Controlled dosing of cryogenic liquid

Abstract

Aseptic dosing head (2, 60) for cryogenic liquid, comprising an aseptic reservoir (10) for cryogenic liquid communicating with a dosing outlet (24); a metering valve stem (30) extending through the aseptic cryogenic liquid reservoir (10) and having a lower distal end configured to selectively open and close the metering outlet (24); an electromagnetic actuator (40) attached to an upper end of the metering valve stem (30) and operable to move the metering valve stem (30) to open and close the metering outlet (24); and a seal (42) extending around the metering valve stem (30) and separating the aseptic cryogenic liquid reservoir (10) from a cavity (44) between the seal (42) and the actuator (40).

Description

PRIORITY CLAIM

[0001] This application claims priority under 35 USC § 119(e) to U.S. patent application Serial No. 18 / 425,621, filed January 29, 2024, and U.S. patent application Serial No. 63 / 623,393, filed January 22, 2024, the entire contents of which are hereby incorporated by reference. TECHNICAL FIELD

[0002] This invention relates to systems and methods for delivering controlled doses of a cryogenic liquid, such as liquid nitrogen. BACKGROUND

[0003] In some processes, it is important to dispense a known amount of cryogenic liquid. For example, liquid nitrogen cans are dispensed into containers that are then immediately sealed in a beverage packaging line, so that after sealing, vaporizing nitrogen pressurizes the container. In this process, the amount of liquid dispensed must be carefully controlled. If too little cryogenic liquid is dispensed, the container may collapse if subjected to significant forces. If too much liquid nitrogen is dispensed, excessive pressure will build up within the container, causing it to deform or rupture. Even when cryogenic liquid (usually nitrogen) is provided in the container as an inert gas source rather than to pressurize it, the cryogen dispensing must be reliable and consistent, with no gaps or liquid surges.

[0004] Controlling the dispensed amount or dose of liquid nitrogen can be difficult, especially when doses must be delivered quickly, as is the case on a high-speed canning or bottle-filling assembly line. The large change in density resulting from liquid vaporization means that devices that dispense a given volume of liquid, such as valves, cannot deliver consistent amounts of cryogen unless the vapor / liquid state of the liquid is controlled.

[0005] Delivering controlled doses of a cryogenic liquid under aseptic conditions involves other considerations, such as how to ensure that the dosing equipment and the cryogen itself are as free from contamination or sterile as possible. Sterilizing the dosing equipment can be challenging. SUMMARY

[0006] According to one aspect of the invention, an aseptic cryogenic liquid dosing head comprises a cryogenic liquid reservoir in communication with a dosing outlet, a dosing valve stem extending through the cryogenic liquid reservoir and having a lower distal end configured to selectively open and close the dosing outlet, and an actuator attached to an upper end of the dosing valve stem and operable to move the dosing valve stem to open and close the dosing outlet.

[0007] In some embodiments, the actuator is electromagnetic.

[0008] In some embodiments, the dosing button also includes a seal extending around the dosing valve stem, separating the cryogenic liquid reservoir from a cavity between the seal and the electromagnetic actuator. The seal provides an airtight seal during operation.

[0009] In many examples, the head includes a controller that may be located some distance from the head, but is still operable to perform a head leak test, including pressurizing the cavity to a pressure greater than a pressure within the reservoir to test for leaks past the seal, and pressurizing the reservoir to test for leaks from the cryogenic liquid reservoir.

[0010] In some cases, the controller is also operable to sterilize the head by processing including introducing a pressurized sterilizing liquid into the reservoir while introducing a gas at a back pressure into the cavity, thereby maintaining the dispensing outlet in a closed state during sterilization.

[0011] In some cases, the controller sequences valves to sterilize the head and introduces a pressurized liquid into the reservoir while simultaneously pressurizing the non-aseptic cavity of the dispensing head, keeping the dispensing outlet in a closed state during sterilization.

[0012] The pressurized sterilization liquid can be steam, for example.

[0013] In some cases, the controller is designed to perform the head leak test both before and after head sterilization.

[0014] In some embodiments, the seal comprises a diaphragm attached to the metering valve stem. In some examples, the metering valve stem includes both a lower valve stem portion disposed below the diaphragm and an upper valve stem portion disposed above the diaphragm and connected to the lower valve stem portion by a threaded connection.

