Patent Publication Number: US-11641698-B2

Title: Connecting thermally-sprayed layer structures of heating devices

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of International Application No. PCT/EP2016/065541, filed Jul. 1, 2016, which designated the United States and has been published as International Publication No. WO 2017/021076 A1 and which claims the priority of German Patent Application, Serial No. 10 2015 214 627.8, filed Jul. 31, 2014, pursuant to 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The invention relates to a heating device for a domestic appliance, comprising a planar carrier with a carrier surface, at least one layer structure that is thermally sprayed onto the carrier surface and at least one solder volume that is applied to at least one thermally sprayed-on layer structure. The invention also relates to a domestic appliance with such a heating device. The invention further relates to a method for producing a heating device for a domestic appliance, wherein a planar carrier with at least one thermally sprayed-on layer structure applied thereon is provided. The invention is, in particular, advantageously usable in cooking devices, in particular with steam cooking capabilities, in washing machines, dishwashers, laundry care appliances and small domestic appliances. 
     In the conventional soldering (e.g. laser soldering, reflow soldering, hand soldering, etc.) of thermally-sprayed layers, the connecting or soldering site is treated with flux to enable adhesion of solder or solder mass. Typically, the thermally-sprayed layer has a thin oxide layer or “oxide skin” which makes an adhesion of the solder mass more difficult or even effectively impossible. The flux serves to break up the oxide skin chemically. However, the flux disadvantageously penetrates into the thermally-sprayed layer, since this is typically slightly porous. It can even penetrate further to porous layers lying thereunder (for example, an insulating layer) and impair their function. In order to prevent a negative influence of the flux (e.g. a worsening of an electrical insulating property), it must previously be washed out thoroughly with solvent. 
     It is already known to produce conducting areas or connecting areas on thermally-sprayed heating conductor layers by means of thermally-sprayed metals (e.g. copper, tin, bronze) and then to solder these metals by means of conventional soldering methods. For the application of not full-surface connecting areas of thermally-sprayed metals (e.g. connecting areas, pads, etc.), however, complex masking must be used. Wear of such masks is high. An application efficiency is low. 
     DE 10 2012 204 235 A1 discloses a domestic appliance for the preparation of foods having a first component and a second component connected to the first component, wherein at least at a connecting site of both components, the first component is made of a first material and the second component is made of a second material different from the first material, and at the connecting site for connecting the components, a solder connection is formed, wherein the solder connection is an ultrasonic solder connection. DE 10 2012 204 235 A1 also concerns a method for producing a domestic appliance. 
     EP 0 963 143 A1 discloses a ceramic carrier with an electric circuit and a connecting device which has at least one metallic connection, for example in the form of a threaded bolt. The connection or the connecting device are connected to the carrier with compensating means consisting of a metal with a greater deformability than the material of the connection, preferably by means of active soldering. The compensating means can be configured in the form of an annular disk or the like and can consist of copper and compensates for the tensions during cooling. The active solder advantageously has a base of silver and copper and a reactive alloy component, for example, titanium or a rare-earth metal. The connecting device can represent both a highly loadable mechanical fastening connection for the carrier and also an electrical connection for the circuit. 
     DE 20 2010 007 081 U1 discloses a device for generating a gas-tight ultrasonic solder connection of two different materials as bonding partners A and B at low temperatures wherein these have a corresponding binding capability with the solder material used, having the following features: a positioning and pre-heating device for a bonding partner B lying lowermost on the joining apparatus, a positioning and placement device for the bonding partner A to be placed thereon, a heating and soldering device for joint warming and soldering of the bonding partners A and B, and a removal device for the joined bonding partners A and B. 
     DE 10 2013 201 386 A1 discloses a cooking hob with a hob plate on which at least one cooking site is formed, and an operating device which comprises electronic components which are positioned, in a plan view of the hob plate, beside the cooking site, and a pot recognition device with which the position of a preparation vessel on the hob plate is recognizable, wherein the pot recognition device has at least one electrically conductive sensor which is configured as a conductor line on the hob plate and, for positional pot recognition, is configured for electrical interaction with a preparation vessel and at least in portions is arranged as an areal delimitation for an area on the hob plate within which the electronic components are arranged. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to overcome at least partially the disadvantages of the prior art and, in particular, to provide an improved capability for the electrical connection of thermally sprayed-on layers or layer structures of a domestic appliance. 
