Technical field of the invention

The present invention relates to a device for applying an unhardened plaster material to a surface.

Background of the invention

The application of a plaster material to a surface, including walls, can be hard and time-consuming work, since it is often necessary to use tools, such as filling knives, in order to ensure a homogenous distribution and an even thickness of the material.

Several plaster materials are known that contain filler material. These plaster materials are often difficult to apply and often require some form of post processing before paint or wall coverings, such as wallpaper or the like, can be applied. Furthermore, it is known that granular stone wool may be used as a filler. In this way, a plaster material is obtained, which with only one application, regardless of the thickness, will result in a smooth and even surface, which does not crack or collapse when settling, and after a normal hardening period and without finishing can be exposed to all know types of paints and wall coverings, such as wall paper and similar coverings.

DD272962A3 describes a spray gun suitable for application of an unhardened plaster material. The spray gun comprises and inlet, an outlet and at least one compressed-air inlet and a compressed-air nozzle. The compressed air-nozzle encircles a material outlet in such a way that the material is air-guided during delivery and application. However, this configuration has certain limitations when it comes to distributing the material in an efficient way.

A solution that solves the above-mentioned problems, including problems related to the application of the material, is therefore desirable. Description of the invention

It is one object of the present invention to provide a solution that solves the above-mentioned problem.

The inventor of the present invention has built a spray gun that is able to evenly apply a layer of plaster material to a surface, such as a wall. The spray gun can feed the plaster material in a direction away from the spray gun and at the same time provide an air lift for the unhardened plaster material.

One aspect relates to a spray gun suitable for applying unhardened plaster material to a surface, wherein said spray gun comprises an inlet for reception of a plaster material, an outlet for delivery of the plaster material, at least one compressed-air inlet, and a first and a second compressed-air nozzle, where the outlet is designed as an elongated slot, and where the first and the second compressed-air nozzle is arranged in parallel to said outlet above and below this respectively, and where the first and the second compressed-air nozzle is capable of feeding the plaster material in a direction away for the spray gun and of providing a lift of the unhardened plaster material.

A second aspect relates to a spray gun suitable for applying unhardened plaster material to a surface, comprising a first inlet adapted for reception of a plaster material, a first outlet adapted for delivery of the plaster material, at least one second inlet adapted for receiving compressed-air, and a first and a second air nozzle in air communication with the second inlet; wherein the first outlet is designed as an elongated slot, and wherein the first and second air nozzles are each arranged parallel to said first outlet; wherein the first air nozzle is positioned above said first outlet, and the second air nozzle is positioned below said first outlet.

A third aspect relates to a system for applying unhardened plaster material to a surface, comprising: - a spray gun according to the present invention; and

- a guide rail adapted for guiding the spray gun across a surface.

The term“spray gun” refers to a tool suitable for spraying/delivering a liquid material, such as an unhardened plaster material. In the present context, the term“unhardened plaster material” refers to a mixture consisting of plaster, filler, and preferably water or other liquid acting as catalyst, curing agent, or solvent. The unhardened plaster material preferably has a viscosity suitable for application with a spray gun according to the present invention. After application to a surface, e.g. after 15 minutes to 24 hours, the unhardened plaster material will harden and thereby become hard. The filler may e.g. be stone wool. The filler may e.g. be mixed with plaster before adding water or other liquid. Furthermore, adhesive material and/or possible coloring agents may be admixed.

A surface may be a wall, e.g. a wall covered by insulation, such as stone wool, where it is desired to cover said stone wool with a plaster material. Plaster material may thus be an alternative to mounting of molded plasterboards, which can be very hard work.

The size of the spay gun is not as such limited but may be adjusted to its specific use. E.g. a handheld spray gun may be smaller than a spray gun held by a robotic arm or a chassis. The different parts of the spray gun may therefore be sized accordingly.

In one or more embodiments, the first outlet has a length of at least 5 cm, such as at least 10 cm, e.g. at least 15 cm, such as at least 20 cm, e.g. at least 25 cm, such as at least 30 cm, e.g. at least 35 cm, such as at least 40 cm, e.g. at least 45 cm. The longer the first outlet is, the larger the treatment area. The width is also important to be able to provide an even flow of unhardened plaster material. If too narrow, filler material may clot the first outlet, and if too wide, the amount of unhardened plaster material will be too large to be carried by the air stream from the air nozzles. Preferably, the first outlet has a width of at least 2 mm, such as within the range of 2-20 mm, e.g. at least 3 mm, such as within the range of 3-19 mm, e.g. at least 4 mm, such as within the range of 4-18 mm, e.g. at least 5 mm, such as within the range of 5-17 mm, e.g. at least 6 mm, such as within the range of 6-16 mm, e.g. at least 7 mm, such as within the range of 7-15 mm, e.g. at least 8 mm, such as within the range of 8-14 mm, e.g. at least 9 mm, such as within the range of 9-13 mm, e.g. at least 10 mm, such as within the range of I Q- 12 mm, preferably within the range of 3-15 mm. The upper range may be dependent on the size of spray gun.

