GB2279022A - Self-cleaning nozzle assembly for a paint spray gun - Google Patents

Abstract

A paint spray gun nozzle assembly (1) has a nozzle (2) having an orifice (23) for the ejection of fluid. A plunger (5) slides out of and into the nozzle orifice (23) respectively to open the nozzle orifice, to allow fluid to eject from the nozzle, and to close the nozzle orifice, and to expel fluid remaining in the nozzle orifice. The paint spray gun has an outer cover (92) through which the nozzle tip (2) projects when the nozzle assembly is fitted to a paint container (90). When the gun is operated, the container (90) pushes the nozzle assembly forward causing pins (59) on the plunger (5) to strike the shoulder (95) of the cover (92). This arrests the forward movement of the plunger and causes the needle (51) to be withdrawn from the nozzle orifice (23). <IMAGE>

Description

1 NOZZLE ASSEMBLY 2279022 The present invention relates to a nozzle

assembly.

There are many applications in which fluid is ejected from a nozzle. The fluid is usually ejected as a spray in the form of small droplets of liquid. It is often desirable to seal the nozzle orifice through which fluid is ejected when spraying is stopped.

A number of spraying mechanisms have been developed which do not use aerosols so that the propellants which have traditionally been used are no longer necessary. In WO 92/12798, for example. there is disclosed a spray paint "gun" in which an electric voltage is applied to a can of paint to charge the paint droplets on operation of a trigger. When the droplets are sufficiently charged, the nozzle of the gun can be directed at an item to be spray painted. As the item to be painted is usually earthed (such as a vehicle body, metal railings, or the like), the charged paint droplets will be attracted to the item through the nozzle orifice, thereby coating the item with paint.

In such a spray paint gun, and in many other applications, it is desirable to expel the last droplets of liquid from the nozzle orifice after spraying has been completed, particularly in the case of paint, so as to prevent clogging of the nozzle orifice. Furthermore, particularly in the case of the spray paint gun briefly described above, it is desirable that the nozzle tip be relatively distant from the rest of the gun to ensure that the charged paint droplets are kept remote from the paint can and other metal parts of the spray paint gun. According to the present invention. there is provided a nozzle assembly. the assembly comprising: a nozzle having an orifice for the ejection of fluid; 35 a plunger slidable relatively rearwards out of and forwards into the nozzle orifice respectively to open the nozzle orifice, to allow fluid to eject from the nozzle, 2 and to close the nozzle orifice. to expel fluid remaining in the nozzle orifice from the nozzle orifice; and, an outer cover against which the plunger bears during forwards movement of the nozzle relative to the outer cover to cause the plunger to move rearwards relative to the nozzle to open the nozzle orifice.

This construction allows the tip of the nozzle to be relatively small and also allows the part of the plunger which slides into and out of the nozzle orif ice to be relatively short, which means that the vol"e of paint or other fluid between the nozzle shut-off is minimised, thus keeping the amount of paint potentially exposed to the atmosphere as small as possible.

The outer cover may be a separate removable part.

Alternatively. it may be integral with a f luid delivery system which supplies fluid to the nozzle.

The plunger may have a needle of relatively reduced diameter, the needle moving into and out of the nozzle orifice.

The nozzle assembly may further Include a seal f or selectively preventing or allowing f low of f luid to the nozzle orifice. The seal may be mounted on or integral with the plunger, sliding movement of the plunger carrying the seal respectively out of and into sealing engagement with the nozzle.

The assembly may further comprise a cap which has attachment means for f ixing the assembly to a container. sliding movement of the plunger in the relatively rearwards direction being limited by abutment of the plunger with the cap. The cap may have a generally central hollow portion through which fluid is delivered to the nozzle orifice. A separate shroud may be provided. the plunger having guide pins which move in apertures provided in a shoulder on the shroud to guide the sliding movement of the plunger. 35 A sleeve may be fixed relative to the nozzle to define a fluid passage therewith. With this construction. fluid can be directed around the outermost portion of the 3 interior of the nozzle assembly, which allows the moving part or parts of the nozzle assembly to be contained within the centre of the nozzle assembly and out of contact with the paint or other fluid being ejected from the nozzle.

