Photoelectric sensor having a welded connection between the housing and the optical module

Abstract

A photoelectric sensor, particularly a light curtain, is shown, comprising an elongated housing and an optical module disposed within the housing. The light-transmitting and / or light-receiving elements are disposed on the optical module at a distance from each other, and the optical module is connected to the housing via flat contact points. The optical module and the housing are made of plastic. At least some of the contact points are designed as fused connections, where the housing and the optical module are welded together.

Description

[Technical Field]

[0001] The present invention relates to a photoelectric sensor according to the general part of claim 1 and to a method for manufacturing a photoelectric sensor according to claim 28. [Background technology]

[0002] State-of-the-art photoelectric sensors typically have an aluminum profile within which at least one optical module is placed. The optical module includes components that ensure the functionality of the photoelectric sensor. In addition to the light-transmitting and / or light-receiving elements on the printed circuit board, a support body for the printed circuit board, also known as a tube, is usually part of the optical module. Depending on the design, the optical module may further include an aperture assembly and a lens assembly, which are preferably attached to the support body. The aluminum profile has one or more openings along one longitudinal side. The optical module is placed within the aluminum profile so that the light-transmitting or light-receiving elements of the optical module are oriented toward the longitudinal side with the opening. A plastic strip is provided to be attached to the aluminum profile as a protective shield, which is transparent to the wavelengths emitted by the optical module. The protective shield can be permanently or detachably attached to the aluminum profile. However, the connection obtained from two different materials creates a mechanical weakness and requires an additional step in the fabrication of the photoelectric sensor. At the same time, the connection must provide a good seal so that the optical module is protected from splashes.

[0003] The optical module is placed in the aluminum profile using guides inside the profile that run in the longitudinal direction of the profile. Counterpart elements of the optical module can be inserted into these guides, resulting in a form-fit and / or force-fit connection between the optical module and the aluminum profile. For this type of connection, a decision must be made as to whether ease of assembly or high vibration and shock resistance is to be prioritized. However, the two requirements are contradictory.

[0004] Instead of an aluminum profile, the profile can also be made from a different material, such as plastic, and since the method of making the connection with the optical module is the same for a plastic profile as for an aluminum profile, it presents the same problems as for an aluminum profile regarding the stability of this connection against vibrations and shock movements.

[0005] US Patent Application Publication No. 2013 / 292554 shows a light curtain with an optical module, which is designed to be inexpensive to manufacture and easy to set up. The optical module is designed to be assembled into a U-shaped profile. The optical module has protruding elements that are used to accurately position the optical module in the housing. Furthermore, the optical module may have fasteners that are used to fasten the optical module into the housing. The fasteners are preferably designed as snap-in elements. The fasteners can be firmly attached to the housing. Adhesive bonding, ultrasonic welding, or screw fastening can be used for this purpose.

[0006] EP 1 770 414 A1 describes an optoelectronic device having multiple light emitter or receiver modules, which are electrically connected to one another by a flexible printed circuit board and associated with a tube or lens body. The light emitter or receiver modules are attached directly to the tube or lens body to which they are assigned, and flexible light guides are fastened directly to the light emitter or receiver modules. A plastic housing is provided to accommodate the light emitter or receiver modules, which are attached to the tube using snap-fit ​​elements. Furthermore, the light emitter or receiver modules can be connected to the respective tube or lens body by a fusion connection. The tube can be assembled in the housing, which for this purpose can have grooves through which the tube can be fixed.

[0007] The assembly of individual housing modules to construct light curtains with various protective area heights from a uniform, short base module is known from EP 2 730 952 A1. A disadvantage of this variant is that each connection point includes an electrical transition that must be sealed against environmental influences. Furthermore, the mechanical stability of the connections is limited, since only a small number of housing modules can be assembled, limiting the maximum protective area height of a light curtain constructed in this way.

[0008] It is known from US Patent Application Publication No. 2014 / 346318 that a printed circuit board with spacers can be aligned with the pinhole aperture of the tube so that the axis of the optoelectronic component (LED / lens) exactly coincides with the axis of the pinhole aperture of the tube. In this case, the printed circuit board can be fixed in place by a laser welded connection between the spacer element and the tube. The disadvantage of this variant is that for each light beam in the light curtain, an optoelectronic component must be aligned with the corresponding pinhole aperture and fixed in place by laser welding. This requires considerable time and expense. Furthermore, each light beam requires two distance elements, which are necessary for the laser welded connection. This also leads to high manufacturing costs. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] US Patent Application Publication No. 2013 / 292554 [Patent Document 2] European Patent Application Publication No. 1770414 [Patent Document 3] European Patent Application Publication No. 2730952 [Patent Document 4] US Patent Application Publication No. 2014 / 346318 Summary of the Invention [Problem to be solved by the invention]

