WO2011154471A1

WO2011154471A1 - A dishwasher

Info

Publication number: WO2011154471A1
Application number: PCT/EP2011/059548
Authority: WO
Inventors: Niklas Olson; Jason Duckworth
Original assignee: Aktiebolaget Electrolux
Priority date: 2010-06-10
Filing date: 2011-06-09
Publication date: 2011-12-15

Abstract

There is provided a dishwasher comprising a pump for imparting to a liquid pressure to thereby generate liquid under pressure, a compartment, and at least one spray arm 20 extending in a direction of an arm axis A. The spray arm 20 is rotatable by means of the liquid under pressure and is provided with a nozzle 36 for distributing, at least partially, the liquid in the compartment, and a control opening 34 for interaction with the nozzle 36. The spray arm 20 comprises a fixed tube 30 extending in a direction of the arm axis A and a movable tube 32. One of the fixed and movable tubes is provided with the nozzle and an other of the fixed and movable tubes is provided with the control opening. The fixed and movable tubes are arranged one at least partially within the other. The dishwasher comprises a driving arrangement for rotating the movable tube substantially around the arm axis A to cause the control opening 34 to interact with the nozzle 36, and the driving arrangement is driven by means of the liquid under pressure.

Description

A DISHWASHER

TECHNICAL FIELD

The present invention relates to a dishwasher according to the precharacterizing portion of claim 1.

BACKGROUND

A dishwasher, in particular for kitchenware such as plates, pots, pans, cutlery etc., commonly comprises a compartment in which the kitchenware to be cleaned is placed, one or more rotating spray arms, or rotors, provided with nozzles for spraying liquid inside the compartment onto the kitchenware, and a pump for creating a liquid pressure in the liquid to spray it through the nozzles. The liquid in the dishwasher is commonly water and/or a mix of water and a washing agent. It is desired that the liquid is distributed so as to reach as many positions as possible at which kitchenware is arranged inside the compartment of a dishwasher. This requires a large number of nozzles, which nozzles may be arranged on one or more of the rotors but which also may be fixedly arranged at other parts of the dishwasher inside its compartment. The desire to reach as many positions as possible is in contrast with the available amount of liquid in a dishwasher and with the desire to use a reasonably sized pump in the dishwasher. In the prior art there are several solutions to this problem.

US2003/0168087 discloses a dishwasher having several rotors with nozzles and/or fixed nozzles, wherein a so-called aqueduct with a rotating dividing unit provided with discharge ports distributes cleaning liquid to only some of the rotors and fixed nozzles at a time.

DE10205008 discloses a dishwasher with a rotor provided with open nozzles and nozzles of a second type. The nozzles of the second type are manipulated by a slidable element to adjust the size of, and to close, these nozzles. The slidable element may be manually or automatically actuated. GB2199734 discloses in Fig. 4 an embodiment of a dishwasher with a rotary spray arm provided with nozzles on its upper side and its lower side. Inside the spray arm there is a slider which is manually manipulated in a longitudinal direction of the spray arm. In one position of the slider the upper nozzles are open and the lower nozzles are closed, and in a different position of the slider the upper nozzles are closed and the lower nozzles are open.

In the prior art there are thus disclosed different ways of using only a selected number of nozzles out of a plurality of nozzles in a dishwasher. There is however still a need for an improved arrangement for distributing liquid evenly and efficiently in at least part of an interior of a dishwasher to clean kitchenware therein.

