AUTOMATIC RESTRICTOR FOR A CONDUIT

Description

The present invention relates to an automatic restrictor for a conduit.

The invention is particularly effective in combination with a device that envisages the mixing of two fluids in a determined stretch of a conduit.

For example, the automatic restrictor according to the present invention can be used in the lance of a high pressure water jet cleaner, for allowing the mixing of water and detergent.

High pressure water jet cleaners comprise a supply pump that supplies water under pressure to a lance, which can be manoeuvred by an operator, equipped with a dispensing nozzle for dispensing the liquid. The dispensing nozzle is provided for changing the size of the water outlet opening between a minimum amplitude configuration, in which the water is dispensed at high pressure, and a maximum amplitude configuration, in which the water is dispensed at low pressure. For example, the nozzle comprises an outlet opening of limited amplitude, for dispensing water at high pressure, and a plurality of further outlet openings, which are closed during high pressure operation, and are only opened when low pressure dispensing is required, typically for dispensing a detergent liquid.

As is known, the detergent liquid is mixed with water upstream of the dispensing nozzle. For that purpose, a mixing device is used that is interposed between the supply pump and the dispensing nozzle.

The mixing device comprises a conduit equipped with a restriction conformed as a Venturi tube. A suction conduit, connected to a tank of detergent liquid, is connected prior to the diverging stretch of the Venturi tube. A shut-off valve, normally closed, is arranged along the suction conduit. Such shut-off valve is provided to open automatically due to the effect of a determined depression that is created prior to the diverging stretch of the Venturi tube.

In particular, when the dispensing nozzle is activated for low pressure dispensing, the depression that is created prior to the diverging stretch of the Venturi tube produces the opening of the shut-off valve and the consequent suction of the detergent liquid from the suction conduit. The detergent liquid is mixed with the water coming from the pump.

When the dispensing nozzle is activated for high pressure dispensing, the depression that is created prior to the diverging stretch of the Venturi tube is not sufficient to cause the opening of the shut-off valve, therefore the detergent liquid is not sucked and only water is dispensed.

In mixing devices of this kind, the water directed towards the dispensing nozzle always tends to cross the Venturi tube, both during high pressure dispensing, and during low pressure dispensing, hence undergoing consistent load losses that cause huge energy losses.

To overcome the drawback summarised above, the Applicant has designed a mixing device which, under high pressure operating conditions, allows the Venturi tube to be by-passed, substantially without changing the structure of the lance or the dispensing nozzle.

Such mixing device, described in Italian patent 1406219, comprises a main conduit that has a restriction configured as a sudden section change. In substance, the main conduit has an internal shoulder that reduces its diameter. The stretch of the main conduit downstream of the restriction is diverging. The suction conduit of the detergent liquid opens into the main conduit prior to the diverging stretch thereof, in proximity to the restriction.

An automatic restrictor is arranged inside the main conduit. Such automatic restrictor is in turn provided with an internal conduit equipped with a restriction. The stretch downstream of the restriction has a reduced diameter with respect to the stretch upstream and is provided with an outlet end that opens onto a head surface of the restrictor. The diameter of such outlet end is smaller than the diameter of the restriction of the main conduit.

The restrictor is movable between an active position, in which its head surface is in contact with the shoulder of the main conduit and the outlet end of its internal conduit faces the restriction of the main conduit, and an inactive position, in which its head surface is detached from the shoulder of the main conduit.

When the restrictor is in the active position, the water that flows along the main conduit is forced to pass through the internal conduit of the restrictor and, from there, through the restriction of the main conduit. Overall, the internal conduit of the restrictor, the restriction and the diverging stretch of the main conduit define a Venturi tube. Consequently, prior to the diverging stretch of the main conduit, a depression is created that allows the suction of the detergent liquid through the suction conduit.

When the restrictor is in the inactive position, the water that flows along the main conduit is free to pass both around the restrictor, i.e. into the gap defined between the restrictor and the main conduit, and through the restriction of the main conduit. Under such conditions, the water is therefore not forced to pass only through the internal conduit of the restrictor, and therefore undergoes load losses which are substantially lower with respect to the condition in which the restrictor is in the active position and the water is forced to pass through the internal conduit of the restrictor.

