GB2274772A - A device for the controlled evacuation of steam from the washing chamber of a dishwasher machine - Google Patents

Description

2274772

DESCRIPTION

The present invention relates to a device for the controlled evacuation of steam from the washing chamber of a dishwasher machine provided with a bottom-hinged front door.

At the end of a washing cycle a considerable quantity of steam at a significantly high temperature is present in the washing chamber of a dishwasher machine.

Subsequent cooling causes condensation of this steam onto the dishes and this causes a drop in their aesthetic properties, in particular reducing their shine.

The object of the present invention is to provide an improved device for the controlled evacuation of steam from the washing chamber of a dishwasher, which allows the drying time of the dishes to be reduced thereby eliminating the above mentioned disadvantages.

This and other objects are achieved according to the invention by a device characterised in that it comprises in combination a support casing intended to be mounted in the door of the machine and in which there is defined a chamber in which the impeller of a motor driven pump is mounted; 2 the said chamber having at least one first and one second aspiration passage intended to be put into communication with the washing chamber of the machine and, the environment outside the machine respectively, and at least one breather conduit intended to be put into communication with the said external environment, in such a way that, in operation, the motor driven pump is able to in and mix in the said clunbw, air and steam drawn in from the washing chamber through the first aspiration passage and air drawn in f rom the external environment through the second aspiration passage, and to cause discharge of the resulting air/steam mixture through the breather duct to the external environment; valve means supported by the said casing and including a movable f low restrictor member associated with the said first passage; there being associated with the said flow restrictor member an electromechanical control device operable, when activated, to cause the f low restrictor member to move from an initial closure position of the said first passage to successive open positions in such a way as to cause successive increases in the flow cross section of the said first aspiration passage; and a resetting mechanism operable, after activation of the said control device, automatically to re-position the flow restrictor member in the initial closure position by the effect of a variation in the attitude of the casing such as that caused in use by opening the door of the 3 machine.

Conveniently, according to a further characteristic, the device further includes further valve means associated with the said second aspiration passage and controlled by an electromechanical control device in such a way as to cause successive decreases in the flow cross section of the second passage in correlation with the successive increases in the flow cross section of the first passage. The device may include, in particular, a single flow restrictor member associated with the first and second aspiration passages, and controlled by the same electromechanical control device, the said flow restrictor member being shaped and disposed within the casing in such a way that the variation in its position is such as to cause an increase in the f low cross section of the first aspiration passage and a decrease in the flow cross section of the second passage.

Further characteristics and advantages of the device according to the invention will appear from the following detailed description, provided purely by way of nonlimitative example, with reference to the attached drawings, in which:

Figure 1 is a perspective view of a dishwasher machine provided with a device according to the invention mounted in the front door of the machine, which is shown closed; 4 Figure 2 is a perspective view of the dishwasher machine of Figure 1 with the front door open; Figure 3 is an exploded perspective view showing the part of the door of the dishwasher machine in which the device according to the invention is mounted; Figure 4 is an exploded perspective view of the device according to the invention; Figure 5 is a front view of the device according to the invention; Figure 6 is a section view taken on the line VI-VI of Figure 5; Figure 7 is a front view of part of the device according to the invention and Figure 8 is a section taken on the line VII-VII of Figure 7; Figure 9 is a view similar to that of Figure 7, showing the device in another working condition and Figure 10 is a section, on an enlarged scale, taken on the line X-X of Figure 9; Figures 11 and 12 are section, similar to that of Figure 10, showing part of the device according to the invention in two further working conditions; Figure 13 is a view similar to that of Figure 9 and shows the device in a further working condition and Figure 14 is a section taken on the line XIV-XIV of Figure 13; and Figure 15 is a section similar to that of Figure 14, showing the device according to the invention in a tilted condition such as to return it to its initial operating conditions.

In Figures 1 and 2 a dishwasher machine generally indicated 1, is shown provided with a front door 2 which can turn about an axis A-A which extends close to the lower edge of that door. In Figure 1 the door 2 is shown closed, extending in a substantially vertical plane, whilst in Figure 2 it is shown open to allow access to the washing chamber 3 of the machine 1.