In one or more embodiments, the first outlet has a length of at least 5 cm, and a width within the range of 2-20 mm, preferably within the range of 3-15 mm.

It is preferred that the cross-sectional area of the first outlet is identical to the cross-sectional area of the first inlet in order to avoid accumulation of the plaster material in the housing of the spray gun. The cross-section of the inlet can be e.g. circle shaped, which will make it easy to attach to a hose.

The first and the second air nozzles are arranged in parallel above and under the first outlet and are preferably substantially smaller than the first outlet. The first air nozzle may be configured as a single air nozzle. In this situation, it is preferred that the length of the first air nozzle is substantially the same as the first outlet. The width if the first air nozzle in this configuration is preferably narrower than the width of the first outlet, such as within the range of 0.1 -4 mm, such as 0.2-3 mm, e.g. 0.3-2 mm, such as 0.4-1.9 mm, e.g. 0.5-1.8 mm, such as 0.6-1.7 mm, e.g. 0.7-1.6 mm, such as 0.8-1.5 mm, e.g. 0.9-1.4 mm, such as 1.0- 1.3 mm, e.g. 1.1 -1.2 mm. The second air nozzle may be configured as a single air nozzle. In this situation, it is preferred that the length of the second air nozzle is substantially the same as the first outlet. The width if the second air nozzle in this configuration is preferably narrower than the width of the first outlet, such as within the range of 0.1 -4 mm, such as 0.2-3 mm, e.g. 0.3-2 mm, such as 0.4-1.9 mm, e.g. 0.5-1.8 mm, such as 0.6-1.7 mm, e.g. 0.7-1.6 mm, such as 0.8-1.5 mm, e.g. 0.9-1.4 mm, such as 1.0-1.3 mm, e.g. 1.1 -1.2 mm. Preferably, a plurality of both first and second air nozzles are present, but the combination of a single first air nozzle with a plurality of second air nozzles is also possible, and vice versa. The distance between the air nozzles and the first outlet may vary, but the first and second air nozzles, respectively, are preferably positioned in line to provide a homogenous air flow. The first air nozzles may be positioned at a different distance from the first outlet than the second air nozzles. In one or more embodiments, the spray gun is configured to vary the distance between the first outlet and the air nozzles. The parts of the spray gun holding the air nozzles may e.g. be moved relative to the part holding the first outlet.

In one or more embodiments, the spray gun comprises at least one first and second air nozzle per 5 mm length of the first outlet, such as 1 -25 of each first and second air nozzle per 5 mm length of the first outlet, e.g. 2-20 of each first and second air nozzle per 5 mm length of the first outlet, such as 3-15 of each first and second air nozzle per 5 mm length of the first outlet, e.g. 4-10 of each first and second air nozzle per 5 mm length of the first outlet, or 1 -5 of each first and second air nozzle per 5 mm length of the first outlet, e.g. 2-3 of each first and second air nozzle per 5 mm length of the first outlet. The number of air nozzles depend on their diameter or length. Preferably, each first and second air nozzle has a diameter or length within the range of 0.1 -4 mm, such as 0.2-3 mm, e.g. 0.3-2 mm, such as 0.4-1.9 mm, e.g. 0.5-1.8 mm, such as 0.6-1.7 mm, e.g. 0.7-1.6 mm, such as 0.8-1.5 mm, e.g. 0.9-1.4 mm, such as 1.0-1.3 mm, e.g. 1.1 - 1 .2 mm.

Preferably, each first and second air nozzle has a width within the range of 0.1 -4 mm, such as 0.2-3 mm, e.g. 0.3-2 mm, such as 0.4-1.9 mm, e.g. 0.5-1.8 mm, such as 0.6-1.7 mm, e.g. 0.7-1.6 mm, such as 0.8-1.5 mm, e.g. 0.9-1.4 mm, such as 1.0-1.3 mm, e.g. 1.1 -1.2 mm. In one or more embodiments, each first and second air nozzle is positioned 2-20 mm from the first outlet, such as 3-19 mm, e.g. 4-18 mm, such as 5-17 mm, e.g. 6-16 mm, such as 7-15 mm, e.g. 8-14 mm, such as 9-13 mm, e.g. 10-12 mm from the first outlet.

