EP2291261A1

EP2291261A1 - Machine tool monitoring device

Info

Publication number: EP2291261A1
Application number: EP08874690A
Authority: EP
Inventors: Benjamin Visel; Georg Stellmann; Sebastian Jackisch
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-06-18
Filing date: 2008-12-09
Publication date: 2011-03-09
Also published as: RU2011101495A; DE102008002503A1; CN102066049A; RU2495319C2; US20110088528A1; JP5279900B2; WO2009152878A1; JP2011524263A

Abstract

The present invention relates to a machine tool monitoring device having a detecting unit (32) for detecting the presence of at least one type of material in at least one prescribed machine tool region, particularly the machine tool working region (34), by means of spectral analysis of radiation (S_R), wherein the detecting unit (32) comprises a sensor unit (44) having at least one sensitivity region (54.2) for detecting radiation in a wavelength range (WL₂) disposed in the electromagnetic range, a transmitting unit (42; 64) for transmitting radiation having at least one radiation component in the wavelength range (WL₂), and an analysis means (58) designed such that it can detect the presence of at least one type of material in at least one prescribed machine tool region based on the radiation detected by the sensor unit (44), wherein the analysis means (58) is operationally coupled to the transmitting unit (42).

Description

description

Title Machine tool monitoring device

The invention relates to a machine tool monitoring device according to the preamble of claim 1.

It is a machine tool monitoring device with a detection unit for material detection known.

Advantages of the invention

The invention relates to a machine tool monitoring device having a detection unit which is provided for detecting the presence of at least one type of material in a predetermined machine tool area, in particular machine tool working area, by means of the spectral evaluation of a radiation.

It is proposed that the detection unit has a sensor unit with at least one sensitivity range for radiation detection in a wavelength range which is arranged in the electromagnetic range, in particular at least partially in the infrared spectrum.

As a result, a reliable and rapid recognition of an application situation of a machine tool can be achieved cost-effectively.

A "region of a machine tool in the immediate vicinity of a tool is to be understood as meaning a region in the" direct "environment of the tool, in particular a region in which each point of the region has a smallest distance from the tool which is at most 10 cm, preferably at most 5 cm and particularly preferably at most 2 cm.

In this context, a "radiation" is to be understood as meaning, in particular, electromagnetic radiation .under a "spectrum" of a signal detected by the sensor unit Radiation should in particular be understood as a distribution of a radiation parameter, in particular the intensity of the radiation as a function of the wavelength, the frequency and / or the time. In addition, a "spectral evaluation" of a radiation is to be understood as a signal evaluation in which an evaluation result is obtained by detecting a characteristic of a spectrum of the radiation ,

In order to achieve an evaluation signal with high signal intensity, the detection unit comprises a transmission unit, which is intended to transmit radiation with at least one radiation component in the wavelength range.

In order to achieve a high degree of safety in the application of a machine tool, the detection unit further comprises an evaluation means which is adapted to detect the presence of at least one type of material in at least one predetermined machine tool area based on the radiation detected by the sensor unit. The at least one type of material is in particular human tissue. Of course, however, it is also possible to detect other types of material, for example materials to be processed and / or processed with the aid of the machine tool, materials of other objects, in particular glove materials, or the like, if so desired. Furthermore, different types of material can be distinguished from each other.

The evaluation means is operatively connected to the transmitting unit. In other words, the evaluation means can detect the presence of at least one type of material in at least one predetermined machine tool area both based on the radiation transmitted by the transmitting unit and based on the radiation detected by the sensor unit. By linking the transmitting unit and the receiving unit and by means of a temporal modulation (pulses) of the transmission signal and filtering this temporal modulation of the received signal, a compensation of the ambient light can also be advantageously achieved.

