METHOD AND MEANS FOR DRYING

Abstract: A method of drying a surface of an object comprises controlling the relative humidity of a pressurized drying medium to be essentially lower than that of the natural air layer immediately adjacent the surface to be dried, blowing the drying medium onto the surface at a velocity of between 5 and 80 m/sec, and controlling the temperature of the drying medium, as it exits from the blowing means, to be in the range from 5-150 DEG C, preferably in the order of about 70 to 95 DEG C.

Description: TO ALL WHOM IT MAY CONCERN: Be it known that I, Rolf Viktor Cederstrόm, a subject of the King of Sweden, and resident of the city of Stockholm, Sweden, have invented certain new and useful improvements in "METHOD AND MEANS FOR DRYING" and I do hereby declare that the following is a full, clear and exact description of the same, reference being had to the accompanying sheet of drawings and to the numerals of reference marked thereon, which form a part of this specification. BACKGROUND OF THE INVENTION Field of the Invention: This invention relates to method and means for drying, and more precisely a method and means of the class which operates with combustion of gas and which are adapted for removal of moisture from the surface of objects. Prior art: Previously known drying apparatuses which operate with com¬ bustion of gas may, simply stated, be said to constitute gas burners for heating of the surface, which should be dried, to such a temperature that water or moisture on the surface is removed essentially by vaporization .and evaporation due to the rise of the surface temperature. However, a comparatively large amount of heat.energy is required to heat the surface to such an extent that evaporation takes place. Further, by the combustion of gas, such as bottled gas, there are also generated large quatities of water vapor, viz. of the order of about 2 cubic meters of water vapor per kilogram of gas. In one way or another also that water vapor must be removed to reach an effective drying. Therefore, the efficiency of the known drying apparatuses is normally very low. SUMMARY OF THE INVENTION A method of drying a surface of an object according to the present invention comprises controlling the relative humidity of a gaseous pressurized drying medium to be essentially lower than that of the natural air layer immediately adjacent to the surface to be dried, blowing said pressurized drying medium onto the surface to be dried at a velocity of between 5 and 80 m/sec, preferably SUBSTITUTE SHEET a velocity of between 25 and 60 m/sec, as said drying medium exits from a blowing means, and controlling the temperature of said pressurized drying medium, as it exits from said blowing means, to be in the range of 5 to 150°C, preferably about 70 to 95°C. Where the pressurized drying medium is compressed air the controlling of the relative humidity of the pressurized drying medium according to the invention is effected by com¬ pressing ordinary ambient air and removing liquified water therefrom down to a relative humidity of the compressed air of about 1 to 10 percent, preferably down to a range of about 2 to 5 percent. In accordance with the invention it has been found very feasible to compress the compressed air to a pressure of between 3 and 12 bars, preferably about 6 - 7 bars. To avoid recirculation of air having a high relative humidity it is preferred according to the invention to take the compressed air, or the air to be compressed, from a space different from and physically separated from the space where drying is to take place. Various drying apparatuses may be used for carrying the above recited drying method into effect in practise. However, according to one aspect of the present invention, a drying apparatus has been found particularly suitable which comprises, in combination, means for controlling the relative humidity of a gaseous pressurized drying medium to be essentially lower than that of the natural air layer immediately adjacent to the surface to be dried, means for flowing said pressurized drying medium onto the surface to be dried, means for controlling the velocity of the drying medium as it exits from the blowing means to be in the range of between 5 and 80 m/sec, preferably a velocity between 25 and 60 m/sec, and means for controlling the temperature of said pressurized drying medium, as it exits from said blowing means, to be in the range of 5 to 150°C, preferably about 70 to 95°C. Particularly advantageous results have been achieved. means for controlling the temperature of said pressurized drying medium comprises a gas burner head, disposed to permit the flame thereof surround the end portion of the drying medium tube to heat said end portion and the pressurized drying medium therein immediately before its exit from said end portion. Advantageously, the gas burner head is of the cyclone type or whirler type. For a fuller understanding of the invention, reference may be had to the following description of preferred embodiments illustrated on the accompanying drawing. ON THE DRAWING FIG. 1 shows a side view of one embodiment of a drying apparatus according to the invention; FIG. 2 shows an axial longitudinal cross section through the foremost end of the drying apparatus in FIG. 1; FIG. 3 shows a cross sectional view as seen in the plane III-III in FIG. 2; FIG. 4 illustrates a detail of the drying apparatus as shown in FIG. 1. AS SHOWN ON THE DRAWING The drying apparatus in FIG. 1 comprises a gas tube, generally denoted 10, and a drying medium tube, generally denoted 11. The two tubes 10 and 11 are held clamped together in a parallel relationship by means of two clamps 12, 12, and a further, middle clamp 13, to which middle clamp 13 there is secured a transverse handle 14. This middle clamp 13 is longi¬ tudinally movable along the two tubes 11, 11. At its rear end the gas tube 10 has valve means, generally denoted 15, for control of the gas flow, and at its foremost end the gas tube 10 is provided with a burner head 16 which in the instant case is of the cyclone- or whirlertype. At the rear end of the drying medium tube 11 there is provided a valve means, generally denoted 17, for control of the flow of drying medium, usually compressed air. The rear end of the drying medium tube 17 is bent downwardly from the gas tube 10 to ensure accessability to the gas valve means 15 and the hand grip H provided for holding the apparatus. Further, this bending downwardly of the rear end of the drying SUBSTITUTE SHEET medium tube 11 ensures that a hose (not shown) for admission of compressed air to be used as drying medium, will be held in a suitable angle with respect to the apparatus. As shown particularly in FIG. 1 and 2 the drying medium tube 11 has its foremost end (the left hand end as shown in FIGS. 1 and 2) bent in such a manner that the tube in question has a considerable portion 18 disposed within the flame (not shown) that emerges from the gas burner head 16, as will be discussed in more details below. Between the handle H with its valve means 15 there is disposed a gas nozzle 19, FIGS. 1 and 4, having an orifice of a suitable size, such as a diameter of about 1.0 mm. The mouth of the gas orifice is disposed centrally of the nozzle 19, and the nozzle is adapted to eject the gas into the rear end of the gas tube 10. Around the nozzle 19 there are disposed a plurality of openings 20 through the wall of the gas tube 10. These openings are of such a size and are arranged in such a manner, that the gas emitting through the nozzle 19 draws in ambient air through the openings 19 to be thoroughly mixed with the gas before the gas/air mixture reaches the burner head 16. The valve means 15. comprises one controllable valve 15A for control of the magnitude of a pilot flame which is always present within the burner head 16 when the apparatus is in use. Further, the valve means 15 comprises a controllable main valve 15B for control of the magnitude of a main flame within the burner head when the apparatus is effectively in operation. The "on/off" status of the apparatus is controlled by means of a spring biased lever L which controls an "on/off" gas valve which may form a portion of the valve 15B. The lever L may be locked in the "on"-position by means of a spring biased latch 21 which engages with the lever L in its "on"-position and locks the lever in that position until the lever L is actuated once again, at which moment the latch 21 automatically returns to its unlocking position. As shown in FIGS. 1, 2 and 3 the cyclone-burner 16 com¬ prises an open ended cylindrical outer jacket 22 which is affixed to the foremost end of the gas tube 11. Near its inlet end, e.g. the right hand end in FIGS. 1 and 2, the SUBSTITUTE SHEET 23 has a plurality of throughgoing bores 24, in the instant case five such bores 24, which are disposed with a slight inclination with respect to the longtidinal central axis of the jacket 22. In operation this bores 24 bring about a very intensive rotary or whirling motion of the gas/air mixture as it passes through the cyclone burner 16 and as it exits there¬ from in the shape of a whirling flame. In fact, this whirling flame surrounds the foremost end of the drying medium tube 18 completely, and strikes the surface of such foremost tube end in such a manner that it will be heated very effectively. It should be mentioned that the drying medium tube has, at the foremost end thereof, a nozzle 29 having an orifice of a diameter of about 3.0 mm, in the instant case. The foremost end of the complete apparatus, i.e. the left hand end as shown in FIGS. 1 and 2, is provided with a protective outer shell 25, preferably made from stainless steel sheet. The shell 25 has a plurality of holes 26 to reduce the weight thereof, and also to permit dissipation of heat. At its rearmost end the shell 25 is provided with two laterally projecting brackets 27,28 to support the apparatus when placed on a base, such as a floor. Just to complete the picture, there is shown very schem¬ atically in FIG. 1, a compressor 30 to feed the drying medium tube 11 with compressed air, to be used as a drying medium in the instant case, viz. through a line 31. Likewise very schematically is shown a gas bottle 32 from which bottled gas is fed to the apparatus through a line 33. SUBSTSTUTE SHEET

