Patent ID: 12259316

DETAILED DESCRIPTION

The present disclosure relates to a cleaning device1for cleaning an outer portion3of a sensor5which is in contact with a medium during measuring mode, for measuring a measured variable of the medium, a measuring device comprising the sensor5and the cleaning device1, and a cleaning method, which can be carried out by means of the cleaning device1.

The cleaning device1can be used especially in conjunction with sensors5which are designed to carry out measurements of the measured variable via or through the outer portion3in contact with the medium during measuring mode. In this respect, the sensor5is, for example, an optical sensor, a photometer or a spectrometer, the outer portion3of which comprises at least one window7transparent to electromagnetic radiation, through which electromagnetic radiation used for measuring the measured variable passes. Examples thereof are calorimetric sensors, turbidity sensors, sensors for measuring a spectral absorption coefficient of the medium, as well as sensors for measuring a concentration of an analyte contained in the medium, such as, for example, sensors for measuring a nitrite content, a nitrate content or an ammonium content.

FIG.1shows an example of a measuring device in which the sensor5comprises a recess9which is open towards the environment, such as a measuring gap for receiving the medium. The outer portion3of the sensor5to be cleaned comprises two windows7arranged opposite one another on both sides of the recess9, through which windows7the measured variable is measured. For this purpose, the sensor5comprises, for example, a radiation source13arranged on one side of the recess9, for example a light source, by means of which radiation is transmitted through the adjoining window7, the medium located in the recess9, and the opposite window7to a detector15during the measuring mode. In this case, the measured variable is determined and output, for example, by means of a measuring electronics17connected to the detector15.

FIG.2shows a further measuring device in which the outer portion3of the sensor5to be cleaned comprises a window11arranged on an outer side, for example, an end face, of the sensor5. In this variant, the radiation source13transmits electromagnetic radiation through the window11into the medium in the measurement mode and the detector15receives electromagnetically radiation reflected or scattered by the window11in the direction of the detector15after interaction with the medium. The measured variable is also determined and output here, for example, by means of a measuring electronics unit17connected to the detector15.

However, the use of the cleaning device1is not limited to sensors operating with electromagnetic radiation, such as optical sensors operating for example with ultraviolet or infrared light. The cleaning device1can also be used analogously for cleaning other sensors, such as ultrasonic sensors or conductivity sensors. In conductivity sensors, the outer portion to be cleaned comprises, for example, at least one electrode surface.

The cleaning device1comprises a pump19which is connected on the input side to a supply line21serving as an air supply line and is connected on the output side to a pressure accumulator27via a discharge line23. The pressure accumulator27is arranged in a housing25of the cleaning device1which can be mounted or is mounted on the sensor5and is connected via an exhaust air duct31of the cleaning device1, which is equipped with a pressure-controlled valve29, to at least one nozzle33which is respectively aligned or can be aligned on the outer portion3of the sensor5to be cleaned. The pressure-controlled valve29is preferably a check valve. Alternatively, the pressure-controlled valve29can also comprise a control slide. A flat jet nozzle is especially suitable as the nozzle33.

The cleaning device1is designed to perform a cleaning method in which at least one cleaning operation is performed in each case. Each cleaning process comprises at least one pressure-surge cleaning. In each pressure-surge cleaning, air sucked in via the feed line21is compressed by means of the pump19in the pressure accumulator27, and at least a portion of the compressed air produced in this way in the pressure accumulator27is ejected in the form of a pressure surge via the nozzle(s)33connected to the exhaust air duct31when pressure exerted by the compressed air enclosed in the pressure accumulator27on the pressure-controlled valve29exceeds a pressure value required for opening the pressure-controlled valve29. Due to the output of the pressure surge, the pressure in the pressure accumulator27decreases abruptly. This leads to the fact that the pressure-controlled valve29automatically closes again and, in the pressure accumulator27, a pressure can again be built gradually by means of the pump19and a further pressure-surge cleaning can be performed.

The present disclosure has the above-mentioned advantages. Optionally, individual components of the cleaning device1, the measuring device comprising the cleaning device1and/or the cleaning method that can be executed by means of the cleaning device can each have different configurations. Some currently especially preferred examples thereof are listed below.

