Gas exhaust medical injection device

Abstract

1. An injection device for injecting a medical fluid from a medical fluid container into a medical tube, the injection device comprising: a body; a piston (6) disposed in the body for moving the piston (6) along a longitudinal direction; a drainage path transverse to the piston (6); and a float (24) configured to float in the medical fluid and configured to move longitudinally within a cavity (36) between a blocking configuration in which an obstruction portion (24a) of the float (24) obstructs a passage (38) of the drainage path, thereby closing the drainage path, and an open configuration in which the obstruction portion (24a) of the float (24) moves away from the passage (38), thereby opening the drainage path, the float (24) having a metacenter (M) spaced from a top of the obstruction portion (24a) by a distance less than ⅓ of the height of the float (24).

Description

[Technical field]

[0001] FIELD OF THEINVENTION The present invention relates generally to the injection of medical fluids, and more particularly to an injection device for injecting medical fluids from a medical fluid container into medical tubing. [Background technology]

[0002] Injection devices are typically used to inject medical fluids from a medical fluid container into medical tubing. Injection of medical fluids, such as iodine contrast media, is required in 70% of CT scan diagnostic cases. This injection is performed using an automatic contrast injector in approximately 70% of cases. Injection tubing is required to connect the automatic injector to the patient.

[0003] Patent application US Serial No. 13 / 453,335 (US Patent Publication No. 20120209111) discloses a bladder syringe for a fluid delivery system including a cylindrical body, a cap-bladder assembly, a plunger element disposed on the cylindrical body, and a mounting assembly for fixing the cap-bladder assembly to the cylindrical body. The cylindrical body has a distal end and a proximal end and defines a through hole. The cap-bladder assembly is adapted to connect to the distal end of the cylindrical body and includes a cap body and a bladder. The cap body defines an internal cavity and a distal discharge conduit and is adapted to engage the distal end of the cylindrical body. The disk-shaped bladder is disposed within the internal cavity and typically includes a central membrane portion. The plunger element is disposed in the through hole of the cylindrical body and is vented to allow evacuation of a space between the plunger element and the cap-bladder assembly of the cylindrical body.

[0004] Patent application US 10 / 986,416 (US Published Patent Application No. 20060249541) discloses a fluid dispensing device including a bottle for receiving a fluid, a discharge tube, and a pressurizing device coupled between the bottle and the discharge tube for pressurizing the fluid and causing the fluid to flow through the discharge tube without gravity. The pressurizing device includes a container coupled between the bottle and the discharge tube, a piston slidably received in the container, and a moving device for moving the piston in a reciprocating motion within the container. For example, a motor is coupled to the piston with a crank to move the piston in a reciprocating motion within the container.

[0005] Patent application U.S. Patent Application No. 10 / 810,686 (U.S. Patent Application Publication No. 20050215850) discloses a syringe pump including a syringe having a plunger that slides on a body having a discharge port, a drive mechanism including a cylinder connected to the syringe and in which a piston attached to a shaft slides, a biasing device that operates to apply a biasing force to the piston to drive the piston in a distal direction with the cylinder, and a safety catch that initially prevents the biasing device from moving the piston, the safety catch being removable to allow the biasing device to move the piston.

[0006] 1 illustrates an example of an injection system 100 for injecting medical liquid from a medical liquid container 104 into a common line 102. Those skilled in the art will appreciate that the medical liquid container 104 may be any type of container specifically adapted to contain medical liquid, such as, but not limited to, a vial, a bottle, a plastic container, and any type of container manufactured to contain medical liquid. The injection system 100 includes a first connector 106 configured to be connected to the medical liquid container 104, an injector 108 to which an injection device 110 having a medical tubing interface 112 is attached, a medical liquid supply line 114 configured to connect the first connector 106 to the medical tubing interface 112 to supply the medical liquid to the injection device 110, and a common line 102 connected to the medical tubing interface 112 and the patient line 116 and configured to inject the medical liquid into the patient line 116. More precisely, a first piping valve 130 connects the liquid supply line 114 to the common line 102 and only allows passage to the common line 102 under vacuum pressure. The common line 102 includes a second piping valve 140 downstream of the first piping valve 130 and only allows passage towards the patient line 116. The infusion device 110 typically includes a body defining an interior space and a piston actuated by a plunger rod and configured to move within the interior space to pump fluid into or expel fluid from the interior space.

[0007] In the illustrated example, two different types of medical fluid are to be injected into the patient, and as a result, the injection system 100 is configured to connect to two medical fluid containers 104 using two different first connectors 106 and two different medical fluid supply lines 114. However, the injection system 100 may be configured to inject only one medical fluid. For simplicity, the following description is made with reference to a configuration in which only one medical fluid is injected, since a double injection simply involves replicating the described features. Here, "double injection" is understood to mean injecting twice.

[0008] For economic and ecological reasons (less use of plastics), multi-patient practices are steadily gaining market share. In the so-called multi-patient practice, the plumbing for the infusion system 100 comprises two very separate parts: the day set 120 and the patient set 122. The patient set 122 is changed for each patient. The patient set 122 is typically used to limit the risk of cross-contamination between successive patients and thus protect the day set. Once installed and ready, the day set 120 remains connected to the power injector for several patient cases, as long as the same medical fluid is injected. If the medical fluid to be injected needs to be changed, the day set 120 is changed. This day set 120 comprises a medical fluid container 104 and a medical fluid supply line 114 connected to the common line 102. The patient set 122 comprises a patient line 116, which is supplied with the medical fluid by the common line 102 and is connected to a catheter or needle for injecting the medical fluid into the patient.

[0009] When the injection system 100 is set to inject a medical liquid into a patient, it is important to ensure that there is no gas present in the tubing prior to injection. Injecting a gas, such as air, into the patient's blood vessels can result in gas embolism, i.e., blockage of the blood vessel caused by one or more bubbles of air or other gas in the circulatory system. When the day set 120 or patient set 116 is in place, the tubing fills with air. Therefore, it is necessary to evacuate any gas present in the tubing prior to injection. Due to the length of the tubing, a large amount of gas will be evacuated from the injection system 100.

