RU2793244C2 - Filtering device, particularly for heating systems - Google Patents

Abstract

FIELD: filtering.

SUBSTANCE: filtering device (10) includes a housing (11), which forms a flow space (12) for the liquid to be filtered, and which is provided with at least two nozzles (13, 14a, 14b) for connection to the pipe. The space (12) contains a magnetic filtration chamber (15) and a mechanical filtration chamber (16) and contains a flow hole (17) communicating with the magnetic filtration chamber (15), so that the fluid that passes through the space (12) flows through one first (13) of the nozzles (13, 14a, 14b) and flowing out through one second (14a, 14b) of the nozzles (13, 14a, 14b) or vice versa, passes sequentially through both chambers (15, 16). The magnetic filtration chamber (15) contains a magnetic element (18), the working end (19) of which extends towards the flow hole (17). The mechanical filtration chamber (16) contains a strainer. The working end (19) is located at a distance from the flow hole (17), so that the accumulation of particulate material at the working end (19) does not prevent the passage of liquid from the magnetic filtration chamber (15) to the mechanical filtration chamber (16) through the flow hole (17).

EFFECT: increased efficiency of the device, simplification of its maintenance.

9 cl, 4 dwg

Description

The present invention relates to a filtering device, in particular for hydraulic heating systems.

This filter device is particularly adapted to be placed along the pipe of a hydraulic heating system so that the fluid conveyed by the pipe passes through said filter device.

It is known in the specific field of technology to place at least one filter device in heating systems.

The hitherto known filtering device comprises an internal space which communicates with an inlet and an outlet.

Hydraulically, there are two chambers between the inlet and outlet, a first chamber adapted to cause the fluid to cyclonic to separate any heavy particles from the fluid by centrifugal effect, and a second chamber located downstream of the the first chamber, in which a magnetic element and a mesh filter are located, which are adapted to carry out, respectively, the separation of magnetically active particles and mechanical filtration of the liquid.

This known filter device has two disadvantages.

The first disadvantage is that during operation, the accumulation of particles on the surface of the magnetic element causes a decrease in the free cross-section for the flow of liquid, which leads to a decrease in the flow capacity of the filter and, accordingly, the system.

The second disadvantage is the difficulty in performing maintenance.

Indeed, in order to clean the filter, i.e. to remove any particulate material that has accumulated inside the second chamber, mainly as a result of the action of the strainer, but also as a result of the action of the magnetic element, the filter device must be open and the second chamber physically accessible.

To ensure this, the pipe along which the filter is located must be interrupted or the filter itself bypassed.

Thus, the problem underlying the present invention is the problem of improving the efficiency of the filter device and simplifying its maintenance.

Thus, it is an object of the present invention to solve this problem by providing a filtering device that does not significantly adversely affect the hydraulic efficiency of a heating system containing such a device, and whose maintenance is easier than the maintenance of known filtering devices.

In view of this object, one object of the invention is to provide for the removal of particulate material that accumulates inside the filter device without the need to interrupt the pipe along which the filter device is placed, or without bypassing the device itself.

It is another object of the invention to provide a filter device which allows easy removal of particulate material trapped by the strainer without requiring the filter device to be opened.

This objective, as well as these and other objectives which will become more apparent below, are solved by means of a filtering device in accordance with the attached independent claim.

Detailed features of the filter device according to the invention are contained in the dependent claims.

Additional features and advantages of the invention will become more apparent from the description of at least one preferred, but not the only, embodiment of the filter device, shown as a non-limiting example in the accompanying drawings, of which:

Fig. 1 shows a sectional view of a filter device according to the present invention;

Fig. 2 shows the filter device according to Fig. 1 with the magnetic element removed;

Fig. 3 shows an enlarged view of a detail according to Fig. 2;

4 shows the filter device according to the previous drawings in a possible use.

With specific reference to the said drawings, 10 denotes the entire filtering device with a housing 11 which forms a flow space 12 for the liquid to be filtered and is provided with at least two nozzles (connection elements) 13, 14a, 14b for connection with a pipe adapted for placing the latter in fluid communication with space 12.

The filter device 10 may generally comprise only two nozzles, or, to provide two possible arrangements, it may include a first nozzle 13 and two second nozzles 14a and 14b, which can extend from the housing 11 in two directions A and B, which are not parallel.

