Rail mounting desiccant unit

There is provided apparatus for absorbing humidity inside an electrical enclosure and indicating absorption of humidity. The apparatus comprises a housing for a desiccant which is attachable to a rail inside the electrical enclosure, such as a DIN specification rail. The housing also includes a transparent window which allows the desiccant to be visualized.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from United Kingdom Patent Application No. 15 17 871.8, filed 9 Oct. 2015, the entire disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Excess humidity inside an electrical enclosure will ultimately result in damage to the electrical enclosure and the components housed within. The present invention relates to apparatus for absorbing humidity inside an electrical enclosure and indicating that humidity has been absorbed.

2. Description of the Related Art

Existing products on the market to counter the problem of excess humidity include air conditioning systems and heating systems. However, the installation and maintenance of such systems in every applicable electrical enclosure can be a monumental task, generally associated with a high procurement cost, high cost of installation and a high cost of maintenance. These systems present hazards themselves, for example, heating devices can overheat and cause significant damage whilst air-conditioning systems may leak inside an electrical enclosure.

A humidity detector for indicating humidity inside an electrical enclosure is known, but installation is required by drilling a hole in the side of the electrical enclosure. Drilling a hole within an enclosure adds to the possibility for a seal to break and thereby provide a path for elements of the external environment to enter an electrical enclosure. Retro-fitting this type of unit is difficult because it requires a portable drill, thereby presenting an ignition risk due to the spark potential of the battery drill and the sparks and heat caused by drilling metallic electrical enclosures.

There is therefore no known product which safely addresses the problem of excess humidity inside electrical enclosures whilst also indicating a need for further investigation, without further jeopardizing the integrity of the electrical enclosure.

The apparatus of the present invention has no running costs, is non-flammable, non-toxic, easily retrofitted, easily maintained and is designed to be mounted on a rail inside an electrical enclosure specifically intended for enclosure components.

BRIEF SUMMARY OF THE INVENTION

According to an aspect of the present invention, there is provided apparatus for absorbing humidity inside an electrical enclosure and indicating absorption of said humidity, comprising: a housing for a desiccant; wherein said housing is configured for attachment to a rail inside said electrical enclosure; and said housing comprises a transparent window.

According to a second aspect of the present invention, there is provided a method of attaching apparatus for absorbing humidity inside an electrical enclosure and indicating absorption of said humidity to a rail inside said electrical enclosure, comprising the following steps: i) inserting a bolt into channel on said housing; ii) tightening said bolt within said channel using a tool; iii) allowing said bolt to engage with a clamp mechanism at base of said channel; and iv) drawing said clamp mechanism towards housing.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

The present invention may be deployed in any electrical enclosure. Electrical enclosures house the switches and displays of electrical and electronic equipment. An example of an environment in which there are large numbers of electrical enclosures is chemical plant101, as shown inFIG. 1. Other examples may be food production plants, steel plants, oil/gas platforms, oil/gas process plants and power stations.

Engineer201checking the components in electrical enclosure202is shown inFIG. 2. Electrical enclosures, such as enclosure202, house the switches and displays of electrical and electronic equipment, prevent electrical shock to equipment users and protect the contents from the environment. Humidity can be a problem inside electrical enclosures. If excess humidity is left to condense, it will ultimately degrade components such as terminals and wiring cores, change contact resistance, cause flashovers and current fluctuations, thereby ultimately resulting in system failure.

Equipment inside electrical enclosures can have a significantly high procurement cost. Signal accuracy is of paramount importance because said signals may be operating safety equipment and/or platform production. Damage caused by excessive humidity within electrical enclosures can result in significant safety concerns and/or result in large financial implications due to loss of production if equipment fails.

The apparatus embodied in the present invention is shown inFIG. 3. Housing301is attached to a rail302inside electrical enclosure303. The rail is typically a DIN rail which is an industry standard rail used in industry inside electrical enclosures. It is appreciated that other similar types of rail meeting alternative industry standards are within the scope of the present invention. Thus, where DIN rail is used in the specification, it should be interpreted to mean any suitable rail found inside an electrical enclosure.