[0010] To purge the injection system 100 from any gas present before injection, the injection device 110 fills the medical liquid supply line 114 by aspirating or drawing medical liquid from the medical liquid container 104. Here, the injection device 110 is filled with a mixture of medical liquid and gas. The injection device 110 is then placed with the medical tube interface 112 facing upwards so that the gas is collected at said medical tube interface 112. It is noted that the filling of the injection device 110 causes turbulence in the medical liquid, generating microbubbles in the medical liquid. Due to the high viscosity of medical liquids (especially for contrast media), the microbubbles may take several minutes to reach the medical tube interface 112. Therefore, it is customary to wait at least 2 or 3 minutes with the medical tube interface 112 facing upwards. Then, by actuating the piston, the gas is expelled from the injection device 110 through the still upward-facing medical tube interface 112 to the common line 102. A medical fluid is then injected into the common line 102 to push the gas out of the common line 102 , thereby purging the infusion system 100 .

[0011] During injection, it may occur that gas is present in the infusion set 110. For example, vaporization of the medical liquid may generate gas. Also, some gas bubbles generated during the initial filling of the infusion system 100 may be trapped against the tubing or walls of the infusion set 110 and may not be expelled during the initial purge. As a result, because the infusion set 110 is positioned with the medical tubing interface 112 facing downward during injection, any gas present in the infusion set 110 is contained in the infusion set 110, away from the medical tubing interface 112, and is not injected into the common line 102.

[0012] This approach has several disadvantages. First, the injector 110 must be moved between two opposing positions with the medical tubing interface 112 facing up or down. This requires that the injector 108 be able to rotate. Second, this purge takes a significant amount of time and the injection system 100 must be monitored by an operator during the purge. The operator must also assess the quality of the purge and whether it is complete. As with any human interaction, reliance on the operator can lead to errors. Third, the gas is pushed along the common line 102 by the medical liquid that is also exiting the injection system. This approach therefore involves wasting medical liquid and requires collecting the wasted medical liquid at the output of the injection system 100, with possible handling errors.

[0013] Also, gas still present in the infusion set 110 after purging can alter the operation of the infusion set, even if the gas is trapped in the infusion set 110. The dosage of medical liquid is usually controlled over the course of the piston of the infusion set 110. Gas is compressible, and therefore the change in the volume of the medical fluid inside the infusion set is imprecise. Also, the volume of gas trapped in the infusion set 110 must be small, otherwise there is a risk of it being injected into the common line 102.

[0014] Therefore, there is a need for an infusion system that can vent gas quickly and whenever gas is present in the infusion device without the need for any operator intervention. Summary of the Invention

[0015] 1. An injection device for injecting a medical liquid from a medical liquid container into a medical tube, comprising: a body defining a longitudinally extending interior space between an upper end of the body and a lower end of the body, the lower end of the body comprising a medical tubing interface through which medical fluid can pass from a medical fluid container through the interior space and exit said interior space to be injected into a medical tubing; - a piston disposed within the interior space and configured to move within the interior space along a longitudinal direction, the piston defining an upper volume and a lower volume of the interior space, the lower volume being configured to receive a medical fluid; a discharge path that crosses the piston longitudinally from the lower space to the upper space of the internal space; a float configured to float on the medical liquid and arranged in a cavity within the drainage path between a lower portion of the drainage path and a middle portion of the drainage path, said lower portion of the drainage path being connected to a lower space, said cavity comprising at least one passageway belonging to the drainage path, said float configured to move longitudinally within said cavity between a blocking configuration in which an obstruction portion of the float obstructs the passageway, thereby closing the drainage path, and an open configuration in which an obstruction portion 24a of the float moves away from the passageway, thereby opening the drainage path; Equipped with An injection device is proposed in which the float has a metacenter that is spaced from the top of the occlusion by a distance less than 1 / 3 of the height of the float.

[0016] Other preferred, non-limiting aspects of the present invention are the following, isolated or in any technically feasible combination: the float is configured to have a metacenter above a line of float between the medical liquid and the air when the float floats on the medical liquid; - the metacenter is spaced less than 0.50 cm from the apex of the occlusion; -The float's center of gravity is above the center of buoyancy. The float is configured to float on a float line in the medical liquid, and the center of gravity of the float is less than 1.0 cm from the float line; The float is configured such that when the float floats in the medical liquid, the float line is at a diameter of the float that corresponds to at least 80% of the maximum diameter of the float; - the float has a maximum diameter that is more than five times the maximum diameter of the cross section of the obstruction that obstructs the passage; - the float has a center of buoyancy at least 1.0 cm away from the top of the occlusion; - a volume of at least 1.0 mL of air is trapped in the cavity when the occlusion closes the passageway; The float comprises a top and a bottom, the top supporting the occlusion of the float and having a diameter that is smaller than or decreases from the bottom, In a blocking configuration in which the obstruction portion of the float blocks the passage, the surface of the bottom is 1.8 mm to 2.8 mm from the surface of the seat; The upper part has a convex outer surface towards the occlusion; The float is provided with a keel under the bottom. The present invention also relates to an injection system comprising: an injection device according to the invention, a first connector configured to be connected to a medical fluid container; a medical fluid supply line configured to connect the first connector to a medical tubing interface to supply the medical fluid to the infusion system; a common line connected to the medical tubing interface and to the patient line and configured to infuse the medical fluid into the patient line. [Brief description of the drawings]

[0017] Other aspects, objects and advantages of the present invention will become more apparent from a reading of the following detailed description of preferred embodiments thereof, given by way of non-limiting example and made with reference to the accompanying drawings, in which: [Figure 1] FIG. 1 is a general diagram of an injection system with two medical fluid containers connected thereto. [Diagram 2] FIG. 13 is a cross-sectional view of the piston of the injection device during the filling step before purging. [Diagram 3]FIG. 13 is a cross-sectional view of the piston of the injection device during the start of a purge. [Figure 4] FIG. 13 is a cross-sectional view of the piston of the injection device at the end of a purge. [Diagram 5] FIG. 13 is a cross-sectional view of the piston of the injection device during the injection step after purging. [Figure 6] FIG. 13 is a cross-sectional view of a piston showing the float in a shut-off position according to a possible embodiment. [Figure 7] 1 is a cross-sectional view of a float according to a possible embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] Detailed Description of the Invention The injection device of the present invention may be used in injection system 100, as previously described in connection with Figure 1. Injection system 100, with the exception of injection device 110, will not be described further.

[0019] Figures 2-5 show an example of an injection device that shares the same features as the claimed invention, except for the float design. Figures 2-5 and the corresponding description section are provided to enable a better disclosure of the invention, and all features disclosed in Figures 2-5 and the corresponding description section apply to the claimed invention, except for the float design.

