WO2020250122A1

WO2020250122A1 - Fluid-operated device

Info

Publication number: WO2020250122A1
Application number: PCT/IB2020/055400
Authority: WO
Inventors: Paolo Sprega
Original assignee: SPREGA, Matteo; SPREGA, Alessandro
Priority date: 2019-06-11
Filing date: 2020-06-09
Publication date: 2020-12-17
Also published as: EP3983686A1

Abstract

The fluid-operated device (1) comprises: one work assembly (53) supplied by one work fluid and provided with: - one liner (3); - one stem (2) coupled in a sliding manner inside the liner (3) and defining with the latter a thrust chamber (4) for the movement of the stem (2) with respect to the liner (3) longitudinally along a direction of movement (A); at least one sensing device (55, 55a, 55b) provided with one sensing element (5) configured to detect without contact the presence of the stem (2); wherein the sensing device (55, 55a, 55b) comprises interaction means (54) movable without contact by the passage of the stem (2) between at least one home configuration, wherein the sensing element (5) detects one of the presence and the absence of the stem (2), and one active configuration, wherein the sensing element (5) detects the other of the presence and the absence of the stem (2).

Description

FLUID-OPERATED DEVICE

Technical Field

The present invention relates to a fluid- operated device.

Background Art

Several fluid- operated devices are known to be used in various technical fields for the transmission of motion.

Generally, the fluid- operated devices of known type comprise a work assembly provided with a liner and a stem inserted at least partly inside the liner and coupled to the latter in a sliding manner between at least one pair of opposite end-of-stroke extremes defining the maximum stroke of the stem with respect to the liner.

Very frequently, the machines or the systems using this type of fluid- operated devices need to monitor the position of the stem with respect to the liner, e.g. to ensure the correct operation of these machines or systems.

In this regard, the known fluid- operated devices are provided with means for detecting the position of the stem with respect to the liner.

Generally, these fluid- operated devices of known type comprise sensing means provided with at least one reference element associated with the stem at a preset position and at least one sensor element associated with the liner at one end-of- stroke extreme and adapted to detect the presence/absence of the reference element.

This way, depending on the preset position at which the reference element is arranged, the position of the stem with respect to the liner may be determined. Generally, with reference to this type of sensing means, the use of magnetic, inductive, optical sensors or the like is known so that the reference element associated with the stem can be detected without contact.

This way, the sensing means do not interfere in any way with the sliding of the stem inside the liner.

However, the fluid-operated devices of this type are subject to improvements related to the detection accuracy of the position of the stem with respect to the liner. In fact, with particular reference to the applications for which a particularly high stem movement speed is required, the sensor element does not always detect the reference element with the desired precision.

In fact, in these cases, the reference element stimulates the sensor element for an extremely limited time and does not always allow the correct recognition of the stem position with respect to the liner.

This drawback is also further increased by the number of reference elements associated with the stem and the distance between them, e.g. to detect a plurality of mutually close positions of the stem with respect to the liner.

In fact, the sudden sequence of two reference elements in the proximity of the sensor element is frequently detected as the passage of a single reference element, resulting in a non-negligible degree of uncertainty about the real position of the stem with respect to the liner.

In addition, the sensor elements only allow conveying status signals and therefore need to be operationally connected to signal control systems configured to interpret the status signals and consequently carry out one or more preset operations.

This approach, however, is particularly complex, as it complicates the installation operations of the sensor element and adversely affects the operation of the fluid- operated device in conjunction with the machines or systems that employ such devices.

The aforementioned drawbacks make the fluid- operated devices of known type particularly complex and imprecise and significantly limit their fields of application with a consequent limitation in the market and sales.

Description of the Invention

The main aim of the present invention is to devise a fluid- operated device that allows detecting without contact and with greater reliability one or more predefined stem positions with respect to the liner with respect to the fluid- operated devices of known type.

A further object of the present invention is to devise a fluid- operated device that allows the structure of the device itself to be considerably simplified with respect to the devices of known type.

An additional object of the present invention is to devise a fluid- operated device that allows directly conveying the power signals.

Another object of the present invention is to devise a fluid- operated device that allows to overcome the above mentioned drawbacks of the prior art within a simple, rational, easy, effective to use and affordable solution.

The objects set out above are achieved by the present fluid- operated device having the characteristics of claim 1.

Brief Description of the Drawings

Other characteristics and advantages of the present invention will be more evident from the description of some preferred, but not exclusive, embodiments of a fluid-operated device, illustrated by way of an indicative, yet non-limiting example, in the attached tables of drawings in which:

Figure 1 is a sectional view of a device embodiment according to the invention in a first configuration of work;

Figure 2 is a sectional view of the device embodiment shown in Figure 1 in a second configuration of work;

Figure 3 is a sectional view of a component of the device embodiment shown in Figures 1 and 2;

Figure 4 is a sectional view of a device embodiment variant shown in Figures 1 and 2;

Figure 5 is an exploded view of a detail of the device shown in Figure 4;

Figure 6 is a view of a device component shown in Figures 4 and 5;

Figure 7 is a sectional view of the component shown in Figure 6;

Figure 8 is a sectional view of a component embodiment variant shown in Figure 7;

Figure 9 is a sectional view of a variant of the device embodiment shown in Figure 4;

Figure 10 is a sectional view of a component of the device embodiment variant shown in Figure 9;

Figure 11 is a sectional view of a further variant of the device embodiment shown in Figures 1 and 2;

Figure 12 is a sectional view of a further embodiment of the device according to the invention;

Figure 13 is a sectional view of a variant of the device embodiment shown in Figure 12;

Figure 14 is a sectional view of a variant of the device embodiment shown in Figure 12;

Figure 15 is a sectional view of an additional embodiment of the device according to the invention;

Figure 16 is a sectional view of a component of the device embodiment shown in Figure 15 in the home configuration;

Figure 17 is a sectional view of the component shown in Figure 16 in the active configuration;

Figure 18 is a sectional view of an additional embodiment of the device according to the invention;

Figure 19 is a sectional view of a component of the device embodiment shown in Figure 18 in the home configuration;

Figure 20 is a sectional view of the component shown in Figure 19 in the active configuration.

Embodiments of the Invention

With particular reference to these figures, reference numeral 1 globally indicates a fluid- operated device.

The fluid- operated device 1 comprises:

at least one work assembly 53 supplied by at least one work fluid and provided with:

at least one liner 3;

at least one stem 2 coupled in a sliding manner inside the liner 3 and defining with the latter a thrust chamber 4 of the work fluid for the movement of the stem 2 with respect to the liner 3 longitudinally along a direction of movement A;

at least one sensing device 55, 55a, 55b associated with the liner 3 at a predefined position and provided with at least one sensing element 5 configured to detect without contact the presence/absence of the stem 2 in the proximity of the predefined position.

Preferably, the work assembly 53 is of the type of a pneumatic or hydraulic member of a type known to the expert in the field, such as e.g. a pneumatic or hydraulic stem/piston pair.

