Proximity sensor with improved impact and shock resistance

Abstract

Proximity sensor (1, 30, 60, 100, 120) comprising a housing (2, 31, 61, 101) having an interior space (18, 38, 68, 108) in which an electronic assembly (27, 39, 69) and an electrical sensor element (29, 41, 70) arranged thereon are located, wherein the housing (2, 31, 61, 101) comprises a side wall (14, 44, 62, 124) and a front section (3, 32, 64, 112), wherein the housing (2, 31, 61, 101) has at least one layer of deformable material, characterized in that the housing (31, 61) has circumferential Grooves (45, 46, 47, 73, 74, 75) which form expansion spaces (45, 46, 47, 73, 74, 75) in which a fluid is located or a vacuum or a strong negative pressure prevails.

Description

[0001] The invention relates to a proximity sensor according to the preamble of patent claim 1.

[0002] Proximity sensors are used, for example, in technical processes to detect the position of workpieces and tools. Such proximity sensors respond to approach without contact, i.e., without direct contact.

[0003] If these proximity sensors are to be used in hazardous areas (areas with a risk of explosion), they must pass an impact test in which they are exposed to a certain impact energy, because ignition sources must not occur in hazardous areas. The desired impact and shock resistance can be achieved through additional protective devices, such as damping and spring elements.

[0004] From DE 10 2012 223 261 B4 and from DE 10 2012 200 478 A1 such a proximity switch with an impact and shock absorption device is known, which has an upper part and a lower part, wherein the upper part contains the components to be protected against impact and shock and the lower part serves for fastening on a support surface, wherein between the upper part and the lower part a damping element for damping impacts and shocks is arranged.

[0005] Furthermore, DE 10 2015 221 312 B3 describes an inductive sensor with a cylindrical housing made of rigid material, which has a front cover, a cylinder tube and a rear plug with an electrical connection, as well as a first O-ring arranged between the front section and the cylinder tube, and a second O-ring, wherein the second O-ring is positioned by an annular groove in the front section and a support in the cylinder tube and is deformable by impact or shock on the front section, wherein the front section and the cylinder tube have corresponding front-side widenings serving as stops, wherein in the unloaded state an air gap is present between the first widening in the plug and the second widening in the cylinder tube, wherein a displacement path of the cover is determined by the width of the air gap,and wherein the displacement dampens the energy of a blow and / or impact.,

[0006] The housing and the front section of the known proximity switches are made of hard and therefore rigid materials, which is why additional protective devices are used to absorb the shock.

[0007] A proximity switch with a housing made of deformable material is described, for example, in DE 198 22 354 A1. DE 198 22 354 A1 relates to a plug insert for cylindrical proximity switches, consisting of a sleeve-shaped receiving part, into which a cylindrical plug with a plurality of electrically conductive pins or sockets penetrating the plug in the direction of the receiving part is sealingly inserted for making electrical contact with a coupling part that can be placed on the plug. For water- and dust-tight sealing of the plug within the receiving part, the plug has at least one rounded or lip-shaped sealing element integrally formed on its casing, which runs peripherally around the plug in a cross-sectional plane of the plug, wherein the plug and sealing element are made of a thermoplastic elastomer.

[0008] Furthermore, DE 100 13 218 A1 discloses a method for manufacturing a position sensor with a housing, in the interior of which an electrical circuit is arranged on a carrier. This method is quick and cost-effective. For this purpose, the carrier is connected to an electrical connection element to form a carrier-connection element combination. The carrier-connection element combination is inserted into the housing, which is closed at one measuring end, from the rear end opposite the measuring end. The space around the carrier-connection element combination in the housing interior is filled to a certain level with a molding compound, and a cap is connected to the rear end of the housing.

[0009] Furthermore, DE 10 2007 010 467 B4 discloses an inductive proximity switch with a stainless steel housing, two transmitting coils, two receiving coils arranged symmetrically to the transmitting coils and connected in series in opposite directions, and one connected to the receiving coil. The transmitting coils are arranged concentrically to the receiving coils, and the inner diameter of the outer transmitting coils is larger than the outer diameter of the inner receiving coils.

[0010] Furthermore, DE 103 59 885 A1 describes a method for manufacturing a switching device with a sensor unit arranged at a measuring end of a housing sleeve and connected to an electronic circuit arranged on a carrier received in the housing sleeve, and with a connection part arranged at a rear end of the housing sleeve. The method is characterized in that the sensor unit, the carrier, and the connection part, together with a shield enclosing the carrier, are assembled to form a dimensionally stable assembly, and that the assembly is subsequently inserted into the housing sleeve and held there in a fixed manner.In a further aspect, the invention relates to an assembly for a switching device for installation in a housing sleeve, comprising a sensor unit with a sensor for detecting a measurement signal, and an electronic circuit arranged on a carrier, wherein the carrier is rigidly connected to the sensor unit at one measuring end. The circuit is electrically connected to the sensor unit and comprises a shield enclosing the carrier, which is rigidly connected to the sensor unit and / or to the carrier, and a connector for connecting the circuit to external devices, which connector is placed on the carrier and / or on the shield.

[0011] However, these sensors described so far have only insufficient impact and shock resistance.

[0012] EP 2 072 967 A1 describes a sensor with improved impact and shock resistance compared to the sensors described above. It is an electronic sensor, in particular an inductive sensor, with a housing sleeve, with a sensor element for measuring a physical variable, which is arranged at a measuring end of the housing sleeve, with an electronic assembly arranged in the housing sleeve and with a connecting piece which is arranged at a connection end of the housing sleeve opposite the measuring end. The sensor is characterized in that the housing sleeve is provided with an inner lining made of plastic, that the inner lining is closed at the measuring end of the housing sleeve, and that the inner lining extends through to the connection end of the housing sleeve far enough that the connecting piece is in sealing engagement with the inner lining.EP 2 072 967 A1 further relates to a method for producing this sensor.

