EP4327060A1

EP4327060A1 - Monitored spring assembly, and methods for manufacturing and operating same

Info

Publication number: EP4327060A1
Application number: EP22722426.8A
Authority: EP
Inventors: Albert Enste
Original assignee: Federnfabrik Schmid AG
Current assignee: Federnfabrik Schmid AG
Priority date: 2021-04-22
Filing date: 2022-04-11
Publication date: 2024-02-28
Also published as: DE102021110346A1; WO2022223350A1

Abstract

The invention relates to a springy assembly (1) which, in addition to a springy part (2), generally a simple spring (2), comprises a measuring assembly (20) having a load sensor (3) to measure the load on the spring (3) during operation and transmit the load measurements to a monitoring unit (50) by means of a wireless transmitter unit (4).

Description

Controlled spring assembly and methods of manufacture and operation

I. Field of application

The invention relates to resilient components, which usually have only a limited lifespan, since they become non-functional due to fatigue or overload, by changing their suspension behavior or being completely destroyed.

II. Technical background

If a built-in spring fails to function, it usually leads to an immediate failure or shutdown of the entire higher-level mechanical unit and, in the worst case, can lead to an accident.

The downtime of the machine unit due to the necessary replacement of the defective spring, the associated repair costs and, if necessary, the previous procurement of spare parts, represents a loss that is usually high in comparison to the value of the spring.

In addition, the defect of each individual spring, which occurs at different points in time, again causes such a downtime.

Although the expected normal service life of the spring under the target conditions of use is generally known, these conditions of use can change in practice, in particular unexpected overloading can occur or have occurred and in particular have not been noticed and the target service life has been shortened as a result.

III. Presentation of the invention a) Technical problem

It is therefore the object of the invention to provide a resilient assembly that is as cost-effective as possible, the actual load of which is checked during operation, preferably constantly, and from this the time point of the probable actual failure of the resilient component can be predicted much more precisely , the remaining force of the spring can be calculated and the probability of failure in the current state can be calculated. It is also the object of the invention to provide a method for cost-effective assembly and operation of such a resilient assembly. b) Solution to the problem This problem is solved by the features of claims 1 and 11 . Advantageous embodiments result from the dependent claims.

A generic spring assembly comprises, on the one hand, the resilient component - hereinafter referred to as spring for short - and a measuring assembly operatively connected thereto with a load sensor, in particular a load sensor fastened to it, a memory unit for temporarily storing the measured data, and a transmitter unit for wireless transmission of the load values measured by the load sensor to a higher-level monitoring unit.

Since the load sensor and/or the transmission unit require energy for their function, such a spring assembly also has an energy supply. Since usually both the load sensor and the transmitter unit, as If other components mentioned below that require energy for their function are also operated using electricity, the energy supply is a power supply.

In the following, only electric current is mentioned as the form of energy used, without restricting the invention to this.

According to the invention, this energy supply includes an energy generator, in particular a current generator, in particular as part of the spring assembly.

In addition or instead, an energy store, in particular a battery, can be present, which ensures the energy supply and can be recharged contactlessly, for example by means of induction or by means of electromagnetic radiation, which is converted into electricity by one of the components of the spring assembly can be converted.

In this way, the load on the spring can be measured continuously over a long period of time or at intervals, so that conclusions can be drawn about the residual force, the probability of failure and the the remaining life of the spring can be drawn.

In particular, this is done automatically by an evaluation unit, which can be configured together with the superordinate monitoring unit or can be part of the monitoring unit, so that the operator can be informed of the force of the spring, preferably via an output unit still has and when or if the remaining service life of the monitored spring ends or if a breakage of the spring has occurred. Preferably, the load is determined by measuring the torsion or bending or extension of the spring using the load sensor, for example using a strain gauge (DMS) or an opto-electrical sensor as the load sensor.

Such strain gauges and, to a limited extent, also opto-electrical sensors are very inexpensive and, if they are suitably mechanically protected, have a very long service life and only have to be applied, in particular glued, to the surface of the spring at a suitable point, preferably at such a point where the torsion or flexing or stretching of the spring is greatest during operation.

So that no load values are lost if data is not being transmitted at the same time, the spring assembly preferably has a data memory in which the measured load values are buffered or generally stored until they are transmitted to the monitoring unit. This is preferably a so-called non-volatile data memory, which is understood to mean a data memory that does not lose its information content even when there is no current, although of course in normal operation the data memory also depends on the energy supply with energy, preferably electricity , is supplied.