Since the pressure in the pressure accumulator27can be built up gradually by means of the pump19, a pump with low power, for example a power of 1 watt, is already sufficient to generate a high pressure in the pressure accumulator27, such as, for example, a pressure of up to 3 bar. The correspondingly small size of the pump19offers the advantage that the cleaning device1can be designed as a compact device in which the pump19and the pressure accumulator27are arranged in the housing25of the cleaning device1.

This compact embodiment shown inFIGS.1and2offers the advantage that the pump19, the pressure accumulator27and the nozzle(s)33are arranged at a small distance from one another and are accordingly small due to power losses caused by line resistances. Another advantage is that the cleaning device1can also be used at operating locations where neither an external compressed air generator is available nor a sufficiently protected location is present outside the medium for accommodating the pump19. Furthermore, the pump19arranged in the housing25of the cleaning device1in the measuring device is surrounded by the medium when the sensor5is immersed in the medium. As a result, it is protected against ambient conditions possibly occurring at the site of use, and possibly also against frost.

Alternatively, however, the pump19can also be arranged outside the housing25of the cleaning device1. In this case, no electrical components are preferably arranged in the housing25of the cleaning device1. The latter is especially advantageous when the sensor5and thus also the housing25of the cleaning device1are to be used in regions subject to explosion hazard where electrical components must meet particular safety requirements in order to ensure that they cannot trigger an explosion even in the event of a technical defect.

As shown inFIG.1, the cleaning device1is designed, for example, as a component of the measuring device that is permanently connected to the sensor5. Alternatively, the cleaning device1is designed, for example, as a device which is detachably connected or which can be detachably connected to the sensor5. This variant shown inFIG.2offers the advantage that already existing sensors5can also be retrofitted as required. In both variants, the nozzle33or each of the nozzles33is in each case formed either as a component of the cleaning device5connected to the exhaust air duct31or as a component of the sensor5which is connected or can be connected to the exhaust air duct31.

Optionally, the cleaning device1additionally has a wiper35which can be operated by means of a wiper drive for carrying out wiper cleaning of the outer portion3.FIG.3shows a view of such a cleaning device1which can be mounted on a sensor5such as, for example, the sensor5shown inFIG.2, in such a way that the wiper35rests against an outer or end face of the sensor5comprising the outer portion3of the sensor5to be cleaned.

In principle, the wiper35can be operated independently of the components of the cleaning device1that serve to carry out the pressure-surge cleaning. In this case, the wiper drive is designed, for example, as an electric drive.FIG.4shows an example of a schematic representation of a cleaning device1, the wiper drive of which comprises an electric motor37which is connected to a shaft39of the wiper35in such a way that a rotation of the shaft39caused by the electric motor37causes a wiper movement of a wiper arm41of the wiper35corresponding thereto, in which the wiper arm41rotates about an axis of rotation formed by the shaft39.

In this variant, the cleaning device1preferably comprises a controller43which is connected to the pump19and the electric motor37and is designed to control the pump19and the electric motor37in such a way that each cleaning process which can be carried out by means of the cleaning device1includes at least one pressure-surge cleaning operation and finishes with a wiper cleaning carried out by means of the wiper35. This offers the advantage that, after the execution of the pressure-surge cleaning(s), any air bubbles remaining on the surface of the outer portion3are removed by the wiper35during the subsequent wiper cleaning. The removal of the air bubbles is advantageous especially in conjunction with sensors5, such as optical sensors, in which air bubbles located on the outer portion3can possibly lead to impairments of the measurement properties, especially the measurement accuracy. In addition, this cleaning method offers the advantage that, as a result of previous pressure-surge cleaning, already-removed, possibly abrasive, contamination components in the subsequent wiping cleaning, can no longer lead to scratching of the outer portion3.

Instead of the electric wiper drive, especially a pneumatic wiper drive connected to the pump19can alternatively be used.FIG.5shows a schematic illustration, andFIGS.6to8show sectional drawings of an embodiment of a cleaning device1having a wiper35, the pneumatic wiper drive of which is arranged in the housing25of the cleaning device1. As shown inFIG.5, the pump19is also preferably arranged here in the housing25of the cleaning device1. Alternatively, the pump19can be arranged outside the housing25, as shown inFIG.8. This offers the advantage, especially when used in explosion-prone areas, that the housing25located in the immediate vicinity of the sensor5in use is free of electrical components.

