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1. WO2002037918 - CLIMATE CONTROL OF AN OUTDOOR CABINET

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

Climate control of an outdoor cabinet

TECHNICAL FIELD OF THE INVENTION

The present invention relates to an outdoor cabinet housing electrical, heat generating equipment, and a method for controlling the climate within such a cabinet.

DESCRIPTION OF RELATED ART

Telecommunication equipment and other electrical equipment housed in base station cabinets require specific climate conditions to work properly. Heat generated by equipment and components, as well as ambient conditions, such as temperature, solar radiation and humidity, strongly affect the climate within the cabinet. Extreme deviations from these specific climate conditions, e.g. temperatures within the cabi- net below 0 °C can not be accepted without jeopardising function and performance of the equipment.

For this reason a climate control apparatus is normally required for controlling the climate within the cabinet. Such a climate control apparatus may comprise units such as fans, heat exchangers, heaters or refrigeration units etc. The composition of such units is determined by ambient conditions, insulation of cabinet and the amount of heat generated by the electrical equipment.

, One way of arranging such a climate control apparatus is to mount it in a door of the cabinet. Hereby, the climate control apparatus is separated from the electrical equipment which facilitate installation as well as the access to the electrical equipment during repairs and maintenance. The climate control apparatus generates a tempered, cooled or heated depending on the situation, air flow to be circulated in the cabinet. The air flow passes by the electrical equipment inside the cabinet in a duct system, exchanging heat, and returns to the climate control apparatus, where the air is treated again. The duct system is provided with air outlet(s) and air inlet(s), which each are in flow communication with corresponding openings of the door mounted climate control apparatus as long as the door is closed. To facilitate the air flow between the air inlet and the air outlet inside the duct system fans are normally arranged in the duct system.

GB 2 277 767 shows a base station cabinet housing telecommunication equipment. A door is mounted to the cabinet providing access to the cabinet. The door is equipped with a climate control apparatus comprising fans and a heat exchanger, and optionally also a heater or a refrigerator unit, depending on climate situations, for controlling the climate within the cabinet. An air flow is circulated by means of the climate control apparatus, passes by the electrical equipment in a heat exchanging manner, and returns to the climate control apparatus, where heat is absorbed/emitted. Hereby, air conditioning is secured inside the cabinet.

However, this door mounted climate control apparatus is not able to control the climate within the cabinet when the door is open.

SUMMARY

One problem related to the disability of controlling the climate within the cabinet when the door is open occurs during repairs and maintenance of the interior of the cabinet at the same time as the ambient temperature is low, e.g. below 0 ° C. This is a common situation in countries having an arctic climate. Since the door has to be ' open during such operations, to provide access to the repairman, the door mounted climate control apparatus itself is not able to control the temperature within the cabinet. Instead non-treated, low temperature ambient air is drawn into the cabinet risking to damage electrical equipment.

To avoid damages to the electrical equipment a temperature alarm connected to a temperature sensor normally turns off the equipment when the temperature within the cabinet falls below a predetermined level. These turnoffs are however not desir- able since they cause expensive and unacceptable disturbances in telecommunication traffic.

To allow repairs and maintenance during such conditions a shelter, e.g. a tent is normally required to cover the base station at the same time as a heating fan warms up the air within the shelter.

Problems related to the necessity of arranging a heated shelter around the base station cabinet every time a repairman is to access the interior of such a cabinet are ob-vious. For example, it is a time consuming procedure to pitch a tent around the base station cabinet and warm the interior up. Such pitching may also be complicated if the base station is, e.g. roof mounted on a building, since the space required for such pitching is not insignificant.

The present invention seeks to overcome the above mentioned drawbacks.

Thus, an object of the present invention is to maintain f nction and performance of the electrical equipment inside the cabinet even though the door is open and the outdoor temperature is low.

The present invention solves the problem by means of creating a protective air curtain in front of the electrical equipment when the door is open. The air curtain in front of the electrical equipment prevents cold air to be drawn into the cabinet and admits the door to be opened even though the outdoor temperature is low. Since no cold air is drawn into the cabinet the use of shelters and heating fans is not necessary during repairs and maintenance.

The air curtain is createdby means of a deflection means arranged in the vicinity of the air outlet. It is adapted to deflect the air flow exiting the air outlet(s) toward the air inlet(s) when the door is open and the climate control apparatus no longer is in flow communication with the duct system. The air curtain is comprised from air normally circulating in the duct system, and which is heated by the electrical equipment.

Preferably, means are provided for automatically bringing said deflection means into an active state, i.e. deflecting the air toward the air inlet, when the door is opened and the air temperature outside the cabinet has fallen below a predetermined level.

It is also conceivable to provide means for manually affecting said deflection means, instead of automatically, into an active state when the door is opened.