[0015] In some embodiments, the reservoir comprises a tube extending from above a cryogenic liquid level to below the cryogenic liquid level and surrounding the metering valve stem.

[0016] In some cases, the cryogenic fluid reservoir is contained within a housing that connects the metering outlet to the electromagnetic actuator. The housing and metering valve stem are preferably constructed primarily from materials with thermal expansion coefficients that differ by less than one percent. In some examples, both the housing and metering valve stem are constructed from stainless steel.

[0017] In some embodiments, the reservoir includes a cryogenic liquid supply line that is filled with cryogenic liquid during operation and extends from a primary cavity of the reservoir to the metering outlet.

[0018] In some examples, the electromagnetic actuator is a servomotor. For example, the servomotor may include an encoder that provides feedback to the controller regarding the position of the valve stem.

[0019] In some cases, the electromagnetic actuator is controllable to change the distance and duration of a displacement of the metering valve stem. This control can be achieved by changing the desired target displacement and time values ​​of the actuator control signal. The electromagnetic actuator can also be controllable to change a rest position of the metering valve stem relative to the metering outlet, for example, by changing a zero position of the valve stem displacement control.

[0020] Some embodiments also include a metered-dose outlet gas flow valve controllable to introduce a flow of sterile gas from a pressurized source to the metered-dose outlet to suppress frost accumulation. The metered-dose outlet gas flow valve may be controllable to open when the electromagnetic actuator is not operating, for example, to deliver a dose of cryogenic liquid. The metered-dose outlet gas flow valve may have a fixed bypass orifice that allows continuous flow of sterile gas to the metered-dose outlet when the electromagnetic actuator is operating to deliver a dose of cryogenic liquid, and may be arranged to introduce the flow of sterile gas to a portion of the metered-dose outlet open to atmospheric pressure.

[0021] In some cases, the lower distal end of the metering valve stem has a thermoplastic cap that engages a seat of the metering outlet.

[0022] Another aspect of the invention features a method for sterilizing a cryogenic liquid dosing head, the method comprising performing a system leak test by pressurizing a first cavity between a dosing valve stem seal and an electromagnetic dosing actuator and a second cavity on an opposite side of the dosing valve stem seal to test for system leaks, then testing for leaks past the seal by reducing the pressure in the second cavity, and with the pressure in the second cavity reduced, monitoring the pressure in the first cavity for a predetermined period of time.In response to a passed seal leak test, a sterilizing liquid is introduced into the second cavity and maintained in the second cavity under conditions that cause sterilization of the second cavity and a metering valve stem extending from the metering valve stem seal to a cryogenic liquid metering outlet, while maintaining sufficient pressure in the first cavity to cause the metering valve stem to remain seated at the cryogenic liquid metering outlet.

[0023] In some cases, the seal leak test and the second cavity leak test are both performed before and after introducing and maintaining the sterilizing fluid in the second cavity.

[0024] At least some embodiments of the invention can provide a particularly high aseptic dispensing rate. This can be achieved, at least in part, by enabling the use of a high-speed electromagnetic actuator under conditions that protect the actuator during sterilization.

[0025] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the following description. Other features, objects, and advantages of the invention will become apparent from the description and drawings, and from the claims. DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of a first embodiment of a cryogenic liquid delivery system for controlled dosing of cryogenic liquid. Fig. 2 is a schematic diagram of a second embodiment of a cryogenic liquid delivery system for controlled dosing of cryogenic liquid. Fig. 3 is a flowchart of a pressure test sequence. Fig. Figure 4 is a flow diagram of a sterilization process including pressure test sequences.

[0026] The same reference symbols in the different drawings indicate the same elements. DETAILED DESCRIPTION

[0027] Firstly, referring to Fig. 1 Cryogen is supplied from a pressurized source in the aseptic cryogenic liquid dosing head 2 and travels through a vacuum-jacketed conduit 3 through a controllable inlet valve 4 into a phase separation reservoir 10. The fill valve 4 can be controlled to ensure that the incoming cryogen substantially liquefies. A sterile filter is arranged in the conduit 3 upstream of the inlet valve 4, preventing unwanted particles from entering the reservoir. As the cryogen two-phase mixture flows into the reservoir 10, the gas phase is vented to atmosphere through the vent line 6. The liquid phase collects in the reservoir 10 and is maintained at a constant level by controlling the valve 4 in response to a level sensor 14.Liquid flows freely by gravity down the supply line 16, which is an extension of the reservoir 10, to a metering valve 20. The pressure head at the bottom of the metering valve is controlled by controlling the cryogenic liquid level in the reservoir. The entire reservoir, including the supply line 16, is enclosed in a vacuum insulation chamber 22 to minimize heating.