The wiper drives shown inFIGS.5to8are piston drives. Accordingly, they each comprise a piston45which is arranged in a piston housing43and which is movable in an axial direction back and forth in the piston housing43between two opposing stops47,49. Located in the piston housing43is a first chamber51and a second chamber53separated from the first chamber51by the piston45, the volumes of which chambers change depending on the position of the piston45. Accordingly, the volume of the first chamber51is minimal when the piston45is in the first end position shown inFIGS.5to8, in which the piston45abuts against the first stop47that delimits the first chamber51on the side facing away from the second chamber53, and maximum when the piston45is in a second end position shown in dashed lines inFIG.5, in which the piston45abuts against the second stop49. The piston45is connected to the shaft39of the wiper35by means of a mechanical converter55in such a way that a movement of the piston45from the first into the second end position results in a corresponding rotational movement of the wiper arm41from an initial position shown inFIG.5to an end position shown in dashed lines inFIG.5. In this case, the wiper arm41is in the end position and in the initial position preferably in each case outside the outer portion3to be cleaned, or at least outside a section of the outer portion3, such as, for example, the window11via which or through which the measured variable is measured.

The converter55shown inFIGS.6to8as an example comprises a spindle57which extends through the piston45and is rotatably mounted in the piston housing43, and which is displaced by the axial movement of the piston45into a rotational movement about the longitudinal axis thereof. The spindle57is connected at the end to the shaft39of the wiper35such that a rotational movement of the spindle57causes a rotation of the shaft39about its longitudinal axis. The rotation of the shaft39in turn causes a rotational movement of the wiper arm41about an axis of rotation corresponding to the shaft39. In this case, a pitch of a spindle external thread is preferably dimensioned such that the wiper arm41is moved by the piston movement of the piston45from the first end position into the second end position from its initial position into its end position and vice-versa.

In conjunction with the spindle57, the cleaning device1preferably comprises at least one anti-rotation lock59which prevents rotation of the piston45about its longitudinal axis. For example, the securing pins shown inFIGS.6to8, which extend parallel to the spindle57extending through the center of the piston45through an outer edge region of the piston45, are suitable as an anti-rotation lock59.

Alternatively, instead of the spindle57, other converters known from the prior art that transform a translation movement into a rotary movement can also be used to convert the axial piston movement into the corresponding rotational movement of the wiper arm41.

Regardless of the design of the converter55, the pump19is connected via the discharge line23connected on the output side to the pump19to an inlet61of the piston housing43which opens into the first chamber51. As shown inFIGS.5to8, the inlet61is designed, for example, as a bore which extends through a wall region of the piston housing43that surrounds the first chamber51externally. In this case, the piston45has, for example on its side facing away from the second chamber53, an extension60with a reduced base area, the axial height of which is dimensioned such that the inlet61also opens in the first chamber51when the piston45is in the first end position. Alternatively, the extension60can also be designed as a component of the first stop47on which the piston45rests in the first end position.

Regardless of the configuration in this regard, the pump19is switched on in that a pressure is gradually built up in the first chamber51by means of the pump19, through which pressure the piston45is pressed in the direction of the second chamber53. The resulting piston movement from the first end position to the second end position is converted by means of the converter55into a corresponding rotational movement of the wiper arm41from the initial position into the end position.

The first chamber51preferably also forms the pressure accumulator27, which is connected or can be connected to the nozzle(s)33via the exhaust air duct31equipped with the pressure-controlled valve29. In this case, the cleaning device1is designed such that the pressure-controlled valve29is opened by the pressure prevailing in the first chamber51when the piston45moved by the pressure prevailing in the first chamber51reaches the second end position.

FIG.5shows an example in which the exhaust air duct31opens into the interior of the piston housing43in a housing region of the piston housing43, which, independently of the piston position, always surrounds a section of the first chamber51. In this embodiment, the piston45is moved starting from the first end position by the pressure which is gradually built up in the first chamber51by means of the pump19into the second end position. Subsequently, the pressure in the first chamber51is further increased by means of the pump19until it exceeds the pressure value required for opening the pressure-controlled valve29, and the pressure surge is output via the open pressure-controlled valve29and the nozzle(s)33. Since the pressure-controlled valve29is permanently exposed here to the pressure prevailing in the first chamber51, the cleaning device1is designed here in such a way that the pressure value required for opening the pressure-controlled valve29is truly greater than the pressure required for the movement of the piston45into the second end position. This ensures that the piston45reaches the second end position before the first chamber51is vented via the pressure-controlled valve29.

