The present invention relates to a calibration and/or pressurization device, in particular it relates to a calibration and/or pressurization device for a device for indicating the pressure of a fluid in a closed circuit.

Said device for indicating the pressure of a fluid in a closed circuit may preferably be configured as a pressure sensor, for example a pressure gauge, or as a pressure transducer. The pressure transducer is a device that converts pressure into an analogue electrical signal. The conversion of pressure into an electrical signal is preferably achieved by the physical deformation of strain gauges connected to a pressure transducer membrane. The pressure applied to the pressure transducer produces a bending of the membrane, which in turn leads to the deformation of the strain gauges. Deformation produces a change in electrical resistance proportional to pressure. Manual calibration and/or pressurization devices, such as the device described in international patent application W02003081198A1, are known within the technical field of reference.

The manual calibration and/or pressurization device, also called press, comprises a piston that slides in an opening formed in a body. The sliding of the piston causes the compression of a fluid present within a closed circuit. The fluid pressure can be increased up to values of about 10000 bar. An operator can rotate a nut screw by acting on an external control, for example on spokes. The rotation of the nut screw, which engages on a thread formed on the piston, causes the translation of the piston itself.

Generally, in the closed circuit there are a device for indicating the pressure, to be calibrated, and a reference device. The electrical signal provided by the device for indicating the pressure must represent an accurate value of the fluid pressure in the closed circuit. For this reason, it is necessary to verify whether the device for indicating the pressure, to be calibrated, provides a pressure value corresponding to the one provided by the reference device. The reference device is generally a device for indicating the pressure made by specialised companies, e.g. SIT (Reference Service in Italy) centres. The reference devices are made so as to constitute a sort of "calliper" for other devices for indicating the pressure.

Given the difficulty of manually operating the calibration and/or pressurization device, due to the intensity of the force to be used to obtain high pressures in the closed circuit and the high precision required to obtain constant pressure values, motorised calibration and/or pressurization devices, comprising an electric motor that rotates a nut screw connected to the thread of the piston, have become widespread in recent years. One of the main problems with such motorised devices is their large sizes, particularly in the longitudinal direction. In fact, the motorised devices generally comprise a mechanical part, that remains substantially unchanged with respect to the manual calibration and/or pressurization devices, and an electric motor placed next to it. This leads to an increase of the sizes of the calibration and/or pressurization device, particularly in the longitudinal direction.

Another problem with motorised calibration and/or pressurization devices is related to the increase in weight compared to manual ones.

A further problem is related to the complexity of kinematics which generally comprises an electric motor, a gearbox and a joint.

The technical problem underlying the present invention is therefore to provide a calibration and/or pressurization device structurally and functionally designed to obviate, at least in part, one or more of the drawbacks complained of with reference to the aforementioned prior art.

In the context of this problem, an object of the present invention is to provide a calibration and/or pressurization device which is particularly versatile and usable for a plurality of types of devices for indicating the pressure.

Another object is to provide a calibration and/or pressurization device that allows a particularly precise movement of the piston in order to achieve high and constant fluid pressure values in the closed circuit. A further object is to provide a particularly compact and lightweight calibration and/or pressurization device.

This problem is solved and this object is achieved by the invention by means of a calibration and/or pressurization device according to the appended claims. According to one aspect of the invention, the calibration and/or pressurization device for a device for indicating the pressure of a fluid in a closed circuit, preferably comprises a body, a piston, an anti-rotation device, a hollow electric motor and a hollow gear motor. The body includes a chamber which can be connected to the fluid of the closed circuit. The piston is suitable for moving in said chamber so as to compress the fluid of the closed circuit and has a longitudinal axis which defines a longitudinal direction. The longitudinal direction associated with the calibration and/or pressurization device is therefore substantially coincident with the axis of the piston. A transverse direction is advantageously perpendicular to said longitudinal direction.

The calibration and/or pressurization device preferably has the function both of compressing the fluid of the closed circuit by raising the pressure thereof and of calibrating a device for indicating the pressure present in said circuit. In this case, the pressurization device comprises a calibration device for the device for indicating the pressure of the fluid in the closed circuit. Preferably, the calibration device is suitable for carrying out calibration operations of the device for indicating the pressure present in the closed circuit, so as to verify the correspondence between the pressure value of the fluid in the circuit provided by the device for indicating the pressure and the one provided by a reference device present in the closed circuit.