Advantageously, the sensing device 55, 55a, 55b comprises interaction means 54 interposed between the sensing element 5 and the stem 2 and movable without contact by the passage of the stem 2 between at least one home configuration, wherein the sensing element 5 detects one of either the presence or the absence of the stem 2 at the predefined position, and at least one active configuration, wherein the sensing element 5 detects the other of either the presence or the absence of the stem 2 at the predefined position.

In particular, the interaction means 54 comprise at least one sliding chamber 6 and at least one sliding body 7 inside the sliding chamber 6.

In addition, in the home configuration, the sliding body 7 is moved close to the sensing element 5, which detects at least one of either the presence or the absence of the stem 2, and, in the active configuration, it is moved away from the sensing element 5, which detects the other of either the presence or the absence of the stem 2.

Advantageously, the sliding chamber 6 faces the thrust chamber 4 without trespassing upon it.

In addition, conveniently, the sliding chamber 6 is interposed between the thrust chamber 4 and the sensing element 5.

In addition, the interaction means 54 comprise magnetic means 15, 16, 47, 51, 58 associated integral in translation with the sliding body 7 and adapted to operate in conjunction with the stem 2 to move the interaction means 54 between the home configuration and the active configuration.

In fact, the stem 2 comprises at least one reference element 57 adapted to operate in conjunction with the magnetic means 15, 16, 47, 51, 58 to move the interaction means 54 between the home configuration and the active configuration.

In particular, the magnetic means 15, 16, 47, 51, 58 may be forced back or attracted by the stem 2 and consequently cause the sliding body 7 to move inside the sliding chamber 6.

This way, the interaction means 54 are moved between the home configuration and the active configuration.

In addition, the interaction means 54 comprise at least one resilient element 8 interposed between the sliding chamber 6 and the sliding body 7.

In particular, the resilient element 8 is loaded when the interaction means 54 are in one of either the home configuration or the active configuration, bringing the latter back into the other of either the home configuration or the active configuration.

Conversely, the resilient element 8 is unloaded when the interaction means 54 are in the other of either the home configuration or the active configuration, maintaining the interaction means 54 in the same configuration.

Preferably, the sliding chamber 6 defines a sliding channel 59 inside which the sliding body 7 slides.

In addition, the interaction means 54 comprises at least one housing section 9 of the resilient element 8 made on the sliding body 7.

In this case, the resilient element 8 is preferably a spring housed at least partly inside the housing section 9 and wound at least partly around the sliding body 7. In fact, the sliding body 7 comprises at least one elongated portion 10 facing the thrust chamber 4 and at least one enlarged portion 11 opposite the elongated portion 10 and associated with the latter to define with the latter a stop section 12 of the resilient element 8 wound around the elongated portion 10.

In addition, appropriately, the stop section 12 is arranged, in use, substantially opposite the housing section 9.

This way, the resilient element 8 is interposed between the housing section 9 and the stop section 12, so as to be loaded when the sliding body 7 is moved close to the sliding chamber 6, and unloaded when the sliding body 7 is moved close to the sensing element 5. This way, the resilient element 8 counteracts the movement of the sliding body 7 caused by the magnetic means 15, 16, 47, 51, 58, which, during the movement of the stem 2, move the sliding body 7 along the sliding chamber 6 and consequently move the interaction means 54 from the home configuration to the active configuration.

Alternative embodiments of the device 1 cannot however be ruled out wherein the interaction means 54 are shaped in such a way that the resilient element 8 is loaded when the sliding body 7 is moved close to the sensing element 5 and unloaded when the sliding body 7 is moved close to the sliding chamber 6.

In particular, the sliding body 7 comprises at least a first ending portion 13 facing the sliding chamber 6 and at least a second ending portion 14 opposite the first ending portion 13.

In addition, the magnetic means 15, 16, 47, 51, 58 comprise at least a first magnetic element 15 associated with the first ending portion 13 and at least a second magnetic element 16 associated with the second ending portion 14.

In particular, the first magnetic element 15 is adapted to operate in conjunction with the stem 2 to move the interaction means 54 between the home configuration and the active configuration.

On the other hand, the second magnetic element 16 is adapted to operate in conjunction with the sensing element 5 to detect the presence/absence of the stem 2 in the proximity of the predefined position during the movement of the interaction means 54 between the home configuration and the active configuration.

Preferably, the first magnetic element 15 is a permanent magnet.

Likewise, the second magnetic element 16 is preferably a permanent magnet. Advantageously, the first magnetic element 15 faces outwards from the first ending portion 13 towards the thrust chamber 4, as shown in Figures 1 and 2.

In the same way, the second magnetic element 16 faces outwards from the second ending portion 14 towards the sensing element 5.

This way, the magnetic field exerted by the first and the second magnetic elements 15, 16 is not hindered by the sliding body 7. In particular, the first ending portion 13 preferably coincides with the elongated portion 10 and the second ending portion 14 preferably coincides with the enlarged portion 11.

This way, the enlarged portion 13 and consequently the second magnetic element 16 is arranged, in use, in the proximity of the sensing element 5, thus facilitating the interaction with the latter.

Similarly, the elongated portion 10 and consequently the first magnetic element 15 is arranged, in use, in the proximity of the stem 2, thus facilitating the interaction with the latter.

In fact, the stem 2 comprises at least one piston 17 sliding tightly inside the liner 3, and the reference element 57 is made of one of a ferrous, magnetic and non magnetic material and coincides with the piston 17.

Further embodiments of the device 1 cannot however be ruled out wherein the reference element 57 and the stem 2 are separate from each other and wherein the reference element is associated with the piston 17.

Preferably, the stem 2 comprises an elongated body 18 locked together in shifting motion with the piston 17 to form the stem itself.

In particular, the piston 17 corresponds to the end of the stem 2 arranged inside the thrust chamber 4 and the elongated body 18 is movable in a sliding manner inside and outside the thrust chamber 4, as shown in Figure 1 and Figure 2. Advantageously, when the piston 17 is arranged at the predefined position of the sensing device 55, 55a, 55b, the reference element 57 operates on the first magnetic element 15, which causes the sliding body 7 to move.

Preferably, the piston 17 is made of ferrous material and operates on the first magnetic element 15 by attracting it to itself.

As a result, the sliding body 7 is attracted to the piston 17 and moves the second magnetic element 16 away from the reference element 57, thus causing the interaction means 54 to move from the home configuration to the active configuration.

Alternatively, if the reference element 57 is made of magnetic material, the first magnetic element 15 is attracted or forced back by the reference element 57 depending on the polarity of the magnetic pole of the reference element 57 facing the first magnetic element 15.

On the other hand, if the reference element 57 is made of non-magnetic material, the remaining part of the stem 2 is made at least partly of ferrous or magnetic material. This way, the stem 2, during its movement, operates on the first magnetic element 15 by forcing it back/attracting it, except for the point at which the reference element 57 faces the first magnetic element 15.

