DE202016106889U1 - connecting device - Google Patents

Abstract

Connecting device for mechanically connecting at least a first and a second component, comprising
a longitudinally extending main body (10) having at least a first and a second recess (14, 16), wherein the first recess (14) has a smaller diameter and / or a smaller cross-sectional area than the second recess (16) and the recesses ( 14, 16) are interconnected,
at least one sensor (20, 22), in particular strain sensor (20), which is designed to detect at least one instantaneous parameter of a mechanical connection, wherein at least one momentary state of the mechanical connection can be determined via the parameter, and
a transmitting unit (28) for wireless transmission of the current parameter and / or the current state,
wherein the sensor (20, 22) in the first recess (14) and the transmitting unit (28) in the second recess (16) is arranged.

Description

The invention relates to a connecting device for mechanically connecting at least a first and a second component.

The connecting device comprises at least one sensor, which is designed to detect at least one instantaneous parameter of a mechanical connection, wherein at least one instantaneous state of the mechanical connection can be determined via the parameter. In addition, the connecting device comprises a transmitting unit for wireless transmission of the current parameter and / or the current state.

Mechanical compounds are found in large numbers in all sorts of conceivable industrially or artisanly produced goods. Only as an example may be mentioned at this point, the engineering and vehicle and / or aircraft. Many of these mechanical connections are safety-related components. There is therefore a need to properly monitor such safety-related mechanical connections to either prevent catastrophic failure of the connections or at least mitigate its effects.

It is known from plants such as nuclear power plants to monitor particularly safety-critical mechanical connections by means of dedicated sensors, which determine externally certain parameters of the mechanical connection and forward the data thus obtained wired to a data processing system.

However, these known from the prior art systems for monitoring mechanical connections are prone to failure, expensive to install, inflexible in their applications and require in particular by their cables for data transmission an increased space, which makes them unsuitable for many conceivable applications.

DE 10 2014 217 076 A1 relates to a system for monitoring a mechanical connection, in which a sensor-transmitter arrangement is integrated, for example, in a screw head.

The revelation of DE 10 2014 217 076 A1 in particular with regard to the advantages and refinements of such a monitoring system, is explicitly included in this application.

Both the sensor and the transmitter are according to the DE 10 2014 217 076 A1 arranged in the same recess in the screw head. The disadvantage of this is that in case of breakage of the screw head, the entire sensor-transmitter arrangement is also damaged or solved and no measurement data can be transmitted.

In addition, an arrangement of both the sensor and the transmitter in the same recess for certain sensor types unsuitable.

It is therefore an object of the invention to provide a connecting device for producing a connecting device, in which the instantaneous state of a mechanical connection can be determined even in extreme situations.

The solution of this object is achieved by a device having the features of claim 1.

According to the invention, the connecting device comprises a longitudinally extending basic body with at least one first and one second recess. There are thus provided in particular two recesses in the elongated body.

The first recess has a smaller diameter and / or a smaller cross-sectional area than the second recess.

The diameter and / or the cross-sectional area of the first recess is preferably at most 1/5, 1/4, 1/3, 1/2, 2/3, 3/4 or 4/5 of the diameter or the cross-sectional area of the second recess.

The recesses are interconnected, i. these are connected. Overall, thus resulting in a cross-sectional enlarging recess. The transition between the recesses may be hard or soft. Thus, for example, at a smooth transition, the diameter or the cross-sectional area in the transition region evenly, for example funnel-shaped, change.

In particular, the recesses are arranged in the interior of the base body. The recesses are encased in the base body, preferably by lateral surfaces of the base body.

According to the invention, the sensor is arranged in the first recess and the transmitting unit in the second recess. In the larger, second recess is thus enough space for the electronics, in particular the transmitting unit available.

The connecting device may in particular comprise a receiving unit. Accordingly, data, preferably wirelessly, can also be received. For example, the transmitting unit can be activated by an external interrogation signal and excited to transmit. The receiving unit may be formed with the transmitting unit in particular as a combined transmitting / receiving unit. The receiving unit is preferably arranged in the second recess.

The smaller, first recess, however, is sufficient for receiving the sensor. The sensor may in particular be a strain sensor, preferably a strain gauge.

The fact that both recesses are connected to each other, also the sensor and the transmitting unit can be interconnected, i. the determined data can be transferred to the transmitting unit and sent there.

