BACKGROUND OF THE INVENTION
Many designs of spray gun are already known. In particular, spray guns for use with viscous materials, such as damp-proofing materials, underfloor sealing materials, bituminous and plastic materials, must have the most manageable and constructively simple design possible, which is easy to clean and which is made up of relatively few individual parts.
In one well-known spray gun the compressed air is supplied by means of the grip . The viscous material is fed into the section of the spray gun case in front of the grip and when pressure is applied to the finger grip it is forced out by the compressed air. This design has, however, the disadvantage that when pressure on the finger control is removed, the stream of viscous material is not checked immediately, so that after spraying some viscous material is discharged into the open. Also the complicated structure of the spray gun means that untrained personnel cannot dismantle or clean it. It is also necessary to operate two separate plungers simultaneously in order to close and open the material or compressed air lines. This leads to difficulties in sealing the supply chamber for the material to be sprayed. Since sealing occurs as a result of linear contact of the two sealing surfaces, there is always the danger that when granular or coarse materials are sprayed, leakage may occur if small particles become lodged between the surfaces. Only a few drops of water are sufficient, when working with viscous materials, to cause the material in the chamber to harden and therefore to make the gun unusable.
SUMMARY OF THE INVENTION
The purpose of the invention is to provide an almost guaranteed design by simple means, and to overcome the above disadvantages.
This has been achieved by a spray gun of the above-described design. The plunger is supported by means of a tongue against the wall, and the front section of the plunger which forms a hollow chamber ends in a nozzle, Z-shaped in longitudinal section and forming, with its crosspiece and its lower side-section, an axial ad a radial ring-shaped sealing surface so that on closing, a ring-shaped seal slides over the radial sealing surface and comes to rest against the axial sealing surface and the force of the spring acting on the hollow plunger presses against them both and forms a solid unit from both sections of the plunger. The oblique connection between the compressed air canal and the hollow plunger is so arranged that when the gun is set into operation the compressed air supply is opened first and then the viscous spraying material is released, and on switching off, the reverse procedure occurs.
Simple pressure on a sealing surface against a sealing ring is no longer involved, but the sealing ring slides first over a sealing surface until it reaches a second sealing surface where it is pressed against the sealing surface over a large area over which it has already passed with its front section. This sliding movement has the advantage that the sealing surface is freed from contamination, so that the sealing area which follows lies against a cleaned sealing surface.
A further aim of the invention is concerned with the problem which occurs, for example, when spraying mortor containing particles of varying size, in obtaining uniform distribution of the larger particles over the surface to give uniform build-up. This is necessary to ensure uniform granulation and uniform strength.
When using conventional nozzles the air stream is bundled to a high degree, so that uneven distribution of the mortor on the wall results. It is therefore possible that there is a greater coating power at the center of the air stream, than is the case in the peripheral region. This is an undesirable side-effect in spray guns.
In order to overcome this it is suggested that a constriction be placed in the region of the nozzle.
This ensures that the air-stream is broken or made turbulent, so that the air flow at the edges of the plaster formation is rather stronger than in the central region.
This is conveniently done by shaping the internal section of the nozzle, at least within the protruding free end-section, into the shape of a cone. This causes an obstruction and turbulence in the air supply so that uniform uptake of the material to be sprayed is guaranteed. This is easy to accomplish from the constructive point of view.
DESCRIPTION OF THE DRAWINGS
Illustrative and non-limiting embodiments of this invention are shown in the drawings wherein:
FIG. 1 is a partial cross-sectional view of one form of spray gun of this invention, shown in closed position;
FIG. 2 is a view of the parts shown in FIG. 1 with the hollow plunger moved to its intermediate open position;
FIG. 3 is a view of the parts shown in FIG. 2 with the hollow plunger moved to its final open position;
FIG. 4 is an enlarged cross-sectional view showing the nozzle part of the spray gun of FIG. 1 in more detail;
FIG. 5 is an enlarged cross-sectional view of another form of nozzle part that can be used in the spray gun of this invention;
FIG. 6 is a partial cross-sectional view showing the nozzle part of FIG. 5 affixed to a hollow plunger, shown in final open position, as used with a modified sprayhead presenting an annular sealing surface;
FIG. 7 is a partial cross-sectional view of another form of spray gun having needle valve affixed to the plunger cooperating with a nozzle insert adapted for use with viscous materials such as paints or lacquers and shown in the closed position;
FIG. 8 is a view of the spray gun shown in FIG. 7 with the parts in the intermediate open position; and
FIG. 9 is a view of the spray gun shown in FIG. 8 with the parts shown in the open position.
In the drawings, parts with the same function are indicated with the same reference number, in the usual way.
The new spray gun is shown in the closed position in FIG. 1, in the middle position in FIG. 2, and in the open position in FIG. 3. Its main parts are the housing 1 with the finger control 2 and the handgrip 10. Inside the housing 1 is a moveable plunger 11, 12. Its movement is caused by means of a connecting rod, connected to the finger control 2, the simplicity of which lies in that it is only linked to the end of the plunger at 3, and into the housing 1, at the point 26.
