DE102012024591A1 - Device for measuring electrostatic charges on dielectric materials, has sensor with sensor surface, where movement of material conveyor partially screens or weakens electric field between dielectric material and sensor surface - Google Patents

Abstract

The device has a sensor with a sensor surface, which determines the electric field coming from the dielectric materials and has no modulation device for periodic screening or weakening of the electric field. The movement of the material conveyor partially screens or weakens the electric field between the dielectric material and the sensor surface. The sensor surface is placed in the casing (101) of a rotating roller (100). The displacement current influenced by the electric field in the sensor surface is measured and a signal processing is conducted.

Description

The invention relates to a device for measuring electrostatic charges on moving dielectric materials.

It is desirable in many cases to know the level of electrostatic charge on a dielectric material.

One reason for this is that such charges can often lead to unwanted effects such as dust attraction, sticking together of the materials or even destruction of electrostatically sensitive components.

In potentially explosive atmospheres, electrostatic charges are a dreaded source of ignition.

On the other hand, there are many applications in which targeted electrostatic charging is desired, for example, to electrostatically adhere materials.

By measuring and detecting an electrostatic charge, the effectiveness of an existing electrostatic discharge device can be checked, furthermore, both discharge and charge devices can be controlled or regulated by a measurand to improve the result.

There are known sensors for measuring electrostatic charges in various designs.

Common to these sensors is that the electric field emanating from an electrostatic charge in a conductive sensor surface causes a charge shift by influence.

This charge shift is measured and evaluated.

For continuous measurements, the electric field must be modulated to eliminate errors due to unavoidable leakage currents of the sense amplifier.

For example, field mills ( GB2 010 493 A ), which alternately interrupt and let pass the electric field to be measured on the sensor surface by means of a rotating impeller.

The impeller is usually powered by an electric motor that wears and requires regular maintenance.

In US 2008 0129302 A1 a micromechanical sensor is introduced, which covers and releases the sensor surface via a laterally moving shield.

On the one hand, these sensors are difficult to produce and, on the other hand, due to their moving mechanics they are very sensitive to soiling, as they frequently occur in production plants, and are therefore only conditionally suitable for continuous use.

The object of the present invention is the development of a simple, robust and cost-effective device for measuring electrostatic charges on moving dielectric materials.

This object is achieved by a device according to claim 1.

Further features of the invention are contained in the subclaims.

The invention will be described below with reference to preferred embodiments. Reference is made to the accompanying drawings.

1 to 5 show a first preferred embodiment of the invention, 1 the complete arrangement, 2 the arrangement without roll shell, 3 the side view with open sensor and 4 the side view with covered sensor, 5 the sensor in detail.

There are two sensors ( 200 ), consisting of sensor surface ( 203 ), insulating sensor housing ( 201 ) and signal conditioning electronics ( 202 ) is integrated into a roller for impedance conversion, amplification and filtering of the displacement current received by the sensor surface.

The roll shell ( 101 ) is over two camps ( 104 ), of which only one is shown, movable on a rigid axis ( 103 ), in the roll shell ( 101 ) there are two openings ( 102 ), which during a rotation of the roll mantle ( 101 ) the sensor surfaces ( 200 . 203 ) periodically cover and release.

In the promotion of a web-like material ( 300 ) over the roller ( 100 ), the roller is oriented so that the sensor ( 200 ) into one of the material ( 300 ) shows a looped area. During a movement of the material ( 300 ) in the direction ( 301 ) the roll shell ( 101 ) in the direction of rotation ( 106 ) and rotate the sensor surfaces ( 200 . 203 Cover and periodically through the Openings ( 102 ). It is irrelevant whether the roller is actively driven or the rotation alone by the friction between roll shell ( 101 ) and material ( 300 ) comes about. The signals processed by the signal conditioning electronics are transmitted through connecting cables ( 400 ) led to the outside and in a signal processing ( 500 ) converted into field strength and surface tension values using previously determined calibration data, displayed and output via an interface. Due to the known geometry of the arrangement, it is possible to determine the polarity in addition to the height of the charge.

The power supply of signal processing and sensor is not shown. In further embodiments of this first preferred embodiment of the invention are in the direction of rotation of the roll shell ( 101 ) several openings ( 102 ) to allow several measurements per revolution.

Furthermore, transversely to the web running direction ( 301 ) fewer or more sensors ( 200 ) so as to have a charge profile transverse to the direction of web travel ( 301 ) to be able to record.

The 6 to 8th show a second preferred embodiment of the invention.