In a known way the door 2 is hollow and comprises an inner wall 4 facing the washing chamber and an outer wall 5 facing the environment surrounding the machine 1.

When the door 2 is in its closed position shown in Figure 1 its inner wall 4 cooperates with seals not illustrated and sealingly closes the washing chamber 3 of the machine.

Between the walls 4 and 5 of the door 2 is defined an air space which in the usual manner communicates with the environment surrounding the machine, for example through breather holes provided in the sections which frame the door. The said air space does not however communicate with the washing chamber when the door 2 is in its closed position.

6 In the embodiment illustrated in Figures 1 to 3, close to the upper edge of the door 2 there is formed an aperture 6, the outer wall 5 thereof, in which there is a grille 7. In an almost facing relationship to this grille there are formed a plurality of apertures in the inner wall 4, indicated with the reference numeral 8 in Figures 2 and 3. In the illustrated embodiment the apertures 8 are situated within a circle 9 indicated in broken outline in Figure 3. Between the apertures 6 and 8 of the door 2 is mounted a device 10 for the controlled evacuation of the steam in the washing chamber 3 at the end of a washing cycle of the machine.

This device comprises a rigid casing formed by two parts 11 and 12 coupled together. A chamber 13 (Figures 4 and 6) is def ined between these parts. The part 11 of the casing receives a motor driven pump 14 including a blade impeller 15 mounted rotatably within the chamber 13 and capable of being driven to rotate by an electric motor 16 fixed externally of the casing part 11.

The electric motor 16 of the motor driven pump 14 is intended to be controlled, in a manner known per se, by the control unit or programmer of the dishwasher machine 1.

The motor driven pump 14 is of centrifugal type and the.casing parts 11 and 12 are shaped in such a way as to 7 f orm, together, a spiral delivery duct 17 (Figure 4) which communicates with the chamber 13 and vkdch c into a terminal breather duct 18 defined by a boxlike tubular portion 19 of the casing part 11.

With reference in particular to Figures 4 and 6, the casing part 12 comprises a main f lat wall 20 having a circular aperture 21 (Figure 6) facing the central portion of the impeller 15 of the pump. Around the aperture 21, on the outer face of the wall 20 of the casing part 12, is connected a tubular part 22 (Figure 6) which is coaxial with the impeller 15 and which - on the opposite side of this impeller - has a flat end wall 23. As can be seen in Figure 6, this end wall 23 extends radially beyond the tubular portion 22 and is connected to an annular flange element 24 in the outer face of which is formed a groove 25 housing a sealing ring 26. The diameter of this ring is greater than or equal to the diameter of the circle 9 (Figure 3) which circumscribes the aperture 8 of the inner wall 4 of the door 2 of the machine.

Between the periphery of the flange element 24 and the main flat wall 20 extends a cylindrical pin 27 parallel to the axis of the impeller 15.

The wall 23 has a pair of windows 28 in the shape of substantially circular sectors, on opposite sides of the 8 centre of this wall (see in particular Figure 4).

The annular wall of the tubular part 22 has a pair of diametrically opposite apertures 29,30 (see in particular Figure 6).

The tubular part 22 and the associated end wall 23 together define a cavity 31 (Figure 6) communicating with the pump impeller chamber 13. In this cavity is disposed a valve member generally indicated 32. As is better seen in Figure 4, this valve member is substantially cup shape, and has a pair of apertures 33 in its f lat end wall in the f orm of circular sectors on either side of its axis. The shape of these apertures or windows preferably, but not necessarily, corresponds to that of the apertures 28 of the wall 23.

The cylindrical annular wall of the valve member 32 has in turn a pair of apertures 34 and 35 the size and angular extent of which correspond to those of the apertures 29 and 30 of the tubular part 22 of the casing.

The valve member 32 has a diameter corresponding substantially to the inner diameter of the cavity 31, and is disposed in this cavity with its end wall adjacent the wall 23. It further has a tubular central hub 36 (Figure 4 to 6). A toothed sector 37 is formed on a portion of the periphery of this hub facing the aperture 34.

