GB2472674A

GB2472674A - Tool vibration monitor

Info

Publication number: GB2472674A
Application number: GB1011631A
Authority: GB
Inventors: Martin Sinner-Hettenbach; Michael Mahler
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2009-08-14
Filing date: 2010-07-09
Publication date: 2011-02-16
Anticipated expiration: 2030-07-09
Also published as: DE102009028547B4; GB2472674B; DE102009028547A1; GB201011631D0

Abstract

A device for determining the vibration exposure of a person 1 who is exposed to mechanical vibrations as a result of the operation of a tool 2 comprises a measuring and transmission device 4 arranged on the tool and a receiving and evaluation device 5, to which a vibration value can be transmitted (e.g. by radio waves 6) for the purpose of evaluation. The receiving and evaluation device 5 has an additional vibration measuring unit. The evaluation device 5 checks whether the vibration value from the measuring and transmission device 4 correlates with the vibration value from the additional vibration measuring unit. This ensures unambiguous assignment between the transmission device 4 and the receiving device 5 so that the correct vibration value is evaluated by device 5, especially in an environment where there is a plurality of tools each with vibration monitors.

Description

Description Title

Vibration determination device for ascertaining the vibration exposure of persons The invention relates to a vibration determination device for ascertaining the vibration exposure of persons, according to the preamble of Claim 1.

Prior art

Known from DE 10 2007 014 894 Al is a vibration dosimeter for ascertaining the vibration exposure of persons who are exposed to mechanical vibrations as a result of the operation of a tool such as, for example, a drill. The vibration dosimeter comprises a measuring device, which is arranged on the tool and which serves to ascertain the operating state of the tool. Additionally provided is an evaluation device, which is carried by the user and which communicates wirelessly with the measuring device. In the evaluation device, a current, cumulative exposure value can be compared with defined limit values, in order to ascertain the vibration exposure of the operator.

According to an embodiment variant described in DE 10 2007 014 894 Al, there is assigned to the measuring device a piezoelectric element, in which the vibrations generated by the tool are converted to an electrical voltage, which is used to supply electric power to the components in the measuring device.

If a variety of tools are used alternately by the operator, for example angle grinders of differing sizes, a straight grinder or a pneumatic hammer, it must be ensured that the cumulative exposure of the operator concerned is measured correctly. The problem of assignment is aggravated further, in particular, for the case where several persons use differing tools alternately.

Disclosure of the invention

The invention is based on the object of ascertaining, through simple means and with high reliability, the vibration exposure of persons who are exposed to mechanical vibrations as a result of the operation of a tool.

This object is achieved, according to the invention, through the features of Claim 1. The dependent claims specify expedient developments.

The vibration determination device according to the invention serves to ascertain the vibration exposure of persons who are exposed to mechanical vibrations as the result of the operation of a tool. The vibration determination device comprises a measuring and transmission device, which is to be arranged on the tool and which is used, on the one hand, to ascertain tool vibrations and, on the other hand, to transmit a vibration value.

Furthermore, there is assigned to the vibration determination device a separately realized receiving and evaluation device, to which the vibration value, determined in the measuring and transmission device, can be transmitted for the purpose of evaluation. The receiving and evaluation device furthermore comprises an additional vibration measuring unit, in which, likewise, a vibration value can be ascertained. In the receiving and evaluation device, it is checked whether there is a correlation between the vibration value that originates from the measuring and transmission device on the tool and the vibration value from the additional vibration measuring unit assigned to the receiving and evaluation device.

By means of the vibration determination device according to the invention, unambiguous assignment is achieved between the measuring and transmission device and the associated receiving and evaluation device. This has advantages, in particular, for the case where the vibration value is transmitted wirelessly, for example by radio, from the measuring and transmission device to the receiving and evaluation device. The correlation between the vibration values in the measuring and transmission device, on the one hand, and in the measuring and transmission device, on the other hand, provides for unambiguous assignment. It is thereby ensured, in particular, that the correct vibration value is considered in the receiving and evaluation device, even when a plurality of tools having respectively assigned measuring and transmission devices, each of which transmit vibration values, are in operation simultaneously in a confined space. The risk of inadvertent evaluation of a vibration value from a tool not assigned to the operator in question is precluded, or at least reduced significantly.

The evaluation value ascertained by the measuring and transmission device undergoes evaluation in the receiving and evaluation device. In this case, in particular, the cumulative vibration exposure of the respective operator is determined, in order to prevent inadmissible exceeding of a limit value.