SUMMARY

An object of the present invention is to provide a dishwasher with a spray arm from which a liquid is automatically distributed evenly over at least part of a compartment inside the dishwasher, and wherein the spray arm has a similar requirement on liquid supply capacity from a pump of the dishwasher as a comparable contemporary simple spray arm. According to an aspect of the invention, the object is achieved by a dishwasher comprising a pump for imparting to a liquid pressure to thereby generate liquid under pressure, a compartment, and at least one spray arm extending in a direction of an arm axis. The spray arm is rotatable by means of the liquid under pressure and is provided with a nozzle for distributing the liquid in the compartment, and a control opening for interaction with the nozzle. The spray arm comprises a fixed tube extending substantially in a direction of the arm axis and a movable tube. One of the fixed and movable tubes is provided with the nozzle and an other of the fixed and movable tubes is provided with the control opening. The fixed and movable tubes are arranged one at least partially within the other to allow the said interaction between the control opening and the nozzle. The dishwasher comprises a driving arrangement for rotating the movable tube substantially around the arm axis to cause the control opening to interact with the nozzle, and wherein the driving arrangement is driven by means of the liquid under pressure. Since the driving arrangement, due to the utilisation of the liquid under pressure, automatically causes an interaction between the nozzle and the control opening, basis is provided for the liquid to be distributed evenly over at least part of the compartment of the dishwasher. Since no more nozzles than normal are required, and/or are not open at the same time, the liquid consumption of the spray arm is the same as of a dishwasher with a spray arm with an uncontrolled, permanently open, nozzle of comparable size. The pump of the dishwasher does not therefore need to have any extraordinary capacity. As a result, the above mentioned object is achieved and conditions for a good dishwashing result are provided at normal pump capacity.

A dishwasher of this kind may be provided with one or more baskets for receiving dishes, in the form of kitchenware such as plates, pots, pans, and cutlery, to be cleaned. The one or more baskets are suitably arranged to slide in and out of the compartment of the dishwasher. The liquid used in the dishwasher may suitably be water or water with a suitable detergent added. The liquid is commonly circulated in the dishwasher during various stages of dishwashing, from the pump through the spray arm and at least one nozzle therein onto the dishes in the compartment and back again to the pump. The spray arm may be provided with several interacting control openings and nozzles. The fixed tube is fixed in relation to the spray arm, which in turn is rotatable inside the compartment. At least one of the fixed and movable tubes is a closed tube with the exception of various liquid dispensing outlets such as the control opening, the nozzle or other types of nozzles. The other tube may be of a more open structure with a function of providing the control openings, alternatively the nozzles.

According to example embodiments the movable tube may extend substantially in the direction of the arm axis and substantially concentrically with the fixed tube. In this manner the movable tube may easily rotate inside or outside the fixed tube and the control openings may thus interact with the nozzles.

According to example embodiments the driving arrangement may comprise a stationary engaging part being stationary in relation to the compartment and a rotating engaging part connected to the movable tube. The stationary engaging part is engaged with the rotating engaging part. The stationary and rotating engaging parts may thus engage to achieve the rotation of the movable tube as the spray arm rotates.

According to example embodiments the stationary engaging part may comprise a first cogwheel and the rotating engaging part comprise a second cogwheel, the first and second cogwheels being engaged with each other. Alternatively, the stationary engaging part and the rotating engaging part may be frictionally engaged with each other.

According to example embodiments the stationary engaging part may have a circular engaging distance and the rotating engaging part may have a peripheral engaging length. The circular engaging distance may be different than any multiple of the peripheral engaging length. In this manner the movable tube will have a different position in relation to the fixed tube for at least two consecutive rotations of the spray arm.

Accordingly, the liquid will be distributed differently in the compartment for the two consecutive turns of the spray arm and an even distribution of the liquid is achieved.

According to example embodiments the control opening and the movable tube may be arranged to open and close the nozzle. According to example embodiments the spray arm may comprise a drive outlet at an outer end of the spray arm, the spray arm being rotatable by means of the liquid under pressure exiting the drive outlet. In this manner the rotation of the spray arm as well as the rotation of the movable tube may be achieved by means of the liquid under pressure. According to example embodiments the nozzle may be arranged in the movable tube and the control opening may be arranged in the fixed tube. In this manner the liquid may be ejected through the nozzle and distributed in the compartment while the nozzle is located in line with the control opening during a rotation of the movable tube around the arm axis. Similarly, the nozzle will be closed while the nozzle is not located in line with the control opening during the rotation of the movable tube. While the nozzle is closed, the liquid is available for distribution trough a different nozzle.

According to example embodiments the control opening may be larger than the nozzle for defining a spraying angle of the nozzle over which the liquid is adapted to be ejected through the nozzle as said movable tube rotates in relation to said fixed tube. In this manner liquid is ejected through the nozzle over the spraying angle defined by a sector, which corresponds to a peripheral length of the control opening, as the movable tube is rotated in relation to the fixed tube.