[0013] The object of the present invention is to provide a proximity sensor with an even further improved impact and shock resistance compared to the known solutions, without the need for additional protective devices.

[0014] This problem is solved according to the features of patent claim 1.

[0015] The invention relates to a proximity sensor comprising a housing, wherein the housing has a side wall comprising at least one side wall, and a front section on a front side. The housing contains at least one layer of deformable material, whereby the housing is deformable. The housing can have only one layer of deformable material or else a layer system consisting of several layers of deformable material. In this case, it is possible to reinforce at least the one layer of deformable material with a fiber system. An end cap is arranged on a rear side of the housing, which likewise contains a deformable material and can also be fiber-reinforced. Also provided on the rear of the housing is an electrical connection which can be passed through the end cap and can be electrically connected to an electronic assembly.The front section of the housing can also be designed as a removable cover.

[0016] The advantage of the deformable material is that it is not only easily deformable but also tear-resistant, in contrast to hard and therefore rigid materials such as hard plastics, metal or ceramics - materials from which the housings of proximity sensors have previously been made.

[0017] If an impact is exerted on the front section during an impact test, the front section can absorb this impact impulse and convert it into potential deformation energy. Due to the deformation, the front section can transfer the force to a compressible element by the deformable front section moving into the compressible element. This compressible element is inserted as a filler in an interior space of the housing. The tear resistance of the housing material prevents the front section from developing cracks, which would otherwise damage the housing. Because the breaking elongation of the material is sufficiently large, the front section cannot be damaged by the impact, thus preventing the creation of an ignition source. The proximity sensor may therefore lose its function, but it may not become an ignition source, for example due to cracks.

[0018] If the end cap also consists of at least one layer of deformable material, the entire interior of the housing of the proximity sensor is surrounded by at least one layer, i.e. in the case of several layers by a layer system, which consists of a deformable material, whereby the proximity sensor is particularly impact-resistant because the deformation can be passed on to the compressible filling material. The filling material can be, for example, resin (e.g. casting resin or foam resin) or a fluid (e.g. air). It is also advantageous that the housing is able to absorb changes in the volume of the filling material. These changes in the volume of the filling material can occur in particular due to changes in temperature, for example an increase in temperature.

[0019] Materials that are easily deformable and also have high ductility are suitable for the housing. In explosion-hazardous areas, these are, for example, materials made of - Elastomers (for example fluororubber based rubber materials, HNBR or EPDM) or - thermoplastic elastomers (for example TPE-U, TPE-A, TPE-O) and - Subsequently cross-linked thermoplastic elastomers (such as TPE-V). The advantage of elastomers and thermoplastic elastomers is that they exhibit a sufficiently high elongation at break with sufficiently high stiffness (shear modulus and shear modulus), which means that the resulting components are highly deformable and do not crack. These elastomers can also be manufactured to be electrostatically dissipative, allowing the proximity sensor to be used in potentially explosive atmospheres without any problems.

[0020] In principle, however, steels can also be used, provided they are highly ductile, such as metallic materials with a cubic face-centered crystal structure (e.g. chromium-nickel steels [trade name V2A-Stähle®] and chromium-nickel-molybdenum steels or chromium-manganese-molybdenum steels (trade name V4A-Stähle®]).

[0021] What is important with this deformable material, which is used for at least one layer of the housing, is that this material has a minimum deformability of at least 2% and a hardness in the range of 10 Shore D to 100 Shore D.

[0022] According to the invention, the housing has a plurality of grooves on an outer side of the side wall. These grooves form expansion spaces, wherein these expansion spaces are arranged between the side wall of the housing and an inner side of the outer housing. These expansion spaces form further compressible elements. A gaseous fluid, a liquid fluid, or a vacuum or a strong negative pressure exists in the expansion spaces. Preferably, a gaseous fluid, for example, air or an inert gas, is located in the expansion spaces, which is preferably enclosed in a foamed material. If the volume of the compressible element located in the interior of the housing changes due to temperature changes, these expansion spaces additionally serve to absorb volume changes of the compressible element across the entire application temperature range.The compressible element present as a filling material preferably has a minimum deformability of at least 2% and a hardness in the range of 10 Shore D to 100 Shore D. In addition to the minimum requirement of good extensibility, such materials also have a sufficiently high resistance, which ensures that the impact energy in the filling material is converted into deformation energy.

[0023] In one embodiment, the proximity sensor has an outer housing that at least partially surrounds the side wall of the housing. The outer housing is preferably made of a metal or a metal alloy, such as steel. This provides the proximity sensor with sufficiently high stability.

[0024] Preferably, the outer housing has a thread on an outer side.

[0025] This allows the proximity sensor to be easily and quickly mounted in a device, for example in an industrial plant in which the measurements are to be carried out.

[0026] A protective cover can also be arranged inside the housing, which is connected to the inside of the housing by means of a flexible adhesive. This protective cover allows the proximity sensor on the front of the housing to deform. If an impact is applied to the front of the proximity sensor, the front deforms toward the interior. This transfers the energy of the impact to the protective cover, causing it to deform. This means that the protective cover converts the impact energy into potential deformation energy.