     This object is achieved with the features of the independent claims. Preferred embodiments of the invention are described, in particular, in the dependent claims. 
     The object is achieved with a heating device for a domestic appliance, comprising a planar carrier with a carrier surface, at least one thermally sprayed-on layer structure on the carrier surface and at least one solder volume that is applied to at least one thermally sprayed-on layer structure, wherein the at least one solder volume is an ultrasonically soldered-on solder volume. 
     This heating device has the advantage that the solder or the solder mass of the solder volume firmly adheres to a thermally sprayed-on layer structure without further auxiliary agents, and with a low electrical contact resistance. This is due to the fact that through the introduction of ultrasonic energy, the oxide skin of the thermally sprayed-on layer structure is broken up. By this means, the connection of the solder to the non-oxidized material of the thermally-sprayed layer lying thereunder is enabled, specifically in particular without the use of material without organic components, in particular without flux. 
     The solder or the solder mass advantageously has a high electrical conductivity. In particular, an electrical resistance and a current load capacity of an electrical conductor or solder connection formed by the solder is dimensioned so that a suitability goes beyond a protection low voltage, specifically in particular into a power region (e.g. of 230 V, up to more than 8 A). Particularly advantageously, the solder connection is also sufficiently dimensioned for a use in the high voltage region (e.g. from about 1250 V AC or 1800 V AC). 
     With the ultrasonic support, in general a soldering on of solder is possible on surfaces that are not wettable with solder using classic soldering methods. It is in general possible also to wet very severely oxidized surfaces or non-metallic (e.g. glassy or ceramic) surfaces strongly and precisely with solder. Thus, with ultrasonic soldering, for example, an exposed ceramic insulation (e.g. a ceramic insulating layer) can easily be contacted mechanically and electrically with solder mass. 
     Additionally, ultrasonic soldering is easily usable since it does not need to be masked. Furthermore, in comparison with thermal spraying of metallic connecting layers, etc., it is markedly more efficient in the use of material (material usage for generating the solder or bond site). Additionally, a saving of cycle time and costs can be achieved. 
     Good adhesion strength is also achieved if the thermally sprayed-on layer structure is porous. Good adhesion strength is also maintained under temperature variation loading. 
     Further achieved is the advantage that no corrosion occurs in the connecting site as with “classic” soldering. 
     Moreover, the ultrasonic solder connection is configurable temperature-stable to at least 150° C. It can also have a thermal coefficient of expansion adapted to the substrate and/or the thermally sprayed-on layer. It is also ageing-resistant at high continuous operation temperatures over the whole product lifespan. 
     A planar carrier can be understood, for example, as a flat carrier or a curved carrier (e.g. in tubular form). The carrier can have, in particular, a panel-like basic form. 
     A further development is that the carrier surface is an electrically insulating carrier surface. The electrically insulating carrier surface can be an electrically insulating layer (e.g. of ceramics) applied to a main body or a substrate of the carrier (e.g. a metal sheet). This layer can also have been thermally sprayed-on. The electrically insulating carrier surface can, however, also be a surface-treated (e.g. oxidized) layer region of a main body of the carrier. The electrically insulating carrier surface can have, in particular, a non-negligible porosity. On use of solder flux, this can penetrate, if applicable, into the relevant pores and, if applicable, reduce or even effectively cancel a capacity for electrical insulation—particularly if a high voltage is applied. In particular, if the main body is already itself electrically insulating and temperature-resistant (up to at least 150° C.), a specially formed surface layer can be dispensed with and the carrier surface then represents the non-modified surface of the main body. This can be the case, for example, if the main body consists of ceramics. 
     The carrier surface can be configured at least on a flat side on which a thermally sprayed-on layer or layer structure is situated, electrically insulating over the whole area. Alternatively, the carrier surface is configured electrically insulating only beneath electrically insulating layers or layer structures, if applicable, laterally protruding beyond the layers or layer structures. Thus, electrically conductive thermally-sprayed layer structures can be thermally sprayed-on onto equally wide or somewhat wider layer structures of an electrically insulating layer. 