According to example embodiments the movable tube or the fixed tube may be provided with two or more nozzles interacting with one and the same control opening, and wherein the two or more nozzles are arranged in the same longitudinal position along the arm axis at different peripheral positions of the movable tube or the fixed tube. In this manner liquid may be ejected into the compartment more than one time through one control opening during one rotation of the movable tube.

According to example embodiments the movable tube may be arranged inside the fixed tube. Alternatively the movable tube is arranged outside said fixed tube.

According to example embodiments the nozzle may be arranged in the fixed tube and the control opening may arranged in the movable tube. In this manner the liquid may be ejected through the nozzle while the control opening is located in line with the nozzle during a rotation of the movable tube around the arm axis. Similarly, the nozzle will be closed while the control opening is not located in line with the nozzle during the rotation of the movable tube. While the nozzle is closed, the liquid may be available for distribution trough a different nozzle, which may be directed in a different direction than the closed nozzle. According to example embodiments where the movable tube is arranged inside the fixed tube, the dishwasher may comprise a fixed conduit arranged in the compartment and leading from the pump to the rotating spray arm. One rotational sealing may be arranged between the fixed conduit and the spray arm. The one rotational sealing is the only rotational sealing used in an assembly comprising the fixed conduit, the spray arm, the fixed tube and the movable tube. In this manner only one rotational sealing is required to seal the spray arm and its parts even tough there are at least two movable part, namely the spray arm itself and the movable tube of the spray arm. Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. Those skilled in the art will realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention, as defined by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The various aspects of the invention, including its particular features and advantages, will be readily understood from the following detailed description and the accompanying drawings, in which:

Fig. 1 illustrates a dishwasher according to example embodiments,

Fig. 2 illustrates a top view of a portion of a spray arm according to example

embodiments,

Fig. 3 illustrates a cross sectional side view of the portion of the spray arm illustrated in Fig. 2,

Fig. 4 illustrates a cross sectional side view of a driving arrangement of a spray arm according to example embodiments,

Figs. 5 and 6 schematically illustrate cross sectional side views of a central part and an outer part of a rotatable spray arm according to example embodiments, and

Fig. 7 illustrates a cross sectional side view of an inner part of a rotatable spray arm according to example embodiments.

DETAILED DESCRIPTION

The present invention will now be described more fully with reference to the

accompanying drawings, in which example embodiments are shown. However, this invention should not be construed as limited to the embodiments set forth herein.

Disclosed features of example embodiments may be combined as readily understood by one of ordinary skill in the art to which this invention belongs. Like numbers refer to like elements throughout.

Well-known functions or constructions will not necessarily be described in detail for brevity and/or clarity. Fig. 1 illustrates a dishwasher 10 according to example embodiments. The dishwasher 10 comprises a housing 15 with a front door 14. Inside the housing 15 there is a compartment 11 in which two baskets 12, 13 for receiving dishes to be cleaned are arranged. The baskets 12, 13 can be pulled out of the compartment 1 1 for easy filling and emptying. Inside the compartment 1 1 , beneath each of the baskets 12, 13 there is arranged one spray arm 20. According to alternative embodiments, the number of baskets and spray arms may be different than two. At least one of the spray arms 20 is provided with an arrangement according to the present invention. Fig. 2 illustrates a top view of a portion of a spray arm 20 according to example embodiments. The spray arm 20 is illustrated in a state separate from a dishwasher. A central opening 22 is an inlet for a liquid, such as water, used in the dishwasher. A peripheral portion 24 around the opening 22 acts as a bearing for rotatably supporting the spray arm 20 in the dishwasher. The liquid is supplied to the spray arm 20 through conduits from a pump. The pump imparts to the liquid a pressure such that the liquid is supplied as a liquid under pressure to the spray arm 20. Suitably the spray arm 20 may be symmetrical about the central opening 22, i.e. comprising two essentially identical portions as illustrated in Fig. 1. At an outer end 26 of the spray arm 20, it is provided with a drive outlet 28. The drive outlet 28 is in the form of a permanently open nozzle directed obliquely outwardly from the spray arm 20 such that the liquid under pressure being ejected through the drive outlet 28 causes the spray arm 20 to rotate. The liquid ejected through the drive outlet 28 may be utilized also for cleaning dishes arranged in a basket of the dishwasher.