In principle, differing types of vibration values can be transmitted and evaluated. For example, vibrations ascertained by sensor in the measuring and transmission device on the tool can be transmitted directly and compared, in the receiving and evaluation device, with vibration values of the same type acquired in the vibration measuring unit there. In the case of this embodiment, the signals exchanged and compared with one another are the frequency, the amplitude, the phase shift and, if appropriate, the signal strength. In the case of a correspondingly high correlation between the vibration signals emitted by the tool and the vibration signals that are ascertained in the further vibration measuring unit of the receiving and evaluation device, an exposure characteristic value can be ascertained cumulatively in the receiving and evaluation device. One or more of the characteristic quantities signal strength, phase shift, frequency and amplitude can be taken into account.

According to a further expedient embodiment, only the commencement of a vibration exposure is taken into account as a vibration value upon a tool being put into operation.

In this embodiment, the commencements of a vibration exposure is in each case determined both via the vibration measuring unit of the measuring and transmission device on the tool and in the vibration measuring device in the receiving and evaluation device, and a correlation, or association, is deduced from a technically caused time delay between the commencement of the respective vibration exposure. The technically caused time delay preferably relates to the signal sensed in the measuring and transmission device, the delay being caused, for example, in that a signal is ascertained only in cyclic, predefined time segments. If the interval of time between the commencement of the vibration signal in the receiving and evaluation device, on the one hand, and the vibration signal in the measuring and transmission device, on the other hand, is of a defined quantity, a correlation can be assumed. In this case, in particular, a time window is predefined, within which the time delay must occur.

The time delay can also be caused in that energy originating from the vibration of the tool is stored intermediately in an electrical storage element in the measuring and transmission device, and a vibration value is transmitted only when the stored and cumulated vibration energy, in the form of electrical energy, exceeds a limit value. Finally it is also possible for vibration values to be transmitted only in the case when the generated vibration energy, or vibration strength, in the measuring and transmission device exceeds a limit value; in this case, it is possible to dispense with a storage element.

In the aforementioned cases, there is produced in each case a time delay that is made the basis of an assignment between the respective measuring and transmission device and the associated receiving and evaluation device.

The aforementioned method of operation has the advantage, moreover, that there is no need for vibrations to be transmitted as a vibration value, but that it is sufficient, in principle, to transmit a tool-specific or, if appropriate, also an operating-mode specific vibration characteristic value as a vibration value. The individual vibration exposure can be ascertained cumulatively from the level or type of the vibration characteristic value and from the duration of the existing vibrations.

Irrespective of the nature of the respective vibration value to be transmitted between the measuring and transmission device and the receiving and evaluation device, the vibration exposure is also rendered cumulatively in the case of changing between differing tools.

Possible, in principle, are both embodiments in which vibration values of the same type are ascertained in the respective vibration measuring units and are correlated with one another, and embodiments with differing types of vibration values, insofar as a correlation exists. A differing vibration value type exists, for example, if the commencement of a vibration is registered in the vibration measuring unit in the receiving and evaluation device and the vibration value originating from the measuring and transmission device renders the typical vibration parameters such as frequency, amplitude, phase shift or signal strength.

According to a further expedient embodiment, the measuring and transmission device can be combined with an electric-power supply unit, which is fed from the vibrations of the tool. In this embodiment (energy harvester), the measuring and transmission device obtains the electrical energy from the mechanical vibrations of the tool and, moreover, advantageously, does not require any additional electrical energy. The electric-power supply unit that is fed via the mechanical vibration is, in particular, a piezoelectric element, in which a mechanical vibration generates a voltage. This electrical voltage can be used to charge a storage unit, in particular a capacitor and, if appropriate, also a battery. As soon as the storage unit has been supplied with sufficient electrical energy, the vibration value is transmitted; the charging period of the storage unit in this case is registered as a time delay in the receiving and evaluation device. The charging duration is usually a tool-specific characteristic value.

Further advantages and expedient embodiments are given by the further claims, the description of the figures and the drawings, wherein: Fig. 1 shows a schematic representation of a hand tool, held by an operator, having a vibration determination device for ascertaining the vibration exposure of the operator, consisting of a tool-side measuring and transmission device and a receiving and evaluation device carried by the operator, Fig. 2 shows a schematic representation of a circuit, which is a constituent part of the measuring and transmission device, Figs. 3 to 5 show further circuit embodiments of the measuring and transmission device.

In the figures, components that are the same are denoted by the same references.