[0027] In another embodiment, the housing of the proximity sensor is arranged on a base plate. The proximity sensor can be connected to a system via this base plate. This proximity sensor has a base that is completely surrounded by the housing, whereby the interior space is formed by the housing and the base. This arrangement prevents any external medium, such as outside air, from entering the interior space.

[0028] Advantageously, the base plate has a lower section and an upper section, with a circumferential gap running between the upper and lower sections of the base plate. A compressible medium is located in this gap, forming a spring element that can further cushion any impact exerted on the housing.

[0029] In a particular embodiment, the proximity sensor has a protective element. This protective element is connected at a first end to the side wall of the housing and at a second end to the lower section of the base plate. The protective element creates a space filled with a compressible medium, for example, air or inert gas. This space is formed by the circumferential gap and a main chamber. This protective element prevents particles, such as dust, from entering the gap, and the gap filled with the compressible fluid remains as a spring element.

[0030] It is also explicitly proposed to combine several features of the individual described embodiments.

[0031] The present invention is explained in more detail below with reference to the accompanying drawings. They show: Fig. 1 a perspective view of a proximity sensor; Fig. 2 a longitudinal section through the proximity sensor according to Fig. 1; Fig. 3 a first variant of the proximity sensor according to Fig. 1; Fig. 4 a longitudinal section through the proximity sensor according to Fig. 3; Fig. 5 an exploded view of the proximity sensor according to Fig. 3; Fig. 6 a longitudinal section through a second variant of the proximity sensor according to Fig. 1 Fig. 7 a fourth variant of the proximity sensor; Fig. 8 a section through the Fig. Proximity sensor shown in Figure 7; Fig. 9 an enlarged section of the Fig. 8 shown proximity sensor; Fig. 10 a fifth variant of the Fig. 8 shown proximity sensor and Fig. 11 an enlarged section of the Fig. 10 shown proximity sensor.

[0032] In Fig. Figure 1 shows a perspective view of a proximity sensor 1 with a housing 2, wherein only a front section 3 of the housing 2 can be seen. This housing 2 can - as in Fig. 1 – be cylindrical. However, the housing 2 can also be oval or rectangular, for example.

[0033] This front section 3 is arranged on a front side 4 of the housing 2, whereby the front side 4 of the housing 2 also forms the front side of the proximity sensor 1. An end cap (not visible) is provided on a rear side 5 of the housing 2, which at least partially encloses an electrical connection 6 connected to the housing 2.

[0034] The housing 2 is at least partially surrounded laterally by an outer housing 7, wherein the outer housing 7 has a thread 8 on an outer side, so that the outer housing 7 is designed as a threaded housing. The outer housing 7 can be made of metal, a metal alloy, or plastic. The thread 8 allows the proximity sensor 1 to be easily and quickly mounted in a device in which the measurement with the proximity sensor 1 is to take place. Such a device is described in Fig. 1 not shown for clarity.

[0035] The housing 2 with its front section 3 consists of at least one layer containing a deformable material. Thus, the housing 2 can also consist of a layer system consisting of several individual layers. Furthermore, in addition to the front section 3 and the side wall of the housing 2, an end cap (in Fig. 1 not visible) consist of at least one layer of deformable material. This deformable material can return to its original shape after deformation. It is advantageous if this deformable material has a minimum deformability of at least 2% and a hardness in the range of 10 Shore D to 100 Shore D.

[0036] In the following, a side wall is understood to mean a lateral wall of the housing, so that one side wall can also include several side walls if, for example, the housing is square; in this case, the side wall would have four side walls.

[0037] In Fig. Figure 1 also shows a section of an impact weight 9. An impact test is performed using this impact weight 9. If an impact test is performed according to EN 60079-0 or IEC 60079-0, the impact is applied with an energy of 6.867 joules (= ~7 joules in common parlance). However, the impact can also be applied with a reduced energy of 3.924 joules (= ~4 joules in common parlance) and an X marking. An X marking means that, according to the operating instructions for the proximity sensor, special conditions must be observed – particularly during installation and operation.

[0038] If the proximity sensor 1 is subjected to an impact test, the impact weight 9 is moved with a specific force or energy onto the front side 4, i.e., onto the front section 3, as indicated by the arrow 10. The impact exerts a force on the front section 3, which absorbs the energy of the impact by deforming. This front section 3 consists of at least one layer containing a deformable material. Since the side wall (not visible) of the housing 2 also contains this deformable material, the side wall can also deform.

[0039] Since at least the front section 3 of the housing 2 deforms due to the impact, the deformation, ie the deformation energy, can be transferred to a compressible element by the layer moving into the compressible element. This compressible element is located as a filling material in an interior space (not visible) of the housing 2. The filling material can be, for example, a resin or a fluid. This compressible element present as a filling material is in the Fig. 1 cannot be seen because it is surrounded by the housing 2.

[0040] The tensile strength of the deformable material of the housing 2 prevents the housing 2 from being damaged, for example, by breaking or cracking. Because the material's elongation at break is sufficiently large, the material cannot be damaged by impact, thus preventing the creation of an ignition source. Therefore, the proximity sensor 1 may lose its function, but it may not create an ignition source, for example, due to cracks.

[0041] Fig. 2 shows a longitudinal section through the Fig. 1, wherein the impact weight is not shown. The housing 2 is cylindrical and comprises two essentially cup-shaped components 11 and 12. The first component 11 comprises the front section 3, to which a first section 13 of the side wall 14 adjoins. The second component 12 comprises the end cap 15, to which a second section 16 of the side wall 14 adjoins. The two sections 13 and 16 overlap in the central region 17 of the proximity sensor 1 and together form the side wall 14 of the housing 2, so that an interior space 18 is created that is completely electrically insulated from the outer housing 7 and mechanically protected.

