The present invention relates to a device for moving washing impellers or sprayers within wash chambers of washing appliances. Said device is applied to a washing and/or drying machine, e.g. a dishwasher.

Dishwashers are known which, for washing crockery in the wash chamber, comprise at least two rotary sprayers, e.g. a rotary sprayer for washing the upper portion of the chamber, in particular crockery arranged on an upper rack, if available, and a lower rotary sprayer for washing the lower portion of the same wash chamber, in particular crockery arranged on a lower rack. Preferably, said washing machines comprise two racks, i.e. a first upper rack and a second lower rack, each associated with at least one rotary sprayer.

Normally the rotary motion of the sprayer is attained by exploiting the inclination of the water jet generated by a plurality of nozzles. In fact, the nozzles are appropriately arranged in a manner such that the force of the exiting water generates an equal and opposite force onto the sprayer, which will thus rotate, e.g. about a vertical axis.

Among the rotary sprayers installed in a wash chamber, the one that washes crockery with most difficulty is the lower rotary sprayer that must wash the lower rack, where crockery particularly difficult to wash is normally placed, such as pots, dishes and cutlery. Such pieces of crockery give rise to several wash problems because they may be heavily encrusted or may have shapes that do not allow water to be properly incident on their surfaces.

A further problem observed during the washing for the lower rotary sprayer relates to the possibility that the latter might strike against improperly positioned crockery, such as cutlery, which might obstruct the sprayer as it turns, thus preventing it from correctly washing some areas of the rack.

To improve the washing action, the lower rotary sprayer comprises nozzles having greater diameters than the other rotary sprayers, so as to ensure a stronger impact of the water against the crockery, resulting however in higher water consumption.

Loading pieces of crockery such as pots creates another problem for sprayer rotation. When pots are not properly arranged, in fact, their shape may cause the water jet to splash back from them, sometimes in a direction opposite to the rotary motion of the sprayer, thus reducing its revolution speed or even causing it to temporarily stop.

The above-described problems do not allow to obtain an optimal washing result of the lower rack as the loaded crockery and/or the arrangement thereof varies, implying that some sections of the wash chamber and/or of the single rack may be washed better than the remaining portions of the rack and/or of the wash chamber.

Rotary sprayers are also known which are removably mounted to the bottom base of the wash chamber and which are adapted to rotate, under the hydrodynamic thrust of water exiting through a plurality of nozzles, about a vertical axis located at the centre of the wash chamber. Such a rotary sprayer for washing the central portion of the wash chamber comprises just a single jet that directs a water jet along said axis of rotation, thus reducing the cleaning power in the central part of the wash chamber.

Arms are also known, whereto one or more rotary sprayers may be secured in different manners. Normally, such arms are idle and are mounted on rolling bearings. Such devices are moved by the hydrodynamic thrust of water. In fact, the hydrodynamic thrust of water causes the sprayers to rotate and, through a satellite movement, also moves said arm. This solution does not allow to determine the position of the arm and, as a consequence, the position of the rotary sprayer within the wash chamber, in particular in which section of the rack it is located.

Devices or arms are also known which, through suitable actuating devices, can be driven in a manner such as to move at least one associated rotary sprayer to different areas of the wash chamber in order to improve the cleaning action. Patent application EP1132039 describes arms adapted to be moved by actuator means. Through a cam system, the arm can, as it moves, move the rotary sprayer along an ellipsoidal orbit. Said actuators allow the arm to rotate by 180° at most, as clearly shown in the drawings.

Normally, in order to direct the water towards the various rotary sprayers included in the wash chamber, dishwashers comprise an alternate wash assembly adapted to switch and distribute fluid flows from an inlet, connected to a supply circuit, e.g. the water main, or from a closed circuit, to one or more outlets, connected to one or more hydraulic circuits, in turn connected to said one or more rotary sprayers . Said alternate wash assembly is actuated by a motor that drives a selector which, depending on its rotation, opens and/or closes one or more hydraulic output circuits in accordance with a predetermined wash program that defines the portion of the wash chamber to be washed.