[0010] It is therefore an object of the present invention to propose an alternative photoelectric sensor, in particular a light curtain, which involves a simple and cost-effective way of connecting the optical module to the housing, which has increased vibration and shock resistance, and which can be produced with minimal mechanical stress on the optical module and the housing. Furthermore, the sealing of the housing should be as effective as possible. [Means for solving the problem]

[0011] This problem is solved by a photoelectric sensor having the features of claim 1.

[0012] The photoelectric sensor, in particular the light curtain, comprises an elongated housing and an optical module arranged in the housing. The light-transmitting and / or light-receiving elements are arranged on the optical module at a distance from each other, and the optical module is connected to the housing via contact points, which are flat. The optical module and the housing are made of plastic. At least some of the contact points are designed as fused connections, and the housing is welded to the optical module. The fused connections between the housing and the optical module are formed by laser back-strip welding.

[0013] The housing protects the optical module of the photoelectric sensor from external influences and acts as a stabilizing element. The welded connection creates a rigid connection between the housing and the optical module inside the housing. The advantage is that the optical module is first positioned by inserting it into the housing and then rigidly connected to the housing in a second step.

[0014] This not only simplifies the assembly process, but also provides a rigid connection between the two components of the photoelectric sensor, significantly increasing the vibration and shock resistance of the photoelectric sensor.

[0015] The housing may be described as the housing of the device because the housing is used to house the optical module such that the optical module is fully enclosed by the housing. Thus, it is intended that the optical module is fully enclosed by the housing in the circumferential direction.

[0016] Since the components come into contact at the contact point, an increase in the temperature of one of the two components causes the other component to heat up as well. In this process, the temperature of the material at the point of irradiation increases up to the melting temperature of the material. Thus, the material of both components melts at the point of irradiation contact and, after cooling, a permanent joint is formed. In this case, the process is called laser transmission welding.

[0017] Compared to ultrasonic welding methods, laser uranami welding has the advantage that energy can be applied to the welding point without contact. Irradiating the contact point from the outside with a laser beam is sufficient to create a strong welded joint. For comparison, in ultrasonic welding methods, a sonotrode designed for this purpose is used to generate ultrasonic waves that come into contact with the components to be welded. The components to be welded, i.e., the joining partners, are therefore subjected to high joining forces during the welding process. In contrast, in laser transmission welding, the energy that creates the connection between the components or that welds both components together is introduced without contact.

[0018] The advantage of a contactless connection is that no external pressure is applied to the joint. This allows welding of contact points that may not be able to absorb the joining force of the ultrasonic welding sonotrode or that are located within a closed system. Furthermore, there is no risk of the parts being joined out of position due to the applied joining force.

[0019] The simple design of the housing and the use of plastic for the main components of the photoelectric sensor keep manufacturing costs low. Plastic acquisition costs are relatively low.

[0020] In a preferred embodiment, the housing is infrared-transparent and the optical module is infrared-absorbing, or the housing is infrared-absorbing and the optical module is infrared-transparent, at least in the region of the contact point. The contact point results from a contact point or contact surface between the housing and the optical module. If one of the two components absorbs infrared light in the region of the contact point, irradiating the contact point with an infrared laser beam will result in a local temperature increase. During the manufacturing process, this irradiation proceeds at such a distance that the plastic material melts at the point of irradiation.

[0021] Advantageously, the contact points of the optical module and the housing each comprise compatible plastics, in particular thermoplastic materials, even more preferably polycarbonate. In the context of the present invention, "compatible" means that the plastics can be joined together by laser welding. By melting the plastic materials of the two components, a particularly resistant welded connection can be produced. If the same plastic material is used, the optical module and the housing will experience the same thermal expansion during the welding process and during subsequent operation due to the same thermal expansion coefficient, so that stresses due to thermal expansion will not occur at the weld points.

[0022] In a further preferred embodiment, the plastic material of at least one of the two components at the intended contact point between the optical module and the housing is mixed with an infrared absorbing additive. The infrared absorbing material is evenly dispersed throughout the plastic. Mixing the plastic with such an additive eliminates the need for an additional step after manufacturing the component, since the additive is already incorporated into the plastic at the contact point.