According to a preferred embodiment of the invention, it is proposed that the recognition unit be provided for detecting the presence by means of the evaluation of a reflection spectrum of a radiation reflected by an examination object, whereby an effective, based on a contrast detection detection of the type of material of the examination object can be achieved. The object under investigation may, as previously described, be previously mentioned, to act on human tissue, such as a hand, to manipulate and / or process items to be processed and / or processed by the machine tool, other items such as gloves worn by an operator, or the like.

A particularly reliable detection can be achieved if the wavelength range is a near-infrared range. As a result, a sensitivity range can be provided which is specifically matched to the detection and evaluation of a reflection spectrum. In this context, a "near-infrared range" should be understood as meaning, in particular, a wavelength interval of the infrared spectrum which is below the wavelength of 15 .mu.m. Furthermore, a high contrast between human tissue and a material can be achieved if the sensitivity range for detecting radiation in one In particular, it is advantageous if the wavelength range is a near infrared range A "near infrared range" should be understood in this context to mean, in particular, a wavelength interval of the infrared spectrum which is below the wavelength 1.5 μm is arranged, in particular a wavelength interval in the IR-A range. The wavelength range may also be partially arranged in the visible and / or ultraviolet region of the electromagnetic spectrum.

In a preferred embodiment of the invention it is proposed that the wavelength range is narrow-band. A "narrowband waveband" is to be understood in this context in particular a wavelength range which has a bandwidth of at most 100 nm, advantageously at most 50 nm and preferably at most 20 nm and particularly preferably at most 10 nm, with a bandwidth of 50 nm already very good results could be achieved, and thus it is advantageously possible to dispense with a design-intensive filtering of a detected radiation.

In a further embodiment of the invention, it is proposed that the transmitting unit is intended to transmit radiation in the wavelength range and in at least one further wavelength range. As a result, radiation can be generated in a targeted manner in desired wavelength ranges, it being possible to dispense with elaborate filtering when the radiation is detected by the sensor unit. Furthermore, a high signal-to-noise ratio can be achieved. This can be achieved in a particularly simple manner if the transmitting unit has at least two, in particular three, sensor modules for transmitting the radiation in each having a different wavelength range, which are operated during operation of the transmitting unit. The transmission can be carried out, for example, successively. A "successive" transmission in two wavelength ranges is to be understood in particular to mean that the transmission in the first wavelength range and the transmission in the second wavelength range are largely free of overlap, in which case an overlap duration in which radiation is transmitted simultaneously in both wavelength ranges should be less than 10%, advantageously less than 5%, and preferably less than 1%, of the smallest transmission duration in a wavelength range, the transmission processes being particularly advantageous without overlap, pulses being separated from one another by the transmission unit Alternatively, the transmitting unit may also have one or more transmitting diodes wherein each transmit diode is adapted to emit radiation in at least two distinct wavelength ranges.

It is also proposed that the machine tool monitoring device has an optical unit which is provided to define at least one reaction region of the detection unit. A "reaction area" of the recognition unit is to be understood as meaning, in particular, a spatial area which is assigned to a process which can be initiated by the recognition unit and which is triggered in the presence of a body of the at least one material type in this spatial area. For example, such a reaction area may also be used to implement a warning function of the machine tool monitoring device The optical unit can correspond to an optical system connected in the beam path of the sensor unit s Alternative correspond to a designed in the beam path of the transmitting unit optical system. By means of the optical unit, a safe and more comfortable application to the machine tool can be achieved by limiting a reaction of the recognition unit to a delimited area.

The ease of use can also be advantageously increased if the machine tool monitoring device has a marking unit that marks the at least one predetermined machine tool area or the at least one reaction area. Such a marking can take place, for example, by projection of laser light around the area to be marked. Alternatively, the marking can also be carried out in that a radiation component in the visible range is emitted by the transmitter unit in the direction of the area to be marked. Of course, other marking methods are conceivable.

