Fill amplification structure for injection devices

Abstract

A medical fluid injection device has an injection device housing with a bladder expansion space therein. A resilient expandable bladder is positioned within the bladder expansion space. A fill indicator is attached to a distal end portion of the bladder. An injection needle is carried by the housing. An injection flow path is in communication between the injection needle and the bladder. A port in the housing receives medical fluid under pressure from a source. An inlet fluid flow path in the housing communicates between the inlet port and bladder for introducing medical fluid into the bladder. A fill amplification member is positioned within the bladder expansion space and at least partially surrounds the bladder so as to restrict radial expansion of at least a portion of the bladder as medical fluid is introduced into the bladder.

Description

Docket No.: 8002-0070.01 FILL AMPLIFICATION STRUCTURE FOR INJECTION DEVICES Inventors: Muhammad Junaid Akbar, Kory Gunnerson, David Stefanchik and Daniel E. Waites Claim of Priority

[0001] This application claims priority to and the benefit of U.S. Provisional Patent Application No.63 / 709,323, filed October 18, 2024, the contents of which are hereby incorporated by reference in their entirety. Field of the Disclosure

[0002] The present application generally relates to injection devices for medical fluids and more particularly to a fill amplification structure and corresponding method that may be used to amplify fill level indications for injection devices. Background

[0003] Development efforts have continued in recent years with regard to injection devices for injecting medical fluids, such as drugs, antibiotics, vaccines, biologics and other medicaments into patients for therapeutic and / or diagnostic purposes. Examples of such injection devices may be found in U.S. Patent Nos. 9,925,333 to Hooven et al.; 11,033,680 to Dunki-Jacobs et al.; 11,040,138 to Hooven et al. and PCT International Patent Application Publication No. WO 2024 / 137969 to Stefanchik et al. each of which are assigned to Enable Injections, Inc. of Cincinnati, Ohio USA, and the contents of each of which are hereby incorporated by reference herein.

[0004] The injection devices referenced above employ an internal reservoir in the form of a resilient balloon or bladder that expands as it is filled with medical fluid from the transfer device. The injection device may, after filling, be removed from the transfer device and placed on the skin of a patient and activated. Upon activation, an injection needle is advanced from the device into the skin of the patient and the inherent pressure provided by the expanded resilient reservoir forces the medical fluid through the needle and into the patient.Docket No.: 8002-0070.01

[0005] A fill indicator is attached to the end portion of the bladder where, as noted above, the bladder enlarges when the injection device is being filled with a drug and contracts when the drug is being dispensed. A window on the injection device shows the relative movement of the indicator so that the amount of drug in the injection device bladder is shown. At partial fill volumes, such as a 10 ml fill of an injection device having 20 ml or 25 ml fill capacity (as an example only), the indicator movement is limited. It is therefore desirable to amplify the indicator’s movement to get full or nearly full travel of the indicator even at partial fill volumes to provide a higher resolution of indicated fill level for the injection device. The amplification provides clarification that a dose is being given by helping the user see movement of the indicator with higher resolution. Summary

[0006] The following non-limiting summary is to acquaint the reader generally with various potential aspects of the present subject matter and is non-exclusive with respect to the various possible aspects or combinations of aspects found in such device or method. Additional aspects of the present subject matter may be found in the detailed description below, in the accompanying claims and / or in the accompanying figures.

[0007] In accordance with one aspect of the disclosure, a medical fluid injection device includes an injection device housing having a bladder expansion space therein. A resilient expandable bladder is positioned within the bladder expansion space. A fill indicator is attached to a distal end portion of the bladder. The housing includes an outlet port. An injection flow path is provided for fluid communication between the bladder and the outlet port. An inlet port in the housing receives medical fluid under pressure from a source. An inlet fluid flow path in the housing communicates between the inlet port and bladder for introducing medical fluid into the bladder. A fill amplification structure is positioned within the bladder expansion space and at least partially surrounds the bladder so as to restrict radial expansion of at least a portion of the bladder as medical fluid is introduced into the bladder.Docket No.: 8002-0070.01

[0008] In accordance with another aspect of the disclosure, a fill amplification structure is configured to be inserted into a bladder expansion space of an injection device having a resilient expandable bladder positioned in the bladder expansion space for holding medical fluid. The fill amplification structure is configured to at least partially surround the bladder so as to restrict radial expansion of at least a portion of the bladder as medical fluid is introduced into the bladder.

