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(11) | EP 0 030 927 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Blowing nozzle |
| (57) A blowing nozzle for connection to a blowing tool to deliver a pressurized, gaseous
fluid. The nozzle comprises a plurality of fluid passages (14) which end in the form
of blowing openings (16) in a shell surface (7a) which becomes narrower at the front
on the nozzle. The area of the blowing openings (16) exceeds by at least 10 percent,
preferably at least 15 percent, the cross-sectional area of the passages (14) close
to the blowing openings (16). |
TECHNICAL FIELD
[0001] The present invention relates to a blowing nozzle for a blowing tool, which nozzle has at least two, preferably more outflow passages, each with a first end adapted to be supplied from the blowing tool with a pressurized gaseous fluid and with a second end comprising a blowing opening adapted to deliver said fluid in the form of a stream of fluid to an atmosphere surrounding the nozzle, at least two of the outflow passages being so orientated that streams of fluid delivered by the corresponding blowing openings can be directed towards an object which is to be treated with said fluid. Fluid streams refers both to continuous and to pulsating streams.
[0002] Such nozzles can be applied to a large number of different types of blowing tool. An example of the use of such a blowing tool is the blowing clean of an object, for example a workpiece, with air or another gas, for example during turning and milling. Other examples are cooling, heating and drying and acting on the movement of various parts, for example in automatic machines.
BACKGROUND ART
[0003] Previously known blowing nozzles and blowing tools have generated so much noise in operation that noise levels which are harmful to hearing or in any case are very disturbing, are reached. Attempts have hitherto been made to reduce the noise level by various changes in the dimensions of the nozzle or of various parts of the blowing tool, or by forming the nozzle as a multi-hole nozzle, that is to say with a plurality of blowing openings.
DISCLOSURE OF INVENTION
[0004] The object of the invention is to provide a multi-hole blowing nozzle, that is a nozzle with at least two, preferably more blowing openings, which has a considerably reduced noise level in comparison with known nozzles. This object is achieved by means of the invention in that the area of said blowing openings exceeds by at least 10 percent, preferably at least 15 percent, the minimum cross-sectional area of the passages just before the blowing openings.
BRIEF DESCRIPTION OF DRAWINGS
[0005] The invention is described in more detail with reference to the accompanying drawing which shows a preferred form of embodiment of a nozzle according to the invention. In the drawing, Figure 1 shows a longitudinal-section of the nozzle, where a small portion is also shown in side view, and Figure 2 shows a view from the front of the nozzle.
BEST MODE OF CARRYING OUT THE INVENTION
[0006] In the drawing, 1 designates a nozzle in general with a nozzle body 2, preferably of metal, adapted to be secured by means of a suitable connection, to a blowing tool 3 indicated by broken lines. The blowing tool 3 does not constitute a part of the present invention so that it is not described in detail here.
[0007] The nozzle body 2 comprises a back portion 4, which becomes narrower in a taper forwards, and the external shell surface 4a of which, which is preferably axially symmetrical, forms the angle a with the central axis 5 of the nozzle 1. The back portion 4 merges at 6 into an intermediate portion 7 which becomes narrower in a taper forwards and the external shell surface 7a of which, which is preferably axially symmetrical, forms the angle S with the central axis 5 of the nozzle body 1.
[0008] The angle a is preferably less than 15°. It can even be 0° in which case the shell surface 4a is thus parallel with the central axis 5.
[0009] In the example shown, the angle β is about 20° but can have other values as described in more detail below. The angle can be greater than, equal to or smaller that the angle a.
[0011] A cylindrical bore hole 9 is formed in the body 2 and merges at the front into a bore hole 10 which becomes narrower in a taper. The wall of the bore hole 10 is preferably parallel to the shell surface 7a.