[0042] The first and second components 11, 12 have notches 19, 20, which each engage in corresponding grooves 21, 22 of the outer housing 7, whereby the outer housing 7 is firmly arranged on the housing 2. In addition, the housing 2 has sealing beads 23, 24, 25, 26, which seal against the outer housing 7.

[0043] Attached to the rear side 5, opposite the front side 4, is the end cap 15, which encloses the electrical connection 6. The electrical connection 6 coming from the outside is electrically connected to an electronic assembly 27 in the interior 18 of the proximity sensor 1, wherein an electrical sensor element 29 is provided on the electronic assembly 27. This sensor element 29 is located in a shell core 56. The interior 18 is filled with a compressible element so that the electronic assembly 27 is completely surrounded by the compressible element. The sensor element can be, for example, a coil, a capacitive probe, or an ultrasonic coupler, depending on the type of proximity sensor.

[0044] In Fig. 2, the housing 2, which comprises the front section 3 and the side wall 14, as well as the end cap 15, are constructed from at least one layer made of a deformable material. This is advantageous in that even if a lateral impact occurs on the outer housing 7, the outer housing 7 can deform, but the housing 2 is not damaged because it consists of at least one layer of deformable material and can thus convert the impact energy into potential deformation energy.

[0045] In addition to the deformable material, the at least one layer can comprise a fiber system. The fiber system can, for example, surround the deformable material on both sides. Other layer systems are also possible, for example, a layer system consisting of a first fiber layer, a first layer of a deformable material, a second fiber layer, a second layer of a deformable material, and a final third fiber layer, whereby the two layers of deformable material are each surrounded by fiber layers. Suitable materials for such a fiber layer include, for example, polyarylamides, aramids, or even polyethylene.

[0046] It is thus possible to provide a plurality of different layer systems from which the housing 2 and also the end cap 15 can consist and which all contain deformable material, namely at least one layer of deformable material.

[0047] Cast resin or foam resin, for example, are suitable as a resin filler in the interior 18 of the housing 2. A gas, for example, air, or a liquid, for example, water, is suitable as a fluid. If a liquid is present in the interior 18, an outlet (not shown) must be provided on the end cap 15 through which the fluid can escape if the housing 2 deforms due to an impact. The outlet can be designed as a pressure relief valve. If a gas is used as the fluid, no pressure relief valve is required because the gas is compressible.

[0048] When assembling the proximity sensor 1, the first component 11 is first inserted into the outer housing 7 until the component 11 snaps into place in the outer housing 7. Then, the electrical connection 6, designed as a cable, is mounted in the second component 12, and the electrical connection 6 is connected to the electronic assembly 27. Preferably, the electrical connection 6 is glued to the end cap 15 using a silane-modified polymer adhesive. The electronic assembly 27 was calibrated in a reference housing (not shown) before installation. A filling compound, preferably a resin in this exemplary embodiment, is then introduced into the first component 11, and then the second component 12, with the electronic assembly 27 attached to it, is pushed into the outer housing 7 until it snaps into place in the outer housing 7.Additional resin is introduced into the thus completed housing 2 through a vent opening (not shown) located on the end cap 15 until the interior space 18 is completely filled with resin. After the resin has expanded to the vent opening, it is cured, and any resin that has leaked out is removed.

[0049] In Fig. 3 is a side view of a first variant 30 of the Fig. 1. This proximity sensor 30 also has a housing 31, whereby only a front section 32 and an end cap 33 can be seen. The housing 31 comprises at least one layer of deformable material, wherein the deformable material of the housing has a minimum deformability of at least 2% and a hardness in the range of 10 Shore D to 100 Shore D. This at least one layer of deformable material can be additionally reinforced by a fiber system. The housing 31 can - as in Fig. 3 - be cylindrical in shape. The front section 32 is attached to a front side 34 of the housing 31, whereby the front side 34 of the housing 31 also forms the front side 34 of the proximity sensor 30. The end cap 33, which at least partially encloses an electrical connection 53, is provided on a rear side 35 of the housing 2. The electrical connection 53 is in turn electrically connected to an electronic module (not visible) located in the housing 2.

[0050] The housing 30 is at least partially surrounded in the longitudinal direction by an outer housing 36, which has a thread 37, thus forming a threaded housing. The outer housing 36 is made of metal, a metal alloy, or plastic.

[0051] In Fig. Figure 4 shows a longitudinal section through the proximity sensor 30. The proximity sensor 30 has a housing 31 with a side wall 44, to whose front side 34 the front section 32 is attached. The front section 32 can also be designed as a removable cover.

[0052] The end cap 33, which encloses the electrical connection 53, is attached to the rear side 35, opposite the front side 34. The electrical connection 53 coming from the outside is electrically connected to the electronic assembly 39 in an interior space 38 of the proximity sensor 30. An electrical sensor element 41, which is located in a shell core 55, is arranged on the electronic assembly 39. The interior space 38 is filled with a filling compound. This filling compound is a compressible element and completely surrounds the electronic assembly 39. A vent plug 42, which is surrounded by the housing 31, is arranged on the rear side 35. Between the vent plug 42 and the housing 31, a vent opening 43 is arranged, which is also filled with filling compound and has several ventilation channels (not visible). Preferably, the vent plug 42 also consists of at least one layer made of a deformable material.However, the vent plug 42 can also consist of a layer system comprising several individual layers of deformable material. This at least one layer of the vent plug 42 can also be reinforced by a fiber system.