An elastic means, for example a spring, pushes the restrictor towards the inactive position. Under high pressure dispensing conditions, the pressure difference established along the main conduit between the stretch upstream and the stretch downstream of the restriction is lower with respect to the pressure difference established in low pressure operation. In this way, by appropriately calibrating the thrust exerted by the spring that acts on the restrictor, it is possible, in low pressure operation, for the restrictor to be shifted and maintained in the active position, by effect of the thrust due to the aforementioned pressure difference. In high pressure operation, the restrictor is shifted into the inactive position, due to the effect of the thrust exerted by the spring that is sufficient to overcome the thrust due to the aforementioned pressure difference. The restrictor therefore has an automatic operation, since it moves between the active position and the inactive position in reaction to the activation of the dispenser between low and high pressure. Further characteristics and advantages of the present invention will become more apparent in the following detailed description of an embodiment of the present invention, illustrated by way of non-limiting example in the attached figures, in which:

- figure 1 is a lateral section view of the device in the active condition (low pressure);

- figure 2 is an enlargement of a zone of figure 1 ;

- figure 3 is a lateral section view of the device in the inactive condition (high pressure);

- figure 4 is an enlargement of a zone of figure 3.

The figures illustrate the mixing device (1 ) according to the present invention used in a high pressure water jet cleaner. The mixing device could however be used in machines of a different type.

The high pressure water jet cleaner comprises a supply pump (P), provided to draw water from a tank or from a water network. The machine further comprises a dispensing nozzle (N), which is placed downstream of the supply pump itself and is arranged at the end of the lance that can be manoeuvred by an operator. In a known way, and therefore described in detail, the nozzle (N) can be activated between a low pressure configuration, for dispensing water at low pressure, and a high pressure configuration, for dispensing water at high pressure. Generally, in the high pressure configuration, the nozzle (N) has a rather reduced outlet section with respect to the low pressure configuration.

The mixing device according to the present invention can be arranged downstream of the supply pump (P) and upstream of the dispensing nozzle (N).

The mixing device comprises a main conduit (20), which comprises a first stretch (21 ) and a second stretch (22). A restriction (23) is interposed between the first stretch (21 ) and the second stretch (22).

In the embodiment represented, the main conduit (20) is afforded within a main body (B) and is equipped with a longitudinal axis (Y). For clear and known construction and assembly needs, the main body (B) is split into at least two portions, in particular a first portion, which comprises the second stretch (22) of the main conduit (20), is associated with a second portion provided for the connection to the pump (P). The first stretch (21 ) of the main conduit (20) is delimited by both portions. In the following description, reference will however be made, in short, to a single body (B) without wishing to exclude an embodiment in which the body (B) is made of two or more parts connected to one another.

The restriction (23) substantially comprises a shoulder internal to the main conduit (20), which separates the first stretch (21 ) and the second stretch (22). The second stretch (22) has a smaller diameter than the first stretch (21 ). Not necessarily, the second stretch (22) can have an increasing internal section, or be diverging, moving away from the restriction (23).

The first stretch (21 ) can be placed in communication with the pump (P), while the second stretch (22) can be connected to the nozzle (N).

The mixing device (1 ) further comprises a suction conduit (30), connected to the second stretch (22) of the main conduit (20). The suction conduit (30) can be afforded through the main body (B).

The suction conduit (30) is provided to allow the suction of a second liquid or fluid, for example a detergent product, which can be contained in a relevant tank, preferably at ambient pressure.

The suction conduit (30) can be equipped with a shut-off valve (31 ). Such shut-off valve (31 ) is provided to assume an opening configuration following the determination of a lower pressure in the second stretch (22) with respect to a determined reference value. For that purpose, the shut-off valve (31 ) comprises a housing (32) and a shutter (33). The shutter (33), for example in the form of a ball, is kept in contact with the housing (32) by an elastic means (34), for example a spring, so as to close the communication between the suction conduit (30) and the tank (T) of the second fluid. The shutter (33) can be pushed away from the housing (32) due to the effect of the pressure difference between the tank (T) and the second stretch (22), in particular due to the effect of a pressure drop in the second stretch (22).

The mixing device (1 ) further comprises a restriction adjuster (40), inserted in the main conduit (20). The restriction adjuster (40) is configured to vary the passage area available for the flow, as a function of the pressure difference between the first stretch (21 ) and the second stretch (22) of the main conduit (20).

In particular, in a high pressure water jet cleaner, the adjuster (40) is configured to reduce the passage section of the first stretch (21 ) so as to determine, by Venturi effect, a reduction in the pressure of the water transiting through the restriction (23). Such pressure reduction can be used to produce the opening of the shut-off valve (31 ).

For example, the adjuster (40) is configured so as to vary the amplitude of the passage opening of the first stretch (21 ) following a configuration change of the nozzle (N) between high or low pressure, i.e. as a consequence of a variation in the pressure difference established between the first stretch (21 ) and the second stretch (22). In particular, the adjuster (40) is configured so as to enlarge the passage opening of the first stretch (21 ), through the restriction (23), when the nozzle (N) is in the high pressure configuration, vice versa so as to reduce the passage opening of the first stretch (21 ), through the restriction (23), when the nozzle (N) is in the low pressure configuration. For that purpose, the adjuster (40) comprises a through internal conduit

(41 ) that has an outlet stretch (42). Such outlet stretch (42) has a smaller diameter with respect to the internal conduit (41 ). The variation in diameter between the internal conduit (41 ) and the outlet stretch (42) is completed in a short stretch, so that between the internal conduit (41 ) and the outlet stretch

(42) a restriction is defined. The outlet stretch (42) opens onto a head surface

(43) of the adjuster (40).