In some embodiments, the calibration and/or pressurization device is advantageously used to compress the fluid of the closed circuit by raising the pressure thereof and not to calibrate a device for indicating the pressure present in said circuit. In this case, such a device can be referred to as a pressurization device for a fluid in a closed circuit.

The anti-rotation device is suitable for promoting a translational movement of the piston in the chamber. "To promote" a translational movement of the piston in the chamber means preventing or limiting the rotation of the piston, allowing longitudinal translation movements.

The hollow electric motor is suitable for moving the piston and comprises a first housing which extends along a longitudinal axis of said electric motor and defines a first axial cavity of said electric motor.

The hollow gear motor comprises: a second housing which extends along a longitudinal axis of said gear motor and defines a second axial cavity of said gear motor; an input element which is connected to the electric motor; and an output element which is connected to an internally threaded bush, said bush being suitable for engaging with an externally threaded element associated with the piston.

The longitudinal axis of the electric motor and the longitudinal axis of the gear motor are both located along the longitudinal direction. In other words, the longitudinal axis of the electric motor and the longitudinal axis of the gear motor are both substantially coincident with the longitudinal direction and therefore also with the longitudinal axis of the piston. The first cavity and the second cavity are advantageously configured to receive the internally threaded bush and the externally threaded element.

The calibration and/or pressurization device to which the invention relates allows to move in the first and second cavity at least part of the kinematic chain that regulates the movement of the piston. The hollow electric motor and the hollow gear motor, both formed so as to have a first cavity and a second cavity respectively, contribute to reduce the sizes of the calibration and/or pressurization device, in particular its longitudinal size. The geometry of said cavities allows in fact to receive elements of the kinematic chain that regulates the movement of the piston, in particular the externally threaded element and the internally threaded bush, which would otherwise be external to the electric motor and the gear motor. The use of the hollow electric motor and the hollow gear motor facilitates the integration of other elements, such as bearings, thus allowing the complexity and sizes of the calibration and/or pressurization device to be further reduced. The longitudinal dimension of the calibration and/or pressurization device is advantageously between 350 mm and 450 mm, more advantageously around 400 mm.

The first cavity advantageously has a longitudinal axis coincident with the longitudinal axis of the electric motor. The second cavity advantageously has a longitudinal axis coincident with the longitudinal axis of the gear motor. Advantageously, the first and second cavity are aligned longitudinally. Preferably, the first and second cavity are coaxial. Preferably, both the first and second cavity are coaxial to the piston. The first and second cavity preferably have a substantially cylindrical shape. Advantageously, the first and second cavity have substantially the same diameter. Advantageously, the first and second cavity are formed so as to receive the externally threaded element for at least two-thirds of its longitudinal size.

The electric motor is advantageously configured as a direct current motor. Preferably, the electric motor is configured as a permanent magnet motor, even more advantageously as a brushed motor. The electric motor preferably comprises a rotor and a stator. The rotor and the stator are advantageously coaxial. Preferably, the rotor and stator are both hollow. Preferably, the rotor is configured so as to wrap around the first cavity. Preferably, the stator is configured to wrap around the rotor. Advantageously, the interaction between the windings present on the rotor, in which electrical current can pass, and the magnets present on the stator enables the rotor to rotate.

Preferably, the gear motor has a transverse size substantially corresponding to a transverse size of the electric motor. Preferably, both the gear motor and the electric motor are contained in a casing, even more preferably said casing has a substantially cylindrical shape.

The gear motor is advantageously flanked by the electric motor in the longitudinal direction. Preferably, the gear motor and the electric motor are coaxial. The gear motor is advantageously supported by bearings. Preferably, the gear motor is of the harmonic type. The harmonic gear motor advantageously comprises an internal elastic component. The harmonic gearbox advantageously allows achieving a high reduction of the clearances and a high transmissible torque density. The input element and the output element of the gear motor are advantageously connected by toothed wheels. The input element of the gear motor receives motion from the electric motor, in particular from the rotor of the electric motor.

