WO1984001082A1

WO1984001082A1 - Condensation eliminator

Info

Publication number: WO1984001082A1
Application number: PCT/NO1983/000033
Authority: WO
Inventors: Jens Balchen
Original assignee: Maritime Protection A S
Priority date: 1982-09-07
Filing date: 1983-09-07
Publication date: 1984-03-15
Also published as: NO151564C; EP0118503A1; NO823017L; NO151564B

Abstract

A condensation eliminator (2) is utilized for junction boxes and similar household units to prevent undesirable condensation in the interior of the unit. The condensation eliminator comprises a cup-shaped bellows (9) disposed within a tubular body (3) which protects the bellows (9) against external influences. The bellows (9) has a mouth-like orifice which seals around an opening (7) leading into a junction box (1) or the like. A plug (8) preferably of sintered metal is inserted into the opening. The plug (8) acts as a barrier between the space defined by the bellows (9) and the interior compartment of the junction box (1). The bellows (9) reacts to pressure variations inside the junction box, and the plug (8) operates as a reducing valve in the event of a sudden increase in pressure inside the junction box and as a flame barrier in the event of a fire within the junction box. The bellows may also be arranged inside a connector box, thereby defining a chamber, the plug being inserted in a wall of the box facing said chamber.

Description

CONDENSATION ELIMINATOR.

The present invention relates to a condensation eliminator for use in connection with connector boxes, lighting fix¬ tures, spotlights, electronic components, instrumentation boxes, motors, cabinets and other housing units, for eli¬ minating undesirable condensation inside the unit. For both the user and the manufacturer of equipment such as connector boxes, lighting fixtures, etc., the formation of condensation inside the unit represents a considerable pro¬ blem. Condensation causes internal components to corrode, it may short-circuit or break the electrical contact in¬ side an instrumentation box or housing, and it can damage not only components but the unit itself, i.e., the connector box, lighing fixture, etc. Hereinafter, the generic term "housing" will be used to designate such equipment.

Both consumers and manufacturers have worked to solve the problem of condensation, but without much success. In re¬ signation, people have resorted to simply boring a drainage hole at the lowest point of the housing. This solution may be simple and practical, but it is quite dangerous, espe¬ cially if the housing is located in an area where there is a risk of explosion. The housing construction is weakened, and the drainage hole may permit explosive gases to enter the housing. The use of a drainage nipple has a weakening effect on the sealing degree of the housing. Such solutions do therefore not satisfy official safety standards.

Condensation forms inside the housing owing to variations in the ambient temperature, which in turn cause pressure variations inside the housing. At high temperatures the internal pressure in the housing will increase, causing the gas volume in the housing to expand. Cooling will result in an underpressure, and moisture will be drawn or "suctioned" into the housing. As this cycle repeats itself, water condensation forms inside the housing.

Calculation show that the volume of gas in a housing in¬ creases/decreases by 3.25% per 10°C of temperature change, The formation of condensation owing to changes in the gas

OM

^• N volume can be prevented if the volume of the housing is able to accomodate to the change in volume of the medium inside the housing. Thus, it is known to provide, as part of a wall of the housing, a flexible membrane which can expand or contract in accordance with the changes in gas volume occuring as a function of temperature. The membrane compensates for the variations in pressure and "suctioning" of moisture is eliminated.

Such a solution, however, is not entirely satisfactory in many applications of the housing units mentioned above. If a sudden increase in pressure (explosion) occurs inside the housing, the housing will be damaged, the membrane will be destroyed, and the damaged membrane will allow the flames to escape and spread. There is thus a need to improve upon the prior art condensation eliminator, and in accordance with the invention it is proposed to provide a porous, pressure resisting element, for example, made of sintered metal, as a barrier in series with the flexible member between the interior space of the housing and the exterior surroundings. Sintered metal, e.g., sintered bronze, is a preferred material, but other materials having simi¬ lar properties, such as a porous ceramic material, could also be used. What is important is that the material must be corrosion resistant, it must have a high melting point and be able to withstand the pressures that may arise, and its porosity must be satisfactory. Sintered bronze with theoretical pore size of 0.12 mm has proved extremely effec¬ tive for quenching flames (flame barrier) as pressures of

2 12 kp per cm . Sample barrier elements were subjected to explosions undertaken with 28% by volume of hydrogen in the air, each sample being tested five times, and none of the test samples allowed a fire to penetrate through the barrier. For the tests, a porous, pressure resisting element in the form of a screw plug, 1 cm in diameter and with a screw length of about 1 cm, was used.

In other words, the porous, pressure resisting element of the invention acts as a reducing valve between the interior of the housing and the external surroundings, and simultane¬ ously functions as a flame quenching component.

The porosity of the element can also be utilized to facili¬ tate water drainage. The element will in that case be mounted at the lowest point of the housing, and it may optionally be formed as a small cup for collecting the condensed water. The water so collected will gradually be forced out through the porous element during increases of the pressure inside the housing. This water will collect, at a location where it will not cause corrosion or in other ways damage the components inside the housing. The porous, pressure resistant element also has independent inventive merit, because it can be utilized alone as a barrier, i.e., without the flexible member. Used alone, the element will be mounted at the lowest point of the housing to facilitate drainage, as mentioned above, and it will also function as a flame barrier.