The internal conduit (41 ) is also provided with at least one inlet opening (44) arranged on a lateral surface (45) of the adjuster (40), so that the flow can enter into the internal conduit (41 ). The adjuster (40) is inserted into the main conduit (20) with a prefixed guide clearance and has a shape such as to create a fluid passage gap around the adjuster (40).

The adjuster (40) is movable between an active position (figures 1 and 2), in which the head surface (43) is in contact with the restriction (23) and the outlet stretch (42) of the internal conduit (41 ) faces the second stretch (22) of the main conduit (20), and an inactive position (figures 3 and 4), in which the head surface (43) is distanced from the restriction (23).

In the active position of the adjuster (40), the flow is forced to pass through the internal conduit (41 ), the outlet stretch (42), the restriction (23) and the second stretch (22) of the main conduit. Therefore, by Venturi effect, a pressure drop occurs in the second stretch (22).

In the inactive position of the adjuster (40), the flow is also free to pass into the gap that surrounds the adjuster (40), and from there through the restriction (23), which has a larger diameter than the outlet stretch (42), hence undergoing a much less significant pressure drop with respect to what happens with the adjuster (40) in the active position.

Preferably, but not necessarily, an elastic means (50) is provided for pushing the adjuster (40) from the active position towards the inactive position. Such elastic means (50), for example in the form of a spring, can be interposed between the restriction (23) and the adjuster (40).

The adjuster (40) is movable between the active position and the inactive position due to the effect of the pressure difference between the first stretch (21 ) and the second stretch (22) of the main conduit (20). In the high pressure water jet cleaner, the difference between the pressure in the first stretch (21 ) and the pressure in the second stretch (22) is lower when the dispensing nozzle (N) is configured for high pressure dispensing with respect to when the nozzle (N) is configured for low pressure dispensing.

Therefore, when the nozzle (N) dispenses at low pressure, the adjuster (40) is pressed in the active position by the pressure difference between the first stretch (21 ) and the second stretch (22) of the main conduit (20). When, instead, the nozzle (N) dispenses at high pressure, the adjuster (40) is pushed into the inactive position by the elastic means (50), whose thrust is higher with respect to the thrust due to the pressure difference between the first stretch (21 ) and the second stretch (22) of the main conduit (20).

As already highlighted, in the active position of the adjuster (40) the head surface (43) is in contact with the restriction (23) and the outlet stretch (42) of the internal conduit (41 ) faces the second stretch (22) of the main conduit (20). The outlet stretch (42) also has a lower section with respect to the restriction (23). This produces, in the flow, a pressure drop by Venturi effect, which allows the second liquid to be sucked through the suction conduit (30).

Advantageously, the adjuster (40) comprises at least one auxiliary opening (46) for the passage of fluid, arranged on the lateral surface (45), in proximity to the head surface (43). Such auxiliary opening (46) opens onto the internal conduit (41 ), defining a communication pathway between the internal conduit (41 ) and the first stretch (21 ) of the main conduit (20).

The auxiliary opening (46) allows the load losses that the flow undergoes when the adjuster (40) is in the inactive position to be reduced further. In fact, the available section for the passage of the flow increases the auxiliary opening section (46). In substance, the passage sections available for the flow are, in addition to the gap that surrounds the adjuster (40) and the outlet stretch (42), also the auxiliary opening (46) through which a portion of the flow can transit in the first stretch (21 ) and in the space between the restriction (23) and the head surface (43).

Preferably, but not necessarily, the auxiliary opening (46) is arranged between the internal conduit (41 ) and the outlet stretch (42). Such positioning allows the load losses undergone by the flow to be further reduced.

The mixing device according to the present invention can further be equipped with a maximum pressure and flow rate adjustment valve (60). Such valve (60) is interposed between the main conduit (20) and a discharge opening (24) and is provided to assume an opening configuration, in which it places the main conduit (20) in communication with the discharge opening (24), if the pressure in the main conduit (20) exceeds a pre-fixed threshold value.

Such valve (60) comprises a sealing housing (61 ) afforded in the body (B) of the device. The sealing housing (61 ) is interposed between a discharge opening (24) and the main conduit (20), or a supply conduit to the first stretch (21 ).

