WO2008030164A1

WO2008030164A1 - Screen and suction device

Info

Publication number: WO2008030164A1
Application number: PCT/SE2007/000774
Authority: WO
Inventors: Eiwe Wihk
Original assignee: F P D Scandinavia Ab
Priority date: 2006-09-08
Filing date: 2007-09-05
Publication date: 2008-03-13
Also published as: SE530297C2; SE0601843L

Abstract

A screen and suction device for sucking up liquid from a liquid pool, arranged to be driven by a liquid pump. According to the invention, the device comprises a floating body (1) having a first, horizontal wall (2) and a first end wall (6), and an internal air-filled space (8), a screen element (15) and a suction nozzle (25) arranged in said space and rigidly connected to the first wall adjacent to an aperture (10), said suction nozzle including a suction cup (26) with a suction chamber (32), an inlet opening (33) and an outlet opening (31), said suction cup including a first wall portion (29) facing towards the screen element, and a second downstream wall portion (30), and an outlet pipe (28) communicating with the suction chamber via the outlet opening. The first wall portion is inclined in the flow direction so that the distance between the screen element and the inclined wall portion increases in a direction towards the second wall portion, and the suction cup is designed so that the cross-sectional area of the suction chamber increases in the same direction, whereby the largest cross-sectional area is larger than the cross-sectional area of the outlet pipe. Furthermore, the outlet pipe is obliquely aligned to the screen element. The invention also relates to such a suction nozzle.

Description

Screen and suction device

The present invention relates to a screen and suction device for sucking up liquid from a liquid pool, said screen and suction device is kept floating on the surface of the liquid pool, and is arranged to be driven by a liquid pump.

The invention also relates to a suction nozzle for such a screen and suction device.

A screen and suction device according to the invention is a pump accessory, which particularly intends to meet the need for additional accessories to the regular equipment being used by the rescue services in connection with disasters such as forest fires, floods, e.g. flooding in basements, etc.

The object of the present invention is to achieve a reliable and efficient screen and suction device for connection to a liquid pump.

The screen and suction device according to the invention is characterized in that it comprises: a floating body being formed by walls comprising a first, horizontal wall and a first end wall and defining an internal space with a gas-filled volume, an opening being arranged within the central portion of the first, horizontal wall; a screen element arranged to cover said opening completely and having flow apertures with a predetermined total area; and a suction nozzle having a vertical centre plane Ci-Ci coinciding with the vertical centre plane C-C of the screen and suction device, and being arranged in said space and rigidly connected to the first horizontal wall adjacent to its opening, said suction nozzle including: a suction cup having a suction chamber, an inlet opening and an outlet opening, said inlet opening facing towards and being in direct communication with the flow apertures of the screen element, said suction cup including a first wall portion, facing towards the screen element, and a second downstream wall portion having said outlet opening, and an outlet pipe extending from the second downstream wall portion to the outside of the floating body, and communicating with the suction chamber via said outlet opening in the second wall portion, that the first wall portion is inclined in the flow direction in a direction away from the screen element so that the distance between the screen element and the inclined wall portion increases in a direction towards the second wall portion, and the suction cup is designed so that the cross-sectional area of the suction chamber increases in a direction towards the second wall portion, whereby the largest cross-sectional area is larger than the cross-sectional area of the outlet pipe, and that the outlet pipe is obliquely aligned to the screen element.

The screen and suction device according to the invention is thus designed so that an optimum flow of liquid through its suction chamber is obtained owing to the fact that no detrimental turbulence arises in the suction chamber and the walls of the suction chamber resist the forces created by the negative pressure prevailing in the suction chamber even at maximum power, in order to thereby avoid leakage in the suction chamber, which otherwise might result in a negative pressure in the floating body itself, which thereby might be deformed and/or filled with water. Since no detrimental turbulence arises in the suction chamber, the floating body will float calmly in the water pool, i.e. without being jerked in different directions in a turbulent way as a result of the shocking effects which are created by more or less strong turbulences inside the suction chamber.