[0053] On an outer side 54 of the side wall 44 of the housing 31, a plurality of grooves 45, 46, 47 are provided, which form expansion spaces 45, 46, 47. These expansion spaces 45, 46, 47 are formed circumferentially in the transverse direction, whereby the expansion spaces 45, 46, 47 form rings that surround the housing 31. These expansion spaces 45, 46, 47 are thus arranged between the side wall 44 of the housing 31 and an inner side 48 of the outer housing 36. If the volume of the compressible element (i.e., the filling compound) located in the interior 38 of the housing 31 changes due to temperature changes, these expansion spaces 45, 46, 47 serve to absorb volume changes over the entire application temperature range.

[0054] The housing 31 consists of at least one layer of deformable material, for example, a thermoplastic elastomer, whereas the outer housing 36 consists of a rigid material, for example, a metal, a metal alloy, or plastic. For example, the outer housing 36 can be made of steel. Preferably, the housing 31 is permanently elastically bonded to the outer housing 36. The electrical connection 53 is also permanently elastically bonded to the end cap 33, and the vent plug 42 is also permanently elastically bonded to the electrical connection 53. The deformable material has a sufficiently high rigidity (elastic modulus) and preferably also has a high elongation at break.

[0055] Particularly suitable for the housing 31 are materials that are easily deformable and at the same time exhibit high extensibility, for example materials made of a cross-linked elastomer (e.g., FKM (fluororubber), HNBR (acrylonitrile butadiene rubber), or EPDM (ethylene propylene diene rubber)) or a thermoplastic elastomer (such as TPE-E, TPE-O, TPE-A, TPE-U), or a post-cross-linked thermoplastic elastomer (such as TPE-V). In general, however, it is also possible to use steels, provided they exhibit good extensibility, such as metallic materials with a face-centered cubic crystal structure (e.g., chromium-nickel steels, chromium-nickel-molybdenum steels, or chromium-manganese-molybdenum steels). These easily formable materials have a minimum formability of at least 2% and a hardness in the range of 10 Shore D to 100 Shore D.

[0056] If a force is applied to the front section 32 during the impact test, the housing 31, or at least the front section 32, is deformed. This deformation energy is transferred to the compressible element present as a filling material located in the interior space 38, so that this compressible element also deforms.

[0057] A resin, such as casting resin or foam resin, or a fluid, is suitable as a filler material. A gas, such as air, or a liquid, such as water, is suitable as a fluid. If a liquid is present in the interior space 38, an outlet (not shown) must be provided on the vent plug 42 through which the fluid can escape if the housing 31 deforms due to an impact and transfers impact energy to the filler material. The outlet can be designed as a pressure relief valve. If a gas is used as the fluid, no pressure relief valve is required because the gas is compressible.

[0058] Fig. Figure 5 shows an exploded view of the proximity sensor 31. The electrical connection 53 is surrounded by the end cap 33 on the rear side 35 and extends through the vent plug 42 to finally connect to the electronic assembly 39. The vent plug 42 has a plurality of ventilation channels running in the longitudinal direction B, of which only the ventilation channels 49, 50, 51, 52 are provided with reference numbers. The housing 31 has a plurality of grooves 45, 46, 47 that form the corresponding expansion spaces 45, 46, 47. The front section 32 is attached to the front side 34 of the housing 31. The expansion spaces 45, 46, 47 are preferably filled with a fluid, for example, air. However, it is also possible to provide a vacuum or a strong negative pressure in the expansion spaces 45, 46, 47.

[0059] The outer housing 36 surrounding the housing 31 has a thread 37 on its outer side and is thus designed as a threaded tube. Via this thread 37, the proximity sensor 30 can be attached to a device or in a device. Such a device, in which the measurement with the proximity sensor 1 is to take place, is shown in Fig. 5 is not shown. It is understood that the outer housing 36 does not need to have a thread and can also be attached to a device in another way, for example via a plug connection.

[0060] For the sake of clarity, the filling material is Fig. 5 not shown.

[0061] When assembling the proximity sensor 1, the housing 31 is first installed into the outer housing 36. Then, the filling compound, for example a resin, such as cast resin or foam resin, is introduced into the housing 31. It is also possible to use preformed foam components as the filling compound. The electronic assembly 39 is then inserted into the outer housing 36, wherein the electronic assembly 39 has previously been calibrated in a reference housing (not shown). Subsequently, the housing 31 is closed with the vent plug 42 and the vent plug 42 is glued to the electrical connection 53 using a permanently elastic adhesive, for example a silane-modified polymer adhesive. After the resin has expanded up to the vent plug 42, it is cured and any escaping resin is removed. Finally, the end cap 33 is applied and fixed to the housing 31 using the permanently elastic adhesive.

[0062] It is important that the filler (e.g., a resin or fluid) introduced into the interior has a minimum deformability of at least 2%. Materials with a hardness in the range of 10 Shore D to 100 Shore D are particularly suitable. In addition to the minimum requirement of good extensibility, such materials also exhibit sufficiently high material stiffness (elastic modulus and shear modulus) so that the filler can convert impact energy into deformation energy.

[0063] Fig. Figure 6 shows a longitudinal section through a second variant of a proximity sensor 60. This proximity sensor 60 has a housing 61 with a side wall 62, with a front section 64 arranged on a front side 63 of the proximity sensor 60. This front section 64 can also be designed as a removable cover, which, however, is not the case with this variant. The housing, with its side wall 62, its front side 63, and its front section 64, has a high elongation at break and is therefore deformable and crack-resistant. This housing consists of at least one layer of a material with a minimum deformability of at least 2% and a hardness in the range of 10 Shore D to 100 Shore D.