The output element of the gear motor is advantageously coupled to the internally threaded bush by means of a flange connected to said bush. Preferably, the bush and the flange are one single piece. Preferably, the flange is positioned at one end of the bush, said end being advantageously the end of the bush closest to the piston in the longitudinal direction. Advantageously, the flange is connected to the output element by means of a threaded connection. The bush preferably extends in the longitudinal direction. Preferably, the bush is substantially cylindrical in shape. Advantageously, the bush has a longitudinal axis that is substantially coincident with the longitudinal axis of the piston. Preferably, the bush is coaxial to the first and second cavities. The bush is preferably inserted in both the first and second cavity.

The externally threaded element preferably extends from the piston towards the electric motor in the longitudinal direction. Advantageously, the longitudinal axis of the externally threaded element substantially coincides with the axis of the piston, and therefore also with the longitudinal axis of the electric motor and with the longitudinal axis of the gear motor. Preferably, the externally threaded element is coaxial to both the first cavity and the second cavity. The externally threaded element preferably has a substantially cylindrical shape. The externally threaded element advantageously has a diameter greater than the diameter of the piston. The externally threaded element is advantageously insertable in both the first and second cavity. The externally threaded element is advantageously one single piece with the piston.

Advantageously, both the externally threaded element and the internally threaded bush have a thread with a pitch of about 2mm. This ensures that the advancement of the piston is sufficiently precise. Such an advancement may advantageously require a micrometre accuracy.

In a preferred embodiment of the invention, the rotary motion of the electric motor, and in particular of its rotor, is transferred to the hollow gear motor in which it will be reduced. Preferably, the gear motor rotates the internally threaded bush connected to it. Said bush in turn engages with the externally threaded element associated with the piston. The engagement between the externally threaded element and the bush would also rotate the piston. However, the anti rotation device promotes a translational movement of the piston in the chamber along the longitudinal direction, preventing it from rotating, as will be explained in more detail below.

Preferably, the piston has a cylindrical shape. Preferably, the chamber has a longitudinal axis substantially coincident with the longitudinal axis of the piston. Advantageously, the chamber is substantially cylindrical in shape. Preferably, the diameter of the piston substantially corresponds to the diameter of the body chamber. The chamber advantageously defines a swept volume of the calibration and/or pressurization device. The swept volume is preferably between 2 cubic cm and 10 cubic cm. This contributes to obtaining high fluid pressure values in the closed circuit.

Preferably, the chamber can be connected to the fluid in the closed circuit by means of a connection element. The connection element is preferably placed near an end of the body of the calibration and/or pressurization device, said end being advantageously on the side longitudinally opposite with respect to the electric motor. The chamber preferably comprises a restriction near the connection element.

The body of the calibration and/or pressurization device comprises a first portion and a second portion. Said portions can be advantageously connected to each other, e.g. by means of a threaded connection. In other embodiments, the portions are configured as a single body. The first portion can advantageously be connected to the closed circuit. The first portion preferably is substantially cylindrical in shape. Advantageously, a longitudinal axis of the first portion is substantially coincident with the longitudinal axis of the piston. The first portion comprises the chamber that can be connected to the fluid of the closed circuit. The first portion advantageously comprises the connection element that connects the chamber to the closed circuit.

The second portion is advantageously connected to the gear motor on the side longitudinally opposite with respect to the first portion. Preferably, the second portion has a substantially cylindrical shape, even more preferably cylindrical with a variable cross-section. Advantageously, a longitudinal axis of the second portion is substantially coincident with the longitudinal axis of the piston. Preferably, the second portion comprises a first interface and a second interface. Advantageously, the first interface is between the second and the first portion and the second interface is between the second portion and the gear motor. Preferably, the first interface is more transversely tapered than the second interface. The second portion preferably has an axial hole. Advantageously, the axial hole has a substantially cylindrical shape. Preferably, the axial hole has a longitudinal axis substantially coincident with the longitudinal axis of the piston. Preferably, the diameter of the axial hole is greater than the diameter of the piston; even more preferably, the diameter, of the axial hole substantially corresponds to the diameter of the externally threaded element.

The electric motor is advantageously powered by means of a power connector positioned on the casing containing the electric motor and the gear motor. The power connector advantageously allows the electric motor to be connected to the electricity grid. Preferably, said power connector is placed on one end of said casing, said end being on the side longitudinally opposite with respect to the second interface.