In fact, given the nature of the non-magnetic material, when the reference element 57 faces the first magnetic element 15, it shields the action of the stem 2 on the first magnetic element 15, which is brought back by the resilient element 8 in one of either the home configuration or the active configuration. Preferably, the sensing element 5 is a magnetic sensor configured to detect the magnetic field exerted by the magnetic means 15, 16, 47, 51, 58 and to sense the variation thereof during the movement of the interaction means 54 between the home configuration and the active configuration.

In fact, in the home configuration, the second magnetic element 16 is moved close to the sensing element 5, i.e. the magnetic sensor, which detects the magnetic field emitted by the second magnetic element 16 so as to signal the presence/absence of the stem 2 at the predefined position.

On the contrary, in the active configuration, the second magnetic element 16 is moved away from the sensing element 5 to signal the presence/absence of the stem 2 at the predefined position.

Embodiment variants, not shown in the figures, cannot however be ruled out wherein the magnetic means 15, 16, 47, 51, 58 comprise a single magnetic element associated with the sliding body 7 and facing outwards from the latter at the first and second ending portion 13, 14.

This way, the end of the magnetic element facing the first ending portion 13 operates in conjunction with the stem 2 to move the interaction means to the activation configuration and the end of the magnetic element facing the second ending portion 14 operates in conjunction with the sensing element 5 to signal the absence/presence of the stem 2 in the proximity of the predefined position. In addition, the interaction means 54 comprise at least one ferromagnetic element 19 interposed between the sliding body 7 and the sensing element 5 and adapted to intensify the magnetic field exerted by the magnetic means 15, 16, 47, 51, 58 on the sensing element 5 in the home configuration.

In particular, the interaction means 54 comprise at least one housing hole 20 made on the sliding chamber 6 and interposed between the sliding body 7 and the sensing element 5, as shown in Figure 3.

This way, the ferromagnetic element 16 is inserted inside the housing hole 20.

In particular, the housing hole 20 is preferably of the through hole type, and the ferromagnetic element 19 is accommodated to size inside the housing hole 20 and consequently faces the second magnetic element 16 and the sensing element 5 at the same time.

Conveniently, the ferromagnetic element 19, given its nature, guides the magnetic field lines emitted by the second magnetic element 16 towards the sensing element 5, promoting the latter to sense the magnetic field emitted by the second magnetic element 16.

Alternative embodiments of the device 1 cannot however be ruled out, wherein the ferromagnetic element 19 is not used.

Advantageously, the device 1 comprises at least one inlet port 23 of the work fluid inside the thrust chamber 4 associated with the liner 3 and centered along a direction of connection D.

In particular, an embodiment variant of the device 1 is shown in Figure 4, wherein the sensing device 55, 55a, 55b is associated with the inlet port 23 and defines at least one connecting channel 56 provided with at least a first connecting head 68 facing the inlet port 23 and at least one second connecting head 69 opposite the first connecting head 68 and facing a supply source 39 of the work fluid.

This way, the connecting channel 56 connects the inlet port 23 to the supply source 39 in a fluid- operated manner along the direction of connection D.

Preferably, the inlet port 23 is centered along a direction of connection D arranged substantially transverse to the direction of movement A. In particular, the direction of connection D is orthogonal to the direction of movement A.

In addition, the connecting channel 56 extends, preferably, substantially straight along the direction of connection D to connect the inlet port 23 to the supply source 39 in a fluid- operated manner along the direction of connection D.

Advantageously, the device 1 comprises at least one pair of inlet ports 23 of the work fluid associated with the liner 3 in fluid- operated communication with the thrust chamber 4 and adapted to supply the latter with the pressurized work fluid.

In addition, the inlet port 23 preferably defines a supply duct 24 through which the work fluid flows.

In particular, the supply duct 24 extends longitudinally and substantially centered along the direction of connection D.

Conveniently, the sensing device 55, 55a, 55b is at least partly associated inside the supply duct 24.

In particular, the connecting channel 56 comprises at least a first opening for the passage of the work fluid made at the first connecting head 68 and at least a second opening for the passage of the work fluid made at the second connecting head 69.

This way, the connecting channel 56 conveys the work fluid provided by the supply source 39 to the inlet port 23 and, consequently, to the thrust chamber 4. Preferably, the sensing device 55, 55a, 55b defines a plurality of connecting channels 56 substantially parallel to each other.

In addition, in this embodiment variant, the sliding chamber 6 extends substantially parallel to the connecting channel 56.

In particular, in this embodiment variant, the sliding chamber 6 and the connecting channel 56 are insulated from each other, i.e. the sliding body 7 is sealed inside the sliding chamber 6 and works dry.

Alternative embodiments of the device 1 cannot however be ruled out wherein the sliding chamber 6 and the connecting channel 56 are in communication with each other and the sliding body 7 works wet in the work fluid. In addition, the device 1 comprises at least one of:

removable association means 61, 62 of the sensing device 55, 55a, 55b with the inlet port 23 comprising at least a first associating portion 61 formed on the inlet port 23 and at least a second associating portion 62 formed on the sensing device 55, 55a, 55b, the first and the second associating portion 61, 62 being coupleable to each other along the direction of connection D; and removable connection means 63, 64 of the sensing device 55, 55a, 55b to the supply source 39 comprising at least a first connecting portion 63 formed on the sensing device 55, 55a, 55b and at least a second connecting portion 64 formed on the supply source 39, the first and the second connecting portion 63, 64 being coupleable to each other along the direction of connection D.

Preferably, the device 1 comprises both the association means 61, 62 and the connection means 63, 64.

In addition, the sensing device 55, 55a, 55b comprises at least a first end 65 arranged, in use, facing the thrust chamber 4, and at least a second end 66 opposite the first end 65.

In fact, the second associating portion 62 is preferably made at the first end 65. Instead, the first associating portion 61 is made inside the supply duct 24.

In particular, the first associating portion 61 is preferably a threaded profile and the second associating portion 62 is a nut screw profile adapted to couple to the threaded profile in a removable manner.

This way, the first end 65, in use, is fastened at least partly removable inside the supply duct 24 by means of the association means 61, 62.

Advantageously, the sliding chamber 6 protrudes at least partly outside the first end 65 along the direction of connection D, as shown in Figs. 4, 5 and 7.

This way, the position of the sliding chamber 6 can be adjusted with respect to the thrust chamber 4.

The first connecting portion 63, on the other hand, is made at the second end 66. Preferably, the second end 66 defines a connecting seat 67 inside which the supply source 39 is insertable in a removable manner. In addition, the connecting seat 67 preferably extends substantially centered and along the direction of connection D.

On the other hand, the second connecting portion 64 is made on the supply source 39.

In particular, the first connecting portion 63 is preferably a threaded profile and the second connecting portion 64 is a nut screw profile adapted to couple in a removable manner with the threaded profile.