[0028] The metering valve 20 is controlled to dispense discrete doses 22 of a cryogenic liquid, such as liquid nitrogen, from the metering outlet 24, which is arranged so that each dispensed dose 22 falls into a container 26 passing below the outlet. The valve 20 can be controllably cycled at a high speed to dispense discrete doses 22 at a rate of, for example, up to 2,000 doses per minute, with each dose falling into a respective container. Each dose may, for example, be between 0.01 and 1.0 ml of cryogenic liquid. Each container moves to a capping station immediately after dosing.

[0029] The metering valve 20 includes a valve stem 30 that cycles vertically to seat and release against a valve seat 32 at the metering outlet, closing and opening the outlet. The stem is made of stainless steel with a thermoplastic tip to provide a sealing surface. When the outlet is open, cryogenic liquid is forced through the outlet by static pressure in the reservoir, determined by the liquid level. The valve seat is a surface of the outlet nozzle that may define a fixed dispensing orifice with a diameter of, for example, 0.065 inches (in some cases, 0.015 to 0.12 inches). The valve stem 30 is cycled by an electromagnetic linear actuator 40 that pushes and pulls the valve stem in response to a controlled electromagnetic force.A diaphragm 42 forms a seal that extends around the metering valve stem and separates the cryogenic liquid reservoir from a cavity 44 between the diaphragm and the electromagnetic actuator 40. The diaphragm provides an airtight annular seal, with an inner portion of the diaphragm attached to the valve stem and an outer portion of the seal secured to the surrounding structure, such as by engaging the inner end of a fitting that holds the actuator in place. In this example, the valve stem has an upper portion attached to the actuator and a lower portion extending to the valve seat. The two portions are threadedly connected at the diaphragm. The diaphragm flexes during each actuation cycle of the valve stem, allowing the stem to move a vertical distance of up to approximately 0.1 inch (2.5 mm) for one full stroke.The diaphragm 42 can be EPDM-molded, for example, over a textural core. In operation, the actuator 40 can be controlled to modulate the amount of valve stem lift and vary the opening and closing rate of the metering outlet, thereby altering the metered volume and dispensing parameters as needed for optimal metering. Control of the metered volume can be achieved, for example, as a function of a measured container pressure downstream of the capping station. Changing the metering parameters by controlling the linear actuator avoids the need to shut down the line to change nozzle sizes.

[0030] In this example, the linear actuator 40 is a linear servo motor (electric cylinder) with a built-in encoder with a resolution of 5 µm, an operating voltage of 48 VDC, a maximum stroke of 10 mm, and a peak output force of 100 N. Suitable actuators are commercially available. Such an actuator is precisely controlled by pulse-width modulation.

[0031] A metered outlet gas flow valve 34 may be controlled to introduce a flow of sterile dry gas from a pressurized source (not shown) to the metered outlet to assist in suppressing frost accumulation at the metered outlet. The metered outlet gas flow valve is preferably controlled to open when the electromagnetic actuator is not operating to deliver a dose of cryogenic liquid and to close during metering. The metered outlet gas flow valve 34 has a fixed bypass orifice that allows continuous flow of sterile gas to the metered outlet when the electromagnetic actuator is operating to deliver a dose of cryogenic liquid. In this way, a small flow of sterile gas always flows from the outlet to keep the outlet clean and frost-free, and a high flow of sterile gas flows during non-metering periods.As can be seen, the metering outlet gas flow valve is arranged to introduce the flow of sterile gas to a portion of the metering outlet open to atmospheric pressure. A heated containment plate 36 at the outlet works in combination with the purge gas from valve 34 to maintain warm, ice-free surfaces during dosing of the cryogenic liquid.