The invention is described in detail in the following with reference to the drawings, wherein:

Figure 1 is a perspective view of a screen and suction device according to the invention;

Figure 2 shows the device according to Figure 1 from the first side of its two major sides, facing away from each other;

Figure 3 shows the device according to Figure 1 from the other side of its two major sides;

Figure 4 is a view from one end of the device;

Figure 5 is a view from the other end of the device;

Figure 6 is a view from the first longitudinal side of the device, wherein a view from the other longitudinal side, which is not shown, is a mirror view of the first one .

Figure 7 is a longitudinal cross-sectional view of the device according to the line A-A in Figure 2 showing the hollow floating body of the device and two nozzles with different dimensions;

Figure 8 is a perspective view of the first nozzle of the device according to Figure 7;

Figures 9, 10 and 11 show the nozzle according to Figure 8 in plan views from different directions; Figure 12 is a perspective view of the second nozzle of the device according to Figure 7; and

Figure 13 shows the nozzle according to Figure 12 in a plan view from its pipe end.

The expressions "horizontal" and "vertical" relate to the position which the screen and suction device assumes when it is placed on a horizontal surface, e.g. is floating on a water surface without being influenced by any external forces .

A preferred embodiment of a combined screen and suction device according to the invention is shown in

Figures 1-7. The screen and suction device comprises a rigid, hermetically sealed floating body 1 of a suitable plastic material, such as for example polyester, vinyl ester or different types of thermoplastic.

The floating body 1 has a first horizontal wall 2, a second horizontal wall 3, two side walls 4, 5, a first end wall 6 and a second end wall 7. All adjoining walls 2-7 connect into each other via curved wall portions, whereby the floating body 1 thus lacks any sharp edges along its sides. The floating body 1 is symmetrical about a vertical centre plane C-C, which intersects the end walls 6, 7 and to which the side walls are parallel. The six walls 2-7 define an internal space 8, including a gas-filled, usually air-filled volume. The first end wall 6 has a central wall portion βa, which is recessed in order to form an easily accessible connection space 9 outside itself, when a hose is to be coupled to the screen and suction device by means of a coupling device of a predetermined dimension. The recessed wall portion 6a is provided with a central, circular aperture 10 of a predetermined diameter. In the embodiment shown, also the second end wall 7 has a similar central wall portion 7a, which is recessed in order to form an easily accessible connection space 11 outside itself, when a hose is to be coupled to the screen and suction device, by means of a coupling device of a predetermined dimension being different from the dimension of the first coupling device. The recessed wall portion 7a of the second end wall 7 is also provided with a central, circular aperture 12 of a predetermined diameter being different from the diameter of the aperture 10 in the first-mentioned wall portion βa . Furthermore, a handle 13, 14 is formed in the middle of each side wall 4, 5 in order to facilitate the handling of the screen and suction device, for example when it is to be carried from one location to another. The first, horizontal wall 2 has a central, recessed wall portion 2a extending between the end walls 6, 7 while forming two outer wall portions 2b, 2c, which can be compared to runners and which are intended to have a supporting action towards a bottom surface of a water pool in order to maintain good suction effect also in low water pools. In the embodiment shown, the wall portion 2a is recessed 12 mm. In general, this recess can be within the interval from 5 to 20 mm, preferably from 10 to 15 mm. Since the screen plate 15 with its inlet, formed by the holes 16, is located in the recessed wall portion 2a, and the recess creates a space 47 which is open to the sides in both directions, it is possible to suck water from a water pool which is very shallow, such as 15 mm deep, when the recess is 12 mm.