An industry standard DIN rail is a metal rail typically used for mounting terminals, control equipment and circuit breakers inside equipment racks or electrical enclosures. A standard DIN rail is made from cold rolled carbon steel sheet with a zinc plated and chromated bright surface finish. The term is derived from the original specifications published by Deutsches Institut für Normung (DIN) in Germany. There are three main types of DIN rail, namely a top hat section DIN rail, a C section DIN rail and a G section DIN rail.

The apparatus embodied by the present invention comprises housing301, which receives desiccant. Housing301is configured for attachment to DIN rail302inside electrical enclosure303. Attachment of housing301to DIN rail302ensures that the desiccant is mounted in an area at the top of electrical enclosure303.

The desiccant deployed by the present invention is used to absorb excess humidity from within the electrical enclosure. A certain amount of humidity may be desirable, as removal of all humidity may cause some items to become brittle. However, as mentioned in connection withFIG. 2, if excess humidity is left to condense onto surfaces, it will degrade components, ultimately resulting in system failure.

Desiccants are known to absorb humidity and a commonly used desiccant is silica gel. Previously, silica gel has been used inside new products, such as new shoes, bags, clothing and electronics to absorb humidity. Such silica gel is typically used in the form of sachets.

However, silica gel sachets cannot be used inside electrical enclosures because they would merely fall to the base of the enclosure. Furthermore, they do not provide an indication for when they have expired and require replacement. Generally given the same temperature and pressure, humid air rises compared to dry air. Consequently, housing301is required as a means to mount the desiccant at the top of the electrical enclosure.

Housing301comprises transparent window304for visualizing the desiccant. In the illustrated embodiment, transparent window304is used to visualize the change of color of the silica gel to allow a visual indication of when the silica gel has absorbed a particular amount of humidity and needs to be changed.

Most electrical enclosures adhere to a particular Ingress Protection rating (IP rating) in order to conform to industry standards. An example is IP64. The first digit makes reference to solids whilst the second digit makes reference to liquids. Clearly, the latter digit is of relevance with regards to the present invention. Therefore, taking an IP rating of 61, 1 protects only against vertically falling drops of water; for an IP rating of 64, 4 protects against splashes of water whereas for an IP rating of 68, 8 protects against long periods of immersion under water at pressure. The apparatus embodied by the present invention can indicate when a particular IP rating is not being adhered to, possibly because a seal on an electrical enclosure or a cable gland (where electrical wires enter the enclosure) has been compromised. Importantly, because the apparatus of the present invention can be used to indicate when an IP rating is not being adhered to or when other humidity control devices are not functioning, it can act as an early warning system to signify the need for further investigation.

Many electrical enclosures such as junction boxes may be checked on an annual basis although other electrical enclosures containing, for example, life-saving equipment, may be checked every month. Therefore, the checking and replacement of the desiccant in the apparatus embodied in the present invention may be incorporated into routine checks of electrical enclosures.

An external view of housing301embodied in the present invention showing transparent window304is illustrated inFIG. 4A, whilst an alternative view of the external surface of housing301embodied in the present invention is shown inFIG. 4B. Housing301is configured for attachment to a DIN rail (not herein shown), and inFIG. 4B, clamp mechanism401is shown for attaching housing301to the DIN rail.

The present invention thus provides housing301for mounting onto a DIN rail inside an electrical enclosure such as a junction box. A DIN rail is a designated method of mounting inside an electrical enclosure and anything required inside an electrical enclosure, such as terminals for cables entering the enclosure, is fixed to a DIN rail. The housing embodied in the present invention is configured for attachment to a top hat section DIN rail, but configurations of alternative types of DIN rail fall within the scope of the present invention. Therefore, the housing embodied in the present invention is suitable for mounting onto any type of DIN rail, although modifications to the housing and clamp mechanism that are within the ambit of the skilled person may be required for mounting onto certain rails.