Advantageously, the sensor unit has at least one further sensitivity range, which is provided for detecting radiation in a further wavelength range, whereby a further increased security in the recognition of the type of material can be achieved. The wavelength ranges may overlap. However, it is advantageous if the wavelength range is separated from each other. A particularly accurate detection can be achieved if the sensor unit has at least three sensitivity ranges which are each provided for detecting radiation in a different wavelength range.

In this context, it is proposed that the evaluation means be such that it can detect the presence of the at least one type of material on the basis of a ratio of at least two radiation parameters, which are each assigned a radiation component in a different wavelength range. As a result, rapid detection can advantageously be achieved. In particular, it can be dispensed with the consideration of a reference radiation. A "radiation parameter" is to be understood in particular to mean a parameter which is detected on the basis of a radiation incident on the sensor unit, which parameter may in particular be an electrical parameter.

Advantageously, a decision unit is provided, which is arranged such that it controls at least one actuator unit based on a detected presence or absence of the at least one type of material. The actuator unit may, for example, be a tool drive which is switched on or off based on the presence or absence of the at least one type of material in the monitored area. Also, the actuator unit may be a protection system that protects the operator from contact with a tool, such as a protection system that moves a tool out of a danger area, or a protection system that generates a warning signal to move the operator to a location to warn of imminent danger. The generated signal may be, for example, an optical, an acoustic or another warning signal.

Advantageously, the machine tool monitoring device comprises an activation and / or deactivation unit with the aid of which the machine tool monitoring system direction by a user can be switched on and / or off. This activation and / or deactivation unit is advantageously designed such that the extent in which it can be activated and / or deactivated by an operator depends on an authorization level of the user. Such authorization-dependent actuation of the activation and / or deactivation unit makes it possible to grant differently qualified users different rights. For example, a master may be authorized to completely disable the machine tool monitor, while a novice apprentice may not be granted rights to deactivate. Furthermore, it is conceivable, for example, for the reaction area to be increased or reduced in dependence on the authorization level of the user. The authorization level of the user can be stored on a portable medium, such as a chip card, a transponder or the like, wherein the storage medium is read to verify the level of authorization in a corresponding device and the level of authorization is checked. Depending on the detected authorization level, activation possibilities of the machine tool monitoring device with the activation and / or deactivation unit can then be enabled or disabled.

Furthermore, the present invention relates to a machine tool, in particular a cutting machine tool, such as a circular saw, a drill or the like, with a machine tool monitoring device of the type defined above.

Finally, the present invention relates to an article for use in handling a machine tool, which article is manipulated such that its material can be more easily detected by the tool master monitoring device. For example, the surface of the article may be coated with a material easily detectable by the machine tool monitoring device. The article is preferably a work glove worn by a user during operation of the machine tool.

Further advantages of the present invention will become apparent from the following description. In the drawings, embodiments of the invention are shown. The drawing, the description and the claims contain numerous features in combination. The person skilled in the art will expediently also consider the features individually and combine them into meaningful further combinations.

Show it: 1 shows a table saw with a detection unit,

FIG. 2 shows the table-top circular saw in a top view with a reaction region of the recognition unit;

FIG. 3 shows a schematic illustration of the recognition unit with a transmitting unit for transmitting a radiation into the reaction area, a sensor unit and an examination object,

4 shows a transmitting means of the transmitting unit and sensor means of the sensor unit in a

Front view.

Figure 5 shows the course of the transmission factor of the sensor unit in dependence of

Wavelength,

FIG. 6 shows the reflection spectrum of a radiation reflected by the reflection object as a function of the wavelength,

FIG. 7 shows an internal circuit of the recognition unit,

FIG. 8 shows a database stored in the recognition unit,

9 shows an alternative transmitting unit of the detection unit for generating pulses, and

FIG. 10 shows the intensity of a radiation generated by the transmitting unit from FIG.