In manufacturing the floating body, an aperture 14 is formed in the recessed wall portion 2a of the first horizontal wall, said aperture 14 having the shape of a segment of an oval, the major portion of the aperture being located within the farther half of the recessed wall portion 2a in relation to the first end wall 6a, and the curvature of the oval segment being facing away from the first end wall. A screen plate 15 is mounted on the first wall 2 to cover the aperture 14 completely. The screen plate 15 also has the shape of a segment of an oval, but consequently has a slightly larger area than the aperture 14, so that the screen plate 15 exhibits continuous edge portions 15a, which are connected to the first wall 2 around its aperture 14 in order to form a stable connection. The screen plate 15 is provided with a plurality of small, uniform, circular holes 16 of a predetermined diameter. Together, the holes 16 provide a predetermined flow area. The screen plate 15 has a curvature 17, the ends of which being connected by a straight edge 18, that is perpendicular to said centre plane C-C, and that is located within the front half of the recessed wall portion 2a in relation to the first end wall 6a. In the preferred embodiment shown, also the second horizontal wall 3 is provided with a similar screen plate 19, that in the same way covers a similar aperture 20 in the wall 3 completely, and that is provided with a plurality of small, uniform, circular holes 21 of a predetermined diameter. Taken together, the holes provide a predetermined flow area. The screen plate 19 has a curvature 22, the ends of which being connected by a straight edge 23 that is perpendicular to said centre plane C-C.

Inside the floating body 1, on the inside of the first horizontal wall 2, there is an elongate, first suction nozzle 25, that is symmetrical about a vertical centre plane Ci-Ci coinciding with the vertical centre plane C-C of the floating body 1. The suction nozzle 25 comprises a suction cup 26, a mounting flange 27 and an outlet pipe 28. The suction cup 26 has a curved wall portion 29 and a wall portion 30 that is transverse to the centre plane Ci-C₁, and located downstream and connects to the curved wall portion 29. A central outlet opening 31 is formed in the transverse wall portion 30. The suction cup 26 defines a suction chamber 32 that comprises an inlet opening 33 having a curvature 34 in the form of a segment of an oval, and a straight portion that connects the ends of the curvature to each other. The mounting flange 27 has a planar shape and is arranged to surround said inlet opening 33 in that it extends around and horizontally outwards from the upper portion of the suction cup 26 in connection to the delimiting curvature 34 and straight portion 39 of the inlet opening 33. The suction nozzle 25 is arranged to be mounted with its planar mounting flange 27 onto the underside of the first, horizontal wall 2 with the aid of a suitable glue for obtaining a stable joint. By means of this attachment, the inlet opening 33 of the suction cup 26 will be aligned towards the aperture 14 of the wall 2 and the screen plate 15 in order to communicate with all holes 16 in the screen plate 15. The outlet pipe 28 is connected to the straight wall portion 30 of the suction cup 26 in connection to its central outlet opening 31 in order to communicate directly with the outside of the floating body 1 via the suction chamber 32 and the flow holes 16 of the suction plate 15. The outlet pipe 28 extends outwards from the suction cup 26 in a direction towards the recessed wall portion 6a of the first, horizontal wall 2. The outlet pipe 28 has an inner pipe portion 35, that is located closest to the suction cup 26, and an outer pipe portion 36, that extends outwards through said aperture 10 in the recessed wall portion 6a into the connection space 9, where the outer end of the outlet pipe 28 is provided with a predetermined coupling device 37 for receiving the coupling device (not shown) of the hose in question. While the outer pipe portion 36 extends horizontally and thus in parallel with the first, horizontal wall 2, the inner pipe portion 35 extends obliquely upwards from a first point, located at a distance from the first wall 2, to a second point, located in the immediate vicinity of this wall 2, so that the centre line of the inner pipe portion 35, in its extension, intersects the screen plate 15 at an acute angle α. In the embodiment shown, this angle a is 22°. In general, this angle α can be within the range of from 15° to 40°, preferably within the range of from 20° to 30°. The inner pipe portion 35 approaches the transverse wall portion 30 with a cross-sectional area form-changing from a circular to a horizontal, oval cross-sectional area with an increasing ovality all the way to the outlet opening which has the same shape and area as the nearest cross-sectional area of the outlet pipe. Accordingly, the big axis of the oval is horizontal and the small axis is vertical. Owing to the laterally widening shape of the outlet pipe 28, the through-flow of liquid through the suction chamber, from those holes 16 in the screen plate 15 that are located at its outer portions at a distance from the centre plane C-C to the oval outlet opening, is facilitated.