9 The reference numeral 38 indicates a butterfly shutter comprising a disk part 39 having a pair of windows 40 the shape and arrangement of which substantially correspond to those of the apertures 28 in the casing. The shutter 38 is disposed with its disk portion 39 adjacent the outer f ace of the wall 23 of the casing, and has a central pin 41 which extends through and beyond the hub 36 of the valve member 32. At the end of the pin 41 protruding beyond the hub 36 there is fixed a stop ring 42, and a coil spring 43 is interposed between this ring and an outer annular shoulder of the said hub. At the centre of the outer face of the disk part 39 of the shutter 38 is formed a recess 44 (Figures 3 to 5) operable to allow engagement of a tool, for example a screwdriver, to allow rotation of this shutter relative to the casing. In Figure 3 the adjustable shutter 38 is shown in a position such that its windows 40 are exactly facing the corresponding apertures 28 of the casing. By means of a tool the position of this shutter can be adjusted in such a way as to vary the cross sectional area of the passage corresponding to the overlap of its windows 40 with the windows 28 of the casing. This operation can be achieved even after the device has been installed in the door 2 of the dishwasher machine, an aperture 8a (Figure 3) in the inner wall 4 of the door being formed for this purpose in facing relationship to the seat 44 of the said shutter.

As can be intuitively seen by observing Figure 3, the steam evacuating device 10 is mounted in the air space of the door 2 in such a way that the sealing ring 26 and the flange 24 press against the inner face of the wall 4 of the door around the apertures 8, 8a of this wall. The box-like portion 19 of the casing, in which the breather duct 18 is defined, is disposed with its terminal aperture around the aperture 6 of the wall 5 of the door.

As can be seen in particular from Figures 3 and 4, in the lower part of the casing, particularly in its portion 11, there is formed an aperture 45 with an attached draining coupling 46 on which the end of a tube 47 (Figure 3) is fitted, the other end of the tube 47 being connected to an aperture (not illustrated) provided in the inner wall 4 of the door 2. This tube therefore allows condensation which may accumulate, during operation, within the casing of the device, to be returned into the washing chamber.

In use, when installed, the apertures 28 of the casing serve as aspiration passages, through vhich the motor 14 is able, at the end of a washing cycle, to draw steam from the washing chamber into the chamber 13. This is obviously possible on the condition that the valve member 32 is disposed in such a way that its apertures or windows 33 are at least partially facing the corresponding apertures or windows 28 of the casing. When activated th--motnr14aL-,o draws into the chamber 13 11 a flow of air from the air space of the door 2, via the apertures 29, 30 of the tubular part 22 of the casing and the facing portions 34 and 35 of the apertures in the valve member 32. The activation of the motor purp causes mixing, in the chamber 13, of steam drawn from the washing chamber with air caiiing from the air space in the door of the machine. The resulting mixture is expelled into the environment outside the machine via the spiral duct 17, the breather duct 18 and the f rontal aperture 6 of the door.

Ihe ffaxing of steam with air drawn fran the air space of the dow is useful for the purpose of "diluting" the steam in the air/steam mixture expelled to the outside, for the purpose of rendering the steam emitted to the exterior of the machine through the outlet grille 7 less concentrated, less hot and less visible.

The angular position of the valve member 32 is controllable by the control unit or programmer of the machine 1 via the devices which will now be described.

Pivoted on the pin 27 (Figure 6), which is fixed to the casing of the device, is a shaped lever 46 which in the illustrated embodiment has three arms 47-49. As is seen in Figure 6, the arm 47 extends through the windows or apertures 29 and 34 of the cylindrical wall 22 and the valve member 32 respectively, and terminates with a 12 toothed sector 50 (see also Figures 4 and 7) which meshes with the toothed sector 37 of the hub of the valve member.

The arm 48 extends substantially in the opposite direction from the arm 47 and has an eye into which is hooked one end of a coil spring 51 the other end of which is anchored at 52 to the casing. With reference for example to Figures 5,9 and 13, the spring 51 tends to urge the lever 46 to rotate in an anti-clockwise sense about the pin 27. The arm 49 of the lever 46 is arcuate and extends around the tubular wall 22 of the casing between the flange 24 and the flat main wall 20 of this casing. This arm 49 carries a mass or weight 52 which, under the action of gravity, is able to impart to the lever 46 a rotary movement in a clockwise sense about the pin 27.