In this training there are two sensors ( 200 ) directly in the rotating roll shell ( 101 ), the sensor signals are transmitted via a rotary feedthrough ( 600 ) from the rotating roll shell ( 101 ) on the fixed roll axis ( 103 ) and signal processing as in the first embodiment of the invention described above.

Through the roll rotation when conveying a web-like material ( 300 ) in web running direction ( 301 ) is the sensor ( 200 ) periodically below the conveyed material ( 300 ), as in 7 represented, or with respect to a grounded reference surface ( 107 ).

In further embodiments of this second preferred embodiment of the invention are in the direction of rotation of the roll shell ( 101 ) several sensors ( 200 ) to allow several measurements per revolution.

Furthermore, transversely to the web running direction ( 301 ) fewer or more sensors ( 200 ) so as to have a charge profile transverse to the direction of web travel ( 301 ) to be able to record.

The 9 to 11 show a third preferred embodiment of the invention.

In this training is a sensor ( 200 ) below a chain of electrically conductive gripper rails ( 700 ), which is an arcuate material ( 800 ) between gripper upper part ( 701 ) and gripper lower part ( 702 ) and in the material direction ( 900 ).

The gripper rails are attached to a revolving chain, which is not shown. Due to the movement of the gripper rails in the material direction, the sensor is ( 200 ) periodically below the conveyed material ( 800 ), as in 11 represented, or opposite the gripper rail ( 700 ), as in 10 shown. The gripper rail is grounded via the circulating chain (not shown) and therefore represents a reference surface for the sensor.

In further embodiments of this third preferred embodiment of the invention are in the direction of movement ( 900 ) of the gripper rails ( 700 ) several sensors ( 200 ) to allow multiple simultaneous measurements.

Next, transverse to the direction of movement ( 900 ) several sensors ( 200 ) so as to have a charge profile transverse to the direction of movement ( 900 ) to be able to record.

The 12 and 13 show a fourth preferred embodiment of the invention. Below an electrically conductive and grounded conveyor belt ( 1000 ) with several openings ( 1001 ) there is a sensor ( 200 ).

On the conveyor belt ( 1000 ) are the subsidized materials ( 1100 ) whose charge is to be determined. Size and number of openings are chosen so that the materials on the conveyor cover some of the openings.

The sensor ( 200 ) is placed below these openings.

During movement of the conveyor belt ( 1000 ) in the direction ( 1200 ) the sensor ( 200 ) alternately the material engaging through the opening electric field and the reference potential of the grounded conveyor belt ( 1000 ) take up.

In further embodiments of this fourth preferred embodiment of the invention, a dielectric conveyor belt is provided with conductive, grounded segments instead of an electrically conductive conveyor belt.

Next, transverse to the direction of movement ( 1200 ) several sensors ( 200 ) so as to be able to measure a plurality of juxtaposed materials.

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• GB 2010493 A [0011]
• US 20080129302 A1 [0013]

Claims (9)

Apparatus for measuring electrostatic charges on dielectric materials moved by a material conveyor comprising at least one sensor having at least one sensor surface which detects the electric field emanating from the dielectric material and has no modulation device integrated into the sensor for periodically shielding or attenuating the electric field, characterized in that the movement of the material conveyor periodically at least partially shields or attenuates the electric field between the dielectric material and the sensor surface. Apparatus according to claim 1, characterized in that at least one sensor surface is placed in the interior of a rotating and at least partially electrically conductive roller with at least one opening in the roll shell. Apparatus according to claim 1, characterized in that at least one sensor surface is placed in the shell of a rotating roller. Apparatus according to claim 1, characterized in that at least one sensor surface is placed on the material side facing away from an at least partially conductive conveyor belt with at least one opening. Apparatus according to claim 1, characterized in that at least one sensor surface is placed on the moving material and at least partially conductive elements of the material conveyor are periodically at least in a part of the gap between sensor and material. Device according to one of the preceding claims, characterized in that the induced by the electric field in the sensor surface displacement current is measured and fed to a signal processing. Apparatus according to claim 6, characterized in that the caused by the movement of the material conveyor periodic fluctuation of the measuring signal detected, evaluated in a signal processing and used to determine the zero point and polarity of the measuring signal. Apparatus according to claim 6 or 7, characterized in that the measurement signal in the signal processing with the aid of stored correction and or calibration values in field strength and / or surface tension values is converted. Apparatus according to claim 8, characterized in that the field strength and / or surface tension values are displayed and / or output via a data interface.

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