[0023] In another preferred embodiment, the optical module comprises a support body, and the printed circuit board with the light transmitting and receiving elements is arranged on the support body. The light transmitting and receiving elements are therefore arranged on the printed circuit board as a component of the optical module, together with the support body, which is tasked, inter alia, with holding the printed circuit board. The printed circuit board can be connected to the support body in a form-fitting or press-fit manner. It is also possible to envisage the printed circuit board being arranged on several support bodies.

[0024] The support body and the housing are advantageously made from compatible thermoplastic materials. A welded connection can therefore be made between the housing and the support body. In this design, the support body is part of the optical module made from a thermoplastic material that is compatible with the housing. The welded connection between the housing and the support body allows the use of a modular optical module design. Other assemblies that may be included as components of the optical module may have other functions without having to meet the requirement of being made from compatible plastics.

[0025] Such further assemblies may include, among others, lens assemblies or aperture assemblies. Preferably, the lens and / or aperture assembly is provided on the support body opposite the light-transmitting or light-receiving element. The lens assembly comprises, among others, a plurality of lenses, the function of which is to disperse or concentrate the incoming or outgoing beam. The aperture assembly is used to limit the amount of light transmitted by the light-transmitting element or received by the light-receiving element. The aperture assembly ensures the resolution of the safety light curtain. The resolution of the safety light curtain determines the size of the smallest object that can be detected. Since the optical module may comprise an aperture assembly and a lens assembly, the welded connection between the optical module and the housing may also be made through the aperture assembly and / or lens assembly.

[0026] It is possible to connect two support bodies that meet at the front via a lens assembly or an aperture assembly, for example, the aperture assembly may have alignment lugs on the side facing the support bodies, which may be inserted perpendicularly into recesses provided on both support bodies.

[0027] Preferably, at least the support body and housing are made from polycarbonate, which has higher impact strength than alternative plastics such as PMMA.

[0028] Usefully, the light transmitting elements comprise light emitting diodes and the light receiving elements comprise photodiodes. Light emitting diodes and photodiodes are widely available.

[0029] The housing is preferably a cylinder, in particular a circular cylinder, whose end surfaces are annular and whose inner walls are formed by circular cylindrical surfaces, thus allowing for an interference fit that closes the openings at the ends of the circular cylindrical housing.

[0030] The housing preferably has a closed cross section. This means that the housing has no joints or transitions between two components or semi-finished products in the circumferential direction. Alternatively, the lateral surfaces of the housing can be said to be integral. This eliminates the need for sealing elements and increases the stability of the housing.

[0031] The design of the housing with a closed cross section, combined with the creation of a connection between the housing and the optical module by laser uranami welding, provides controlled heat transfer to form the welded connection. Laser uranami welding allows the optical module to be welded to the housing, and a housing closed on all sides is used. Other welding methods, such as ultrasonic welding, require an open housing (U-shaped profile). This is because in ultrasonic welding, energy is transmitted via vibrations, which must tightly clamp the welded components together. Because the optical module cannot be clamped within a closed housing, it vibrates during ultrasonic welding. This prevents controlled heat transfer to form the welded connection between the housing and the optical module. For this reason, creating a welded connection between the housing and the optical module by laser transmission welding cannot simply be replaced by ultrasonic welding. Furthermore, a closed housing eliminates the need for an additional connection point between two housing parts, which would otherwise need to be connected and sealed.

[0032] In a further preferred embodiment, the housing comprises an elongated base body forming a receiving space for the optical module, the base body having at least one opening on a longitudinal side and a protective shield closing this opening. This is an alternative design to the cylindrical housing described above. The optical module can be inserted through an opening on a longitudinal side or through an opening on a longitudinal end. The connection between the elongated base body and the protective shield can both be fixed, i.e., inseparable, or removable. The protective shield is designed to allow the light-emitting and receiving elements of the photoelectric sensor to pass electromagnetic radiation.

[0033] The base body is preferably a U-profile with an opening on one longitudinal side. The U-profile is characterized by a combination of a stable shape, low material cost, and large capacity, making it a good choice for use as a base body for the housing. Furthermore, the U-profile simplifies the assembly of the optical module because the U-profile is open on one longitudinal side.

[0034] The protective shield is advantageously welded to the base body at its edges, preferably by laser transmission welding. The welded connection provides a strong connection between the base body and the protective shield, preferably forming a watertight seal between these components at the edges of the protective shield, meeting IPX5, IPX7, and IPX9K protection ratings. Furthermore, laser transmission welding can help increase the production speed and at the same time reduce manufacturing costs by eliminating the need for additional sealing elements, such as O-rings, glue, adhesive tape, etc.