As can be seen from Fig. 1, the hand tool 2, for example a drill, is held by an operator 1, who is subjected to vibration exposure during operation of the hand tool. The vibration exposure is ascertained by means of a vibration determination device 3, which has a two-part structure and comprises a measuring and transmission device 4, on the hand tool 2, and a receiving and evaluation device 5, which is carried by the operator 1. The devices 4 and 5 are made so as to be separate from one another, and communicate wirelessly with one another via radio waves 6. Both the measuring and transmission device 4 and the receiving and evaluation device 5 each have a vibration measuring unit for measuring vibrations emitted by the hand tool 2 during operation.

Expediently, the measuring and transmission device 4 is detachably fastened to the housing of the hand tool 2, for example by means of magnets or through positive fit-on or the like. The measuring and transmission device 4 is preferably realized so as to be autonomous in respect of energy arid not dependent on the energy supply of the hand tool 2. Preferably, energy is supplied to the measuring and transmission device 4 via an autonomously operating electric-power supply unit, which preferably generates electrical energy from the vibrations of the hand tool 2.

In particular, in this case it is possible for the electric-power supply unit to be realized as a piezoelectric element.

Complementing the autonomously operating electric-power supply unit, or as an alternative thereto, the electric power supply can also be effected via batteries, or storage batteries. In principle, however, a connection to the electrical energy supply of the hand tool 2 is also possible.

The following description of the figures relates to an embodiment of the measuring and transmission device 4 having an autonomously operating electric-power supply unit, preferably realized as a piezoelectric element, that is fed from the vibrations of the tool.

For the purpose of ascertaining the vibration exposure while, at the same time, assigning unambiguously between a measuring and transmission device 4 and an associated receiving and evaluation device 5, vibration values are in each case ascertained in the vibration measuring units both in the measuring and transmission device 4 and in the receiving and evaluation device 5, the vibration value from the measuring and transmission device 4 being transmitted, via the radio waves 6, to the receiving and evaluation device 5, and evaluated therein. There are thus available in the receiving and evaluation device 5 two vibration values, which have been ascertained via independent vibration measuring units and which can be related to one another according to a predefined specification. The vibration values correlate with one another in a predefined manner, which can be determined in the receiving and evaluation device 5. Consequently, correct assignment is possible between the vibration values from the measuring and transmission device 4 that are transmitted wirelessly via radio waves 6 to the receiving and evaluation device 5, in which a cumulated vibration exposure of the operator 1 can be ascertained and displayed.

-10 -A circuit 7, which is a constituent part of the measuring and transmission device 4, is represented in Fig. 2. The circut 7 comprises a piezoelLectric element 8, which is made to vibrate by the vibrations of the hand tool 2, and thereupon generates a electrical voltage, in accordance with the piezoelectric effect. The electrical energy generated by the piezoelectric element 8 is used to transmit a vibration value. For this purpose, a direct-current voltage, by means of which a capacitor 10 is charged, is first generated in a rectifier 9 that is connected in circuit after the piezoelectric element 8. A resistor 11 is connected in parallel to the capacitor 10, it being possible to use the capacitance of the capacitor and the discharge resistance of the resistor 11 to set the vibration effect above which the vibration value is to be transmitted. For this purpose, the circuit 7 has, as a

voltage-controlled circuit element, a field-effect

transistor 12, which is arranged in an electrical circuit together with a transmission coil 13 and an assigned transmission circuit 14, the transmission coil 13 and the transmission circuit 14 being part of an RFID (radio frequency identification) circuit. Upon attainment of a particular threshold voltage, the RFID circuit is activated via the field-effect transistor 12, whereupon a vibration value can be read out via the transmission coil 13. The circuit 7 according to Fig. 2 thus serves to provide a vibration value upon attainment of a particular vibration intensity. The piezoelectric element 8 in this case also acts as a vibration measuring unit, in addition to its energy-generating function.

In the exemplary embodiment according to Fig. 3, in comparison with Fig. 2, a transmission module 15 is -11 provided instead of a transmission circuit, via which transmission module a radio signal is emitted in dependence on the generated energy and picked up by the measuring and transmission device 4.

Likewise, in the exemplary embodiment according to Fig. 4, transmission of an ascertained vibration value is effected by means of a transmission module 15. However, a vibration value corresponding to the generated energy is first stored intermediately in a storage element 16, which vibration value is transmitted at a subsequent point in time via the transmission module 15.

In the exemplary embodiment according to Fig. 5, a supply voltage 17 for the transmission module 15 is generated at regular intervals of time via a corresponding circuit, which transmission module emits a radio signal to the measuring and transmission device at corresponding intervals of time.