[0012] The bore hole 10 merges at the front into a cylindrical bore hole 11 which ends with a tapered bore hole 12. The bore holes 9 and 10 together form a chamber 13 which is adapted to be supplied from the blowing tool 3 with a pressurized gaseous fluid, the pressure of which is more than 4 bars, preferably about 4 - 8 bars. The bore holes 11 and 12 constitute a seat for a supporting body, not shown, for a valve, not shown, which is included in the blowing tool and which is adapted to regulate the streams of fluid through the blowing tool. In the forms of embodiment of the invention where such a supporting body does not occur, the bore holes 11 and 12 are absent. Otherwise, in the last-mentioned case, these bore holes would lead to an increased noise level.
[0013] A number of fluid passages in the form of ducts 14, which have a circular cross-section with the diameter D, and with a cross-sectional area which is less than 3 mm2, connect the chamber 13 to the atmosphere surrounding the nozzle. The ducts 14 extend substantially parallel to the central axis 5 of the nozzle.
[0014] The entrance to the ducts 14 consists of inlets 15 in the wall of the bore hole 10, while the outlet of the ducts 14 consists of blowing openings 16 in the external shell surface 7a of the intermediate portion 7. As a result of the fact that the openings 15 and 16 form the angle S with the longitudinal direction of the ducts 14, the openings are ellipsoidal, the major axis of the ellipse being D/sins. As a result, the openings 15 and 16 have a larger area than the cross-sectional area of the ducts. By experimental tests it has now been shown that the relationship between the area at least of the openings 16 and the cross-sectional area of the ducts 14 has a decisive effect on the noise level of the nozzle. A corresponding effect, although to a somewhat lesser extent, applies with regard to the area of the openings 15 in relation to the cross-sectional area of the ducts 14.
[0015] It has been found that a drastic reduction in the noise level is achieved if the angle s is reduced from 60° to just under 60°. Even with a reduction below 650, however, a certain reduction is noise is achieved. The value of 60° or 650 for the angle 0 gives an area of the outlet openings 16 which exceeds the cross-sectional area of the ducts 14 by 15 or 10 percent respectively. In the form of embodiment shown in the drawing, β is approximately 20°, as a result of which the area of each outlet 16 exceeds the cross-sectional area of the ducts 14 by about 200 percent.
[0016] The same percentage increase in the area of the outlets 16 in relation to the cross-sectional area of the ducts 14 can be obtained if the ducts 14 are inclined in relation to the central axis 5, so that they extend inwards or outwards in their fluid direction. If the ducts 14 diverge outwards, for example, in relation to the central axis 5, by an angle γ°, an increase in area of 15 or 10 percent is obtained if the angle β between the shell surface 7a and the central axis amounts to 60-γ° or 65-γ°.
[0017] The angle γ should not exceed 20°, however, Preferably 8 should be less than 150, or better still less than 10°.
[0018] In order that the said fluid, that is to say the streams of fluid which leave the blowing openings 16, may be able to reach the object which is to be treated with the fluid to a sufficiently high extent, it is preferable that the ducts 14 or in any case the part thereof situated closest to the respective blowing opening, should extend substantially parallel to one another or that they should converge on a point in front of the nozzle, where the object is. If the object which is to be treated with the fluid does not have too small an extent, the ducts 14 may naturally be allowed to diverge outwards somewhat. In all the said embodiments, however, the aim should be that the streams of fluid reach the object in an assembled group.
[0019] Between the openings 16 there are disposed wing-shaped radial flanges 17 which extend with increasing height from the back end of the body portion 4 to just in front of the openings 16 where the edge of the flanges is rounded at 18. If the angle a is nil, however, the flanges 17 nevertheless have a constant height along the shell surface 4a. In front of the openings 16, the flanges have a height H, which should be greater than the diameter D of the ducts 14, preferably greater than D/sinβ. Through the presence of the flanges 17, the openings 16 are protected from damage which might otherwise occur as a result of the orientation and shaping of the blowing openings 16 arranged according to the invention. Such damage can lead to an increased noise level. The presence of the flanges therefore ensures that the low noise level achieved according to the invention is retained. Another advantage of the flanges 17 is that they serve as a skin protection during the handling of the blowing tool.
[0020] The flanges 17 may approriately be made of metallic material but they can also be of plastics, rubber or like material.