In the prior art, control of the movement device or arm is ensured by an actuator which is independent of the actuator included in the alternate wash assembly. This implies the impossibility of having the sprayer stop at all points, because the actuator only has two positions or states .

Arm movement devices are also known wherein an actuator moves said arm, which is associated with at least one rotary sprayer. Such movement devices comprise a part of the mechanism for transmitting motion from the actuator to the device or arm inside the wash chamber. This implies that such mechanism portions must be properly insulated to protect said transmission mechanism against corrosion induced by water and to avoid that dirt residues might deposit into sensitive portions of the device, which might lead to arm seizure.

Rotary sprayer movement devices are known which, through at least two motors, can move a rotary sprayer in an XY plane in order to wash specific sectors of the rack. Such a device requires two actuators in order to move said rotary sprayer in space, and most of the drive mechanisms are within the wash chamber, resulting in the above- mentioned problems of corrosion or dirt accumulation. In addition, controlling the proper positioning of the rotary sprayer in the desired point is a very complex task, because at least one position sensor is required for each axis along which said rotary sprayer can move. It is also necessary that the duct supplying water to the rotary sprayer be flexible, so that it can follow the sprayer's movements. The necessity of using a flexible duct may cause an interruption in the water flow to the rotary sprayer because of undesired duct occlusions due, for example, to bottlenecks or pressures normally caused by the crockery.

Devices for moving the rotary sprayer within the wash chamber are also known which allow said rotary sprayer to be moved through rotation of an arm. Movement is only possible for small angles of rotation; during said movement, moreover, rotation of the rotary sprayer is prevented by, for example, the walls of the wash chamber.

The present invention aims at solving the above- mentioned technical problems of the prior art by providing a device for rotatably moving at least one rotary sprayer, thus allowing the rotary sprayer to be positioned in the desired zones of the wash chamber.

One aspect of the present invention relates to a movement device having the features set out in the appended claim 1.

A further aspect of the present invention relates to a dishwasher having the features set out in the appended claim 7.

Auxiliary features of the movement device and of the dishwasher are set out in respective dependent claims appended hereto .

The features and advantages of the device and of the dishwasher according to the present invention will become more apparent from the following patent description of at least one embodiment thereof and from the annexed drawings, wherein :

• Figure 1 shows a perspective view of the movement device according to the present invention;

· Figure 2 shows an exploded view of the device of

Fig. 1;

• Figure 3A is a sectional side view of the device of Figure 1, in a first embodiment thereof;

• Figure 3B is a perspective view of a preferred embodiment of the actuating device according to the present invention;

• Figures 4A, 4B and 4C show the arm of the movement device according to the present invention, comprising a first embodiment of the torque limiting means; in particular, Figure 4A is an exploded view of the arm of the movement device according to the present invention, Figure 4B is a sectional side view of the same arm, Figure 4C is an exploded view of the torque limiting means in a first embodiment thereof;

· Figures 5A, 5B and 5C show the arm of the movement device according to the present invention, comprising a second embodiment of the torque limiting means; in particular, Figure 5A is an exploded view of the arm of the movement device according to the present invention, Figure 5B is a sectional side view of the same arm, Figure 5C is an exploded view of the torque limiting means in a second embodiment thereof;

• Figures 6A, 6B and 6C show, in different views, the alternate wash assembly; in particular, Figure 6A is a top view of the alternate wash assembly; Figure 6B is a sectional view of a first embodiment of the alternate wash assembly; Figure 6C is an exploded view of a second embodiment of the alternate wash assembly, comprising fluid heating means;

• Figures 7A and 7B show alternative embodiments of the movement device according to the present invention; in particular, Figure 7A shows the alternate wash assembly comprising an additional third outlet, Figure 7B shows a movement device to which a vapor circuit can be applied;

• Figure 8 is a perspective view of a dishwasher comprising a movement device according to the present invention;

• Figure 9 is a circuit block diagram of the electronic devices connected to a central control unit;

• Figure 10 is an exploded view of a variant of the arm of Figure 1.