The plunger consists of a forward hollow section 12, and a rear plunger shaft 11, which has a smaller cross-section. Inside the housing 1, there is a cylindrical chamber 17, surrounding the plunger shaft 11, in which the screw spring 15 is situated. At one end this presses against the plunger ring surface 16 of the hollow plunger 12, and at the other against the rear wall of the cylinder 19. The end of the plunger shaft 11, within the rear section of the housing is provided with a thread 4, on to which is screwed the nut 5. By screwing or unscrewing the nut 5 the plunger 11, 12 can be positioned within the housing 1 and so determining the sealing pressure. This will be considered later.
At the front end of the hollow plunger 12, is fitted a nozzle 9, the opening of which is indicated by the number 23. The compressed air streams through a canal 13 inside the handgrip 10 in the direction of arrow 6, into the cylinder 17 and when the position is that shown in FIG. 1 it can go no further. Since the finger control 2 is not engaged, the screw spring 15 can act solely on the plunger ring surface 16 and press the plunger against the direction of the arrow 8 with its nozzle 9 against a seal 25 with a flange 27. In this way the supply line 14 for the viscous material to be sprayed, which enters in the direction of arrow 7, is blocked. The seal 25 is narrowed in a conical shape to fit the nozzle 9 and together with its sealing flange 27, fixed into a nozzle flange 22 in the front nozzle insertion 32. The funnel-shaped exit flange 28 of the nozzle insertion 32 repeats the angle of inclination of the lip-shaped section of the packing 25, so that a smooth uniform exit surface is formed. The cycle which occurs when the spray gun is set into operation is as follows:
With the position as indicated in FIG. 1 the finger control 2 is pressed in the direction of arrow 42, and the plunger 11, 12 is pulled in the direction of arrow 43 and first takes up the position shown in FIG. 2. In this position the hole 18 in the hollow plunger 12 is so far to the right that it is connected with the cylinder 17 and the canal 13, while the seal 25 still keeps the viscous material line 14 closed. The compressed air now flows from canal 13 and the cylinder 17 through the hole 18 into the chamber 44 of the hollow plunger 12 and leaves the nozzle opening 23 against the direction shown by arrow 8. Further movement of the plunger in the direction of arrow 43 results in the position shown in FIG. 3. Here the seal 25 is released from the nozzle 9, so that the material to be sprayed can exit through the ring-shaped opening thus formed over the nozzle insertion 32.
When the spray gun is switched off the processes are repeated in the reverse order. First the spray material stream is cut off and the supply line sealed and only then is the compressed air supply cut off. Thus in the closed position the hole 18 remains in such a position that there is a small gap through which compressed air can flow. This prevents contaminating particles entering the chamber 44 of the hollow plunger 12 through the nozzle opening 23 of the nozzle 9 in the direction of arrow 8. The nozzle 9, which can be easily fixed to the hollow plunger 12, e.g., by screwing, has in longitudinal section a Z-shaped configuration and the lower side-pieces by bending inwards from the conical nozzle opening 23. The lower side-piece 36 (FIG. 3) forms the radial sealing surface, while the step 34 provides the axial sealing surface. On sealing the seal 25 slides with ring-shaped contact and without causing much resistance, over the front cylindrical section 36 of the nozzle 9 and cleans from it any particles of spray material which may be present. The rear surface 35 of the seal 25 then meets the flat step 34, and as a result of the pressure of the screw spring 15 and the conical shape of the seal 25, exerts a component force which presses the seal 25 against both the step 34 and the cylindrical section (lower side-piece 36) of the nozzle 9. In this way any leakage of liquid from the viscous material line 14 is effectively prevented.
A collar 24 seals the viscous material line 14 from the hollow plunger 12. Connecting nipples for the compressed air and the material to be sprayed are provided on the grip 10, but the details are not shown. A control for the compressed air supply, which operates in the usual way, can also be fitted.
The nozzle insertion 32 is fixed into the front section of the housing 1 by means of a fixing ring 45. The hollow plunger 12 moves in the seating 20 and the plunger shaft 11 in the seating 21.
In FIG. 4 the nozzle 9 is shown enlarged. It can be seen that the nozzle in section has an almost perfect Z-shape and is formed from two sections with an intermediate step 34.
The two sections form the true nozzle opening and the thread 60. The nozzle opening 23 has a constriction 59 which sets the exiting compressed air into turbulent motion.
The internal cross-section of the nozzle 9 is such that it narrows in a conical fashion towards the free end. This cone 61, makes an angle of approximately 45° with the middle axis of the nozzle, but this of course may alternatively be larger. Choice of a smaller angle reduces the amount of turbulence set up in the air stream. The nozzle opening 23 widens again in the front section, so that at the constriction 59, an edge is formed which is set back a little from the front edge of the nozzle 9. It is advantageous if a line extending from the opening 23 and a line extending from the side of the nozzle cone 61 make an approximate right angle with each other.