More in detail, the first connecting portion 63 is conveniently made inside the connecting seat 67.

This way, the supply source 39, in use, is fastened in a removable manner and at least partly inside the connecting seat 67 by means of the connection means 63, 64.

Advantageously, in this embodiment variant, the sensing device 55, 55a, 55b is coupled to the work assembly 53 interposed directly between the inlet port 23 and the supply source 39.

In fact, the device 55, 55a, 55b made this way considerably reduces the overall dimensions of the device 1 with respect to the known type of devices, without significantly changing the connection between the inlet port 23 and the supply source 39.

An embodiment variant of the device 1 is shown in Figure 8, wherein the magnetic means 15, 16, 47, 51, 58 comprise at least one attractive element 51 associated with the sliding chamber 6 and facing the second magnetic element 16, wherein the attractive element 51 attracts the second magnetic element 16 to move the interaction means 54 between the home configuration and the active configuration.

Advantageously, the sliding chamber 6 comprises at least one extreme wall 52 facing the second ending portion 14 and with which the attractive element 51 is associated.

Appropriately, the attractive element 51 is associated with the extreme wall 52 and is arranged inside the sliding chamber 6.

In particular, this embodiment variant differs from the previous one in that it does not require the use of the resilient element 8.

In fact, in this embodiment variant the functions performed by the resilient element 8 are carried out by the second magnetic element 16 operating in conjunction with the attractive element 51.

In particular, in the home configuration, the sliding body 7 is moved close to the sensing element 5.

In fact, in this configuration, the attractive element 51 attracts the second magnetic element 16 to itself, thus causing the sliding body 7 to move away from the stem 2.

On the other hand, in the work configuration, the sliding body 7 is moved away from the sensing element 5.

In fact, in this configuration, the first magnetic element 15 faces the reference element 57, which attracts the sliding body 7 to itself.

In particular, in this configuration, the attractive effect between the first magnetic element 15 and the reference element 57 is greater than the attractive effect between the second magnetic element 16 and the attractive element 51.

In fact, even in the work configuration, the second magnetic element 16 suffers the attractive effect by the attractive element 51 ; this effect, in fact, causes the movement of the interaction means 54 from the work configuration to the home configuration when the reference element 57 is moved away from the first magnetic element 15.

Further embodiment variants of the device 1 cannot however be ruled out wherein the sensing devices 55, 55a, 55b are associated with the liner 3 outside the inlet port 23, as shown in Figure 1.

In addition, further embodiment variants of the device 1 cannot be ruled out, wherein it comprises a pair of inlet ports 23 and a single sensing device 55, 55a, 55b coupled to one of the ports themselves, as shown in Figure 13.

In addition, further embodiment variants of the device 1 cannot be ruled out, wherein the supply source 39 is connected in a fluid- operated manner to the inlet port 23 along a different direction with respect to the direction of connection D, as shown in Figures 9 and 10, wherein the supply source 39 is connected in a fluid- operated manner to the connecting channel 56 along a direction of connection substantially orthogonal to the direction of connection D and substantially parallel to the direction of movement A.

A further embodiment variant of the device 1 is shown in Figure 11.

In particular, this embodiment variant differs from the previous ones in that the interaction means 54 comprise at least one passage channel 21 made on the sliding chamber 6 facing the thrust chamber 4 and adapted to allow the passage of the work fluid between the sliding chamber 6 and the thrust chamber 4.

This way, the sliding chamber 6 of the sensing device 55, 55a, 55b is flooded by the work fluid.

Advantageously, the work fluid increases the inertia of the sliding body 7, which is thus made less sensitive to external stresses, such as e.g. vibrations and shocks, which operate on the device 1, thus reducing the risk of undesired switches of the interaction means 54.

In fact, these stresses can cause a false signal of the presence/absence of the stem 2 by the sensing device 55, 55a, 55b.

In particular, a shock of the device 1 could force the movement of the sliding body 7, e.g., from the home configuration to the active configuration regardless of whether or not the reference element 57 faces the first magnetic element 15 or not.

In particular, in the embodiment of the device 1 shown in Figures 1 and 2, the device 1 comprises a pair of sensing devices 55a, 55b.

Furthermore, in this embodiment, the work assembly 53 comprises at least one pair of end-of-stroke extremes 22a, 22b opposite and spaced apart from each other to substantially define the stroke of the stem 2 with respect to the liner 3 along the direction of movement A.

In fact, the piston 17 is movable inside the liner 3 between the end-of-stroke extremes 22a, 22b.

Advantageously, each of the sensing devices 55a, 55b is arranged at a respective end-of-stroke extreme 22a, 22b to detect the position of the stem 2 with respect to the liner 3. In particular, each sensing element 5 detects when the stem 2, in this case the piston 17, reaches a corresponding end-of-stroke extreme 22a, 22b.

Appropriately, in the embodiment of the device 1 shown in the Figures 1 and 2, the inlet ports 23 of the work fluid are associated in the proximity of the end-of- stroke extremes 22a, 22b to allow the movement of the stem 2 along the direction of movement A.

The operation of the embodiment of the device 1 described above is as follows. Advantageously, when the stem 2 is fully retracted inside the liner 3, the piston 17 is arranged at the predefined position of the sensing device 55a.

Consequently, the interaction means 54 of the sensing device 55a are in the active configuration.

In fact, the sliding body 7 of the sensing device 55a is moved close to the stem 2 due to the attraction between the first magnetic element 15 and the piston 17, which in this embodiment coincides with the reference element 57.

Consequently, the resilient element 8 is loaded and the second magnetic element 16 is moved away from the ferromagnetic element 19 and from the sensing element 5, which does not sense, or senses below a preset threshold value, the magnetic field emitted by the second magnetic element 16.

This way, the sensing element 5 detects that the piston 17 is arranged at the end-of-stroke extreme 22a defining the configuration wherein the stem 2 is totally retracted inside the liner 3, as shown in Figure 1.

Conversely, in this configuration, i.e. wherein the piston 17 is arranged at the sensing device 55a, the interaction means 54 of the sensing device 55b are in the home configuration.

In fact, the second magnetic element 16 of the sensing device 55b is moved close to the sensing element 5, which senses, or senses beyond a preset threshold value, the magnetic field thereof.

In addition, when moving the piston 17 from the end-of-stroke extreme 22a to the end-of-stroke extreme 22b, both devices 55a, 55b are in the home configuration.

Consequently, when the piston 17 reaches the end-of-stroke extreme 22b, the interaction means 54 of the sensing device 55b switch from the home configuration to the active configuration.

This way, the sensing element 5 detects that the piston 17 is arranged at the end- of- stroke extreme 22b defining the configuration wherein the stem 2 is totally extracted from the liner 3, as shown in Figure 2.