An example of the present invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a partial cross-sectional view of a nozzle assembly with th e nozzle orifice closed; Figure 2 is a partial cross-sectional view of the nozzle assembly with the nozzle orifice open; Figures 3a-d are an elevation, a cross-sectional and end views of a nozzle tip; Figures 4a-d are an elevation, a cross-sectional and end views of a shroud of the nozzle assembly; Figures 5a-d are an elevation, a cross-sectional and end views of a sleeve; Figures 6a-c are an elevation and end views of a plunger; Figures 7a-c are cross-sectional and end views of a seal; Figures 8a-d are an elevation, a cross-sectional and end views of a cap; and, Figure 9 is a schematic partial cross-sectional view of the nozzle attached to a spray paint gun.

A nozzle assembly 1 has a nozzle tip 2 which is fixed in a shroud 3. The nozzle tip 2 has a cylindrical portion 21 of circular cross-section and a conical portion 22 which has an orifice 2 3 at the tip end through which f luid ejects. The cone angle of the nozzle tip 2 is preferably substantially 600 and the nozzle orifice 23 narrows at an angle of 60 passing outwards of the tip 2. At the opposite end of the nozzle tip 2, an annular flange or shoulder 24 extends radially outwards of the cylindrical portion 21, the flange 24 having a dovetail-like cross-section 25. The end wall of the tip 2 beyond the flange 24 is castellated by being formed with material removed from five adjacent 4 portions 26. This castellation provides paint flow paths as will be described in more detail below.

The shroud 3 is generally cylindrical having a circular cross-section. The shroud 3 has a body portion 31 and a nose portion 32 of smaller diameter than the body portion 31, a step or shoulder 33 being provided between the body portion 31 and nose portion 32. The body portion 31 may be externally knurled to provide a better grip for the user. At the end of the nose portion 32 opposite the body portion 31, the shroud 3 has an opening 34 defined by an in-turned collar 35. The collar 35 has a dovetail-like cross-section which corresponds to the dovetail-like cross section of the f lange 24 on the nozzle tip 2. The tip f lange, 24 abuts behind the collar 35 on the shroud 3 to retain the nozzle tip 2 in the shroud 3, the nozzle tip 2 being inserted into the shroud 3 through the body portion 31 end.

The shroud 3 has four equiangularly spaced arcuate apertures 36 through the shoulder 33. Four equiangularly spaced rectangular apertures 37 are also provided through the shoulder 33 and are positioned respectively equiangularly between adjacent pairs of the arcuate apertures 36.

A generally cylindrical sleeve 4 is provided. The sleeve 4 generally has three portions. A first cylindrical body portion 41 has an outer diameter which is substantially the same as the internal -diameter of the nose portion 32 of the shroud 3 so that the sleeve 4 is a tight f it in the nose portion 32 of the shroud 3. The second portion of the sleeve 4 is a neck portion 42. The neck portion 42 has an outer diameter which is somewhat less than the internal diameter of the cylindrical portion 21 of the nozzle tip. The third portion of the sleeve 4 is a frustoconical nose portion 43. The cone angle of the nose portion 43 of the sleeve 4 is substantially the same as that of the conical portion 22 of the nozzle tip 2. A shoulder 44 is formed between the body portion 41 and neck 1 portion 42 of the sleeve 4. The distance from the shoulder 44 and the very tip of the nose portion 43 is less than the distance from the beginning of the orifice 23 and the rear edge of the nozzle tip 2. Accordingly, a channel 10 is defined between the nozzle tip 2 and the sleeve 4. this channel 10 carrying fluid in use.