Preferably, in the closed circuit which can be connected to the calibration and/or pressurization device, the device for indicating the pressure, to be calibrated, and a reference device are present. Advantageously, the device for indicating the pressure, to be calibrated, and the reference device are subjected to the same fluid pressure in the closed circuit. Preferably, the reference device is also a device for indicating the pressure of the fluid in the closed circuit, but calibrated so as to provide a pressure value which is as close as possible to an actual pressure value of said fluid in the closed circuit. The reference device preferably has a higher accuracy class than that of a device for indicating the pressure to be calibrated. In other words, the reference device is a sort of "calliper" used to calibrate the device for indicating the pressure.

The calibration and/or pressurization device can advantageously be used for calibration operations of the device for indicating the pressure. These operations can preferably be carried out in climatic chambers, i.e. under controlled conditions of temperature, humidity, etc. When carrying out calibration operations, it is necessary to verify the correspondence between the pressure value of the fluid in the circuit provided by the device for indicating the pressure and the one provided by the reference device. When said values correspond, the device for indicating the pressure can be considered as correctly calibrated. Preferably, before said calibration operations the circuit is vacuumed so that the air in the circuit is eliminated. In fact, the air can cause inaccuracies in the calibration operations since it would not be possible to compress the liquid in the circuit at the desired pressure levels. Advantageously, in the event that the reference device and the device for indicating the pressure, to be calibrated, provide different pressure values, electronics on board said devices ensure that the electrical signal generated by the device for indicating the pressure is adapted to the reference device so that the device for indicating the pressure provides a fluid pressure value substantially corresponding to the one provided by the reference device.

The reference device can advantageously be sold as a kit together with the calibration and/or pressurization device. Alternatively, the reference device can be purchased separately.

The fluid used is preferably water, even more preferably water mixed with synthetic oils.

Preferably, the calibration and/or pressurization device has two connection elements, each of which connects the chamber to the fluid of the closed circuit: a first and a second connection element. Advantageously, the first connection element is suitable for connecting the calibration and/or pressurization device to the device for indicating the pressure and the second connection element is suitable for connecting the calibration and/or pressurization device to the reference device. Advantageously, the first connection member connects the calibration and/or pressurization device to a first branch of the closed circuit in which the device for indicating the pressure is present, and the second connection element connects the calibration and/or pressurization device to a second branch of the closed circuit in which the reference device is present. Advantageously, the calibration and/or pressurization device is suitable for bringing to the same pressure value both the fluid in the first branch and the fluid in the second branch, so that the device for indicating the pressure and the reference device are subjected to the same fluid pressure.

In some embodiments, the first connection element is connected to a manifold to which a plurality of devices for indicating the pressure to be calibrated can be connected. Each of the devices for indicating the pressure connected to the manifold is subjected to substantially the same pressure as the liquid in the closed circuit, said pressure being set by means of the calibration and/or pressurization device. The use of the manifold advantageously makes it possible to calibrate a plurality of devices for indicating the pressure at the same time.

Advantageously, there may be a third connection element suitable for being connected to a further device for indicating the pressure, for example present in a third branch of the closed circuit. The third element may otherwise be closed with a closing element, e.g. a plug suitable for preventing fluid pressure losses in the closed circuit.

In other embodiments, both the device for indicating the pressure and the reference device may be connected to a single connection element of the calibration and/or pressurization device. In this configuration, the device for indicating the pressure and the reference device are advantageously arranged in series in the closed circuit.

Preferably, the anti-rotation device is configured as a protuberance which extends transversely from the piston, said protuberance being formed so as to be inserted and to slide in a groove which is formed in the body of the calibration and/or pressurization device.

The anti-rotation device advantageously prevents the rotation of the piston. However, the piston could still make small rotations due, for example, to dimensional tolerances that are not particularly precise, which could lead to a clearance between the protuberance and the groove. For example, the protuberance could be slightly narrower than the groove and for this reason the piston could make small rotations around its longitudinal axis. Preferably, the groove extends transversely into the body. Advantageously, the groove is formed in the second portion of the body, most advantageously at the axial hole of said second portion. In alternative embodiments, the groove may be formed on the piston and the protuberance on the body.

The calibration and/or pressurization device preferably comprises an assembly device which is suitable for fixing the calibration and/or pressurization device to a support. The assembly device is preferably configured as a bracket which can be connected to the support, for example by means of a threaded connection. The assembly device is advantageously connected to the second portion of the body, even more advantageously to an area of the second portion interposed between the first and the second interface. Preferably, said area has a shoulder on which the assembly device abuts. Preferably, the calibration and/or pressurization device comprises a guide device interposed between the piston and the first portion of the body of the calibration and/or pressurization device.

