranged symmetrically to the bend 8a and curvature 9a of the group of spring sections 4b with respect to the point of symmetry P_xy. The foot 3a is shaped and arranged symmetrically to the foot 3b with respect to the point of symmetry P_xy. The contact plate 5 is shaped and arranged symmetrically around the point of symmetry P_xy.
Hence, in view of the above explanations regarding Fig. 2, in a projection along the height direction Z, the contact spring 1 is shaped and arranged symmetrically around the point of symmetry P_xy, i.e. is regarded as only having two dimensions in a plane extending in the length direction X and in the cross-direction Y. The above-explained symmetries with respect to the point of symmetry P_xy are defined all in a projection along the height direction Z.
Furthermore, when taking into account the height direction Z in addition to the length direction X and the cross-direction Y, the above explanations regarding the symmetry of the contact spring 1 with respect to the point of symmetry P_xy analogously apply to a symmetry of the contact portion 2, the base portion 3 and the spring portion 4 with respect to a first line of symmetry, namely a height axis H of the contact spring 1 extending in parallel to the height direction Z analogously to the deflection path D through a zenith 10, i.e. peak of the contact point 6.
Moreover, the entire contact spring 1 is shaped symmetrically with respect to a first vertical plane of symmetry S_xz, extending in the length direction X and the height direction Z and comprising a length axis L of the contact spring 1, as well as with respect to a second vertical plane of symmetry S_yz, extending in the cross-direction Y and the height direction Z and comprising a transversal or cross axis T of the contact spring 1.
As can also be seen in Fig. 2, the spring sections 7a, 7b and 7c are provided with a neck or tapering 11 a, 11 b and 11 c, respectively, in a projection along the height direction Z.
Fig. 3 is a schematic side view of the contact spring 1 illustrated in Figs. 1 and 2. Here it becomes apparent that in a projection along the cross-direction Y, the spring section 7c of the group of spring sections 4a is shaped and arranged symmetrically to the spring section 7b of the group of spring sections 4b with respect to a point of symmetry P_xz lying essentially in a balance point or centroid M of the contact spring 1, where the height axis H and the length axis L cross.
In a projection along the cross-direction Y, the curvatures 9a, 9b of the group of spring sections 4a are arranged symmetrically to the curvatures 9a, 9b of the group of spring sections 4b with respect to the point of symmetry P_xz. In a projection along the cross-direction Y, the contact plate 5 is arranged symmetrically to the feet 3a, 3b with respect to the point of symmetry P_xz. Hence, except for the contact point 6, in a projection along the cross-direction Y, the contact spring 1 is shaped symmetrically around the point of symmetry P_xz. Each of the feet 3a, 3b provides a planar support or solder area 14 on which the contact spring 1 may be supported and which may serve for affixing the contact spring 1 to a substrate.
In the side view illustrated in Fig. 3, it further becomes apparent that the contact spring 1 has a bi-concave shape with its upper half comprising the contact portion 2 and the spring sections 7c forming a bow-like contact arch 12 having a height h₁₂ measured in the height direction Z. the contact spring further comprises two bow-like base arches 13 including the foot 3a as well as the spring sections 7a and the foot 3b as well as the spring sections 7b. The base arches 13 each have a height h₁₃ measured in the height direction Z. The heights h₁₂ and h₁₃ as well as a height h₆ of the contact point 6 altogether add up to an overall height h₁ of the contact spring 1, measured in the height direction Z. The base arches 13 are resiliently connected to the contact arch 12 via the curvatures 9a, 9b which merge into the spring sections 7c.
Furthermore, in a projection along the cross-direction Y, the arches 12 and 13 are shaped and arranged symmetrically to each other with respect to the point of symmetry P_xy and the second axis of symmetry T which is the transversal or cross axis of the contact spring and runs through the balance point M in parallel to the cross direction Y. Each of the arches 12 and 13 is also shaped and arranged symmetrically with respect to a second vertical plane of symmetry S_yz, comprising a height axis H of the contact spring 1 running through the balance point M in parallel to the height direction Z.
Fig. 4 is a schematic perspective view of the contact spring 1 in a maximum or fully compressed state V. In the maximum compressed state V, a mating contact (not shown) presses down the spring portion 2 against the height direction Z along the deflection path D with a contact force F_c acting or impinging on preferably the zenith 10 of the contact point 6. The contact spring 1 acts against the contact force F_c with a spring force F_s equalling the contact force F_c out by acting in the contact direction C', whereas the contact force F_c acts in the compression direction C.
Even in the maximum compressed state V, the contact spring 1 maintains its symmetry as described above with respect to the first vertical plane of symmetry S_xz and the second vertical plane of symmetry S_yz- Moreover, in a projection against the height direction Z, the contact spring 1 maintains its rotational symmetry around the point of symmetry P_xy.