[0020] 2-5, the infusion device 110 includes a body 2 defining an interior space 4 extending longitudinally between an upper end 2b of the body 2 and a lower end 2a of the body 2, the lower end 2a of the body having a medical tubing interface 112 through which medical liquid can penetrate the interior space 4 from a medical liquid container 104 and can exit said interior space 4 to be infused into a common line 102. In contrast to previous infusion devices, the infusion device 110 according to the present invention is configured to stay down with the medical tubing interface 112. Terms relating to space such as "down", "up", "lower", "upper", "higher", "highest" and the like should be understood as defining commonly accepted relative positions to the vertical, i.e. the direction of local earth gravity. This is because gases and medical liquids are subject to gravity, and the present invention utilizes gravity to provide for proper gas evacuation. As a result, in use, the lower end 2a of the body 2 is located below the upper end 2b of the body 2. The body 2 is typically a hollow cylinder made of, for example, glass or plastic material, also called a barrel.

[0021] The injection device 110 also includes a piston 6 arranged in the internal space 4 and configured to move in the internal space 4 along the longitudinal direction, i.e. between the upper end 2b of the body 2 and the lower end 2a of the body 2. The piston 6 defines an upper space 4b and a lower space 4a of the internal space. The lower space 4a is configured to receive a medical liquid, while the upper space 4b is not intended to receive any liquid. The piston 6 provides an airtight seal between the upper space 4b and the lower space 4a. For this purpose, the piston 6 is provided with at least one peripheral seal 8 or 10, for example made of rubber, preferably two peripheral seals 8, 10 at different heights along the longitudinal direction. Each peripheral seal 8, 10 is pressed against the wall of the body 2 to ensure a seal. As in the illustrated example, the peripheral seals 8, 10 may be four-rings, but may also be O-rings, for example.

[0022] Due to the tight seal provided by the piston 6, the pressure can vary greatly between the upper space 4b and the lower space 4a of the internal space 4. The pressure inside the upper space 4b is roughly fixed and kept at a reference pressure that is substantially independent of the path of the piston 6. This reference pressure is typically atmospheric pressure, e.g. the pressure of the environment of the system. Preferably, the upper end 2b of the body 2 is at least partially open so that the pressure inside the upper space 4b corresponds to atmospheric pressure, independent of the path of the piston 6. Conversely, the pressure inside the lower space 4a of the internal space 4 depends on the contents of said lower space 4a and the path of the piston 6. In the following description, overpressure is a pressure above the reference pressure and vacuum pressure is a pressure below the reference pressure.

[0023] The piston 6 is attached to the piston rod 12, for example by a protrusion 14 on the top of the piston 6 that engages said piston rod 12. The piston rod 14 is driven by an injector 108 to move the piston 6 along the longitudinal direction inside the interior space 4. The piston 6 can be formed by several parts assembled together. In the illustrated example, the piston 6 has a lower part 6a, a middle part 6b, and an upper part 6c. Connectors such as screws 16 can be used to assemble the piston parts.

[0024] The piston 6 has a discharge path arranged inside the piston 6. This path traverses the piston 6 in the longitudinal direction from the lower space 4a to the upper space 4b of the internal space 4. The discharge path is intended to discharge the gas present in the lower space 4a to the upper space 4b. Typically, the discharge path is not linear, and can be opened and closed at different points depending on the components of the piston 6, as described below. More specifically, the discharge path includes a lower portion 17a, a middle portion 17b, and an upper portion 17c. The lower portion 17a of the discharge path is connected to the lower space 4a, and the upper portion 17c of the discharge path is connected to the upper space 4c. The middle portion 17b is between the lower portion 17a and the upper portion.

[0025] The piston 6 includes a lower interface 18 that defines a lower space 4a of the internal space 4, said lower interface 18 having an inlet 20 of the discharge path. Preferably, the inlet 20 opens at the highest part of the lower interface 18 in order to properly discharge all gas present in the lower space to the lower interface 18 without any gas being trapped in the lower space 4a of the internal space. Preferably, the lower interface 18 has a surface with an apex toward the upper end 2b of the body, and the inlet 20 of the discharge path opens at said apex. For example, the lower interface 18 has a convex surface as viewed from the lower space 4a of the internal space, and the inlet 20 of the discharge path opens in the center of said lower interface 18, as in the example shown. For example, the surface of the lower interface 18 may correspond to the surface of a cone, a truncated cone, or a pyramid facing upwards. Alternatively, the lower interface 18 may have a concave surface as viewed from the lower space 4a of the internal space, and the inlet 20 of the discharge path opens at the periphery of said lower interface 18. For example, the lower interface 18 may have a groove disposed about the periphery of the lower interface 18, and the exhaust passage inlet 20 may open in the groove.

[0026] The piston 6 includes a purge valve 22 arranged in the discharge path between the middle part 17b of the discharge path and the upper part 17c of the discharge path. The purge valve 22 is configured to move between a blocking configuration, in which the purge valve 22 closes the discharge path, and a passing configuration, in which the purge valve 22 keeps said discharge path open. The passing configuration of the purge valve 22 requires an overpressure in the middle part 17b of the discharge path relative to a reference pressure in the upper space 4b, caused by the piston 6 moving towards the lower end 2a of the body 2. Since the upper space 4b is at a reference pressure (e.g. atmospheric pressure), overpressure means a pressure above the reference pressure. More precisely, the overpressure required for the passing configuration of the purge valve 22 corresponds to the pressure in the middle part 17b exceeding the reference pressure in the upper space 4b and the upper part 17c of the discharge path by at least a first pressure threshold. The purge valve 22 is configured to be in the blocking configuration when the piston 6 moves towards the upper end of the body 2. This is because there is no overpressure in the intermediate portion 17a relative to the reference pressure in the upper space 4b, but instead there is a vacuum pressure, i.e. a pressure below the reference pressure.

[0027] The piston 6 also includes a selector 24 disposed within the discharge path between the lower portion 17a of the discharge path and the middle portion 17b of the discharge path. The selector 24 is configured to selectively allow gas to pass through the selector 24 and travel along the discharge path from the lower portion 17a to the middle portion 17b of the discharge path. The selector 24 is also configured to selectively prevent medical liquid from passing through the selector 24 and traveling along the discharge path from the lower portion 17a to the middle portion 17b of the discharge path, and thus traveling along the discharge path from the lower space 4a to the upper space 4b of the interior space. As a result, the lower portion 17a of the discharge path is a mixed portion configured to receive both medical liquid and gas, and the middle portion 17b and the upper portion 17c are gaseous portions configured to receive only gas.