The guide device is suitable for further promoting a straight translational movement of the piston along the longitudinal direction. The guide device preferably wraps around the piston. The guide device is advantageously configured as a drilled cylindrical bush. Preferably, the bush has a longitudinal axis substantially coincident with the longitudinal axis of the piston. Advantageously, the guide device has a substantially cylindrical shaped hole. The hole preferably has a diameter substantially corresponding to the diameter of the piston. The guide device is preferably near the first interface. The guide device is advantageously formed so as to wrap around the chamber of the first portion of the body.

Preferably, the calibration and/or pressurization device comprises a sealing device suitable for preventing fluid leaks from the chamber.

Advantageously, the sealing device is located at the first interface. Preferably, the sealing device is suitable for preventing fluid leaks from the first portion of the body to the second portion of the body. Advantageously, the sealing device is configured as a gasket. Preferably, the gasket has a through-hole. Preferably, the through-hole has a diameter substantially corresponding to the one of the piston. Advantageously, the guide device and the sealing device are placed side by side in the longitudinal direction. Preferably, the sealing device is in the longitudinal direction closer to the gear motor than the guide device.

Preferably, the calibration and/or pressurization device comprises a control system suitable for setting a certain fluid pressure value in the closed circuit and maintain said value constant through a retroactive algorithm.

Preferably, the control system comprises a data input system, for example a control console, through which it is possible to set a certain fluid pressure value in the closed circuit. Preferably, the data input system can be connected to a motor communication connector. Preferably, said motor communication connector is positioned on the casing containing the electric motor and the gear motor, even more preferably said motor communication connector is placed on one end of said casing, said end being on the side longitudinally opposite with respect to the second interface. Advantageously, the power connector and the motor communication connector are placed side by side.

Preferably, the control system comprises a microprocessor. Advantageously, the microprocessor is set to work with a retroactive algorithm. Preferably, said retroactive algorithm is of the Proportional-Integral-Derivative type, commonly abbreviated as PID. The piston preferably compresses the fluid in the closed circuit up to the pressure value set by means of the input device. Advantageously, the reference device present in the closed circuit provides the value of the actual fluid pressure in the closed circuit. Preferably, the control system receives the signal from the reference device and compares it with the pressure value set by means of the input device. If said pressure values are different, e.g. due to special environmental conditions, the control system advantageously acts on the calibration and/or pressurization device so that the latter modifies the pressure of the fluid in the circuit in order to bring the pressure indicated by the reference device back to the pressure value set by the input device. In other words, the control system receives the signal from the reference device, compares it with the set pressure value and then drives the electric motor to move the piston which, by translating, will modify the pressure of the fluid in the circuit until said pressures are the same.

The control system allows obtaining extremely precise and constant fluid pressure values in the closed circuit. Preferably, the retroactive algorithm of the microprocessor makes it possible to obtain a particularly precise and constant regulation of said pressure in the circuit. In some types of applications, for example, it may be necessary to control the fluid pressure stably down to a hundredth of a bar on a 10000 bar full scale.

The features and further advantages of the invention will be better appreciated from the following detailed description of a preferred, but not exclusive, embodiment illustrated, by way of non-limiting example, with reference to the appended drawings in which:

- figure 1 is a side view of the calibration and/or pressurization device;

- figure 2 is a perspective view of the calibration and/or pressurization device; - figure 3 is a longitudinal section of the calibration and/or pressurization device;

- figure 4 is a longitudinal section of the hollow electric motor and the hollow gear motor.

With reference to the figures, a calibration and/or pressurization device, for a device indicating the pressure of a fluid in a closed circuit, is referred to as a whole by the reference number 1.

The calibration and/or pressurization device 1 comprises a body 2, a piston 3, an anti-rotation device 4, a hollow electric motor 5 and a hollow gear motor 6.