[0064] Attached to the rear side 65, opposite the front side 63, is an end cap 66 that encloses an electrical connection 67. The end cap 66 also has a high elongation at break. The electrical connection 67 coming from the outside is designed as a cable and is electrically connected to an electronic assembly 69 in an interior space 68 of the proximity sensor 60. The electronic assembly 69 is a populated printed circuit board and is electrically connected to an electrical sensor element 70, wherein the electrical sensor element 70 is arranged in a shell core 71. The interior space 68 is filled with a filling compound. A compressible element, such as a resin (e.g., cast resin or foam resin) or a preformed foam component, is used as the filling compound, so that the electronic assembly 69 is completely surrounded by this filling compound.The filling material has a high elongation at break and a high stiffness, which makes the filling material easily compressible and easily deformable.

[0065] It is also possible to fill the interior space 68 with a fluid instead of resin. A suitable fluid can be a gas, such as air, or a liquid, such as water. If the interior space 68 contains a liquid, a vent plug with an outlet (not shown) must be provided (as is the case in the second variant 30) so that the fluid can escape if the housing 61 deforms due to an impact. The outlet can be designed as a pressure relief valve. If a gas is used as the fluid, no pressure relief valve is required because the gas is compressible.

[0066] On an outer side 72 of the side wall 62 of the housing 61, a plurality of grooves 73, 74, 75 are provided, forming expansion spaces 73, 74, 75. These expansion spaces 73, 74, 75 are formed circumferentially in the transverse direction, whereby the expansion spaces 73, 74, 75 form rings surrounding the housing 61. A compressible element, preferably a fluid such as air, is located within these expansion spaces 73, 74, 75. Thus, these expansion spaces 73, 74, 75 can also absorb impact energy by converting this impact energy into potential deformation energy.

[0067] These expansion spaces 73, 74, 75 are arranged between the side wall 62 of the housing 61 and an inner side 76 of an outer housing 77. This outer housing 77 consists of a plastic, a metal, or a metal alloy and at least partially surrounds the side wall 62 of the housing 61. Preferably, the side wall 62 of the housing 61 is permanently elastically bonded to the outer housing 77. The outer housing 77 has a thread 85 on an outer side 86, via which the proximity sensor 60 can be attached to a device or in a device. This device can be, for example, an industrial plant that is located in Fig. 6 is not shown.

[0068] If the volume of the compressible element present as a filling compound, which is located in the interior 68 of the housing 61, changes due to temperature changes, these expansion spaces 73, 74, 75 serve to absorb volume changes across the entire application temperature range. The expansion spaces 73, 74, 75, which are designed as transverse annular grooves, enable axial displacement upon axial loading and radial deformation upon radial loading on the outer housing 77, because the force of the load is directed into webs 82 to 84 of the expansion spaces 73, 74, 75, whereby the webs 82 to 84 can be deformed into the expansion spaces 73, 74, 75 filled with the compressible medium (e.g., air).

[0069] For improved impact resistance, an additional protective sheath 78 is located in the interior 68. This protective sheath 78 is again made of a material with high elongation at break and preferably high rigidity, whereby the protective sheath 78 forms an internal deformable spring element. This protective sheath 78 is connected to an inner side of the housing 61 by means of a flexible adhesive. The protective sheath 78 additionally promotes a deformation of the proximity sensor 60 on the front 63. If an impact is exerted on the front 63 of the proximity sensor 60, the front deforms in the direction of the interior 68. As a result, the energy of the impact is also transferred to the protective sheath 78, causing the protective sheath 78 to deform, i.e. the protective sheath 78 converts the impact energy into potential deformation energy.

[0070] The component strengths of the protective sheath 78, as well as the housing 61 and the end cap 66, must be greater than the respective mechanical forces or mechanical stresses acting on them. This means that the minimum material strength of the corresponding components must be greater than the mechanical stresses occurring in the respective component during the impact test, and that the distortions occurring in the components due to component deformation must be smaller than the respective material deformation limits (elongation at break and shear at break).

[0071] Materials that are easily deformable and highly extensible are particularly suitable for the housing 61 with its front section 64, the end cap 66, and the protective cover 78. Suitable materials include cross-linked elastomers (e.g., FKM (fluororubber), HNBR (acrylonitrile butadiene rubber), or EPDM (ethylene propylene diene rubber)), thermoplastic elastomers (such as TPE-E, TPE-O, TPE-A, TPE-U), or post-cross-linked thermoplastic elastomers (such as TPE-V). However, it is generally also possible to use steels, provided they exhibit high extensibility, such as chromium-nickel steels, chromium-nickel-molybdenum steels, or chromium-manganese-molybdenum steels.

[0072] However, materials from other material classes can also be used, as long as they have sufficiently high impact resistance.

[0073] To prevent damage to the electronic assembly 69 if an impact is applied to the front panel 63, particularly to the front section 64, the electronic assembly 69 is designed to be resilient. For this purpose, the electronic assembly 69 has several cantilever spring regions 79 to 81.

[0074] If a force is exerted on the front area 63 during the impact test, the housing 61, or at least the front section 64 of the housing 61, is deformed. This deformation energy is transferred not only to the protective cover 78, which is designed as a deformable spring element, but also to the filling compound, which is also located in the interior space 68. In this case, the front section 64 can deform into the filling compound. The filling compound therefore preferably has a minimum deformability of at least 2% and a hardness in the range of 10 Shore D to 100 Shore D.

