SE546500C2 - Blowing devices with angled exhaust passages - Google Patents

Abstract

Blowing device (1) comprising an enclosure (3) having a pressurized gaseous fluid inlet (17), said enclosure having an outlet surface (9) comprising a plurality of primary and secondary exhaust passages (19, 21) wherein the secondary exhaust passages are angled away from the primary exhaust passages an angle β.

Description

Fieid of the iriventiori The present invention reiates to hiovving devices, such as air knives and air manitoids Background iritormation For many years hiowing devices, otten caiied air knives, air rnaniioids and air (nozzie) rnanitoids, have been used in many industries and rnanutacttiring processes to deiiver pressurized air against the surface ot stationary or moving objects to hiovy oft, i_e,, remove, iiduid or dehris from, or to cooi or to heat the surface ot those ohiects.

A typicai air itnife consists oi a rnanitoid or pienum vvitii an eiongated riarroyir air siot, either continuous or segrnented so as to more a piuraiity ot smaii openings, trom vvhicit pressurized air can exit aiong the iength oi the air siot, The siot is iritended to provide a continuous air fiow or jet aiong the iength oi the siot. Air itnives are gerieraiiy piaced in ciose proxirraity to the part being hiovvri ott and any interruption in the continuous air tio-vv rnay he cietrimeritai to the hiovv oti eitect An air nozzie or air manitoid consists ot a manitoid or pienurn from vvhich muitipie air outiet riozzies, with round or eiongated openings, are piaced at various interyais aiong the iength ot the manifoid. The air nozziejmanitoid does not provide a continuous air tiow aiong its iength as does an air itniie. instead the orifice of each outiet nozzie usuaiiy deiivers a much iarger air tiow in a concentrated area in the torrn ot a high veiocity air stream irorn each outiet nozzie. A prohiern may occur where two adjacent air streams impact a surface at the same spot hut trorn ditterent angies as the restiiting combined airtiow :nav torm a "hiind spot" vtrhicit iacits the desired cieaning effect and iaiis to rernove iiquid or dehris.

Properties that are important tor a compressed air hiovving device are noise ievei, constimption, power and hiovving pattern. These tour parameters are dependent on the pressure in the hiovvirtg device and are usuaiiy speciiied at different pressures. in many air appiications today, a rectanguiar cross~sectionai area ot the jet is required where the vridth of the air stream shouid he inaxintized, and the height rninirnized. Preterahiy the noise ievei and air constimption shouid aiso he rninirnized. Qne vray of achieving this is use severai smaiier outiet nozzies instead of using one iarge outiet nozzie. The size and centre-to-centre spacing of the outiet nozzies are careitiiiy caicuiated to rninintize the sound ievei at a given pressure. The outiet nozzies can he piaced in different patterns to ohtain a specific hioy-ring pattern. The cross-sectionai areas of the outiet opening-s in the nozzies and the distance between thern together deterrnine the cross- sectionai area ot the nozzie.

To determine the hiowiiwg pattern, the reiative pressure that occurs on a fiat surface front a ntanifoid vrhich is facing the surface at. 90" can be measured.

Vtfitit a given design of the pattern of the outlet channeis, if št is desired to increase the reiative pressure across the width of the biowing pattern then this can oniy be achieved by adiusting the input pressure.

The disadvantage of increasing the pressure is that it tends to result in a disproportionately high pressure increase in the centre of the airjet, which is rarely required for this type of nozzle, instead of a proportionate increase across the whole width of the blowing pattern. This means that, in practice, you use an unnecessary amount of energy to get an increase in the relative pressure over the whole surface covered by the air stream. Therefore, there exists a need for air blowing arrangements which can provide more equal coverage on a surface for a given pressure and a given cross-sectional area of the nozzles of the arrangement.

Summary of the invention lt is an object of the invention to overcome or at least minimize the problem mentioned above by means of a blowing device having the features of claim 1. Such a blowing device is characterised by having a group of at least two adjacent central exhaust passages which direct a pressurised gaseous fluid at a first angle from the blowing device wherein said group of central exhaust passages are surrounded on each side by at least one exhaust passage orientated at an angle away from the closest central exhaust passage. Owing to the presence of the at least two adjacent central exhaust passages directed in the same direction and the presence of further exhaust passages directed away from this direction, the resulting jet of co-mingled gas formed from the pressurized gas leaving these exhaust passages surprisingly exhibits a smaller central peak pressure than blowing devices with a single central exhaust passage directed in a first direction and arranged between further exhaust passages orientated at an angle away from the central exhaust passage.

