Test unit and method for measuring internal pressure of cylindrical glass container

Abstract

A test unit (12) for measuring the internal pressure of a cylindrical glass container comprises a support (14) adapted to accommodate the cylindrical glass container during a test phase so as to define a longitudinal axis corresponding in use to the longitudinal axis of the cylindrical glass container arranged in the support (14). The test unit (12) further comprises a pneumatic piston (16) adapted to selectively apply a predetermined axial force in a longitudinal direction substantially parallel to the longitudinal axis. The pneumatic piston is adapted to actuate a plunger movable along the longitudinal axis within the container arranged in the support (14). The test unit (12) is provided with at least one measuring sensor (18, 20) adapted to measure a diameter change in a transverse direction transverse to the longitudinal axis. A programmable control unit (22) operatively connected to the at least one measuring sensor (18, 20) is configured to correlate the diameter change measured by the at least one measuring sensor (18, 20) in the presence of a predetermined axial force with a reference internal pressure value corresponding to the measured diameter change and the predetermined axial force.

Description

Technical Field

[0001] The present invention relates to a test unit and method for measuring the internal pressure of a cylindrical glass container for pharmaceutical use. Specifically, the present invention relates to a test unit and method for measuring the pressure in a cylindrical glass container for pharmaceutical use (such as a syringe, an autoinjector or an ampoule). Background Art

[0002] It is well known that in pharmaceutical cylindrical glass containers, there is a particular need to evaluate the internal pressure and the effect of a given internal pressure on the wall of the container itself.

[0003] In the present disclosure, a cylindrical glass container is understood to be a substantially cylindrical container, in particular one that is closed at one end opposite to the plunger or pusher or has a smaller opening at the end.

[0004] For example, self-injectors are arranged with a thrust system, typically a spring-loaded piston, which, when activated, acts on the plunger of the syringe to initiate the injection.

[0005] The spring acts on the plunger to generate a pressure wave which propagates through the liquid contained in the syringe, causing the internal pressure of the syringe to increase, thus pressurizing the liquid volume.

[0006] The pressure of the liquid in the syringe suddenly increases, and the time interval can range from 0.1ms to as long as 15ms, but is usually between about 0.15ms and 3ms. It will also suddenly exert stress on the syringe wall, which may cause the wall to rupture in some cases.

[0007] Problems associated with increased syringe internal pressure are more pronounced, for example when containing concentrated and / or highly viscous drugs, as the spring force must be increased within an acceptable injection time, which may result in increased stress at the syringe wall.

[0008] It is thus known to carry out experimental tests on self-injecting syringes, in which a known amount of internal pressure is applied and the relative deformation of the wall is measured.

[0009] The measurement of the deformation of the syringe wall is usually accomplished by applying a contact system (usually strain gauges) to specific locations on the outer surface of the syringe.

[0010] Once a known stress is applied to the syringe plunger, the internal pressure is detected (via a dedicated internal sensor) and the relative deformation of the wall is measured using strain gauges.

[0011] Although the existing technology is widely used and understood, it is not without flaws.

[0012] For example, the use of strain gauges makes the testing process particularly complex and is not suitable for random sampling on a production line.

[0013] Furthermore, the process of placing strain gauges on the container wall is time-consuming and does not meet the sample quantity requirements required for production control.

[0014] Furthermore, prior art test systems can suffer from insufficient positioning accuracy of the strain gauges. Positioning errors can affect both the measurement itself and the comparability of values ​​measured on two different syringes, for example. Indeed, the installation of strain gauges requires professionals who are familiar with installation-related issues, such as the optimal amount of glue to use.

[0015] Furthermore, strain gauges attached to the outer wall of the syringe cannot be reused (unless testing is performed on the same syringe). In other words, the strain gauges cannot be removed and reused. This means that at least as many strain gauges as the number of syringes to be tested must be used, at the expense of cost and production time. Summary of the invention

[0016] In view of this, it is necessary to overcome the defects and limitations in the above-mentioned prior art.

