NOZZLE FOR GAS-OPERATED SPRAYING APPARATUS

Abstract: A nozzle (10) for a gas-operated spraying apparatus, the nozzle (10) being tapered at an outlet end and having a passage therethrough wherethrough, in use, a medium to be sprayed may flow to the outlet under the control of a retractable needle (28) of circular cross-section extending substantially coaxially of the passage and of the nozzle, the outlet (24) forming a seal with the needle (28) in a rest position thereof, and in which the outlet (24) is of non-circular form, the nozzle (10) being formed of a material deformable by the needle to form the seal.

Description: NOZZLE FOR GAS-OPERATED SPRAYING APPARATUS This invention relates to nozzles for gas-operated spraying apparatus, particularly, but not exclusively, spraying apparatus disclosed in, for example, patent application No PCT/GB86/00186. In that patent application, a nozzle of novel kind is disclosed which nozzle permits, in use, extremely good control of spraying of paint for example. It has been found that even better control, preferably adjustable, can be achieved by a nozzle forming the object of the present invention. It is an object of the present invention to provide an improved nozzle for a gas-operated spraying apparatus. According to the present invention, there is provided a nozzle for a gas-operated spraying apparatus, the nozzle being tapered at an outlet end and having a passage therethrough wherethrough, in use, a medium to be sprayed may flow to the outlet under the control of a retractable needle of circular cross-section extending substantially coaxially of the passage and of the nozzle, the outlet forming a seal with the needle in a rest position thereof, and in which the outlet is of non-circular form, the nozzle being formed of a material defor able by the needle to form the seal. The tapered end of the nozzle is preferably of conical shape coaxial with the passage through the nozzle. The tapered end may have a plurality of tapered regions. Preferably, the outlet is planar and is constituted by a truncation of the tapered end in. a plane not orthogonal to the passage. The nozzle is intended to cooperate with an air cap of a spraying apparatus. In a preferred embodiment, the nozzle has cooperating means on a body thereof permitting the nozzle to be indexed, in use, relative to the air cap. The invention will be described further, by way of example, with reference to the accompanying drawing, in which:- Figure 1 is a side elevation of a nozzle according to the present invention; Figures 2 and 3 are fragmentary top and side elevations, to an enlarged scale, of the tip of the nozzle of Figure 1; and Figure 4 is a fragmentary perspective view, to a different scale, of the nozzle tip showing the cooperation of a needle therewith. Referring to the drawings, there is shown a nozzle 10 for use in a gas-operated spraying apparatus (not shown) . The nozzle is preferably moulded from a plastics material as described in the aforesaid patent application No PCT/GB86/00186. The nozzle has a body 12 and a tip 14. The tip 14 includes a first conically tapered region 16, a substantially cylindrical region 18 of zero taper, a further conically tapered region 20 and an outlet region 22 of a different conical taper. An outlet aperture 24 in the region 22 permits a medium such as paint to flow through a passage 26 (indicated in Fig. 4) axially disposed of the body 12 of the nozzle 10. A needle 28 (see Fig. 4) of circular cross-section is located, in use, axially of the nozzle body 12 and projects through the outlet aperture 24 forming a seal therewith in a rest position of the needle. The needle 28 has a lesser taper than that of the portion of the axial passage 26 defining the outlet aperture 26. The needle 28 is retractable from its rest position, in which it forms a seal, in the direction fo the arrow A to permit the medium such as paint to be ducted through the outlet aperture 26 to be sprayed. It will be seen that the further conically tapered region is a truncated right circular cone relative to an end face 30 of the cylindrical region 18 of the tip and is coaxial with an axis 32 of the passage 26 itself coaxial with the body 12 of the nozzle 10. The outlet region 22 also comprises a right circular cone (see Figs. 2, 3 and 4) coaxial with the axis 32. However, the region 22 is truncated obliquely relative to the axis 32 to form the outlet aperture 24. The aperture 24 is thus planar but elliptical in shape. If the region 24 had been truncated orthogonally of the a 32, as the needle was retracted in use, an annulus would be formed providing, theoretically, an equal flow of medium such as paint over the surface of the needle. In practice, if the needle is permitted to float within the aperture (as described in the aforesaid patent application), it tends to lie at one side of the aperture forming a crescent shaped outlet for paint. It has been found that, if the aperture 24 is non-circula e.g. elliptical as described, the paint flow can be reduced even further, for a given area of the aperture 24, so that even finer lines may be "drawn". It is not certain how the ability to draw even finer lines, than those possible with a nozzle as described in the aforesaid patent application, is achieved. It may be due to the double crescent annulus formed as the needle 28 is retracted (if the needle floats axially of the nozzle) or it may be due to a single crescent of the same area but greater width. In any case, there is a much reduced tendency to uneven spray e.g. blobs of paint, and, hence, an increased control in the drawing of extremely fine lines. Further, it has been found that there is an optimum position of the nozzle 10 relative to a surrounding air cap (not shown) for controlling the spray for drawing fine lines. * As mentioned above, the needle 28 effectively floats in the aperture 24. Gravity may cause it to take a lower than axial position. However, other forces on the needle tend to exceed those due to gravity. It is not certain what position is taken up by the needle 28 in the aperture 24 during use. Suffice it to say that, if the nozzle is rotated about its axis, relative to a surrounding air cap (not shown), an optimum position of the nozzle can be found for the finest lines. To this end, the nozzle 10 may be provided with indexing means enabling its position, in use, to be selected. The indexing means may be provided by obturations 34 (see Fig. 1) which obturations perform other functions but due to their circumferential symmetry permit,for example, five selectable angular positions of the nozzle 10 relative to an air cap. Conventionally, a nozzle is matched to its air cap. However, a nozzle according to the invention may be one of a series of nozzles having different sized outlets for use with a common air cap. This is possible because of the uniformity of moulded nozzles; the preferred method of fabricating nozzles according to the present invention. The invention is not confined to the precise details of he foregoing example and variations may be made thereto. For instance, the truncation of the outlet region 22 may not be planar but may be stepped or curved. The nozzle may have a single taper conical tip 14 or may be of a more complex shape having a plurality of tapers. The nozzle body 12 may be of any appropriate form for interfitting with an air cap and a spraying apparatus. Such spraying apparatus and air cap may be as described in the aforesaid patent application. Other variations are possible within the scope of the present invention.