Description of the figures Figures 1a) to lc) show schematically lateral, plan and end-on views of a first embodiment of a blowing device in accordance with the present invention.

Figures 2a) to Zc) show schematically side, plan and end-on views of a first embodiment of a blowing device in accordance with the present invention.

Figure 3 shows an example of the relative pressures measured at positions across a surface using different angles for exhaust passages.

Detailed description of the invention Figures 1a)-1c) shows schematically and not to scale lateral, plan and end views of a blowing device 1 according to a first embodiment of the invention. Blowing device 1 comprises an enclosure 3 with an exterior wall 5 which encloses a chamber 7. The enclosure is in the form of a box, which in this example is shown as being substantially rectangular but which could be of any other suitable shape, and the box has an outlet surface 9 which is intended to face towards the item which it blows air onto as shown by the arrow 11. Preferably outlet surface 9 is flat and elongated with a major centre line 13 extending in a first direction X and a minor centre|ine 15 extending perpendicular to the major centre line in the direction Y. The external wall 5 has a pressurized gas supply inlet 17 which is adapted be connected to a supply of pressurised gas (not shown). The outlet surface 9 is provided with a plurality of primary exhaust passages 19 and a plurality of secondary exhaust passages 21each of which extend from the chamber 7 through the exterior wall 5 and open out on the outlet surface 9. The primary and secondary exhaust passages are shown arranged in a straight line along the major centre|ine of the outlet surface to order to give this embodiment of the invention symmetry, but they may be arranged in any other fashion such as parallel to the major centre|ine or at an angle to the centre|ine. A plurality of primary exhaust passages form a group of primary exhaust passages 23 comprising at least two adjacent primary exhaust passages 19 which are arranged to direct pressurised gaseous fluid at a first angle ot from the outlet surface. Preferably this angle is perpendicular to the outlet surface. lf the blowing device is intended to provide a jet of air which is substantially symmetrical along the major centre|ine then the centre of the group of primary exhaust passages can coincide with the midway point of the major centre|ine as shown in the figures. lf the blowing device is intended to produce a stream of air which is not symmetrical then the centre of the primary exhaust passages can be placed to one side of the midway point of the major centre|ine. The group of primary exhaust passages form a line, preferably a straight line, and which is followed on each end in the direction of the major centre|ine by at least one secondary exhaust passage 21 which is directed at an angle ß away from angle ot in the direction along the major centre|ine. As shown in figure 1a), the central group 23 of two primary exhaust passages 19 has three secondary exhaust passages 21 arranged to the left of it which direct pressurized gas at the angle ß to the left, and three secondary exhaust passages 21 arranged to the right of it which direct pressurized gas at the angle ß to the right. ln this embodiment of the invention there are two primary exhaust passages in the group of primary exhaust passages and there are a total of six secondary exhaust passages arranged in groups of three secondary exhaust passages on either side the group of primary exhaust passage, but there could be more than two primary exhaust passages in the group of primary exhaust passages, and the number of secondary exhaust passages on each side of the group for primary exhaust passages could be any number equal to or greater than 1. The centre-to- centre distances between adjacent exhaust passages may be equal or different and the cross- sectional areas of the exhaust passages may be the same for every exhaust passage or they may be different.