[0017] The present invention needs to provide a system which can also be used during on-line sampling or which is characterized by a relatively short measurement time.

[0018] Furthermore, there is a need for a system that is not affected by problems caused by misalignment of the positioning of the measurement system on the outer surface of the container.

[0019] In order to at least partially meet the above requirements, the present invention provides a test unit for measuring the internal pressure of a cylindrical glass container and a method for measuring the internal pressure of a cylindrical glass container.

[0020] In particular, in order to at least partially meet the above requirements, the present invention provides a test unit for measuring the internal pressure of a cylindrical glass container, comprising:

[0021] a support adapted to house the cylindrical glass container during a testing phase so as to define a longitudinal axis (x) which corresponds, in use, to the longitudinal axis of the cylindrical glass container arranged in said support;

[0022] a piston adapted to selectively exert a predetermined axial force in a longitudinal direction substantially parallel to said longitudinal axis (x), the piston being adapted to actuate a plunger movable along said longitudinal axis in a container arranged in said support;

[0023] at least one measuring sensor adapted to measure a diameter variation in a transverse direction (y) transverse to said longitudinal axis (x);

[0024] A programmable control unit is operatively connected to the at least one measuring sensor and is configured to correlate the diameter change measured by the at least one measuring sensor in the presence of a predetermined axial force with a reference internal pressure value corresponding to the measured diameter change and the predetermined axial force.

[0025] According to an aspect of the invention, at least one measuring sensor is of optical type.

[0026] According to a possible embodiment, the at least one measuring sensor comprises two measuring sensors which are arranged substantially opposite each other in a radial direction.

[0027] According to a possible embodiment, the at least one measuring sensor is arranged on an adjustable support adapted to adjust the position of the at least one measuring sensor in a direction substantially parallel to the longitudinal direction and / or substantially parallel to the transverse direction (y).

[0028] According to a possible embodiment, said at least one measuring sensor is adapted to measure a diameter variation in a direction substantially perpendicular to said longitudinal axis (x).

[0029] According to a possible embodiment, the adjustable support is a micrometric slide allowing position adjustment along three Cartesian axes and adjustment by rotation around the three Cartesian axes.

[0030] According to a possible embodiment, the support is made of a rigid or semi-rigid material.

[0031] According to a possible embodiment, the support is made of a polymer material, a fiber-filled polymer material or aluminum.

[0032] According to a possible embodiment, the support member comprises a fixed base and a receiving portion, and the receiving portion comprises a substantially cylindrical inner surface.

[0033] According to a possible embodiment, the receiving portion comprises at least one measuring aperture adapted to place the interior of the receiving portion in visual communication with at least one measuring sensor.

[0034] According to a possible embodiment, the receiving portion comprises two diametrically opposed measuring apertures.

[0035] According to a feasible embodiment, the support member is provided with a longitudinal support mechanism for supporting the cylindrical glass container.

[0036] According to a possible embodiment, the longitudinal support mechanism for supporting the cylindrical glass container may be adapted to support a middle portion of the container or an end portion of the container.

[0037] According to a possible embodiment, the support is provided with a drainage hole adapted to ensure drainage of the fluid from the container after the piston impact.

[0038] According to a possible embodiment, the drain hole is arranged on the fixed base to allow fluid communication between the exterior and the inner surface of the receiving portion.

[0039] According to a possible embodiment, the piston is of pneumatic, electric or magnetic type.

[0040] According to a possible embodiment, the piston is arranged on a bridge-shaped support structure, which is arranged on a first test bench on which the support member is arranged.

[0041] According to a possible embodiment, the test unit comprises a first test stand constituting a support for the piston and a second test stand constituting a support for at least one sensor, the first and second test stands being separated from each other and / or vibration-isolated.

[0042] According to a possible embodiment, the control unit is configured to provide a piston thrust value associated with a corresponding actual thrust value.