Claims: CLAIMS 1. A nozzle for a gas-operated spraying apparatus, the nozzle being tapered at an outlet end and having a passage therethrough wherethrough, in use, a medium to be sprayed may flow to the outlet under the control of a retractable needle of circular cross-section extending substantially coaxially of the passage and of the nozzle, the outlet forming a seal with the needle in a rest position thereof, and in which the outlet is of non-circular form, the nozzle being formed of a material deformable by the needle to form the seal. 2. A nozzle as claimed in claim 1 wherein the tapered end of the nozzle is of conical shape coaxial with the passage through the nozzle. 3. A nozzle as claimed in claim 1 or 2 in which the tapered end has a plurality of tapered regions. 4. A nozzle as claimed in claim 1, 2 or 3 wherein the outlet is planar and is constituted by a truncation of the tapered end in a plane not orthogonal to the passage. 5. A nozzle as claimed in any preceding claim, intended for cooperation with an air cap of a spraying apparatus, and wherein the nozzle has cooperating means on a body thereof permitting the nozzle to be indexed, in use, relative to the air cap. 6. A nozzle for a gas-operated spraying apparatus and substantially as hereinbefore described with reference to the accompanying drawing.

Inventors: ILOTT JAN, ILOTT, JAN
Applicants: ILOTT JAN, KODAK LTD, ILOTT, JAN, KODAK LIMITED
Application year: 1989
Main classification: B05B7
IPC codes: B05B1, B05B7, B44D3