The spray arm 20 comprises a fixed tube 30, i.e. it is fixed in relation to the spray arm 20, and a movable tube 32, which extends inside the fixed tube 30 and thus, is only partially visible in Fig. 2. Both the fixed and movable tubes 30, 32 extend in a direction of an arm axis A. The movable tube 32 is rotatable around the arm axis A. The fixed tube 30 is provided with control openings 34 in the form of slots. The movable tube 32 is provided with nozzles 36 in the form of round through holes. One nozzle 36 is arranged in the movable tube 32 for each control opening 34 in the fixed tube 30. The different nozzles 36 in the movable tube 32 are arranged at different circumferential positions around the circumference of the movable tube 32. Accordingly, as the movable tube 32 rotates inside the fixed tube 30, only some of the nozzles 36 will be open at a time since only some of the nozzles 36 will be positioned within the control openings 34 at a time. In Fig. 2, two nozzles 36 are open in the two left hand control openings 34. In the right hand control opening 34 no nozzle 36 is visible as the corresponding nozzle 36 has a different circumferential position than the corresponding control opening 34. Each nozzle 36 will eject liquid while it is open, i.e. while it is positioned within its control opening 34. Since the nozzles 36 rotate with the movable tube 32 and due to the control openings 34 having a larger circumferential extension than the nozzles 36, each nozzle 36 ejects liquid in a circle sector in relation to the fixed tube 30. The circle sector is defined by the size of the corresponding control opening 34, which thus defines a spraying angle of the nozzle 36. Two advantages with the arrangement of the movable tube 32, the nozzles 36, and the control openings 34 explained above are worth pointing out. Firstly, since not all nozzles 36 are open at the same time, the requirements on the pump of the dishwasher are limited, in particular in relation to the volumetric capacity of the pump. Secondly, due to the rotation of the nozzles 36 and their spraying angels, an even distribution of the liquid over the circle sector covered by the spraying angle is achieved and accordingly, only an even distribution over a part of the compartment inside the dishwasher. The liquid will thus reach the dishes to be cleaned from more different angels than if only fixed nozzles of the same size and number where provided on the spray arm. The conditions for achieving a good cleaning result are improved over a spry arm with fixed nozzles. This is achieved with a pump sized for the relevant number of open nozzles, which is the same number, or about the same number, as in a similarly sized spray arm with permanently open nozzles.

Fig. 3 illustrates a cross sectional side view of the portion of the spray arm 20 illustrated in Fig. 2. The fixed and movable tubes 30, 32 are concentric. The movable tube 32 is illustrated in a position where the right hand nozzle 36 is within its corresponding control opening 34 of the fixed tube 30, and thus, is open. The left hand nozzles 36 are closed since they are positioned in a different circumferential position than their corresponding control openings 34. Optionally, as illustrated in connection with the left hand control opening 34 and nozzles 36, the movable tube 32 may be provided with two or more nozzles 36 interacting with one and the same control opening 34. The two or more nozzles 36 are thus arranged in the same longitudinal position of the arm axis A at different peripheral positions.

Fig. 4 illustrates a cross sectional side view of a driving arrangement 40 of a spray arm 20 according to example embodiments. The spray arm 20 is rotatably attached to a fixed conduit 42 inside a not-shown compartment of a dishwasher. Liquid under pressure is lead through the fixed conduit 42 into the spray arm 20 to exit therefrom through not- shown nozzles etc. The liquid under pressure rotates the spray arm about an axis of rotation B in the same, or similar, manner as described in relation to Figs. 2 and 3.