[0028] The purge valve 22 is disposed above the selector 24 in the longitudinal direction, from the lower space 4a to the upper space 4b of the internal space. Therefore, the purge valve 22 is disposed in the gas portion of the discharge path and does not come into contact with any liquid.

[0029] In the shut-off configuration, the purge valve 22 seals the vent 26 between the middle portion 17b and the upper portion 17c of the exhaust path. In the through configuration, the purge valve 22 opens said vent 26. In the illustrated example, two vents 26 appear between the middle portion 17b and the upper portion 17c of the exhaust path. More or fewer vents 26 can be provided, as long as they can be sealed by the purge valve 22.

[0030] Preferably, as shown in the illustrated embodiment, the purge valve 22 is an umbrella valve having a diaphragm-shaped sealing disk 22a and a stem 22b. The stem 22b engages in a hole 28 arranged in a fixed part of the piston 6 and presents an enlarged lower part with an upper cross section than the cross section of the hole 28, thereby fixing the purge valve 22. The diaphragm-shaped sealing disk 22a is arranged above at least one vent 26 that is part of the discharge path and defines the upper part 17c to the middle part 17c of the discharge path. The umbrella valve can deformably and / or slidably move along the hole 28 arranged in the fixed part of the piston 6 to change its configuration (e.g. by deformation of the stem). In the passing configuration, the sealing disk 22a is away from the vent 26 due to the higher pressure of the gas inside the middle part 17b, thereby allowing the gas to pass through said vent 26. In the shutoff configuration, the higher pressure of the gas inside the upper portion 17c of the exhaust path causes the sealing disk 22a to press against the vent 26, thereby sealing said vent 26 and closing the exhaust path. For example, the umbrella valve can be made of a rubber-type elastomer, or silicone.

[0031] The selector 24 is a float 24 configured to float in the medical fluid.

[0032] The process for operating an injection device having a float 24 as a selector will now be described with reference to Figures 2 to 5.

[0033] In Fig. 2 the injection device 110 is shown before purging, e.g. during a filling step, during which the injection device 110 is filled with medical liquid and undesired gas. During this filling step the piston rod 12 is driven upwards, e.g. by an injector 108 acting on said piston rod 12, thereby moving the piston 6 longitudinally, i.e. upwards, in the interior space 4 towards the upper end 2b of the body 2. The lower space 4a expands, as a result of which the pressure of the gas inside said lower space 4a falls below the reference pressure of the gas inside the upper space 4b, e.g. atmospheric pressure.

[0034] Since the selector 24 allows gas to move from the lower part 17a to the middle part 17b of the exhaust path, a reduced pressure in the lower space 4a is also found in the lower part 17a and in the middle part 17b of the exhaust path. However, since the purge valve 22 needs to bring the overpressure in the middle part 17b of the exhaust path to the passing configuration, the purge valve 22 is maintained in the blocking configuration. More precisely, the purge valve 22 is pushed downwards and seals the vent 26, thereby closing the exhaust path in the blocking configuration.

[0035] The combination of the closing of the exhaust path by the purge valve 22 and the expansion of the lower space 4a effectively creates a vacuum pressure in the lower space 4a, i.e. a pressure below the reference pressure. The pressure in the lower space 4a decreases until it reaches the opening pressure of the first piping valve 130, which is, for example, 0.2-0.5 bar below the reference pressure. The opening of the first piping valve 130 creates a suction of medical liquid to compensate for this vacuum pressure in the lower space 4a. The medical liquid is filled into the lower space 4a through the fill line 114 connected to the medical liquid container 104. Any gas present in the piping is also sucked into the lower space 4a.

[0036] Gradually, as the lower space 4a fills with medical liquid or gas, the pressure inside the lower space 4a rises and approaches atmospheric pressure. When the pressure inside the lower space 4a reaches the closing pressure (substantially similar to the opening pressure) of the first piping valve 130, the first piping valve 130 closes and filling stops. At the end of the filling step, the lower space 4a is filled with a certain amount of gas 32 that exceeds the certain amount of medical liquid 34. Because the pressure rise was stopped by closing the first piping valve 130 before the vacuum pressure was fully compensated, the pressure of the gas inside the lower space 4a is still lower than the pressure of the gas inside the upper space 4b. As a result, the purge valve 22 remains in the shutoff configuration.

[0037] As mentioned above, after filling the injection device 110, the gas in the lower space 4a must be evacuated during purging. This purging is performed by driving the piston 6 downwards, as shown in FIG. 3. The piston 6 moves inside the inner space 4 along the longitudinal direction towards the lower end 2a of the body 2. The lower space 4a shrinks and the gas pressure in the lower space 4a increases until the pressure difference between the gas pressure in the middle part 17b that remains in communication with the lower space 4a and the reference gas pressure in the upper space 4b becomes higher than the opening pressure threshold of the purge valve 22, i.e. until the pressure difference reaches a first pressure threshold.

[0038] As mentioned above, the purge valve 22 is configured to move to the through configuration in response to the overpressure in the lower volume 4a exceeding the reference pressure in the upper volume 4b by at least the opening pressure threshold of the purge valve 22 (e.g., the pressure difference between the overpressure and the reference pressure of 20-100 mbar). This causes the purge valve 22 to move to the through configuration, thereby opening the exhaust path. In the illustrated example, the sealing disk 22a moves away from the vent 26, thereby unsealing said vent 26.

[0039] Gas is discharged from the lower space 4a to the upper space 4b of the interior space 4 through a discharge path that crosses the piston 6. More specifically, the gas enters the discharge path through the inlet 20, then along the lower part 17a of the discharge path, then along the middle part 17b of the discharge path, then through the vent 26, and finally along the upper part 17c to reach the upper space. This is shown by the dotted arrows in FIG. 3.

[0040] When the piston 6 moves downwards while gas is being discharged through the discharge path, the piston reaches a certain amount of medical liquid in the lower space 4a. More specifically, the lower interface 18 comes into contact with the medical liquid and the gas is pushed back towards the inlet 20 of the discharge path as the inlet 20 opens at the highest part of said lower interface 18. This causes the gas to be discharged from the lower space 4a before the medical liquid reaches the inlet 20 of the discharge path. When all the gas is discharged, the medical liquid penetrates the inlet 20 of the lower interface 18 of the piston 6 and fills the lower part 17a of the discharge path.