[0009] In accordance with another aspect of the disclosure, a process for adjusting sensitivity of a fill indicator to a fill volume of medical fluid in an injection device having a bladder expansion space with a resilient expandable bladder positioned in the bladder expansion space for holding medical fluid, where a fill indicator is attached to a distal potion of the bladder, includes the steps of inserting a fill amplification structure into the bladder expansion space and at least partially surrounding the bladder with the fill amplification structure so as to restrict radial expansion of at least a portion of the bladder as medical fluid is introduced into the bladder.

[0010] In accordance with another aspect of the disclosure, a medical fluid injection device includes an injection device housing having a bladder expansion space therein. a resilient expandable bladder is positioned within the bladder expansion space. A fill indicator is attached to a distal end portion of the bladder. The housing includes an outlet port. A n injection flow path is in flujd communication between the bladder and the outlet port. A fill amplification structure is positioned within the bladder expansion space and at least partially surrounds the bladder so as to restrict radial expansion of at least a portion of the bladder by medical fluid in the bladder.

[0011] These and other aspects of the present subject matter are set forth in the following more detailed description and accompanying figures. Brief Description of the Drawings

[0012] Fig.1 is a perspective view of a prior art injection device suitable for use with embodiments of the fill amplification structure of the disclosure.Docket No.: 8002-0070.01

[0013] Fig.2 is a vertical cross-sectional side elevation view of the injection device of Fig.1 connected to a prior art transfer device.

[0014] Fig.3 is an exploded perspective view of certain parts of the injection device of Figs.1 and 2.

[0015] Fig.4 is a vertical cross-sectional side elevation view of the injection device and a portion of the transfer device of Figs.1-3.

[0016] Fig.5 is a horizontal cross-sectional top plan view of the injection device of Figs.1-4.

[0017] Fig.6 is a perspective view of a rigid insert embodiment of the fill amplification structure of the disclosure.

[0018] Fig.7 is a perspective view of the rigid insert of Fig.6 mounted in an injection device with the top portion of the housing of the injection device removed.

[0019] Fig.8 is a horizontal cross-sectional perspective view of the injection device and rigid insert of Fig.7.

[0020] Fig.9 is an exploded perspective view of a multi-piece embodiment of the rigid insert and an injection device with the top portion of the housing of the injection device removed.

[0021] Fig.109is a horizontal cross-sectional top plan view of the injection device and fill amplification structure of Fig.8.

[0022] Fig.11 is a horizontal cross-sectional top plan view of an injection device provided with an alternative embodiment of a rigid insert fill amplification structure.

[0023] Fig.12 is a horizontal cross-sectional top plan view of an injection device provided with another alternative embodiment of a rigid insert fill amplification structure.

[0024] Fig.13 is a perspective view of the rigid insert of Fig.12.

[0025] Fig.14 is a plot of fill indicator motion vs bladder fill volume for an injection device with the rigid insert of Figs.12 and 13 in comparison with a baseline for an injection device without the rigid insert.

[0026] Fig.15 is a top plan view of the injection device of Fig.12 with three regions of physical geometry and stepped inner diameters indicated.Docket No.: 8002-0070.01

[0027] Fig.16 is a plot of dispense pressure vs bladder fill volume for the injection device with insert of Figs.12, 13 and 15 illustrating the three regions of Fig.15.

[0028] Fig.17 is a plot of fill indicator position vs bladder fill volume for the injection device with insert of Figs.12, 13 and 15 illustrating the three regions of Fig.15.

[0029] Fig.18 is a plot of the average position of the fill indicators of Figs.10- 12 vs bladder fill volume during filling of the bladder in comparison with a baseline for an injection device without the rigid insert.

[0030] Fig 19 is a plot of the average position of the fill indicators of Figs.10-12 vs bladder fill volume during bladder dispensing in comparison with a baseline for an injection device without the rigid insert.

[0031] Fig.20 is a perspective view of a spring embodiment of the fill amplification structure of the disclosure.

[0032] Fig.21 is a second perspective view of the spring embodiment of the fill amplification structure of Fig.20 with a fill indicator and dolphin-shaped bladder connector added.