Thus, the filter device can be connected to the pipe in the first configuration using the first nozzle 13 and one first 14a of the second nozzles 14a and 14b, or in the second configuration with one second 14b - instead of one first 14a - of the second nozzles 14a and 14b.

For example, the direction A of one first 14a of the second pipes 14a and 14b may be parallel and preferably coincides with the direction C of the extension of the first pipe.

The direction B of one second 14b of the second nozzles 14a and 14b may extend at an angle or preferably perpendicular to the extension direction C of the first nozzle.

In such a case, in the first configuration, it is possible to place the filter device in the system using the configuration in line with the pipe, or, in the second configuration, using an L-shaped configuration, connecting it to two pipe lengths so as to form an L shape.

In general, the first valve 100, which may be configured to prevent fluid from flowing out through the second nozzle 14a or 14b to which it is attached, may be associated with said nozzle of the second nozzles 14a or 14b, which will be connected to the pipe. The filter device may form part of a kit that contains the first valve 100, or the first valve may be attached to the second nozzle, or built into the latter if the filter device contains one second nozzle.

Or it can be attached to both second pipes, or built into the latter, in the case when the filter device contains two second pipes, depending on the specific requirements for implementing the present invention.

The space 12 contains a magnetic filtration chamber 15, which communicates with one first 13 of the nozzles 13, 14a, 14b, and a mechanical filtration chamber 16, which communicates with one second 14a and 14b of the nozzles 13, 14a, 14b and which contains a flow hole 17, communicating with the magnetic filtration chamber 15 in such a way that the fluid passes through the space 12, flowing in through one first 13 of the nozzles 13, 14a, 14b and flowing out of one second 14a or 14b from the nozzles 13, 14a, 14b, or vice versa, passes sequentially through both chambers 15 and 16.

The magnetic filtration chamber 15 contains a magnetic element 18, the working end 19 of which extends towards the flow hole 17.

The magnetic element 18 is typically adapted to create a magnetic field within the filtration chamber so as to attract magnetically active particles that may be carried by the fluid flow that passes through the magnetic filtration chamber 15.

The mechanical filtration chamber 16 includes a strainer 20 which divides it into a first part 16a in communication with the flow hole 17 and a second part 16b in communication with the second nozzle 14a and 14b so that the fluid flow passing between the flow hole 17 and the second nozzle 14a or 14b is forced to pass through the strainer 20.

By "mesh filter 20" is meant a filter substantially formed by or comprising a mesh, for example preferably a stainless steel mesh, or a filter formed by a finely perforated element, such as a thin plate, provided with a plurality of holes which can be distributed substantially evenly along its length.

The working end 19 is located at a distance from the flow hole 17 so that the accumulation of material in the form of solid particles at the working end 19 does not interfere with the movement of liquid from the magnetic filtration chamber 15 to the mechanical filtration chamber 16 through the flow hole 17.

For example, along a direction D parallel to the elongation of the flow hole 17, the working end 19 of the magnetic element 18 may be located at a distance d from the flow hole 17.

Said distance d may range, for example, from 1 cm to 3 cm and is preferably 1.5 cm.

Thus, it is ensured that when using the filter device 10, the accumulation of material in the form of magnetically active solid particles attracted by the magnetic element 18 does not cause blockage of the flow hole 17 or reduce its free passage and in particular negatively affect the flow capacity of the filter device 10.

The magnetic filtration chamber 15 may comprise a bottom wall 21 and an outlet 22 which may face the bottom wall 21, wherein the magnetic element 18 may extend between the bottom wall 21 and the working end 19 to the flow hole 17.

An outlet 22 may be provided with or attached to a second valve 200 which may be opened to drain fluid from the magnetic filtration chamber 15.

The outlet 22 extends along the direction G, which may be parallel to the direction A of one first 14a of the second outlets 14a or 14b, in order to always provide access to the outlet 22 when the filter device 10 is located in particular in the boiler.

The housing 11 can be formed from two shells 11a and 11b which complement each other and can be joined together by a connection which can be, for example, bayonet or threaded.

With reference to the accompanying drawings, the aforementioned connection consists, for example, of a threaded connection 11c.

Gaskets may be provided to ensure the tightness of the threaded connection 11c.

The threaded connection 11c may be such that the threads of the upper shell 11a and the threads of the lower shell 11b are aligned so that when the shells 11a and 11b are fixed together, the direction G of the outlet 22 will be substantially parallel to the direction A of one of the first 14a of the second nozzles 14a and 14b.