FIGS. 4A and 4Bshow lid402of the apparatus embodied in the present invention. Lid402comprises a number of holes403, as shown inFIGS. 4A and 4B. In the illustrated embodiment, there are approximately four hundred to five hundred holes and holes403have an approximate diameter of half a millimeter (0.5 mm). Holes403function to provide air ventilation to ensure that the air inside the electrical enclosure does pass over the desiccant and that the desiccant absorbs humidity and passes on the humidity from the top layer downwards. Holes403are approximately half a millimeter (0.5 mm) in diameter to ensure that the desiccant does not fall out of housing301through air ventilation holes403. Silica gel, when used as a desiccant in bead form, is typically between two millimeters (2 mm) and five millimeters (5 mm) in diameter.

Lid402comprises four screws404for removing lid402, to allow replacement of desiccant. A tool such as a screwdriver is required to open lid402of housing301to remove spent desiccant and replace with fresh desiccant.

The same tool as is used for opening lid402of housing301is inserted into channel405. As explained in connection withFIGS. 6A and 6B, the tool is inserted into channel405to tighten a bolt (not herein shown), which engages with clamp mechanism401. Clamp mechanism is drawn towards housing301, thereby clamping housing301onto the DIN rail.

In the illustrated embodiment, housing301is fabricated from a polycarbonate material which itself has a very low rate of humidity absorption and a very low rate of shrinkage. The latter feature is important as it increases the accuracy of the final size of housing301during the injection molding process. Transparent window304is fabricated from a polycarbonate and all other components from stainless steel.

InFIG. 5A, lid402of the present invention has been removed, revealing the interior of the embodied apparatus in an empty state. InFIG. 5A, there is no desiccant within the apparatus. Holes501represent the holes for receiving screws404(not herein shown) for attaching lid402(not herein shown) to housing301once housing301has been refilled with desiccant. Channel405is shown inFIG. 5A. As explained in connection withFIGS. 6A and 6B, a tool such as a screwdriver is inserted into channel405to tighten a bolt (not herein shown), which engages with clamp mechanism401. Clamp mechanism is drawn towards housing301, thereby clamping housing301onto the DIN rail.

InFIG. 5B, lid402(not herein shown) of the claimed apparatus has been removed, revealing the interior of housing301. Holes501represent the holes for receiving screws404(not herein shown) for attaching lid402(not herein shown) to housing301once housing301has been re-filled with desiccant.

Channel405is shown inFIG. 5B. As explained in connection withFIGS. 6A and 6B, a tool such as a screwdriver is inserted into channel405to tighten a bolt (not herein shown), which engages with clamp mechanism401. Clamp mechanism is drawn towards housing301, thereby clamping housing301onto the DIN rail.

In the illustrated embodiment, housing301is full of silica gel in a bead form502. Although silica gel in a bead form502is used in the illustrated embodiment, any other desiccant falls within the scope of the present invention. Other desiccants may include, for example, Montmorillonite Clay, Molecular Sieve, Calcium Sulfate etc.

Silica gel only absorbs a certain amount of water, and this is up to forty percent (40%) of its own weight. Therefore, as an example, fifty grams (50 g) of silica gel would absorb around twenty grams (20 g) of water vapor. It is therefore possible to calculate how much silica gel by weight to place in housing301to absorb a specific amount of humidity.

Several types of silica gel are known that undergo different color changes. In the illustrated embodiment, the type of Silica gel used is that which changes from orange to clear, but other types of silica gel which change, for example, from orange to green, are also within the scope of the invention.

FIG. 6Ashows channel405. Channel405is configured for receiving bolt601and at the base of channel405is clamp mechanism401. Channel405receives bolt601, and in the illustrated embodiment, bolt601is a sixty millimeter (60 mm) bolt. Bolt601is inserted into channel405and the head of bolt601is tightened using a tool such a screwdriver (not herein shown). The process of tightening bolt601causes bolt601to engage with clamp mechanism401. Clamp mechanism401is then drawn towards housing301, thereby clamping housing301onto DIN rail (not herein shown).

Housing301comprises a recess to allow for varying degrees of tolerances from bolt manufacturers. The recess may be, for example, three quarters of a millimeter (0.75 mm). Clamp mechanism401is drawn directly towards housing301and does not itself rotate.