In a preferred embodiment of the invention the deflection means is a slide tiltably mounted above the air outlet, so as to shield the air outlet(s) and deflect the air flow toward the air inlet(s). Hereby, an inexpensive and simple solution is achieved, which requires a minimum of space inside the cabinet and is easy to handle by a repairman.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 a is a perspective view of an outdoor cabinet according to prior art;

Fig. lb is a perspective view of the cabinet in fig. la when a door is open;

\ Fig. lc is a cross-sectional side view of the outdoor cabinet in fig. la showing a normal air flow when the door of the cabinet is closed;

Fig. 2 is a cross-sectional side view of the outdoor cabinet in fig. la-c showing the air flow when the door is open;

Fig. 3a is a perspective view of a slide in non-active position;

Fig. 3b is a perspective view of the slide in a an active position;

Fig. 4a shows a cross-sectional side view of the cabinet according to the present invention comprising the slide in fig. 3a in the non-active state;

Fig. 4b shows a cross-sectional front view of the cabinet according to the present invention comprising the slide in fig. 3a in the non-active state;

Fig. 5a shows a cross-sectional side view of the cabinet comprising the slide in the active state;

Fig. 5b shows a cross-sectional front view of the cabinet comprising the slide in the active state;

DETAILED DESCRIPTION OF EMBODIMENTS

Figs, la-c shows views of a outdoor cabinet 1 according to prior art. The cabinet is intended for outdoor use in a telecommunication system. The cabinet comprises a box-like body 3 having two side walls 5, a rear wall 7, and a roof 9. A door 11 is mounted to the box-like body by means of not shown hinges. Louvres 12 a-b are arranged in the door of the cabinet for entry and exit of an external air flow in respectively out of the cabinet. A knob 13 is attached to the door to facilitate closing and opening of the door.

The box-like body is inside (as shown in fig. lb-c) provided with slots or subracks 15 adapted to accommodate electrical equipment/units 17, such as telecommunication units or other heat generating units. The electrical units 17 are vertically stacked on top of each other within the subracks 15. A horizontal, intermediate space is defined between each electrical unit 17. During operation heat is generated by the electrical units, which has to be removed so as to maintain function and performance of the electrical equipment.

To this end a fan 21 is, as shown in fig. lc, arranged above each electrical unit and is adapted to remove heat generated by the electrical units and transfer it to an internal duct system 23. The internal duct system 23 comprises air inlets 25 and an air outlet 27 arranged at a front side 28 of the electrical units, which is accessible when the door 11 is open. The air outlet 27 is arranged above the air inlets 25. The duct system 23 extends from the air inlets 25, through the electrical units 17, to a rear duct portion 29 arranged between the rear wall and a rear side 30 of the electrical units. Further, the rear duct portion connects to an upper duct portion 31, arranged between a ceiling 33 of the cabinet and the electrical units, which finally debouches at the air outlet 27.

The air inlets 25 and the air outlet 27 are, when the door 11 of the cabinet is closed, in flow communication with corresponding openings 35, 37, respectively, arranged in the door. These openings are constituted by an upper air intake 37, in flow communication with the air outlet 27 and two lower exhaust openings 35, which are in flow communication with the air inlets 25 inside the cabinet.

The door 11 comprises a climate control apparatus in the form of a heat exchanger 38 through which a not shown external air flow and an internal air flow circulate, which flows are interacting in a heat exchanging manner inside the heat exchanger. The external air flow is taken from the ambient atmosphere outside the cabinet and enters the cabinet through louvres 12 a, passes by the heat exchanger 38 and leaves > the cabinet through louvres 12b, so as to return to the ambient atmosphere. The in- ternal air flow comprises the air heated by the electrical equipment and which is circulated in the cabinet.

As can be seen from fig. lc the internal air flow within the cabinet 11 is also shown. The direction of the internal air flow is indicated by the arrows. A thick arrow indi- cates a cool air flow, while a thin arrow indicates a less cool air flow. Heat generated by the electrical equipment is absorbed by surrounding air and is by means of the internal air fans 21 transferred into the duct system 23, where it is forced to rise towards the ceiling 33 in the rear duct portion 29, and is finally leaving the cabinet through the upper air outlet 27. This heated air flow enters the heat exchanger 38 inside the door 11 through the upper air intake 37 and the heat is emitted inside the heat exchanger, thus absorbed by the external air flow, which forwards it to the ambient atmosphere outside the cabinet 1 via louvres 12b. Two exhaust fans 39 exhaust the thus cooled internal air flow, when leaving the heat exchanger 38, into a space 41 between the door and the box-like body in front of the electrical equipment. This cooled internal air flow is entering the air inlets 25, and will once again absorb heat generated by the electrical equipment. This closed loop process will, during operation, continue as long as the door 11 is closed.