FIGS.6to8show an alternative embodiment in which the exhaust air duct31equipped with the pressure-controlled valve29opens into a housing region of the piston housing43which only then adjoins the first chamber51when the piston45reaches the second end position. As can be seen from the sectional plane shown inFIG.7, the exhaust air duct31opens here into a recess62, which is introduced into a housing inner wall of the piston housing43and is open towards the interior of the piston housing43, such as a recess62formed by a section of a bore extending through the piston housing43or a branch channel running around the inside in the piston housing43. The recess62is arranged in the piston housing43at a height which is dimensioned such that a lower edge of the recess62facing the second stop49adjoins an upper side of an outer edge of the piston45facing the first chamber51when the piston45is in the second end position. Here too, the piston45is moved, starting from the first end position by the pressure which is gradually built up in the first chamber51by means of the pump19, into the second end position. As a result, the axial height of the first chamber51running parallel to the direction of movement of the piston45is increased to such an extent that the exhaust air duct31opens into the first chamber51, and the pressure prevailing in the first chamber51acts on the pressure-controlled valve29. Since the pressure-controlled valve29in this variant is only exposed to the pressure prevailing in the first chamber51when the piston45reaches the second end position, a pressure-controlled valve29can be used here that already opens at a lower pressure value than that in the pressure-controlled valve29used in the example shown inFIG.5. A further advantage of this embodiment is that the pressure required for carrying out the piston movement and thus also the wiper movement can be set independently of the employed pressure-controlled valve29. In this case, the pressure required for carrying out the piston movement can be adjusted, for example, via a characteristic value of a spring mounted under the piston45.

In the cleaning devices1shown inFIGS.5to8, the first chamber51is vented by each pressure surge output via the pressure-controlled valve29, so that the piston45can subsequently be moved back into the first end position.

Analogous to the rotational movement of the wiper arm41from the initial position into the end position, the rotational movement of the wiper arm41opposite thereto from the end position into the starting position can also be brought about by the fact that a pressure is built up in the second chamber53by means of the pump19, through which pressure the piston45is pressed from the second end position into the first end position. To this end, however, both chambers51,53would have to have an inlet that can be connected to the pump19via a channel equipped with a controllable valve, via which the chambers51,53can be alternately subjected to pressure, and both chambers51,53would have to be vented in alternation via a corresponding exhaust air duct.

Alternatively, the cleaning device1has a spring63which is arranged and designed such that the spring63is tensioned by the movement of the piston45from the first end position into the second end position, and the tensioned spring63moves the piston45back into the first end position when the pressure in the first chamber51drops due to the pressure surge output via the pressure-controlled valve29. For this purpose, the spring63can be designed in different ways. For example, the spring63can comprise a spring element or a plurality of coupled spring elements. In this case, the individual spring elements can each be designed, for example, as a compression spring element, as a clamping spring element, as a coil spring element, or as a diaphragm.

In the shown embodiments, the spring63is designed as a compression spring arranged in the second chamber53, which compression spring is compressed by the movement of the piston45from the first to the second end position. Alternatively, however, the spring can also be designed as a tension spring arranged in the first chamber51, which is stretched by the movement of the piston45in the direction of the second chamber53. Both variants offer the advantage that the spring63within the piston housing43is protected against environmental influences. Alternatively, however, the spring can also be arranged outside the piston housing43and/or be connected to the spindle57or the wiper35. For example, the spring can be connected to the wiper35in such a way that it is tensioned by the movement of the wiper arm41from the initial position into the end position and moves the wiper arm41back into its initial position after the pressure surge has been output. In this case, the piston45is transported into the first end position via the wiper movement converted by the converter55.