With reference to the above-mentioned drawings, the device for moving at least one rotary sprayer 5, which is adapted to rotate about a first axis "R" , comprises an arm 3 capable of rotating by 360° about a second axis "Z" , preferably vertical, on which said rotary sprayer 5 is rotatably mounted; at least one actuating device 2, which is adapted to rotate said arm 3 about said second axis "Z" .

Said arm is preferably asymmetric and comprises a single rotary sprayer 5 mounted in the proximity of a peripheral portion 33 of the same arm 3.

Preferably, said actuating device 2, connected in the proximity of a coupling portion 32 of arm 3, selectively rotates the same arm 3 in order to position said rotary sprayer 5 at desired angles of rotation of arm 3 about said second axis "Z" . Preferably, said actuating device 2 is connected to arm 3 at coupling portion 32 of arm 3 and to the rest of the structure of the washing appliance equipped with the movement device.

In the preferred embodiment, said actuating device 2 comprises an actuator 21, preferably one motor and at least one motion transmission mechanism 22, which is adapted to transmit motion from said actuator or motor 21 to said at least one arm 3. More preferably, said motion transmission mechanism 22 comprises at least one shaft 221b fitted on one end to coupling portion 32 of arm 3 and on the opposite end to the shaft of motor 21, so that the second axis of rotation "Z" of arm 3 corresponds to the axis of rotation of shaft 221b.

Preferably, said shaft 221b is fitted on one end to a joining element 30 comprised in said coupling portion 32.

In particular, said arm 3 is mounted on rolling bearings that allow arm 3 to rotate by 360° about said second axis "Z" .

Said arm 3 is connected to the hydraulic circuit intended for rotary sprayer 5.

In addition to supporting associated rotary sprayer 5, arm 3 also acts as a duct for supplying water to rotary sprayer 5.

Arm 3, fitted on said second shaft 221b, comprises an internal duct 31 allowing water to flow towards rotary sprayer 5.

As shown in the drawings, said arm 3 is an asymmetric arm, since it comprises a coupling portion 32 in the proximity of one end of said arm 3 and a peripheral portion 33 at the opposite end of said arm 3, on which at least one rotary sprayer 5 is mounted.

Said coupling portion 32 also defines a first portion of duct 31, thereby allowing the fluids to flow towards rotary sprayer 5.

Said washing and/or drying machine is preferably a dishwasher 1 comprising an outer casing 10, a wash chamber 11, at least one rotary sprayer 5 for distributing wash fluid for washing crockery, as shown by way of example in Figure 8.

Preferably, said movement device according to the present invention is located in the proximity of an alternate wash assembly 4 adapted to switch and distribute fluid flows from an inlet 44, connected to a supply circuit, to one or more outlets (43a, 43b), connected to one or more hydraulic circuits.

Inlet 44 of said alternate wash assembly 4 is connected to a wash pump, which takes water from a water collecting sump 6, located in the proximity of said arm 3, thereby creating a closed supply circuit; said one or more outlets 43a, 43b are connected to as many hydraulic circuits, which are adapted to transport fluids, e.g. water, to the various zones of the wash chamber for distribution. Preferably, said alternate wash assembly comprises a first outlet 43a, which is connected to a hydraulic circuit adapted to supply an upper rotary sprayer (not shown) ; and a second outlet 43b, which is connected to a hydraulic circuit adapted to supply lower rotary sprayer 5.

Essentially, said alternate wash assembly 4, shown by way of example in Figures 6A, 6B and 6C, comprises a chamber 41 in which a selector 42 is arranged. Said selector 42 is adapted to selectively open and/or close one or more outlets (43a, 43b) depending on which hydraulic circuit must be activated and/or deactivated.

In a preferred embodiment, said selector 42 is moved by means of said actuating device 2.