The surfaces 62, on which the viscous material slides, do not have the sharp edges which are formed in the constriction 59.
The conical surfaces formed inside the extension to the nozzle 63 are in the same plane as the opening of the spray material nozzle. Since the seal 25 of this material nozzle is made from elastic material it can be bent by a stream of air, although only slightly. This means that no dead room can arise in the material nozzle, i.e., the air stream completely penetrates the material nozzle and removes the spray material, so that along these surfaces complete air circulation occurs. In this way a considerable quantity of material is retained despite the setting up of turbulence in the air stream.
This development has the great advantage that the edges formed by the constriction 59 and the extension 63, are not involved in sealing. The sealing function is carried out much more by the surface 62, which retain this function until the seal 25 is inserted into the angle 65. It is, of course possible, should it be necessary, to insert a seal corresponding to the profile of seal 25, perhaps a ring seal, into this angle 65. Furthermore of course, it is also possible to use a metal ring in place of the seal 25, in which case the metal ring must be made so that its diameter fits accurately over that of the nozzle 9, or it must be fitted with an elastic seal which can fit into the angle 65 of the nozzle 9.
From FIG. 4 it can also be seen, that the hollow plunger 12 is provided with an external thread, so that the nozzle 9 can be screwed on to the hollow plunger 12.
A modification example is shown in FIG. 6, in which another shape of nozzle and a different type of material nozzle is used. Here the front section 66 of the nozzle 9 is much more cylindrical in shape. Here also there is a constriction 59 which causes air turbulence. The cone formed by the constriction merges into a further relatively flat cone 58, so that the internal cross-section of the nozzle 9, gradually widens towards its end. Furthermore in this case, the external diameter of the nozzle 9, is not greater than the diameter of the hollow plunger 12, so that together they form a smooth cylindrical surface. This was made possible by the nozzle carrying an external thread and the hollow plunger 12, an internal thread. This means that the viscous material to be sprayed is in contact with the rear side of the threaded section of the nozzle 9. The viscous material therefore meets with less resistance.
The material nozzle shown in FIG. 6 is of such design, that a commercially available unit can be used for seal 25, since it has an almost cylindrical form. With regard to the fact that the sealing unit is very much stressed during rough use, this design has particular advantages. Replacement is simple.
With reference to the nozzle form, the example in FIG. 5, is a similar type of design as that in FIG. 6, and carries the same reference numbers. This shows a further modification of nozzle 9 to give yet another method for connecting it to the hollow plunger 12.
The hollow plunger 12 is cut away and provided with an external thread, while the nozzle 9 carries an internal thread. The advantage already described for FIG. 6 also exists in this case, namely that the viscous material has no anchoring points to give rise to build-up.
The nozzle designs outlined in the invention have important advantages, which lie not only in the particularly troublefree operation during spraying, but also in their simple construction and freedom from maintenance, the latter being particularly important with rough use on the building site. In FIGS. 7 to 9 the invention is extended to spray for paint and lacquer. Here also the plunger shaft 11 is fitted with a thread 4, on to which a nut 5 is screwed. The cylinder 17 is closed at the back by a sealing plate 54. The hollow plunger 41 is provided at the front end with an external thread 55, on to which a cap 38 is screwed to form with the hollow plunger 41, a cylindrical chamber 40. In the chamber 40 there is a needle nozzle 29 with a collar 37 seated so as to be movable. Also there is a spring 39 in the chamber 40. The plunger shaft 11 carries a sealing collar 53, the sealing surface of which 52 presses with close contact against the sealing surface 51 of a neck 50 in the housing. In this model, the paint leaves the center of the nozzle 56, while the air leaves the gun through a ring-shaped aperture. The needle nozzle 29 operates with the nozzle insertion 33 design for paints. A cap 31, which can be attatched is fixed to the housing 1 with a fixing ring 30, so that a ring-shaped chamber is formed 48. The procedure for spraying is as follows: The compressed air is supplied through canal 13 in the direction of arrow 6 into the cylindrical chamber 17, where it is stopped by the sealing collar 53 and cannot go further. The plunger shaft 11 is moved in the direction of the arrow 43 by pressure on the finger control 2 carrying the middle section backwards as shown in FIG. 8, so that the compressed air passes from the canal 13 and the cylinder 17 through the ring-shaped canal 18a into another intermediate chamber 46 in the housing 1. From there it passes through canal 47 into the ring chamber 48 and exits in the direction of the arrows 49. In this intermediate stage shown in FIG. 8, the nozzle insertion 33 keeps the paint or lacquer inlet closed and the spring 39 holds the needle nozzle 29 in the closed position. If the plunger shaft is moved further towards the position shown in FIG. 9 the needle nozzle operates and the paint can emerge from the center 56 of the nozzle insertion 33. The exiting paint is ejected directly into a pressurized air flow which surrounds it. On closing the operations are reversed as in the case of the guns described in FIGS. 1 to 3. First the paint supply is cut off and then the compressed air is disconnected. The number 24 is given to a collar which seals the needle nozzle 29 from the intermediate chamber 46.