The sensor and the transmitting unit are in the recesses in the elongate body, to which also e.g. a (lower) part of the screw head can count arranged. If the connection device breaks, e.g. an (upper) part of a screw head, the sensor and / or the transmitting unit are thus not released. The instantaneous parameter of the mechanical connection can therefore still be determined and transmitted even in extreme situations.

At least one instantaneous state of the mechanical connection can be determined via the current parameter. For example, it can also be determined in normal situations whether the connection device functions adequately, e.g. is sufficiently attracted. Too loose a connection can be found as well as too strong a connection.

By the transmitting unit, the current parameter can be sent. The evaluation in this case is done externally, i. outside the connection device.

As an evaluation device can thus serve an external component, which is wirelessly coupled or coupled to the transmitting unit. From the current parameter, the evaluation device can determine at least one momentary state of the mechanical connection.

Alternatively, an evaluation, at least in part, can also be carried out within the connection device and the instantaneous state can be transmitted wirelessly to the outside, e.g. to a display device. It can therefore be provided at least part of the evaluation device within the connecting device. This can in particular serve to save energy and thus to extend the duration of use by transmitting measured values only if they have a relevance and / or exceed a certain limit.

The instantaneous parameter of the mechanical connection detected by the sensor may in particular be a biasing force. For example, the instantaneous parameter may be the biasing force of the connecting device with respect to the first and / or the second component. Alternatively or additionally, the parameter may also be a biasing force between the first and the second component or between a first and a second connection component of the connection arrangement. The term biasing force is to be understood broadly and includes, for example, a tightening force, contact pressure or a contact pressure.

This allows the use of relatively simple design and thus space-saving and inexpensive known sensors.

Since in many mechanical connections the contact pressure or the contact pressure of the connected components is an essential characteristic of the connection, the system according to the invention for monitoring precisely this size can be used advantageously.

The evaluation device may preferably comprise a memory unit which is designed to store at least one desired value for the parameter detected by the sensor. The evaluation device can be designed to compare the parameter detected by the sensor with the desired value stored in the memory unit.

Alternatively, the sensor or the transmitting unit can also be designed with such a memory unit in which nominal and / or calibration values can be stored. In this case, a target / actual comparison of the parameter already take place in the sensor or in the transmitting unit. In particular, e.g. Data is sent if the setpoint is not maintained. On the other hand, if the set point is met, sending data is not necessary, e.g. to save energy.

The provision of the memory unit makes it possible to monitor in a connection device according to the invention whether a mechanical connection is located inside or outside its intended working range. This allows a particularly simple and reliable detection of unwanted or dangerous states of said compound as well as an energy saving.

Furthermore, it is also conceivable, alternatively or in addition to the above-mentioned configuration, to store further data in the same or a further memory unit to which data is accessed can be. It is conceivable, inter alia, data that serve the detection of different sensors, in particular different configurations, or components of the connection device, or calibration data and / or encryption information for a secure communication.

Further developments of the invention can be found in the dependent claims, the description and the accompanying drawings.

According to one embodiment, an evaluation device is provided, which is designed to determine from the current parameter at least one instantaneous state of the mechanical connection, wherein the evaluation device is arranged in the second recess. In particular, all the electronics, e.g. Also, a power supply device, an energy harvesting device and / or a storage unit, be disposed within the second recess. The data relating to the current state can be sent, received by an external component outside the connection device and, for example, further used and / or displayed.

According to a further embodiment, the recesses extend along the base body. The sensor or the transmitting unit is in this way enough space available. Furthermore, certain sensor types require a measurement in the longitudinal direction.

In particular, the first recess may adjoin the second recess, i. the recesses border each other and merge into each other. From outside to inside, the recess thus tapers.

According to a further embodiment, the recesses are arranged parallel and / or coaxial with each other. This is manufacturing technology particularly easy to implement. Thus, initially a recess with a larger diameter and / or a larger cross-sectional area can be longitudinally introduced into the base body, in particular machined. Subsequently, a further recess having a smaller diameter and / or a smaller cross-sectional area is introduced longitudinally into the base body, in particular machined. The second recess does not reach as far into the base body as the first recess.

Preferably, the recesses are arranged centrally in the main body. So is also e.g. the sensor is always centered.

According to a further embodiment, the first and / or second recess is at least partially cylindrical and / or funnel-shaped. Cylindrical recesses are particularly easy to realize in terms of manufacturing technology. For example, the recesses may be holes. If both recesses are funnel-shaped, they can also merge into one another and virtually form a common recess.