The largest cross-section of the suction chamber 32 of the suction cup, i.e. transversely to the centre plane Ci-C₁, is located close to the straight wall portion 30. The cross-sectional area is a circle segment of varying size in that it decreases continuously from the straight wall portion 30 in a direction towards the opposite end 38 of the suction cup 26, where the cross-sectional area heads towards zero.

The suction cup 26, the mounting flange 27 and the outlet pipe 28 are made in one piece, so that no joints which could be broken by external forces are present therebetween. Since the major portion of the suction cup 26 is formed by the curved wall portion 29, the suction cup 26 will, owing to the curved shape, efficiently resist large pressure differences between the outside and the inside of the curved wall portion 29.

In the embodiment shown, a similar elongate, second suction nozzle 40 is also arranged at the inside of the second horizontal wall 3. This second nozzle 40 has a slightly smaller dimension than the initially described nozzle 25, but is otherwise designed in the same way. The nozzle 40 has a smaller coupling device 41 on the outer end of its outlet pipe 42. Thereby, the nozzle 40 is intended to be utilized for a pump of a lower capacity than the pump which is connected to the initially described nozzle 25.

After having connected a pump to its associated nozzle 25; 40, the floating body 1 is placed in a water pool with the side having the screen plate 15; 19 belonging to the connected nozzle 25; 40 facing downwards. When connecting the pump, a negative pressure is created in the suction chamber 32; 44, whereby water is sucked in through the screen plate 15; 19, and the floating body is sucked or pulled down a small distance below the water surface so that the screen plate 15; 19 is kept below the water surface all the time so that air penetration is avoided. Furthermore, the floating body 1 becomes less sensitive to waves. Owing to the fact that the suction cup 26; 45 has a curved wall portion right in front of the suction plate 15; 19 and that its outlet pipe 28; 42 is aligned towards the area of the screen plate 15; 19 provided with holes, as seen in a projection, no detrimental turbulence arises which can cause shocks or jerks in the floating body 1, and instead an optimum flow of liquid through the suction chamber 32; 42 and the outlet pipe 28; 43 is obtained. Accordingly, water is sucked in through the screen plate 15; 19 and flows the closest way through the suction chamber 32; 44 and out through the outlet pipe 28; 43 without being forced against any turbulence-generating planar surfaces being located right in front of the screen plate 15; 19. Furthermore, the curved wall portion 29; 46 provides a larger resistance against the negative pressure prevailing in the suction chamber is obtained also at maximum pump power than what is the case with planar walls of a box-shaped suction cup. In this way, leakage in the suction chamber 32; 44 with accompanying deformation and water-filling of the floating body 1 itself is avoided.

The unique design of the suction nozzles according to the invention contributes to an efficient screen and suction device that is safe to operate, where the specific part of the design lies, firstly, in the connection of the outlet pipe to the suction chamber so that the outlet pipe becomes obliquely aligned to the screen plate, and, secondly, in the first wall portion of the suction chamber, facing towards the screen plate, is inclined in the flow direction so that the distance between the screen plate and the inclined wall portion increases in a direction towards the outlet, and that the remainder of the suction cup, i.e. its side walls, is designed so that the cross-sectional area of the suction chamber increases in a direction towards the outlet. In this way, an optimum through-flow of water through the suction chamber is obtained in that the emergence of such turbulences in the suction chamber which detrimentally influence the through-flow of water from the screen plate to the outlet and which also can cause irregular jerks in the screen and suction device, that thereby acts irregularly on the water surface, are eliminated. The same negative pressure prevails in the entire suction chamber and the risk of sucking in the walls with accompanying leakage is eliminated. Such a leakage can result in the floating body being destroyed so that the entire screen and suction device has to be discarded. Furthermore, the oblique alignment of the outlet pipe means that the water to a large extent will flow obliquely inwards towards the screen plate on its outside, which implies that an advantageous tractive force is produced in the screen and suction device so that it has a tendency to be pulled in a direction from the end where the pump hose is connected to the screen and suction device. In this way the hose will be stretched out so that loops, twists, folds, and the like disappear without any manual work, which in its turn facilitates and speeds up a rescue and fire-fighting operation .