Figures 2a)-2c) show schematically and not to scale a lateral, plan and end view of a blowing device 1 according to a second embodiment of the invention where the same reference numbers used in figures 1a)-1c) are used for similar elements in these figures. Thus, blowing device 1 comprises an enclosure 3 with an exterior wall 5 which encloses a chamber 7. The enclosure is in the form of a box, which in this example is shown as being substantially rectangular but which could be of any other suitable shape, and the box has an outlet surface 9 which is intended to face towards the item which it blows air onto as shown by the arrow 11. Preferably outlet surface 9 is flat and elongated with a major centre line 13 extending in a first direction X and a minor centre|ine 15 extending perpendicular to the major centre line in the direction Y. The external wall 5 has a pressurized gas supply inlet 17 which is adapted be connected to a supply of pressurised gas (not shown). The outlet surface 9 is provided with a plurality of primary exhaust passages 19 and a plurality of secondary exhaust passages 21, each of which extend from the chamber 7 through the exterior wall 5 and open out on the outlet surface 9. The primary and secondary exhaust passages are shown arranged in a straight line along the major centreline of the outlet surface to order to give this embodiment of the invention symmetry, but they may be arranged in any other fashion such as parallel to said major centreline or at an angle to the centreline. A plurality of primary exhaust passages forms a group of primary exhaust passages 23 comprising at least two adjacent primary exhaust passages 19 which are arranged to direct pressurised gaseous fluid at a first angle ot from the outlet surface. Preferably this angle is perpendicular to the outlet surface. lf the blowing device is intended to provide a jet of air which is substantially symmetrical along the major centreline then the centre of the group of primary exhaust passages can coincide with the midway point of the major centreline as shown in the figures. lf the blowing device is intended to produce a stream of air which is not symmetrical then the centre of the primary exhaust passages can be placed to one side of the midway point of the major centreline. The group of primary exhaust passages forms a preferably straight line which is followed on each end in the direction of the major centreline by at least one secondary exhaust passage 21 which is directed at an angle ß away from angle ot in the direction along the major centreline. As shown in figure 2b), the central group 23 comprises two primary exhaust passages 19 and immediately outside this group of primary exhaust passages, on each side thereof, a pair 25 of secondary exhaust has been positioned, said secondary exhaust passages being arranged parallel to the minor centreline 15. Further outside each group of two secondary exhaust passages a single secondary exhaust passage is arranged on the major centreline. This single secondary exhaust passage is followed by a further pair of secondary exhaust passages parallel with the minor centreline Figure 3 shows experimental results from a blowing device which comprised a row of exhaust passages arranged in a straight line. The blowing device comprised two central primary exhaust passages which pointed straight towards a flat pressure measuring surface. A plurality of secondary exhaust passages of the same cross-sectional area was positioned on either side of the pair of primary exhaust passages. The inlet pressure was 0.5 MPa, the distance to the pressure measuring surface was 200 mm, the face of the surface was 290 mm x 310 mm. The face of the blowing device that faced the pressure measuring surface was 43 mm x 7 mm. lt had two central primary exhaust passages and 14 secondary exhaust passages (seven to either side of the central primary exhaust passages) arranged at centre to centre intervals of 2.7 mm. All exhaust passages were circular with a diameter of 0.9 mm.

A series of experiments were made using the same inlet pressure but with the secondary passages angled away at different angles from the first exhaust passages. The angles that were tested were 0°, 1.5°, 2.5°, 4°, and 6°. As can be seen in figure 3, increasing the angle of inclination of the secondary exhaust passages leads to a desirable lower but wider distinct peak which gives a good coverage of the surface without an excessively high peak pressure in the centre which only wastes energy. Surprisingly, at an angle of around 6°. The peak not only becomes wide but forms a plateau which an almost constant pressure over a wide range of positions. This is desirable as it gives a good cleaning or cooling effect over a wide area without requiring an increased inlet pressure. ln all embodiments of the present invention the secondary exhaust passages can be inclined at the same angle ß away from the nearest primary exhaust passage. Preferably angle ß is greater or equal to 1 degree and less than or equal to 10 degrees in the direction away from the closest primary exhaust passage, more preferably angle ß is greater or equal to 2 degrees and less than or equal to 9 degrees, even more preferably angle ß is greater or equal to 3 degrees and less than or equal to 8 degrees, yet more preferably angle ß is greater or equal to 4 degrees and less than or equal to 7.degrees and most preferably angle ß is greater or equal to 5 degrees unless than or equal to 7 degrees. lt is also conceivable that the angle ß changes as the distance of a secondary exhaust passage from the closest primary exhaust passage increases. For example, the second exhaust passage closest to a primary exhaust passage may be inclined at an angle ß away from the primary exhaust passage, the next secondary exhaust passage may be inclined at an angle ß + x degrees, the next secondary exhaust passage may be inclined at ß + y degrees, the following secondary exhaust passage may be inclined at an angle of ß + z degrees and so on, where z> y > x.

Preferably the maximum diameter or width of any exhaust passage is equal to or less than 1.0 mm and more preferably is less than or equal to 0.9 mm and greater than or equal to 0.5 mm. Preferably, all primary exhausts are of substantially the same cross-sectional area as each other, and/or all secondary exhausts are of substantially the same cross-sectional area as each other, or all exhaust passes have substantially the same cross-sectional area.

Preferably the minimum centre-to-centre distance between adjacent exhaust passages is equal to or greater than three times and less than or equal to five times the maximum diameter or width of opening of the largest exhaust passage,