A further embodiment of the device 1 is shown in Figure 12, wherein the stem 2 comprises:

at least one shifting body 25 with respect to the liner 3 along the direction of movement A made of one of a ferrous, magnetic and non-magnetic material and operating in conjunction with the magnetic means 15, 16, 47, 51, 58 to move the interaction means 54 to one of the home configuration and the active configuration;

a plurality of reference elements 57 associated with the shifting body 25 spaced apart from each other along the direction of movement A at a plurality of respective pre-established positions and arranged, in use, facing the sliding chamber 6, the reference elements 57 being made of another of the ferrous, magnetic and non-magnetic material and operating in conjunction with the magnetic means 15, 16, 47, 51, 58 to move the interaction means 54 to the other of the home configuration and the active configuration.

Preferably, even in this embodiment, the stem 2 comprises a piston 17 and the shifting body 25 coincides with the elongated body 18.

However, unlike the embodiment described above, the piston 17 does not comprise a reference element 57, neither coincide therewith.

Alternative embodiments of the device 1 cannot however be ruled out wherein the piston comprises in turn one or more reference elements 57 or wherein it coincides with the reference element itself.

Preferably, the shifting body 25 is made of ferrous material and the reference elements 57 are made of non-magnetic material.

Further embodiments of the device 1 cannot however be ruled out wherein the shifting body 25 and the reference elements 57 are made of different materials, e.g. wherein the stem 2 and the reference elements 57 are made of a ferrous, magnetic and non-magnetic material, respectively.

In particular, in the embodiment of the device 1 shown in Figure 12, the sliding body 7 is moved close to the stem 2 whenever it is placed facing the shifting body 25.

On the contrary, the sliding body 7 is moved away from the stem 2, due to the resilient element 8, whenever it faces a reference element 57 or whenever it does not face the stem 2.

In fact, during the movement of the stem 2, the interaction means 54 of the sensing device 55, 55a, 55b are in the active configuration when the latter faces the shifting body 25.

On the other hand, the interaction means 54 of the sensing device 55, 55a, 55b are in the home configuration when the latter faces a reference element 57.

Advantageously, each detection of a reference element 57 corresponds to a predefined reciprocal position of the stem 2 with respect to the liner 3.

This way, the sensing device 55, 55a, 55b allows constantly monitoring the position of the stem 2 with respect to the liner 3.

Preferably, in this embodiment, the work assembly 53 comprises at least one guiding body 26 of the stem 2 through which the latter is coupled tightly to the liner 3 along the direction of movement A.

In addition, the sensing device 55, 55a, 55b is inserted at least partly inside the guiding body 26.

Advantageously, the work assembly 53 comprises at least one guiding channel 27 of the shifting body 25 made on the guiding body 26.

In particular, the shifting body 25 is provided with a cross section that is substantially complementary to the guiding channel 27 and substantially smaller than that of piston 17, which, as a result, is constrained inside the thrust chamber 4 along the direction of movement A by the guiding body 26.

In fact, advantageously, the guiding body 26 defines the end-of-stroke extreme

22b.

In other words, the piston 17 is shiftable in sliding contact with the liner 3 between the end-of-stroke extremes 22a, 22b.

On the other hand, the shifting body 25 is shiftable in contact with the guiding body 26 inside and outside the thrust chamber 4.

In particular, the sensing device 55, 55a, 55b is arranged inside the guiding body 26 facing the guiding channel 27.

This way, during the movement of the stem 2, the sensing device 55, 55a, 55b is substantially placed side by side with the shifting body 25, thus increasing the effect of the latter and of the reference elements 57 on the magnetic means 15, 16, 47, 51, 58 of the same sensing device.

In other words, this solution minimizes the distance between the shifting body 25 and the sliding body 7, thus increasing the sensitivity of the sensing device 55, 55a, 55b.

Preferably, in this embodiment, the shifting body 25 is substantially cylindrical in shape and is provided with a plurality of grooves 28 made at the predefined positions.

In addition, the reference elements 57 are substantially ring-shaped and are associated to size inside the grooves 28 to define with the shifting body 25 a substantially cylindrical- shaped body.

Conveniently, in this embodiment, the work assembly 53 comprises sealing means 31, 32 interposed between the guiding body 26, the stem 2 and the liner 3 to delimit the sliding chamber 6.

In addition, the sensing device 55, 55a, 55b is arranged outside or inside the thrust chamber 4.

In other words, the sealing means 31, 32 define a wet stretch 29 and a dry stretch 30 of the guiding channel 27, where the wet stretch 29 coincides with a portion of the thrust chamber 4 and the dry stretch coincides with a stretch outside the thrust chamber 4.

Preferably, the sealing means 31, 32 comprise at least a first sealing element 31 interposed between the liner 3 and the guiding body 26 and at least a second sealing element 32 interposed between the guiding body 26 and the stem 2.

In particular, in this embodiment, the sensing device 55, 55a, 55b is arranged outside the thrust chamber 4.

More in detail, the sensing device 55, 55a, 55b is arranged at least partly inside the guiding body 26 and faces the dry stretch 30 of the guiding channel 27.

In addition, in this embodiment, the sensing device 55, 55a, 55b is arranged outside the inlet port 23 of the work fluid.

An embodiment variant of the device 1 is shown in Figure 13 wherein, the sensing device 55, 55a, 55b is arranged inside the thrust chamber 4.

More in detail, in this embodiment variant, the sensing device 55, 55a, 55b is arranged at least partly inside the guiding body 26 and faces the wet stretch 29 of the guiding channel 27.

In addition, in this embodiment variant, the sensing device 55 is arranged inside an inlet port 23 of the work fluid.

A further embodiment variant of the device 1 is shown in Figure 14.

In particular, this embodiment variant differs from the embodiment of the device 1 described above in that the device 1 comprises signaling means 60 for signaling the direction of movement of the stem 2 with respect to the liner 3, interposed between the sensing device 55, 55a, 55b and the stem 2 and provided with:

at least one recess 33 made facing the stem 2 and defining with the latter a sliding duct 34 provided with at least one pair of stop ends 37a, 37b substantially opposite each other and between which the sliding duct 34 extends substantially parallel to the direction of movement A;

at least one movable body 35 arranged inside the sliding duct 34 in contact with the stem 2 and moved by dragging by the latter inside the sliding duct 34, the sensing device 55, 55a, 55b facing the sliding duct 34 at one of the stop ends 37a, 37b to signal the presence/absence of the movable body 35. Advantageously, in this embodiment variant, the device 1 comprises a plurality of sensing devices 55, 55a, 55b, among which one of these is placed facing the dry stretch 30.

Further embodiments of the device 1 cannot however be ruled out wherein it comprises a single sensing device 55, 55a, 55b. In particular, the signaling means 60 are interposed between the sensing device 55, 55a, 55b is placed facing the dry stretch 30 and the stem 2, as shown in Figure 14.

Preferably, the recess 33 is formed on the guiding body 26 facing inside the guiding channel 27.