The screen and suction device according to the invention is manufactured with advantage by means of so-called vacuum injection of the plastic material into two moulds for the floating body and one mould with two mould halves for each suction nozzle. The obtained joint faces are coated with glue. The joint faces are then brought together in order to obtain strong, permanent glue joints, which are not destroyed at the prevailing pressures. Thus, the nozzle is made in a single, integral piece by moulding and gluing. Vacuum injection enables the screen and suction device to obtain a desired low weight. A screen and suction device according to the invention, which has been produced by means of vacuum injection with the required thickness of material with the dimensions length 810 mm, width 600 mm and height 258 mm has a weight of about 10 kg. In the described embodiment, the thickness of material of the floating body is 3 mm, except in the wall portions comprising glue joints, where the thickness is 9 mm, whereas the thickness of material of the suction nozzles is 4 mm.

The screen and suction devices according to the invention are designed to fit to the pump systems which are available on the market. Thus, there are classified pumps, wherein the classes are classified according to the Swedish Standard SS 3496 as follows:

Class I, 400 liters/minute and 6 bars

Class II, 1200 liters/minute and 10 bars

Class III, 2400 liters/minute and 10 bars

The screen and suction device, having e.g. twin suction nozzles according to the invention, is equipped with replaceable coupling devices fitting to the coupling devices of the hoses of these different pumps, and it can also be equipped with coupling devices suited to individual needs .

A screen and suction device according to the invention, which is suited to the requirements of the rescue services, has a floating body with an internal free volume of about 135 liters, while the largest nozzle has a suction chamber which is about 3 liters and the smallest nozzle has a suction chamber which is about 2 liters, resulting in a volume ratio of 67.5 and 45, respectively.

The screen and suction device according to the invention can be utilized in most situations, where there is a need of water for fire fighting, such as forest fires, and where some kind of water pool is available, such as lakes, rivers and smaller watercourses as well as bogs and swamps . The screen and suction device according to the invention enables utilization of water from relatively shallow water pools, which e.g. ensue from the fire fighting operation itself and which previously have not been possible to utilize for the ongoing fire fighting operation. Floating debris and muddy bottoms cause no problem for the screen and suction device, thanks to its design. The screen and suction device is also useful for evacuating water that has penetrated into spaces such as premises, basements, etc., in connection with precipitation.

The suction nozzle has been shown and described with reference to a preferred embodiment. For the same or other applications than the one mentioned above, the suction cup can of course be designed in many different ways within the scope of the claims. The cross-section of the suction cup, and thereby of the suction chamber, can have a rectangular shape, the area of which increases towards the outlet. In this case, said inclined wall portion can be straight or curved, as seen in a longitudinal cross-section, and the two side walls can be straight and parallel to each other or angled in relation to each other. They can also be curved. Conveniently, the transitions between adjacent wall portions are curved in order to avoid sharp corners and thus increase the strength of the suction cup at prevailing pressure differences. Even if the cross-section of the suction cup is curved, as shown, the inclined wall portion can be straight, as seen in a longitudinal cross-section.