[0032] Aseptic dispensing requires that the dispensing system be sterilized at regular intervals. This sterilization typically involves introducing high-temperature steam (e.g., 250°F) to all internal surfaces normally exposed to cryogen (either liquid or gas) downstream of the fill valve at a pressure of approximately 30 psi, and maintaining these temperatures and pressures for a time sufficient to kill bacteria and pathogens on the surfaces. A sterilization cycle is described below. To protect the diaphragm 42 during sterilization, a non-aseptic gas is introduced into the cavity 44 by controlling the backpressure valve 46, thereby equalizing at least most of the steam pressure in the reservoir to prevent the valve stem from disengaging from the valve seat until desired.In pneumatic systems, the pneumatic metering valve actuator will generally be capable of developing sufficient downward force to maintain the valve seat during sterilization. Pressurizing the cavity 44 allows the use of electromagnetic actuators, which generally do not provide sufficient axial force to compensate for steam pressures.

[0033] Before performing a sterilization cycle, the integrity of the diaphragm 42 must be tested. Otherwise, high-temperature steam can damage the linear actuator. To test the integrity of the diaphragm, the cavity 44 can be pressurized to a test pressure above any pressure in the reservoir, and the cavity pressure can be monitored over a predetermined time interval to confirm that any leaks past the diaphragm are insignificant. This diaphragm test can be part of an overall head leak test in which both the cavity 44 and the reservoir are pressurized to check for leaks through any part of the aseptic section, and the pressure in the reservoir is then released while maintaining pressure in the cavity 44 to perform the diaphragm integrity test.

[0034] Aseptic dispensing also requires that the system's mechanical components withstand extreme temperature changes, ranging from -320°F liquid nitrogen temperatures during operation to +250°F steam temperatures during sterilization. Such extreme temperature changes can cause significant problems due to thermal expansion. Given that the dispensing valve stem in an aseptic system can be up to 30 inches long, careful attention must be paid to avoiding problems due to changes in the overall length of the valve stem due to thermal expansion. For example, the structure connecting the dispensing outlet to the linear actuator should be constructed of materials with an overall net thermal expansion coefficient that is the same or substantially the same as that of the valve stem.Preferably, the housing and the metering valve stem are primarily constructed of materials with thermal expansion coefficients that differ by less than one percent. In this example, such a structure is also made of stainless steel. Additionally, a bearing signal can be sent to the linear actuator after the valve stem has been immersed in cryogenic liquid for a period of time.

[0035] A controller 50 controls the various valves for performing pressure tests and completing a sterilization cycle. This may be the same controller that also controls the linear actuator during operation. At the start of a diaphragm pressure test, the controller opens the backpressure valve 46 until pressure in the cavity 44, measured by the cavity pressure sensor 52, exceeds the pressure in the reservoir 10 beneath the diaphragm, measured by the valve pressure sensor 54, by a fixed amount, such as 10 psi. The valve 46 is closed, and the cavity pressure is monitored for a fixed time interval, such as two minutes. If the cavity pressure drops by more than a predetermined amount, such as 3 psi, over the time interval, the controller sends a warning message that the diaphragm pressure test has failed, and the system is serviced.

[0036] Once the diaphragm test is complete, the controller 50 can also perform a full system leak test. With the vapor separator outlet valve 56 closed, the valve stem seated, and the reservoir vent line 6 closed (through a vent valve not shown), the controller pressurizes both the reservoir 10 and the cavity 44 by controlling valves 4 and 46 until pressures at sensors 52 and 54 are both within a predetermined pressure window. Valves 4 and 46 are then closed, and the pressure at sensor 54 is monitored over a set time interval. If the reservoir pressure drops by more than a predetermined amount, approximately 3 psi, over the time interval, the controller sends a warning message that the system leak test has failed, and the system is serviced. The diaphragm pressure test and the system leak test are typically both performed before and after system sterilization.

[0037] This sequence of these two tests is shown in the flow chart of Fig. 3. Upon initiation 100 of the pressure test sequence, the controller first closes open valves 102, then opens 104 the backpressure valve 46 and the inlet valve, and starts a 30-second timer 106 while pressurizing the main reservoir in parallel with the cavity 44. When the timer reaches 30 seconds, the backpressure valve 46 and the inlet valve 4 are closed 108, and a 2-minute timer 110 is started. At the end of the two minutes, the reservoir pressure is checked 112 at the pressure sensor 54. If the pressure has dropped by more than 3.0 psi during the two minutes, a signal is sent 114 indicating a pressure test failure. Otherwise, valves 56 and 64 are opened 116 to remove pressure from the reservoir, leaving the cavity 44 pressurized, and a third timer 118 is started.After the two minutes have elapsed, the pressure in cavity 44 is checked 120. If the cavity pressure has fallen below a predetermined setpoint, a signal is sent 122 indicating a failure of the membrane integrity test. Otherwise, the pressure test is successfully completed 124.