The body 2 includes a chamber 9 which can be connected to the fluid of the closed circuit. The piston 3 is suitable for moving in said chamber 9 so as to compress the fluid of the closed circuit. The piston 3 has a longitudinal axis S defining a longitudinal direction X associated with the calibration and/or pressurization device 1. The longitudinal direction X thus substantially coincides with the longitudinal axis S of the piston 3. A transverse direction Y is substantially perpendicular to said longitudinal direction. The hollow electric motor 5 comprises a first housing 50 which extends along a longitudinal axis M of said electric motor 5 and defines a first axial cavity 51 of said motor 5.

The hollow gear motor 6 comprises: a second housing 60, which extends along a longitudinal axis R of said gear motor 6 and which defines a second axial cavity 61 of said gear motor 6; an input element, which is connected to the electric motor 5; an output element, which is connected to an internally threaded bush 7, said bush being suitable for engaging with an externally threaded element 8 associated with the piston 3.

The longitudinal axis M of the electric motor 5 and the longitudinal axis R of the gear motor 6 are both located along the longitudinal direction X. In other words, the longitudinal axis M of the electric motor 5 and the longitudinal axis R of the gear motor 6 are both substantially coincident with the longitudinal direction X and therefore also with the longitudinal axis S of the piston 3.

The first cavity 51 and the second cavity 61 are advantageously configured to receive the internally threaded bush 7 and the externally threaded element 8. The gear motor 6 is aligned with the electric motor 5 along the longitudinal direction X. The longitudinal axis M of the electric motor 5 and the longitudinal axis R of the gear motor 6 are substantially coincident.

The first cavity 51 has a longitudinal axis coincident with the longitudinal axis M of the electric motor 5. The second cavity 61 advantageously has a longitudinal axis coincident with the longitudinal axis R of the gear motor 6. The first 51 and the second cavity 61 are substantially coaxial to the piston 3. The first 51 and the second cavity 61 are aligned along the longitudinal direction X. The first 51 and the second cavity 61 are coaxial. The first and second cavity have a substantially cylindrical shape. The first 51 and the second cavity 61 have substantially the same diameter. The first cavity 51 and the second cavity 61 can receive the externally threaded element 8 throughout its longitudinal size. A longitudinal size L of the calibration and/or pressurization device 1 is advantageously about 400 mm.

The electric motor 5 preferably comprises a rotor 52 and a stator 53. A longitudinal axis of the rotor 52 and a longitudinal axis of the stator 53 are substantially coincident. The rotor 52 and the stator 53 are both hollow. The rotor 52 is configured so as to wrap around the first cavity 51 and the stator 53 is configured so as to wrap around the rotor 52.

The gear motor 6 has a transverse size substantially corresponding to a transverse size of the electric motor 5. Said transverse sizes are indicated in figure 3 with the letter T. Both the gear motor 6 and the electric motor 5 are contained in a casing 59 having a substantially cylindrical shape.

The input element of the gear motor 6 receives motion from the rotor 52 of the electric motor 5. The output element of the gear motor 6 is coupled to the internally threaded bush 7 by means of a flange 71 connected to said bush 7. The bush 7 and the flange 71 are preferably one single piece. The flange 71 is positioned at one end 72 of the bush 7, said end 72 being the one closest to the piston 3 in the longitudinal direction X. The bush 7 extends along the longitudinal direction X. The bush 7 is substantially cylindrical in shape and is inserted in both the first 51 and the second cavity 61. The bush 7 has a longitudinal axis substantially coincident with the longitudinal axis S of the piston 3. The longitudinal axis of the bush 7 coincides with the longitudinal axis M of the electric motor 5 and with the longitudinal axis R of the gear motor 6.

The externally threaded element 8 extends from the piston 3 towards the electric motor 5 along the longitudinal direction X. The longitudinal axis of the externally threaded element 8 coincides substantially with the longitudinal axis S of the piston 3, and thus also with the longitudinal axis M of the electric motor 5 and with the longitudinal axis R of the gear motor 6. The externally threaded element 8 has a substantially cylindrical shape and has a diameter greater than the diameter of the piston 3. The externally threaded element 8 is in both the first 51 and the second cavity 61. The externally threaded element 8 is one single piece with the piston 3. Advantageously, both the externally threaded element 8 and the internally threaded bush 7 have a thread with a pitch of about 2mm.