In this way, a spray gun is provided, which is suitable for application of an unhardened plaster material to a surface, e.g. a wall, where the unhardened plaster material may be sprayed onto this surface homogeneously. The homogeneous distribution of the unhardened plaster material is secured by the elongated first outlet, which constitutes the outlet of the plaster material, and the first and second air nozzles. Providing the spray gun with first and second air nozzles enables it to manipulate the mentioned unhardened plaster material. In a typical use situation, the user of the spray gun will make sure that the slot is horizontal, such that gravity will cause the plaster material (without supply of compressed air) to fall like a waterfall out of the first outlet. By arranging the first air nozzle under the first outlet (i.e. in parallel to the first outlet in a use situation, where the elongate first outlet is horizontal), the compressed air supplied from said air nozzle will cause the unhardened plaster material to be lifted in such a way that it doesn’t just drop strait down after leaving the first outlet. In other words, the compressed air is delivered homogeneously along the first outlet. Furthermore, by providing the spray gun with a second air nozzle arranged above the first outlet (under the same conditions as mentioned earlier), the said second air nozzle will cause the unhardened plaster material to be delivered with a certain power and speed such that the user may be able to position himself at a certain distance from (e.g. 1 m) the surface, which is to be covered by plaster material. By adjusting the pressure of the compressed air, it is possible to adjust the thickness of the unhardened plaster material being applied to the surface. The configuration of the spray gun of the present invention is an improvement compared to DD272962A3, since this document describes a material outlet encircled by an air nozzle, which does not in the same way facilitate a delivery and lift of said material. The present invention results in an improved work situation towards applying a homogeneous layer of unhardened plaster material, as achieved by the present invention.

The described use of a spray gun provides an easy and economical way of applying a plaster material, thereby resulting in great saving of working time compared to know methods. Due to the homogeneous distribution of the unhardened plaster material on the surface, the subsequently hardened plaster material is suitable for further processing, e.g. application of paint or wall coverings.

In one or more embodiments, the first and second air nozzle are angled towards each other.

A third aspect relates to a system for applying unhardened plaster material to a surface, comprising:

- a spray gun according to the present invention; and

- a guide rail adapted for guiding the spray gun across a surface.

The guide rail is especially suitable for relatively large spray guns or at least for relatively large surfaces. The guide rail may be configured for releasably fastening to the ground and extend upwards relative to the ground. Alternatively, or additionally, the guide rail may be releasably fastened to a ceiling.

In one or more embodiments, the spray gun is releasably fastened to a bracket being slidably connected to the guide rail.

In one or more embodiments, the guide rail comprises two elongate rods, and wherein the spray gun is directly or indirectly (e.g. through a bracket) connected thereto. The elongate rods may in one end be configured for releasably fastening to the ground and extend upwards relative to the ground. Alternatively, or additionally, the elongate rods may in another end be configured for releasably fastening to a ceiling. The pressure from the applied unhardened plaster material released from the first outlet may be enough to slide the spray gun up the elongate rods. Alternatively, the bracket may be motorized and configured for crawling or sliding up and down the two elongate rods. Obviously, the hose delivering the unhardened plaster material to the spray gun needs to be of a length suitable for the spray gun being able to slide up and down the two elongate rods.

In one or more embodiments, the elongate rods are telescopic. Alternatively, the elongate rods may be configured for connection to extension rods.

A fourth aspect relates to a system for applying unhardened plaster material to a surface, comprising:

- a spray gun according to the present invention; and

- a robotic arm adapted for guiding the spray gun across a surface.

As used in the specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" or "approximately" one particular value and/or to "about" or "approximately" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about", it will be understood that the particular value forms another embodiment.

It should be noted that embodiments and features described in the context of one of the aspects of the present invention also apply to the other aspects of the invention.

Brief description of the figures

Figure 1 illustrates the spray gun according to the invention seen in perspective; Figure 2 illustrates a spray gun according to the invention seen in the direction towards its outlet;

Figure 3 illustrates a spray gun according to the invention seen from the side; and

Figure 4 illustrates the spray gun in use.

Detailed description of the invention

In the following, the invention will be described in detail by embodiments, which are not to be construed as limiting for the scope of the invention.

