GB2028127A

GB2028127A - Fire extinguisher

Info

Publication number: GB2028127A
Application number: GB7833562A
Authority: GB
Original assignee: Hammargren & Co AB
Current assignee: Hammargren & Co AB
Priority date: 1978-08-16
Filing date: 1978-08-16
Publication date: 1980-03-05
Also published as: GB2028127B

Abstract

A fire extinguisher of the type discharging a jet of extinguishing gases produced in the extinguisher by the combustion of a pyrotechnical charge. The extinguisher has a housing 1 connected at one end to a discharge nozzle 3 and provided at the other end with a combustion chamber 4 containing the pyrotechnical charge 5 and having a narrow outlet 7 into the interior of the housing. The space surrounded by the housing between the combustion chamber and the discharge nozzle constitutes a gas chamber 15 the volume of which substantially exceeds the volume of the combustion chamber. Powder or liquid extinguishant may be mixed with the discharged gases. <IMAGE>

Description

SPECIFICATION Fire extinguisher This invention relates to a fire extinguisher comprising a housing, a discharge nozzle connected to said housing, a combustion chamber arranged within said housing, said combustion chamber having a narrow outlet into said housing, a charge contained in said combustion chamber, said charge being composed so as on ignition to burn with the development of gaseous reaction products only which are neither combustible nor oxidizing, and means operable from outside the housing for igniting said charge.

While fire extinguishers of this kind offer the possibility of obtaining a favourable ratio of the weight of the extinguishing gas to the total weight of the extinguisher, the existing designs of extinguishers of this kind are unsatisfactory in various respects and have found little or no practical use.

The invention has for its object to provide an improved fire extinguisher of the kind above specified, which satisfies all practical requirements in respect of simple and safe operation, adequate extinguishing action etc.

and thus clears the way for a wider practical application of this kind of extinguishers. More particularly, the invention has for an aim that the extinguishing gas during the combustion of the charge is discharged from the nozzle as a quiet and even jet having a "stiffness" and a maximum effective length governed by the choice of the outlet area of the discharge nozzle.

According to the invention, the combustion chamber and the discharge nozzle above specified are arranged at opposite ends of the housing, the space surrounded by said housing between the combustion chamber and the discharge nozzle constituting a gas chamber the volume of which substantially exceeds the volume of the combustion chamber.

To improve the extinguishing action, or to adapt the same to special fire conditions, the extinguisher according to the invention may be provided with means for the admixture of a fire extinguishing powder to the combustion gases and/or with means for ejecting a fire extinguishing liquid under the action of the gas pressure in the gas chamber.

The invention shall now be described in more detail with reference to the accompanying drawings which show by way of example a number of fire extinguishers embodying the invention.

In the drawings, Figure 1 is a longitudinal sectional view of a first embodiment of the invention, Figure 2 is a longitudinal sectional view of a modified form of the embodiment of Fig. 1, Figure 3 is a side view, partly in longitudinal section, of a third embodiment of the invention, Figures 4 and 5 are, respectively, longitudinal sectional views of a fourth and a fifth embodiment of the invention, Figure 6 shows a longitudinal section of the middle part of a modified form of the embodiment of Fig. 5, and, Figure 7 is a side view, partly in section, of still another form of the extinguisher according to the invention.

The extinguisher of Fig. 1 consists of a tubular container 1 closed at one end by a rear wall 2 and provided at the other end with a conically tapering discharge nozzle 3. A thick-walled tube 4 of heat insulating material is closely fitted into the rear part of the container 1 in front of the rear wall 2. The tube 4 contains a charge 5 pressed or cast into the tube 4 so as to tightly engage the inner wall thereof. A throttling disc 6 is fitted into the wall of the container 1 at the front end of the tube 4, said throttling disc having a narrow central orifice 7. The space contained between the throttling disc 6 and the discharge nozzle 3 constitutes a gas chamber 1 5. One end of a fuse 8 is clamped or otherwise firmly attached between the throttling disc 6 and the front face of the charge 5.

The other end of the fuse is connected outside of the orifice of the discharge nozzle 3 to a friction igniter 9 connected by a string 10 to a pull ring 11. A cap 1 2 fitted on the container 1 protects the friction igniter, with its string and pull ring, against accidental operation and also serves to prevent humidity from entering the container. If desired, the cap 1 2 may contain one or more pieces of a drying agent.

When operated the container is grasped by the handle 1 3. A heat insulating coating 1 4 on the part of the container which is adjacent to the handle protects the hand of the operator against the heat radiation of the container wall.

The charge 5 may for instance consist of compressed black gunpowder or of any other of the compositions used for the propulsion of rockets, for instance a composite powder made of a mixture of ammonium perchlorate and a liquid, hardenable binder moulded into shaped pieces by casting or extrusion and subsequently hardened. In a composite powder of this type, the ammonium perchlorate serves as an oxygen donor and the hardened binder as an oxygen acceptor during the combustion process.