[0033] Fig.22 is a perspective view of an injection device equipped with the spring fill amplification structure of the disclosure.

[0034] Fig.23 is a vertical cross-sectional perspective partial view of the injection device and spring fill amplification structure of Fig.21.

[0035] Fig.24 is a top plan view of an injection device with the top portion of the housing removed illustrating a molded ridge embodiment of the fill amplification structure of the disclosure. Detailed Description

[0036] Disclosed here are devices and methods that amplify fill indicator motion for an injection device to provide full or fuller travel of the indicator with partial fills of an injection device. Such a capability provides greater resolution with regard to the indicated fill level of an injection device and use of an injection device over a broader range of fill levels.Docket No.: 8002-0070.01

[0037] As illustrated for purposes of explanation and not limitation, Fig.1 illustrates a prior art injection device, indicated in general at 14, suitable for use with embodiments of the fill amplification structure of the disclosure. As described in greater detail in previously mentioned and commonly assigned U.S. Patent Nos.9,925,333 to Hooven et al.; 11,033,680 to Dunki-Jacobs et al.; 11,040,138 to Hooven et al. and PCT International Patent Application Publication No. WO 2024 / 137969 to Stefanchik et al., the injection device includes a housing 50 with an activation button 16 that is pressed by a user to initiate an injection once the device is secured to a patient via adhesive positioned on the bottom surface 18 of the housing.

[0038] As described in previously mentioned U.S. Patent Nos.9,925,333 to Hooven et al. and 11,033,680 to Dunki-Jacobs et al., as well as commonly assigned U.S. Patent No.11,571,361 to Bourelle et al. and U.S. Patent Application Publication No. US 2023 / 0285243 to Drach et al., the contents of each of which are also hereby incorporated by reference, a transfer device, not illustrated, allows the transfer medical fluid, which may be any injectable fluid such as for diagnostic or therapeutic purposes including, without limitation, drugs, antibiotics, chemotherapy or similar agents, biologics or other medicament, from a fluid source such as a vial or a standard syringe to the injection device 14.

[0039] As seen in Fig.2, a prior art transfer device may include a first connector or port 24 for connection to a fluid source such as a syringe, a second connector port or mating member 26 for cooperation with the injection device 14 and a fluid flow path 28 connected between them. The first connector 24 is shown with the upper syringe receiving portion in section, illustrating a female luer port 30 for receiving the typical male Luer end of a syringe type fluid source. The first connector has an internal passageway, not shown, that extends from the luer port 30 to the flow path 28. The fluid flow path 28 may be of any suitable construction such as flexible plastic tubing, a rigid pre-formed flow path or other. As used herein, the word, “upper,” lower,” “above,” “below” and similar words are only indicative of relative positional relationships among various features and are not otherwise intended to impose limitations of direction.Docket No.: 8002-0070.01

[0040] The second connector 26 is situated in the tray 18 beneath the injection device receiving station or recess 22. The fluid flow path 28 is connected to an inlet port 32 of the second connector and an internal flow path 34 in the second connector extends from the inlet port 32 to an outlet port 36. Optionally, the internal flow path includes a hydrophobic filter such as hydrophobic membrane 38 covering a connector vent opening 40 to allow gas bubbles in the medical fluid to vent to the ambient atmosphere, while preventing liquid from flowing through the filter, and another filter such as membrane 42 through which the fluid must pass to remove particulate or other undesired materials from the fluid. In the illustrated transfer device, the internal flow path 34 extends through a relatively thin and wide cavity or region 44. One side of the cavity communicates through the hydrophobic membrane 38 with gas vent opening 40 in the connector wall. On the opposite side of the cavity, the membrane 42 extends over the second connector outlet port 36. The relatively thin height of the cavity promotes contact of any entrained bubbles with the hydrophobic membrane, while the relatively large cavity width provides a large cross section for fluid flow through the cavity.

[0041] The second connector 26 includes an upstanding support member 46 to help support the underside of the injection device. The outlet port 36 of the second connector also extends upwardly toward the underside of the injection device. A rigid fluid transfer tube 48 extends from the outlet port 36 for insertion into an inlet port of the injection device 14.