During use of the calibration and/or pressurization device 1, the rotary motion of the electric motor 5 and in particular of its rotor 52, is transferred to the hollow gear motor 6, where it is reduced. Preferably, the gear motor 6 rotates the internally threaded bush 7 connected to it. Said bush 7 in turn engages with the externally threaded element 8, associated with the piston 3. The engagement between the externally threaded element 8 and the bush 7 would also rotate the piston 3. However, the calibration device 1 comprises an anti-rotation device 4 which promotes a translational movement in the longitudinal direction X of the piston 3 in the chamber 9, preventing it from rotating.

The piston 3 has a substantially cylindrical shape. The chamber 9 has a longitudinal axis substantially coincident with the longitudinal axis S of the piston 3. The chamber 9 is substantially cylindrical in shape. Preferably, the diameter of the piston 3 substantially corresponds to the diameter of the chamber 9 of the body 2. The chamber 9 defines a swept volume of the calibration and/or pressurization device 1 preferably between 2 cubic cm and 10 cubic cm.

The body 2 of the calibration and/or pressurization device 1 comprises a first portion 21 and a second portion 22.

The first portion 21 is advantageously connected to the closed circuit. The first portion 21 preferably is substantially cylindrical in shape. The first portion 21 comprises the chamber 9 which can be connected to the fluid of the closed circuit. The first portion 21 comprises the connection element 91, 92 which connects the chamber 9 to the closed circuit.

The second portion 22 is connected to the gear motor 6 on the side longitudinally opposite with respect to the first portion 21. Preferably, the second portion 22 has a substantially cylindrical shape with a variable cross-section.

The second portion 22 comprises a first interface 26 and a second interface 28. The first interface 26 is between the second 22 and the first portion 21 and the second interface 28 is between the second portion 22 and the gear motor 6. The first interface 26 is more tapered in the transverse direction Y than the second interface 28. The second portion 22 preferably has an axial hole 27 of substantially cylindrical shape. The axial hole has a longitudinal axis substantially coincident with the longitudinal axis S of the piston 3. The diameter of the axial hole 27 is greater than the diameter of the piston 3 and substantially corresponds to the diameter of the externally threaded element 8.

The electric motor 5 is powered by means of a power connector 54 positioned on the casing 59 containing the electric motor 5 and the gear motor 6. The power connector 54 allows the electric motor 5 to be connected to the electricity grid in an advantageous manner. Preferably, said power connector 54 is placed on one end 69 of said casing 59, said end 69 being on the side longitudinally opposite with respect to the second interface 28.

Preferably, in the closed circuit which can be connected to the calibration and/or pressurization device 1, the device for indicating the pressure, to be calibrated, and a reference device are present. Advantageously, the device for indicating the pressure, to be calibrated, and the reference device are subjected to the same fluid pressure in the closed circuit.

When carrying out calibration operations, it is necessary to verify the correspondence between the pressure value of the fluid in the circuit provided by the device for indicating the pressure and the one provided by the reference device. When said values correspond, the device for indicating the pressure can be considered as correctly calibrated.

In the event that the reference device and the device for indicating the pressure to be calibrated provide different pressure values, electronics on board said devices ensure that the electrical signal generated by the device for indicating the pressure is adapted to the reference device so that the device for indicating the pressure provides a fluid pressure value substantially corresponding to the one provided by the reference device. The fluid used is preferably water, even more preferably water mixed with synthetic oils.

The chamber 9 can be connected to the fluid of the closed circuit by means of a connection element 91, 92. The connection element 91, 92 is placed near one end 23 of the body 2 of the calibration and/or pressurization device 1, said end being on the side longitudinally opposite with respect to the electric motor 5. The chamber 9 comprises a restriction 94 near the connection element 91, 92. Preferably, the calibration and/or pressurization device 1 has two connection elements 91, 92 each of which connects the chamber 9 to the fluid of the closed circuit: a first 91 and a second connection element 92. The first connection member 91 is suitable for connecting the calibration and/or pressurization device 1 to the device for indicating the pressure and the second connection member 92 is suitable for connecting the calibration and/or pressurization device 1 to the reference device. Advantageously, the first connection element 91 connects the calibration and/or pressurization device 1 to a first branch of the closed circuit in which the device for indicating the pressure is present, and the second connection element 92 connects the calibration and/or pressurization device 1 to a second branch of the closed circuit in which the reference device is present. The calibration and/or pressurization device 1 is suitable for bringing to the same pressure value both the fluid in the first branch and the fluid in the second branch, so that the device for indicating the pressure and the reference device are subjected to the same fluid pressure. Advantageously, there is a third connection element 93 closed with a closing element suitable for preventing fluid pressure losses in the closed circuit.