The distal end 49a of the arm 49 has a slot 53 (see particularly Figure 4). Into this slot extend two arms or pawls 54 and 55. These arms or pawls have noticeably different lengths. Their upper ends are articulated to the arm 49 of outer pin 56 (Figures 4 and 8) and their lower ends form respective noses 54a, 55a facing the casing of the device.

The arms or pawls 54 and 55 can turn in respective parallel planes orthogonal to the general plane of 13 oscillation of the lever 46.

A leaf spring indicated 57 is fixed to the portion 49a of the arm 49 by means of a screw 58. This spring has two coplanar adjacent arms 59, 60 which act independently on the pivoted arms or pawls 54 and 55 respectively, from opposite sides of the casing, tending to urge them in the direction of the said casing.

With reference in particular to Figures 3 to 5, close to the end part 49a of the arm 49 of the lever 46, a locking/unlocking device generally indicated 61 is fixed to the portion 11 of the casing. This device comprises a hollow support body which in the illustrated embodiment comprises a shell 62 which is coupled to a wall 63 facing the end portion 49a of the lever 46. As is seen in particular in Figures 4 and 8, the wall 63 forms a projection 64 with an upper stop surface indicated 65. Above this stop surface the wall 63 has an aperture 66.

Within the body 62, 63 there is mounted an actuator device generally indicated 67 in Figures 8, 10-12, 14 and 15. This device comprises a support and guide structure 68 in which a resistive heating element70, for example a PTC lozenge resister, is interposed between two pairs of bimetallic bl 69. Tt-c- first pair of bimetallic blades is disposed between the bottom wall of the shell 62 and the resistive element 70, whilst the other pair of 14 bimetallic strips is interposed between the resistive element 70 and a thrust member 71. This member has a shirt-shape end 71a which extends into the body 62, 63, and a needle-like end which can project through the aperture 66 of the wall 63. A coil spring 62 is interposed between the skirt end 71a of this member and the wall 63, and tends to maintain the thrust member 71, the blades 69 and the resistive element interposed between them in contact with one another.

The arrangement is such that when the resistive element 70 has no current flowing through it and the blades 69 are therefore "cold" the spring 72 maintains the thrust member 71 in the condition shown in Figure 8, in which it does not project from the aperture 66 of the wall 63. In the casing 62, 63 of the locking/ unlocking device 61 there are fixed conductor connection members having respective projections 73 in the form of blade pins (see f or example Figures 6 and 8) which allow the supply of electrical current to the resistive heating element 70. The terminals 73 project from the casing of the locking/ unlocking device, in a recess 74 of this body, for coupling with a connector 75 (Figure 3) for connection to the control or programmer unit of the dishwasher machine.

The axial rest position of the thrust member 71 can be calibrated by means of a threaded grub screw 76 (Figure 8) disposed in a correspondingly threaded aperture of the bottom wall of the shell 72.

The arrangement of the three-arm lever 46 and the associated locking/unlocking device 61 is such that the stop surface 65 of this device intersects the path which the noses 54a, 55a of the pawls 54 and 55 can follow by the effect of the rotation of the lever 46 when the said pawls are in their working alignment shown in Figure 8.

The device described above operates as follows.

During a washing cycle the device is at rest. In this condition the thrust member 71 does not protrude beyond the wall 63 of the locking/unlocking device. The threearm lever is disposed as can be seen in Figures 7 and 8, and the nose 54a of the pawl 54 presses on the stop surface 65. The valve member 32, which is coupled to the three-arm lever 46 via the toothed sectors 37 and 50, is maintained in the condition of Figure 7, in which the solid portions of its flat wall 32a, lying between the windows 33, close the apertures 28 of the casing, preventing steam developed in the washing chamber from being able to reach the chamber 13 housing the pump impeller 15. Moreover its apertures 34, 35 face the apertures 29, 30 of the casing.