[0075] In Fig. Figure 7 shows a fourth variant of a proximity sensor 100. This proximity sensor 100 has a housing 101 with a front section 112, wherein the housing 101 is arranged on a base plate 102. The base plate 102 is arranged opposite the front section 112. The base plate 102 is attached to a device 106 via connecting elements 103, 104, 105, for example, screws, wherein only a wall section 107 of the device 106 is shown in detail. The device 106 can be, for example, an industrial system.

[0076] Fig. 8 shows a section through the Fig. 7. The proximity sensor 100 has a base 110, which is completely surrounded laterally by the housing 101, whereby the proximity sensor 100 has an interior space 108. This interior space 108 is filled with filling compound 109, which completely surrounds an electronic assembly, wherein the electronic assembly is also connected to an electrical connection and an electrical sensor element located in a shell core, as is the case, for example, with the proximity sensor 60. However, this is in Fig. 8 is not visible. The filling compound preferably has a minimum deformability of at least 2% and a hardness in the range of 10 Shore D to 100 Shore D.

[0077] Such materials, which have a minimum deformability of at least 2% and a hardness in the range of 10 Shore D to 100 Shore D, are also used for the housing 101 and the base plate 102. These materials are easily deformable and, at the same time, exhibit high extensibility, such as materials made of a cross-linked elastomer (for example, FKM (fluororubber), HNBR (acrylonitrile butadiene rubber), or EPDM (ethylene propylene diene rubber)) or a thermoplastic elastomer (such as TPE-E, TPE-O, TPE-A, TPE-U) or a post-cross-linked thermoplastic elastomer (such as TPE-V).

[0078] In general, however, it is also possible to use steels as long as they are highly ductile, such as chromium-nickel steels, chromium-nickel-molybdenum steels or chromium-manganese-molybdenum steels.

[0079] A material with a high elongation at break and sufficiently high rigidity, thus allowing for good deformation, is used for both the housing 101 and the base plate 102. This allows both the housing 101 and the base plate 102 to deform when an impact is applied to the housing 101 of the proximity sensor 100. The base 110, however, can be made of a material that does not have to be deformable. As with the housings of the other variants, the housing 101 and the base plate 102 can consist of at least one layer of deformable material, which layer can also be reinforced by a fiber system.

[0080] The housing 101 is connected to an upper portion 114 of the base plate 102 via an extended side portion 113. A sealing element 111 (for example, an O-ring or an injected foam seal) is provided between the side portion 113 and the upper portion 114 of the base plate 102, sealing a gap between the upper portion 114 and the side portion 113 against the ambient air (or another gas) located in the external area 115. The side portion 113 is bonded to the upper portion 114 by means of an adhesive, or the side portion 113 is held to the upper portion 114 via the sealing element 111 by adhesion.

[0081] A circumferential gap 116 is provided between the upper section 114 and a lower section 117 of the base plate 102, in which a compressible medium, for example, air, an inert gas, or a foam material (e.g., PUR flexible foam, PP-E, PS-E), is located. Due to the compressible medium located in the gap 116, the gap 116 forms an additional spring element that cushions the impact.

[0082] Fig. 9 shows an enlarged section of the Fig. 8 consisting of the proximity sensor 100, the base plate 102 and the device 106. It can be clearly seen that between the upper section 114 of the base plate 102 and the extended side section 113 of the housing 101 there is a gap (without reference number) in which the sealing element 111 is arranged, whereby the interior 108 of the proximity sensor 100 is sealed (for example against the ambient air).

[0083] The Fig. The circumferential gap 116 already shown in Figure 8 is filled with a compressible medium (for example, air or inert gas) and is located between the upper section 114 and the lower section 117 of the base plate 102. This section 114, in which the compressible medium is located, forms a bending beam spring region, the deformability of which is made possible by the compressible medium located in the gap 116.

[0084] In Fig. 10 shows a fifth variant of a proximity sensor 120. This variant differs from the ones shown in the Fig. 7 to 9 only by an additional protective element 121, which is why the reference numbers have been essentially retained. The protective element 121 is part of the housing 101, wherein the protective element 121 at least partially surrounds a side wall 124 of the housing 101 of the proximity sensor 120. In Fig. 10, only two side walls 122, 123 of the side wall 124 are visible. The housing 101 and the protective element 121 consist of at least one layer of a flexible material, whereby the at least one layer can also be reinforced by a fiber system.

[0085] The protective element 121 is designed as a protective wall, with the protective element 121 being connected at a first end 118 to the side wall 124 and at a second end 119 to the lower section 117 of the base plate 102. The protective element 121 creates a space 126 filled with a compressible medium, for example, air or an inert gas. This space 126 is formed by the circumferential gap 116 and a main space 125.

[0086] The advantage of this variant is that the protective element 121, which at least partially surrounds the side wall 124 of the proximity sensor 120, prevents particles, such as dust, from entering the gap 116, and the gap 116 filled with the compressible fluid (a gaseous medium) remains intact as a spring element. The gap 116 thus fulfills the same function as the expansion spaces 73, 74, 75 of variant 60.

[0087] In Fig. Figure 11 shows an enlarged section of one side of the proximity sensor 120. The housing 101 is connected to the upper portion 114 of the base plate 102 by the extended side portion 113, with the sealing element 111 arranged in the gap therebetween. This sealing element 111 prevents the gaseous medium from passing from the space 126 into the interior 108 of the proximity sensor 120.

