Compact fog generating device

Abstract

Power-efficient, compact fog machine. The heat exchanger has an internal geometry consisting of a stepped pin inserted in a correspondingly stepped external jacket. The diameter of the pin (and correspondingly the internal diameter of the jacket) is larger near the inlet and thinner near the outlet. Alternatively, the diameter of the pin (and correspondingly the internal diameter of the jacket) is smaller near the inlet and larger near the outlet. Overcomes technical limitations due to tradeoff between size of metal heat exchanger and number of holes necessary for fog generation.

Description

[0001] COMPACT FOG GENERATING DEVICE

[0002] The present invention refers to a compact fog generating device , capable of producing a very dense fog, to increase the safety level of an alarm system .

[0003] Fog generating devices are designed to produce a very thick fog that completely impedes vision . To achieve this result , a fog fluid must be rapidly evaporated and subsequently condensed into microdroplets . The si ze of these droplets is large enough not to be crossed by light without interfering with it and consequently causing a dif fusion phenomenon ( scattering) which precludes visibility .

[0004] These devices are therefore suitable for foiling a theft or robbery, as they quickly produce a quantity of fog which, for a long time , completely prevents vision, so the thief or robber, disoriented, often gives up on his intent .

[0005] To minimi ze the possibility of the thief completing the theft or causing damage , it is necessary that the saturation of the environment occurs in the shortest possible time . To obtain this result , it is necessary to administer a high power to the fluid, equal at least to the speci fic evaporation heat per the number o f units of mass of liquid required .

[0006] The power needed to have adequate ef fects ranges from a few kW, for modest performance machines , to tens or even hundreds of kW for higher-end machines . It is clear that these powers cannot be supplied by the electricity supplier ' s meters , but must be extracted from an energy "warehouse" located on site . The dimensions of thi s warehouse in terms of kWh represent the maximum quantity of fog fluid that can be evaporated by the apparatus .

[0007] This energy is stored in thermal form in the sensible heat o f a metallic mass . The mass is preferably heated by an electrical resistance over a suf ficiently long time so as not to require high power, the accumulated heat being rapidly released when it is crossed by a fog fluid which passes through the coils and / or gaps created inside it .

[0008] The creation of these internal circuits is critical for the correct extraction of energy from the accumulator : this extraction must be carried out in a very short time .

[0009] Currently, the circuits are made by deep drilling connected in the upper and lower part of the accumulator by means of transversal holes and welding . This work is very long and expensive , both in terms of execution time and in terms of tools and material waste .

[0010] Normally, the flow passes through the holes in " series" , as the holes in "parallel" are not crossed by the flow in a homogeneous way . This dif ference increases during delivery, creating areas of the exchanger that are too cold and others with energy that remains unused . By creating a " series" path, it is instead necessary to al so increase the si ze of the passages in order not to have an excessive loss of load .

[0011] Furthermore , the hole space is subtracted from the thermal mass of the accumulator .

[0012] As the power required increases , the number of holes must increase in order to increase the exchange surface and a technical / economic limit for construction is soon reached .

[0013] The devices currently in use are technical and economic compromises , which make scaling the application of the technology to extremes difficult and uneconomical. Furthermore, the use of materials with high thermal conductivity such as aluminium, while on the one hand enabling the extraction of heat, on the other causes the fluid to vaporize too quickly, creating a gas cushion that insulates from thermal contact the drop of fluid. This is known as the "Leidenfrost effect". Conversely, if the metal has a low thermal conductivity, the temperature of the surface, in contact with the fluid, suddenly decreases. The Leidenfrost effect is eliminated, but the possibility of quickly extracting heat from the metal parts far from the channel is reduced.

[0014] Documents WO-A1-99 / 33326 and WC-A1-2019 / 058400 describe heat exchangers according to the prior art .

[0015] Object of the present invention is solving the aforementioned prior art problems by providing a new solution that overcomes the aforementioned limitations, allowing the creation of exchangertype devices of any size, and also exchangers with a reduced size, less than 5 kg, with a greater efficiency of fog generated in a single shot, in relation to the weight of the metal mass.

[0016] For this purpose, it must be noted that a straight exchanger (consisting of a cylindrical pin and related jacket) , if sized with an abundant gap (with respect to the mass and the exchange surface) , allows a good flow speed but a bad heat exchange and any drops of liquid will be carried by the vapor flow in liquid form to the exit. However, if it is sized correctly, given that these are small exchangers, the space between the pin and the jacket must be less than 0.2 mm, making the system very susceptible to blockages. Even the slightest oxidation or internal deposit will significantly change performance.