The second part 16b of the mechanical filtration chamber 16 may include an outlet channel 23.

The filter device 10 may include means for closing the outlet channel 23, which will generally be formed so that they can be actuated from outside the filter device 10 in order to open and close the outlet channel 23.

The filter device 10 will be configured so that after opening the outlet channel 23, the latter will be connected to the magnetic filtration chamber 15 in order to discharge into the latter the material accumulated during the use of the filter device 10 in the second part 16b of the mechanical filtration chamber 16 as a result of filtration by means of a mesh filter 20.

More specifically, housing 11 may include a tubular flange 24 that protrudes into space 12.

The strainer 20 may be formed and positioned within the mechanical filtration chamber 16 so as to form between it and the tubular flange 24 a cavity 25 which contains a bottom opening which defines the outlet channel 23.

In such a case, the second part 16b of the mechanical filtration chamber 16 will comprise a cavity 25.

Said closing means may comprise a closing element 26 which is movable between a closed position in which it closes the outlet 23 and an open position in which the outlet 23 is opened so as to connect the cavity 25 to the magnetic filtration chamber 15.

Said closing element may be provided with an opening or even formed in such a way as to allow the flow of fluid between the magnetic filtration chamber 15 and the first part 16a of the mechanical filtration chamber 15 .

The flange 24 can be made externally in such a way as to cause in the liquid entering the magnetic filtration chamber 15 a cyclonic movement towards the bottom wall 21.

Thus, the separation and settling of particulate material will be provided by centrifugal effect, as is per se known and not described in detail.

If the liquid enters through the first pipe 13, the filtering device 10 can be made in such a way that the liquid, having reached the bottom wall 21, is directed to the flow hole 17 so as to pass into the mechanical filtration chamber 16, moving along the magnetic element 18.

The flange 24 may extend along the extension direction E and the magnetic element 18 may extend along the action direction F (operating direction), which is preferably substantially parallel to the extension direction E.

The filter device 10 is configured to be attached to the hydraulic system pipe so that the direction of extension E is substantially vertical, while the filter device 10 is configured so that the particulate material that has accumulated in the cavity 25 can be discharged by gravitation, through the outlet channel 23 after the opening of the latter, that is, the outlet channel 23 will be made in such a way that when the direction of elongation E is essentially vertical, it runs at least partially vertically.

Meanwhile, the filter device 10 is designed to ensure that it remains operational even when it is attached to the hydraulic pipe so that the extension direction E is substantially horizontal.

The housing 11 may preferably comprise a tubular sleeve 27 which protrudes into the magnetic filtration chamber 15 and forms a cavity 28 for the magnetic element 18.

The cavity 28 will preferably be open on the outside of the housing 11 in order to allow the insertion and removal of the magnetic element 18 without interfering with the operation of the filter device 10.

In use, a magnetic element 18 may be placed within the sleeve 27 to attract and hold onto the latter magnetically active particles.

The magnetic element 18 is preferably retractable from the sleeve 27 in order to release said particles.

The magnetic element 18 may include a cassette shell 29 containing a permanent magnet or a plurality of permanent magnets.

Cassette shell 29 may have a substantially cylindrical shape and contain a lower end, made with the possibility of a strong and releasable connection with the inlet 28a of the cavity 28.

The magnetic element 18 and the sleeve 27 can be made with the possibility of a strong and releasable connection with each other in such a way as to selectively fix the magnetic element 18 in the sleeve 27 or release it and allow it to be removed from the sleeve 27.

For example, bottom end 29a and inlet 28a may be provided with complementary threads and/or each element includes a circular groove so that when bottom end 29a and inlet 28a are connected together, said grooves form a seat for an elastic ring, such as an O-ring. In this case, one of the slots will be occupied by the elastic ring in such a way as to ensure that the lower end 29a is snapped into place with the inlet 28a.

The magnetic filtration chamber 15 may be cylindrical on the inside, and the sleeve 27 may have a cylindrical outer surface coaxial with the magnetic filtration chamber 15.

This solution will be particularly advantageous for optimizing separation efficiency as a result of the cyclonic effect mentioned above in the embodiments of the present invention for which it is intended.

The sleeve 27 may extend from the bottom wall 21 to the flow hole 17, while said closing means may include a movable element 30 connected to the sleeve 27 for movement between a first position and a second position.