     A thermally sprayed-on layer can be understood to be a layer which, for example, has been produced by means of molten bath spraying, electric arc spraying, plasma spraying (e.g. atmospheric, under protective gas or under reduced pressure), flame spraying (e.g. powder flame spraying, wire flame spraying or plastic flame spraying), high velocity flame spraying, detonation spraying, cold gas spraying, laser spraying or PTWA spraying, in particular onto the carrier surface. If a plurality of thermally sprayed-on layers or layer structures are present, at least two thereof can be identically configured, e.g. with regard to their material, their layer thickness, etc. Also, at least two thermally sprayed-on layer structures can be configured differently, e.g. with regard to their material, their layer thickness, etc. 
     At least one thermally sprayed-on layer or layer structure can be, for example, a metallic layer or layer structure, e.g. comprising aluminum (Al), bronze, copper (Cu), silver (Ag), tin (Sn), etc. or an alloy thereof. The thermally sprayed-on layer can also be a nickel-chromium alloy (NiCr). The thermally sprayed-on layer can also be a ceramic layer, for example, an electrically insulating layer. A surface of the thermally sprayed-on layer or layer structure can be oxidized. 
     A layer structure should be understood, in particular, to be a layer which, in plan view, has a form different from the form of the carrier surface, that is, no layer covering the whole carrier surface. Rather, the layer structure on the carrier or the carrier surface has, in plan view, its own contour (“outer contour”) which extends at least partially on the carrier surface (and not only on its edge). The layer structure can be present, in particular, in the form of at least one elongate conducting track or line. The conducting line can be wholly or partially straight and/or wholly or partially curved. For example, the conducting line can have a meandering course. The conducting line can however be present, for example, in the form of a short stripe or a rectangular, round, oval etc. contact field. 
     An ultrasonically soldered-on solder volume is, in particular, a solder volume that has been applied by means of an ultrasonic soldering method. 
     It is one embodiment that at least one thermally sprayed-on layer structure is a resistance heating conductor layer, in particular, a thick film. The heating conductor layer can be, in particular, an elongate heating conductor line. The heating conductor line can extend, for example, in a meandering or spiral form. Solder mass can be applied, in particular, in the region of at least one end of the heating conductor layer—in particular, heating conductor line—in order to connect it electrically. As the material of the heating conductor layer, in particular, aluminum, an aluminum compound or a nickel-chromium compound can be provided. The heating conductor layer can thus, in particular, represent a thermally sprayed-on area heater for domestic appliances. 
     It is a further embodiment that at least one ultrasonically soldered-on solder volume electrically connects the thermally sprayed-on layer structure to at least one other component of the heating device. By this means, electrical connections can be created with the thermally sprayed-on layer structure particularly rapidly, economically and reliably. 
     It is a further development that at least one ultrasonically soldered-on solder volume is a solder volume produced in one step or a single stage, which enables a particularly simple and rapid electrical connection. The solder volume can be applied, for example, in one process by means of an ultrasonic soldering iron between the thermally sprayed-on layer structure and another component. 
     It is a further embodiment that at least one ultrasonically soldered-on solder volume is electrically connected by means of a further solder volume not applied by ultrasound, to at least one other component of the heating device. This has the advantage that a part of a solder connection can also be produced by means of another soldering method (e.g. laser soldering, reflow soldering, hand soldering, etc.), which enables a particularly varied possibility for applying the solder volume. In this way, another soldering method can bring about soldering for particular surfaces more gently and/or for complex geometries, simply and more rapidly. With this embodiment, in a further development, a solder volume can firstly be ultrasonically soldered onto a thermally sprayed-on layer and then the ultrasonically soldered-on solder volume can be electrically further connected by means of a solder volume applied by other means. The ultrasonically soldered-on solder volume therefore serves as the basis or substrate for the solder volume not applied with ultrasound. The application of solder volumes by different soldering methods is executable, particularly in the context of a multi-stage, e.g. two-stage, method. 
     It is a further embodiment that at least one other component of the heating device is a further thermally sprayed-on layer structure, on which at least one ultrasonically soldered-on solder volume is present. Then, for example, in a first stage, both thermally sprayed-on layer structures (in general: bonding partners) can be provided with an ultrasonically soldered-on solder volume and subsequently, in a second stage, the two ultrasonically soldered-on solder volumes are connected to one another by means of another soldering method. 