Regardless of the position and configuration of the spring63, a pressure is built up by switching on the pump19in the first chamber51, by means of which pressure the piston45is moved against the spring force of the spring63into the second end position. Due to this piston movement, the wiper arm41is moved from the initial position into the end position. When the piston45reaches the second end position, the pressure-controlled valve29opens automatically by the pressure acting thereon in this piston position. As a result, the first chamber51is vented and the pressure-surge cleaning of the outer portion3is carried out by the exhaust air. Due to the pressure drop caused by the venting of the first chamber51, the pressure which tensions the spring63is released, so that the piston45is moved back into the first end position by the spring force of the tensioned spring63. By means of this piston movement, the wiper arm41is simultaneously also moved from the end position back into the initial position via the converter55. For this purpose, a wiper cleaning automatically follows each pressure-surge cleaning, and this sequence is repeated until the pump19is switched off, and the cleaning process necessarily ends with a wiper cleaning. This offers the advantage that, if necessary, any remaining air bubbles are removed by the final wiper cleaning after the last pressure-surge cleaning. Furthermore, the cleaning device1offers the advantage that the cleaning process is started by switching on the pump19and is ended by switching off the pump19so that, in contrast to the variant shown inFIG.4, no control is required to control the sequence of the cleaning process.

As shown inFIGS.5to8, the second chamber53is preferably designed as a closed chamber. In this case, the pump power of the pump19, the volume of the second chamber53when the piston45is in the first end position, and the pressure value at which the pressure-controlled valve29opens are coordinated with one another such that the pressure which can be built up by means of the pump19in the first chamber51is greater than the internal pressure which prevails in the second chamber53when the piston45is in the second end position.

Alternatively, the second chamber53can be designed as a chamber that can be ventilated and vented. In this case, for example, an exhaust air duct67, which is shown in dashed lines inFIG.5and is equipped with an outlet valve65, is connected to the second chamber53, via which exhaust air duct the second chamber53is vented when the pressure in the second chamber53exceeds a predetermined pressure upper limit. In this case, the exhaust air can be output, for example, to the environment or to at least one of the nozzles33which are additionally connected or can be connected to the exhaust air duct67. The ventilation takes place, for example, via an air supply channel71which is shown in dashed lines inFIG.5and is equipped with an inlet valve69and is connected to the supply line21, and via which the second chamber53is ventilated when the pressure in the second chamber53falls below a predetermined pressure lower limit. The inlet valve69and/or the outlet valve65are suitable especially as valves designed as a check valve.

Optionally, the cleaning device1additionally has a supply air controller73which is designed to temporarily close the inlet61opening into the first chamber51during each pressure-surge cleaning performed with the cleaning device1, and to subsequently reopen it. An exemplary embodiment of this is shown inFIG.8. This supply air controller73comprises a gate valve75which is arranged in a recess77in a housing wall region of the piston housing43through which the inlet61extends. The gate valve75is arranged in the recess77so as to be displaceable back and forth in a direction parallel to the longitudinal axis thereof between a passage position shown inFIG.8and a locking position. The gate valve75comprises a passage channel79extending through the gate valve75, which passage channel79is aligned and arranged such that it forms a channel that is arranged in the inlet61and connects the first chamber51to the discharge line23connected to the pump19when the gate valve75is in the passage position. In addition, the gate valve75is designed such that it closes the inlet61when the gate valve75is in the locking position.

The recess77shown inFIG.8has a closed end region and an open-end region which is opposite the closed end region and is connected to the interior of the piston housing43via an opening81. In this case, the opening81is arranged at a height within the piston housing43which is dimensioned such that a lower edge of the opening81facing the second stop49adjoins the upper side of the outer edge of the piston45facing the first chamber51when the piston45is in the second end position. It is thus achieved that the gate valve75is pushed into the locking position by the pressure prevailing in the first chamber51when the piston45reaches the second end position. InFIG.8, the opening81is designed as a section of the branch channel, which surrounds the recess62and extends annularly in the piston housing43, into which the exhaust air duct31also opens.

Optionally, the gate valve75has a pressure contact surface83on its end facing the opening81, the radial distance of which decreases from a longitudinal axis of the piston housing43extending through the piston center in the opposite end of the gate valve75. The inclined pressure contact surface83offers the advantage that the portion of the force exerted by the pressure prevailing in the first chamber51with the piston45located in the second end position on the gate valve75, which portion acts parallel to the longitudinal axis of the gate valve75on the gate valve75, is increased as a result of this.