[0038] To sterilize the system, the controller 50 controls the inlet valve 4, through which pressurized steam (or other sterilizing medium) is introduced into the reservoir to sterilize the system, and the outlet valve 56, through which the steam is removed through a vapor separator 58 after sterilization. As stated above, the controller simultaneously pressurizes the cavity 44 with inert gas during sterilization by controlling valve 46 to help equalize stresses on the diaphragm and maintain the valve stem in its seat. The reservoir vent valve (not shown) is also kept closed during sterilization. The outlet valve 56 may remain at least partially open during the filling of the reservoir with steam to ensure a flow of sterilizing steam into the metering valve and up to the diaphragm.The controller can monitor the temperature at various points in the system to confirm that sterilization temperatures and times have been achieved before venting through the outlet valve. Sterilization of the dispensing outlet can be accomplished by raising the valve stem under steam conditions and allowing pressurized steam to vent through the outlet.

[0039] The sterilization sequence is shown schematically in Fig. 4. At initiation 200, such as at the end of a dispensing run, cryogen is vented 202 from the system by opening the dispensing outlet 24 with the fill valve 4 closed, and this configuration is maintained until the fill level sensor 14 indicates an empty reservoir for a predetermined period of time, such as 5 minutes. Next, the fill valve 4 is opened to a flow of dry gas, and the reservoir is heated 204 to a temperature above -100°F. Once an elevated reservoir temperature has been confirmed, the pressure test discussed above is initiated 100. Upon successful completion 124 of the pressure test, the valve 4 is opened 206 to a flow of heated sterilizing fluid, such as steam.The various valves leading from the reservoir are cycled to ensure that the entire reservoir is adequately exposed to heated steam, while the cavity 44 is sufficiently pressurized via valve 46 to prevent a high pressure drop across the membrane 42. During this sterilization step, the metering outlet 24 can be cleaned, either by introducing a sterilizing liquid through valve 34 or by sterilizing the outlet from below. The reservoir temperature is monitored until it exceeds a predetermined threshold, approximately 250°F, for a minimum period of time, approximately 30 minutes, to ensure sterilization of all internal surfaces.After sterilization, the sterilizing liquid is purged 210 from the system using a dry flow of sterile gas through the inlet valve 4, with the other valves in the system being cycled as needed to ensure that the entire system is purged. After purging, the pressure test sequence is initiated again 100 to confirm that the system is sealed and ready for further dosing. A dry gas flow is also provided through the dosing outlet valve 34. Once the pressure tests have been successfully completed 124, the reservoir is filled with cryogenic liquid to a desired level 126, and dosing can resume.

[0040] The controller 50 is connected to a user interface (not shown) that allows the operator to set parameters such as dispense duration and valve stem stroke, and to turn dispensing on and off. The controller 50 also receives inputs from various sensors, such as the fill level sensor 14, the pressure sensors 52 and 54, and various temperature sensors. To control the electromagnetic actuator 40, the controller 50 also receives a signal indicating the presence of a container to be dispensed, such as a single pulse from a container sensor (not shown), and a signal from an encoder embedded in the electromagnetic actuator that responds to valve stem displacement. For example, there may be 300 to 1500 encoder pulses per container dispensing cycle.The controller 50 also has outputs for controlling the various valves, such as the inlet valve 4, the purge gas valve 34, the back pressure valve 46, the outlet valve 56 and the vent valve 64.

[0041] Referring to Fig. 2, the aseptic dosing head 60 for cryogenic liquid has a similar function to that shown in Fig. 1, but the cryogen reservoir is concentric around the valve stem 30, which extends from the membrane 42 into the reservoir, which is surrounded by a tube 62 that extends below the free surface of the cryogenic liquid 70 in the reservoir. In this example, the reservoir vent valve 64 is shown. As in the example of Fig.1, all valves are controlled by the controller 50 to perform the diaphragm and leak tests discussed above, as well as sterilization of the aseptic space and surfaces. This example also shows a shutter 66 that is controlled to pivot to cover the dosing outlet during sterilization and when the system is not in use. The shutter defines a small hole through which condensate can drip from the dosing outlet cavity during sterilization. Some system components, such as a level switch or a sensor coupled to the fill valve 4, as well as various pressure and temperature sensors (except for a temperature sensor 68 in the steam vent line), are not shown for clarity.