[0042] With continued reference to Fig.2, the injection device housing 50 encloses a resilient, expandable fluid reservoir such as an arcuate resilient bladder 52. The injection device housing has a fluid inlet port 54 for receiving the fluid transfer tube 48 and a fluid flow path, generally at 56, that extends between the inlet port and the reservoir. A one-way flow control valve 58 is located in the fluid flow path to control fluid flow between the inlet port and the reservoir, allowing medical fluid to flow from the inlet port to the reservoir and substantially preventing fluid flow from the reservoir to the inlet port.

[0043] With reference to Fig.3, the valve 58 includes a valve body 70 and a valve member 72. The valve body is provided with a flow lumen 74 that directs medical fluid from the inlet port into a manifold 60 due to the one-way operation ofDocket No.: 8002-0070.01 valve member 72. The flow lumen may optionally be provided with a fluid absorbent member 82.

[0044] With continued reference to Fig.3, the illustrated manifold is generally V-shaped, with a valve housing 62 at the vertex of the V-shaped manifold, a bladder mounting member 64 on one leg of the V-shaped manifold and a needle housing 66 on the other leg of the V-shaped manifold. The fluid flow path 56 extends into the valve housing 62 and branches at the valve housing and extends from the valve housing along each leg of the V-shaped manifold. This can be better seen in Figs.4 and 5 which show the fluid flow path branch 56a, which extends through the bladder mounting member 64, and the fluid flow path branch 56b, which extends to needle housing 66.

[0045] Referring to Fig.5, the bladder mounting member 64 extends into an open end of an arcuate resilient bladder 52. The open end of the bladder is secured to the mounting member by a circumferential o-ring 68 that resides in a slot 70 around the mounting member and clamps the bladder wall 71 against the surface of the mounting member. The fluid flow path 56a discharges into the bladder, and Fig.5 shows the resilient bladder as expanded after filling. When filled, the expanded resilient bladder inherently applies pressure to the fluid contained therein, and provides the motive force for expelling the fluid through an injection needle 100 (Fig.4) when the injection device is later activated. In alternative embodiments, such as where an external tube set and corresponding needle or cannula are provided, the injection device may include a housing outlet port that receives the fluid from the expanded bladder for expulsion from the housing. In such an embodiment, the tube set is attached to the housing outlet port and directs the fluid to the needle or cannula. The flow control valve 58 allows filling of the bladder under pressure from a medical fluid source (e.g. a syringe) and prevents the pressurized fluid in the filled bladder from escaping through the inlet port 54.

[0046] With reference to Fig.5, the distal end of the arcuate resilient bladder 52 is affixed an indicator 101, which is constrained to follow the bladder expansion space 104 (also indicated in general at 104 in Fig.3) defined by the inner surfaces 106 (Fig.3) of the housing 50.Docket No.: 8002-0070.01

[0047] It is desirable to have the bladder 52 fill and empty along its length in a controlled way, from one end to the other to encourage the expandable member 52 to completely empty, and to allow the easy and accurate measurement of fluid in the expandable member.

[0048] To visually aid in determining how much fluid is in the bladder, with reference to Fig.1, the injection device housing may be provided with a window, such as a clear portion 103 of the housing 50, through which the indicator 101 may be viewed with graduated markings, such as those indicated at 105, to indicate the volume remaining in the bladder.

[0049] With reference to Fig.5, the injectable or medical fluid in the bladder 52 is preferably expelled progressively from the distal end 118 of the bladder towards the proximal end 122, where the proximal end of the bladder is closest to the dispensing needle or cannula of the injection device. This allows the user to visually ascertain or approximate the injection status visually alone or with the aid of graduation markings (105 of Fig.1) on a window or clear portion 103 the injection device housing or adjacent to the window.

[0050] As explained in greater detail below, embodiments of the disclosure provide a fill amplification structure that is inserted around the bladder and which restricts the available space for the bladder to expand radially and instead, causes the bladder to elongate sooner with lower fill volumes. Embodiments of the fill amplification structure may include a rigid insert that’s dropped into the bladder expansion space, a spring insert which is wrapped around the bladder, or ribs or similar protrusions or structures molded into inner surfaces of the housing that extend along the bladder expansion space. Concepts of the disclosure rely fundamentally on restricting the available space for the bladder to expand radially to get higher movement at lower fill volumes.