[0043] According to a possible embodiment, when the cylindrical glass container is an auto-injector, the control unit is configured to provide a piston thrust value associated with a corresponding actual thrust value of a spring and a piston of the auto-injector.

[0044] According to a possible embodiment, the control unit is configured to perform measurements at least in the range between 2 ms before actuation of the plunger of the syringe and 30 ms after actuation of the plunger of the syringe, preferably between 5 ms and 15 ms.

[0045] According to a possible embodiment, the support comprises a force measuring device adapted to measure the force exerted by the piston on the syringe arranged in the support.

[0046] The method for measuring the internal pressure of a cylindrical glass container according to the present invention comprises:

[0047] (a) Initial step: Arrange a test unit for measuring the internal pressure of a cylindrical glass container according to the above content;

[0048] (b) a calibration step of calibrating the test unit, in which the pressure measuring device is inserted into a cylindrical glass container of a determined type to measure the container, and the piston applies a predetermined axial force, each axial force value being associated with a corresponding type of fluid contained in the container, a corresponding change in diameter of the container arranged in the support, and a corresponding pressure value measured in the container;

[0049] (c) a measuring step of measuring a change in diameter of the cylindrical glass container arranged in the support member by at least one measuring sensor;

[0050] (d) Processing step: The programmable control unit is operably connected to the at least one measuring sensor so as to associate the diameter change measured by the at least one measuring sensor with the reference internal pressure value corresponding to the measured diameter change and the predetermined axial force measured in the calibration step when a predetermined axial force is present.

[0051] According to a possible embodiment, the method comprises a step before step (c), wherein at least one measuring sensor is positioned:

[0052] The included angle α between the pointing trajectory of the measuring sensor and the tangent line of the circle at the observation point is 90°±10°, preferably 90°±5°, and more preferably 90°±1°.

[0053] According to a possible embodiment, the method comprises a step before step (c), wherein if the test unit is arranged with two measuring sensors, these sensors are positioned such that:

[0054] The maximum deviation between the measuring sensors in the longitudinal direction is 0.3 mm, preferably 0.05 mm to 0.1 mm;

[0055] The maximum deviation between the measuring sensors in the transverse direction is 0.3 mm, preferably 0.05 mm to 0.1 mm.

[0056] According to a possible embodiment, the method comprises a step before step (c) in which an observation point is selected within a range of at most 20 mm above the shoulder of the cylindrical glass container, preferably within a range of 5 mm above the shoulder of the cylindrical glass container.

[0057] According to a possible embodiment, the calibration step (b) comprises the following steps:

[0058] Start calibration;

[0059] Install strain gauges and / or install pressure sensors;

[0060] comparing the measured values ​​obtained by the measuring sensors;

[0061] Verify compliance with mathematical models;

[0062] End calibration.

[0063] According to a feasible embodiment, the measuring step (c) comprises the following steps:

[0064] placing the container in the support;

[0065] Check vertical alignment between container and piston;

[0066] checking the positioning of at least one measuring sensor;

[0067] Starting to collect data by at least one measuring sensor;

[0068] an actuating piston;

[0069] End collection;

[0070] Save the collected data;

[0071] obtaining a maximum diameter change by combining signals from at least one measuring sensor;

[0072] Calculate the internal pressure at the maximum diameter change using thick shell theory in a linear elastic field;

[0073] The maximum diameter change and the associated maximum theoretical reference pressure are obtained during the calibration step. BRIEF DESCRIPTION OF THE DRAWINGS

[0074] Further features and advantages of the present invention will become more apparent with reference to the following description of non-limiting preferred embodiments, in which:

[0075] Figure 1 depicts a schematic perspective view of a test unit according to an embodiment of the present invention;

[0076] Figure 2 depicts a partial schematic perspective view of a test unit according to an embodiment of the present invention;

[0077] Figure 3 depicts a schematic front view of a test unit according to an embodiment of the present invention;

[0078] Figure 4 depicts a schematic top view of a test unit according to an embodiment of the present invention;

[0079] Figure 5 depicts a schematic side view of a test unit according to an embodiment of the present invention;

[0080] Figure 6 depicts a schematic side view of components of a test unit according to an embodiment of the present invention;

[0081] Figure 7 depicts a schematic elevation view of components of a test unit according to an embodiment of the present invention;

[0082] Figure 8 and Fig. 9 Schematic top and front views are shown showing the relative arrangement between a container and components of a test unit according to an embodiment of the present invention.