Description of the exemplary embodiments

FIG. 1 shows a machine tool 10 designed as a table saw in a side view. The machine tool 10 has a tool 12 configured as a disk-shaped saw blade, which is rotationally driven in a sawing operation by means of a drive unit 16 arranged in a drive housing 14 and designed as an electric motor. Supported on the drive housing 14 is a saw table 18, on which a workpiece 20 to be machined can be placed. To protect an operator, the Machine tool 10, a protective cover 22 which surrounds the projecting out of the saw table 18 of the tool 12 in a non-powered state of the machine tool 10. To carry out a machining of the workpiece 20, this is moved in a known manner in a working direction 24 in the direction of the tool 12 by an operator, of which a hand 26 is shown schematically in the figure. Here, the guard 22, which is rotatably mounted about a rotation axis 28, pivoted by the workpiece 20 upwards, whereby the tool cutting edge is released.

To increase operator safety, the machine tool 10 is provided with a machine tool monitoring device 30. The machine tool monitoring device 30 has a recognition unit 32, which is provided for the presence detection of human tissue in a machine tool working area 34 of the machine tool 10. The machine tool working area 34 can be seen from above in FIG. 2 in a plan view of the machine tool 10. For the sake of clarity, the representation of the protective hood has been omitted in FIG. The recognition unit 32 has a reaction area 36 which is associated with the actuation of an actuator unit 38 coupled to the drive unit 16 and which is operatively connected to the recognition unit 32 (see FIG. 7). If the detection unit 32 detects the presence of human tissue in the reaction area 36, then an actuation signal is transmitted to the actuator unit 38, which causes the actuation signal to stop the drive unit 16 and to immediately decelerate the saw blade with the aid of an emergency brake device (not shown). The reaction area 36 corresponds to a partial area of the machine tool working area 34, which is arranged in front of the tool 12 in the working direction 24. It should be noted at this point, however, that the reaction area does not basically have to fall into a machine tool working area. Rather, a reaction area can be defined in any area. In the illustrated example, the detection unit 32 in the protective hood 22, in the working direction 24 in front of the tool 12 arranged front portion of the protective cover 22 is arranged. In an alternative embodiment, the detection unit 32 may be arranged on a splitting wedge, on a rip fence and / or on a boom above the saw table 18.

The functional principle of the recognition unit will be described with reference to FIG. The saw table 18, the workpiece 20 and the recognition unit 32 are shown in a schematic view. For the sake of clarity, the representation of the tool 12 and the guard 22 is dispensed with. On the workpiece 12 in the reaction region 36, an examination object 40 is arranged. This examination subject 40 can in particular the hand 26 be the operator. The detection unit 32 has a transmission unit 42, which is shown schematically in the figure, which transmits a radiation Si into the reaction area 36 during operation. This radiation Si is reflected by the examination object 40 and received as radiation S _R by a sensor unit 44 of the detection unit 32, which is shown schematically in FIG. The transmission unit 42 and the sensor unit 44 is preceded by an optical unit 46. The optical unit 46 has a lens unit (not shown) which defines the boundaries of the reaction area 36 in which the radiations Si are transmitted. The lens unit is further designed to limit the sensitivity of the sensor unit 44 to radiation S _R ZU reflected in the reaction area 36. The optical unit 46 has an optical axis 48. The machine tool monitoring device 30 further has a marking unit, which is shown schematically in FIG. 3 and, during operation of the recognition unit 32, marks the reaction area 36 of the recognition unit 32 by projection onto the saw table 18. For example, the marking unit 49 may be formed as a laser marker. Alternatively or additionally, the marking of the reaction region 36 can be carried out by the transmitting unit 42, which generates a radiation component in the visible range.

FIG. 4 shows the transmitting unit 42 and the sensor unit 44 of the recognition unit 32 in a front view, in which the optical axis 48 cuts through the plane of the drawing. The transmitting unit 42 has a transmitting means 50, which is designed as an LED. In the immediate vicinity of the transmitting means 50 four sensor means 52 of the sensor unit 44 are arranged, which are each designed as a photodiode.