[0035] In another preferred embodiment, end caps are attached to both open longitudinal ends of the housing, the end caps being used to close the openings at the longitudinal ends.

[0036] The end caps are advantageously made at least partially from infrared-absorbing plastic. Therefore, the end caps can also be connected to the housing or the optical module by laser back-strip welding. As a result, the inside of the housing is splash-proof. The end caps are preferably rigidly attached to the housing and / or the optical module. A material-locking connection creates a robust connection between the end cap and the housing or the optical module. The material joint between the end cap and the housing and / or the optical module is preferably created by laser transmission welding. The end caps are advantageously attached to the housing or the optical module by laser back-strip welding. In the case of laser back-strip welding between the end cap and the housing or the optical module, either the end cap, the housing, or the optical module must absorb infrared rays at least at the contact surface.

[0037] Another advantage is that the laser welding method can also be used to create welded joints around the entire perimeter of the housing, including the front side. Lengths of approximately 2 meters are common for light curtains. With such dimensions, measuring the bond strength of the ultrasonic welded joint through the component is not possible, or is only possible with great effort.

[0038] The end caps close two openings on the sensor housing opposite each other. Preferably, the connection, particularly the welded connection, between the end cap and the housing forms a seal. The end cap can have a ring shoulder that protrudes into the housing, the outer diameter of which corresponds to the inner diameter of the housing. This allows the end cap to be connected to the housing over the entire circumference, creating a welded connection that ensures protection against water droplets. This type of connection has the advantage that no additional seal is required between the housing and the end cap. Therefore, the proposed welded connection prevents moisture ingress, especially when the photoelectric sensor is exposed to various temperatures during use. This type of connection is also suitable for higher ingress protection classes, such as IP69K.

[0039] In another preferred embodiment, two or more optical modules can be connected to each other at the front. This has the advantage that sensor assemblies can be manufactured with different protection zone heights. Thus, the sensor housing can be several times the length of a single optical module.

[0040] Preferably, the light-transmitting and / or light-receiving elements of all optical modules in the housing are oriented in the same radial direction of the cylindrical housing. In the case of light curtains, it is important that all beams of the photoelectric sensors are strictly parallel to ensure that the light curtains can be aligned as closely as possible.

[0041] In another preferred embodiment, the optical module has a first plug-in connection at one longitudinal end and a second plug-in connection at the opposite longitudinal end, the first and second plug-in connections being connectable to one another. It is important that the plug-in connections between the two optical modules ensure accurate mutual alignment with as little play as possible and that the optical modules cannot twist around their longitudinal axes so that the beam axes of the optical modules are aligned parallel.

[0042] Preferably, the first plug-in connection is designed as a plug (male) and the second plug-in connection is designed as a socket (female). A plug-socket connection is a reliable and cost-effective way to link two or more optical modules.

[0043] The end caps preferably have plug-in connections that can be connected to the plug-in connections of the distal optical modules, thereby preventing relative rotation between the optical modules and the adjacent end caps about the longitudinal axis of the housing. The connection between the end caps and the optical modules allows alignment of the optical modules before welding by rotating the connected end caps. The end caps can have alignment markings that define the welding position of the optical modules in the machine holder, for example, or the alignment markings allow a specialist to easily optically determine the exact welding position of the optical modules.

[0044] In another preferred embodiment, the photoelectric sensor comprises an assembly for fastening the photoelectric sensor to the substrate, the assembly being advantageously connected to the housing of the photoelectric sensor by laser back-strip welding, thereby resulting in low manufacturing costs.

[0045] Another aspect of the present invention relates to a photoelectric sensor, particularly a light curtain, having an elongated housing and at least two optical modules disposed within the housing. The photoelectric sensor is characterized in that the optical modules can be connected to each other at their front ends via a plug-in connection, with the optical modules having a plug at a first longitudinal end and a socket at a second end. The plugs and sockets of the optical modules are shaped and positioned so that the plug of the first optical module can be inserted into the socket of the second optical module, preventing relative rotation about the longitudinal axis of the optical modules. This type of plug-in connection between the two optical modules ensures that the optical modules are always aligned in the same way after connection.