Towards the rear of the body portion 41 of the sleeve 4, five apertures 45 are formed through the outermost circumferential wall of the body portion 41 to leave an annular semi-circular collar 46 around the upper half of the body portion 41. In the uppermost portion of body portion 41 of the sleeve 4, the sleeve 4 is formed with material removed to define channels 47 in the assembled nozzle assembly 1, the channels 47 being formed between the is remaining material of the upper part of the body portion 41 of the sleeve 4 and the inner circumferential wall of the nose portion 32 of the shroud 3. Accordingly, fluid can pass into the rear of the sleeve 4, up through the respective apertures 45 and then pass along the five channels 47 between the sleeve 4 and the shroud 3, through the spaces 26 forming the castellations in the tip 2 and thence into the channel 10 formed between the neck portion 42 and nose portion 43 of the sleeve 4 and the nozzle tip 2. Thus. fluid is directed generally around the outside of the sleeve 4 ultimately to the orifice 23 in the nozzle tip 2.

A plunger 5 is provided and has a needle 51 which is a taper fit in the nozzle tip orifice 23. The needle 51 enters the nozzle tip orifice 23 to push out any remaining fluid after spraying has been completed. Because the fluid is directed through the channel 10 around the outside of the sleeve 4, the needle 51 can he relatively short, which means that the volume of paint between the seal shut-off (to be described in more detail below) is minimised, thus keeping the amount of paint potentially exposed to the atmosphere as small as possible. Also. fluid can be kept 6 from making contact with at least some of the central operative parts of the nozzle assembly 1.

The plunger 5 has a generally circular plate-like base 52. The base 52 has four generally rectangular recesses 53 which are equiangularly spaced around its periphery. These rectangular recesses 53 correspond to the four rectangular apertures 37 in the shroud 3. A semi-circular wall 54 extends perpendicularly from the base 52 and has a circular end wall 55 which Is generally parallel to the base 52. A nose 56 from the end wall 55. The end of the nose 56 tapers to the needle 51, via a frustoconical portion 57 having a cone angle-of 600.

The semi-circular wall 54 of the plunger 5 is provided with two elongate slots 58 which extend from about one quarter of the way down the semi-circular wall 54 from the end wall 55 towards and through the base 52 as can be seen in the elevation and end views in Figures 6a-c.

The base 52 is provided with four upstanding arcuate guide pins 59 which extend perpendicularly from the base 52 towards the end wall 55 of the semi-circular wall 54. The guide pins 59 are equiangularly spaced around the base 52 and generally lie equiangularly between respective pairs of rectangular recesses 53. The guide pins 59 correspond to the arcuate apertures 36 in the shoulder 33 on the shroud 3.

In the assembled nozzle assembly 1. the forward part of the plunger 5 lies within the body, neck and nose portions 41, 42, 43 of the sleeve 4 with the needle 51 of the plunger extending through the end of the nose portion 43 of the sleeve 4. A generally conical rubber seal 6 is provided to seal the gap between the plunger 5 and needle 51 and the nozzle orif ice 23. The cone angle of the rubber seal 6 is 600. The seal 6 has a through hole 61 through which the needle 51 passes. The rubber seal 6 is a tight f it on the plunger 5 and has a rear wall 62 which sits behind the frustoconical portion 57 of the plunger 5 so 7 that the rubber seal 6 moves back and f orth with the plunger 5 as will be described in more detail below.

As will be clear from the drawings of the assembled nozzle assembly 1, the guide pins 59 on the plunger 5 are slidably received in the arcuate apertures 36 in the shroud 3 so that the motion of the plunger 5 is controlled to be along the longitudinal axis only of the assembled nozzle assembly 1.

A cap 7 is provided which fulfills two prime functions. Firstly, the cap 7 provides an attachment means for fixing the nozzle assembly 1 to a fluid container (to be described in more detail below). This may be in the form of a screw thread 71 provided internally of a cylindrical base portion 72 of the cap 7. Secondly, the cap 7 locks the whole assembly 1 together.