[0041] As shown, the lower portion 17a of the drainage path may include a cavity 36 into which the selector 24 is positioned so that the medical fluid begins to fill the cavity 36. The selector is a float 24 configured to float in the medical fluid, and the cavity 36 is configured to allow the float 24 to move up and down the cavity 36 along a longitudinal direction. The cavity 36 includes at least a passageway 38 that forms a boundary between the lower portion 17a and the middle portion 17b of the drainage path. The passageway 38 is positioned at the top of the cavity 36. The float 24 is configured to move longitudinally within the cavity 36 between a blocking configuration in which the float 24 occludes (i.e., blocks) the passageway 38, thereby closing the drainage path, and an open configuration in which the float 24 moves away from the passageway 36, thereby opening and not blocking the drainage path.

[0042] More precisely, when the cavity 36 is filled with gas 32, the float 24 remains at the bottom of the cavity 36, keeping the passageway 38 open and thereby not blocking the drainage path. When the medical liquid reaches the cavity 36, the float 24 starts to float on the medical liquid and therefore rises, carried by the medical liquid 34, according to the upward buoyant force exerted on the float by the medical liquid (Archimedes' principle). Under this force, the float 24 moves upwards until it reaches the top of the cavity 36, blocking the passageway 38.

[0043] The passage 38 is defined by a periphery forming a seat 40 for the float 24 facing said float 24. The float closes the passage 38 by pressing the seat. The seat 40 is made of metal or plastic, for example thermoplastic polyurethane, polyoxymethylene, polycarbonate, polyvinyl chloride, etc. Advantageously, the seat 40 is made of a material having a modulus of elasticity higher than 2500 mpa (megapascals). Preferably, the seat 40 has a cross section that decreases in the direction of the middle part 17b of the discharge path, for example the shape of the seat 40 is at least partially a hollow truncated cone. A reinforcing element 42, such as a washer, can be provided above the seat 40 to strengthen it, especially if said seat is made of a highly deformable material.

[0044] As shown in the illustrated example of FIG. 6, the float 24 has at least an obstruction portion 24a configured to obstruct (e.g., block or block) the passage 38. Typically, the passage 38 has a circular cross-section, and the obstruction portion 24a of the float 24 also has a circular cross-section. For example, the obstruction portion 24a of the float 10 may have an at least partially elliptical shape, or a spherical or pine-tree conical shape. For example, the float 24 may simply be a ball. Preferably, the obstruction portion 24 of the float is coated with a deformable material to better seal the passage 38 when the float 24 is pressed against the seat 40.

[0045] Preferably, the float 24a has a floating portion 24b with an enlarged portion relative to the widest portion of the obstruction portion 24a, said floating portion 24b supporting the obstruction portion 24a. The float may be in two parts as in Figs. 1-5, or may be a single part including the obstruction portion 24a and the floating portion 24b. The obstruction portion 24a of the float 24 is, for example, a ball. The floating portion 24b of the float 24 has a diameter larger than the widest diameter of the obstruction portion 24a, i.e. the ball portion, of the float. The larger the diameter of the floating portion 24b of the float 24 (perpendicular to the longitudinal direction), the more responsive the float 24 is to a low force exerted on it by the medical liquid 34. This improved response allows the medical liquid to push the float 24 upwards as soon as it reaches the float 24, thus ensuring that the medical liquid cannot reach the passage 38 before said passage is obstructed by the float 24.

[0046] When the medical liquid 34 comes into contact with the float 24, for example with the floating part 24b of the float 24, the float 24 starts to float and thus moves upwards, as shown in FIG. 4, until it reaches the seat 40. The shape of the float 24 and the shape of the seat 40 are adapted so that a continuous seal is created when the float 24 presses against the seat 40. Now, the passage 38 is blocked and neither the gas nor the medical liquid can pass through the blocked passage 38. A small amount of gas can be trapped inside the cavity 36 between the blocked passage 38 and the surface of the medical liquid 34, i.e. in the lower part of the drainage path. This small volume makes it possible to keep the seat dry and to avoid any accumulation of material on the seat 40. The small volume can be, for example, a volume of less than 10 ml at atmospheric pressure. This small amount of air can be sufficient to dry the float 24. The density of the float 24 and the complementary shapes of the occlusion portion 24a and the sheet 40 are selected to minimize the volume of trapped air while keeping the surface of the medical fluid away from the sheet 40. For example, the cross section of the sheet may decrease in the direction of the middle portion 17b of the drainage path.

[0047] When the passage 38 is blocked, gas can no longer reach the middle part 17b escaping the overpressure in the lower part 17a of the exhaust path. As a result, the pressure in the middle part 17b above the blocked passage 38 drops until the difference between the pressure in the middle part 17b and the reference pressure reaches the closing pressure threshold of the purge valve 22, which is slightly above the reference pressure since the upper space 4b is at said reference pressure. For example, the closing pressure threshold of the purge valve 22 can correspond to a positive pressure difference between the pressure inside the middle part 17b and the reference pressure of 20 to 100 mbar. Preferably, the closing pressure threshold and the open-close valve threshold are substantially the same, but they may also be different. As a result, the purge valve 22 is now closed in a shut-off configuration (FIG. 5). In this example, the sealing disk 22a covers the vent 26. The purge step is finished. A small amount of gas 32 with a residual overpressure (i.e. slightly higher than the reference pressure) is retained in the middle part 17b. The residual overpressure is not high enough to force the purge valve 22 to open the vent 26. This residual overpressure ensures that air at atmospheric pressure coming from the head space 4b cannot penetrate the middle part 17b of the exhaust path, thus avoiding non-sterile air entering the sterile area where the medical fluid circulates.

[0048] The process may include a complementary filling step, which is performed after the purging step and before the injection step, allowing the lower space 4a to be filled with a precise predetermined medical liquid volume 34, which was not possible in the first filling step due to the volume of gas 32, which resulted in an erroneous volume measurement (usually based on the course of the piston 36).

[0049] The process may include an injection step, in which the piston moves in the inner space along the longitudinal direction toward the lower end 2a of the body, and the medical liquid leaves said lower space of the inner space and is injected into the medical tube. When the discharge path is closed, the pressure inside the lower space 4a increases when the piston 6 is pressed down. When the pressure in the lower space 4a reaches the opening pressure of the second piping valve 140, the second piping valve 140 opens, and the medical liquid 34 can leave the lower space 4a and travel through the common line 102 to reach the patient line 116. This allows the medical liquid to be injected without any gas. During injection, the float 24 comes into contact with the medical liquid.