[0046] Another aspect of the present invention relates to a method for manufacturing a photoelectric sensor comprising an elongated housing and an optical module, in which the optical module is inserted into the housing, aligned within the housing, and then joined to the housing by laser transmission welding. Light-transmitting and / or receiving elements are disposed on the optical module, and the photoelectric sensor is preferably used to form a light curtain. Ideally, the elongated housing has an opening at at least one longitudinal end through which the optical module can be inserted into the housing. The optical module is aligned within the housing so that the light-transmitting and / or receiving elements on the optical module point in the desired direction. The optical module must contact the housing for laser transmission welding to be used. The contact point between the housing and the optical module serves as the welding point.

[0047] The housing has an opening at at least one longitudinal end. The optical module is preferably inserted through the open longitudinal end of the housing. The use of an open longitudinal end does not require an additional opening in the housing, ensuring greater dimensional stability of the housing.

[0048] The openings at the longitudinal ends of the housing are as small as possible due to their location at the ends of the housing, and form relatively easily closable surfaces. Preferably, the openings at the longitudinal ends of the housing are closed with end caps after inserting the optical module into the housing.

[0049] The end cap should seal the housing to protect the optical module inside from external environmental influences. The end cap can be welded to the housing or optical module, preferably using laser transmission welding. The welded connection between the end cap and the housing forms a seal, eliminating the need for a separate sealing component. This allows the end cap to be connected to the housing or optical module in the same way that the optical module is already connected to the housing, thus simplifying the manufacturing process and reducing costs.

[0050] After inserting the optical module into the housing, it must be ensured that the optical module is centered in the housing. Support arms on the optical module can be used for this purpose. The optical module preferably has support arms that contact the housing when the optical module is inserted into the housing and center the optical module in the housing.

[0051] The invention will now be described in more detail with reference to the drawings, which are in schematic representation and in which: The preferred features mentioned above may be realised in any combination, provided that such features are not mutually exclusive; The drawings are not to scale and are in schematic representation; [Brief explanation of the drawings]

[0052] [Figure 1]1 is a three-dimensional partial view of a first photoelectric sensor according to the present invention, which is composed of a housing and an optical module arranged within the housing. [Figure 2] FIG. 2 is a longitudinal section through the photoelectric sensor of FIG. 1; [Figure 3] FIG. 1 is a perspective view of a first photoelectric sensor, in which the opposing opening of the housing is closed by an end cap. [Figure 4] FIG. 1 is a front view of the first photoelectric sensor with the end cap removed. [Figure 5] FIG. 1 is a perspective view of several optical modules arranged in a row. [Figure 6] FIG. 10 is a perspective view of a second photoelectric sensor having a two-part housing. DETAILED DESCRIPTION OF THE INVENTION

[0053] Hereinafter, the same reference signs (in the various figures) represent the same or functionally identical elements. An additional apostrophe symbol may serve to distinguish between similar or functionally equivalent or functionally similar elements in further embodiments.

[0054] FIG. 1 shows a photoelectric sensor 11 according to the invention. The photoelectric sensor 11 comprises a housing 13 and an optical module 15, on which a printed circuit board 19 with a light source or light sensor is arranged. In the illustrated example, the housing 13 is transparent and formed by a hollow cylinder. The length of the cylindrical housing 13 is several times greater than its diameter. The optical module 15 is placed inside the housing 13. The optical module 15 comprises a support body 17, a lens assembly 21, a printed circuit board 19, and an aperture assembly 22, the lens assembly not being visible in FIG. 1. The lens assembly 21 and the aperture assembly 22 are arranged on the same longitudinal side of the support body, while the printed circuit board 19 is arranged on the opposite longitudinal side of the support body 17. The printed circuit board 19 and the aperture assembly 21 do not come into contact with the housing 13 in the illustrated design. The connection between the optical module 15 and the housing 13 can be provided by a lens assembly 21, an aperture assembly 22 or components specially introduced for this purpose.

[0055] The support body 17 has protrusions 26 on its longitudinal sides 25 that extend to and create contact points with the housing 13. In the embodiment shown, the support body 17 has three contact points 24 per longitudinal side. These contact points 24 act as weld points connecting the support body 17 to the housing 13.

[0056] Support arms 23 are attached to the length of optical module 15 at regular or irregular intervals. The support arms 23 are used to position optical module 15 within housing 13. The support arms 23 project perpendicularly from each longitudinal side 25 so that they contact housing 13. The support arms can also serve as welding points, even if they are not provided for this purpose in the illustrated design. Other functions of support arms 23 are described below.