The shape, dimensions and typology of selector 42 in use may vary depending on design specifications. For the purposes of the present invention, the operation of the alternate wash assembly 4 will not be described in detail herein, since it is known to those skilled in the art.

In an alternative embodiment of alternate wash assembly 4, shown in Figure 6C, chamber 41 internally comprises at least one heating means 46, e.g. a resistor, adapted to selectively heat the fluid, e.g. water, that must be directed to the various hydraulic circuits connected to alternate wash assembly 4. The use of heating means 46 allows to eliminate the pressure switch normally included in prior-art dishwashers 1, along with the associated take-off on sump 6 and welding of the sump 6.

Said at least one heating means 46 comprises safety devices 461, which are connected to a central control unit 8. Preferably, said safety devices 461 are electric/pneumatic and comprise at least one sensor 462 and a switch adapted to determine the temperature and/or the pressure of the fluid and to deactivate said at least one heating means 46 when a preset temperature is reached or if the pressure drops. In fact, temperature sensor 462 is monitored by said control unit 8, which, when it detects a temperature equal to or higher than a preset maximum temperature, will turn off heating device 46 by opening the electric circuit.

If a pressure drop occurs due to lack of fluid or other faults, such as, for example, a malfunctioning wash pump, sensor 462 will either open the switch directly or send a signal, e.g. to control unit 8, for opening the switch and turning off heating means 46.

Preferably, said control unit 8 will open the switch, thereby opening the circuit of heating device 46, should any current dispersion occur which might be potentially dangerous for the user of dishwasher 1.

In addition, as shown in Figure 7A, said alternate wash assembly 4 may comprise a third outlet 43c adapted to be connected to a hydraulic circuit comprising a water recovery container (not shown in the drawings) or a drying device .

As aforementioned, said actuating device 2 comprises an actuator 21, preferably a single motor, and at least one motion transmission mechanism 22, adapted to transmit motion from said actuator or motor 21 to said at least one arm 3. Said motion transmission mechanism 22 may also be adapted to transmit motion from said actuator or motor 21 to said at least one alternate wash assembly 4.

Preferably, said arm 3 is located within wash chamber 11; instead, said at least one actuating device 2 is external to the same wash chamber 11 of said washing machine 1 whereto said movement device has been applied. In fact, said actuating device 2 is preferably arranged underneath the bottom base of wash chamber 11, thus being protected against the action of water, and particularly not being in direct contact with either the wash water or dirt residues resulting from the various wash steps, so that any corrosion or seizure of the motion transmission mechanisms 22 is prevented.

Said actuating device 2 is in turn controlled by a central control unit 8 for the purpose of allowing said at least one arm 3 to be placed into desired positions inside the wash chamber for predetermined time periods. In particular, as shown in Figure 9, central control unit 8 is susceptible of being connected to said motor 21.

Preferably, said central control unit 8 is adapted to execute a wash program of same dishwasher 1, which specifies the positions and the stop times of rotary arm 3 within wash chamber 11. Said control unit 8 may be connected to a memory unit 81 storing at least one wash program. Said control unit 8 may possibly comprise said memory unit 81.

Preferably, at the beginning of each wash step arm 3 is always positioned in such a way that rotary sprayer 5 is in a predetermined sector of wash chamber 11. At the end of each wash cycle, arm 3 may possibly stop in a predetermined position prior to the beginning of the next wash cycle.

Central control unit 8 is adapted to activate other devices normally included in dishwasher 1 and to monitor a plurality of sensors which are useful for controlling the same dishwasher. Such devices and sensors will not be described in detail herein, since they are known to those skilled in the art.

In the embodiment shown in the annexed drawings, arm 3 is rotatably supported around a fixed axis, preferably around said second axis "Z" , which is located in the proximity of the centre of the base of wash chamber 11. In particular, said arm 3 is located in the proximity of sump 6 comprised in wash chamber 11. Rotary arm 3 has a predetermined revolution speed. In a preferred embodiment, the revolution speed of arm 3 may be a multiple or submultiple of the revolution speed of selector 42 of the alternate wash assembly.