Claims

C L A I M S

1. A screen and suction device for sucking up liquid from a liquid pool, said screen and suction device is kept floating on the surface of the liquid pool, and is arranged to be driven by a liquid pump, characterized in that it comprises:

- a floating body (1) being formed by walls (1-7) comprising a first, horizontal wall (2) and a first end wall (6) and defining an internal space (8) with a gas-filled volume, an aperture (10) being arranged within the central portion of the first, horizontal wall (2);

- a screen element (15) arranged to cover said aperture (10) completely and having flow holes (16) with a predetermined total area; and

- a suction nozzle (25) having a vertical centre plane C_I-C_I coinciding with the vertical centre plane C-C of the screen and suction device, and being arranged in said space (8) and rigidly connected to the first horizontal wall (2) adjacent to its aperture (10), said suction nozzle including:

- a suction cup (26) having a suction chamber (32), an inlet opening (33) and an outlet opening (31), said inlet opening (33) facing towards and being in direct communication with the flow holes (16) of the screen element (15), said suction cup (26) including a first wall portion (29), facing towards the screen element (15), and a second downstream wall portion (30) having said outlet opening (31), and - an outlet pipe (28) extending from the second downstream wall portion (30) to the outside of the floating body (1), and communicating with the suction chamber (32) via said outlet opening (31) in the second wall portion (30) ,

that the first wall portion (29) is inclined in the flow direction in a direction away from the screen element (15) so that the distance between the screen element (15) and the inclined wall portion (29) increases in a direction towards the second wall portion (30), and the suction cup (26) is designed so that the cross-sectional area of the suction chamber (32) increases in a direction towards the second wall portion (30), whereby the largest cross-sectional area is larger than the cross-sectional area of the outlet pipe (28), and that the outlet pipe (28) is obliquely aligned to the screen element (15) .

2. A screen and suction device according to claim 1, characterized in that the suction cup (26) includes two side wall portions defining a major portion of the inlet opening (33) of the suction cup (26) and being connected to the first and second wall portions (29, 30), said second wall portion (30) defining the remaining portion of said inlet opening (33) .

3. A screen and suction device according to claim 1 or 2, characterized in that the centre line of the outlet pipe (28) forms an acute angle α with the screen element ( 15) .

4. A screen and suction device according to claim 3, characterized in that said angle α is within the range of 15°-40°, preferably within the range of 20°-30°.

5. A screen and suction device according to any one of claims 1-4, characterized in that the first wall portion (29) is curved as seen in a vertical section located in said centre plane Ci-Ci and in each vertical section parallel to this plane.

6. A screen and suction device according to any one of claims 1-5, characterized in that the first wall portion (29) is curved, as seen in each vertical cross-section intersecting said centre plane Ci-C₁ at right angles .

7. A screen and suction device according to claim 6, characterized in that said cross-section has the shape of a segment of a circle or an oval.

8. A screen and suction device according to any one of claims 1-7, characterized in that said outlet opening (31) is arranged in the immediate vicinity of the screen element (15) .

9. A screen and suction device according to any one of claims 1-8, characterized in that the outlet pipe (28) includes an inner pipe portion (35) aligned towards the screen element (15) and located closest to the suction cup (26) , and an outer, horizontal pipe portion (36) which connects to the inner pipe portion (35) at an obtuse angle.

10. A screen and suction device according to any one of claims 1-9, characterized in that the total area of the flow holes (16) is equal to or substantially equal to the cross-sectional area of the outlet pipe (28).

11. A screen and suction device according to any one of claims 1-10, characterized in that the flow holes (16) are circular with a diameter within the range of 6-10 mm, preferably 8 mm.

12. A screen and suction device according to any one of claims 1-11, characterized in that the outlet pipe (28) is provided with a coupling member (37) for coupling to a corresponding coupling member of a hose being connected to said liquid pump.

13. A screen and suction device according to any one of claims 1-12, characterized in that said first end wall (6) includes a central, recessed wall portion (6a), arranged to define a protected space (9) for said coupling member (37) and through which the outlet pipe (28) extends.

14. A screen and suction device according to claim 1, characterized in that the walls (1-7) of the floating body include a similar second, horizontal wall (3) and a second end wall (7), that a similar second nozzle (40) is arranged in said space (8) and rigidly connected to the second horizontal wall (3) adjacent to its opening, and that the suction chambers of the two suction nozzles have different volumes.