[0083] The common elements or parts of elements in the following embodiments will be marked with the same reference numerals. DETAILED DESCRIPTION

[0084] exist Figure 1 1 , reference numeral 12 denotes a testing unit for measuring the internal pressure of a cylindrical glass container 100 .

[0085] The test unit 12 comprises a support 14 adapted to accommodate the cylindrical glass container 100 during a testing phase so as to define a longitudinal axis x which corresponds in use to the longitudinal axis of the cylindrical glass container 100 .

[0086] Furthermore, the test unit comprises a piston 16 adapted to selectively exert a predetermined axial force in a longitudinal direction substantially parallel to the longitudinal axis x. The piston 16 is adapted to actuate a plunger 102 movable along the longitudinal axis within a container 100 arranged in the support 14 .

[0087] The test unit 12 further comprises at least one measuring sensor 18 , 20 adapted to measure a diameter change in a transverse direction y transverse to the longitudinal axis x.

[0088] Furthermore, the test unit 12 comprises a programmable control unit 22 which is operably connected to at least one measuring sensor 18, 20 and is configured to associate, when a predetermined axial force is present, a diameter change measured by at least one measuring sensor 18, 20 with a reference internal pressure value corresponding to such measured diameter change and such predetermined axial force.

[0089] At least one sensor 18 , 20 may be of optical type.

[0090] According to a possible embodiment, at least one sensor 18, 20 may be a laser type sensor. For example, at least one sensor 18, 20 may be a LH30IX485QP laser type sensor sold by Banner Engineering.

[0091] According to a possible alternative embodiment, at least one sensor 18, 20 may be a confocal sensor. For example, at least one sensor 18, 20 may be a CHRocodile CLS confocal sensor sold by the company Precitec.

[0092] The at least one measuring sensor 18, 20 may include two measuring sensors 18, 20, which are arranged substantially opposite to each other along corresponding directions of the diameter direction of the cylindrical glass container being tested or the containing part thereof.

[0093] According to a possible embodiment, at least one measuring sensor 18, 20 can be arranged on an adjustable support 24, 26, which is adapted to adjust the position of at least one measuring sensor 18, 20 in a direction substantially parallel to the longitudinal axis (x) and / or in a direction substantially parallel to the transverse direction (y).

[0094] The adjustable supports 24, 26 may be, for example, micrometric slides allowing position adjustment along at least one Cartesian axis and adjustment by rotation around at least one Cartesian axis. Advantageously, the adjustable supports 24, 26 may be, for example, micrometric slides allowing position adjustment along three Cartesian axes and adjustment by rotation around three Cartesian axes.

[0095] According to a possible embodiment, the measuring sensors are adjusted in terms of position and signal strength by means of a dedicated computer program.

[0096] The adjustable supports 24 , 26 may be adapted to allow positioning of the at least one measurement sensor 18 , 20 so as to be able to take measurements on the cylindrical glass container 100 between the container shoulder 104 and 2 cm in the direction of the plunger 102 .

[0097] The support 14 may be made of a rigid or semi-rigid material. According to a possible embodiment, the support 14 may be made of a polymeric material, possibly a fiber-reinforced polymeric material. In an alternative embodiment, the support 14 may be made of a metal, such as aluminum.

[0098] Reference Figure 6 and Figure 7 In the embodiment, the support member 14 may include a fixed base 142 and a receiving portion 144.