In a preferred embodiment, shown in Figure 3A, said motion transmission mechanism 22 comprises a shaft 221b fitted on one end to a joining element 30 of arm 3 and on the opposite end to the shaft of motor 21.

Said motor 21 is an electric motor, e.g. a step motor, as normally used for the devices included in the dishwasher. Preferably, the maximum torque of said motor 21 is limited in order to avoid any damage to actuating device 2 which might be due, for example, to an improperly positioned piece of cutlery stopping the rotation of the arm.

In a non-limiting alternative embodiment, as shown by way of example in Figures 3B, said motion transmission mechanism 22 comprises a first shaft 221a fitted on one end to said selector 42 of the alternate assembly 4 and on the opposite end to the shaft of motor 21; a second shaft 221b is fitted on one end to a joining element 30 of arm 3 and on the opposite end to a pinion 222b, which meshes with a crown wheel 222a mounted to said first shaft 221a. The ratio between said crown wheel 222a and said pinion 222b is such that the revolution speed of the first shaft 221a is a multiple of the revolution speed of said second shaft 221b.

In a preferred embodiment, as shown by way of example in Figure 9, said actuating device 2 comprises at least one sensor 24 adapted to detect the position of said at least one arm 3 within wash chamber 11 of a washing machine 1, and possibly also the position of selector 42 of the alternate wash assembly. Said at least one sensor 24 is, for example, an encoder, mounted to said shaft 221b and adapted to determine the direction of rotation of arm 3 and the absolute position thereof within wash chamber 11, with a predetermined uncertainty, as a function of the rotation of shaft 221b. Said at least one sensor 24 may be a position sensor of any type, such as, for example, capacitive, resistive, inductive, etc.

Said at least one sensor 24 is susceptible of being connected to said control unit 8 for the purpose of determining the position of arm 3, so that rotary sprayer 5 can be positioned as required within the wash chamber. In fact, said sensor 24 allows rotary sprayer 5 to be positioned in a desired zone of wash chamber 11 through an appropriate movement of arm 3. control unit 8, depending on the data received from said sensor 24, can operate motor 21 in a manner such as to place rotary sprayer 5 into the desired position by rotating said arm 3.

Said arm 3 is connected to the hydraulic circuit intended for lower rotary sprayer 5. Preferably, arm 3 is mounted through fastening means 62 to said second outlet 43b, which is located in a housing within sump 6.

In addition to supporting associated rotary sprayer 5, arm 3 also acts as a duct to supply water to rotary sprayer 5, e.g. from the second outlet 43b of alternate assembly 4, to which it is connected.

In particular, said arm 3 is mounted on, rolling bearings that allow arm 3 to rotate by 360° about said second axis "Z" . As aforementioned, arm 3 is fitted to said second shaft 221b, but comprises an internal duct 31 allowing water to flow from the alternate wash assembly 4 to rotary sprayer 5.

As shown in the drawings, said arm 3 is an asymmetric arm, since it comprises a coupling portion 32 in the proximity of one end of said arm 3, and a peripheral portion 33 at the opposite end of said arm 3, where only one rotary sprayer 5 is mounted.

Said coupling portion 32 comprises said joining element 30 fitted to said shaft 221b, so that the second axis of rotation "Z" of arm 3 corresponds to the axis of rotation of shaft 221b. Said coupling portion 32 also defines a first portion of duct 31, thereby allowing fluids to flow, for example, from said alternate wash assembly 4 to rotary sprayer 5. Preferably, said arm 3 is made of plastic material, comprising an upper portion 3a and a lower portion 3b that can be removably combined together, as shown in Figures 4A and 5A.

Preferably, said joining element 30 comprises at least one torque limiting means 23 adapted to disengage arm 3, preferably arranged in said coupling portion 32.