At the end of a washing cycle the controller or programme 16 unit of the machine causes the supply of current to the resistive element 70 of the locking/unlocking device 61 and activation of the- mtor 14. The bimetal strips 69 are heated and thus become curved as shown in Figure 10, causing the thrust member 71 to project from the body of the locking/ unlocking device in such a way as to cause disengagement of the nose 54a of the oscillating pawl 54 from the stationary stop surface 65. The mass 52 now causes, by gravity, rotation of the three-arm lever 46 in a clock-wise sense, as seen in Figure 7.

Correspondingly, the toothed sector 50 of the arm 47 of this lever causes anti-clockwise rotation of the valve member 32. Rotation of the lever 46 ends when the nose 55a of the pawl 55 comes up against the thrust member 71 as is shown in Figure 11. Having reached this condition the apertures 33 of the valve member 32 partially overlap the apertures 28 of the casing, by an angle indicated oc in Figure 9. Furthermore the apertures 34 and 35 of this valve member again largely overlap the corresponding apertures 29 and 30 of the casing.

The mot= 14-15 mw draws into the chamber 13, and mixes together, a flow of steam coming from the washing chamber of the machine and a flow of air from the air space in the door. The mixture is then expelled out from the dishwasher machine through the breather duct 18. The operation continues with a temporary interruption of the 17 supply of current to the heating resister element 70, so that the strips 69 return to their initial configuration and the spring 72 biases the thrust member 71 into the casing of the locking/unlocking device as shown in Figure 11. The nose 55a of the pawl 55 now engages against the stop surface 65 causing a further rotation of the threearm lever 46 and a corresponding rotation of the valve member 32 in a sense such as to cause an increase in the size of the steam aspiration passages and a corresponding reduction in the size of the air aspiration passages from the air space in the door.

The increase of the flow cross section of the steam aspiration passages and the corresponding decrease in the flow cross section of the aspiration passages for aspiration the air contained in the door obviously depend on the angle of rotation of the lever 46 to bring the nose 55a from the condition shown in Figure 11 to the canditim shown in Figure 12. This angle depends on the geometry of the device and, upon design, can be made large or small at will, depending on requirements.

The operation then continues with a further supply of current to the resistive heating element 70, which again causes the thrust member 71 to project and disengage the nose 55a from the stop surface 65. Consequently, as is shown in Figures 13 and 14, the three-arm lever 46 turns further in a clockwise sense, against the action of the 18 biasing spring 51, and the valve member 32 is disposed as shown in Figure 13. In this condition its frontal apertures 33 are totally in register with the apertures 28 of the casing. The flow cross section of the steam aspiration passages is correspondingly at its maximum. In this condition the flow cross section of the air aspiration passages from the door air space are on the other hand reduced.

After a certain time, determined for example by means of timer means known per se, the supply of current to the resistive heater element 70 is inteted. and the electric 14 is deactivated.

The user can now open the door 2 of the machine by turning it as shown in Figure 2. This tilting causes a variation in the orientation of the steam evacuation device 10, which for example assumes the orientation shown in Figure 15. In this condition the force exerted by gravity on the mass 52 of the three-arm lever 46 is less than the biasing force exerted by the spring 51. This spring thus causes rotation of the lever 46 about the pin 27 returning the said lever to the initial rest position in which it is located in relation to the lockinglunlocking device 61, as illustrated in Figure 8. The steam evacuation device 10 thus reassumes its initial configuration ready for a subsequent washing cycle.

19 In Figures 4, 5, 7 and 13 the reference numeral 80 indicates a microswitch carried by the part 12 of the casing 11, 12 in such a position that it is actuated by the arm 49 of the lever 46 when the valve member 32 is in the closed position, that is closing the steam aspiration apertures. This microswitch thus provides a signal which can be used by the control unit of the machine 1, f or example to prevent restarting of the machine without having opened the door 2 after the end of the preceding washing cycle and therefore having reset the steam evacuation device.

obviously other types of known sensors can be utilised for the same purpose.

The device described above makes it possible to prevent the aerial mixture evacuated from the machine from being visible and from having a very high temperature. This is achieved due to the fact that the flow cross section of the steam aspiration passages are initially small and are gradually increased, whilst at the same time the f low cross sections of the air aspiration pawages contained in the door are correspondingly decreased.