[0050] Note that the opening pressure threshold (i.e. the first pressure threshold) of the purge valve 22 is lower than the opening pressure threshold (the second pressure threshold) of the second line valve 140, so that the purge valve 22 opens before the second line valve 140 opens when gas is exhausted. However, during this injection step, the blockage of the passage 38 by the selector (float 24) means that pressure increases in the lower space 4a but not in the isolated middle part 17b of the exhaust path. The purge valve 22 is therefore kept in the shutoff configuration.

[0051] As described above, the float 24 transitions between an open configuration in which the obstruction portion 24a of the float 24, 50 moves away from the passage 38 to open the exhaust path, and a blocked configuration in which the obstruction portion 24a of the float 24 blocks the passage 38 to close the exhaust path.

[0052] Since the float 24 floats on the medical fluid, the occlusion 24a blocks the passage 38 before the medical fluid reaches the passage 38. Air is trapped in the cavity 36. When the occlusion 24a of the float 24 blocks the passage 38, the pressure in the cavity 36 increases, the volume of trapped air decreases, and the medical fluid approaches the occlusion 24a. It is preferable to keep the medical fluid away from the occlusion 24a of the float. If the occlusion 24a becomes wet, in the long term, droplets of medical fluid may leak out in the drainage path. Since the float 24 is lightweight, another risk is that the wet occlusion 24a will adhere to the passage 38, for example due to surface tension. This is particularly important in that different medical fluids can have various densities and the float 24 should be able to function properly with low density medical fluids and high density medical fluids.

[0053] To avoid any medical liquid from entering the passageway 38, and preferably coming into contact with the occlusion 24a, it is desirable to ensure that sufficient air, which can be referred to as an air mattress protecting the occlusion 24a, is trapped in the cavity 36. When the occlusion 24a closes the passageway 38, a volume of at least 1.0 mL, preferably more than 2.0 mL, and possibly more than 3.0 mL, should be trapped in the cavity 36. When the occlusion 24a closes the passageway 38, the trapped air can be considered to be at atmospheric pressure (approximately 1013 hPa or 1 atm). However, the trapped air volume should not be too large. If the trapped air volume is too large, it may be difficult to manage the pressure inside the lower space 4a, since air is compressible. Preferably, the trapped air volume should be less than 10.0 mL, preferably less than 5.0 mL, when the occlusion 24a closes the passageway 38.

[0054] It may be advantageous to reintroduce air into the cavity 36 after several injections in the absence of gas to purge, so as to have enough trapped air to keep the obstruction 24a dry. It is possible to take advantage of the fact that the purge valve 22 can leak air under a small negative pressure (for example between 0 and -200 mbar) into the middle part 17b of the discharge path, below the purge valve 22 and thus through the passage 38 into the cavity 36. The step of air introduction to reintroduce air into the cavity 36 may be carried out from time to time, for example periodically. In this step, a regenerative negative pressure is created in the middle part 17b of the discharge path below the purge valve 22, for example by moving the piston 6 upwards. The regenerative negative pressure is above the opening pressure or cracking pressure of the first pipe valve 130 or the filling valve, and is typically above -200 mbar and below -20 mbar, for example -150 mbar. This does not result in a fill of medical fluid, but the purge valve 22 allows air that has passed through the middle portion 17b of the drain path to escape and penetrate the cavity 36 through the passage 38 that is no longer blocked by the float 24. Thus, air is introduced into the cavity 36 to ensure that enough air is trapped inside to keep the occlusion 24 dry.

[0055] The regenerative negative pressure does not have to be constant, but is maintained for a certain period of time, such as 2 to 10 seconds, depending on the leak rate of the purge valve 22, to allow for sufficient air to be introduced. For example, the regenerative negative pressure is maintained between 10% and 80% of the opening or cracking pressure of the first piping valve 130, typically including between -10 and -200 mbar, and preferably between 50 and 180 mbar.

[0056] The center of buoyancy B of the float 24 can also be considered to ensure that the passageway 38 is blocked while the medical fluid is moving away from the occlusion 24a. More specifically, the center of buoyancy B of the float 24 should be spaced away from the occlusion 24a, and more precisely, the float has a center of buoyancy B that is spaced away from the top of the occlusion 24a by more than half the height of the float, and preferably at least two-thirds the height of the float. The center of buoyancy B of the float 24 is the center of gravity of the displaced volume of fluid corresponding to the volume of the float 24. This is the center of the volume of the float 24.

[0057] In one embodiment of the present disclosure, the center of buoyancy B of the float 24 is longitudinally spaced from the top 24c of the occlusion 24a by at least 1.0 cm, preferably at least 2.0 cm, more preferably at least 3.0 cm. Typically, the center of buoyancy B of the float 24 may be no more than one-third of the longitudinal height of the float 24 from the bottom to the top occlusion 24a.

[0058] Due to the distance between the center of buoyancy B and the top of the occlusion 24a, the float is pushed upwards early by the medical fluid towards the passageway 38. Thus, the occlusion 24a of the float 24 occludes the passageway 38 while the medical fluid is away from the occlusion 24a, with a sufficient volume of trapped air to protect the occlusion 24a even after high pressure is applied (e.g., greater than 15.0 bar, preferably greater than 20.0 bar).

[0059] Stability is important because as soon as the obstruction 24a reaches the height of the passage 38, the obstruction 24a should face the passage 38 to ensure that the passage 38 closes immediately. The float 24 has a metacenter M that is spaced from the top of the obstruction 24a by a distance less than 1 / 3 of the height of the float 24 (along the longitudinal direction), preferably less than 1 / 4 of the height of the float 24. For example, the metacenter M is spaced from the top of the obstruction 24a by less than 1.0 cm, preferably less than 0.50 cm. When the float 24 floats in a liquid (e.g., with a density of 1, e.g., up to a density of 1.44 or more), the float 24 may tilt, and the center of buoyancy B of the float 24 will move. The metacenter M is the point where a vertical line passing through the tilted center of buoyancy B intersects with a line passing through the original vertical center of buoyancy B, and is the metacenter M. Preferably, the float 24 is configured to have a metacenter above the line of float between the medical fluid and the air when the float 24 floats in the medical fluid.

[0060] With reference to Figures 6 and 7, a non-limiting example of an injection device with a float that allows sufficient air to be trapped in accordance with the claimed invention is described. Figure 6 shows an example of a float 24 in a blocking position that blocks the passageway 38. Figure 7 shows an alternative configuration of the float 24 in cross section. The float 24 is shaped to form a center of buoyancy B that is spaced (longitudinally) from the top 24c of the occlusion. Preferably, the float 24 is at least partially hollow, preferably more hollow at the top than at the bottom. The top 24c of the occlusion 24a preferably has an at least partially spheroidal shape, typically hemispherical.

