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EP-3727507-B1 - PRESSURE SENSOR FOR INJECTION DEVICES

EP3727507B1EP 3727507 B1EP3727507 B1EP 3727507B1EP-3727507-B1

Inventors

  • HELMER, MICHAEL

Dates

Publication Date
20260506
Application Date
20181219

Claims (11)

  1. A medicament delivery device (1) comprising: a medicament container (3) comprising medicament container walls and a sealing element (11); a stopper (9) translatably disposed inside the medicament container; and a plunger (19) passing through an axial bore (21) of the sealing element, the plunger being operable to displace the stopper, wherein the sealing element, stopper and medicament container walls define a cavity (13) inside the medicament container, characterised in that : the plunger comprises one or more slits extending along a sidewall of the plunger, wherein the one or more slits fluidly connect the cavity to an external atmosphere when the plunger is at a pre-defined depressed position, and the one or more slits do not extend into the cavity when the plunger is in an undepressed position, thereby sealing the cavity; and the medicament delivery device comprises a pressure sensor (15), wherein the pressure sensor is configured to measure the pressure inside the cavity to determine a start time and end time of an injection, wherein the pressure sensor is configured to identify a start time of an injection based on a decrease in pressure within the cavity to below a first threshold value and to identify an end time of an injection based on an increase in pressure within the cavity to above a second threshold value.
  2. The medicament delivery device (1) of claim 1, wherein the pressure sensor (15) is configured to determine an injection duration from measurements of the pressure inside the cavity (13).
  3. The medicament delivery device (1) of claim 2, wherein the pressure sensor (15) is configured to detect a plateau in the measurements of the pressure inside the cavity (13) to determine the injection duration based on the length of the plateau.
  4. The medicament delivery device (1) of claim 2 or 3, wherein the pressure sensor (15) is configured to determine the injection duration based on the difference in the start time and the end time.
  5. The medicament delivery device (1) of any preceding claim, wherein the sealing element (11) comprises a valve extending from an inner wall of the axial bore for allowing air into the cavity when the negative pressure inside the cavity exceeds a threshold value.
  6. The medicament delivery device (1) of any preceding claim, wherein the pressure sensor (15) is located outside the cavity (13).
  7. The medicament delivery device (1) of claim 6, wherein the sealing element (11) comprises one or more conduits (17) fluidly connecting the cavity (13) to the pressure sensor (15).
  8. The medicament delivery device (1) of any preceding claim wherein the medicament delivery device is an autoinjector, the autoinjector comprising a drive mechanism for actuating the plunger.
  9. The medicament delivery device (1) of any preceding claim, further comprising a medicament (5).
  10. The medicament delivery device (1) of any preceding claim, wherein the first threshold value is the same as the second threshold value.
  11. The medicament delivery device (1) of any preceding claim, wherein the first threshold value is different to the second threshold value.

Description

FIELD OF INVENTION The present application relates to pressure sensors for injection devices. In particular, it relates to pressure sensors for monitoring injection times in injection devices. BACKGROUND Monitoring a patient's injection regime can provide useful information regarding the patient's compliance with the regime and whether the patient is using their injection equipment correctly. One set of information that can be useful is an indication and/or record that an injection has occurred. Another is the injection duration. This can be indicative of the amount of medication expelled by the injection equipment during the injection. It can also indicate whether the injection device is working properly. This can be particularly important in autoinjector devices. WO2018/083062 A1, an earlier filed but later published patent application, discloses a measuring arrangement for measuring of a volume change of a liquid medium located inside a liquid reservoir, the measuring arrangement comprising: - a gas tight enclosure having an interior volume containing a gas reservoir and containing the liquid reservoir, wherein the liquid reservoir is filled with a liquid medium, - a gas inlet in flow connection with the gas reservoir and extending through a boundary of the gas tight enclosure to an exterior of the gas tight enclosure, - an outlet connectable with the liquid reservoir and extending through the boundary of the gas tight enclosure, - wherein the gas reservoir and the liquid reservoir are hermetically separated by an impenetrable separation wall, and - a flow meter arranged in or across the gas inlet to measure an ingress of a gaseous medium through the inlet in response to a withdrawal of the liquid medium from the liquid reservoir through the outlet. US 5370630 A discloses a device for injection of fluidic materials into body tissue includes a syringe and an injection housing. The syringe includes a first end, a second end, a hollow barrel, a plunger, and a rod which extends through the second end of the syringe. The housing further includes a first end, a second end, and a bore. The first end of the housing is disposed in juxtaposed relationship with the second end of the syringe. The rod extends beyond the second end of the housing. A piston travels within the bore in a reciprocal fashion, and cooperates with the rod in a ratchet-like fashion. The piston engages the rod as the piston travels toward the first end of the housing, and disengages from the rod as the piston travels toward the second end of the housing. The plunger of the syringe is thereby advanced in increments, each of which is translatable to a specific volume of fluidic material. SUMMARY The invention is defined in the independent claim. According to a first aspect, the specification discloses a medicament delivery device comprising: a medicament container comprising medicament container walls and a sealing element; a stopper translatably disposed inside the medicament container; a pressure sensor; and a plunger passing through an axial bore of the sealing element, the plunger being operable to displace the stopper, wherein the sealing element, stopper and medicament container walls define a cavity inside the medicament cartridge; and wherein the pressure sensor is configured to measure the pressure inside the cavity. The pressure sensor may be configured to determine an injection duration from measurements of the pressure inside the cavity. The pressure sensor may be configured to detect a plateau in the measurements of the pressure inside the cavity to determine the injection duration based on the length of the plateau. The pressure sensor may be configured to detect a start time of the injection and an end time of the injection and to determine the injection duration based on the difference in the start time and the end time. The pressure sensor may be configured to identify a start of an injection based on a decrease in pressure within the cavity to below a threshold value. The sealing element may comprise a lip extending from an inner wall of the axial bore for allowing air into the cavity when the negative pressure inside the cavity exceeds a threshold value. The pressure sensor may be located outside the cavity. The sealing element may comprise one or more conduits fluidly connecting the cavity to the pressure sensor. The medicament delivery device may be an autoinjector, the autoinjector comprising a drive mechanism for actuating the plunger. The plunger may further comprise one or more slits, the slits fluidly connecting the cavity to an external atmosphere when the plunger is in a pre-defined depressed position, for example a defined end of injection postion. The medicament delivery device may further comprise a medicament. According to a second aspect, the specification also describes a method of determining an injection duration comprising: monitoring air pressure in a cavity of a medicament container using a pressure sensor;