According to the invention, therefore, a condensation eli- minator is provided for use in connector boxes, light fix¬ tures, spotlights, electronic components, instrumentation boxes, motors, cabinets and other housing units where con¬ densation in an interior compartment of the unit is unde¬ sirable, the device also comprising a flexible member which forms a partition between the interior compartment and the external surroundings, wherein the eliminator is character¬ ized by a porous, pressure resistant element, for example of sintered metal, which is arranged as a barrier in series with the flexible member, between the interior compartment and the external surroundings.

A preferred embodiment of the invention is characterized in that the porous pressure resistant element is arranged be¬ tween the said compartment and the flexible member.

Another preferred embodiment of the invention is character¬ ized in that the porous pressure resistant element is mounted in an opening in an outer wall of the housing, the flexible member being a bellows inside the housing and de¬ fining a chamber towards the openings.

O PI A further preferred embodiment of the invention is character¬ ized in that the porous, pressure resistant element is in¬ serted in an opening in an outer wall of the housing, and in that the flexible member comprises a cup-shaped bellows whose mouth is sealed to the outside face of the outer wall, around said opening.

Preferably, the porous, pressure resistant element in this embodiment is a screw plug which is simply screwed into threads provided in the wall opening.

In practice, it may be advantageous to produce the condensa¬ tion eliminator as an independent unit, comprising an assembly of both the porous, pressure resistant element and the flexible member, the unit being formed as a mounting unit for connection with the housing.

An independent unit of this type may be formed, for instance, essentially as a tubular body within which the flexible member is mounted, one end of the tubular body being formed for connection to an opening in an outer housing wall. In that case, said one end of the tubular body is formed with a screw union for screwing into a threaded opening in said outer wall. The screw union can also be internally threaded for .receiving the porous, pressure resistant element that is formed as a screw plug.

In a practical embodiment, the flexible member is a pressure- compensating bellows, shaped like a hat, and the rim around the mouth of the bellows is clamped to and retained by the tubular body at about the middle of its length. The ad¬ vantage of this is that a bellows of this type can utilize the entire interior space in the tubular body as it expands and contracts to compensate for the changes in gas volume in the interior of the housing. In an especially preferred embodiment, the tubular body is composed of two parts which are joined together, and rim surrounding the mouth of the bellows is clamped in the joint between the two parts. The tubular body may then easily be opened for replacing the bellows if needed, or to remove any water which has seeped

C PI out through the porous element and collected in the space defined by the bellows and the porous element.

The invention will be descrioed in greater detail in the following with reference to the accompanying drawings, which show three preferred embodiments of the invention.

Figure 1 shows a connector box with a condensation eliminator according to the invention mounted thereon.

Figure 2 in partial cross section shows a second embodiment of a condensation eliminator according to the invention, mounted in the wall of a housing, and

Figure 3, in partial section, discloses a connector box wherein the invention is used.

Figure 1 shows a connector box 1. The box has several bores for the introduction of cables, and in one of these a conden¬ sation eliminator 2 is mounted, as may be seen in the drawing.

The condensation eliminator 2 is an independent unit consist- ing of a tubular body 3. One end wall 4 of the tube is closed and a screw union 5 is attached thereto. The screw union 5 is screwed into a threaded opening 6 in the wall of the box 1. The screw union 5 has an internally threaded through bore 7 which also passes through the end wall 4, as seen in Figure 1. A screw plug 8 made of sintered metal, preferably sintered bronze, is screwed into the threaded bore 7. Mounted within the tubular body 3 is a cup-shaped bellows 9 whose mouth is sealed to the inside face of the end wall 4, so that the mouth of the cup-formed bellows 9 surrounds the bore opening 7.

The bellows 9 will react to pressure variations inside the box 1, expanding if the pressure increases and contracting when the pressure decreases. Pressure variations in the box 1 will thus be equalized, and condensation will not form inside the box. The sintered plug 8 will operate as a re¬ ducing valve, preventing sudden pressure increases inside the box from damaging the bellows 9. The sintered plug also operates as a flame quenching component.

Due to its location inside the tubular body 3, the bellows

O 9 is protected from external forces that could damage- it.

Figure 2 shows a condensation eliminator 10 which is mounted at the lowest point of a connector box (shown only as a part of the bottom wall 11 of the connector box) . As in the embodiment illustrated in Figure 1, the condensation eliminator 10 is constructed as an independent unit, but in this case the tubular body is a two-part component, consist¬ ing of two tubular halves 12 and 13. Each half-tube 12,13 is provided with a respective flange collar 14, 15 with mating threads so that the collars may be screwed together, as shown in Figure 2. One tubular half 12 is closed at one end by an end plate 16 formed with a screw union 17 which is screwed into the threaded opening 18 in the box wall 11. The screw union has an internally threaded through bore 19. A plug 20 corresponding to the plug 8 in Figure 1 is screwed into the threaded bore 19.

The second tubular half 13 is cup-shaped, as shown, and at least one opening 21 is provided in the bottom wall thereof.