The sensor means 52 each have a sensitivity range 54 which, for the detection of radiation, each in a different wavelength range WLi = [λi, λ ^], WL ₂ = [λ3, λ / i], WL ₃ = [λ ₅ , λβ] or WL ₄ = [λ ₇ , λg] is provided. This is shown schematically in FIG. FIG. 5 shows the course of the transmission factor of the sensor unit 44 as a function of the wavelength λ of the reflection radiation S _R received by the sensor unit 44. By way of example, the wavelength ranges WL ₁ have a central wavelength of 375 nm, 450 nm, 740 nm, 840 nm and 1550 nm and are narrow-band, each with a bandwidth of approximately 10 nm. The sensor unit 44 can be used for narrow-band filtering of the detected radiation S _{R be provided in} addition to the sensor means 52 with a system of filter components, which is upstream of the sensor means 52. In the embodiment of the sensor means 52 as selective photodiodes narrow-band filtering is inherent, whereby further filter components can be advantageously avoided. Alternatively or in addition to photodiodes, the sensor means 52 may be formed as CCD or CMOS arrays, InGaAs detectors, pyroelectric detectors, etc. The wavelength ranges WL ₂ , WL ₃ , WL ₄ are arranged in the infrared spectrum. In particular, these wavelength ranges WL ₂ , WL ₃ , WL _{4 are} each an area of the near infrared spectrum IR-A with the limit values [700 nm, 1500 nm]. The wavelength range WLi is at least partially arranged in the visible region of the electromagnetic spectrum. Alternatively or additionally, wavelength ranges in the infrared ranges IR-B (1.5-3 μm) and IR-C (3-15 μm) can be selected. The transmitting unit 42 with the transmitting means 50 generates a radiation which comprises the wavelength ranges WL ₁ shown in FIG.

The principle of the presence detection of human tissue in the reaction region 36 of the recognition unit 32 will be explained with reference to FIGS. 6, 7 and 8. FIG. 6 shows the reflection spectrum of the radiation S _R reflected by the examination object 40 and detected by the sensor means 52. This reflection spectrum corresponds to the distribution of the signal intensity as a function of the wavelength λ of the radiation S _R. The sensor means 52 and the sensitivity regions 54 each detect a part of the reflection spectrum in the corresponding wavelength ranges WL ₁ . The sensor means 52 generate at the output terminal in each case a radiation parameter V ₁ , which is in each case designed as an electrical voltage. The radiation parameter Vi, for example, is proportional to the signal intensity Si of the radiation S _R integrated over the wavelength range WL ₁ and hatched in FIG.

As can be seen from FIG. 7, the radiation characteristics V _{1 are} applied to an input of an evaluation means 58 of the recognition unit 32. In a further variant, it is conceivable that the radiation characteristics V _{1 are} amplified. In an evaluation, the radiation parameters V _{1 are} compared with values of a database 62 stored in a memory unit 60 of the recognition unit 32 by means of logical operations. This database is shown schematically in FIG. In a first evaluation strategy, the acquired radiation parameters V _{1 are} compared with stored values Ai, A ₂ , A ₃ , etc. Each pair (V ₁ , A ₁ ) is assigned a recognition variable which can assume the values "False" (F) or "True" (T). The value "F" precludes the presence of human tissue in the reaction area 36. In a second, alternative or additional evaluation strategy, the evaluation means 58 determines ratios Vi / V ₂ , Vi / V ₃ etc. between the different radiation parameters V ₁ . These ratios are compared with stored values Ai, A ₂ , A ₃ , etc., whereby, as described above, the presence of human tissue in the reaction area 36 can be inferred Memory unit 60 may also provide information about the Spectral sensitivity of the sensor means 52 may be stored, which can be used to evaluate the radiation characteristics V ₁ .