During the combustion process, the charge 5 is subjected to a pressure equal to the sum of the atmospheric pressure, the pressure drop in the discharge nozzle 3, and the pressure drop in the throttling disc 6. In this sum, the last-mentioned pressure drop forms the dominating term, the orifice of the throttling disc being much narrower than the nozzle 3.

The rate of combustion of the charge is a function of the pressure acting on the charge.

It is therefore possible to obtain a desired rate of combustion, or a desired duration of the combustion period, by a proper choice of the diameter of the orifice of the throttling disc.

The optimal combustion period varies with the fire conditions which the extinguisher will have to deal with and amounts as a rule to not less than some seconds and not more than about twenty seconds. The speed of the gas jet, which determines the "stiffness" and the largest useful length of the jet, varies with the pressure drop in the discharge nozzle 3 and can, therefore, be adjusted by the choice of the orifice area of the nozzle. The excess pressure in the gas chamber 15, which is equal to the pressure drop in the discharge nozzle, is comparatively low and therefore allows the use of a comparatively thin material for the wall of the container. The material does not have to be very heat resistant, the material being subjected to the hot gases produced by the burning charge for a short period only. It is, for instance, possible to use unalloyed steel sheet or organic materials.The part of the container 1 which encloses the gas chamber 1 5 may be provided with an inner coating of heat insulating material.

When the extinguisher is to be used, the operator grasps the handle 1 3 of the extinguisher with one hand, removes the cap 1 2 with the other hand, ignites the fuse 8 by pulling the ring 11 away from the nozzle, and directs the nozzle towards the seat of the fire. The burning period of the fuse 8 is preferably of the order of one or two seconds.

It is, however, also possible to mount the extinguisher with a permanent direction against a potential seat of fire, for instance the carburettor of a gas motor. In that case, the manual igniting device described is preferably replaced by an automatic igniting device. For instance, an easily ignited pyrotechnical charge connected to the charge 5 of the extinguisher by a rapid fuse may be arranged near the potential seat of fire. According to another possibility, a sensing device reacting to a fire (for instance a photoelectric cell, a smoke detector or a bimetal element) is arranged to actuate an electric igniter engaging the charge 5 or connected to the charge by a fuse.According to still another possibility, a frictional igniter may be arranged to be operated by a spring released by a combustible element, for instance a nitrated cotton string, arranged to be burnt off by the heat of the fire. These and similar devices are obvious to those skilled in the art and do not have to be shown or explained in detail.

In the modification shown in Fig. 2, the charge 1 6 is enclosed in a pressure-resistant capsule 1 7 of a thermally insulating material, the front wall 1 8 of which is provided with a narrow orifice 1 9 and performs the same function as the throttling disc 6 of Fig. 1.

Fig. 3 shows an extinguisher 20 of the same type as the one represented in Fig. 1 or 2 but supplemented with a device for the ejection of a fire extinguishing powder. Said device consists of a container 21 containing a supply 22 of the fire extinguishing powder and connected to the extinguisher 20 by two tubes 23, 24. One tube extends between the gas chamber 25 of the extinguisher 20 and a point a little above the bottom 26 of the container 21. The other tube 24 extends only slightly below the upper wall 27 of the powder container 21 and is provided at its other end with a discharge section 30 arranged coaxially within the discharge nozzle 28 of the extinguisher 20 so as to form together with said nozzle an annular channel 29.When the charge of the extinguisher 20 is burning, a part of the current of combustion gases will flow from the pressure chamber 25 through the tube 23, the powder container 21 and the tube 24. The passage of the gases through the container 21 will result in the formation of a powder-gas-mixture which is ejected through the tube 24 and mixes with the gas current discharged through the annular channel 29.

The powder 22 may consist of any mixture or composition known to possess fire extinguishing or flame damping properties, for istance any powder composition used in the socalled powder extinguishers employing compressed air or compressed nitrogen as an ejecting agent. One example is a composition consisting mainly of potassium sulphate, with minor additions of chlorides and other substances. A second example is a composition consisting mainly of sodium bicarbonate.

The fire extinguisher of Fig. 4 has a cylindrical wall 35, a bottom 31 and a conical top 32 provided with a curved nozzle 33. A substantially cylindrical, pressure resistant capsule 34 consisting of a heat insulating material and enclosing a compact charge 37 rests on the inside of the bottom 31. An annular member 36 is fitted between the lower part of the capsule 34 and the cylindrical wall 35 to maintain the capsule 34 properly centred with respect to the wall 35. The casule is provided below with four angularly spaced, radial outlets 38. A supply of fire extinguishing powder occupies the annular space between the capsule 34 and the wall 35 and part of the space above the top of the capsule. A fuse 40 extends from the lower end of the charge 37 through one of the outlets 38, the gas chamber 41 and the discharge nozzle 33 to an igniter 44 attached to the outer face of the container top 32. A plastic foil cap 42 applied on the end of the discharge nozzle 33 prevents humidity from entering the container. The container is mounted by means of a clamp member 43 near a potential seat of fire.

