Housing with vent sleeve as well as measuring instrument and pressure gauge for process measurement technology with such a housing

Abstract

Housing (2), with a venting device (10) arranged on the housing (2), which allows the supply of ambient pressure to the interior of the housing (2), wherein the venting device (10) is formed from a sleeve-like protective cap (11) with lateral openings (12) and a liquid-repellent membrane, wherein inside the venting device (10) a cavity is formed to receive the membrane and the membrane is arranged such that an opening in the wall of the housing (2) provided for the pressure supply is covered, characterized by that the sleeve-like protective cap (11) has a narrow, circumferential widening (14) in the area of ​​its side surface, so that a defined drip edge is formed.

Description

[0001] The invention relates to a housing according to the preamble of claim 1, a measuring instrument and a pressure measuring instrument for process measurement technology with such a housing.

[0002] Measuring instruments of the aforementioned type are used in automation technology to monitor the properties of a fluid, such as pressure, temperature, flow rate, and fill level. Depending on the application, these instruments are exposed to varying weather conditions or require frequent cleaning to maintain hygiene, for example, using a high-pressure or steam jet cleaner. However, pressure gauges require a passage through their housing, as the measured pressure values ​​must be related to the ambient pressure to display the relative pressure.

[0003] Such openings in housings are not only relevant for pressure gauges, but also for other measuring devices and housings in general, where a pressure difference to the inside of the housing should be avoided, e.g. as a result of changing atmospheric pressure.

[0004] One-piece barriers in the form of films or membranes are known from the prior art. For example, DE 102 32 028 B4 proposes providing a passage in the housing wall, which is closed with a liquid-repellent and gas-permeable segment to achieve pressure equalization between the interior of the housing and the external environment. This segment consists of a film, e.g., a plastic film, or a membrane, e.g., made of PTFE.

[0005] However, a disadvantage is that the films or membranes would be exposed unprotected to a high-pressure or steam jet used for cleaning purposes.

[0006] For this reason, pressure gauges in particular employ sleeve-like impact protection devices, which are designed as small, cylindrical bodies projecting laterally from the housing of the measuring instrument in the form of a protective cap and have lateral openings to prevent the direct jet from reaching the diaphragm or film. A pressure gauge with such an impact protection device is known, for example, from DE 10 2014 107 251 A1.

[0007] Other such ventilation units are known from DE 10 2015 109 704 A1 and EP 1 740 861 B1.

[0008] If the vent sleeve is designed in the form of the aforementioned impact protection devices, the so-called "teapot effect" can occur. Particularly during the cleaning process, the cleaning fluid does not drip off completely or quickly enough from the front edge of the vent sleeve, but instead flows at least partially down the sides of the vent sleeve towards the measuring instrument housing, thus also passing through the openings in the vent sleeve intended for air exchange. These openings can then be temporarily, at least partially, blocked, which can impair air exchange during this time.

[0009] The targeted draining of aggressive media to prevent corrosion is known from DD 2 04 767 A1.

[0010] The object of the invention is to further develop a vent sleeve for a measuring device mentioned above in such a way that the teapot effect is avoided.

[0011] The problem is solved by a housing with the features of claim 1, a measuring device with the features of claim 3, and a pressure gauge with the features of claim 4. Advantageous embodiments of the invention are specified in the dependent claims.

[0012] According to the invention, the sleeve-like protective cap has a narrow, circumferential widening on its side surface, thus forming a defined drip edge. The downward-facing area of ​​the vent sleeve is particularly problematic, as its position can vary depending on the installation configuration of the pressure gauge. The circumferential widening would therefore cover every conceivable installation configuration of the housing or the (pressure) measuring device.

[0013] The narrow, circumferential widening acts as a kind of nozzle. A liquid located in the downward-facing area of ​​the vent sleeve would be forced to flow upwards after passing around the defined tear-off edge created by the widening. However, this is prevented by gravity. As a result, the liquid drips off the narrow widening. The narrower the circumferential widening, the more pronounced the tear-off edge becomes, further facilitating the detachment of the droplet.

[0014] An advantageous further development provides that the narrow, circumferential widening is positioned at such a distance from the housing that any liquid running down the housing, e.g., condensate or cleaning fluid, cannot penetrate into the area of ​​the openings. Due to the continuous dripping of the liquid, less liquid remains on the housing of the measuring instrument and on the venting device itself during the cleaning process.

[0015] The narrow, circumferential widening therefore has two functions: it forms a drip edge and at the same time it acts as a barrier that prevents liquid running down the housing from entering the area of ​​the openings.

[0016] The invention will now be explained in more detail using exemplary embodiments and with reference to the drawings.

[0017] They show schematically: Fig. 1 a pressure measuring device according to the invention in perspective view and Fig. 2 a pressure measuring device according to the invention in a frontal view.