[0099] The receiving portion 144 of the support 14 may be adapted to prevent glass-to-glass or glass-to-metal contact by using an insert (not shown) made of a polymeric material and disposed on an inner surface 148 of the receiving portion 144 for receiving the cylindrical glass container 100 .

[0100] According to a possible embodiment, the support member 14 may be connected to the first test table 28 , for example, by screws (not shown) and using through holes 146 provided at the fixing base 142 .

[0101] The receiving portion 144 may include a substantially cylindrical inner surface 148 and at least one measurement aperture 150 , 162 adapted to place the interior of the receiving portion 144 in visual communication with the at least one measurement sensor 18 , 20 .

[0102] The support 14 may be arranged with a longitudinal support mechanism 154 for supporting the cylindrical glass container 100 .

[0103] The longitudinal support mechanism 154 for supporting the cylindrical glass container may be adapted to support a middle portion or an end portion of the container.

[0104] For example, where the cylindrical glass container is a syringe, the longitudinal support mechanism 154 may be adapted to support a shoulder region of the syringe or a flange region thereof.

[0105] Advantageously, the inner surface 148 of the support 14 may be shaped to mate with respect to a cylindrical glass container to be placed therein.

[0106] The inner surface 148 may be designed such that the distance between the inner surface 148 and the cylindrical glass container is less than 0.2 mm during use.

[0107] According to a possible embodiment, the support 14 may be provided with a drain hole 156 adapted to ensure fluid discharge from the container after the piston 16 impacts. The drain hole 156 may be arranged at the fixed base 142 to allow fluid communication between the exterior of the receiving portion 144 and the inner surface 148.

[0108] According to a feasible embodiment, a reinforcing wing 143 may be provided between the fixed base 142 and the accommodating portion 144 , and the reinforcing wing 143 is adapted to make the accommodating portion 144 more stable relative to the fixed base 142 .

[0109] from Figures 1 to 5 It can be seen that, according to a possible embodiment, the support 14 , the piston 16 and the associated support structure 158 may be arranged on the first test stand 28 .

[0110] The first test stand 28 may have a substantially square base with three legs arranged on opposite sides.

[0111] According to a possible embodiment, the support 14 , the piston 16 and the associated support structure 158 may be arranged on a base structure 32 located above the support surface 34 of the first test stand 28 .

[0112] According to a possible embodiment, the measuring sensors 18, 20 are arranged on a second test station 36 independent of the first test station 28. Advantageously, the adjustable supports 24, 26 and the measuring sensors 18, 20 are arranged on a second test station 36 independent of the first test station 28.

[0113] According to a possible embodiment, the support surface 34 of the first test station 28 comprises at least one through hole 38 , 40 from which the second test station 36 together with the at least one adjustable support 24 , 26 protrudes.

[0114] Advantageously, the support surface 34 of the first test table 28 comprises two through holes 38, 40 from which the second test table 36 protrudes together with the adjustable supports 24, 26. The second test table 36 may be divided into two separate test tables to support each adjustable support 24, 26 independently.

[0115] In this way, the first test station 28 may be physically separated from the second test station 36 so that any vibrations are not transferred to the second test station 36 where the at least one measurement sensor 18 , 20 is located.

[0116] According to a possible embodiment, the first test stand 28 constituting the support of the piston 16 and the second test stand 36 constituting the support of the at least one sensor 18 , 20 may be separated from each other and / or vibration-isolated.

[0117] According to a possible embodiment, the support comprises a force measuring device 29 adapted to measure the force exerted by the piston on the syringe arranged in the support. For example, the force measuring device 29 can be arranged on the support 14 or on a fixed part of the piston 16. Advantageously, the force measuring device can be, for example, a load sensing unit.

[0118] The method according to the present invention will be described below.