The first recess may in particular have a diameter between 0.1 mm and 10 mm, in particular 0.1 mm and 5 mm. Alternatively or additionally, the second recess may have a diameter between 2 mm and 40 mm.

The first recess may be arranged below a screw head and / or above a thread. In particular, this may have a length between 2 mm and 40 mm, preferably between 2 mm and 20 mm. The second recess may be disposed within a screw head. For example, this may have a length between 2 mm and 30 mm.

On the one hand there is enough space available for the sensor or the electronics. On the other hand, the recesses are small enough not to adversely affect the stability or carrying capacity of the connecting device.

According to a further embodiment, the first recess is formed as a blind hole. The recess thus does not extend over the entire length of the body, but ends within the body. Alternatively, the first recess may also be formed as a through hole.

According to a further embodiment, the second recess is releasably closed by a closure element or permanently closed. The closure may in particular be watertight, so that no moisture, e.g. Splashing, penetrates into the interior of the connecting device and possibly the sensor, the transmitting unit and / or other electronic components damaged. The closure element is in particular designed such that it transmits the signal of the transmitting unit.

In a releasable closure element, for example, a cover or clips may be provided, which can be removed or pivoted. By a releasable closure element, e.g. For repair and / or maintenance purposes such as battery replacement in a simple way access to the sensor, the transmitting unit and / or possibly to other electronic components are created.

In a permanently closed closure element, the second recess may be preferably encapsulated. In this case, a certain amount of play can be provided between the sensor unit and optionally further electronic components in order to avoid damage. Above all, casting can be adhered to an inner end. Consequently, the electronics and / or the transmitting unit can become stuck if, for example, a screw head breaks off. Signals can therefore also be sent in extreme situations.

By the closure element, the sensor and the transmitting unit are enclosed safely and in particular water-protected. The fact that the transmission of data is wireless, no openings for cables or the like are necessary, which could possibly penetrate water.

The closure element is designed such that it protects the sensor and / or the transmitting unit, for example against rockfalls.

According to a preferred embodiment, the sensor comprises at least one strain sensor, preferably strain gauges, in particular an arrangement of two or four strain gauges. Strain gauge are inexpensive to produce and work extremely accurate. In particular, the strain gauge can be a metal film strain gauge, a semiconductor strain gauge, or a SAW expansion element.

By way of a strain sensor arranged in the longitudinal direction of the base body, instantaneous parameters of the mechanical connection can be reliably detected by means of which the instantaneous state can be determined. For example, the longitudinal expansion and thus the current biasing force of the connecting element can be determined.

Preferably, the strain sensor with the blind hole bottom and / or a side wall of the first recess, preferably in the longitudinal direction, connected, in particular glued. However, an alignment in the transverse direction is also possible - additionally or alternatively. When using e.g. Metal strain gauges and / or semiconductor strain gages, a combination of the arrangement in the longitudinal and transverse directions is particularly advantageous to detect the mechanical longitudinal stresses of the connecting device. So can be made in a simple and inexpensive way a connection to the body. The adhesive bond does not interfere with the measurement, so that changes in the mechanical connection are transmitted at least substantially one to one. Likewise, another type of connection technology can be selected, for example a welding, screwing, compression, riveting and / or clamping of the expansion sensor with the connecting element.

According to a further embodiment, the connecting device is designed as a screw, bolt or connecting pin. These elongated connection devices are well suited to connect several components together. These also provide enough space for recesses in which a small sensor and a small transmitting unit can be arranged.

In particular, the first and / or second recess can be arranged in a shaft or head of the screw, the bolt or connecting pin. Preferably, the first recess in the shaft and the second recess is arranged in the head. The sensor thus remains in the shaft, even if e.g. the screw head breaks off. It can therefore be determined and / or sent in extreme situations, the current state of a mechanical connection.

The invention also relates to a method for producing a, in particular according to the invention, connecting device for mechanically connecting at least a first and a second component.

In a longitudinally extending main body, a first and a second recess are introduced, in particular machined, wherein the first recess has a smaller diameter and / or a smaller cross-sectional area than the second recess and the recesses are interconnected.

In this case, preferably the second recess is introduced first, e.g. drilled or milled. Thereafter, following the second recess, a first recess of smaller diameter and / or smaller cross-sectional area is introduced, e.g. drilled or milled. The second recess does not reach as far into the elongated base body as the first recess.

Subsequently, at least one sensor, in particular a strain sensor, is introduced into the first recess. The sensor is designed to detect at least one instantaneous parameter of a mechanical connection, wherein at least one momentary state of the mechanical connection can be determined via the parameter.