[0057] FIG. 2 shows a longitudinal section of a partial region of the photoelectric sensor shown in FIG. 1. A hollow cylindrical housing 13 forms the outer boundary of the sensor 11. An optical module 15 is arranged inside the hollow cylindrical housing 13 and comprises, among other things, a support body 17. A printed circuit board 19 is arranged along one side of the support body 17, and a light-transmitting or light-receiving element 29 of the photoelectric sensor 11 is arranged on the support body 17. The beam from the light-transmitting or light-receiving element 29 must pass through the support body 17. For this purpose, a continuous recess 31 is provided in the support body 17 at the level of the light-transmitting or light-receiving element. A lens assembly 21 is arranged at the end of the recess 31 opposite the light-transmitting or light-receiving element 29. The lens assembly 21 is attached to the support body 17 by an aperture assembly 22, which serves as an aperture for the lens assembly 21 and ensures the desired resolution of the light curtain. The aperture assembly 22 has a plate-shaped structure with locating lugs 28 that protrude perpendicularly from one flat side. The support body 17 has recesses that accommodate the locating lugs 28 of the aperture assembly 22. The locating lugs 28 and the recesses in the support body 17 are dimensioned so that when the locating lugs 28 are inserted into the recesses, a frictional connection is created between the support body 17 and the aperture assembly 22. The length of the aperture assembly 22 can differ from the length of the support body 17. Several aperture assemblies 22 can be arranged on one support body 17.

[0058] The hollow cylindrical housing 13 has openings 32 at each of its longitudinal ends. These openings can be closed by end caps 27. In FIG. 2, the openings 32 of the hollow cylindrical housing 13 are closed by the end caps 27. The end caps 27 extend through the openings into the hollow cylinder through a first region 33 that contacts the inside of the housing wall. A second region 34 of the end cap 27, located outside the housing 13, is attached to the longitudinal end of the housing so that the end cap 27 and the housing 13 have an annular contact surface. The contact surface within the first region 33 can serve as a welding point. The cylindrical surface as the contact surface within the first region 33 between the end cap 27 and the housing 13 allows for the use of a laser beam directed perpendicular to the housing 13 for laser welding. On the other hand, the contact surface within the second region 34 requires the use of a laser beam directed at an acute angle to the housing wall for laser welding. By rotating the laser beam source or the housing 13 about its central axis, a continuous welded connection between the housing 13 and the end cap 27 can be created in a single step.

[0059] FIG. 3 shows the photoelectric sensor 11 as a whole. The housing 13 of the photoelectric sensor is cylindrical. The optical module is located inside the housing 13 and is not shown in FIG. 3. End caps 27 are attached to both ends of the cylindrical housing 13. One of the end caps 27' has an opening for a connector 35. The connector 35 forms an interface with another electrical device, allowing information from the photoelectric sensor 11 to be transmitted via the connector 35 to, for example, a control unit attached to the connector 35. At the same time, information from the optical module 15 adjacent to the end cap 27 is transmitted to the connector 35 via the printed circuit board 19. The end caps 27 completely cover the surface of the cylindrical housing 13 at both ends. The part of the end cap 27 that protrudes above the housing 13 is designed as an octagonal nut. Among other things, this allows a better overview of the position of the end cap and the optical module and prevents the light curtain from rolling.

[0060] FIG. 4 is a front view of the photoelectric sensor 11, showing the connector 35 rather than the end cap. The optical module 15 is placed inside the cylindrical housing 13. The optical module 15 contacts the housing 13 via the protrusions 26 on the longitudinal sides 25 and via the support arms 23. In the cross section shown in FIG. 4, there are four contact points between the optical module 15 and the housing 13, and the illustrated design contemplates welding only the optical module's protrusions 26. The support arms 23 are used to position the optical module 15 within the housing 13 until the welded connection is made. The distance between the opposing protrusions 26 is slightly greater than the inner diameter of the housing 13 to provide an interference fit between the optical module 15 and the housing 13. The support arms 23 are approximately perpendicular to the plane formed by the opposing protrusions 26 and, through their contact with the housing, exert a force in an opposing direction. While this force is quite small, it serves to secure the optical module 15 within the housing 13 until the welded connection is made.

[0061] One or several printed circuit boards 19 are held in a conformal manner within the optical module 15. When using two or more printed circuit boards 19, the electrical connection between adjacent printed circuit boards 19 is made via a connecting plug 37. The connecting plug 37 is intended to be attached to the printed circuit board 19.

[0062] The optical modules 15 have a plug 39 on one end and a socket on the other, which together provide a plug-socket connection. This means that the size and location of the plug and socket are selected so that the plug 39 of one optical module 15 can be inserted into the socket of another optical module. The socket is positioned at the same height and width as the plug 39. This connection prevents twisting of the optical modules relative to each other and ensures that the light transmitters or receivers of all optical modules 15 are aligned in the same direction after connecting the two optical modules 15.