A pressure-compensating bellows 22 is clamped between the two collars 14,15 by the rim surrounding its mouth opening 23. The bellows 22 is shown in an intermediate position in the drawing; in accordance with changes in pressure, the bellows 22 can move from a position in which it rests against or is reversed in a direction toward the bottom wall of the tubular half 13, and an upper position in which the bellows 22 rests against or is reversed in a direction toward the end plate 16. The bellows 22 thus utilizes the entire volume of the tubular body consisting of the two halves 12, 13.

The materials selected for the bellows 9, 22 should provide a flexible bellows which can react to slight differences in pressure. In a practical embodiment, the bellows might have a wall thickness of 0.4 mm or less; this will give a very flexible bellows which reacts to small pressure differences (about a 20 mm water column) .

The porous, pressure resistant element, shown in the exemplary embodiments as the screw plugs 8, 20, is preferably made of sintered bronze having a theoretical pore size of 0.12 mm.

In the embodiment illustrated in Figure 2, the condensation eliminator is disposed at the lowest point of a housing, for example at the bottom wall 11 of a connector box as shown. The condensation eliminator may be used as a water collect¬ ing means in a housing placed in an area where explosions may occur. The condensation eliminator is then placed at the lowest point of the housing. The screw plug will pro¬ tect against flame spreading out of the housing and at the same time the bellows will protect against dirt etc. as well as dangerous gases entering the housing.

The volume of the condensation eliminator, i.e., the change in volume which the bellows permits, is determined by cal¬ culations based on the volume of the interior compartment which is to be protected.

Several modifications of the illustrated embodiments may be made without departing from the scope of the invention. Instead of the "countersunk" placement of the screw plug 20 in the threaded bore 18 in the bottom wall 11 of the box shown in Figure 2, the screw plug 20 could also be flush with the inside face of the bottom wall 11 and have a de¬ pression or cup-like in its end surface for collecting any condensation water. The screw plugs 8, 20 do not necessari- ^• ly have to be formed in the shown plug shape with an end collar. The end collar could be eliminated, and the porous, pressure resistant element may also have other manifestations which will be readily apparent to a person skilled in the art on the basis of the teachings contained in this patent specification.

Figure 3 doscloses a connector box 25 wherein a bellows or membrane 26 is mounted as shown, thereby defining a chamber 27 towards an opening 28 in the box wall. A screw plug 29 of sintered bronze is threaded in the opening 28. Above the bellows 26 there is an internal partition wall 30 having openings 31. This partition wall forms a partition between the useful volume of the box and the "breathing space" of the bellows. The plug 29 is porous and allows for the

OMP "breathing" of the bellows. An explosion in the box may destroy the bellows but the plug will have the same protect¬ ive functions as in the embodiments of Figures 1 and 2. The bellows is interchangeable, being fastened between box portions 32, 33.

Claims

P a t e n t C l a i m s.

1. A condensation eliminator for use on connector boxes, lighting fixtures, spotlights, electronic components, instru¬ mentation housings, motors, cabinets and other housing units wherein condensation in an interior compartment of the unit is undesired, comprising a flexible member which forms a partition between the interior compartment of the unit and the external surroundings, characterized in that a porous, pressure resistant element, for example of sintered metal, is provided as a barrier in series with the flexible member, between the interior compartment and the external surround¬ ings.

2. A condensation eliminator according to claim 1, characterized in that the porous, pressure resistant ele¬ ment is arranged between the interior compartment and the flexible member.

3. A condensation eliminator according to claim 1, characterized in that the porous, pressure resistant ele¬ ment is inserted in an opening in an outer wall of the housing, the flexible member being a bellows inside the housing and defining a chamber towards the said opening.

4. A condensation according to claim 2, characterized in that the porous, pressure resistant element is inserted into an opening in an outer wall of the housing, and that the flexible member is a cup-shaped bellows whose mouth is sealed to the outside face of the outer wall, around the opening therein.

5. A condensation eliminator according to claim 3 or 4 , characterized in that the porous, pressure resistant element is a screw plug.

6. A condensation eliminator according to one of the preceding claims, characterized in that the porous, pressure resistant element and the flexible member are assembled in an independent mounting unit.

7. A condensation eliminator according to claim 7, characterized in that the unit is preferably formed as a

OMP

S tubular body within which the flexible member is mounted, one end of the tubular body being formed for connection to an opening in said outer wall of the housing.

8. A condensation eliminator according to claim 7, characterized in that said one end of the tubular body is formed with a screw union for connection to a threaded opening in said outer wall of the housing.

9. A condensation eliminator according to claim 8, characterized in that the interior of the screw union is formed for receiving the porous, pressure resistant ele¬ ment.

10. A condensation eliminator according to one of the claims 7-9, characterized in that the flexible member is a pressure-compensating bellows of hat-like shape, the rim surrounding its mouth opening being clamped to and retained by the tubular body at about the middle of its length.

11. A condensation eliminator according to claim 10, characterized in that the tubular bodv is a two-part com- ponent, intended to be joined together with the rim of the pressure-compensating bellows clamped in the joint between the two parts.