Since the spring assembly is often installed in places that are difficult to access, it is important that the spring assembly can work independently for as long as possible for the energy supply and for querying measured values.

The energy supply of the spring assembly preferably includes a buffer store for energy, preferably a battery that can be recharged without any problems: The reloading can cause an internal energy generator that is part of the spring assembly, or an external energy supplier that supplies energy to the spring assembly without contact, preferably also over a greater distance, for example by means of electromagnetic waves.

The energy supplier can also be the data query unit of the superordinate monitoring unit at the same time. The data interrogation unit can be an RFID antenna and the transmitter unit of the spring assembly can be an RFID tag, which uses the RFID antenna to send the information contained in the RFID tag to the interrogation unit on request , but at the same time receives energy via the query signal from the RFID antenna, with which such a buffer battery can be recharged.

The transmitter unit can also be a Bluetooth low energy unit or a specially developed communication unit.

The energy supplier can also generate electrical energy using other methods, such as the piezoelectric effect or the Peltier effect

An internal energy generator, in particular an internal current generator, can be a separate part from the other electrically operated components, or can be functionally combined with one of these electrically operated components of the spring assembly.

One of the sensors of the spring assembly or the transmission unit could be designed in such a way that it generates electricity through its operation, in particular the stretching or movement of either the energy generator or the spring on which the energy generator is usually attached, is converted into energy or the temperature of the energy generator or the part to which it is attached can be used to generate energy. Such an energy generator can be, for example, a piezo element or a Peltier element, which is known to generate electricity from a temperature, in particular a temperature difference, such a temperature difference being generated, for example, by an insulating housing of the spring assembly can be generated, which causes different temperatures to prevail on the inside and the outside of the enclosure. The Peltier element can also be mounted on the printed circuit board or another support element of the spring assembly and generate electricity from the differences in temperature there.

Preferably, the transmission unit can also be configured to receive data, i.e. be designed as a combined transmission/reception unit, whereby not only energy-yielding electromagnetic waves can be received by the transmission/reception unit and converted into electricity, but control signals can also be sent to the spring assembly, for example control signals for activating the load sensor at a certain point in time or the like.

Even a so-called passive transponder does not require its own energy supply and supplies data stored in it upon request, with the energy for sending the data being transmitted only by means of the request signal.

The spring assembly can be further developed by having additional components, in particular additional sensors, and/or at least one LED. The LED can be used to communicate certain statuses to the operator, for example overload on the spring or just the readiness for communication with the spring assembly.

On the one hand, this could be a temperature sensor, with the help of which the temperature of the spring or the air around the spring can be measured, which is of interest since the temperature has a considerable influence on the lifespan of a spring - including in all Usually a spring made of metal is understood - has. For the same reason, a pollutant sensor can be present, which measures the content of harmful substances on the spring or in the ambient air.

For the same reason, an acceleration sensor or position sensor can be present, which measures the acceleration of the spring assembly or the distance covered by it. These values can be used as a trigger signal for measuring the spring load.

Furthermore, an analogue/digital converter can be present in order to convert the data, which is usually supplied in analogue form, into a digital signal which can be stored and also sent more easily.

It is also possible to use a measuring amplifier to amplify the usually relatively weak, mostly analog, measuring signals.

The design of the spring assembly is particularly simple if different functions can be combined in one component, i.e. functions can be combined:

As an example, an RFID tag contains current-conducting conductor tracks applied to a rigid or flexible plastic circuit board, usually in a spiral shape.

Another example here is a Peltier element, which can be included in the spring assembly and can generate electricity due to the temperature differences on its two sides.

Sections of these traces or the entire trace could be used on the one hand as a load sensor and / or on the other hand for energy generation are used, the latter, for example, by signals from the query unit are sent to the RFID tag, the even do not aim to query measured values, but only to send energy containing electromagnetic radiation to the RFID tag and ultimately serve to charge or recharge the buffer battery.

A DMS used as a load sensor could also be used to generate electricity.

With regard to the method for operating a spring assembly, which is designed in particular as described above, this object is achieved in that during operation the loading of the spring is constant or only at intervals, in particular either only on request or triggered by a defined acceleration threshold value or minimum distance covered, which is measured by means of a corresponding sensor, and the measured stress values are sent wirelessly to a monitoring unit.