Different makes of tool, such as a screw driver, have varying degrees of insulation, and in general, the thickness of insulation increases towards the handle of the tool. In tools having a greater degree of insulation, the tool will not be able to physically reach as far down the channel inside the housing compared to tools having less insulation. However, bolt601, which is sixty millimeters (60 mm) in length, allows for different makes of tool, having different degrees of insulation, to be inserted into channel405and still reach the head of bolt601. However, it is also within the scope of the present invention that bolts of alternative lengths may be used (albeit with modifications required that are within the scope of the skilled person), in which case a tool having the appropriate amount of insulation so that the tool can be inserted into channel405and still reach the head of the bolt.

In the illustrated embodiment, channel405tapers internally from a diameter of six millimeters (6 mm) to five millimeters (5 mm), and is configured for use with bolt601with a head having a diameter of five point four millimeters (5.4 mm). During the initial assembly the bolt is forced past this taper. This internal tapering of channel405therefore acts as a mechanism to prevent bolt601from falling out of housing301should bolt601be loosened from the clamp mechanism401. Other degrees of tapering are also within the scope of the present invention.

FIG. 6Bshows a close up view of bolt601engaging with clamp mechanism401, and clamp mechanism401engaging with DIN rail302. Engagement of clamp mechanism401with DIN rail302secures housing301to DIN rail302.

An alternative embodiment of the apparatus embodied in the present invention is shown inFIGS. 7A and 7Bin plan view. The apparatus ofFIGS. 7A and 7Bis substantially similar to that as previously shown and differs only in the arrangement of the clamp mechanism as will now be described.

The apparatus is shown inFIG. 7Ain an empty state with no desiccant within the apparatus. The apparatus comprises housing701which is configured for attachment to a rail inside an electrical enclosure in the manner shown in previousFIG. 3. Housing701is configured to receive a desiccant in a substantially similar manner to the previous embodiment. The desiccant is used to absorb humidity and may be silica gel or an alternative desiccant which is suitable for use in electrical enclosures of the types previously indicated.

The apparatus comprises a transparent window702which is used to view the desiccant when it is placed within a cavity703of the housing701in a similar manner to that described inFIG. 5B.FIG. 7Aillustrates the apparatus with the lid704removed, which is shown inFIG. 7B. In use, and when filled with desiccant, lid704is placed on top of housing701and attached to housing704by utilizing holes705in housing701and corresponding holes706in lid704. Holes705and706respectively are configured to receive screws which attach lid704to housing701.

Referring toFIG. 7A, lid704has been removed to reveal channel707. In a similar manner to the embodiment described in respect ofFIGS. 5 and 6, a tool such as a screwdriver is inserted into channel707to tighten a bolt, which engages with a clamp mechanism708. Clamp mechanism708is drawn towards housing701which thereby clamps housing701to an industry standard rail such as a DIN rail.

Channel707comprises a first portion709which provides a closed channel and a second portion710which provides an open channel. The open channel provides for easy insertion of a bolt for tightening the clamp mechanism708as will be described in further detail inFIG. 8.

A corresponding channel closure portion711is provided and fixed to lid704as illustrated inFIG. 7B. When lid704is attached to housing701, closure portion711fits into the aperture of open channel710.

A cross sectional view of channel707is illustrated inFIG. 8where housing701has lid704fitted thereto. Closed channel709is shown with a bolt801inserted therein. Open channel710is shown with closure portion711in place in aperture802given that lid704has been attached to housing701.

Bolt801is positioned in closed channel709when lid704is removed from housing701. As closure portion711does not form part of channel707when lid704has been removed, bolt801can be angled into the space of closed channel709which has a wider diameter than the diameter of the body of bolt801giving a clearance gap803. For example, in the embodiment, closed channel709has an internal diameter of four millimeters (4 mm). In comparison, the open channel710has a widest diameter of six millimeters (6 mm) and tapers to a diameter of four millimeters (4 mm).

Thus, in order to activate the clamp mechanism708in this alternative embodiment, bolt801is inserted into the housing701and bypasses tapered section804. When lid704is replaced, bolt801is encased within housing701and cannot fall out. In turn this reduces the amount of wear on the housing. It is appreciated that bolt801is tightened in a substantially similar manner to that of bolt601inFIG. 6.