The detection unit 32 described here is an analog detection unit in which a detection or evaluation of the reflected radiation S _R takes place exclusively in an analogous manner. In this case, a particularly effective detection due to small acquisition or evaluation times can be achieved. A combined use of analog and digital signal processing means or the exclusive use of digital signal processing means is also conceivable.

The transmitting means 50 emits radiation having a constant intensity of radiation over time. In an alternative embodiment variant, the detection unit 32 has an alternative transmission unit 64 which transmits radiation with a variable intensity into the reaction area 36. This is shown in FIGS. 9 and 10. FIG. 9 shows the sensor unit 64 which generates a radiation Si which has a series of pulses 68 and is shown in FIG. FIG. 10 shows the course of the intensity of the radiation Si as a function of the time t. A pulse 68 has a width B of about 100 μs. The transmitting unit 64 is provided to transmit a radiation successively in the wavelength ranges WLi to WL ₄ . Here, in a sequence of four consecutive pulses 68.1 to 68.4, the pulses are each assigned to a different wavelength range WLi to WL ₄ . The pulses 68 correspond to a radiation which is transmitted in a respective different wavelength range WL ₁ . For this purpose, the transmitting unit 64 has a plurality of transmitting means 66.1 to 66.4 which are each provided for transmission in a different wavelength range WLi to WL ₄ . In this case, a transmission means 66.1 for the pulse 68.1 corresponds to the wavelength range WLi, etc. Alternatively, transmitting diodes may also be used which can each emit radiation in at least two of the wavelength ranges WL ₁ . The transmitting means 66 may be formed, for example, each as an LED. Such a successive blasting in different wavelength ranges WL ₁ makes it possible to dispense with complex filtering of the detected reflected radiation S _R. Thus, with the aid of the machine tool monitoring device 30, a reaction region 36 of the machine tool working region 34 can be monitored, which constitutes a danger zone of the machine tool 10 as a workpiece feed region. With the aid of the machine tool monitoring device, it is possible to distinguish human tissue from the materials to be machined with the aid of the machine tool 10, so that the saw blade of the machine tool 10 can be brought to a standstill immediately by means of the actuator unit 38 as soon as, for example, a user's hand 26 inside the machine Reaction region 36 with the help of the machine tool Monitoring device 38 is detected. As shown in FIG. 1, the machine tool comprises an activation and deactivation unit 70, which is operatively connected to the machine tool monitoring device 30. This activation and deactivation unit 70 is designed in such a way that the extent to which it can be confirmed by an operator depends on an authorization level of the user. For this purpose, the activation / deactivation unit 70 comprises a laser unit, not shown in detail, with the aid of which portable storage media on which authorization levels of operators are stored can be read out. Depending on the detected authorization level of the user, the user can activate or deactivate the machine tool monitoring device 30, possibly within predetermined limits. Such authorization-dependent actuation of the activation / deactivation unit 70 makes it possible to grant different rights to different users. For example, a master who has much experience in handling the machine tool 10 may be granted to completely disable the machine tool monitor 30 while not allowing such a deactivation to an inexperienced apprentice.

It should be understood that machine tool monitoring devices of the type described above may serve to monitor a variety of machine tools in which a user may / must intervene occasionally or regularly in the work process of the machine tool. Furthermore, the machine tool area, which can be monitored by means of a machine tool monitoring device according to the invention, is not limited to a machine tool working area in the vicinity of the tool. Rather, all machine tool areas can be monitored, from which a danger potential can emanate for the user.

Finally, it should be understood that the present invention is not limited to the embodiments described above. Rather, variations and changes are possible without departing from the scope of the present invention, which is defined by the appended claims.