An evaluation unit there informs the operator in advance, if possible, about the approaching end of the service life of the monitored spring, or at least reports the breakage of such a spring very quickly. Alternatively, an evaluation unit can also be integrated into the spring assembly and report critical loads to the higher-level unit. This evaluation unit can also light up an LED on the spring assembly as a warning. In this way, system downtimes can be minimized by replacing one or more installed springs as a preventive measure shortly before the end of their service life. Since the factors influencing the service life such as temperature, pollutants in the environment, level and frequency of the load and its duration can also be taken into account by an evaluation unit, no early exchange of the springs and no unnecessarily frequent downtimes of the corresponding system.

The load on the spring is preferably determined based on the deflection of the spring, because this, together with the material characteristics of the spring, is one of the parameters from which conclusions can best be drawn about the remaining spring force and the remaining service life of the spring.

The energy-requiring components of the spring assembly, such as the load sensor or transmitter unit, are preferably operated with electricity, so that an existing buffer store for energy is usually a battery that can be recharged.

Because it can be recharged, the backup battery can be selected to be small and inexpensive, which means that the entire spring assembly can be small and inexpensive, which is of particular advantage for attachment to the spring.

Such a buffer memory is either recharged contactlessly from outside the spring assembly, either via induction or by means of electromagnetic radiation, but without such an energy supplier having to be brought too close to the spring assembly. In particular, this can be done without relocating from a higher-level monitoring unit, which is usually permanently installed in the vicinity of the spring assembly, and which can include such an energy supplier and/or an interrogation unit that can be functionally combined.

The buffer memory can instead or additionally be recharged by means of an internal power generator that is part of the spring assembly, be it via an RFID tag or a passive transponder or other ren power generator that is capable to generate electricity from a movement, a temperature, a temperature difference or an expansion of a component. The measurement of the load on the spring can be carried out at specified points in time, or can only be carried out on request from the outside, which of course greatly reduces the energy requirement for the load sensor and the storage unit for the measured values. c) exemplary embodiments

Embodiments according to the invention are described in more detail below by way of example. Show it:

Figure 1a: a leaf spring package on a vehicle axle with measuring unit,

Figure 1b: a spiral spring with a measuring unit,

Figure 2a, b: the measurement assembly mounted on the surface of a spring in side view,

FIG. 3: a measurement assembly glued onto a spring viewed from above.

FIG. 1a shows, as resilient component 2, a leaf spring assembly on a motor vehicle axle, which, as shown, generally consists of several individual leaf springs 2 that are placed one on top of the other and are curved convexly downwards and are held together by clips. The axle body 19 is fastened running transversely to the direction of extension under the leaf spring assembly, in that there is such a spring assembly in each of the two end regions of the axle body 19 and a wheel 21 is rotatably fastened to each end of the axle body 19.

Two points are shown at which the load sensor 3 or the entire measuring assembly 20 can be attached to one of the springs 2 of the spring assembly:

ok Once approximately in the middle between the end attachment points of the spring package, ie at the same point at which the axle body 19 is located below, therefore preferably on the top of the spring package. As a rule, these should be the points at which the highest tensile load of the material occurs, since material fatigue or material destruction at this point of the highest load is also the cause of damage to the spring up to and including breakage.

In the case of deflection in the vertical direction, the elongation occurring in this area, for example, of the uppermost spring 2 in this case is determined by the load sensor 3 or the measuring assembly 20 .

However, the movement path of the spring 2 and thus of the measurement assembly 20 can be relevant due to its movement if the measurement assembly 20 includes an energy generator 14 .

Figure 1b shows a spiral spring in which the load sensor 3 is applied, in particular glued, to a winding, in particular the inside thereof, of the spiral spring 2, or an entire measuring assembly 20 including the load sensor 3.

In all these cases, the measurement module 20 is either permanently or only sporadically wirelessly connected to a monitoring unit 50, which on the one hand includes a query unit 51 for querying the measured values from the measurement module 20, with which it is wireless can get in touch, and which on the other hand generally has an evaluation unit 52 for evaluating the measured values received. Such a monitoring unit 50 does not necessarily have to be installed on the spring, but can be a mobile device, including a Flandy or tablet or similar, which is only brought close to the spring assembly to read out the data. This will be the case in particular if the spring assembly in your design can work, measure and store measurement data independently for longer.

In order to communicate the results of the evaluation unit 52 to the operator, the monitoring unit 50 also has an output unit 50a, in this case shown as a display on the monitoring unit 50.