On ignition of the charge 37, the combustion gases are discharged through the outlets 38 and pass through the powder layer 39, producing a mixture of gases and powder which is discharged through the nozzle 33.

The extinguisher shown in Fig. 5 has a cylindrical wall 45, a conical top 46 and a conical bottom 47. A curved discharge nozzle 48 is fitted in the top 46. A tubular extension 50 fitted in the bottom 47 and provided below with a bottom 49 contains a pressure resistant capsule 51 consisting of heat insulating material and enclosing a compact charge 52. The upper end wall 53 of the capsule 51 is provided with a gas outlet 54. A fuse 55 engaging the upper face of the charge 52 extends through the outlet 54, the gas chamber 56 of the extinguisher and the discharge nozzle 48 to an igniter (not shown). A perforated partition 57 fitted in the cylindrical wall 45 supports a supply 58 of fire extinguishing powder. A thin sheet of paper 59 resting on or glued on to the upper face of the partition 57 prevents the powder from running through the holes in the partition.When the charge 52 is burning, the combustion gases penetrate through the holes in the partition 57 and through the powder supply, so that a gaspowder-mixture is formed and ejected through the discharge nozzle 48.

In the modification of the embodiment of Fig. 5 shown in Fig. 6, the partition 60 is provided with a piece of tubing 61 extending through the powder supply 65, and with a baffle plate 63 fitted at the lower end of the vertical passage formed by said piece of tubing 61. When the charge is burning, one part of the combustion gases will pass through the baffle plate 63 and the piece of tubing 61, while another part will penetrate into the powder supply through the holes 64 of the partition 60. This arrangement provides the possibility of obtaining any desired relation between the rate at which the powder supply is discharged and the rate at which the charge is consumed by a corresponding choice of the relation between the area of the orifice in the baffle plate 63 and the total area of the holes 64 of the partition 60.

Fig. 7 shows a fire extinguisher of the basic type represented in Fig. 1 or 2 supplemented with a device for ejecting a fire extinguishing liquid together with the gaseous combustion products. Said device comprises a container 67 containing a supply 68 of the fire extingu ishing liquid and connected to the extingu isher body 66 by two tubes 69, 70 fitted in the top 72 of the container 67. One tube 69 connects the upper end of the container 67 to the gas chamber 71 of the extinguisher. The lower extremity of the other tube 70, which is located at a level slightly above the bottom 74 of the liquid container 67, is provided with a baffle plate 73. At the other end, the tube 60 has an end portion 76 arranged coaxially with the discharge nozzle 75 so as to form together with the nozzle an annular channel 77 for the combustion gases emerging from the gas chamber 71.

When the charge is burning, the gas pressure in the gas chamber 71 of the extinguisher is transmitted through the tube 69 to the liquid container 67, whereby the liquid is pressed out through the tube 70 at a rate determined by the gas pressure and by the area of the orifice of the baffle plate 73. This arrangement provides the possibility of obtaining any desired relation between the rate at which the liquid container 67 is emptied and the rate at which the charge is consumed.

A thin foil member 78, 79 is attached to the upper orifices of the tubes 69, 70, respectively, to prevent evaporation or leakage of the liquid without obstructing the passage of gas and liquid, repectively, in the operation of the extinguisher.

The charges shown in Figs. 1, 2, 4 and 5 have the shape of a cylinder, the cylindrical surface of which is covered, and are designed for so-called front combustion, during which a substantially plane combustion front is gradually displaced at right angles to its plane. The invention is, however, not limited to the use of charges of this type. An extinguisher for putting out a fire which requires an extra strong blast of extinguishing gas may have to be equipped with a charge shaped so as to provide a large combustion area. The charge may, for instance, have a star-shaped crosssection.

Claims

1. A fire extinguisher comprising a housing, a discharge nozzle connected to said housing, a combustion chamber arranged within said housing, said combustion chamber having a narrow outlet into said housing, a charge contained in said combustion chamber, said charge being composed so as on ignition to burn with the development of gaseous reaction products only which are neither combustible nor oxidizing, and means operable from outside the housing for igniting said charge, in which said combustion chamber and said discharge nozzle are arranged at opposite ends of said housing and in which the space surrounded by said housing between the combustion chamber and the discharge nozzle constitutes a gas chamber the volume of which substantially exceeds the volume of the combustion chamber.

2. A fire extinguisher as claimed in Claim 1 which contains a supply of fire extinguishing powder arranged to be traversed by at least part of the gas current produced by the burning charge, whereby said powder is carried away by the gas and the resulting mixture of gas and powder is ejected through said discharge nozzle.

3. A fire extinguisher as claimed in Claim 2 in which said powder supply is arranged within said gas chamber.

4. A fire extinguisher as claimed in Claim 1 which is further provided with a container containing a fire extinguishing liquid, said container being at its upper end connected to said gas chamber and being at its lower end connected to a discharge conduit the other end of which is arranged in such a relation to said discharge nozzle as to cause the liquid discharged through said discharge conduit to mix with the gas discharged by said discharge nozzle.

5. A fire extinguisher substantially as herein described with reference to the drawings.