The movable element 30 can extend into the sleeve 27, as shown in the accompanying drawings, for example, so as to be driven by the magnetic element 18.

The sleeve 27, the movable element 30 and the magnetic element 18 can be made so that after the introduction of the magnetic element 18 inside the sleeve 27 the movable element 30 will be in the first position, for example, because it is pushed by the working end 19 of the magnetic element 18, and after the magnetic element is removed 18 from the sleeve 27, the movable element 30 will be in the second position.

Said closing means can be made in such a way that when the movable element 30 is in the first position, the outlet 23 is closed, as shown in FIG. 1, and when the movable element 30 is in the second position, the outlet 23 is open, , for example, shown in Fig.2.

The locking element 26 can be movably attached to the movable element 30 with the latter between a closed position in which the movable element 30 is in said first position and an open position in which the movable element 30 is in said second position.

The filter device 10 may further comprise resilient means adapted to exert on the movable element 30 and/or the locking element 26 a force suitable for moving the movable element 30 from the second position to the first position.

In particular, in order to move the aforementioned movable element 30, said closing means may, for example, comprise a spring or other elastic element attached to the housing 11, for example, to the sleeve 27, and acting on the movable element 30 in such a way as to push it into the second position , that is, to counteract its movement to the first position.

In general, the filter device 10 may be configured such that the closing element 26 tends to keep the outlet 23 open when the magnetic element 18 is not in contact with the housing 11.

For example, when the filter device 10 is positioned such that the extension direction E is vertical, the closure element 26 and the movable element 30 may tend to keep the outlet 23 open by gravity acting on the closure element 26 and/or the movable element 30.

The movable element 30 may be slidable, for simplicity preferably in a rectilinear direction, relative to the sleeve 27 along the extension direction E between said first position and said second position; wherein said sleeve 27 extends in said direction F of action.

Alternatively, the opening and closing of the outlet channel 23 can be accomplished by rotating the locking element 26 in a manner not shown in the accompanying drawings.

In this case, the closing element 26 may comprise at least one through hole, which, after rotation of the closing element 26, may be aligned with the outlet 23 in order to open it, or may be offset relative to the outlet 23 in order to close it.

The filtering device can be designed in such a way that the rotation of the closing element 26 for opening or closing the outlet channel 23 can be carried out by means of the magnetic element 18 and, if necessary, by its rotation.

For example, the working end 19 of the magnetic element 18 may be configured to contact directly or indirectly with the locking element 26 in order to rotate it when the magnetic element 18 is located within the cavity 28.

The locking element 26 and the magnetic element 18 may be rotatable about a common axis of rotation, which may be parallel to the extension direction E of the flange 24.

With specific reference to the example of the filter device 10 shown in the accompanying drawings, FIGS. 1 and 4 show two possible alternative configurations suitable for placement based on the aforementioned L-shaped configuration and in-line configuration.

The locking element 26 may be substantially in the form of a disc with a central portion adapted to contact on the inside with the lower, preferably cylindrical, edge of the strainer 20.

Said central portion may be provided with an opening in order to allow liquid to flow from the magnetic filtration chamber 15 into the first part of the mechanical filtration chamber 16 or vice versa.

Around the perimeter of said central area, the closing element may comprise a flange adapted to contact the outlet channel 23 in such a way as to close it.

Below is a description of the possible operation of the filter device 10, connected to the hydraulic system in such a way that the liquid to be filtered flows into the filter device 10 through the first pipe 13 and flows out of one second 14b from the second pipes 14a and 14b.

Obviously, the following description may also be applicable, mutatis mutandis, in the case where liquid flows from one first 14a from the second pipes 14a and 14b, as in the case of the configuration shown in Fig. 4, or in the case when it flows in through one of the second nozzles 14a or 14b and flows out of the first nozzle 13.

In use, the liquid introduced through the first port 13 enters the magnetic filtration chamber 15 and flows along the flange 24, which is preferably cylindrical.

The first nozzle 13 will preferably be axially offset relative to the flange 24 so as to force the liquid to move along the flange 24 in a circular motion, descending towards the bottom wall 21 so as to cause the aforementioned cyclonic movement.

As a result of this cyclonic movement, any heavy particles carried by the fluid flow will tend to accumulate first on the peripheral walls of the magnetic filtration chamber 15 and then sink to accumulate on the bottom wall 21.

When the liquid reaches the bottom wall 21, it will tend to move up the center around the magnetic element.