[0021] Although the drawing shows a nozzle with eight blowing openings 16, it is obvious that fewer or more blowing openings may be provided. In addition to the ring of openings 16 shown, one or more central, conventional, blowing openings can be provided in the nose portion 8 of the nozzle. The presence of such a central blowing opening, which does not have any or at any rate any appreceiable increase in area, naturally has a certain effect of increasing the noise level. In certain cases, however, one or more such central holes can be warranted, particularly if it is desired to achieve a greater concentration of fluid round the central axis of the nozzle.
[0022] It is further obvious that the nose portion 8 can be flat instead of being rounded. In this case, the blowing openings 16 can be disposed either in the flat nose of the nozzle or in the edge thereof, so that they open out partially in the shell surface 7a of the nozzle and partially in the periphery of the flat nose. Even with a nozzle with a flat nose, however, the blowing openings 16 can be situated entirely in the shell surface 7a.
[0023] Nor is the invention limited to like straight ducts 14. Instead, these can consist, for example, of a plurality of different duct portions, which form angles with one another, where the portion situated closest to the blowing openings 16 preferably extends substantially parallel to the central axis 5 of the nozzle, or of helical fluid passages. The ducts can also have a varying cross-section along their length. In the last-mentioned case, it is the cross-sectional area of the ducts 14 just before the outlets 16, seen in the direction of the fluid, which should be related to the area of the outlets 16. Similarly it is the cross-sectional area of the ducts 14 just after the inlets 15, seen in the direction of the fluid, which should be related to the area of the inlets 15.
1. A blowing nozzle (1) for a blowing tool (3), which nozzle has at least two, preferably
more outflow passages (14), each with a first end (15) adapted to be supplied from
the blowing tool with a pressurized, gaseous fluid and with a second end comprising
a blowing opening (16) adapted to deliver said fluid in the form of a fluid stream
to an atmosphere surrounding the nozzle, at least two of the outflow passages being
so orientated that fluid streams delivered by the corresponding blowing openings can
be directed towards an object which is to be treated with said fluid, characterised
in that the area of said blowing openings (16) exceeds by at least 10 percent, preferably
at least 15 percent, the minimum cross-sectional area of the passages (14) just before
the blowing openings.
2. A blowing nozzle as claimed in Claim 1, characterised in that the blowing openings
(16) are situated in a shell surface (7a) on the nozzle (1) which forms an acute angle
(β) with the central axis (5) of the nozzle.
3. A nozzle as claimed in one of the preceding Claims, characterised in that each
of said passages (14) has a minimum cross-sectional dimension which is less than 2
mm.
4. A nozzle as claimed in one of the Claims 2 - 3, characterised in that said shell
surface (7) becomes narrower towards the front.
5. A nozzle as claimed in one of the preceding Claims, characterised in that said
passages (14) are elongated and that at least at their said second end (16) they extend
substantially parallel to the central axis (5) of the nozzle.
6. A nozzle as claimed in one of the Claims 1 - 4, characterised in that said passages
(14) are elongated and that they form an anglewith the central axis (5) of the nozzle,
which is less than 20°, preferably less than 15 .
7. A nozzle as claimed in one of the preceding Claims, characterised in that the passages
have a constant and mutually like cross-sectional area along their whole length.
8. A nozzle as claimed in one of the preceding Claims, characterised in that said
first end (15) of the passages (14) forms an inlet, the area of which exceeds by at
least 10 percent, preferably at least 15 percent, the minimum cross-sectional area
of the corresponding passage (14) just after the inlet.
9. A nozzle as claimed in one of the Claims 2 - 8, characterised in that one or more
protections (17) for the blowing openings are provided on the shell surface (7a) in
the form of members projecting from this.
10. A nozzle as claimed in Claim 9, characterised in that each of said protections
(17) consists of an elongated, wing-shaped member, of which the extent (H) in height,
that is to say at right angles to the shell surface (7a), is preferably greater than
the diameter (D) of the adjacent blowing openings (16) at least in a region beside
this.