Claims: I CLAIM AS MY INVENTION: 1. A method of drying a surface of an object comprising: controlling the relative humidity of a gaseous pressuriz¬ ed drying medium to be essentially lower than that of the natural air layer immediately adjacent to the surface to be dried, blowing said pressurized drying medium onto the surface to be dried at a velocity of between 5 and 80 m/sec, preferably a velocity between 25 and 60 m/sec, as said drying medium exits from a blowing means, and controlling the temperature of said pressurized drying medium, as it exits from said blowing means, to be in the range of 5 to 150°C, preferably about 70 to 95°C. 2. A method as claimed in claim 1 and wherein the pres¬ surized drying medium is compressed air, wherein the controlling of the relative humidity of the pressurized drying medium is effected by compressing ordinary ambient air and removing liquified water therefrom down to a relative humidity of the compressed air of about 1 to 10 percent, preferably down to a range of about 2 to 5 percent. 3. A method as claimed in claim 2, wherein the the air is compressed to a pressure of between 3 and 12 bars, preferably a range of about 6 - 7 bars. 4. A method as claimed in claim 2, wherein the ambient air to be compressed is taken from a space different from and physically separated from the space where drying is to take place. 5. A drying apparatus to be used for drying a surface of an object comprising, in combination, means for controlling the relative humidity of a gaseous pressurized drying medium to be essentially lower than that of the natur air layer immediately adjacent to the surface to be dried, means for blowing said pressurized drying medium onto the surface to be dried, means for controlling the velocity of the drying medium as it exits from the blowing means to be in the range of between 5 and 80 m/sec, preferably a velocity between 25 and 60 m/sec, and ' SUBSTSTUTE SHEET drying medium, as it exits from said blowing means, to be in the range of 5 to 150°C, preferably about 70 to 95°C. 6. An apparatus as claimed in claim 5, wherein said means for controlling the temperature of said pressurized drying medium comprises a gas burner head, disposed to permit the flame thereof surround the end portion of the drying medium tube to heat said end portion and the pressurized drying medium therein immediately before its exit from said end portion. 7. An apparatus as claimed in claim 6, wherein said gas burner head is of the cyclone or whirler type. SUBSTITUTE SHEET

Inventors: CEDERSTROEM ROLF V, CEDERSTROEM, ROLF, V.
Applicants: CEDERSTROEM ROLF V, CEDERSTROEM, ROLF, V.
Application year: 1989
Main classification: F26B3
IPC codes: F26B21