Figure 1 illustrates a spray gun 100 in perspective. The spray gun comprises a housing 101 with a first inlet 102 for the reception of an unhardened plaster material, and a first outlet 103 for delivery of said unhardened plaster material. Furthermore, the spray gun 100 comprises a first air inlet 1 1 1 and a second air inlet 112. Each air inlet 1 1 1 , 112 having substantially the same length as the first outlet 103, and a width that is narrower than the width of the first outlet 103. The mentioned air inlets 11 1 ,1 12 leads the compressed air into each first 1 13 and second cavity 1 14, respectively, wherefrom the compressed air is led further on towards the first air nozzle 1 15 (from the first cavity 1 13) and the second air nozzle 1 16 (from the second cavity 1 14). Thereby, the air pressure may be individually regulated through the first 1 15 and second 1 16 air nozzle. The air nozzles 1 15,1 16 are arranged in parallel to the outlet 103, which is best illustrated in Figure 2. The first outlet 103 is configured as an elongated slot, which is also best illustrated in Figure 2. The function of the spray gun 100 is to lead the unhardened plaster material from the first inlet 102 through the housing 101 , and further on out of the first outlet 103. The first 1 13 and the second 1 14 cavities are arranged above and under a part of said housing 101 , respectively, in order for the compressed air to be led out of the air nozzles 1 15, 1 16. In other words, a part of the housing 101 , especially the part near the first outlet 103, is placed between the first 113 and the second 1 14 cavity. Thereby, the air nozzles 1 15,1 16 correspondingly result in an elongated slot that runs above and under the outlet 103. In this configuration, the air nozzles 1 15,1 16 are each configured as a single slot. However, it may be an advantage to provide a spray gun with multiple air nozzles 1 15,1 16 positioned in line and parallel to the elongate first outlet.

Figure 2 is a better illustration of the outlet 103 and the air nozzles 1 15,1 16.

From the air inlets 1 1 1 (reference number 1 12 not shown), the compressed air is led further into the first 1 13 and the second cavity 1 14, respectively, and further towards the first air nozzle 1 15 and the second air nozzle, respectively. In a preferred embodiment, the two air nozzles 1 15,1 16 are thereby independent of each other, which allows for manipulation of the functions of the spray gun 100. It is to be noted that the first and second cavities 1 13,1 14 are merely a connection between the air inlets 1 1 1 ,1 12 and the air nozzles 1 15,1 16, the extent of which can be limited though simple design changes. In Figure 2, it is to be noted how the first outlet 103 is provided as an elongated slot, and how the first air nozzle 1 15 and the second air nozzle 1 16 are arranged in parallel to this slot/outlet. In a preferred embodiment, the cross-sectional area of the first outlet 103 is identical to that of the inlet (not shown), in order to avoid accumulation of the unhardened plaster material. The first 1 15 and second 116 air nozzles allow the unhardened plaster material leaving the first outlet 103 to be lifted and carried forward

(accelerated), thereby allowing the spray gun to apply the unhardened plaster material from a certain distance and more efficiently. Accelerating the plaster material allows it to be spread over a larger area. Furthermore, it is to be noted that the opening/aperture of the air nozzles 1 15,116 may vary, allowing for an adjustment of the operation.

Figure 3 illustrates the mouth of the spray gun 100 seen from the side. It is especially to be noted how the first outlet 103 is flanged by the first 1 15 and the second 1 16 air nozzle, which are in air communication with the first cavity 1 13 and the second cavity 1 14, respectively. These cavities 1 13,1 14 are furthermore in air communication with the air inlets (not shown), but as mentioned, a change in the design can reduce or make the cavities superfluous, if the air inlets are led directly to the air nozzles 1 15,1 16. It should also be noted how the second air nozzle 1 16, arranged under the first outlet 103, is angled differently relative to the first outlet than the first air nozzle 1 15. These differences cause the plaster material to leave the outlet 103 in the most optimal direction for the unhardened plaster material to be distributed in the most homogenous manner on a surface.

Figure 4 illustrates the spray gun 100 with the air pressure turned off (Figure 4a) and the air pressure turned on (Figure 4b). The unhardened plaster material 200 is illustrated with a dashed line, even though it should be noted that it is not part of the invention. In Figure 4a, the lack of compressed air makes the plaster material 200 leave the first outlet 103 with only the same speed as it is added to the spray gun 100 via the inlet (not show) - it drops like a waterfall due to gravity. Figure 4b illustrates how the compressed air (illustrated with arrows) lifts the unhardened plaster material 200 and carries it forward. The angle between the direction of the airflows (the arrows) and the first outlet 103 is optimized, allowing the plaster material 200 to leave the outlet 103 at an optimal direction. Especially the second air nozzle 1 16 contributes to a lift (opposing gravity), while the first air nozzle 1 15 carries forward and/or accelerates the unhardened plaster material 200 in order for said unhardened plaster material to be distributed in the most homogenous manner on a surface.

References

100 Spray gun

101 Flousing

102 First inlet

103 First outlet

1 1 1 First air inlet 112 Second air inlet

113 First cavity

114 Second cavity

115 First air nozzle

116 Second air nozzle

200 Unhardened plaster material