The cap 7 has an annular shoulder 73 which extends radially outwards and inwards of the circumferential wall of the body portion 72. Four arms 74 extend from the shoulder 73 opposite the base 72. The arms 74 are positioned at the outermost periphery of the shoulder 73 and are of rectangular cross-section. The free end of each of the arms 74 terminates in a securing peg 75 which extends a short distance radially outwards. Each peg 75 has a sloping portion 76 on its forward side (the left hand side in the elevation in Figures 8). The position of the arms 74 corresponds to the rectangular recesses 53 in the plunger 5 and the rectangular apertures 37 in the shroud 3, the rectangular apertures 37 in the shroud 3 being large enough to allow a respective peg 75 to pass through the rectangular aperture 37.

A generally semi-circular wall 77 extends parallel to the arms 74 from the innermost periphery of one half of the annular shoulder 73 of the cap 7. A further semi-circular wall 78 similarly extends parallel to the arms 74 from the annular should 73, although this second semi-circular wall 78 is positioned rather closer to the longitudinal axis of the cap 7 than the first semi-circular wall 77. The second 8 semi-circular wall 78 terminates in an end wall 79 which is generally parallel to the shoulder 73. A third semicircular wall 80 extends from the end wall 79 away from the shoulder 73. The outermost surface 81 of the third semi- circular wall 80 tapers slightly towards the longitudinal axis of the cap 7 away from the shoulder 73.

The second semi-circular wall 78 has two elongate ridges 82. The ridges 82 are substantially 900 apart and correspond to the slots 58 in the plunger 5. Each of the elongate ridges 82 has a step 83 and also has a taper at its end 84 beyond the end wall 79, the tapered end 84 corresponding to the tapered surface 81 on the third semicircular wall 80 projecting from the end wall 79. The cap 7 also has two tie bars 85 between the end wall 79 and the semi-circular wall 77 which provide greater rigidity to the cap 7.

The nozzle assembly 1 is assembled by placing the nozzle tip 2 into the shroud 3 as described above so that the dovetail shoulder 24 on the nozzle tip 2 fits into the dovetail in-turned collar 35 on the shroud 3. The sleeve 4 is then inserted into the shroud 3 until the shoulder 44 on the sleeve 4 abuts the rear surface of the nozzle tip 2. The rubber seal 6 is placed over the needle 51 and frustoconical portion 57 of the plunger 5. The plunger 5 is then inserted into the sleeve 4 so that the needle 51 passes through the sleeve 4 and orifice 23 in the nozzle tip 2. At the same time, the guide pins 59 on the plunger 5 enter the arcuate apertures 36 in the shroud 3. A coil compression spring 8 is inserted into the sleeve 4 to abut the base 55 of the plunger 5. Finally, the cap 7 is brought into engagement with the remainder of the nozzle assembly 1 to lock the assembly 1 together. In particular,, the tapered portions 81,84 at the nose of the cap 7 are pushed as a force-f it into the rear of the sleeve 4 and the steps 83 engage the rear of the sleeve 4. The compression spring 8 is retained within the third semi-circular wall 80 of the cap 7 and the extension of the elongate ridges 82 on 9 the cap 7 and is compressed between the end wall 79 of the cap 7 and the end wall 55 on the plunger 5. At the same time, the pegs 75 on the arms 74 of the, cap 7 can pass through the rectangular apertures 37 in the shroud 3 by means of the angled surf aces on the pegs 75 riding over the radially outermost walls of the rectangular apertures 37, the pegs 75 f inally snapping outwards by virtue of the resilience of the material of the cap 7 to lock the cap 7 relative to the shroud 3. The arms 74 are received in the rectangular recesses 53 in the plunger 5.

With the nozzle assembly 1 assembled as described above, fluid can enter the central portion of the cap 7 at its rear and then pass between the first and second semicircular walls 77, 78 of the cap 7. Fluid can then pass between the space formed between the free end of the first semi-circular wall 77 and the end wall 79 to the channel 47 f ormed between the sleeve 4 and the shroud 3 and to the channel 10 formed between the sleeve 4 and the nozzle tip 2 as described above.