     For example, in this way, a layer structure produced with arc spraying can be connected to a layer structure produced through atmospheric plasma spraying, which are separated from one another by a laser cut. 
     In this way, for example, thermally sprayed-on conductor lines extending mutually parallel can be connected to one another across gaps (e.g. laser cuts). This can be used, for example, for subsequent equalization of an electrical resistor of a thermally sprayed-on heating conductor in order to ensure a required nominal power output of the heating device (“trimming”) and/or for repairing faulty sites in thermally sprayed-on conductor lines (e.g. heating conductor lines). 
     It is an alternative development that the solder volume in the second stage also is or has been ultrasound soldered-on. This corresponds to a two-stage ultrasonic soldering of at least one thermally sprayed-on layer structure. 
     It is a further embodiment that at least one other component of the heating device is a metallic contact. Then, for example, in a first stage, the thermally sprayed-on layer structure can be provided with an ultrasonically soldered-on solder volume and subsequently, in a second stage, the ultrasonically soldered-on solder volume can be directly connected to the metallic contact by means of another soldering method. 
     The metallic contact can be, for example, a contact field applied by galvanizing, application of a metal film, etc. to the carrier surface, e.g. a contact element, for example, of copper. 
     It is moreover a further embodiment that the metallic contact is a contact element of an electrical or electronic component, for example, a contact pin of a plug connector part (e.g. connector plug) or an electrical connector of an electrical or electronic component (e.g. a contact region of an SMD component such as an NTC resistor, a blow-out fuse, of a sensor—e.g. cast in solder glass, etc.). By this means, a thermally-sprayed layer can be connected particularly easily and lastingly to a circuit, etc. The electrical or electronic component is advantageously an SMD (“Surface Mounted Device”). Thus, thermally sprayed-on layer structures and electrical and/or electronic components can be connected to one another particularly easily and economically. The SMD component (e.g. of the size 0603, 0805 or 1206) can be placed by means of a vacuum gripper. Wired components which are provided for a through hole technology (THT) mounting can also be connected by means of their metallic contact to the thermally sprayed-on structure. 
     It is a further embodiment that at least one ultrasonically soldered-on solder volume covers at least a portion of the thermally sprayed-on layer structure—in particular a heating conductor layer—without connecting said layer structure electrically to another—in particular electrically conductive—component of the heating device. In this embodiment, in particular, at least one solder layer (also designated a “conductor layer”) can be applied to the heating conductor layer in order to reduce an electric power density in the heating conductor layer locally. Thereby also, local heating (“hot spots”) can be prevented. A conductor layer can be applied, for example, to power connections at design-related constrictions in conductor lines, at corners and/or at reversal points in the heating conductor layout. The conductor layer or the solder material can also lie on the carrier surface. 
     The object is also achieved with a domestic appliance having at least one heating device as described above. The domestic appliance provides the same advantages as the heating device and can be constructed similarly. 
     The domestic appliance can be, for example, a cooking device or an accessory for a cooking device (e.g. a heatable cooking chamber partition). The cooking device can have, for example, a steam cooking function, the heating device being associated with a steam generating apparatus in order to evaporate water present in the steam generating apparatus. The cooking device can be, for example, an oven with a steam cooking capability or a dedicated steam cooker. The heating device can then represent, for example, a bottom of a water tank. 
     In the case of the heatable cooking chamber partition, at least one thermally sprayed-on layer structure can be present on one side or on both sides, in particular at least one heating conductor layer (structure). 
     The domestic appliance can also be a laundry care appliance. The heating device can then be used, for example, as a washing solution heater of a washing machine or a laundry dryer. The heating device can also be provided as a process air heater. 
     The domestic appliance can further be a dishwasher. The heating device can then be used, for example, as a heater for heating the washing liquid. In this case, the heater is, in particular, a component of a heating pump assembly. 
     The domestic appliance can also be an electrically operated small domestic appliance, e.g. a water boiler, a coffee machine (e.g. in the form of an espresso machine), a toaster, etc. 
     The heating device can be configured as a tube (in general: a rotationally symmetrical body), wherein at least one thermally sprayed-on sealant layer heating conductor is present on a wall of the tube of the domestic appliance. The tube can then be used or intended, in particular, as a flow-through heater for gas passed therethrough (e.g. process air) and/or liquid (e.g. water to be evaporated, washing fluid or washing solution). 