In a first embodiment, shown by way of example in Figures 4A, 4B and 4C, torque limiting means 23 comprises a selective abutment element 231 appropriately associated with said joining element 30, which is adapted to abut against the inner walls of internal duct 31 in coupling portion 32; an elastic means 232, e.g. a spring, and a top element 233.

When a predetermined torque value of shaft 221b is exceeded, depending on the elastic constant of elastic means 232, selective abutment element 231 will slip on element 30, thereby preventing motion from being transmitted to arm 3 by shaft 221b. The principle of operation of torque limiting means 23 of the first embodiment is such that, following the release of arm 3, a new balance point will be reached after a rotation of shaft 221b by approximately 360°, so that it can rotate about said second axis ⁿ Z" , driven by said motor 21. This torque limiting means 23 has one balance point.

In a second embodiment, shown in Figures 5A, 5B and

5C, joining element 30 comprises an abutment portion 234 made of ferrous or ferromagnetic material, which is adapted to abut against a magnetic element 235, so that interference therebetween is generated through magnetic effect, thereby allowing motion to be transmitted to arm 3 by shaft 221b. When a predetermined torque value of shaft 221b is exceeded, the magnetic force between abutment portion 234 and interference element 235 becomes smaller than the force applied to arm 3, so that abutment element 234 will move away from magnetic element 235, thereby preventing motion from being transmitted to said arm 3.

Following the release of arm 3, shaft 221b must rotate by approximately 360° in order to engage and drive arm 3 again. This torque limiting means 23, therefore, has only one balance point when abutment element 234 is in the proximity of magnetic element 235, preferably when they face towards each other, so that the magnetic force will tend to hold them abutted against each other.

Preferably, said rotary sprayer 5 is a symmetric satellite sprayer rotating about said first axis of rotation "R" , which is parallel to the second axis of rotation "Z" of arm 3. Rotary sprayer 5 has preferably a tapered shape, its dimensions, e.g. in the longitudinal direction, being smaller than the standard dimensions used for conventional lower rotary sprayers. In particular, the longitudinal extension of rotary sprayer 5, which is secured to arm 3 in accordance with the present invention, is at most equal to half the smallest dimension of the base of wash chamber 11.

In particular, said rotary sprayer 5 is mounted onto a suitable through housing 34 comprised in peripheral portion 33 of arm 3. Said housing 34 is adapted to allow rotary sprayer 5 to rotate freely, as well as to allow the wash fluid to flow towards said rotary sprayer 5.

The same rotary sprayer 5 comprises an engagement mouth 52, which is adapted to fit into said housing 34 to allow the fluid to flow into rotary sprayer 5 and come out through a plurality of nozzles 51 in order to hit the crockery arranged in a lower rack positioned inside wash chamber 11 of dishwasher 1.

Said nozzles 51 are appropriately arranged on said rotary sprayer 5, preferably on the upper portion of said rotary sprayer 5, and have predetermines sizes. Preferably, the sizes of said nozzles 51 are smaller than the average sizes of the nozzles comprised in the lower rotary sprayers currently available on the market.

Said engagement mouth 52 comprises removable locking means 53, e.g. interference means, which are adapted to retain said rotary sprayer 5 in order to prevent it from accidentally detaching from said arm 3.

Internal duct 31 of arm 3, under said suitable housing

34, comprises a protuberance 311 which is appropriately shaped to avoid any fluid flow turbulences in duct 31 and to direct the same fluid into rotary sprayer 5.

In an alternative embodiment, shown in Figure 10, arm 3 according to the present invention comprises at least one nozzle 51 to increase the wash power, preferably located in upper portion 3a of the same arm 3.

In a preferred embodiment, shown in Figure 7B, the movement device according to the present invention can be applied to a vapor circuit or to a hydraulic circuit for water at a higher temperature than the fluid coming from alternate wash assembly 4. In particular, internal duct 31 of arm 3 can be used for conducting water vapor towards the same rotary sprayer 5 when the latter is positioned under the crockery, for improving the washing or drying action.