FIG. 2a shows in a 1 . Design of such a measuring assembly glued to a spring 2:

The load sensor 3, for example a DMS or an opto-electrical sensor, is glued to the outer surface of a spring 2 by means of an adhesive layer 16.

The load sensor 3, such as a strain gauge or an opto-electrical sensor, can in turn be found on the underside of a conventional electronic circuit board 17 and be connected to it firmly but preferably only at certain points, if possible at only one connection point, which is on its facing away from the top can carry more electrical or electronic components.

In the case of a large-area connection, the limited extensibility and flexibility of the circuit board 17 would have an adverse effect on the measurement result.

Here, for example, there is a transmitter unit 4 in the form of the electrical conductor tracks 18, which are applied to the circuit board 17 and which can represent a transmitter unit 4 such as an RFID transponder or also called an RFID tag, at least together with an electronic circuit, not shown, which is connected to the conductor tracks 18 of the RFID tag.

The transmitter unit can also be a Bluetooth low energy unit or a specially developed communication unit. On the circuit board 17, in particular also on the top side facing away from the load sensor 3, there can also be an electronic data memory 6, a preferably non-volatile data memory s, as well as an analog/digital converter 7 and/or a Measuring amplifier 8 and an electronic circuit 22, which can also work as an evaluation unit.

A buffer store 15 for energy, in particular a buffer battery 15, can also be present on circuit board 17.

All electrical or electronic components are electrically conductively connected to each other according to their function.

A pollutant sensor 13 is also arranged on the circuit board 17 - but not absolutely necessary in this case - on the underside and away from the load sensor 3, which is intended to determine certain pollutants in the immediate vicinity of the Fe 2, and depending on the design can also be in contact with the spring 2.

Furthermore, an acceleration sensor 24 can also be present.

The pollutant sensor 13 and the acceleration sensor 24 can, of course, be electrically connected to the other electronic designs.

A backup battery 15 could possibly be dispensed with if only for a query by the monitoring unit 50 and its query unit 51 using the load sensor 3 and using the supplied by the query unit 51 by the electromagnetic radiation of the query electrical energy would be measured.

Preferably, however, the measurements by the load sensor 3 should be independent of the time at which the measured values are queried by the monitoring ment unit 50 may be possible and for this purpose a buffer battery 15 is provided, which is recharged, for example, by an energy generator 14, which is preferably also present on the circuit board 17.

Preferably, strain gages or the opto-electrical sensor and electronic circuit board 17 can also not be connected to one another over a wide area, but arranged next to one another according to the side view of FIG Carrier film 23 of the DMS not to be negatively influenced by the surface connection with the rigid and much less stretchable electronic circuit board 17.

FIG. 3 shows a measurement assembly 20 in a plan view from above, which includes both a load sensor 3 and a transmission unit 4 in the form of an RFID tag.

The latter consists of an electronic circuit 2, which is applied to the electronic circuit board 17, in particular soldered, and with the several con centrically arranged, ring-shaped each almost closed electrical Lei terbahnen 18b, which is also on the electronic circuit board 17 in a known manner and Way can be formed and are connected to an electronic circuit 22 at the respective free ends.

The transmitting unit 4 formed from the conductor tracks 18 and the electronic circuit 22 is also designed as a receiving unit and can receive signals via these concentric conductor tracks 18b, which also act as an antenna.

The concentric conductor tracks 18 are on the one hand suitable for receiving the query signal and generating energy, which is then temporarily stored in the buffer battery 15 coupled to the electronic circuit 22 . The electronic circuit 22 can also include circuit parts that are suitable for connecting the resistance wire of a DMS and registers its changing voltage values and, in particular, can store them in a data memory 6, which is preferably part of the electronic circuit 22.

Instead of the DMS, an opto-electrical sensor can also be used as a stress sensor, which optically detects and registers strains and can store the strain changes in a data memory 6, which is preferably part of the electronic circuit 22.

The resistance wire can also be in the form of printed conductors 18 applied to the circuit board 17, for example vapor-deposited.

In the case shown, the conductor track 18a of the DMS is in the form of long meandering loops extending in a primary direction, specifically in the central inner free space of the concentrically running conductor tracks 18b of the RFID.

The main direction of extension of these meander loops represents the preferred measuring direction of the DMS, so that the entire circuit board 17 is generally longer in this main direction of extension, the first surface direction 11 of the circuit board 17, than in the second surface direction 12, which runs transversely, preferably perpendicularly, thereto.