[0018] In the following description of preferred embodiments, identical reference numerals denote identical or comparable components.

[0019] The Fig. 1 and Fig.Figures 2 each show an electronic pressure measuring device 1 for use in process measurement technology, which is manufactured and distributed by the applicant under the designation Plxxxx. However, the invention is not limited to a pressure measuring device, but is applicable to housings of any type where a pressure difference between the interior of the housing and the environment is to be avoided, e.g., due to changing atmospheric pressure, or where moist air is to escape from the interior, e.g., during temperature changes in a humid environment and resulting condensation inside the housing.

[0020] The measuring device 1 essentially consists of a housing 2, which is mounted on a process connection 3. The process connection 3 includes, on the one hand, the sensor unit in the form of a pressure measuring cell (not shown) and, on the other hand, enables the mechanical connection of the measuring device 1 to the container or pipe containing the medium. The evaluation electronics (not shown), which are located in the housing 2, are designed to evaluate and process the measurement signals supplied by the sensor unit. These signals can then be accessed via the connector and, for example, forwarded to a PLC.

[0021] The housing also includes a display and operating elements. The measuring device 1 is operated via these elements, i.e., parameterization or setting of essential parameters, such as switching points, is carried out. The respective actions are displayed to the user.

[0022] For pressure gauges that measure pressure relative to ambient pressure, a venting device 10 is necessary so that the measured pressure values ​​can be related to the ambient pressure for the output of the relative pressure. This venting device 10 initially consists of an atmospheric connection to the outside, which is sealed by means of a liquid-repellent, breathable membrane, thus allowing pressure exchange while simultaneously protecting the interior of the pressure gauge from the ingress of liquid. To protect this membrane from high-pressure or steam jets used for cleaning purposes, the venting device 10 further includes a protective cap 11 with lateral openings 12.

[0023] The invention focuses on a narrow, circumferential extension 14 of the protective cap 11, which is positioned at such a distance from the housing 2 of the measuring device 1 that any liquid running off the housing 2, e.g., consisting of condensate or cleaning fluid, cannot penetrate into the area of ​​the openings 12 on the protective cap 11. When the pressure gauge 1 is cleaned, this liquid, or the condensate that constantly accumulates on the housing 2, can drip off in a controlled manner from this narrow, circumferential extension 14, as a kind of spout is formed at this point. Due to the continuous dripping of the liquid, less liquid remains on the housing 2 of the measuring device and on the venting device 10 itself during the cleaning process, thus preventing any obstruction of the openings 12 in a simple manner.

[0024] The widening 14 therefore has two functions: it forms a drip edge and at the same time prevents any liquid running off the housing 2 from entering the area of ​​the openings 12. Reference symbol list 1 pressure gauge 2 cases 3 Process connection 10 Venting device 11 Protective cap 12 openings 14 narrow, circumferential widenings

Claims

[1] Housing (2), with a venting device (10) arranged on the housing (2), which allows the supply of ambient pressure to the interior of the housing (2), wherein the venting device (10) is formed from a sleeve-like protective cap (11) with lateral openings (12) and a liquid-repellent membrane, wherein inside the venting device (10) a cavity is formed to receive the membrane and the membrane is arranged such that an opening in the wall of the housing (2) provided for the pressure supply is covered, characterized by , that the sleeve-like protective cap (11) has a narrow, circumferential widening (14) in the area of ​​its side surface, so that a defined drip edge is formed. [2] Housing (2) according to claim 1, characterized by, that the narrow, circumferential widening (14) is arranged at such a distance to the housing (2) that a liquid running off the housing (2) cannot penetrate into the area of ​​the openings (12). [3] Measuring instrument for process measurement technology, comprising a housing (2) according to one of the preceding claims. [4] Pressure gauge (1), with a housing (2), a [unclear] in the housing (2) a pressure measuring cell arranged and a venting device (10) arranged on the housing (2), which enables the supply of an ambient pressure to the pressure measuring cell and thus the measurement of a relative pressure, wherein the venting device (10) is formed from a sleeve-like protective cap (11) with lateral openings (12) and a liquid-repellent membrane, wherein inside the venting device (10) a cavity is formed to receive the membrane and the membrane is arranged such that an opening in the wall of the housing (2) provided for the pressure supply is covered, characterized by , that the sleeve-like protective cap (11) has a narrow, circumferential widening (14) in the area of ​​its side surface, so that a defined drip edge is formed. [5] Pressure gauge (1) according to claim 4, characterized by , that the narrow, circumferential widening (14) is arranged at such a distance to the housing (2) of the measuring instrument (1) that a liquid running off the housing (2) cannot penetrate into the area of ​​the openings (12).

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