[0061] From top to bottom, float 24 comprises an occlusion portion 24a, a top portion 50, and a bottom portion 52. Top portion 50 supports occlusion portion 24a of float 24 and has a smaller diameter than and / or a decreasing diameter from bottom portion 52. The diameters are measured transverse to the longitudinal direction. Bottom portion 52 supports top portion 50. Top portion 50 increases in diameter from occlusion portion 24a to bottom portion 52. Preferably, bottom portion 52 is heavier than top portion 50 and occlusion portion 24a.

[0062] The top 50 and / or bottom 52 have a maximum diameter that is greater than the maximum diameter of the occluded portion 24a of the float. The larger the diameter of the bottom 52 of the float 24 (perpendicular to the longitudinal direction), the more responsive the float 24 is to the lower forces exerted on the float 24 by the medical fluid 34. This improved response allows the medical fluid to push the float 24 upward as soon as it reaches the float 24, thus ensuring that the medical fluid cannot reach the passageway 38 before said passageway is occluded by the float 24.

[0063] In the example of Fig. 6, the top 50 comprises a lower intermediate portion 50b and a stem 50a projecting upward from the intermediate portion 50b. Along the length, toward the occlusion 24a, the cross-sectional diameter of the intermediate portion 50b decreases, while the cross-sectional diameter of the top 50 remains substantially constant. It is also possible for the diameter to decrease continuously along the top 50, as in Fig. 7. In this case, the top can have a convex outer surface toward the occlusion 24a to aid in draining medical fluids downward. The diameter of the bottom portion 52 may decrease at least partially downward.

[0064] The float 24 is at least configured such that the float line L when the float 24 floats in the medical liquid is at least 80% of the maximum diameter of the float 24, preferably at least 90% of the maximum diameter of the float 24, more preferably at the maximum diameter. The float 24 has a maximum diameter greater than the maximum cross-sectional diameter of the obstruction portion 24a obstructing the passageway 38, for example, greater than twice the maximum cross-sectional diameter of the obstruction portion 24a, preferably greater than five times the maximum cross-sectional diameter of the obstruction portion 24a. For example, the maximum diameter of the float 24 can be greater than 1.5 cm, preferably greater than 2.5 cm. In these examples, the maximum diameter of the float 24 is shared by the top portion 50 and the bottom portion 52 at their joint, but this is not a requirement. The maximum cross-sectional diameter of the float 24 may be only at the top portion 50 or the bottom portion 52.

[0065] To achieve maximum stability, the float 24 is configured such that the float or water line when the float 24 floats in the medical fluid is at the maximum diameter (perpendicular to the longitudinal direction) of the float 24, or at a diameter corresponding to at least 80% of the maximum diameter of the float 24, where the water line or float line represents the interface between the water entrained as the medical fluid and the air above.

[0066] The larger the diameter of the float 24 (perpendicular to the longitudinal direction), the more responsive the float 24 is to the low force exerted on it by the medical fluid 34. This improved response allows the medical fluid to push the float 24 upward as soon as it reaches the float 24, thus ensuring that the medical fluid cannot reach the passageway 38 before said passageway is blocked by the float 24. The larger cross-section of the float 24 also increases the force exerted by the occlusion portion 24a in the blocking configuration, improving the tightness of the seal of the passageway 38.

[0067] At least the occlusion 24a may be separate, for example made of semi-rigid materials such as TPE-U, TPE-S, TPE-E, silicone rubber, liquid silicone rubber, or other materials with hardness Shore including 30ShA to 95ShA, more advantageously about 70ShA, while the rest of the float 24 is made of harder materials such as PC, PA, PE, PP, or other raw materials with a higher mechanical resistance between 200mPa and 2500mPa, around 800mPa. The float 24 can be made in one piece, with some material such as a high density plastic core at the bottom, on which a body of a low density material such as a foam material is molded. The occlusion 24a is then molded on top. It is also possible to assemble the float from different parts. For example, the top 50 and bottom 52 of the float may be made in one piece, and the occlusion 24a is molded or added on top. The top 50 and bottom 52 may also be separate or joined to each other, as in the example of FIG. 7.

[0068] The upper peripheral surface 44 of the cavity 36 is the surface of the piston 6 that defines the upper portion of the cavity and leads to the seat 40 in which the passage 38 is located. The float 24 does not contact the upper peripheral surface 44 of the cavity 36, even in the closed configuration. The upper peripheral surface 44 surrounds an opening 46 that engages with a portion of the upper section 50, such as the stem 50a. The opening 46 opens into the seat 40. The closure 24a extends beyond the opening 46 to the seat 40 and the passage 38. Preferably, the closure 24a is always above the opening 46, even in the open configuration, so that the float 24 is always correctly positioned with the closure 24a facing the passage 38.

[0069] To further guide the float 24 toward the passage 38, the seat 40 may have a guide portion 40a that surrounds the closure portion 24a and possibly a portion of the upper section 50, such as a stem 50a, that is engaged beyond the opening 46.

[0070] To improve the efficiency of the trapped air and protect the occlusion 24a, it is desirable for the trapped air volume to reach a medical volume that remains a distance away from the occlusion 24a. Preferably, the upper section 50 of the float 24 and the upper peripheral surface 44 of the cavity 36 have complementary shapes that minimize the volume of air trapped in the gap 36a between the outer surface of the upper section 50 and the corresponding opposing upper surface of the cavity 36 (FIG. 6).

[0071] For example, the section of the cavity 36 may decrease in the direction of the passage 38, as may the outer surface of the upper section 50. However, the gap 36a must not be too small in order to avoid the medical fluid being trapped in the gap 36a and blocking possible movement of the float 24 due to capillary and surface tension phenomena.

[0072] Preferably, the minimum or average distance d1 of the air gap 36a between the outer surface of the upper section 50 and the upper peripheral surface 44 of the corresponding opposing cavity 36 when the passageway 38 is closed is at least 1.8 mm, preferably at least 2.0 mm. To avoid having excessive trapped air, the maximum or average distance d1 of the air gap 36a between the outer surface of the upper section 50 and the upper peripheral surface 44 of the corresponding opposing cavity 36 when the passageway 38 is closed is at most 3.0 mm, preferably at most 2.7 mm, more preferably at most 2.5 mm. Or more generally, the majority of the distances d1 of the air gap 36a between the outer surface of the upper section 50 and the upper peripheral surface 44 of the corresponding opposing cavity 36 when the passageway 38 is closed is at least 1.8 mm, preferably at least 2.0 mm. The majority of the distances d1 of the air gaps 36a between the outer surface of the upper section 50 and the upper peripheral surface 44 of the corresponding opposing cavity 36 when the passageway 38 is closed are at most 3.0 mm, preferably at most 2.7 mm, more preferably at most 2.5 mm. The air gaps 36 are preferably rotationally symmetric about their longitudinal direction. For example, the distances are measured along a normal to the outer surface of the upper section 50 and / or the corresponding opposing upper peripheral surface 44 of the cavity 36.

