The present invention relates to a hydraulic device for use mainly, but not exclusively, in the field of household appliances, particularly in dishwashers and washing machines according to the preamble of claim 1.
Such devices are known from, e.g., GB 1 468 870 A or EP 0 753 281 A.
The object of the present invention is to provide a device of the type indicated above in which, even in the presence of the necessary hydraulic conditions, normal siphoning does not start, at least for a time.
This object is achieved by means of a device of the type indicated above, characterized in that at least one cross-section of the intermediate portion is constricted in comparison with the cross-sections of the first and second branches. This cross-section of the intermediate portion is preferably constricted by at least 50% in comparison with the cross-sections of the first and second branches.
The presence of the constriction causes siphoning not to start normally in the duct, even in the presence of the hydraulic conditions necessary for starting, because air bubbles remain inside the duct and are not expelled, at least in the short term.
This may be advantageous, for example, when the signal produced by the level-sensor means is required, at least temporarily, not to correspond to that which would be produced if the siphon-shaped duct were operating in normal running conditions.
Further advantages of the present invention will become clear from the following detailed description, given with reference to the appended drawings, provided purely by way of non-limiting embodiment of the invention, in which:
A hydraulic device comprises (Figure 1), a first chamber 10 and a second chamber 12. In particular, the first chamber 10 is a compartment of the filling system of a household appliance such as a dishwasher or a washing machine, and the second chamber 12 is a region with which sensor means 14 are associated for providing a signal indicative of the level of liquid in the first chamber 10. The sensor means are of a known type, for example, a pressure switch.
A first duct 16 connects the first chamber 10 to the second chamber 12. It is shaped like a siphon and has a first branch 18 in communication with the first chamber 10, a second branch 20 in communication with the second chamber 12, and an intermediate portion 22 connecting the first branch 18 to the second branch 20 and having a cross-section 24 which is constricted in comparison with that of the branches 18, 20.
The first chamber 10 also has a water-inlet duct 26 and an outlet duct 28 in which a solenoid valve 30 is disposed.
When the latter is opened, the water in the first chamber 10 is discharged without difficulty through the duct 16. The water in the second chamber 12, in which the sensor means 14 are present, on the other hand, is slowed by the constriction 24. The sensor means 14 thus continue, for a certain time, to send a signal corresponding to the pre-existing level condition, which may be advantageous, in particular, with regard to the period of time required to empty the first chamber 10.
Figure 2 shows a variant of the device of the invention. In this drawing, parts identical or equivalent to those shown in the previous drawing retain the same reference numerals.
In this embodiment, the first chamber 10 is a washing tank of a household appliance such as a dishwasher or washing machine, and the second chamber 12 is a region with which sensor means 14, for example, a pressure switch, are associated for providing a signal indicative of the level of liquid in the first chamber.
Moreover, the second branch 20 of the first siphon-shaped duct 16 also constitutes the first branch of a second siphon-shaped duct 32, the second arm 34 of which opens into the second chamber 12 and which is inverted relative to the first duct 16.
By virtue of this arrangement, the liquid in the first chamber 10 can never come into direct contact with the sensor means 14 from which it is always isolated by an air bubble which cannot be eliminated because of the presence of the two siphon-shaped ducts 16, 32.
This prevents the liquid from wetting the electrical components and thus damaging them in the event of breakage of the diaphragm of the pressure switch of the sensor means 14.
Figure 3 shows a further variant of the device of the invention. In this drawing, parts identical or equivalent to those shown in the previous drawings retain the same reference numerals.
In this case, the first chamber 10 is a washing tank of a household appliance such as a dishwasher or washing machine and the second chamber 12 is a compartment of the system for filling the washing tank. As well as being connected by the first siphon-shaped duct 16 having a constricted cross-section 24, the first and second chambers 10 and 12 are also connected by a third siphon-shaped duct 36 without a constriction.
The chambers also have respective liquid-supply ducts 38, 40.
The sensor means 14 detect the level of water in the second chamber 12 and are calibrated in a manner such as to bring about a further admission of water when the level measured is below a threshold level 42 higher than that at which the constriction 24 is disposed.
During normal operation of the device, the water supplied through the duct 38 into the second chamber 12 is discharged through the third siphon duct 36 into the first chamber 10. Conditions such as to prevent siphoning from starting may therefore arise in the duct 36, for example, as a result of an incorrect movement of the household appliance.
In this case and when the second chamber 12 is full of water, the first duct 16 enables water to flow out of the second chamber 12 into the first chamber 10 until the level of water in the second chamber 12 is reduced to that of the constriction 24. This level is in any case lower than that of the threshold 42 so that, in the next working cycle of the appliance, the sensor means 14 can bring about a new flow of water into the second chamber 12.
If, on the other hand, the level in the first chamber 10 is such that the water therein tends to flow out into the second chamber 12, this is prevented by the constriction 24 which causes air bubbles to form in the second branch 20 of the duct 16 and siphoning consequently not to start.
Naturally, it is intended that, the principle of the invention remaining the same, the details of construction and forms of embodiment may be varied widely with respect to those described and illustrated in the drawings, without thereby departing from the scope of the present invention as defined by the appended claims.
As already mentioned, the device of the invention can be used, for example, in household appliances such as dishwashers or washing machines. In particular, one or more of its various components such as the chambers, the sensor means and the branches of the siphon duct, may be formed integrally with other elements of the household appliance, such as the sump or water softener. Alternatively, these components may be assembled with the other elements of the household appliance in a manner such as to facilitate dismantling when it is necessary, for example, to perform cleaning operations.