The spray arm 20 comprises two fixed tubes 30 and two movable tubes 32. The movable tubes 32 are rotated about an arm axis A by means of the driving arrangement 40. The driving arrangement 40 comprises a stationary engaging part 44 connected to the fixed conduit 42 and a rotating engaging part 46 connected to each movable tube 32. The stationary engaging part 44 comprises a first cogwheel 48 and the rotating engaging parts 46 each comprises a second cogwheel 50. As the spray arm 20 rotates about the axis of rotation B, the spray arm 20 rotates in relation to the stationary engaging part 44. Since the stationary engaging part 44 and the rotating engaging parts 46 are engaged by means of the first and second cogwheels 48, 50, the rotating engaging parts 46, and accordingly also the movable tubes 32, will be rotated about the arm axis A. In order to arrange for not-shown nozzles in the movable tubes 32 to eject the liquid through not-shown control openings of the fixed tubes 30 at different positions in the compartment for each one of two consecutive rotations of the spray arm 20, the number of cogs on the stationary engaging part 44 is not an even multiple of the number of cogs on one of the rotating engaging parts 46. Or put differently, the stationary engaging part 44 has a circular engaging distance, i.e. along the first cogwheel 48, along which a peripheral engaging length around a rotating engaging part 46 engages, i.e. along the second cogwheel 50, and the circular engaging distance is different than any multiple of the peripheral engaging length. The spray arm 20 is sealed against the fixed conduit 42 by means of a rotational sealing 52, i.e. a sealing which seals between a rotating part and a stationary part. This rotational sealing 52 is the only rotational sealing required in the entire rotating spray arm 20 assembly despite there being at least three movable parts which are flowed through by the liquid. The three movable parts are, the spray arm 20 itself and the two movable tubes 32. This is possible due to the arrangement of the movable tubes 32 entirely inside the spray arm 20.

Figs. 5 and 6 schematically illustrate cross sectional side views of a central part and an outer part of a rotatable spray arm 20 according to example embodiments. The spray arm 20 is rotatably attached to a fixed conduit 42 inside a not-shown compartment of a dishwasher. Liquid under pressure is lead through the fixed conduit 42 into the spray arm 20 to exit therefrom through nozzles 36, one of which is illustrated in Fig. 6, and through a drive outlet 28 at each outer end 26 of the spray arm 20. The liquid under pressure rotates the spray arm 20 about an axis of rotation B by being ejected through the drive outlet 28.

The spray arm 20 comprises a fixed tube 30 and a movable tube 32. The tubes 30, 32 are circular and concentric about an arm axis A. The movable tube 32 is arranged outside the fixed tube and is rotated about the arm axis A by means of a driving arrangement 40. The driving arrangement 40 comprises a stationary engaging part 44 connected to the fixed conduit 42 and a rotating engaging part 46 connected to the movable tube 32. The rotating engaging part 46 is frictionally engaged with the stationary engaging part 44 by means of a schematically illustrated rubber O-ring 59. The rotating engaging part 46 comprises an axle 60. The axle 60 is connected to the movable tube 32 at the outer end 26 of the spray arm 20. As the spray arm 20 rotates about the axis of rotation B, the spray arm 20 rotates in relation to the stationary engaging part 44. Since the stationary engaging part 44 and the rotating engaging part 46 are frictionally engaged, the rotating engaging part 46, and accordingly also the movable tube 32, will be rotated about the arm axis A. It may be noted that in the schematic Fig. 5 a wheel 62 of the rotating engaging part 46 and a wall portion 62 of the spray arm 20 in practice may be provide with through holes to facilitate for the liquid to flow into the fixed tube 30. The fixed tube 30 is provided with control outlets 34 in the form of slots, one of which is illustrated in Fig. 6. As explained above, when movable tube 32 rotates, liquid will be ejected through the nozzle 36 while it is positioned within the control opening 34. Again, since the nozzle 36 rotate with the movable tube 32, and due to the control opening 34 having a larger circumferential extension than the nozzle 36, the nozzle 36 ejects liquid in a circle sector in relation to the fixed tube 30. The circle sector is defined by the size of the control opening 34, which thus defines a spraying angle of the nozzle 36.

The movable tube 32 may be provided with nozzles 36 arranged at different

circumferential positions around the circumference of the movable tube 32. The fixed tube may accordingly be provided with one control opening 34 for each nozzle 36. As the movable tube 32 rotates outside the fixed tube 30, only some of the nozzles 36 will be open at a time since only some of the nozzles 36 will be positioned within the control openings 34 at a time.

Fig. 7 illustrates a cross sectional side view of an inner part of a rotatable spray arm 20 according to example embodiments. The spray arm 20 is rotatably attached to a fixed conduit 42 inside a not-shown compartment of a dishwasher. Liquid under pressure is lead through the fixed conduit 42 into the spray arm 20 to exit therefrom through nozzles 36 and through a not-shown drive outlet an outer end of the spray arm 20. The liquid under pressure rotates the spray arm 20 in the same manner as discussed above.