The use of an asymmetric arm and a smaller rotary sprayer makes available more room in wash tub 11.

The use of a smaller rotary sprayer 5, which can be moved to different sections over the base of wash chamber 11, allows, as aforementioned, to reduce the dimensions of sprayer nozzles 51.

Comparing the dimensions of rotary sprayer 5 with those of the lower rotary sprayers commonly used in prior- art dishwashers, the longitudinal extension of rotary sprayer 5 according to the present invention is half the longitudinal extension of current lower rotary sprayers.

The movement of arm 3 about said second vertical axis "Z" and the small dimensions of rotary sprayer 5 allow to wash a portion of the rack, e.g. only one fourth of the rack, thus reducing the water consumption, also because of the smaller number of nozzles 51. By way of example, for a wash chamber 11 having a 50cm side, the longitudinal dimension of arm 3 is smaller than 12.5 cm, while the rotary sprayer has a longitudinal extension of less than 25 cm. The number of nozzles 51 of lower rotary sprayer 5 is halved.

The possibility of moving arm 3, and hence of placing the rotary sprayer into desired positions for washing a particular sector of lower rack 12, improves the washing of the crockery arranged in rack 12 because the crockery is better sprinkled with wash fluid.

Furthermore, the controlled movement of arm 3 allows arm 3 to be positioned in a manner such that the fluid jets from nozzles 51 of arm 3 and/or of rotary sprayer 5 are at least partly directed towards a detergent dispenser 14 comprised in dishwasher 1, into which the user has previously poured a predetermined quantity of detergent. The possibility of intentionally directing the fluid jets towards said detergent dispenser allows dissolving the detergent into the fluid as a function of the wash step to be carried out .

The dimensions of rotary sprayer 5 and the rotation of arm 3 about said second vertical axis "Z" allow to improve the washing in the central zone of wash chamber 11 of dishwasher 1, by improving the trajectories of the fluid jets coming from the rotary sprayer.

Furthermore, the smaller number of nozzles 51 and the possibility of changing the position of rotary sprayer 5 within wash chamber 11 ensure a lower consumption of liquid, in particular water, used for washing the crockery. The smaller quantity of wash water required allows to reduce the capacity of the wash pump and the power of the associated motor, resulting in lower production costs. Positioning the rotary sprayer into particular sectors of wash chamber 11 allows to improve the wash performance, in that it is possible to change the stop times of rotary sprayer 5 in the various positions depending on the wash program in execution.

The movement device according to the present invention allows to position the rotary sprayer in the desired zones of wash chamber 11 through the use of a simple actuating device. Furthermore, the movement device is safe and immune from malfunctions or damage typically suffered by prior-art devices, because motion transmission mechanism 22 is insulated and cannot be corroded by wash fluids, nor can it be subject to dirt accumulation, which might damage the mechanism itself.

REFERENCE NUMERALS:

1 Dishwasher

10 Outer casing

11 Wash chamber

12 Rack

14 Detergent dispenser

2 Actuating device

21 Motor

22 Motion transmission mechanism

221a/b First and second shafts

222a Crown wheel

222b Pinion

23 Torque limiting means

231 Selective abutment element

232 Elastic element

233 Top element 234 Abutment portion

235 Magnetic element

24 Sensor

3 Arm

3a/b Upper and lower portions

30 Joining element

31 Internal duct

311 Protuberance

32 Coupling portion

33 Peripheral portion

34 Housing

4 Alternate wash assembly

41 Chamber

42 Selector

43a/b First and second outlets

43c Third outlet

44 Inlet

46 Heating means

461 Safety device

462 Temperature sensor

5 Rotary sprayer

51 Nozzles

52 Engagement mouth

53 Locking means

6 Sump

62 Fastening means

8 Central control unit

81 Memory unit

"Z" Second axis - arm rotation

"R" First axis - sprayer rotation