[0088] The protective element 121 is part of the housing 101 and surrounds the side wall 124 of the proximity sensor 120 at least partially and can - as shown in the Fig. 11 - also completely surrounds the side wall 124. This protective element 121 is connected to the base plate 102 by means of connecting elements or by means of an adhesive, which, however, Fig. 11 is not shown in detail.

[0089] The protective element 121 prevents incompressible material, such as dust or sand, from entering the gap 116 and thus impairing the resilient properties of this gap 116. This allows the proximity sensor 120 to be used even in heavily soiled or dusty areas. List of reference symbols 1 proximity sensor 2 housings 3 Front section 4 Front 5 Back 6 Electrical connection 7 Outer casing 8 threads 9 Impact weight 10 Arrow 11, 12 components 13 First Section 14 Side wall 15 End cap 16 Second Section 17 Middle area 18 Interior 19, 20 notches 21, 22 grooves 23 to 26 sealing beads 27 Electronic assembly 29 Electrical sensor element 30 Proximity sensor 31 housings 32 front section 33 End cap 34 Front 35 Back 36 outer casings 37 threads 38 Interior 39 Electronic assembly 41 Electrical sensor element 42 vent plugs 43 Ventilation opening 44 side wall 45 to 47 expansion spaces 48 Inside 49 to 52 ventilation ducts 53 Electrical connection 54 Outside 55 shell core 56 shell core 60 Proximity sensor 61 housings 62 side wall 63 Front 64 front section 65 Back 66 End cap 67 Electrical connection 68 Interior 69 Electronic assembly 70 Electrical sensor element 71 shell core 72 Outside 73 to 75 expansion spaces 76 Inside 77 outer casing 78 protective cover 79 to 81 bending beam spring ranges 82 to 84 bridges 85 threads 86 Outside 100 proximity sensor 101 housings 102 base plate 103 to 105 Fasteners 106 Device 107 wall section 108 Interior 109 Filling compound 110 Floor 111 Sealing element 112 front section 113 page section 114 Upper Section 115 Outdoor area 116 gap 117 Lower Section 118 First End 119 Second Ending 120 Proximity sensor 121 protective element 122, 123 side walls 124 side wall 125 Main Room 126 Room

Claims

[1] Proximity sensor (1, 30, 60, 100, 120) comprising a housing (2, 31, 61, 101) having an interior space (18, 38, 68, 108) in which an electronic assembly (27, 39, 69) and an electrical sensor element (29, 41, 70) arranged thereon are located, wherein the housing (2, 31, 61, 101) comprises a side wall (14, 44, 62, 124) and a front section (3, 32, 64, 112), wherein the housing (2, 31, 61, 101) has at least one layer of deformable material, characterized by that the housing (31, 61) has circumferential grooves (45, 46, 47, 73, 74, 75) on an outer side (54, 72) of the side wall (44, 62), which form expansion spaces (45, 46, 47, 73, 74, 75) in which a fluid is located or a vacuum or a strong negative pressure prevails. [2] Proximity sensor (1, 30, 60) according to claim 1, characterized bythat an end cap (15, 33, 66) is arranged on the housing (2, 31, 61) and is opposite the front section (3, 32), the end cap (15, 33, 66) containing at least one layer of deformable material. [3] Proximity sensor (1, 30, 60, 100, 120) according to claim 1 or 2, characterized by that the deformable material is a cross-linked elastomer, a thermoplastic elastomer, a post-cross-linked thermoplastic elastomer or a metallic material with a face-centered cubic crystal structure. [4] Proximity sensor (1, 30, 60) according to claim 1, characterized by that the side wall (14, 44, 62) of the housing (2, 31, 61) is at least partially surrounded by an outer housing (7, 36, 77). [5] Proximity sensor (1, 30, 60) according to claim 4, characterized by that the outer housing (7, 36, 77) comprises a thread (8, 37, 85) on an outer side. [6] Proximity sensor (1, 30, 60) according to claim 4, characterized by that the outer housing (7, 36, 77) is made of metal, a metal alloy or plastic. [7] Proximity sensor (1, 30, 60, 100, 120) according to claim 1, characterized by that a filling compound is arranged in the interior (18, 38, 68, 108) of the housing (2, 31, 61, 101). [8] Proximity sensor (1, 30, 60, 100, 120) according to claim 1, characterized by that the housing (2, 31, 61, 101) has a fiber system which reinforces the at least one layer of deformable material. [9] Proximity sensor (60) according to claim 7, characterized bythat an additional protective sheath (78) made of a deformable material is arranged in the interior (68) of the housing (61), wherein the protective sheath (78) is connected to an inner side of the housing (61) by means of a flexible adhesive and wherein the deformable material is a cross-linked elastomer, a thermoplastic elastomer, a post-cross-linked thermoplastic elastomer or a metallic material with a cubic face-centered crystal structure. [10] Proximity sensor (100, 120) according to claim 1, characterized by that the housing (101) of the proximity sensor (100, 120) is arranged on a base plate (102). [11] Proximity sensor (100, 120) according to claim 1, characterized by that the proximity sensor (100, 120) has a base (110) which is completely surrounded laterally by the housing (101), whereby the interior (108) is enclosed by the housing (101) and the base (110). [12] Proximity sensor (100, 120) according to claim 10, characterized by that the base plate (102) has a lower section (117) and an upper section (114), wherein a circumferential gap (116) runs between the upper section (114) and the lower section (117), wherein a compressible medium is located in the gap (116). [13] Proximity sensor (120) according to claim 12, characterized by that a protective element (121) is provided, wherein the protective element (121) is connected with a first end (118) to the side wall (124) of the housing (101) and with a second end (119) to the lower section (117) of the base plate (102).

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