[0119] The method for measuring the internal pressure of the cylindrical glass container 100 includes:

[0120] Initial step: Arrange a test unit 12 having the above-mentioned features for measuring the internal pressure of a cylindrical glass container 100;

[0121] Calibration steps of the test unit 12: measuring the cylindrical glass container 100 by inserting a pressure measuring device into a cylindrical glass container 100 of a determined type, and the piston 16 applies a predetermined axial force, each axial force value being associated with a corresponding type of fluid contained in the cylindrical glass container 100, a corresponding diameter change of the cylindrical glass container 100 arranged in the support 14, and a corresponding pressure value measured in the cylindrical glass container 100;

[0122] Measuring step: measuring a diameter change of the cylindrical glass container 100 arranged in the support 14 by at least one measuring sensor 18, 20;

[0123] Processing step: The programmable control unit 22 is operatively connected to at least one measuring sensor 18, 20 to correlate the diameter change measured by at least one measuring sensor 18, 20 in the presence of a predetermined axial force with a reference internal pressure value corresponding to such measured diameter change and such predetermined axial force.

[0124] In other words, in the case of a self-injecting syringe, the piston 16 of the test unit 12 simulates a spring piston system that activates the plunger 102 .

[0125] According to a feasible embodiment, the impact speed of the piston 16 can be adjusted to obtain substantially the same impact force as the spring piston system that activates the plunger 102. In this case, since the spring piston system of the syringe has a smaller mass relative to the piston 16, the impact speed of the piston 16 on the plunger 102 will also be slower.

[0126] A possible procedure for positioning the measurement sensors 18, 20 in preparation for the measurement step (c) will now be described.

[0127] Once the point of interest to be measured has been established and thus the circumference of the container 12 whose diameter is to be measured has been identified, the measuring sensors 18, 20 are directed to measure the distance, i.e. at the point closest to the sensor itself (see Figure 8 and Fig. 9 example shown).

[0128] like Figure 8 As shown, the angle α between the pointing trajectory of the measuring sensors 18 and 20 and the tangent of the circle of the observation point 30 may be 90°±10°, preferably 90°±5°, and even more preferably 90°±1°.

[0129] In the case where the test unit 12 is equipped with two measuring sensors 18, 20:

[0130] The maximum deviation between the measuring sensors in the longitudinal direction may be 0.3 mm, preferably 0.05 mm to 0.1 mm;

[0131] The maximum deviation between the measuring sensors in the transverse direction can be 0.3 mm, preferably 0.05 mm to 0.1 mm.

[0132] According to a possible embodiment, the observation point 30 may be selected to be about 5 mm above the shoulder.

[0133] The distance between the measuring sensors 18, 20 and the observation point 30 can be determined from the distance producing the strongest acquisition signal. Advantageously, the control unit 22 can be adapted to display the signal strength in order to adjust the position and distance of the measuring sensors 18, 20 relative to the container 100.

[0134] The calibration step can be performed using pressure sensors and strain gauges.

[0135] As mentioned above, the measuring sensor allows obtaining the change in diameter of the outer wall of the container caused by the impact of the piston with the plunger.

[0136] Strain gauges can be used to obtain deformation measurements of the outer wall of the container in both the axial and circumferential directions. Pressure sensors, on the other hand, allow for direct measurement of the internal pressure.

[0137] In a known manner, assuming a uniaxial tension state in the circumferential direction, the diameter change (measured with a non-contact measuring sensor), the deformation (measured with a strain gauge) and the internal pressure (measured with a pressure sensor) can be related by the thick shell linear theory. Considering that the model used is a linear elastic model, increasing the diameter change will linearly increase the internal pressure.

[0138] For different piston impact velocities, the peak diameter change obtained using the measuring sensor was validated by comparing it with the peak deformation values ​​obtained by strain gauge and pressure sensor measurements.

[0139] The user can then directly perform the calibration, for example via a predefined procedure.

[0140] Calibration may be performed by placing strain gauges at the observation points 30 of the measurement sensors 18 , 20 .

[0141] The step of validating the model used may take into account various types of containers 12 and parameters, such as different container filling amounts, viscosities of the liquid used, the presence or absence of an air gap, and different types of springs.