Preferably, the sensor with the base body, in particular on a Blind hole bottom and / or a side wall of the first recess, connected, eg glued.

A transmission unit for wireless transmission of the current parameter and / or the current state is introduced into the second recess.

In particular, the transmitter unit can be connected to the sensor, with the sensor initially being introduced into the first recess and subsequently the transmitter unit being introduced into the second recess. Alternatively, the transmitting unit and the sensor can be previously connected and introduced as a unit in the recesses.

If the recesses are funnel-shaped in at least one direction, a lateral pressure can be achieved when inserting the sensor and / or transmitting unit, which is useful in the fixed assembly of the elements.

For example, the sensor unit can also be mounted on a web, mandrel or pipe. In particular, the sensor unit can be cooled strongly and inserted into a heated connection device. If both get the same temperature, the components are jammed. A bonding is not necessary here.

The sensor can be introduced in particular on a pin in the first recess. For this purpose, the electronics, in particular the transmitting unit, have a passage. Once the sensor has been placed, the pin can be pulled out again. The pin thus serves only as an aid for introducing and / or positioning the sensor.

Alternatively, the sensor can also be injected, for example, by air pressure.

Finally, the second recess can preferably be closed. The closing can be done in particular waterproof. In this case, the opening facing away from the first recess opening of the second recess can be shed, for example.

All embodiments of the device described here are in particular designed to be operated according to the method described here. Furthermore, all embodiments of the device described here and all embodiments of the method described here can each be combined with each other.

The invention will now be described by way of example with reference to the drawings. Show it:

1 a schematic sectional view of an embodiment of a connecting device according to the invention,

2 a perspective view of an embodiment of various electronic components of a connecting device according to the invention,

3 a schematic plan view of an embodiment of an evaluation device for a connecting device according to the invention,

4 a detail of an embodiment of a connecting device according to the invention,

5 a perspective view of an embodiment of a closure element of a connecting device according to the invention, and

6 a perspective view of an embodiment of a connecting device according to the invention.

First, it should be noted that the illustrated embodiments are merely exemplary in nature.

1 shows a trained as a screw connecting device with an elongated, as a shaft 10 trained body, which has an external thread 12 may have, as well as a screw head 13 , which may be formed as a hexagon and forms a mounting portion.

The main body 10 includes a first recess 14 and a second recess 16 , The first recess 14 has a smaller diameter and / or a smaller cross-sectional area than the second recess 16 on. The first recess 14 can be considered a blind hole 18 be educated. The second recess 16 can in the screw head 13 be arranged.

The recesses 14 . 16 are connected. A transition area 19 between the first recess 14 and the second recess 16 may be funnel-shaped.

In 2 are an active sensor 20 , a passive sensor 22 and a temperature sensor 24 shown. The temperature sensor 24 is purely optional and can be used to determine the temperature.

Also, only an active sensor 20 or a passive sensor 22 be provided. Basically, a single sensor is enough 20 . 22 ,

For the active sensor 20 it can be a strain sensor, in particular strain gauges or an arrangement of several Strain gages act. The active sensor 20 can detect long-term changes of at least one parameter, in particular a tightening force, a mechanical connection.

The passive sensor 22 can be designed as a piezoelectric or electrodynamic connection sensor. The passive sensor 22 can detect changes in the time of the mechanical connection parameter and / or generate electrical impulses when the parameter changes.

The active sensor 20 can via the passive sensor 22 and / or the temperature sensor 24 to be activated.

The temperature sensor 24 may include a temperature sensor. Alternatively, the temperature sensor 24 also as part of the active sensor 20 be self-trained. For example, the temperature may be due to a voltage drop of one or more strain gauges 20 be determined. In particular, the total resistance changes with a temperature change. The resistor is arranged directly on the strain gauge or a bridge with several strain gauges. The temperature can also be measured, for example, in the case of semiconductor strain gages on a diode or at a temperature measuring resistor arranged parallel or at a specific angle, for example 45 °, to the measuring resistors.

The sensors 20 . 22 . 24 are preferably on a dock 26 attached, which is formed for example as a board material, flexible circuit board or preformed to the bore cross section preformed flexible tube or rigid mandrel. This can, for example, for pressing the sensors 20 . 22 . 24 during insertion of the electronics unit in the connecting device during assembly to the first recess 14 be slightly conical. The sensors 20 . 22 . 24 can through the jetty 26 in the first recess 14 the connection device are placed.