The valve (60) further comprises a shutter (62), conformed for example like a spherical or conical cap, conformed to be arranged in contact with the housing (61 ) so as to close the communication between the discharge opening (24) and the main conduit (20). In particular, the shutter (62) is movable between a closed position, in which it is pressed against the housing (61 ), and an open position, in which it is distanced from the housing (61 ).

The shutter (62), through a stem, is connected to a plate (63), movable sealingly within a piloting chamber (64). Such piloting chamber (64) is placed in communication with the main conduit (20) by means of a piloting conduit (65), afforded in the body (B) of the device. In this way, the plate (63) is subject to the pressure present within the main conduit (20).

An adjustable spring (66) is arranged in contact with the plate (63), on the opposite side with respect to the piloting chamber (64). In this way, the adjustable spring pushes the shutter (62) towards the closing position. In a known way, the thrust exerted by the spring on the plate (63) can be adjusted through a screw abutment (67), placed in contact with the other end of the spring (66).

For the activation of the maximum pressure valve (60), the adjuster (40) comprises, at the axial end opposite the head surface (43), a sealing portion (47), conformed to be arranged in contact with a bottom wall (26) of the main conduit, placed upstream of the outlet of the by-pass conduit (65) with respect to the direction of the flow.

Thanks to the presence of the sealing portion (47), the adjuster (40) is able to close the main conduit (20) in the case in which, in the main conduit itself, a pressure peak occurs, due, for example, to the closure of the nozzle (N), or to the change from low pressure dispensing to high pressure dispensing. Under such conditions, the adjuster (40) is pushed backwards, towards the bottom wall (26). The sealing portion (47) occludes the main conduit (20), so that the pressure peak, through the by-pass conduit (65) is transmitted to the piloting chamber (64) and to the plate (63). If the thrust on the plate (63) exceeds the thrust exerted by the spring (66), the shutter (62) comes detached from the housing (61 ), so that the flow arriving at the main conduit (20) is discharged at the outlet through the discharge opening (24).

The operation of the mixing device according to the present invention takes place as follows.

By operating the nozzle (N) in the low pressure configuration, the pressure difference between the first stretch (21 ) and the second stretch (22) of the main conduit (20) is such as to push the adjuster (40) into the active position. As already underlined, in such configuration, the flow is forced to pass through the internal conduit (41 ) and the outlet stretch (42) of the adjuster (40). By Venturi effect, at the outlet of the outlet stretch (42) and in the passage through the restriction (23), the flow undergoes a pressure loss which causes the suction of the second liquid (detergent) through the suction conduit (30). Therefore a mixture of water and detergent arrives at the nozzle (N).

During low pressure operation, the maximum pressure and flow rate adjustment valve (60) remains closed, since the spring (66) is adjusted so as to exert a sufficient thrust to keep the shutter (62) in a closed position. All the flow rate dispensed by the pump (P) therefore reaches the nozzle (N).

By operating the nozzle (N) in the high pressure configuration, the pressure difference between the first stretch (21 ) and the second stretch (22) of the main conduit (20) is lower with respect to the same pressure difference that occurs during low pressure operation. Therefore, the adjuster (40) is pushed towards the inactive position, but without reaching the bottom wall (26) of the main conduit (20). The flow coming from the pump (P) therefore passes through the first stretch (21 ) of the main conduit (20), through the gap that surrounds the adjuster (40), the opening or auxiliary openings (26) and the space between the head surface (43) and the restriction (23), the outlet stretch (42) of the adjuster (40) and the restriction (23), for reaching the second stretch (22) of the main conduit (20). As already outlined, the presence of the opening or auxiliary openings (26) allows the load losses suffered by the flow to be drastically reduced, with respect to what happens in mixing devices of the known type. The restriction offered overall by the flow passage sections, under these conditions, is such as to produce a modest pressure drop, that is not sufficient to cause the opening of the shut-off valve (31 ).

With the nozzle (N) in the high pressure configuration, the pressure within the first stretch (21 ) of the main conduit increases, as does the pressure within the piloting chamber (64). The spring (66) can be adjusted so as to balance the thrust produced by the pressure in the piloting chamber (64). In this way, the shutter (62) is detached partially from the housing (61 ), allowing the outflow of part of the flow rate dispensed by the pump (P). The position of the shutter (62) oscillates moving away from and towards the housing (61 ), adjusting the flow rate that flows out through the discharge opening (24) as a function of the flow rate dispensed by the pump (P) and the degree of opening of the nozzle (N).

In the case in which the operator, by acting on the opening control of the hydraulic lance, interrupts the flow at the outlet from the dispensing nozzle (N), the consequent increase in pressure in the piloting conduit (20) makes the adjuster (40) move back, coming into contact with the bottom wall (26) of the main conduit, in this way causing the opening of the shutter (62), in the ways already described. The activation of the valve (60) could also be obtained through a different piloting element, distinct from the adjuster (40).