In use, the assembly 1 is fitted to a container 90, shown schematically in a paint gun 91 in Figure 9, by screwing the cap 7 onto a screw thread provided on the container 90. A further outer cover 92 is then fitted over the nozzle assembly 1, with the nozzle tip 2 projecting through the outer cover 92. The outer cover 92 has a generally cylindrical portion 93, which fits over the body of the paint gun 91, and a generally frustoconical portion 94, which fits over the nozzle assembly 1. The frustoconical portion 94 is provided internally with a shoulder 95. When the paint gun 91 described above is operated, the container 90 is pushed forward relative to the housing of the gun 91 and the outer cover 92. This pushes the whole nozzle assembly 1 relatively forward. However, the position and size of the internal shoulder 95 of the outer cover 92 is set so that the free ends of the guide pins 59 of the plunger 5 strike this internal shoulder 95 and prevent further relative forward movement of the plunger 5. Thus, further movement of the remainder of the nozzle assembly 1 forwards causes the plunger 5 to be relatively withdrawn. withdrawing the needle 51 from the nozzle tip orifice 23. thereby allowing paint in this 5 example to be ejected from the nozzle tip orifice 23.

When the gun is released following completion of spraying, the nozzle assembly 1 is withdrawn and the compression spring 8 forces the nozzle tip 2 and container 90 relatively backwards (rightwards in Figures 1 and 2) 0 pushing the needle 51 into the nozzle tip orif ice 23, thereby ejecting any remaining liquid from the nozzle tip orifice 23.

Instead of being a separate component which is removably fixed to the spray paint gun, the outer cover 92 may be integral with the spray paint gun, or may be hingedly fixed to the spray paint gun. for example.

The shape of each of the components of the nozzle assembly 1 in the example described above is such that moulding of these components (apart from the spring 8) is very straightforward since, in most parts. there are no undercuts or deeply recessed parts. Thus, most of the moulds used can be simple two- piece moulds without any sliding fingers or the like needed to mould more complex pieces.

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Claims (11)

1. A nozzle assembly, the assembly comprising:

nozzle having an orifice for the ejection of fluid; plunger slidable relatively rearwards out of and forwards into the nozzle orifice respectively to open the nozzle orifice, to allow fluid to eject from the nozzle, and to close the nozzle orifice, to expel fluid remaining in the nozzle orifice from the nozzle orifice; and, an outer cover against which the plunger bears during forwards movement of the nozzle relative to the outer cover to cause the plunger to move rearwards relative to the nozzle to open the nozzle orifice.

is

2. A nozzle assemble according to claim 1, wherein the plunger has a needle of relatively reduced diameter, the needle inoving into and out of the nozzle orifice.

3. A nozzle assemble according to claim 1 or claim 2, comprising a seal for selectively preventing or allowing flow of fluid to the nozzle orifice.

4. A nozzle assembly according to claim 3, wherein the seal is mounted on or integral with the plunger, sliding movement of the plunger carrying the seal respectively out of and into sealing engagement with the nozzle.

5. A nozzle assembly according to any of claims 1 to 4, comprising a cap which has attachment means for fixing the assembly to a container, sliding movement of the plunger in the relatively rearwards direction being limited by abutment of the plunger with the cap.

6. A nozzle assembly according to claim 5, wherein the cap has a generally central hollow portion through which fluid is delivered to the nozzle orifice.

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7. A nozzle assembly according to any of claims 1 to 6, comprising a shroud, the plunger having guide pins which move in apertures provided in a shoulder on the shroud to guide the sliding movement of the plunger.

8. A nozzle assembly according to any of claims 1 to 7, comprising biasing means for biasing the plunger into the nozzle orifice.

9. A nozzle according to any of claims 1 to 8, further comprising a sleeve fixed relative to the nozzle and defining a fluid passage therewith.

10. A spray paint gun, including a nozzle assembly is according to any of claims 1 to 9.

11. A nozzle assembly, substantially as described with reference to the accompanying drawings.