[0063] FIG. 5 shows two interconnected optical modules 15, 15′. In the embodiment shown here, the printed circuit board 19 is arranged on one longitudinal side of the support body 17, 17′, while the lens assembly 21 is arranged on the opposite longitudinal side of the support body 17, 17′. The aperture assembly 22 is assembled on the side of the optical module 15 on which the lens assembly 21 is arranged. The aperture assemblies 22 are designed to be attached to the optical modules 15 so that consecutive aperture assemblies 22 are arranged at the transition between the two optical modules 15. Thus, the aperture assemblies 22 arranged on the two optical modules 15, 15′ also ensure that the resolution is uniform across the modules. During assembly, the optical modules 15 are joined together in a first step via a plug-and-socket connection so that the light transmitters or receivers of the optical modules 15 are immediately aligned. To do this, the plug 39 of the first optical module 15 is inserted into the socket of the second optical module. In a second step, the aperture assemblies 22 are attached to the optical modules and the side-by-side optical modules 15 are connected to form one optical module. Adjacent printed circuit boards 19 are connected to one another by connection plugs 37, which form an electronic connection between the two printed circuit boards 19. As an alternative to the embodiment shown in Figure 5, it is also possible to envisage that rather than the aperture assemblies being arranged on the two support bodies, a new aperture assembly is arranged at the transition from one support body to the adjacent support body.

[0064] 6 shows a further embodiment of a photoelectric sensor according to the invention. In contrast to the designs already shown, the housing 13 has a rectangular cross section instead of a round one. The housing 13 is formed from a U-profile 45 and a protective shield 47, which is arranged on the U-profile 45 so that the protective shield 47 closes the opening of the U-profile. An optical module is placed inside the housing 13. The optical module 15 can be attached to both the U-profile 45 and the protective shield 47 of the housing.

[0065] End caps 27 are also provided to close openings at both ends of the illustrated housing 13. The end caps 27 have a shape that corresponds to the cross section of the U-profile 45 and can be positioned adjacent to each opening in the U-profile 45.

[0066] Although specific embodiments have been described above, it will be apparent that various combinations of the illustrated embodiments may be used, provided that the embodiments are not mutually exclusive. [Explanation of symbols]

[0067] 11 Photoelectric Sensor 13. Cabinet 15 Optical Module 17 Support body 19 Printed circuit board 21 Lens assembly 22 aperture assembly 23 Support arm 24 contact points 25 Longitudinal side 26 Protrusion 27 End Cap 28 Placement Rug 29 Light-emitting or light-receiving elements 31 Continuous recess on support body 32 Openings at longitudinal ends of housing 33 Contact surface in the first region 34 Contact surface in the second region 35 Connector 37 Printed circuit board connection plug 39 Plug 45 U-shaped contour body 47 Protective Shield

Claims

1. A photoelectric sensor (11), in particular a light curtain, said photoelectric sensor (11) comprising: an elongated housing (13), an optical module (15) arranged in said housing (13); Equipped with - the light sending and / or light receiving elements (29) are arranged in said optical module (15) at a distance from each other, - said optical module (15) is connected to said housing (13) via contact points (24); a photoelectric sensor (11) in which the optical module (15) and the housing (13) comprise plastic; 1. A photoelectric sensor (11) comprising: at least some of the contact points (24) between the optical module (15) and the housing (13) designed as welded connections, the welded connections between the housing (13) and the optical module (15) being formed by laser transmission welding.

2. 2. The photoelectric sensor (11) according to claim 1, characterized in that, at least in the region of the contact points (24) designed as welded connections, the housing (13) is infrared-transparent and the optical module (15) absorbs infrared rays, or the housing (13) absorbs infrared rays and the optical module (15) is infrared-transparent.

3. 3. The photoelectric sensor (11) according to claim 1, wherein the optical module (15) and the contact points (24) of the housing (13) each comprise a compatible plastic, in particular a thermoplastic material, more preferably polycarbonate.

4. 4. The photoelectric sensor (11) according to claim 1, wherein an infrared-absorbing additive is added to the plastic material of at least one of the components at the intended contact point (24) between the optical module (15) and the housing (13).

5. 5. The photoelectric sensor (11) according to claim 1, wherein the optical module (15) comprises a support body (17), and a printed circuit board (19) having the light transmitting or receiving element is arranged on the support body (17).