In the case of the aforementioned embodiments of the circuits, which are a constituent part of the measuring and transmission device 4, there is transmitted, expediently, as a vibration value, a tool-specific or, if appropriate, also an operating-mode specific vibration characteristic value that is typical of the respective hand tool, or of the respective operating mode of the hand tool, respectively. The vibration characteristic value can be read out directly from the hand tool and transmitted via the measuring and transmission device, in which case a corresponding communication device is required between an electronic component of the hand tool and the measuring and transmission device 4. It is also possible, however, for a -12 -vibration characteristic value to be generated from the type of vibrations generated in the hand tool, which vibrations are measured via the vibration measuring unit in the measuring and transmission device 4.

The vibrations of the hand tool are also registered in the vibration measuring unit that is a constituent part of the receiving and evaluation device 5 carried by the operator.

The association between the measuring and transmission device and the receiving and evaluation device can be deduced from the time delay that occurs between the commencement of a registered vibration in the receiving and evaluation device and the commencement of a registered vibration in the measuring and transmission device. The time delay occurs, as described in Figures 2 to 5, for technical reasons, as a result of the vibration value being transmitted, or provided, cyclically, or as a result of being transmitted, or provided, upon attainment of a threshold value in respect of the strength of the vibrations, or as a result of being transmitted, or provided, following attainment of a particular energy potential, or charge state, in the electrical storage element.

This assignment between the measuring and transmission device and the receiving and evaluation device by means of the time delay is effected with sufficient accuracy, in that a time window, which must be between the commencement of the respective signals, is defined for the delay.

However, in order to preclude confusion with other measuring and transmission devices in the proximity of the receiving and evaluation device, it can be expedient to take account of an additional correlation criterion, for -13 -example the signal strength, the frequency, the amplitude or the phase shift.

Claims

-14 -Claims 1. Vibration determination device for ascertaining the vibration exposure of persons who are exposed to mechanical vibrations as a result of the operation of a tool, comprising a measuring and transmission device (4), to be arranged on the tool (2), for ascertaining tool vibrations and for transmitting a vibration value, and comprising a receiving and evaluation device (5), to which the vibration value can be transmitted for the purpose of evaluation, characterized in that the receiving and evaluation device (5) additionally comprises a vibration measuring unit, it being possible to check in the receiving and evaluation device (5) whether the vibration value from the measuring and transmission device (4) correlates with a vibration value ascertained in the additional vibration measuring unit.
2. Vibration determination device according to Claim 1, characterized in that a defined time delay, between the vibration value ascertained in the additional vibration measuring unit and the transmitted vibration value, is considered as a correlation.
3. Vibration determination device according to Claim 2, characterized in that the time delay occurs within a defined time window.
4. Vibration determination device according to Claim 2 or 3, characterized in that the vibration value is a vibration characteristic value.-15 -
5. Vibration determination device according to any one of Claims 1 to 4, characterized in that the tool-side measuring and transmission device (4) has an electric-power supply unit that is fed from the vibrations of the tool (2)
6. Vibration determination device according to Claim 5, characterized in that the electric-power supply unit comprises a piezoelectric element (8)
7. Vibration determination device according to Claim 5 or 6, characterized in that an electrical storage element (9, 16), which can be charged via the electric-power supply unit, is provided.
8. Vibration determination device according to any one of Claims 2 to 4 and 6, characterized in that the time delay between the vibration value ascertained in the additional vibration measuring unit and the transmitted vibration value can be ascertained from the charging duration of the electrical storage element (9, 16)
9. Vibration determination device according to any one of Claims 1 to 8, characterized in that both the measuring and transmission device (4) and the receiving and evaluation device (5) comprise acceleration sensors, the signal strength, the phase shift, the frequency and/or the amplitude between the measurement signals of the accelerations sensors being considered for the purpose of determining the correlation.-16 -
10. Vibration determination device according to any one of Claims 1 to 9, characterized in that, in the case of a correlation having been determined, the vibration exposure is registered cumulatively in the receiving and evaluation device (5)
11. Method for operating the vibration determination device according to any one of Claims 1 to 10, characterized in that a vibration value is transmitted if the generated vibration energy in the measuring and transmission device (4) exceeds a limit value.
12. Method for operating the vibration determination device according to any one of Claims 1 to 11, characterized in that the generated vibration energy is stored intermediately in the storage element (9, 16) , arid a vibration value is transmitted if the stored and cumulated vibration energy exceeds a limit value.
13. Method for operating the vibration determination device according to any one of Claims 1 to 12, characterized in that a vibration value is transmitted in predetermined intervals of time.
14. Vibration determination device substantially as herein described with reference to the drawings anddescription.