Any magnetically active particles will tend to stick to the outer surface of the sleeve 27 under the force of attraction exerted by the magnetic element 18.

The liquid will then enter a mechanical filtration chamber 16 where it will pass through a strainer 20 which will remove particles larger than the through holes of the strainer 20.

In order to clean the filter device 10, it is sufficient to close the first valve 100 to prevent liquid from flowing out of the filter device 10 towards the system to which it is connected.

As a result of this closing operation, the particles that have accumulated on the inner surface of the strainer 20 will tend to fall into the magnetic filtration chamber 15 and settle on the bottom wall 21 of the latter.

After removing the magnetic element 18, particles that have accumulated on the outer surface of the sleeve 27 will tend to separate from it and collect on the bottom wall 21.

In order to remove the particulate material that has accumulated inside the magnetic filtration chamber 16, it will be sufficient to open the second valve 200 so that the liquid flowing from the outlet 22 carries away with it the particles to be removed.

In addition, the hydrodynamic effect of the effluent will also tend to remove any particulate material still adhering to the sleeve 27 and/or the bottom wall 21 and/or other parts of the space 12.

In addition, upon removal of the magnetic element 18, the locking element 26 will open the exit channel 23, allowing any particles that have accumulated inside the cavity 25 to enter the magnetic filtration chamber 15, as shown, for example, by the dotted arrow in FIG.

In particular, in the case of operation in the opposite direction as described herein, i.e. when fluid enters through one of the second nozzles 14a and exits the first nozzle 13, there will be a significant accumulation of particles inside the cavity 25, which during cleaning (when the first valve - in this case associated with the first nozzle 13 - will be closed) will be discharged into the magnetic filtration chamber 15 as a result of the opening of the outlet channel 23 after the locking element 26 has moved to the open position due to the removal of the magnetic element 18. Thus, when the outlet 22 open, the particles released from the cavity 25 through the outlet channel 23 will also be removed.

Thus, it is shown how the present invention is able to achieve the stated object and purpose.

In fact, with the filter device according to the present invention, it is possible to have a three-dimensional magnetic filtration chamber, without any mesh filter, inside which particulate material can accumulate without obstructing the flow of liquid through the filter device.

The filter device according to the invention not only can be easily connected in an L-configuration or in-line configuration to a hydraulic system, but can also be used in two opposite possible directions of fluid flow, i.e. from the first nozzle to one of the second nozzles or vice versa, without affecting its flow capacity.

In particular, the filter device according to the present invention will also be easy to clean even for an unskilled user, because it does not need to be opened, but simply use the aforementioned valves and remove, if necessary, the magnetic element, as described in more detail above.

Thus, the simple design of the filter device according to the invention is such that the device can be manufactured simply using known plastic injection techniques and through a simple and convenient assembly operation.

The invention thus conceived may be susceptible to many modifications and variations, all of which are within the scope of the appended claims.

In addition, all parts can be replaced by other technically equivalent elements.

In practice, the materials used, as well as the corresponding shapes and dimensions, can be changed depending on specific requirements and the state of the art.

Where the design features and techniques referred to in the following claims are accompanied by symbols or reference numerals, these reference numerals or symbols are provided for the sole purpose of facilitating the understanding of said claim and, therefore, they in no way limit the interpretation of each element that is indicated, only by way of example, by means of the reference numerals or symbols mentioned.

Claims (14)