[0142] Advantageously, using two measuring sensors 18 , 20 , it is possible to evaluate changes in diameter due to system vibrations, translations, and container bending.

[0143] According to a feasible embodiment, the calibration step may include the following steps:

[0144] Start calibration;

[0145] Install strain gauges and / or install pressure sensors;

[0146] Comparing the measurement values ​​obtained by the measuring sensors 18, 20;

[0147] Verify compliance with mathematical models;

[0148] End calibration.

[0149] According to a feasible embodiment, the measuring step may include the following steps:

[0150] Placing the container 100 in the support 14;

[0151] Check whether the container 100 and the piston 16 are vertically aligned;

[0152] checking the positioning of at least one measuring sensor 18 , 20 ;

[0153] Start collecting data by at least one measuring sensor 18 , 20 ;

[0154] Actuating piston 16;

[0155] End collection;

[0156] Save the collected data (e.g. in a form in csv or similar format);

[0157] The maximum diameter change is obtained by combining the signals from at least one measuring sensor 18, 20;

[0158] Calculate the internal pressure at the maximum diameter change using thick shell theory in a linear elastic field;

[0159] During the calibration step, the maximum diameter change and the associated maximum theoretical reference pressure are output.

[0160] The advantages obtained with the test unit and the method according to the invention are therefore clear.

[0161] Firstly, the method indirectly determines the pressure inside the container by measuring the change in diameter.

[0162] In addition, the test unit and method provided by the present invention can also measure the internal pressure of a cylindrical glass container in a non-contact manner.

[0163] In this way, the test unit can for example be arranged directly in a production line, since no operator has to manually perform operations, such as applying strain gauges in prior art processes.

[0164] At the same time, the system is not affected by the positioning problem of the strain gauge on the outer surface of the container. Accordingly, the measurements made using the test unit and method of the present invention can be easily repeated and the measured values ​​can be compared between containers of the same type.

[0165] In order to meet special requirements, those skilled in the art may modify and / or replace the elements described in the above embodiments with equivalent elements without departing from the protection scope of the claims.

Claims

1. A test unit (12) for measuring the internal pressure of a cylindrical glass container (100), comprising: a support (14) adapted to receive the cylindrical glass container (100) during a testing phase so as to define a longitudinal axis (x) corresponding, in use, to the longitudinal axis of the cylindrical glass container (100) arranged in said support (14); a piston (16) adapted to selectively exert a predetermined axial force in a longitudinal direction substantially parallel to said longitudinal axis (x), said piston being adapted to actuate a plunger (102) movable along said longitudinal axis within said cylindrical glass container (100) arranged in said support (14); at least one measuring sensor (18, 20) adapted to measure a diameter variation in a transverse direction (y) transverse to said longitudinal axis (x); A programmable control unit (22) is operably connected to the at least one measuring sensor (18, 20) and is configured to associate the diameter change measured by the at least one measuring sensor (18, 20) with a reference internal pressure value corresponding to the measured diameter change and the predetermined axial force when a predetermined axial force is present.

2. The test unit (12) according to claim 1, characterized in that The at least one measuring sensor (18, 20) is of optical type.

3. The test unit (12) according to claim 1, characterized in that The at least one measuring sensor (18, 20) comprises two measuring sensors (18, 20) which are arranged substantially opposite each other in a radial direction.

4. The test unit (12) according to claim 1, characterized in that The at least one measuring sensor (18, 20) is arranged on an adjustable support (24, 26), which is adapted to adjust the position of the at least one measuring sensor (18, 20) in a direction substantially parallel to the longitudinal direction and / or substantially parallel to the transverse direction (y).

5. The test unit (12) according to claim 1, characterized in that The at least one measuring sensor (18, 20) is adapted to measure a diameter change in a direction substantially perpendicular to the longitudinal axis (x).