This makes it clear to the user which is the measuring direction of the measuring assembly 20, which, apart from the components shown on the top of the circuit board 17 in FIG.

Ideally, conductor tracks 18 applied to the circuit board 17 should be usable both as a load sensor 3 and/or as an RFID antenna and/or as an energy generator 14, for example at different times. Thus, the meandering conductor tracks 18a, which are primarily designed as DMS resistance wires, can serve as an antenna for the transmitter/receiver unit 4 like the concentric conductor tracks 18 at times when there is no load measurement.

Furthermore, both the traces 18b of the RFID and the traces 18a of the DMS can be used as an energy-generating piezo element if their traces 18a, b are made of a semiconductor such as silicon, which has a piezoelectric effect in the form of power generation under mechanical stress .

The current generated by the movement and/or stretching/compression of the spring 2 and analogous movement and stretching or compression of such a piezo element can then be used at least away from the times when these conductor tracks 8a, b have another function, such as an RFID antenna or DMS are to meet, are tapped and thus the buffer battery 15 charged who the.

In this sense, the illustration in FIG. 3 can show not only a top view of a hard electronic circuit board 17, but also a top view of a thin and elastic carrier film 23, as required for a DMS as a carrier for its conductor tracks 18h .

In this case, the electronic circuit 22 and/or the data memory 6 and/or the buffer battery 15 can be accommodated, in contrast to the illustration in FIG. REFERENCE LIST

1 spring assembly

2 resilient component, spring

2a surface

3a load sensor, strain sensor, DMS

3b opto-electrical sensor

4 transmitter unit, RFID

5 power supply

6 data storage

7 analog/digital converters

8 measuring amplifiers

9 temperature sensor

10 perpendicular to the surface

11 1. Surface Direction

12 2. Surface Direction

13 pollutant sensor

14 energy generators

15 buffer tanks

16 adhesive layer

17 circuit board

18 track

19 axle body

20 measurement assembly

21 wheel

22 electronic circuit

23 carrier film

24 motion sensor 50 surveillance unit

50a output unit

51 interrogation unit

52 evaluation unit

DMS strain gauges

Claims

EXPECTATIONS

1. Spring assembly (1) with

- a resilient component (2), in particular a spring (2),

- A measuring assembly (20) which is operatively connected to the resilient component (2) and which comprises

- A load sensor (3), a data memory (6) for storing the load measured readings

- a transmission unit (4) for wireless transmission of the measured load values,

- A power supply (5) for supplying at least the load sensor (3) with power, characterized by

- The energy supply (5) comprises an energy generator (14) and/or an energy store (15), in particular a contactless rechargeable battery (15).

(Specifically: DMS)

2. Spring assembly according to claim 1, characterized in that

- the load sensor (3) is a strain sensor (3),

- In particular, a strain gauge (DMS) or an opto-electrical sensor (3).

3. Spring assembly according to any one of the preceding claims, characterized in that

- The load sensor (3), in particular the strain sensor (3) or the opto-electrical sensor (3), on the surface (2a) of the resilient component (2), in particular the spring (2), is attached. (Other optional components:)

4. Spring assembly according to any one of the preceding claims, characterized in that

- The data memory (6), in particular the non-volatile data memory (6), is supplied with energy from the energy supply (5).

5. Spring assembly according to any one of the preceding claims, characterized in that the spring assembly has

- an analog/digital converter (7) for digitizing the analog measured values and/or

- An electronic circuit (22) for evaluating the analog measured values and/or a measuring amplifier (8) for amplifying the, in particular analog, measured values and/or

- a temperature sensor (9) for measuring the ambient temperature around the spring assembly (1) and/or

- A pollutant sensor (13) for measuring the content of harmful for the spring-promoting component pollutants in the ambient air or on the pollutant sensor (13), and / or

- an acceleration sensor (24) for measuring the acceleration of the resilient component and/or

- a position sensor (24) for measuring the distance to be covered by the resilient component, - wherein one or more, in particular all, of the aforementioned electrical components from the power supply (5) supplied with energy who the.

(buffer memory, reload:)

6. Spring assembly according to any one of the preceding claims, characterized in that

- The energy supply (5) has a buffer memory (15) for energy, which is supplied by the internal energy generator (14) or an external energy supplier, in particular by means of electromagnetic waves, in particular by a data query unit (51) come, is reloaded without contact,

- the external energy supplier is an RFID antenna, and/or

- the form of energy with which at least the load sensor (3) is operated and/or which is generated and possibly buffered is electric current and the buffer memory (15) for energy is a battery (15).