The supply air controller73shown inFIG.8comprises a return spring85which is designed and arranged in the recess77in such a way that the return spring85is tensioned by the displacement of the gate valve75into the locking position and pushes the gate valve75back into the passage position when the compressive force exerted through the opening81on the gate valve75falls below the restoring force of the tensioned return spring85. As a result, the inlet61is opened by the return spring85when the pressure in the first chamber51drops abruptly through the pressure surge output via the pressure-controlled valve29.

Each nozzle33which is connected or can be connected to the exhaust air duct31for carrying out the pressure-surge cleanings can be designed, for example, as a component of the cleaning device1or as a component of the sensor5.

In this respect, the cleaning device1has, for example, at least extension87in which the nozzle33or at least one of the nozzles33is arranged.FIG.3andFIGS.6to8show an exemplary embodiment with two extensions87formed integrally on opposite sides of the housing25of the cleaning device1. In this case, at least one nozzle33connected to the exhaust air duct31is arranged in at least one of the two extensions87. Optionally, the extensions87are simultaneously designed as a sensor enclosure which, when the cleaning device1is connected to the sensor5, encompasses at least a section of the sensor5on the outside.

Alternatively, or additionally, the cleaning device1has, for example, one or more nozzles33arranged along the wiper arm41and connected to the exhaust air duct31. In this case, the connection required for this between the exhaust air duct31and the nozzles33can be designed in different ways.

FIG.9shows an example in which the exhaust air duct31equipped with the pressure-controlled valve29is connected via a connecting line89arranged outside the housing25of the cleaning device1and a line extending inside the wiper35through the wiper arm41to the nozzles33arranged along the wiper arm41.

FIG.10shows a modification of the cleaning device1shown inFIGS.6to8, which has one or more nozzles33arranged along the wiper arm41, as a further example. In this variant, the exhaust air duct31can be connected via a plurality of line portions connected to one another during each pressure-surge cleaning to the line91which runs inside the wiper35through the wiper arm41and is connected to the nozzles33. These line portions comprise a first line portion93which is connected to the line91extending through the wiper arm41and extends along the shaft39of the wiper35or through the shaft39and extends in a direction running parallel to the shaft39into a rotary disk95connected to the spindle57. The rotary disk95is arranged in the piston housing43on the side of the second stop49facing away from the first chamber51, on which the piston45rests in the second end position. The first line portion93extending in the axial direction into the rotary disk95is connected at the end in the rotary disk95to a second line portion97which runs radially outwards inside the rotary disk95and opens at an outer side of the rotary disk95. In addition, the line portions comprise a third line portion99connected to the exhaust air duct31, which runs at least in portions through a housing wall of the piston housing43and opens into the interior of the piston housing43at the level of the mouth of the second line portion97at a position which is opposite the mouth of the second line portion97when the piston rotating the rotary disk95which is connected to the spindle57is located in the second end position shown inFIG.10.

In the case of cleaning devices1which have nozzles33arranged in the wiper35, the cleaning operations take place, for example, in that the wiper35is moved from the initial position into the end position in the manner described above, then a pressure-surge cleaning is carried out, in which the first chamber51is vented in a shock-like manner via the nozzles33integrated in the wiper35, and the wiper35is subsequently moved back into its initial position. The nozzles33on the wiper arm41are preferably arranged in such a way that they are aligned with the outer portion3of the sensor5to be cleaned when the wiper35is in its end position. For this purpose, the nozzles33are arranged, for example, on the side of the wiper arm41which, when the wiper arm41is in the end position, points in the direction of the initial position. This offers the advantage that, during each cleaning process, a wiper cleaning follows the pressure-surge cleaning carried out by the nozzles33arranged on the wiper35. This offers the advantage that each cleaning process ends with a wiper cleaning, by means of which air bubbles remaining on the outer area to be cleaned3are removed.

With regard to mounting measuring devices comprising the cleaning device1at a location of use, it is recommendable to combine the supply line21together with electrical connection lines101of the sensor5and/or the cleaning device1into a strand, via which the measuring device is immersed in the medium at the place of use.