6. The test unit (12) according to claim 1, characterized in that The support (14) includes a fixed base (142) and a receiving portion (144), the receiving portion (144) including a substantially cylindrical inner surface (148) and at least one measurement aperture (150, 162), the measurement aperture (150, 162) being adapted to place the interior of the receiving portion (144) in visual communication with at least one measurement sensor (18, 20).

7. The test unit (12) according to claim 1, characterized in that The support member (14) is provided with a longitudinal support mechanism (154) for supporting the cylindrical glass container (100) and is adapted to support the middle portion of the container or the end portion of the container.

8. The test unit (12) according to claim 6, characterized in that The support member (14) is provided with a drain hole (156), which is adapted to ensure that the fluid is discharged from the container after the piston (16) impacts, and the drain hole (156) is arranged on the fixed base (142) to allow fluid communication between the outside of the accommodating part (144) and the inner surface (148).

9. The test unit (12) according to claim 1, characterized in that The test unit (12) comprises a first test stand (28) forming a support for a piston (16) and a second test stand (36) forming a support unit for at least one measuring sensor (18, 20), the first test stand (28) and the second test stand (36) being separated from each other and / or vibration-isolated.

10. The test unit (12) according to claim 1, characterized in that The programmable control unit (22) is configured to provide a thrust value of the piston (16) associated with a corresponding actual thrust value.

11. The test unit (12) according to claim 1, characterized in that The programmable control unit (22) is configured to perform measurements at least within a range between 2 ms before actuation of the plunger (102) of the cylindrical glass container (100) and 30 ms after actuation of the plunger (102) of the cylindrical glass container (100).

12. The test unit (12) according to claim 1, characterized in that The support (14) comprises a force measuring device (29) adapted to measure the force exerted by the piston (16) on a plunger (102) of the cylindrical glass container (100) arranged in the support (14).

13. A method for measuring the internal pressure of a cylindrical glass container (100), comprising: (a) Initial step: arranging a test unit (12) for measuring the internal pressure of a cylindrical glass container (100) according to claim 1; (b) a calibration step of calibrating the test unit (12), in which a pressure measuring device is inserted into a cylindrical glass container (100) of a determined type to measure the cylindrical glass container (100), and in which a predetermined axial force is applied by the piston (16), each axial force value is associated with a corresponding type of fluid contained in the cylindrical glass container (100), a corresponding diameter change of the cylindrical glass container (100) arranged in the support (14), and a corresponding pressure value measured in the cylindrical glass container (100); (c) a measuring step: measuring a change in diameter of the cylindrical glass container (100) arranged in the support (14) by at least one measuring sensor (18, 20); (d) Processing step: The programmable control unit (22) is operably connected to the at least one measuring sensor (26, 28) to associate the diameter change measured by the at least one measuring sensor (26, 28) when a predetermined axial force is present with a reference internal pressure value corresponding to the measured diameter change and the predetermined axial force measured in the calibration step.

14. The method for measuring the internal pressure of a cylindrical glass container (100) according to claim 13, characterized in that: The calibration step comprises the following steps: Start calibration; Install strain gauges and / or install pressure sensors; comparing the measurement values ​​obtained by the at least one measuring sensor (18, 20); Verify compliance with mathematical models; End calibration.

15. The method for measuring the internal pressure of a cylindrical glass container (100) according to claim 13, characterized in that: The measuring step (c) comprises the following steps: placing the cylindrical glass container (100) in a support (14); Checking whether the cylindrical glass container (100) and the piston (16) are vertically aligned; checking the positioning of the at least one measuring sensor (18, 20); Starting to collect data by means of the at least one measuring sensor (18, 20); Actuating piston (16); completing data acquisition by the at least one measuring sensor (18, 20); Collecting and saving data acquired by the at least one measuring sensor (18, 20); Obtaining a maximum diameter change based on the collected and stored data acquired by the at least one measuring sensor (18, 20); Calculate the internal pressure at the maximum diameter change using thick shell theory in a linear elastic field; The maximum diameter change and the associated maximum theoretical reference pressure are obtained during the calibration step.

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