(Own energy production:)

7. spring assembly according to any one of the preceding claims, characterized in that

- either the spring assembly (1) comprises an energy generator (14) separate from the other electrical components mentioned

- or the load sensor (3) or the temperature sensor (9) or the transmitter unit (4) is designed in such a way that this component generates energy, in particular electrical current, through its operation,

- in particular by the energy generator (14) converting the expansion or movement or temperature of the resilient component (2) into energy,

- In particular by the energy generator (14) is a piezo element or a Peltier element. (Sender also receiver:)

8. spring assembly according to one of the preceding claims, characterized in that - the transmitter unit (4) is also designed to receive data, so as a transmitter / receiver unit (4) is formed.

9. Spring assembly according to one of the preceding claims, characterized in that - the transmitting unit (4) is an RFID tag or a passive transponder.

(functionally combined elements:)

10. Spring assembly according to any one of the preceding claims, characterized in that

- at least part of the conductor tracks (18) or current conductors of the RFID tag is simultaneously a load sensor (3) and/or an energy generator (4) and/or - at least part of the DMS is an energy generator (4) is.

11. Method for operating a spring assembly (1), with - a resilient component (2), in short a spring (2),

- a load sensor (3) operatively connected to the spring component (2),

- a transmitter unit (4)

- An energy supply (5) with an energy generator (14) and/or a contactless rechargeable energy store (15), in particular a battery (15), for example a spring assembly (1) according to one of the preceding claims, characterized in that - the load on the spring (2) is measured continuously or at regular intervals during operation, in particular only on request from the outside, in particular directly on the spring (2),

- the load measurement values are stored in a data memory (6),

- the load measurement values are sent wirelessly to a monitoring unit (50).

12. The method according to claim 11, characterized in that the load on the spring (2) is determined based on the deflection of the spring (2).

13. The method according to any one of the preceding method claims, characterized in that the energy-requiring components of the spring assembly (1) are operated by means of electric current.

(Power supply:)

14. The method according to any one of the preceding method claims,

- wherein the spring assembly (1) has a buffer store (15) for energy, in particular a battery (15), characterized in that the buffer store (15)

- Is recharged either contactless from the outside, in particular by means of electromagnetic radiation or induction shear

- And/or by means of an internal energy generator (14), which is part of the spring assembly (1), is recharged.

15. The method according to any one of the preceding method claims, characterized in that

- the load on the spring (2) is only measured on request from outside and/or the load measured values are sent to the query unit (51),

- in particular at least or only during the query from the query unit (51) to the transmission unit (4) energy is transmitted to this by means of electromagnetic radiation, in particular by means of radio waves,

- Electromagnetic radiation, in particular radio waves, is transmitted in particular more often than just during queries to the transmitting unit (4).

16. The method according to any one of the preceding method claims, characterized in that the bending or movement or the temperature of the spring (2) or the energy generator (14) is converted into energy, in particular electrical current, for internal energy generation.

17. The method according to any one of the preceding method claims, characterized in that

- The temperature of the spring (2) or the spring (2) surrounding the air is measured and/or ge

- the content of substances harmful to the spring (2) in the environment, in particular the air around the spring (2), is measured. and or

- the acceleration or the distance covered by the spring (2) is measured.

18. The method according to any one of the preceding method claims, characterized in that from

- the measured loads of the spring (2) and or

- From the pollutant content around the spring (2) and the exposure time and / or

- by measuring the elongation, particularly at the critical and/or most stressed points of the spring, and comparing these values with the stresses allowed for the specific material of the spring, comparing the deterioration of the spring, particularly both in terms of force as well as the remaining service life, is calculated by an evaluation unit (52), which can be part of the query unit (51), the remaining spring force and/or the probable remaining service life of the spring (2) is calculated and in particular is communicated to the operator via an output unit (50a) of the monitoring unit (50).

19. The method according to any one of the preceding method claims, characterized in that electrical conductor tracks (18) of the load sensor (3) also, in particular with a time delay for measuring the load on the spring (2), as an antenna of a transponder, in particular as an RFID -Antenna and orused for power generation.

20. The method according to any one of the preceding method claims, characterized in that

- The conductor tracks (18) of a strain gage are made of a semiconductor, in particular silicon, and are also used to generate electricity due to their piezo effect,

- In particular with a time delay to measure the load on the spring (2) with the DMS.