Hence, due to maintaining its symmetry, as described above, while being transferred from the uncompressed state U to the maximum compressed state V, the deflection path D runs linearly in parallel to the contact direction C' and the contact force F_c. Thus, any transverse movements of the contact point 6 within a plane extending in a length direction X and in the cross-direction Y are prevented.
Further, in the maximum compressed state V, the contact plate 5 acts as an additional contact spring in that it is bent downwardly. At the same time, the feet 3a, 3b may remain plane, i.e. they do not bend upwardly in the height direction Z.This may at least in part be achieved by a safe and enduring affixation of the contact spring 1 on the substrate.
Fig. 5 is a schematic perspective view of a part of the contact spring 1 in the uncompressed state U and the maximum compressed state V. Here, the linearity of the deflection path D becomes apparent. Further, it can be seen that in the uncompressed state U, the contact spring 1 is essentially free of mechanical stresses.
In the maximum compressed state V, a stress distribution within the contact spring 1 is such that the contact point 6 and the feet 3a, 3b remain essentially stress-free with a minimum mechanical stress δ_min of nearly 0 MPa. Also, the middle sections of the spring sections 7a, 7b and 7c, i.e. the areas of these spring sections in their middle measured essentially along the length direction X remain essentially stress-free with a minimal stress δ_min of nearly 0 MPa. In contrast, mechanical stresses build up in the contact plate 5, the spring sections 7a, 7b, 7c, the bends 8a, 8b, 8c, and the curvatures 9a, 9b, where a maximum mechanical stress δ_max of on average 750 MPa and peaks of up to 850 MPa are encountered.
Fig. 6 shows the contact spring 1 in the uncompressed state U and the maximum compressed state V analogously to Fig. 5 in a schematic side view. Here it becomes apparent that the deflection path D has a length I_D. The height h₁ of the contact spring in the uncompressed state U decreases to a height h'₁ in the compressed state, which equals the height h₁ minus the length I_D.
Further, in Fig. 6 it becomes apparent that in the fully-compressed state V, a transition zone between the spring sections 7c and the curvature 9b is bent downwardly, whereas a transition zone between the bend 9b and the spring section 7b is bent upwardly. Hence, in at least a portion of the curvatures 9a, 9b mechanical stresses build up. Thus, the curvatures 9a, 9b act as additional spring sections in that they generate a spring momentum around an axis running in parallel to the length axis L through the middle of each of the curvatures 9a, 9b.
Fig. 7 is a force over deflection diagram showing the behaviour of the contact spring 1 illustrated in Figs. 1 to 6. The contact spring 1 has a working range R_w of approximately 0.6 to 0.7 (dimensionless) measured in parallel to the height direction Z and equalling the length I_D of the deflection path D, a force range R_F equalling the spring forces F_s along the deflection path D is approximately 0.7 (dimensionless). The working range R_w starts at a minimal required contact force F_c,min of approximately 1.2 and may exceed the half of a maximal compression C_max of the contact spring 1 of approximately 1.4. The maximal compression is possible without yielding and leads to a maximum possible contact force F_c,max of approximately 1.95 which is the sum of the minimal required contact force F_c,min and the force range R_F.
Fig. 8 is a schematic perspective view of a contact spring 100 as known from the prior art. The contact spring 100 comprises a contact portion 102, a base portion 103 and a spring portion 104, which connects the contact portion 102 to the base portion 103. The contact spring 100 further comprises a biasing element 101, which biases the contact portion 102 in a pre-loaded position under a certain initial compression C_i,₁₀₀.
A hook-like contact section 105 of the contact portion 102 is provided with a contact point 106 and a zenith 110 which faces into a contact direction C'. When the contact spring 100 is pressed down at the contact point 110 in a compression direction C, the contact section 105 rotates about the spring section 107 in a rotation around an axis of rotation A which runs essentially in parallel to the cross-direction Y. Hence, the contact point 106 has a curved deflection path D₁₀₀. Thus, there will be relative movements between a mating contact and the contact point 6 at least in parallel to the length direction X.
Deviations from the above-described embodiments of a contact spring 1 according the present invention are possible without departing from the inventive idea. The contact spring 1 may be provided with a contact portion 2, a base portion 3 and a spring portion 4 in whatever shape, form and arrangement necessary for providing the desired linear deflection path D and appropriate working range R_w as well as force range R_F. Hence, the contact plate 5 and the contact point 6 may also be shaped, formed and arranged as desired. There may be one single foot 3a, 3b, but also a larger number of feet 3a, 3b. Especially, providing the contact spring 1 with at least two feet 3a, 3b may be advantageous to support the contact forces F_c in a balanced manner.