In addition, the device 1 comprises an insert 36 obtained, preferably, on the guiding body 26, communicating with the recess 33 and inside which is housed the sensing device 55, 55a, 55b facing the recess itself at one of the stop ends 37a, 37b.

This way, advantageously, the sensing device 55, 55a, 55b, the stem 2 and the recess 33 operate in conjunction with each other to define the sliding duct 34, as shown in Figure 14.

In fact, the movable body 35 is constrained at the top and bottom, respectively, by the sliding chamber 6 and by the stem 2, and is constrained longitudinally along the direction of movement A between the stop ends 37a, 37b by the sliding duct 34.

This way, the movable body 35 is movable alternately along the direction of movement A in a forward direction B and in a backward direction C, which is substantially opposite the forward direction B.

In particular, conventionally, the term“forward direction B” indicates the direction of movement of the stem 2 along the direction of movement A outwards from the liner 3.

Conversely, the term“backward direction C” indicates the movement of the stem 2 along the direction of movement A inwards of the liner 3.

In particular, the movable body 35 is moved in the forward direction B or in the backward direction C at the same time as the movement of the stem 2.

In fact, the movable body 35 accompanies the movement of the stem 2 in the same direction of movement as the latter due to the sliding friction between the contact surfaces of the two.

In fact, the movable body 35 has, preferably, a ring shape and defines a passage hole inside which the stem 2 is inserted to size. This way, when the stem 2 is moved to the forward direction B, the movable body 35 is moved close to the stop end 37b until it is forced to stop its stroke at the latter.

On the other hand, when the stem 2 is moved to the backward direction C, the movable body 35 is moved close to the stop end 37a until it is forced to stop its stroke at the latter.

Preferably, the sensing device 55, 55a, 55b is arranged facing the sliding duct 34 at the stop end 37b.

Alternative embodiment variants of the device 1 cannot however be ruled out wherein the sensing device 55, 55a, 55b is arranged facing the sliding duct 34 at the stop end 37a.

Preferably, the movable body 35 is made of one of a ferrous, magnetic and non magnetic material.

Preferably, the movable body 35 is made of a magnetic material.

This way, the stem 2 does not drag the movable body 35 due to the sliding friction between the contact surfaces of the two.

In fact, in the event of the movable body 35 being made of a magnetic material, the movement thereof in the same direction of movement as the stem 2 is caused by the magnetic attraction with the latter.

Alternative embodiments of the device 1 cannot however be ruled out wherein the movable body 35 is moved in the same direction as the stem 2 due to the combination of sliding friction and magnetic attraction between the latter.

Advantageously, when the movable body 35 faces the sensing device 55, 55a, 55b, the corresponding sliding body 7 is moved close to the stem 2 due to the attraction between the movable body 35 and the first magnetic element 15, thus moving the interaction means 54 from the home configuration to the active configuration.

On the contrary, when the movable body 35 is moved away from the first magnetic element 15, the sliding body 7 is moved away from the stem 2 due to the thrust of the resilient element 8, which moves the interaction means 54 from the active configuration to the home configuration. In other words, the interaction means 54 of the sensing device 55, 55a, 55b switch from the home configuration to the active configuration when the movable body 35 is dragged by the stem 2 to the stop end 37b, i.e. when the stem 2 is moved in the forward direction B.

On the contrary, the interaction means 54 of the sensing device 55, 55a, 55b switch from the active configuration to the home configuration, when the movable body 35 is moved away from the stop end 37b, as shown in Figure 14. This way, the home configuration and the active configuration of the interaction means 54 of the sensing device 55, 55a, 55b facing the sliding duct 34 are related to the movement of the stem in the forward direction B or in the backward direction C, thus allowing the determination of the direction of movement of the stem 2.

A further embodiment of the device 1 is shown in Figure 15.

In particular, this embodiment differs from the embodiments described above in that the sensing element 5 is of the type of a micro- switch and is provided with at least one switch element 42 operable mechanically for the activation of the same sensing element 5.

Furthermore, in this embodiment, the sliding body 7 comprises at least one extreme portion 49 facing the thrust chamber 4 and at least one activation extreme 38 opposite the extreme portion 49.

Conveniently, the extreme portion 49 coincides with the first ending portion 13 described in the previous embodiments.

In particular, the activation extreme 38 is moved close to the switch element 42 pressing it in one of the home configuration and the active configuration, and is moved away from the switch element 42 releasing it in the other of the home configuration and the active configuration.

Advantageously, in this embodiment the magnetic means 15, 16, 47, 51, 58 comprise at least one magnetic body 47 associated with the extreme portion 49 and adapted to operate in conjunction with the stem 2 to move the interaction means 54 between the active configuration and the home configuration.

Advantageously, the sensing element 5, i.e. the micro-switch, can directly convey the power signals.

Advantageously, the sensing device 55, 55a, 55b comprises a pair of sensing elements 5, in this case micro- switches with changeover contacts, arranged opposite each other with respect to the sliding channel 59.

Preferably, the activation extreme 38 comprises at least one sliding shank 40 inside the sliding channel 59 and at least one activation shank 41 associated with the sliding shank 40 to define an activation extreme 38 having a substantially“T” shape.

In particular, the activation shank 41 is arranged outside the sliding channel 59 facing the switch element 42, as shown in Figure 16 and 17.

This way, during the movement of the sliding body 7 inside the sliding channel 59, the activation shank 41 is moved close and away from the sensing element 5 to press or release the switch element 42.

More in detail, the conformation and use of the magnetic body 47 are similar to the conformation and use of the first magnetic element 15 described with reference to the previous embodiments.

Conveniently, in this embodiment, the resilient element 8 is interposed between the sliding channel 59 and the activation extreme 38.

In particular, the interaction means 54 comprise at least one stop edge 48 obtained inside the sliding channel 59 and in which the resilient element 8 is housed.

More in detail, the resilient element 8 is preferably a spring wound at least partly around the sliding body 7 at the sliding shank 40 and interposed in abutment between the stop edge 48 and the activation shank 41, as shown in Figures 16 and 17.

The operation of the embodiment of the device 1 described above is as follows. Advantageously, when the reference element 57 faces the magnetic body 47, the interaction means 54 of the corresponding sensing device 55, 55a, 55b are in active configuration.

In fact, the sliding body 7 of the sensing device 55, 55a, 55b is moved close to the stem 2 due to the attraction between the magnetic body 47 and the reference element 57.

As a result, the activation shank 41 abuts against the switch element 42 and activates the sensing element 5.

In addition, the resilient element 8 is loaded in this configuration.

This way, when the reference element 57 is moved away from the magnetic body 47, the resilient element 8 is unloaded and moves the sliding body 7 away from the stem 2.

As a result, the activation shank 41 is moved away from the switch element 42, releasing it.

Further embodiments of the device 1 cannot however be ruled out wherein the sensing element 5 comprises an elastic return body, not shown in the figures, adapted to restore the status of the switch element 42 after the compression thereof by the activation shank 41.