The spray arm 20 comprises a fixed tube 30 and a movable tube 32. The tubes 30, 32 are circular and concentric about an arm axis A. The movable tube 32 is arranged inside the fixed tube 30 and is in the form of a cage structure with longitudinal bars 70 and circumferential sections 74. The circumferential sections 74 abut an inside of the fixed tube 30. The movable tube 32 is rotated about the arm axis A by means of a driving arrangement 40. The driving arrangement 40 comprises a stationary engaging part 44 connected to the fixed conduit 42 and a rotating engaging part 46 connected to the movable tube 32. The rotating engaging part 46 is frictionally engaged with the stationary engaging part 44 by means of a schematically illustrated rubber O-ring 59. The rotating engaging part 46 comprises an axle 60 which is connected to the movable tube 32. As the spray arm 20 rotates, the spray arm 20 rotates in relation to the stationary engaging part 44. Since the stationary engaging part 44 and the rotating engaging part 46 are frictionally engaged, the rotating engaging part 46, and accordingly also the movable tube 32, will be rotated about the arm axis A.

The fixed tube 30 is provided with nozzles 36 directed in different directions. The number of nozzles 36 may be larger than for a similarly sized arm in a contemporary dishwasher of similar size. As will be explained bellow, requirements on a pump of the dishwasher will be about the same as for the similarly sized contemporary dishwasher. The circumferential sections 74 of the movable tube 32 are provided inside the fixed tube 30 opposite to the nozzles 36. The circumferential sections 74 of the movable tube 32 are discontinuous, i.e. an interruption 76 is provided in the circumferential sections 74. The interruptions 76 form control openings 34 in the movable tube 32. Liquid will be ejected through each nozzle 36 while a control opening 34 passes the nozzle 36, and the nozzle 36 accordingly, is open. The nozzle 36 is closed while the remainder of the

circumferential section 74 passes the nozzle 36. Since the control openings 34 have different positions in the circumferential direction of the movable tube 32, not all nozzles 36 will be open at the same time. Accordingly, liquid consumption of the spray arm 20 in total may be kept at the same level as for a similarly sized contemporary dishwasher with a spray arm provided with fewer, but permanently open, nozzles. Since the nozzles 36 are directed in different directions, a more even distribution of the liquid inside a portion of the dishwasher may be achieved than in the contemporary dishwasher. Also foreseen is that the fixed tube 30 is provided with two or more nozzles 36 interacting with one and the same control opening 34, the two or more nozzles 36 being arranged in the same longitudinal position along the arm axis A at different peripheral positions of the fixed tube 30.

Example embodiments may be combined as understood by a person skilled in the art. For instance may the different designs of the movable tubes and of the driving arrangements for the movable tubes of the illustrated embodiments be applied in other combinations. It is also understood by those skilled in the art that the control openings may be of various other shapes than in the form of slots, such as circular or oval.

Alternatively to arranging the fixed and movable tubes concentrically, they may be arranged non-concentrically, e.g. the movable tube may be arranged more to one side inside of the fixed tube, seen in a longitudinal direction of the fixed tube. Therefore, it is to be understood that the foregoing is illustrative of various example embodiments and the invention is not to be limited to the specific embodiments disclosed and that modifications to the disclosed embodiments, combinations of features of disclosed embodiments as well as other embodiments are intended to be included within the scope of the appended claims.

As used herein, the term "comprising" or "comprises" is open-ended, and includes one or more stated features, elements, steps, components or functions but does not preclude the presence or addition of one or more other features, elements, steps, components, functions or groups thereof.

As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. As used herein, the common abbreviation "e.g.", which derives from the Latin phrase "exempli gratia," may be used to introduce or specify a general example or examples of a previously mentioned item, and is not intended to be limiting of such item. If used herein, the common abbreviation "i.e.", which derives from the Latin phrase "id est," may be used to specify a particular item from a more general recitation.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

It will be understood that when an element is referred to as being "coupled" or

"connected" to another element, it can be directly coupled or connected to the other element or intervening elements may also be present. In contrast, when an element is referred to as being "directly coupled" or "directly connected" to another element, there are no intervening elements present.