The anti-rotation device 4 is configured as a protuberance 41 which extends from the piston 3 along the transverse direction Y. The protuberance 41 is formed so as to be inserted and to slide in a groove 42 which is formed in the body 2 of the calibration and/or pressurization device 1. The groove 42 extends along the transverse direction Y within body 2. Advantageously, the groove 41 is formed in the second portion 22 of the body 2, more advantageously at the axial hole 24 of said second portion 22. The calibration and/or pressurization device 1 comprises an assembly device 35 suitable for fixing the calibration and/or pressurization device 1 to a support, not shown. The assembly device 35 is configured as a bracket 36 that can be connected to the support, for example by means of a threaded connection. The assembly device 35 is connected to the second portion 22 of the body 2, in particular to an area of the second portion 22 interposed between the first interface 26 and the second interface 28. Preferably, said area has a shoulder 37 on which the assembly device 35 abuts.

The calibration and/or pressurization device 1 comprises a guide device 77 interposed between the piston 3 and the first portion 21 of the body 20 of the calibration and/or pressurization device 1.

The guide device 77 is suitable for further promoting a straight translational movement of the piston 3 along the longitudinal direction X. The guide device 77 wraps around the piston 3. The guide device 77 is configured as a drilled cylindrical bush 78. The guide device 77 has a hole 79 which is substantially cylindrical in shape and having a diameter substantially corresponding to the one of the piston 3. The guide device 77 is preferably located near the first interface 26. The guide device 77 is formed so as to wrap around the chamber 9 of the first portion 21 of the body 2. The calibration and/or pressurization device comprises a sealing device 87 suitable for preventing fluid leaks from the chamber 9. Advantageously, the sealing device 87 is located at the first interface 26, so as to prevent fluid leaks from the first portion 21 of the body 2, in which the chamber 9 is present, to the second portion 22 of the body 2, coupled to the gear motor 6. The sealing device 87 is configured as a gasket 88 having a through-hole 89. The through-hole 89 has a diameter substantially corresponding to the one of the piston 3. Advantageously, the guide device 77 and the sealing device 87 are placed side by side in the longitudinal direction X. The sealing device 87 is in the longitudinal direction X closer to the gear motor 6 than the guide device 77. The calibration and/or pressurization device 1 comprises a control system 65 which is suitable for setting a certain fluid pressure value in the closed circuit and maintain said value constant through a retroactive algorithm.

The control system 65 comprises a data input system through which a certain fluid pressure value can be set in the closed circuit. The data input system can be connected to a motor communication connector 55 positioned on the casing 59 that contains the electric motor 5 and the gear motor 6. The motor communication connector 55 is located on one end 69 of said casing 59, said end 69 being on the side longitudinally opposite with respect to the second interface 28. The power connector 54 and the motor communication connector 55 are placed side by side. The control system 65 comprises a microprocessor 66 set to work with a retroactive algorithm. Said retroactive algorithm is of the Proportional-Integral- Derivative (PID) type. The piston 3 compresses the fluid in the closed circuit up to the pressure value set by the input device. The reference device present in the closed circuit provides the actual pressure value of the fluid in the closed circuit. The control system 65 receives the signal from the reference device and compares it with the pressure value set by means of the input device. If said pressure values are different, e.g. due to particular environmental conditions, the control system acts on the calibration and/or pressurization device so that the latter modifies the pressure of the fluid in the circuit in order to bring the pressure indicated by the reference device back to the pressure value set by means of the input device. In other words, the control system 65 receives the signal from the reference device, compares it with the set pressure value and then drives the electric motor 5 to move the piston 3 that by translating will modify the pressure of the fluid in the circuit until said pressures are the same. The invention thus solves the proposed problem while achieving multiple benefits. In particular, the hollow electric motor 5 and the hollow motor gear 6, both formed so as to have a first cavity 51 and a second cavity 61 respectively, contribute to reduce the size of the calibration and/or pressurization device 1, in particular its longitudinal size L, making it particularly compact and light. The control system 65 installed on the calibration and/or pressurization device 1 also contributes to obtain high and constant pressure values of the fluid in the closed circuit.