In other words, in the active configuration, the compression of the switch element 42 causes the compression of the return elastic body, which, this way, is loaded and counteracts this compression, tending to return the switch element 42 to its original position.

In fact, once the compression action exerted by the activation shank 41 is completed, the elastic return body unloads and operates on the switch element 42 which in turn operates on the activation shank 41 by forcing it back, i.e. by moving it away from the sensing element 5.

Consequently, in this additional embodiment, the use of the resilient element 8 is not provided. In fact, in this further embodiment, the functions performed by the resilient element 8 are carried out by the return elastic body of the sensing element 5.

A further embodiment of the device 1 is shown in Figure 18, wherein, unlike the embodiment variant described above, the magnetic means 15, 16, 47, 51, 58 comprise at least one attractive body 58 associated with the activation extreme 38 and facing the attractive element 51.

In addition, the attractive element 51 and the attractive body 58 are configured to attract/force back each other to move the interaction means 54 between the home configuration and the active configuration.

Preferably, at least one of either the attractive element 51 or the attractive body 58 is made of magnetic material.

On the other hand, the other of either the attractive element 51 or the attractive body 58 is made of one of either a magnetic material or a ferrous material.

Preferably, the attractive element 51 is made of a magnetic material and the attractive body 58 is made of a ferrous material.

Alternative embodiment variants cannot however be ruled out wherein the attractive element 51 and the attractive body 58 are both made of a magnetic material.

This way, similarly to what described about the embodiment variant of the device 1 shown in Figure 8, the activation extreme 38 is constantly attracted by the extreme wall 52, so as to maintain the interaction means 54 in the home configuration.

In fact, in the home configuration, the activation shank 41 is moved away from the sensing element 5, as shown in Figure 19.

On the other hand, in the active configuration, the activation shank 41 is moved close to the sensing element 5 to abut against the switch element 42, as shown in Figure 19.

In fact, in this embodiment, the device 1 is without the resilient element 8 and its operation is similar to that described with reference to the previous embodiment, in which, however, the functions performed by the resilient element 8 are carried out by the attractive element 51 operating in conjunction with the attractive body 58.

Further forms and embodiment variants of the device 1 cannot however be ruled out made by means of the combination of the forms and embodiment variants described above.

In particular, the sensing devices 55, 55a, 55b shown in Figures 7, 8, 16, 17, 19 and 20 may be used as an alternative to the sensing devices 55, 55a, 55b used in the embodiments of the device 1 shown in Figures 4, 9, 11-14.

More in detail, it is considered particularly relevant the embodiment obtained by the use of the sensing devices 55, 55a, 55b shown in Figures 16, 17, 19 and 20 in combination with the work assembly 53 shown in Figure 13.

In fact, in this embodiment, the sensing of the intermediate positions of the stem 2 with respect to the liner 3, i.e. the repeated movement of the interaction means between the home configuration and the active configuration, causes the mechanical activation/deactivation of the micro- switch, which, in turn, generates a train of electrical pulses particularly easy to control by a user with respect to the signal generated by the magnetic sensor.

In other words, in this embodiment, all the intermediate positions detected by the sensing devices 55, 55a, 55b are mechanically transduced.

This solution considerably simplifies the device 1 compared to the embodiments in which a sensing element 5 of the type of a magnetic sensor is used.

In fact, the maintenance, installation and control of the signals generated by the sensing elements 5 of the type of a magnetic sensor is particularly complex compared to the sensing elements 5 of the micro-switch type.

It has in practice been ascertained that the described invention achieves the intended objects.

In particular, the interaction means allow the fluid-operated device to detect one or more stem positions with respect to the liner with an extremely high precision compared to the fluid- operated devices of known type.

More in detail, the interaction means make it possible to detect the reference elements in a very simple, reliable and accurate way, regardless of whether they are associated at the piston or at intermediate stem positions.

In addition, the use of the sensing devices provided with micro- switches makes it possible to directly convey the power signals without the need for auxiliary electronic signal conversion/processing systems.

Claims

1) Fluid- operated device (1) comprising:

at least one work assembly (53) supplied by at least one work fluid and provided with:

at least one liner (3);

at least one stem (2) coupled in a sliding manner inside said liner (3) and defining with the latter a thrust chamber (4) for the movement of said stem (2) with respect to said liner (3) longitudinally along a direction of movement (A);

at least one sensing device (55, 55a, 55b) associated with said liner (3) at a predefined position and provided with at least one sensing element (5) configured to detect without contact the presence of said stem (2) in the proximity of said predefined position;

characterized by the fact that said sensing device (55, 55a, 55b) comprises interaction means (54) interposed between said sensing element (5) and said stem (2) and movable without contact by the passage of said stem (2) between at least one home configuration, wherein said sensing element (5) detects one of the presence and the absence of said stem (2) at said predefined position, and at least one active configuration, wherein said sensing element (5) detects the other of the presence and the absence of said stem (2) at said predefined position.

2) Device (1) according to claim 1, characterized by the fact that said interaction means (54) comprise at least one sliding chamber (6) and at least one sliding body (7) inside said sliding chamber (6), in said home configuration said sliding body (7) moving close to said sensing element (5), which detects at least one of the presence or the absence of said stem (2), and in said active configuration moving away from said sensing element (5), which detects the other of the presence and the absence of said stem (2).

3) Device (1) according to one or more of the preceding claims, characterized by the fact that it comprises at least one inlet port (23) of the work fluid inside said thrust chamber (4) associated with said liner (3) and centered along a direction of connection (D) and by the fact that said sensing device (55, 55a, 55b) is associated with said inlet port (23) and defines at least one connecting channel (56) provided with at least a first connecting head (68) facing said inlet port (23) and at least a second connecting head (69) opposite said first connecting head (68) and facing a supply source (39) of the work fluid, said connecting channel (56) connecting said inlet port (23) and the supply source (39) in a fluid- operated manner along said direction of connection (D).

4) Device (1) according to one or more of the preceding claims, characterized by the fact that it comprises at least one of:

removable association means (61, 62) of said sensing device (55, 55a, 55b) with said inlet port (23) comprising at least a first associating portion (61) formed on said inlet port (23) and at least a second associating portion (62) formed on said sensing device (55, 55a, 55b), said first and said second associating portion (61, 62) being coupleable to each other along said direction of connection (D); and

removable connection means (63, 64) of said sensing device (55, 55a, 55b) to the supply source (39) comprising at least a first connecting portion (63) formed on said sensing device (55, 55a, 55b) and at least a second connecting portion (64) formed on the supply source (39), said first and said second connecting portion (63, 64) being coupleable to each other along said direction of connection (D).

5) Device (1) according to one or more of the preceding claims, characterized by the fact that said interaction means (54) comprise at least one passage channel (21) made on said sliding chamber (6) facing said thrust chamber (4) and adapted to allow the passage of the work fluid between said thrust chamber (4) and said sliding chamber (6).