[0042] While several examples have been described for illustrative purposes, the above description is not intended to limit the scope of the invention, which is defined by the scope of the appended claims. There are and will be other examples and modifications within the scope of the following claims. For example, although a solid-rim diaphragm is described as a seal along the metering valve stem, a sliding seal (such as an O-ring or lip seal that slides along the stem surface) may be used, but additional precautions should be taken to ensure that the entire valve stem surface exposed to the aseptic cavity in use is properly sterilized. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 18 / 425,621

[0001] US 63 / 623,393

[0001]

Claims

[1] Aseptic dosing head (2, 60) for cryogenic liquid, comprising an aseptic reservoir (10) for cryogenic liquid communicating with a dosing outlet (24); a metering valve stem (30) extending through the aseptic cryogenic liquid reservoir (10) and having a lower distal end configured to selectively open and close the metering outlet (24); an electromagnetic actuator (40) attached to an upper end of the metering valve stem (30) and operable to move the metering valve stem (30) to open and close the metering outlet (24); and a seal (42) extending around the metering valve stem (30) and separating the aseptic cryogenic liquid reservoir (10) from a cavity (44) between the seal (42) and the actuator (40). [2] The aseptic cryogenic liquid dosing head (2, 60) of claim 1, wherein the seal (42) is configured to provide an airtight seal during operation. [3] Aseptic dosing head (2, 60) for cryogenic liquid according to claim 1 or 2, wherein the seal (42) comprises a membrane attached to the dosing valve stem (30). [4] The aseptic cryogenic liquid dosing head (2, 60) of claim 3, wherein an inner portion of the membrane (42) is secured to the valve stem (30) and an outer portion of the membrane (42) is secured to the surrounding structure of the head. [5] Aseptic dosing head (2, 60) for cryogenic liquid according to claim 3 or 4, wherein the membrane (42) is adapted to flex during each actuation cycle of the valve stem (30) so that the valve stem can move. [6] An aseptic cryogenic liquid dosing head (2, 60) according to any preceding claim, wherein the electromagnetic actuator (40) is operable to move the dosing valve stem (30) to open and close the dosing outlet (24) to dispense discrete doses (22) of cryogenic liquid from the dosing outlet (24), preferably at a rate of up to 2000 doses per minute. [7] An aseptic cryogenic liquid dosing head (2, 60) according to any one of the preceding claims, wherein the head further comprises a controller (50) operable to perform a head leak test. [8] The aseptic cryogenic liquid dosing head (2, 60) of claim 7, wherein the head leak test comprises pressurizing the cavity (44) to a pressure higher than a pressure within the reservoir (10) to check for leaks at the seal (42). [9] The aseptic cryogenic liquid dispensing head (2, 60) of claim 7 or 8, wherein the head leak test comprises pressurizing the reservoir (10) to check for leaks from the cryogenic liquid reservoir (10). [10] An aseptic cryogenic liquid dosing head (2, 60) according to any one of the preceding claims, wherein the head further comprises the controller (50) operable to perform a sterilization cycle. [11] The aseptic cryogenic liquid dosing head (2, 60) of claim 10, wherein the sterilization cycle comprises introducing a pressurized sterilizing fluid into the reservoir (10) while introducing a gas at a counter pressure into the cavity (44), thereby maintaining the dosing outlet (24) in a closed state during sterilization. [12] An aseptic cryogenic liquid dosing head (2, 60) according to claim 10 or 11, wherein the sterilization cycle comprises raising the valve stem (30) to allow discharge of pressurized sterilizing fluid through the dosing outlet (24). [13] Aseptic dosing head (2, 60) for cryogenic liquid according to one of the preceding claims, wherein the electromagnetic actuator (40) is a servo motor. [14] The aseptic cryogenic liquid dosing head (2, 60) of claim 13, wherein the servo motor (40) comprises an encoder providing feedback regarding a position of the valve stem (30) to modulate the amount of lift of the valve stem (30) to control a dosing volume in response to a measured container pressure.

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