[0073] To provide stability, the float 24 should have at least some axial symmetry about the longitudinal axis, and preferably the float 24 has rotational symmetry about the longitudinal axis. By keeping the float 24 straight with respect to the longitudinal axis, the obstruction portion 24a can always face the passage 38. This allows the obstruction portion 24a to obstruct the passage 38 without colliding with the sheet 40 surrounding the passage 38 when the float 24 is pushed up by the medical fluid. To improve the stability of the float 24, the center of gravity G of the float 24 is preferably above the center of buoyancy B.

[0074] When the float 24 floats on water (density 1), preferably even liquids with densities up to 1.44, such as highly concentrated drugs, the center of gravity G of the float 24 is less than 1.0 cm, preferably less than 0.5 cm, from the float line (interface between the medical liquid and the air). Preferably, the center of gravity G of the float 24 is below the water line. Preferably, the float has a metacentric height (i.e., the distance between the center of gravity G of the float 24 and the metacentric M of the float 24) less than 2.0 cm, preferably less than 1.5 cm, from the top of the occlusion portion 24a of the float.

[0075] The top 50 can function as a guide to guide the occlusion 24a. To further guide the float 24 in the cavity 36, the float 24 can include a keel 56 below the bottom 52 that extends longitudinally downward from the center of the bottom 52. The keel 56 has a diameter at least one-fifth less than the maximum diameter of the bottom 52. For example, the keel 56 extends along at least 0.4 cm, and preferably less than 1.0 cm.

[0076] Although the present invention has been described with respect to certain preferred embodiments, it is clear that the invention is in no way limited thereto, but includes all technical equivalents of the described means and combinations thereof. It will be clear to those skilled in the art that various changes and modifications can be made without departing from the scope of the invention, in particular as defined in the appended claims.

Claims

1. An injection device (110) for injecting medical liquid from a medical liquid container into a medical tube, - A main body (2) comprising a main body (2) having a longitudinally extending internal space (4) defined between the upper end (2b) and the lower end (2a) of the main body (2), wherein the lower end of the main body has a medical tube interface (112) through which the medical liquid can penetrate the internal space (4) from the medical liquid container and exit the internal space (4) so ​​as to be injected into the medical tube (112), - A piston (6) disposed inside the internal space (4) and configured to move within the internal space (4) along the longitudinal direction, the piston (6) defining an upper space (4b) and a lower space (4a) of the internal space, the lower space (4a) being configured to receive the medical fluid, - A discharge path that traverses the piston (6) in the longitudinal direction from the lower space (4a) to the upper space (4b) of the internal space, - A float (24) configured to float in the medical liquid and positioned in a cavity (36) inside the discharge path between the lower part (17a) and the middle part (17b) of the discharge path, wherein the lower part (17a) of the discharge path is connected to the lower space (4a), the cavity (36) comprises at least one passage (38) belonging to the discharge path, and the float (24) is configured to move along the longitudinal direction inside the cavity (36) between a blocking configuration in which the blocking portion (24a) of the float (24) blocks the passage (38), thereby closing the discharge path, and an opening configuration in which the blocking portion (24a) of the float (24) is separated from the passage (38), thereby opening the discharge path, Equipped with, The injection device (110) has a float (24) that, when the float (24) floats in a liquid having a density between 1 and 1.44, has a metacenter (M) that is separated from the top of the occluded portion (24a) by a distance of less than 1 / 3 of the height of the float (24).

2. The injection device according to claim 1, wherein the float (24) is configured such that when the float (24) floats in the medical liquid, the metacenter (M) is located above the buoyancy line between the medical liquid and the air.

3. The injection device according to any one of claims 1 to 2, wherein the metacenter (M) is separated from the top of the occluding portion (24a) by less than 0.50 cm when the float (24) is floating in the liquid.

4. The injection device according to claim 1, wherein when the float (24) floats on the liquid, the center of gravity (G) of the float is above the center of buoyancy (B).

5. The infusion device according to claim 1, wherein the float (24) is configured to float in the medical liquid by means of a buoyancy wire, and when the float (24) floats in the liquid, the center of gravity (G) of the float is less than 1.0 cm from the buoyancy wire of the float.

6. The injection device according to claim 1, wherein the float (24) is configured such that the buoyancy line when the float (24) floats in the medical liquid is the diameter of the float (24) which corresponds to at least 80% of the maximum diameter of the float (24).

7. The injection device according to claim 1, wherein the float has a maximum diameter exceeding twice the maximum diameter of the cross-section of the blocking portion that blocks the passage (38).

8. The injection device according to claim 1, wherein the float has a center of buoyancy that is separated by at least 1.0 cm from the top of the occluded portion (24a) when the float (24) floats in the liquid.

9. The injection device according to claim 1, wherein at least 1.0 mL of air is sealed in the cavity (36) when the passage (38) is closed by the occlusion portion (24a).

10. The injection device according to claim 1, wherein the float comprises an upper part and a bottom part (52), the upper part supporting the closed part (24a) of the float and having a diameter smaller than the diameter of the bottom part (52), or a diameter decreasing from the bottom part (52).

11. In the blocking configuration in which the closing portion (24a) of the float (24) blocks the passage (38), the surface of the bottom portion (52) is 1.8 mm to 2.8 mm from the surface of the sheet, the injection device according to claim 10.

12. The injection device according to claim 11, wherein the upper part has a convex outer surface toward the closed portion (24a).

13. The injection device according to claim 1, wherein the float is provided with a keel (56) below the bottom (52).

14. An injection system (100), - The injection device (110) described in claim 1, - A first connector (104) configured to be connected to a medical liquid container (104), - A medical fluid supply line (114) is configured to supply the medical fluid to the injection system, with the first connector (104) connected to the medical tube interface (112), - An injection system (100) comprising a medical tube interface (112) and a common line (102) configured to be connected to the patient line (116) for injecting the medical fluid into the patient line.

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