15. A suction nozzle suitable for a screen and suction device for sucking up liquid from a liquid pool, said screen and suction device is kept floating on the surface of the pool, and is arranged to be driven by a liquid pump, said screen and suction device comprising a floating body (1) being formed by walls (1-7) including a first, horizontal wall (2) and a first end wall (6) and defining an internal space (8) with a gas-filled volume, an aperture (10) being arranged within the central portion of the first, horizontal wall (2), and a screen element (15) arranged to cover said aperture (10) completely and having flow holes (16) with a predetermined total area, characterized in

that the suction nozzle (25) , which has a vertical centre plane Ci-Ci coinciding with the vertical centre plane C-C of the screen and suction device, is arranged in said space (8) and rigidly connected to the first horizontal wall (2) adjacent to its aperture (10), and

that the suction nozzle includes a suction cup (26) having a suction chamber (32), an inlet opening (33) and an outlet opening (31) , said inlet opening (33) facing towards and being in direct communication with the flow holes (16) of the screen element (15), said suction cup (26) including a first wall portion (29) , facing towards the screen element (15), and a second downstream wall portion (30) having said outlet opening (31), and

- an outlet pipe (28) extending from the second downstream wall portion (30) to the outside of the floating body (1), and communicating with the suction chamber (32) via said outlet opening (31) in the second wall portion (30),

that the first wall portion (29) is inclined in the flow direction in a direction away from the screen element (15) so that the distance between the screen element (15) and the inclined wall portion (29) increases in a direction towards the second wall portion (30) , and the suction cup (26) is designed so that the cross-sectional area of the suction chamber (32) increases in a direction towards the second wall portion (30), whereby the largest cross-sectional area is larger than the cross-sectional area of the outlet pipe (28), and that the outlet pipe (28) is obliquely aligned to the screen element (15) .

16. A suction nozzle according to claim 15, characterized in that the suction cup (26) includes two side wall portions defining a major portion of the inlet opening (33) of the suction cup (26) and being connected to the first and second wall portions (29, 30), said second wall portion (30) defining the remaining portion of said inlet opening (33) .

17. A suction nozzle according to claim 15 or 16, characterized in that the centre line of the outlet pipe (28) forms an acute angle α with the screen element ( 15 ) .

18. A suction nozzle according to claim 17, characterized in that said angle α is within the range of 15°-40°, preferably within the range of 20°-30°.

19. A suction nozzle according to any one of claims 15-18, characterized in that the first wall portion (29) is curved as seen in a vertical section located in said centre plane C₁-Ci and in each vertical section parallel to this plane.

20. A suction nozzle according to any one of claims 15-19, characterized in that the first wall portion (29) is curved, as seen in each vertical cross-section intersecting said centre plane C₁-C_x at right angles.

21. A suction nozzle according to claim 20, characterized in that said cross-section has the shape of a segment of a circle or an oval.

22. A suction nozzle according to any one of claims 15-21, characterized in that said outlet opening (31) is arranged in the immediate vicinity of the screen element (15) .

23. A suction nozzle according to any one of claims 15-22, characterized in that the outlet pipe (28) includes an inner pipe portion (35) aligned towards the screen element (15) and located closest to the suction cup (26) , and an outer, horizontal pipe portion (36) which connects to the inner pipe portion (35) at an obtuse angle.

24. A suction nozzle according to any one of claims 15-23, characterized in that the total area of the flow holes (16) is equal to or substantially equal to the cross-sectional area of the outlet pipe (28).

25. A suction nozzle according to any one of claims 15-24, characterized in that the flow holes (16) are circular with a diameter within the range of 6-10 mm, preferably 8 mm.

26. A suction nozzle according to any one of claims 15-25, characterized in that the outlet pipe (28) is provided with a coupling member (37) for coupling to a corresponding coupling member of a hose being connected to said liquid pump.