1. A filtering device (10) for filtering a liquid, comprising a housing (11) forming a flow space (12) for the liquid to be filtered and equipped with at least two connection elements (13, 14a, 14b) for connecting to a pipe, made with the possibility arranging the pipe in fluid communication with space (12); moreover, the space (12) contains a chamber (15) of magnetic filtration, which communicates with one of the first (13) of the elements (13, 14a, 14b) of the connection, and a chamber (16) of mechanical filtration, which communicates with one second (14a, 14b) of the connection elements (13, 14a, 14b) and which contains a flow hole (17) communicating with the magnetic filtration chamber (15) in such a way that the fluid that passes through the space (12) flows through one first (13) of connection elements (13, 14a, 14b) and flowing from one second (14a, 14b) of the connection elements (13, 14a, 14b) or vice versa, passes sequentially through both chambers (15, 16); moreover, the magnetic filtration chamber (15) contains a magnetic element (18), the working end (19) of which extends towards the flow hole (17), and the magnetic element (18) is configured to create a magnetic field inside the magnetic filtration chamber (15); moreover, the chamber (16) of mechanical filtration contains a mesh filter (20), which divides it into the first part (16a), which communicates with the flow hole (17), and the second part (16b), which communicates with the second element (14a, 14b) of the connection, so that the fluid flow passing between the flow hole (17) and said connection element passes through the strainer (20); moreover, the working end (19) is located at a distance from the flow hole (17), so that the accumulation of material in the form of solid particles at the working end (19) does not prevent the flow of liquid from the magnetic filtration chamber (15) into the mechanical filtration chamber (16) through the flow hole (17), characterized in that the magnetic filtration chamber (15) contains a bottom wall (21), an outlet pipe (22), which faces the bottom wall (21), while the magnetic element (18) passes between the bottom wall (21 ) and the working end (19) to the flow hole (17); moreover, the second part (16b) of the mechanical filtration chamber (16) contains an outlet channel (23), and the filter device (10) contains a means for closing the outlet channel (23), which is configured to be controlled from outside the filter device to open and close the outlet channel (23); moreover, after opening the outlet channel (23), it is connected to the magnetic filtration chamber (15) to discharge into it the material accumulated in the second part (16b) of the mechanical filtration chamber (16) after being filtered by the strainer (20). 2. The device (10) according to claim 1, in which the housing (11) contains a tubular flange (24) protruding into the space (12); moreover, the mesh filter (20) is located inside the mechanical filtration chamber (16) to form a cavity (25) between it and the tubular flange (24) containing a lower opening that forms the outlet channel (23); wherein the second part (16b) of the mechanical filtration chamber (16) contains said cavity (25); moreover, the closing means comprises a locking element (26), which is movable between a closed position, in which it locks the outlet channel (23), and an open position, in which the outlet channel (23) connects the cavity (25) with the chamber (15) magnetic filtration. 3. The device (10) according to claim 2, in which the flange (24) extends along the extension direction (E), and the magnetic element (18) extends along the operating direction (F), which is essentially parallel to the extension direction (E); wherein the filter device (10) is configured to be attached to a hydraulic system pipe such that the direction (E) of elongation is substantially vertical, the filter device (10) being configured such that the particulate material that has accumulated inside the cavity (25) , can be released by gravity through the outlet channel (23) after it has been opened. 4. Device (10) according to any one of claims 1 to 3, in which the housing (11) comprises a tubular sleeve (27) protruding into the magnetic filtration chamber (15) and forming a cavity (28) for the magnetic element (18), which open on the outer side of the housing (11); moreover, the magnetic element (18) is located inside the sleeve (27) for attracting and holding magnetically active particles on it, and the magnetic element (18) is made with the possibility of being removed from the sleeve (27) for the release of particles. 5. The device (10) according to claim 4, in which the sleeve (27) extends from the bottom wall (21) towards the flow hole (17); moreover, the closing means contains a movable element (30) attached to the sleeve (27) with the possibility of moving between the first position and the second position; moreover, the movable element (30) passes into the sleeve (27) for its drive through the magnetic element (18); moreover, the sleeve (27), the movable element (30) and the magnetic element (18) are designed so that after the introduction of the magnetic element (18) inside the said sleeve (27), the movable element (30) is in the first position, and after the removal of the magnetic element (18) from the sleeve (27) the movable element (30) is in the second position; moreover, the closing means is designed so that when the movable element (30) is in the first position, the outlet channel (23) is closed, and when the movable element (30) is in the second position, the outlet channel (23) is open. 6. The device (10) according to claim 5, in which the locking element (26) is attached to the movable element (30) with the possibility of moving with it between the closed position, in which the movable element (30) is in the first position, and the open position , in which the movable element (30) is in the second position. 7. The device (10) according to claims 3 and 6, in which the movable element (30) is configured to move relative to the sleeve (27) along the extension direction (E) between the first position and the second position; wherein the sleeve (27) extends in the working direction (F). 8. The device (10) according to any one of claims 6, 7, which further comprises an elastic means adapted to exert on the movable element (30) and/or on the locking element (26) a force suitable for moving the movable element (30) out of second position to first position. 9. The device (10) according to claim 8, in which the magnetic element (18) and the sleeve (27) are made with the possibility of a stable releasable connection with each other to selectively fix the magnetic element (18) inside the sleeve (27) or release it to provide the possibility of its extraction from the sleeve (27).

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