Naturally, the principal of the invention remaining the same, the embodiments and details of construction can be widely varied with respect to what has been described and illustrated by way of non-limitative example, without by this departing from the ambit of the present invention.

In particular, the valve member 32 can have a different form from that illustrated, being for example conical rather than cylindrical.

Likewise the number and shape of the apertures of this member as well as the number and shape of the aspiration and breather apertures of the casing of the device can differ from what has been described above.

The number of pawls which, by cooperating with the locking/ unlocking device define the successive working positions of the valve member can likewise be changed.

The locking/unlocking device can include other actuators of a type known per se in place of a bimetallic blade actuator, for example the so-called wax actuators or actuators of like similar thermally expansive material, electro-magnetic actuators,etc.

Claims (15)

21 CLAIMS

1. A device for controlled evacuation of steam from the washing chamber (3) of a dishwasher machine (1) having a front bottom-hinged door (2), characterised in that it comprises, in combination a support casing (11,12) intended to be mounted in the door (2) of the machine (1) and in which is defined a chamber (13) in which the impeller (15) of an electric pump (14) is rotatably mounted; the said chamber (13, 31) having at least first and second aspiration passages (28, 29, 30) intended to be put into communication with the washing chamber (3) of the machine (1) and the environment outside the machine (1) respectively, and at least one breather dust (17, 18) intended to be put into communication with the said external environment in such a way that in operation the pump (14) is able to withdraw air and steam drawn from the said washing chamber (3) via the first aspiration passage (28) and mix it in the said chamber (13,31) with air coming from the external environment through the second aspiration passage (29, 30) and to evacuate resultant air/steam mixture to the external environment through the breather conduit (17,18); valve means (32) supported by the said casing (11,12) and including a movable flow restrictor member (32) associated with the said first aspiration passage (28); there being associated with the said flow 22 restrictor member(32) an electromechanical control device (46; 54,55; 61) operable to cause the flow restrictor member (32) to move from an initial position closing the said first passage (28) to successive open positions in such a way as to cause successive increments in the flow cross section of the said first aspiration passage (28); and a reset mechanism (48, 51, 52) operable, after activation of the said control device, automatically to reset the flow restrictor member (32) into the initial closure position by the effect of a variation in the attitude of the casing (11,12) such as that caused in use by tilting the door (2) of the machine (1) upon opening.

2. A device according to Claim 1, characterised in that it further includes further valve means (22, 29, 30; 32) associated with the said second aspiration passage (29, 30) and controlled by an associated electro-mechanical control device (46, 54, 55; 61) in such a way as to cause successive decrements of the flow cross section of the said second passage (29,30) in correspondence with the successive increments in the flow cross section of the first passage (28).

3. A device according to Claim 2, characterised in that said valve means and said further valve means include a single flow restrictor member (32) associated with the first and second aspiration passages (28; 29, 30) and 23 controlled by the same electro-mechanical control device (46; 61) the said flow restrictor member (32). being shaped and disposed in the casing (11, 12) in such a way that its variation in position is such as to cause simultaneously an increase in the flow cross section of the first aspiration passage (28) and a decrease in the flow cross section of the second passage (29, 30).

4. A device according to Claim 3, characterised in that the casing (11, 12) forms a substantially cylindrical cavity (31) communicating with the said chamber (13) and having an end wall (23) in which the said at least one first aspiration passage (28) is formed and an annular wall (22) in which the said at least one second aspiration passage (29, 30) is formed, and in that the flow restrictor member (32) is mounted coaxially and rotatably in the said cavity (31) and has a substantially cylindrical shape with an end wall (32a) and an annular wall (32b) adjacent the corresponding walls (22, 23) of the said cavity (31) and having respective apertures (33; 34, 35) which can be brought into register with the said first and second aspiration passages (28; 29, 30), respectively, in respective predetermined angular positions of the said restrictor member (32).