     The object is further achieved with a method for producing a heating device for a domestic appliance, a planar (flat and/or curved) carrier being provided with at least one thermally sprayed-on layer structure applied thereto and at least one solder volume is ultrasonically soldered onto at least one thermally sprayed-on layer structure. The method provides the same advantages as the heating device and the domestic appliance and can be constructed similarly thereto and vice versa. 
     It is therefore one embodiment that at least one thermally sprayed-on layer structure is ultrasonically soldered in one stage to another component of the heating device. For this purpose—for example, by means of an ultrasonic soldering iron—in one process, a track of solder can be drawn from the at least one thermally sprayed-on layer structure to the other component. 
     It is another embodiment that at least one thermally sprayed-on layer structure is ultrasonically soldered in two stages to another component of the heating device in that in a first stage, a solder volume is applied at least to at least one thermally sprayed-on layer structure by means of ultrasonic soldering and this solder volume is soldered in a second stage to the other component of the heating device. The soldering in the second stage can be carried out with or without ultrasound. 
     It is a further embodiment that the other component of the heating device is a thermally sprayed-on layer structure, onto which, in the first stage, a solder volume is applied by ultrasonic soldering and this ultrasonically applied solder volume is soldered, in the second stage, to another ultrasonically applied solder volume of the heating device. 
     Furthermore, it is an embodiment that the ultrasonic soldering is carried out by means of an ultrasonic soldering iron. The ultrasonic soldering iron can have, for example, a sonotrode, which is configured as a soldering tip. 
     It is another embodiment that the ultrasonic soldering is carried out by means of an ultrasonic solder bath (or soldering bath). Herein, a component to be wetted with solder can be dipped in a solder bath before or after mounting on the carrier. The wetting of this component therefore does not need to be undertaken on the carrier, which enables simplified production. The respective individual steps can be improved, where appropriate, by a process of heat treatment (e.g. by pre-heating) of the component. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above-described properties, features and advantages of this invention and the manner in which this is achieved will now be described more clearly and intelligibly with an exemplary embodiment, illustrated in the following schematic description of an exemplary embodiment, which will be described in detail making reference to the drawings. 
         FIG.  1    is a plan view sketch of a heating device of a domestic appliance; 
         FIG.  2    is a sectional representation in side view of a first portion of the heating device of  FIG.  1   ; 
         FIG.  3    is a sectional representation in side view of a second portion of the heating device of  FIG.  1   ; 
         FIG.  4    is a sectional representation in side view of a third portion of the heating device of  FIG.  1   ; and 
         FIG.  5    is a sectional representation in side view of a fourth portion of the heating device of  FIG.  1   . 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE PRESENT INVENTION 
       FIG.  1    shows a plan view of a heating device  1  of a domestic appliance H. The heating device  1  can be used, for example, for heating water situated in a water tank of a steam generator. The domestic appliance H can, however, also be an oven with a steam cooking capability, a dedicated steam cooker, an electrically heatable cooking chamber partition, a laundry care appliance, a dishwasher, a small domestic appliance, etc. 
     The heating device  1  has a planar carrier  2  (e.g. made of a metal sheet) with an electrically insulating carrier surface  3  (e.g. made of a light porous, for example thermally sprayed-on, ceramic layer). A plurality of metallic layer structures  4  to  8  are thermally sprayed onto the carrier surface  3 . The thermally sprayed-on layer structures  4  to  8  are electrically insulated from one another by the carrier surface  3  and comprise: a first (long) meandering heating conductor line  4 , a second (short) meandering heating conductor line  5  and three short straight conductor lines  6  to  8 . 
     The two heating conductor lines  4  and  5  are electrically connected to one another by two tracks  9  made of a first solder or solder material  10 . By this means, the two heating conductor lines  4  and  5  are electrically connected in series. If the second heating conductor line  5  is not to be used, in place of the two tracks  9 , the two corresponding ends of the first heating conductor line  4  could be directly connected to one another by means of a track made of the first solder material  10  (not shown). The electrical resistance can also be exactly trimmed in that a position of the lower track  9  here between the heating conductor lines  4  and  5  can be varied, as indicated by the double arrow. By means of a suitable placement of the tracks  9 , the common heating conductor line  4 ,  5  can consequently be trimmed. 