[0017] For these reasons, a boiler is envisaged with a stepped internal geometry, as regards both the central pin and the external jacket: this surface between the steps can be flat or machined / stepped or corrugated.

[0018] This solution, which allows for a much greater distance between pin and jacket, introduces little pressure drop and therefore a high heat exchange speed with less risk of clogging.

[0019] The above and other objects and advantages of the invention, as will appear from the following description, are achieved with a device such as that described in claim 1. Preferred embodiments and non-trivial variations of the present invention form the subj ect matter of the dependent claims .

[0020] It is understood that all attached claims form an integral part of this description .

[0021] It will be immediately obvious that countless variations and modi fications can be made to what i s described ( for example relating to shape , dimensions , arrangements and parts with equivalent functionality) without departing from the scope of the invention, as appears from the attached claims .

[0022] The present invention will be better described by a preferred embodiment thereof , provided by way of example and not by way of limitation, with reference to the attached drawings , in which :

[0023] - Figure 1 shows the compact fog generating device with noz z les and a central housing for the insertion of a cartridge heating resistor, according to a possible embodiment of the present invention;

[0024] - Figure 2 shows the compact fog generating device according to the invention without noz zles ;

[0025] Figure 3 shows a perspective view of the j acket of the compact fog generating device according to the invention; - Figure 4 shows a sectional view of the pin of the fog generating device according to the invention; and

[0026] - Figure 5 shows a side view of an alternative embodiment of the compact fog generating device of the invention, with a stepped or corrugated external surface .

[0027] Referring to the Figures , the compact fog generating device 1 of the exchanger type of the invention, in one of its first preferred embodiments , includes at least one pin 3 ( cylindrical or parallelepiped or other geometric shape ) contained within and operationally connected to at least one external j acket 5 ( cylindrical or parallelepiped-shaped or other geometric shape as long as it is capable of moving telescopically with the pin 3 ) , this fog generating device 1 also being equipped with inlet means 7 and outlet means 9 of a fog fluid .

[0028] As shown in Figure 1 , the compact fog generating device 1 is also equipped with a central housing 14 for the insertion of a cartridge heating resistor, although it is possible to heat the device from the outside , with a flat mica resistor or with a spiral armoured resistance . In an innovative way, the pin 3 has an external surface with a substantially stepped shape , with a larger diameter at the inlet means 7 and a smaller diameter at the outlet means 9 ; and the external j acket 5 has an external surface ( the one in contact with the pin 3 ) of a substantially stepped shape , with a larger diameter and smaller thickness in correspondence with the inlet means 7 and a smaller diameter and greater thickness in correspondence of the outlet means 9 .

[0029] A mirrored configuration of the fog generating device of the invention (not shown) is also possible , in which the pin has its external surface of a substantial ly stepped shape , with a smaller diameter in correspondence with the inlet means and a larger diameter at the outlet means ; and the external j acket has its internal surface ( the one in contact with the external surface of the pin) of a substantially stepped shape , with a smaller diameter and greater thickness in correspondence with the inlet means and a greater diameter and lesser thickness in correspondence of the outlet means .

[0030] Preferably, the device 1 is assembled by screwing the pin 3 inside the external j acket 5 , but other forms of assembly are also possible , such as welding or sealing gaskets or putty, applied to the pin 3 and to the external j acket 5 .

[0031] The fog generating device 1 of the invention is designed to be operatively connected to a tube 11 for introducing the fog fluid through the inlet means 7 ( for example by screwing the tube 11 inside the inlet means 7 , as shown) .

[0032] Furthermore , the fog generating device 1 of the invention is designed to be operatively connected to a fog fluid outlet noz zle 13 via the outlet means 9 ( for example by screwing the noz zle 13 inside the outlet means 9 , as shown) .

[0033] Furthermore , in an innovative way, the device 1 of the invention could be equipped with a plurality of concentric pins , which follow the same scheme and operating principle as the pin 3 .

[0034] And furthermore , preferably the noz zle or noz zles 13 may have di f ferent shapes and dimensions to optimi ze the performance of the device 1 .

[0035] With the above configuration, the following advantages are obtained compared to the prior art :

[0036] - considering the iron alloy construction, 8g of mass of the exchanger is suf ficient for each m of fog emitted (where known devices reach 30-40 g of mass per m of fog emitted) lower weight of the metal exchanger with consequent lower weight of the fog system and smaller si ze of the same smaller external surface of the exchanger with consequent lower heat dispersion and related consumption for the same cubic meters of fog delivered .