6. 6. The photoelectric sensor (11) according to claim 5, characterized in that the support body (17) and the housing (13) are made from compatible plastic materials, and the welded connection is made between the housing and the support body (17).

7. 7. Photoelectric sensor (11) according to claim 5 or 6, characterized in that a lens (21) and / or an aperture assembly (22) is provided on the support body (17) opposite the light transmitting or receiving element (29).

8. Photoelectric sensor (11) according to any one of claims 5 to 7, characterized in that at least the support body (17) and the housing (13) are made from polycarbonate.

9. Photoelectric sensor (11) according to any one of claims 1 to 8, characterized in that the light-sending elements each comprise a light-emitting diode and the light-receiving elements each comprise a photodiode.

10. Photoelectric sensor (11) according to any one of claims 1 to 9, characterized in that the housing (13) has a cylindrical shape, preferably a circular cylindrical shape.

11. Photoelectric sensor (11) according to any one of claims 1 to 10, characterized in that the lateral faces of the housing (13) are integral.

12. 12. The photoelectric sensor (11) according to claim 1, wherein the housing (13) comprises an elongated base body forming a receiving space for the optical module, the elongated base body having at least one opening on a longitudinal side and a protective shield (47) closing at least the opening.

13. 13. The photoelectric sensor (11) according to claim 12, characterized in that the base body is a U-profile (45), the U-profile (45) having one or more openings on one longitudinal side.

14. Photoelectric sensor (11) according to claim 12 or 13, characterized in that the protective shield (47) is welded at its edges to the base body, preferably by laser uranami welding.

15. Photoelectric sensor (11) according to any one of claims 12 to 14, characterized in that the welded connection between the base body and the protective shield (47) forms a connection that is sealed against splashes of water.

16. Photoelectric sensor (11) according to any one of claims 1 to 15, characterized in that end caps (27) are attached to both longitudinally open ends of the housing (13).

17. 17. Photoelectric sensor (11) according to claim 16, characterized in that the end cap (27) is at least partially made from infrared absorbing plastic.

18. Photoelectric sensor (11) according to claim 16 or 17, characterized in that the end cap (27) is rigidly attached to the housing (13) and / or the optical module (15).

19. 19. The photoelectric sensor (11) according to any one of claims 16 to 18, characterized in that the end cap (27) is attached to the housing (13) and / or the optical module (15) by laser transmission welding.

20. Photoelectric sensor (11) according to any one of claims 16 to 19, characterized in that the connection, in particular the weld, between the end cap (27) and the housing (13) forms a seal.

21. Photoelectric sensor (11) according to any one of claims 1 to 20, characterized in that two or more optical modules (15) can be connected to one another at the front side.

22. A photoelectric sensor (11) according to any one of claims 1 to 21, characterized in that the light transmitting and / or light receiving elements (29) of all the optical modules (15) in the housing (13) are oriented in the same radial direction of the cylindrical housing.

23. 23. The photoelectric sensor (11) according to claim 1, wherein the optical module (15) has a first plug-in connection at one longitudinal end and a second plug-in connection at the opposite longitudinal end, the first plug-in connection and the second plug-in connection being connectable to each other.

24. 24. Photoelectric sensor (11) according to claim 23, characterized in that the first plug-in connection is designed as a plug (39) and the second plug-in connection is designed as a socket.

25. Photoelectric sensor (11) according to claim 23 or 24, characterized in that the end cap (27) has a plug-in connection that can be connected to the plug-in connection of the last optical module (15).

26. The photoelectric sensor (11) according to any one of the preceding claims, characterized in that the photoelectric sensor (11) comprises an assembly for fastening the photoelectric sensor (11).

27. A method for making a photoelectric sensor (11) comprising an elongated housing (13) and an optical module (15) arranged within said housing, comprising the steps of: - a light transmitting and / or receiving element (29) is arranged on said optical module (15), - said optical module (15) is inserted into said housing (13); - positioned within said housing (13), 3. The method of claim 2, wherein the optical module (15) is connected to the housing (13) by laser transmission welding.

28. 28. The method of claim 27, wherein the optical module is inserted through an open longitudinal end of the housing.

29. 29. The method of claim 28, wherein the open longitudinal end is closed with an end cap after inserting the optical module.

30. 30. The method of claim 29, wherein the end caps are welded to the housing or to the optical module, preferably by laser transmission welding.

31. 31. The method of any one of claims 27 to 30, wherein the optical module comprises a support arm that contacts the housing upon insertion of the optical module into the housing and centers the optical module within the housing.

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