Further, the contact spring 100 may be provided with groups of spring sections 4a, 4b in whatever number, form, shape and arrangement desired for achieving the desired linear spring path D. Therefore, the spring sections 7a, 7b, 7c, bends 8a, 8b, 8c and curvatures 9a, 9b should be arranged such that at least in part they are arranged symmetrically and provide a balancing of forces acting within the spring 1 transversally to the compression direction C.
Also the zenith 10, necks 11 a, 11b, 11c, contact arch 12, base arch 13 and support area 14 may be formed such as desired for providing a contact spring 1 with a preferably linear deflection path D.
A symmetry of the contact spring 1 in a projection along the cross-direction Y with respect to the point of symmetry P_xy and the second axis of symmetry T, as described while referring to Fig. 3 above, is especially of advantage for facilitating the manufacture of the contact spring but is not mandatory for a linear deflection path D. The symmetry that is most beneficial for facilitating a manufacturing of the contact spring 1 is that of arch 12 and 13 about the horizontal plane S_xy.

Claims

Contact spring (1) for contacting a mating contact in an electrically conductive manner, comprising
a contact portion (2) adapted to contact the mating contact in a contact direction (C'),
a base portion (3) adapted to be fixed to a substrate, and
a spring portion (4) resiliently connecting the contact portion (2) to the base portion (3) and defining a deflection path (D) along which the contact portion (2) is deflectable in relation to the base portion (3),
characterised in that
the spring portion (4) comprises at least a first and a second spring section (7a, 7b, 7c) which at least in an uncompressed state (U) of the contact spring (1) are arranged symmetrically to each other and essentially balance any forces acting transversally to the deflection path when a contact force (F_c) acts upon the contact portion (2) against the contact direction (C').
Contact spring (1) according to claim 1 characterised in that at least in the uncompressed state (U) the first and the second spring section (7a, 7b, 7c) are arranged symmetrically with respect to a point of symmetry (P_xy, P_xz) lying on the deflection path D.
Contact spring (1) according to claim 1 or 2 characterised in that in a projection along a compression direction (C) of the contact spring 1, at least in the uncompressed state (U), the first and the second spring sections (7a, 7b, 7c) are arranged symmetrically with respect to a contact point (6) of the contact spring (1) facing into the contact direction (C').
Contact spring (1) according to one of claims 1 to 3 characterised in that the contact spring (1) comprises at least two groups of spring sections (4a, 4b) arranged on opposite sides of the deflection path (D).
Contact spring (1) according to one of claims 1 to 4 characterised in that, at least in the uncompressed state (U) in a projection along a cross-direction (Y) of the contact spring (1), the contact spring (1) is formed essentially symmetrical with a horizontal plane of symmetry (S_xy), a normal vector of which is running essentially in parallel to the contact direction (C').
Contact spring (1) according to one of claims 1 to 5 characterised in that, at least in the uncompressed state (U), the contact spring (1) is formed essentially symmetrical with at least one vertical plane of symmetry (S_xz, S_yz), a normal vector of which runs essentially perpendicularly to the contact direction (C').
Contact spring (1) according to one of claims 1 to 6 characterised in that the contact spring (1) comprises a bow-like contact arch (12) and/or at least one bow-like base arch (13).
Contact spring (1) according to one of claims 1 to 7, characterised in that the base portion (3) comprises at least two feet (3a, 3b) which are separated from each other and are connected to different spring sections (7a, 7b, 7c).
Contact spring (1) according to one of claims 1 to 8 characterised in that the contact spring (1) has no parts overlapping along a projection in parallel to the deflection path (D).
Contact spring (1) according to one of claims 1 to 9 characterised in that the contact spring (1) is integrally formed of stamped and/or rolled sheet material.
Contact spring (1) according to one of claims 1 to 10 characterised in that at least one of the spring sections (7a, 7b, 7c) is tapering.
Contact spring (1) according to one of claims 1 to 11 characterised in that a quotient of a maximum height (h₁) of the contact spring (1) in the uncompressed state (U) divided by its minimal height (h₁') in a maximum compressed state (V) exceeds the value of 3.5 and/or a quotient of its force range (R_f) divided by a working range (R_w) of the contact spring along the deflection path (D) is below the value of 1.
Contact spring (1) according to one of claims 1 to 12 characterised in that under compression along the deflection path, (D) the von Mises-Stress within the contact spring (1) does not exceed 1000 MPa.
Substrate for an electrical sensor arrangement characterised in that the substrate is adapted to support a contact spring (1) according to one of claims 1 to 13 above.
Kit for an electrical sensor arrangement comprising at least one contact spring and at least one substrate characterised in that the contact spring (1) is designed according to one of claims 1 to 13 and/or the substrate is designed according to claim 14 above.