[0037] In summary, the innovative use of the exchanger 1 of the present invention can be summari zed in the following steps :

[0038] - bringing the exchanger 1 to a temperature suitable for optimal operation ( this temperature cannot be speci fied in absolute value since it depends on many external factors , such as the quality of the thermal insulation, the composition of the fog fluid used, the quantity of fog that wants to generate , etc . ) introducing the fog fluid into the inlet pipe 11 at a pressure suf ficient to guarantee the desired flow : in this way, the fog will begin to come out of the noz zle 13

[0039] - stopping the introduction of fog fluid when the quality of the fog generated no longer meets the necessary requirements ( due to the lowering of the average temperature of the exchanger 1) .

[0040] As far as heating is concerned, both the pin and the covering are heated, for example by means of an electric resistance (slot 14 for this resistance) . The exchanger 1 is generally made of metal (for example, iron, steel, aluminium, etc.) or ceramic material.

[0041] Finally, as regards the advantages of the stepped solution, normally the flow passes through the holes in "series" as the "parallel" holes are not crossed by the flow in a homogeneous way. This difference increases during delivery, creating areas of the exchanger that are too cold and others with energy that remains unused. By creating a "series" path, it is instead necessary to also increase the size of the passages in order not to have an excessive loss of load. Compared to the straight exchanger, i.e. made up of a cylindrical pin and relative jacket, the stepped solution allows the distance between these two elements to be significantly increased, drastically reducing the risk of clogging and loss of pressure and therefore contributing to the generation of a high volume of fog (for the same mass of the exchanger) without deterioration in quality over time. Some preferred embodiments of the invention have been described, but naturally they are susceptible to further modi fications and variations within the same inventive idea al so in the material in which it is implemented . In particular, numerous variations and modi fications , functionally equivalent to the previous ones , which fall within the scope of the invention as highlighted in the attached claims , will be immediately evident to those skilled in the art .

Claims

CLAIMS1. Compact fog generating device (1) of an exchanger type, comprising at least one pin (3) contained inside and operatively connected to at least one external jacket (5) , said fog generating device (1) also being equipped with inlet means (7) and outlet means (9) of a fog fluid, characterized in that:- said pin (3) has its external surface of a substantially stepped shape, wherein said surface between the steps is flat or machined or wavy, with a larger diameter in correspondence with said inlet means (7) and smaller diameter in correspondence with said outlet means (9) ; and said external jacket (5) has its internal surface, facing the external surface of said pin (3) , of a substantially stepped shape, with a larger diameter and smaller thickness in correspondence with said inlet means (7) and smaller diameter and greater thickness in correspondence with said outlet means (9) .

2. Compact fog generating device (1) of an exchanger type, comprising at least one pin (3) contained inside and operatively connected to at least one external jacket (5) , said fog generatingdevice (1) being also equipped with inlet means (7) and outlet means (9) of a fog fluid, characterized in that:- said pin (3) has its external surface of a substantially stepped shape, wherein said surface between the steps is flat or machined or wavy, with a smaller diameter in correspondence with said inlet means (7) and larger diameter in correspondence with said outlet means (9) ; and said external jacket (5) has its internal surface, facing the external surface of said pin (3) , of a substantially stepped shape, with a smaller diameter and greater thickness in correspondence with said inlet means (7) and larger diameter and smaller thickness in correspondence with said outlet means (9) .

3. Compact fog generating device (1) according to claim 1 or 2, characterized in that said pin (3) and said external jacket (5) are both cylindrical in shape, or both parallelepiped or both with another geometric shape that slides mutually in a telescopic way.

4. Fog generating device according to claim 1, 2 or 3, characterized in that said device (1) is assembled by screwing said pin (3) and saidexternal jacket (5) .

5. Compact fog generating device (1) according to claim 1, 2 or 3, characterized in that said device (1) is assembled by means of welding or sealing gaskets or putty, applied to said pin (3) and to said external jacket (5) .

6. Compact fog generating device (1) according to any of the previous claims, characterized in that it is also equipped with a central housing (14) for the insertion of a cartridge heating resistor.

7. Compact fog generating device (1) according to any of claims 1 to 5, characterized in that it is designed to be heated from the outside, with a flat mica resistor or with a spiral armoured resistor.

8. Compact fog generating device (1) according to any of the previous claims, characterized in that it is designed to be operatively connected to a tube (11) via said inlet means (7) .

9. Compact fog generating device (1) according to any of the previous claims, characterized in that it is designed to be operatively connected to a nozzle (13) via said outlet means (9) .

10. Compact fog generating device (1) according to any of the previous claims, characterized in that it is equipped with a plurality of concentric pins,which follow the same scheme and operating principle as said pin (3) .

11. Compact fog generating device (1) according to any of the previous claims 6 or 9, characterized in that said nozzle (13) has different shapes and dimensions to optimize the performance of the device ( 1 ) .

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