The present invention relates to a pressure equalizing housing device for preventing the entrance of moisture or other contaminators into the interior of the housing device.
Electro-optical, electronic and other instruments may be heavily affected, and their components may be irreversibly damaged, by excessive moisture. As used herein, the term “moisture” is intended to refer to water which is diffused, penetrated or condensed from the ambient atmosphere, whether in liquid or vapor form. Housings, enclosing cameras, optics, electronics and instruments, undergo thermal cycling by external or internal heat source(s) and due to on/off cycling within the enclosure, result in moisture built-up therein. A relatively simple way of dispensing moisture is to provide greater ambient airflow across, or through, the enclosure. Ambient air, however, may be contaminated by dust and other contaminants, unwanted within the housing enclosure, and moreover, when components are located in an enclosed housing, it can be very difficult to provide adequate airflow to reduce moisture. Whenever the housing is non-hermetically sealed, it is possible to reduce moisture in the housing by placing therein a drying agent or desiccant. The terms “desiccant” or “drying agents” as used herein, are intended to refer to any material which absorbs water vapor from the air and are thereby able to reduce the moisture in the air inside the housing. However, in order to maintain low moisture content in the functional space of non-hermetically sealed housings for an extended period of time, quite a big portion of the system space should be allocated for storing drying agents. In those cases where the space is small and weight is critical, this solution is also not practical.
Another method to resolve the moisture problem in an enclosure is to fill it with moisture-free gas, e.g., nitrogen, at a pressure higher than the ambient pressure. This “overpressure” method requires hermetic sealing of the housing, and therefore, results in costly housings. During the lifetime of the product, this method also requires periodical pressure inspection. Therefore, the “overpressure” method may not be adequate for mass production of low-cost and maintenance-free systems.
It is therefore a broad object of the present invention to provide a pressure equalizing housing device in which the penetration capability of moisture and/or other contaminators into the housing, is reduced.
In accordance with the present invention there is therefore provided a pressure-equalizing housing device, comprising a rigid housing having a coupling end and configured to contain at least one instrument, said coupling end of the housing is adapted to be at least indirectly sealable to a radiation transmittable surface, an opening made in a wall of said housing enabling fluid to pass therethrough, said housing and surface delimiting an interior space communicating with the exterior of the housing via said opening, and a pressure-influenced member forming an expandable and retractable volume body, a portion of which member is located adjacent to, or the interior of which member communicates with, said opening, for equalizing the pressure inside and outside said housing.
The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.
With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.
In the drawings:
The pressure equalizing housing device 2 illustrated in
The member 8 is delimited by the rigid housing part 6 and mechanical delimiter 28, which provide it with a structural support during the volume variation and also with mechanical protection, and delimits the volume of the member 8, to avoid interference with the optical field-of-view of the instrument 14. The space between the exterior of the member 8 and the interior of the rigid housing part 6 is continuously “breathing”, by the volume variation of the member 8, subject to the pressure gradient. This breathing space is controlled by the opening 26 located in the rigid housing part 6 and provides an air pathway between the ambient and the non-functional space 12 of the housing device 2.
It should be understood that the bellows 30 may just as well be located outside the housing, in which case, the functional space 10 is the space extending from within the housing through the opening 26 into the bellows 30.
The operation of this embodiment is similar to that described above. Whenever the functional space 10 is sealed and capable of maintaining a certain level of overpressure, it can initially be inflated, up to a predetermined level of overpressure, by a moisture-free gas, e.g., dry air, thus improving its resistance to moisture and/or other contaminators penetration/diffusion. Optionally, whenever the ambient air is relatively clean and dry, the overpressure can be naturally built up by a release valve (not shown), which enables ambient air inlet into the functional space 10 above a predetermined level of pressure gradient. The pressure gradient should be higher than the pressure gradient needed to inflate/deflate the expandable bellows 30. The implementation of a release valve (one or two-directional) avoids collapsing and/or overstressing of the rigid housing, when structured of light materials, as may be required in mass production products.
To reduce the fatigue and wear of the member 8 and to reduce the amount of desiccant 24, the volume of fluid captured within the functional space 10 of the device during the installation, can be decreased to a minimum by a filler. Smaller captured fluid volume will result in a lower demand for intake/discharge to equalize the pressure, and therefore, will allow longer lifetime of the member 8.
The device 2 may be made in a variety of shapes and sizes as required for placing the instruments 14, such as cameras, optics, electronics, communication instruments, sensors, and the like, inside. The housing parts 4 and 6 may be made of a single enclosure or assembled of more than a single piece, as shown in
When the air pressure inside the functional space 10 drops, or alternatively, the ambient pressure rises, the expandable or retractable bellows 30, responsive to the pressure gradient or difference, is inflated by the ambient air through the opening 26, until the pressure difference between the functional space 10 and non-functional space 12 is eliminated or significantly reduced. Pressure difference decrease will eliminate or significantly reduce the ambient air penetration into the interior functional space.
When the pressure of the functional space rises, e.g., because the thermal cycle, or alternatively, the ambient pressure drops, the expandable or retractable bellows 30 will discharge excessive air until either pressure difference is eliminated or dramatically reduced, or the expandable or retractable bellows 30 reaches its minimum volume.
Since the pressure difference between the functional space 10 and the ambient air is low, rigid housing part 4 and/or 6 may optionally have apertures covered by movable or rotatable parts or surfaces sealed by sealers, e.g., a rotatable surface 20 and a housing part 6 rotatable about housing part 4.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Number | Date | Country | Kind |
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176983 | Jul 2006 | IL | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/IL2006/000913 | 8/8/2006 | WO | 00 | 2/7/2008 |
Number | Date | Country | |
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60707164 | Aug 2005 | US |