5. A device according to any preceding Claim, in which the said flow restrictor member (32) is mounted rotatably 24 in the casing (11, 12) and the said electro- mechanical control device comprises a control mechanism (46-51) including a lever (46) mounted pivotally with respect to the casing (11, 12) and coupled to the said flow restrictor member (32); the said lever (46) having a f irst arm (49) connected to a mass (52) operable, when the casing is disposed in a predetermined attitude assumed in use when the door (2) of the machine is closed, to cause rotation in a predetermined sense thereof by gravity and against the action of resilient biasing means (51) to cause a corresponding rotation of the f low restrictor member (32) in a direction which corresponds to increases in the f low cross section of the first aspiration passage (28); an electrically controlled locking/unlocking device (54, 55; 61) being associated with the said lever (46) and operable to retain the said lever (46) in a plurality of successive predetermined angular positions, and to allow the said lever (46) to move by gravity from each of the said angular positions to the next; the said resilient biasing means (51) being prearranged to bias the lever (46) to a predetermined starting position which corresponds to the closure position of the first aspiration passage (28), by the effect of a variation in the attitude of the casing (11, 12) such as to render the action of the said resilient means (51) predominant over the force of gravity acting on the said first arm (49) of the lever (46).

6. A device according to Claim 5, characterised in that the flow restrictor member (32) has a toothed sector (37) which meshes with a corresponding toothed sector (50) carried by a second arm (47) of the said lever (46); this lever (46) being turnable about an axis parallel to the axis of rotation of the said flow restrictor member (32).

7. A device according to Claim 5 or Claim 6, characterised in that to the first arm (49) of the lever (46) are pivoted the ends of adjacent first and second pawls (54, 55) turnable in a plane orthogonal to the plane in which the lever (46) turns and which have different lengths in the direction in which, in operation, the said first arm (49) of the lever tends to move by the effect of gravity; resilient biasing means (57-60) being associated with the said pawls (54, 55), tending to maintain them in a pre-established working plane with respect to the leve r (46); the locking/unlocking device (61) comprising a body (62, 63) which is f ixed to the said casing (11, 12) and adjacent to the said arm (49) of the lever (46), and which has a stop surface (65) which intersects the path which can be followed by the said pawls (54,55) upon turning of the lever (46) when the said pawls are located in the said working plane; the arrangement being such that when the restrictor member (32) is in the closure position of the first passage (28) the longer 26 pawl (54) engages on the said stop surface(65) preventing the said arm (49) of the lever (46) from descending under gravity; and an electrically controlled actuator (67) including a release member (71) movable with respect to the said body (62, 63) and capable of assuming a retracted position in which it does not interfere with the said pawls (54, 55), and an extended position in which it causes the pawl engaging the said stop surface (65) to turn, thereby causing disengagement thereof and allowing the said first arm (49) of the lever (46) to descend under gravity.

8. A device according to Claim 7, characterised in that the said locking/ unlocking device (61) is so arranged that, after disengagement of a pawl (54; 55) from the stop surface (65), the release member (71) is maintained in the extended position for a predetermined period of time in such a way that the other pawl (55) engages against the said release member (71) before reaching the said stop surface (65).

9. A device according to Claim 7 or Claim 8, characterised in that the said actuator (67) iml at last one bimetal strip (69) cooperating with the said release member (71), and an associated resistive heating element (70) operable to cause a deformation thereof such as to cause the release member (71) to move from its retracted 27 to its extended position.

10. A device according to Claim 9, characterised in that the said release member (71) has a biasing spring (72) associated therewith, tending to urge it back into the retracted position.

11. A device according to any of Claims from 7 to 10, characterised in that the said resilient biasing means include at least one leaf spring (57, 59, 60).

12. A device according to any preceding claim, characterised in that the said first aspiration passage (28) has an adjustable shutter (38) associated therewith, moveable with respect to the said casing (11, 12) and manually positionable to any one of a plurality of positions in which it partially closes the said first passage (28).

13. A device according to any preceding claim, characterised in that it further includes sensor means (80) operable to provide electrical signals indicating that the said flow restrictor member (32) is closed.

14. A device according to Claims 5 and 13, characterised in that the said sensor means include a microswitch (80) carried by the said casing (12) and cooperating with an arm (49) of the said lever (46).

4 28 4

15. A device substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.