Above the jetty 26 is a sending unit 28 intended. This is located, together with other electronic components, in the mounted state in the second recess 16 , The transmitting unit 28 can be a radio module 30 with an antenna 32 include. Optionally, the antenna 32 be divided into two areas. Thus, a first area may receive signals from the evaluation device 34 and a second area for sending data to the evaluation device 34 serve. In this way, the communication can be made bidirectional and the evaluation device 34 can request readings from the connection device if required. The radio module 30 may have a controller with an electromagnetic shield.

The transmitting unit 28 can wirelessly send the current parameter and / or the current state of the connection device.

The transmitting unit 28 In particular, temperature based temperature data provided by the temperature sensor may also be used 24 be determined, send wirelessly. Optionally, the temperature can also be controlled by a temperature sensor mounted in or on the controller 24 be recorded.

For example, if a temperature limit value is exceeded or not reached, a warning signal and / or the temperature as temperature data can be sent wirelessly. Alternatively or additionally, temperature data for determining a warning signal when exceeding or undershooting a temperature limit value can be sent wirelessly.

The temperature influence on the current parameter can still be compensated in the connection device. Alternatively or additionally, the temperature data for compensation of a temperature influence on the current parameter can be sent wirelessly, for example to an external evaluation device 34 as related to 3 will be described in more detail.

The connecting device may be a button cell 36 comprise trained energy storage. As energy storage 36 For example, it is also possible to use an accumulator, a battery, in particular a thin-film battery, a capacitor and / or a supercap.

The passive sensor 22 can also serve as an energy recovery device and, for example, the energy storage 36 load or for direct power to the electronics, in particular the transmitting unit 28 and / or the active sensor 20 , serve. Alternatively, the passive sensor 22 is arranged in a swingable region of the connecting device and is set in motion via inertial forces.

The energy storage 36 can in a holder 38 be included. In this holder 38 can the energy storage 36 be kept releasable. A quick exchange is made possible.

Between the energy storage 36 and the transmitting unit 28 can be an analogue electronics 40 with an analog preamp 42 be provided.

The transmitting unit 28 is adapted to the data of the at least one sensor 20 . 22 . 24 to send wirelessly. Optionally, in the second recess 16 Also an evaluation device may be provided, which initially at least partially evaluates the data before they are sent.

The current parameter or instantaneous state, eg the momentary tightening force, as well as possibly the temperature data can be transmitted via the transmitting unit 28 be sent wirelessly, for example to an external evaluation device 34 , a display device and / or a central system of a vehicle.

In 3 is an external evaluation device 34 shown. This can be, for example, a smartphone or a tablet.

The evaluation device 34 includes a receiving unit 44 , a computing unit 46 as well as a display 48 trained display device.

The signals of the transmitting unit 28 can from the receiving unit 44 be received wirelessly and to the arithmetic unit 46 to get redirected. The arithmetic unit 46 can evaluate the received data. In this case, the arithmetic unit 46 For example, access a database. The evaluated data can be displayed graphically and on the display, for example 48 be issued. For example, it can be shown how high the tightening force and / or temperature of the connecting devices is or whether the tightening force and / or temperature reach a critical value.

It can be easily checked, for example, whether the screws of a tire or all tires of a vehicle are tightened enough and safe operation is possible. Furthermore, a loosening of the screws and thus a theft of the wheel bolts can be detected. Through the combination of passive and active sensor 22 . 20 the slow and sudden loosening of the screws can be detected instantaneously, so that also a sudden tearing off of the screw head 13 or a theft of the screws can be detected low energy at a long standstill of the car.

In 4 is shown a mounted state. You can see them in the second recess 16 arranged electronic components, such as the transmitting unit 28 , Below, in the first recess 18 , are the sensors 20 . 22 . 24 intended.

The strain gauge 20 can be on one end face at the bottom of the blind hole 18 attached, in particular glued, welded, screwed, pressed, riveted and / or jammed, be. Alternatively or additionally, the strain gauge 20 also on a side wall of the blind hole 18 be attached. At least one sensor 20 . 22 . 24 stands with the transmitting unit 28 in contact.

The second recess 16 can through a closure element 50 be closed. A closure element 50 is exemplary in 5 shown. The closure element 50 can be clipped onto the connection device. These can be several locking lugs 51 be provided, which are preferably arranged evenly distributed. In this way, the second recess 16 , in particular solvable, sealed and the electronics are protected in particular from water ingress. Alternatively, the recess 16 also be completely poured with a protective compound.