Claims

claims

1. Machine tool monitoring device with a detection unit (32), which is provided for detecting the presence of at least one predetermined machine tool area, in particular machine tool working area (34), by means of the spectral evaluation of a radiation (S _R ), characterized in that the detection unit (32) a sensor unit (44) having at least one sensitivity range (54.2) for detecting radiation in a wavelength range (WL ₂ ) which is arranged in the electromagnetic range, a transmitting unit (42; 64) which is provided with radiation having at least one radiation portion in the wavelength range (WL ₂ ), and having an evaluation means (58) adapted to detect the presence of at least one type of material in at least one predetermined machine tool area based on the radiation detected by the sensor unit (44), the evaluation means (58) 58 ) is operatively connected to the transmitting unit (42).

2. Machine tool monitoring device according to claim 1, characterized in that the detection unit (32) for presence detection by means of the evaluation of a reflection spectrum of a research object (40) reflected radiation (S _R ) is provided.

3. Machine tool monitoring device according to claim 1 or 2, characterized in that the wavelength range (WL ₂ ) is arranged at least partially in the infrared spectrum.

4. Machine tool monitoring device according to claim 3, characterized in that the wavelength range (WL ₂ ) is a near-infrared or near infrared range.

5. Machine tool monitoring device according to one of the preceding claims, characterized in that the wavelength range (WL ₂ ) is formed narrow-band.

6. Machine tool monitoring device according to one of the preceding claims, characterized in that it comprises an optical unit (46) which is intended to define at least one reaction region (36) of the detection unit (32).

7. Machine tool monitoring device according to one of the preceding claims, characterized in that a marking unit is provided which marks the at least one predetermined machine tool area or the at least one reaction area.

8. Machine tool monitoring device according to one of the preceding claims, characterized in that the transmitting unit (64) is provided to transmit a radiation in the wavelength range (WL ₂ ) and in at least one further wavelength range (WLi, WL ₃ , WL ₄ ).

9. Machine tool monitoring device according to claim 8, characterized in that the transmission unit (64) has a plurality of transmission unit modules, wherein the transmission unit modules are such that each transmission unit module emit radiation in a different wavelength range (WLi, WL ₂ , WL ₃ , WL ₄ ) can.

10. Machine tool monitoring device according to claim 8, characterized in that the transmitting unit (64) has at least one transmitting diode, which is such that it can emit radiation in at least two mutually different wavelength ranges (WLi, WL ₂ , WL ₃ , WL ₄ ).

11. Machine tool monitoring device according to one of claims 8 to 10, characterized in that the sensor unit (44) has at least one further sensitivity range (54.1, 54.3, 54.4) provided for detecting radiation in a further wavelength range (WLi, WL ₃ , WL ₄ ) is.

12. Machine tool monitoring device according to one of claims 8 to 11, characterized in that the evaluation means (58) of the detection unit (32) is such that it detects the presence of the at least one type of material based on a ratio of at least two radiation parameters (V ₁ , V ₂ , V ₃ , V ₄ ), each associated with a radiation component in a different wavelength range (WLi, WL ₂ , WL ₃ , WL ₄ ).

13. Machine tool monitoring device according to one of the preceding claims, characterized in that a decision unit is provided which in such a way is that it controls at least one actuator unit (38) based on a detected presence or absence of the at least one type of material.

14. Machine tool monitoring device according to one of the preceding claims, characterized in that it has an activation and / or deactivation unit (70) for activating and / or deactivating the machine tool monitoring device by a user.

15. A machine tool monitoring device according to claim 14, characterized in that the activation and / or deactivation unit (70) is designed in such a way that the extent to which the machine tool monitoring device can be activated and / or deactivated by an operator with the aid of an authorization level depends on the user.

16. Machine tool, in particular cutting machine tool, with a machine tool monitoring device according to one of the preceding claims.

17. An article for use on a machine tool according to claim 16, characterized in that it is manipulated such that its material can be more easily detected by the machine tool monitoring machine.

18. An article according to claim 17, characterized in that its surface is coated with a material easily to be detected by the machine tool monitoring device.

19. The article of claim 17 or 18, characterized in that this is a work glove.