     As shown in  FIG.  2    in section A-A, for this purpose, the track  9  of the first solder material  10  has been ultrasonically soldered on in one stage from the surface of the first heating conductor line  4  across the carrier surface  3  to the surface of the second heating conductor line  5 . Herein, due to the ultrasonic energy introduced, the first solder material  10  holds both on the heating conductor lines  4  and  5  as well as on the carrier surface  3  without flux being needed for this. The track  9  can be applied, for example, by means of a soldering with an ultrasonic soldering iron. 
     Referring again to  FIG.  1   , the three straight thermally sprayed-on conductor lines  6  to  8  are connected to a connector plug  11  of the heating device  1 , in particular to respective electrical contacts  11   a  of the connector plug  11 . Adjacent conductor lines  6  and  7  or  7  and  8  are connected via respective SMD components  12 . The SMD components  12  are herein, by way of example, NTC resistors which have electrical contacts or contact fields  14  at their end regions in the form of solder terminals. Thus, via the plug frame  11 , measurement values (e.g. electrical resistance values, voltage values or current values) associated with a respective temperature can be read off. 
     The SMD components  12  are fastened via soldering points  13  from the first solder material  10  and a second solder material  15  to the conductor lines  6  and  7  or  7  and  8 , as shown in  FIG.  3    as a section B-B of the heating device  1 . Herein, the conductor lines  6  and  7  or  7  and  8  have been ultrasonically soldered with a solder volume of the first soldier material  10 . Consequently, the SMD components  12  have been placed with their contact fields  14  on respective solder volumes of the solder material  10 . Then, the solder volumes of the solder material  10  have been soldered to the associated contact fields  14  by means of a non-ultrasonic soldering method (e.g. a laser soldering, reflow soldering, hand soldering, etc.) using the second solder material  15 . The first solder material  10  and the second solder material  15  can be the same or different. 
     Consequently, the two conductor lines  7  and  8  are electrically connected to one another by means of the SMD component  12  via the soldering points  13 , which have (partial) solder volumes  13   a  and  13   b  of the first solder material  10  and/or the second solder material  15 . 
     Similarly, for example, the electrical contacts  11   a  (e.g. contact posts or contact pins) of the connector plug  11  are mounted on the conductor lines  6  to  8 , wherein they can have been dipped in a solder bath (not shown) before the mounting of the connector plug  11 . The solder bath can function with or without an ultrasonic input. The solder material introduced in the solder bath can be, for example, one of the solder materials  10  or  15 . 
     Referring again to  FIG.  1   , in addition, two metallic contact areas  16  are applied to the carrier surface, by means of which the combined heating conductor line  4  and  5  can be electrically connected at the end, for example, to a voltage supply. In this regard,  FIG.  4    shows a sectional representation in a side view of a section C-C of the heating device  1 . 
     In this regard, similarly to  FIG.  3   , a solder volume (solder point)  17  of the first solder material  10  has been ultrasonically soldered onto the thermally sprayed-on heating conductor line  4 , and then a track  18  of the second solder material  15  has been drawn with another soldering method (not involving ultrasound) from the solder volume  17  to the metallic contact area  16 , or vice versa. 
     Similarly, the two thermally-sprayed heating conductor lines  4  and  5  could also each be provided with ultrasonically soldered-on solder volumes  17  of the first solder material  10 , which are connected to one another via a track  18  of the second solder material  15 . 
     Referring once more to  FIG.  1   , at a bend in the heating conductor line  4 , a conducting layer  19  has also been ultrasonically soldered only onto the heating conductor line  4  and, if appropriate, the carrier surface  3 , in order to reduce a current density there and so to prevent a formation of “hot spots”, as shown in the section D-D in  FIG.  5   . 
     Naturally, the present invention is not restricted to the exemplary embodiment disclosed. 
     In general, “a”, “an”, etc. can be understood as singular or plural, in particular in the sense of “at least one” or “one or more”, etc., provided this is not explicitly excluded, e.g. by the expression “exactly one”, etc. 
     A numerical value can also include the given value as a typical tolerance range, provided this is not explicitly excluded.