Preferably, the closure element 50 signal transmissive, ie that of the transmitting unit 28 data sent may be the shutter element 50 penetrate.

6 shows a connecting device with attached closure element 50 , For example, for maintenance purposes, the closure element 50 simply removed.

LIST OF REFERENCE NUMBERS

10

Shank, basic body

12

external thread

13

Screw head, hexagon, mounting section

14

first recess

16

second recess

18

blind

19

Transition area

20

active sensor, strain sensor, strain gauges

22

passive sensor, piezoelectric or electrodynamic connection sensor

24

temperature sensor

26

Bridge, flexible circuit board, tube, conical mandrel

28

transmission unit

30

radio module

32

antenna

34

evaluation

36

Battery, energy storage

38

bracket

40

analog electronics

42

Analogvorverstärker

44

receiver unit

46

computer unit

48

Display, display device

50

closure element

51

locking lug

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102014217076 A1 [0006, 0007, 0008]

Claims (17)

Connecting device for mechanically connecting at least a first and a second component, comprising a longitudinally extending main body ( 10 ) having at least a first and a second recess ( 14 . 16 ), wherein the first recess ( 14 ) has a smaller diameter and / or a smaller cross-sectional area than the second recess ( 16 ) and the recesses ( 14 . 16 ), at least one sensor ( 20 . 22 ), in particular strain sensor ( 20 ), which is designed to detect at least one momentary parameter of a mechanical connection, wherein at least one instantaneous state of the mechanical connection can be determined via the parameter, and a transmitting unit ( 28 ) for wireless transmission of the current parameter and / or the instantaneous state, wherein the sensor ( 20 . 22 ) in the first recess ( 14 ) and the transmitting unit ( 28 ) in the second recess ( 16 ) is arranged. Connecting device according to claim 1, characterized in that an evaluation device ( 34 ) is provided, which is adapted to determine from the current parameter at least one instantaneous state of the mechanical connection, wherein the evaluation device ( 34 ) in the second recess ( 16 ) is arranged. Connecting device according to claim 1 or 2, characterized in that the recesses ( 14 . 16 ) inside the body ( 10 ) are arranged. Connecting device according to one of the preceding claims, characterized in that the recesses ( 14 . 16 ) along the body ( 10 ). Connecting device according to one of the preceding claims, characterized in that the first recess ( 14 ) to the second recess ( 16 ). Connecting device according to one of the preceding claims, characterized in that the recesses ( 14 . 16 ) are arranged parallel to each other. Connecting device according to one of the preceding claims, characterized in that the recesses ( 14 . 16 ) are arranged coaxially with each other. Connecting device according to one of the preceding claims, characterized in that the first and / or second recess ( 14 . 16 ) is formed at least partially cylindrical and / or funnel-shaped. Connecting device according to one of the preceding claims, characterized in that a soft transition between the first and the second recess ( 14 . 16 ) is provided, in particular wherein the diameter and / or the cross-sectional area in the transition region ( 19 ) evenly, preferably funnel-shaped, changes. Connecting device according to one of the preceding claims, characterized in that the first recess ( 14 ) as a blind hole ( 18 ) or through hole is formed. Connecting device according to one of the preceding claims, characterized in that the second recess ( 16 ) by a closure element ( 50 ), in particular waterproof, closable. Connecting device according to claim 11, characterized in that the second recess ( 16 ) through the closure element ( 50 ) is releasably closable. Connecting device according to one of claims 1 to 10, characterized in that the second recess ( 16 ) by a closure element ( 50 ), in particular waterproof, permanently closed, preferably potted, is. Connecting device according to one of the preceding claims, characterized in that the sensor at least one strain sensor ( 20 ), preferably strain gauges, in particular an arrangement of two or four strain gauges, in particular wherein the strain sensor ( 20 ) with a blind hole bottom and / or a side wall of the first recess ( 14 ), preferably glued, welded, screwed, pressed, riveted and / or jammed, is. Connecting device according to one of the preceding claims, characterized in that the sensor ( 20 ) comprises at least one metal film strain gauge, a semiconductor strain gauge and / or a SAW strain element. Connecting device according to one of the preceding claims, characterized in that the connecting device is designed as a screw, bolt or connecting pin. Connecting device according to claim 16, characterized in that the first and / or second recess ( 14 . 16 ) in a shaft ( 10 ) or head ( 13 ) of the screw, the bolt or connecting pin is arranged.

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