However, as fig. 2 depicts, this closed loop process is interrupted when the door is opened (for sake of clarity the door is omitted in this figure). Instead ambient out-door air will be drawn into the cabinet 1 by means of the internal air fans 21, absorb heat generated by the electrical equipment 17, and eventually leave the cabinet through the upper air outlet 27. However, instead of entering the heat exchanger in the door 11, the air flow vanish into the ambient atmosphere. Accordingly, the heat exchanger looses its temperature controlling function, which as mentioned earlier can lead to unfavourable situations.

According to the present invention the cabinet 1 is provided with a deflection means 50. In fig. 3a-b a deflection means in the form of a slide or a lid 50 is shown. Fig 3a shows the slide in a non-active state, while fig. 3b shows the slide in an active state, which states will be more thoroughly described below.

The slide 50 is made from a plate material and has a substantially rectangular shape. The slide comprises a planar portion 52 having two short sides and two long sides. One of said long sides and the two short sides are bent in substantially right angles with respect to the planar portion 52, thereby forming long side portion 54 and short side portions 56, respectively. The long side is bent in an opposite direction as the two short sides. This long side works as a handle for e.g. a repairman when activating or inactivating the slide 50.

Each of the short side portions 56 are provided with two pins 58 protruding perpen- dicularly from the short side portions. The protruding pins 58 are, on each short side portion 56, arranged in a line adjacent to the transition area between the planar portion 52 and the bent short side portion 56. Pins arranged on mutually same locations on each short side portions are hereinafter referred to as rear pins 58a and front pins 58b, respectively. The slide further comprises two mounting elements 60 also working as a guide means. The mounting elements 60 are adapted to be mounted on opposite side walls of the cabinet and has a length substantially corresponding to the length of the short side portions. Each mounting element comprises a longitudinal recess 62 with substantially semicircular ends 64, where the diameter of the semicircular ends 64 is greater than the width of the recess 62. The semicircular ends are hereinafter referred to as rear semicircular ends 64a and front semicircular ends 64b, respectively.

The diameter of the rear pins 58a are less than the width of the recess 62, thus the rear pins 58a can slide in the recesses 62 so as to guide the slide 50 between the non-active state shown in fig. 3a and the active state shown in fig. 3b.

The semicircular ends 64a, b work as retaining means for the slide 50, i.e. when the rear pins 58a reach the rear semicircular ends 64a or the front semicircular ends 64b, > respectively the slide 50 is retained in that position. This is accomplished due the difference between the width of the recesses 62 and the diameter of the semicircular ends 64a, b. When the rear pins 58a reach the rear semicircular ends 64a two clips 66 arranged on the mounting elements 60 can hook the front pins 58b, so as to firmly hold the slide 50 in this non-active position.

Fig. 4a-b shows the cabinet according to the present invention provided with the slide 50 shown in fig. 3a-b. The door is omitted in figure 4b for sake of clarity. As can be seen the door 11 in fig. 4a is closed and the slide 50 is in the non-active position, i.e. a position just beneath and parallel with the ceiling 33 of the cabinet, so as not to affect the internal air flow within the cabinet as indicated by the arrows. Thus, the internal air flow is accomplished exactly as described with reference to fig. lc.

Fig. 5a-b shows the cabinet in fig. 4a-b when the door is open (for sake of clarity the door is omitted in the figure 5a) and the slide 50 is in the active position. This active position implies that the slide 50 prevents the air flow to vanish into the ambient atmosphere when exiting the upper air outlet 27, which normally would be the fact when the door is open. Instead the air flow is downwardly deflected towards the air inlets (as indicated by the downwardly directed arrows) and thus an air curtain is created in front of the electrical equipment preventing cold air to be drawn into the cabinet 1. The internal air fans 21 are thus adapted to create a strong and intensive air flow exiting the upper air outlet 27. The two short side portions 56 of the slide 50 work as spacing elements, so as to create a channel that connects to the upper outlet 27 and deflects the air flow towards the air inlets 25. The air curtain prevents that cold air is drawn into the cabinet 1, instead a mixture between ambient air and air exiting the cabinet is entering the cabinet. Accordingly, the slide 50 maintain the function of a closed loop system.

Even though the invention has been described with reference to base station cabinets to be employed in a telecommunication system it is conceivable to use the cabinet with other electrical equipment and for other purposes, such as cabinets housing ' rectifier equipment in a power supply system.

The slide may be manufactured from any suitable material, such as light metal, plastic, etc.

It is also conceivable to provide means for automatically activating the slide , e.g. when the door is opened and the ambient temperature has fallen below a predetermined value.

Furthermore, the deflection means may be a sleeve coupling optionally attachable to the outlet. Such a solution enable the deflecting means to become portable and to fit . smaller outlets.

The deflection means may also be a roller blind mounted in the ceiling of the cabinet, e.g. by means of magnets.