Claims

1. A dishwasher (10) comprising a pump for imparting to a liquid pressure to thereby generate liquid under pressure, a compartment (1 1 ), and at least one spray arm (20) extending in a direction of an arm axis (A), said spray arm (20) being rotatable by means of said liquid under pressure and being provided with a nozzle (36) for distributing said liquid in said compartment(1 1 ), and a control opening (34) for interaction with said nozzle (36), wherein said spray arm (20) comprises a fixed tube (30) extending in a direction of said arm axis (A) and a movable tube (32), one of said fixed and movable tubes (30, 32) being provided with said nozzle (36) and an other of said fixed and movable tubes (30, 32) being provided with said control opening (34), and wherein said fixed and movable tubes (30, 32) are arranged one at least partially within the other to allow said interaction between said control opening (34) and said nozzle (36)

characterized in that

said dishwasher (10) comprises a driving arrangement (40) for rotating said movable tube (32) substantially around said arm axis (A) to cause said control opening (34) to interact with said nozzle (36), and wherein said driving arrangement (40) is driven by means of said liquid under pressure.

2. The dishwasher (10) according to claim 1 , wherein said movable tube (32) extends substantially in said direction of said arm axis (A) and substantially concentrically with said fixed tube (30).

3. The dishwasher (10) according to any one of claims 1 and 2, wherein said driving arrangement (40) comprises a stationary engaging part (44) being stationary in relation to said compartment (11 ) and a rotating engaging part (46) connected to said movable tube (32), said stationary engaging part (44) being engaged with said rotating engaging part (46).

4. The dishwasher (10) according to claim 3, wherein said stationary engaging part (44) comprises a first cogwheel (48) and said rotating engaging part comprise a second cogwheel (50), said first and second cogwheels (48, 50) being engaged with each other.

5. The dishwasher (10) according to claim 3, wherein said stationary engaging part (44) and said rotating engaging part (46) are frictionally engaged with each other.

6. The dishwasher (10) according to any one of claims 3 - 5, wherein said stationary engaging part (44) has a circular engaging distance and said rotating engaging part (46) has a peripheral engaging length, and wherein said circular engaging distance is different than any multiple of said peripheral engaging length.

7. The dishwasher (10) according to any one of the preceding claims, wherein said control opening (34) and said movable tube (32) are arranged to open and close said nozzle (36).

8. The dishwasher (10) according to any one of the preceding claims, wherein said spray arm (20) comprises a drive outlet (28) at an outer end (26) of the spray arm (20), the spray arm (20) being rotatable by means of said liquid under pressure exiting said drive outlet (28).

9. The dishwasher (10) according to any one of the preceding claims, wherein said nozzle (36) is arranged in said movable tube (32) and said control opening (34) is arranged in said fixed tube (30).

10. The dishwasher (10) according to claim 9, wherein said control opening (34) is larger than said nozzle (36) for defining a spraying angle of said nozzle (36) over which said liquid is adapted to be ejected through said nozzle (36) as said movable tube (32) rotates in relation to said fixed tube (30).

1 1 . The dishwasher (10) according to any one of the preceding claims, wherein said movable tube (32) or said fixed tube (30) is provided with two or more nozzles (36) interacting with one and the same control opening (34), and wherein said two or more nozzles (36) are arranged in the same longitudinal position along said arm axis (A) at different peripheral positions of said movable tube (32) or said fixed tube (32).

12. The dishwasher (10) according to any one of the preceding claims, wherein said movable tube (32) is arranged inside said fixed tube (30).

13. The dishwasher (10) according to any one of claims 1 - 11 , wherein said movable tube (32) is arranged outside said fixed tube (30).

14. The dishwasher (10) according to any one of claims 1-8, wherein said nozzle (36) is arranged in said fixed tube (30) and said control opening is arranged in said movable tube (32).

15. The dishwasher (10) according to claim 12, wherein a fixed conduit (42) is arranged in said compartment (1 1 ) leading from said pump to said rotating spray arm (20), and wherein one rotational sealing (52) is arranged between said fixed conduit (42) and said spray arm (20), said one rotational sealing (52) being the only rotational sealing used in an assembly comprising said fixed conduit (42), said spray arm (20), said fixed tube (30) and said movable tube (32).