Fire extinguishers – Fluid systems – Distributing systems
Reexamination Certificate
1999-12-29
2002-07-09
Morris, Lesley D. (Department: 3752)
Fire extinguishers
Fluid systems
Distributing systems
C169S020000, C169S056000, C169S060000, C169S061000, C239S208000
Reexamination Certificate
active
06415870
ABSTRACT:
FIELD OF THE INVENTION
This application is the national phase under 35 U.S.C. §371 of PACT International Application No. PACT/JAP99/01899 which has an International filing date of Apr. 9, 1999 which designated the united states of America.
This invention relates to an automatic extinguisher system for buildings, etc., and more particularly to a wet-type sprinkler system of which secondary pipelines are filled with water in a normal condition.
BACKGROUND ART
Hitherto, sprinkler systems are in widespread use in buildings, especially in large-scale buildings. In known sprinkler systems, sprinkler heads for fire-extinguish purpose are arranged on ceilings of buildings. The sprinkler system is composed essentially of the sprinkler heads each of which is individually actuated in response to an ambient thermal condition, a feed pump as a water supply unit, and a feed pipe arrangement including primary pipelines and secondary pipelines.
The primary pipeline(s) of the feed pipe arrangement is arranged in a manner perpendicularly rising from the feed pump, to reach the heights of floors. The secondary pipelines are connected to the primary pipeline such that water flows through the pipelines. The secondary pipeline(s) generally extends in the horizontal direction on each floor, and then it is branched and hung-down in the almost perpendicular direction to form hang-down pipe portions, which respectively communicate with the sprinkler heads.
The sprinkler systems with such structures as mentioned above are divided into wet-type sprinkler systems and dry-type sprinkler systems. These two types of the system are different in the following point: That is, in the former type, not only the primary pipelines but also the secondary pipelines are filled with water, and this state is called “normal condition”. On the other hand, in the latter type, the secondary pipelines are not filled with water, i.e. They are filled with air (in other words, only the primary pipeline is filled with water).
In the known wet-type sprinkler system, water charged in the secondary pipelines in the same manner as in the primary pipeline is constantly kept pressurized, e.g. At 7 to 8 kg/cm
2
. By this setting, the system has an advantage in that water discharge is quickly performed when the sprinkler head is actuated at the breaking out of fire. In general cases, however, the opening and shutting of the sprinkler heads are controlled not systematically but individually at the ceiling portions at which the sprinkler head are arranged. For example, when a sprinkler head is exposed to heat, a sealed portion thereof is melted, and the sprinkler head comes ready to jet water. Accordingly, in the event that the sprinkler head is actuated on an occasion other than an actual fire, for instance failure of the system or intentional destruction of the same, there is an inconvenience that pressurized water is instantly injected to drench the area around the sprinkler head. For example, when the sprinkler head functions in a wrong way in an office building, documents, computers, elevator systems, etc. Have incurred a huge amount of damage.
To cope with the inconvenience, a wet-type sprinkler system having an additional function of a so-called preliminary operation has been employed. The above-mentioned sprinkler system is provided with a valve section between the primary pipeline and each secondary pipeline. The valve section is caused to normally be closed, and the valve is opened by a control section of the system only when the control section receives a fire-detection signal from a fire sensor (which functions more quickly than the sprinkler head), followed by feeding a large volume of high-pressure water to the secondary pipelines as the preparation for actuating sprinkler heads.
This system only allows water in the secondary pipeline to be discharged in the event of wrong-way-function of the sprinkler heads, and therefore damage can be minimized compared with the prior system. However, the water in the secondary pipeline alone still causes a considerable amount of damage.
On the other hand, the dry-type sprinkler system has been developed to eliminate such damage. Namely, in this system, the secondary pipeline is filled with air which is pressurized at about 2 kg/cm
2
, in place of water. Therefore, even if the sprinkler head undergoes a failure, only air is discharged, so that damage caused by water can be avoided. This is the largest advantage of the dry-type sprinkler system.
The dry-type sprinkler system requires a work of dewatering or draining the secondary pipe when water injection is carried out on trial. Even after the dewatering work, however, not a little volume of water remains in the hang-down pipe portions if each of the sprinkler heads is not actuated. As a result, it tends that the hang-down pipe portion in the vicinity of a boundary between water and air corrodes, and the corrosion once obtained easily spreads resulting in perforation. To eliminate the corrosion, periodical maintenance and repair are required, or a pipe formed of a special material becomes indispensable, and therefore the defrayal on a managing company is not small.
Further, there is such a tendency that a very small volume of air leaks at a junction of the pipelines, etc., compared with the case where water is stored, so that decrease in pressure of air is relatively fast, which requires frequent addition of air into the secondary pipelines by means of a compressor or the like. The supplement of air, however, disadvantageously brings about supply of oxygen, thereby promoting the formation of rust.
Still further, when water injection for actually extinguishing fire is carried out, water pressurized at about 7 to 10 kg/cm
2
flows from the feed pump into the secondary pipelines upon opening of the valve section. If air remains at the corners or upper portions in the pipeline, however, an effective cross section of flowing water in the pipeline is reduced, which can unfavorably prevent water from flowing.
Even further, when water highly pressurized by the feed pump is supplied to the sprinkler heads which have not yet been actuated, air stored therein beforehand is compressed to become high pressure air, thereby causing such a danger that elastic force of the high pressure air can blow off components of the sprinkler heads. In addition, when a fire actually breaks out, water cannot be discharged until the charged air is completely drawn off. As a result, it is pointed out that the dry-type sprinkler system is inferior to the wet-type sprinkler system in immediacy at an initial extinguishing operation which is the essential object of sprinkler systems.
To cope with the various inconveniences of the known sprinkler systems, particularly to enhance a rust prevention performance, an extinguishing fixture is proposed, for example, in Japanese Patent Kokai Publication Hie 10(1998)-234881. According to the extinguishing fixture, in place of air, inert gas is charged in a pipe portion of the secondary pipeline, at a location immediately above the sprinkler heads of the wet-type sprinkler system. By using inert gas such as nitrogen gas, rusting and development thereof can be effectively prevented in both the wet-type sprinkler system and the dry-type sprinkler system.
Further, there is disclosed a water flow detecting system for a wet-type sprinkler system, for example, in Japanese Patent Kokomo Publication No. Hie 7(1995)-12382, in which fluid in the secondary pipelines is brought to have a low pressure (but not negatively pressurized) than water in the primary pipelines. In this case, if a fire actually breaks out, the low-pressure water in the secondary pipelines is immediately discharged, so that it is considered that this system is effective for initial extinguishing operation.
However, in the above mentioned extinguishing fixture disclosed in Japanese Patent Kokai Application Hie 10(1998)-234881, in which inert gas has been charged, if the sprinkler head is actuated in a relatively small and tightly closed room, nitrogen gas fills the room, wher
Birch & Stewart Kolasch & Birch, LLP
Morris Lesley D.
Nguyen Dinh Q.
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