6) Device (1) according to one or more of the preceding claims, characterized by the fact that said interaction means (54) comprise magnetic means (15, 16, 47, 51, 58) associated integral in translation with said sliding body (7) and adapted to operate in conjunction with said stem (2) to move said interaction means (54) between said home configuration and said active configuration. 7) Device (1) according to one or more of the preceding claims, characterized by the fact that said stem (2) comprises at least one reference element (57) adapted to operate in conjunction with said magnetic means (15, 16, 47, 51, 58) to move said interaction means (54) between said home configuration and said active configuration.

8) Device (1) according to one or more of the preceding claims, characterized by the fact that said sensing element (5) is a magnetic sensor configured to detect the magnetic field exerted by said magnetic means (15, 16, 47, 51, 58) and to sense the variation thereof during the movement of said interaction means (54) between said home configuration and said active configuration.

9) Device (1) according to one or more of the preceding claims, characterized by the fact that said interaction means (54) comprise at least one ferromagnetic element (19) interposed between said sliding body (7) and said sensing element (5) and adapted to intensify the magnetic field exerted by said magnetic means (15, 16, 47, 51, 58) on said sensing element (5) in said home configuration.

10) Device (1) according to one or more of the preceding claims, characterized by the fact that:

said sliding body (7) comprises at least a first ending portion (13) facing said thrust chamber (4) and at least a second ending portion (14) opposite said first ending portion (13);

said magnetic means (15, 16, 47, 51, 58) comprise at least a first magnetic element (15) associated with said first ending portion (13) and at least a second magnetic element (16) associated with said second ending portion (14);

said first magnetic element (15) is adapted to operate in conjunction with said stem (2) to move said interaction means (54) between said home configuration and said active configuration.

said second magnetic element (16) is adapted to operate in conjunction with said sensing element (5) to detect the presence/absence of said stem (2) in the proximity of said predefined position during the movement of said interaction means (54) between said home configuration and said active configuration.

11) Device (1) according to one or more of the preceding claims, characterized by the fact that said interaction means (54) comprise at least one resilient element (8) interposed between said sliding chamber (6) and said sliding body (7) and characterized by the fact that:

said resilient element (8) is loaded when said interaction means (54) are in one of said home configuration and said active configuration, bringing the latter back into the other of said home configuration and said active configuration;

said resilient element (8) is unloaded when said interaction means (54) are in the other of said home configuration and said active configuration, maintaining said interaction means (54) in the same configuration.

12) Device (1) according to one or more of the preceding claims, characterized by the fact that said magnetic means (15, 16, 47, 51, 58) comprise at least one attractive element (51) associated with said sliding chamber (6) and facing said second magnetic element (16), said attractive element (51) attracting said second magnetic element (16) to move said interaction means (54) between said home configuration and said active configuration.

13) Device (1) according to one or more of the preceding claims, characterized by the fact that said stem (2) comprises at least one piston (17) sliding tightly inside said liner (3) and said reference element (57) is made of one of a ferrous, magnetic and non-magnetic material and coinciding with said piston (17).

14) Device (1) according to one or more of the preceding claims, characterized by the fact that it comprises a pair of said devices (55a, 55b) and by the fact that:

said work assembly (53) comprises at least one pair of end-of-stroke extremes (22a, 22b) opposite and spaced apart from each other to substantially define the stroke of said stem (2) with respect to said liner (3) along said direction of movement (A);

said piston (17) is movable inside said liner (3) between said end-of-stroke extremes (22a, 22b); each of said devices (55a, 55b) is arranged at a respective end-of-stroke extreme (22a, 22b) to detect the position of said stem (2) with respect to said liner (3).

15) Device (1) according to one or more of the preceding claims, characterized by the fact that said stem (2) comprises:

at least one shifting body (25) with respect to said liner (3) along said direction of movement (A) made of one of a ferrous, magnetic and non magnetic material and operating in conjunction with said magnetic means (15, 16, 47, 51, 58) to move said interaction means (54) to one of said home configuration and said active configuration;

a plurality of said reference elements (57) associated with said shifting body (25) spaced apart from each other along said direction of movement (A) at a plurality of respective pre-established positions and arranged, in use, facing said sliding chamber (6), said reference elements (57) being made of another of the ferrous, magnetic and non-magnetic material and operating in conjunction with said magnetic means (15, 16, 47, 51, 58) to move said interaction means (54) to the other of said home configuration and said active configuration.

16) Device (1) according to one or more of the preceding claims, characterized by the fact that said work assembly (53) comprises at least one guiding body (26) of said stem (2) through which the latter is coupled tightly to said liner (3) along said direction of movement (A), said sensing device (55, 55a, 55b) being inserted at least partly inside said guiding body (26).

17) Device (1) according to one or more of the preceding claims, characterized by the fact that said work assembly (53) comprises sealing means (31, 32) interposed between said guiding body (26), said stem (2) and said liner (3) to delimit said thrust chamber (4), said sensing device (55, 55a, 55b) being arranged outside or inside said thrust chamber (4).

18) Device (1) according to one or more of the preceding claims, characterized by the fact that:

said sensing element (5) is of the type of a micro- switch and is provided with at least one switch element (42) operable mechanically for the activation of the same sensing element (5);

said sliding body (7) comprises at least one extreme portion (49) facing said thrust chamber (4) and at least one activation extreme (38) opposite said extreme portion (49) and adapted to mechanically operate said sensing element (5), said activation extreme (38) moving close to said switch element (42) pressing it in one of said home configuration and said active configuration, and moving away from said switch element (42) releasing it in the other of said home configuration and said active configuration;

said magnetic means (15, 16, 47, 51, 58) comprise at least one magnetic body (47) associated with said extreme portion (49) and adapted to operate in conjunction with said stem (2) to move said interaction means (54) between said active configuration and said home configuration.

19) Device (1) according to one or more of the preceding claims, characterized by the fact that said magnetic means (15, 16, 47, 51, 58) comprise at least one attractive body (58) associated with said activation extreme (38) and facing said attractive element (51), said attractive element (51) and said attractive body (58) being configured to attract/force back each other to move said interaction means (54) between said home configuration and said active configuration.

20) Device (1) according to one or more of the preceding claims, characterized by the fact that it comprises signaling means (60) for signaling the direction of movement of said stem (2) with respect to said liner (3), interposed between said sensing device (55, 55a, 55b) and said stem (2) and provided with:

at least one recess (33) made facing said stem (2) and defining with the latter a sliding duct (34) provided with at least one pair of stop ends (37a, 37b) substantially opposite each other and between which said sliding duct (34) extends substantially parallel to said direction of movement (A);

at least one movable body (35) arranged inside said sliding duct (34) in contact with said stem (2) and moved by dragging by the latter inside said sliding duct (34), said sensing device (55, 55a, 55b) facing said sliding duct (34) at one of said stop ends (37a, 37b) to signal the presence/absence of said movable body (35).