[0051] An embodiment of a fill amplification structure of the disclosure may take the form of a rigid insert, indicated in general at 128 in Fig.6. The rigid insert 128 features a longitudinally arcuate body 130 having a concave and curved inner wall 132 that defines a channel, indicated in general 134. The inner wall 132 features an inner diameter or radius, indicated by arrow 140 in Fig.6. The arcuate body 130 also includes an outer surface 136 that is provided withDocket No.: 8002-0070.01 recesses 138. As an example only, the rigid insert 128 may be molded or otherwise formed from plastic.

[0052] The rigid insert 128 is illustrated in Figs 7 and 8 after installation in an injection device, indicated in general at 142. The injection device 142 features a construction similar to the injection device of Figs.1-5. In both Figs.7 and 8, the top portion of the housing of the injection device 142 has been removed, and only the bottom portion 144 of the housing is present. The bladder expansion space 146 is illustrated in both Figs.7 and 8. The entirety of the inserted rigid insert 128 is shown in Fig.7 while the rigid insert has been bisected by a horizontal cutting plane with the bottom portion visible in Fig.8.

[0053] As illustrated in Figs.6 and 7, the rigid insert 128 is installed in the bladder expansion space 146 of an injection device so that at least a portion of the arcuately expandable bladder 152, shown in an unfilled condition in Fig.8, is received within the channel 134. As in the prior art injection device of Figs.1-5, an indicator 158 is attached to the distal end of the bladder 152 so that it traverses at least a portion of the bladder expansion space 146 as the bladder is filled with liquid medicine through fill passage 157 (Fig.8). The top portion of the housing of the injection device (not shown in Figs.6-8), as shown for the injection device of Fig.1, features a window with graduated markings through which the position of the indicator 158 may be viewed so as to indicate the fill condition of the bladder 152.

[0054] As illustrated in Figs.7 and 8, the recesses 138 of the rigid insert 128 receive and engage ribs 154 formed within the injection device 142 along the inner surface 156 of the curved outer wall defining the bladder expansion space 146. As a result, the rigid insert is secured in a fixed position within the housing of the injection device without the use of adhesive so that it does not move as the bladder fills and empties of liquid medication. Alternative structures may be used in the place of ribs 154 of Fig.8 (such as, for example only, pins with corresponding recesses in the rigid insert) and / or the recesses may alternatively be formed in the injection device with the structures formed on the rigid insert. In another alternative, the ribs 154 and recesses 138 may be eliminated with adhesive used to secure the rigid insert within the injection device instead.Docket No.: 8002-0070.01

[0055] The insert can be placed either before or after the bladder assembly is installed in the injection device housing allowing for ease of assembly. Furthermore, the rigid insert reduces injection device manufacturing costs by expanding the range of liquid medication fill amounts that may be accommodated by an injection device that otherwise would only have a single fill capacity. This reduces the number of different injection device component sizes (for example, housing sizes, housing window graduations, bladder sizes, etc.) that would otherwise need to be produced. Rigid inserts having differing dimensions to accommodate different fill levels, but that may be installed in the same single injection device, are inexpensive to produce compared to the costs of manufacturing entire multiple injection devices providing a corresponding variety of fill sizes.

[0056] The rigid insert 128 provides a restricted radial expansion space for the bladder 152. As a result, the bladder 152 contacts the inner wall 132 of the channel 134 as it fills with liquid medicine and the indicator moves from the “Empty” position illustrated in Figs.7 and 8 to the “Full” position indicated at 160 in Fig.8 after moving in the direction of arrow 162. Restriction of radial expansion of the bladder leads to amplification of axial expansion of the bladder, and thus amplification of movement of the fill indicator around the arcuate length of the expansion space within the injection device, when a given volume of medical fluid is introduced into the bladder. While the rigid insert 128 is illustrated as having an arcuate body 130, the body instead may be straight for use in an injection device having a linear bladder expansion space.

[0057] In addition, while the rigid insert 128 is illustrated as a single piece in Figs.6 and 7, it may be instead initially formed and / or inserted into the injection device as multiple pieces, such as upper half 129a and lower half 129b of Fig.9, while maintaining the same volumetric impact with regard to restricting the expansion of bladder 152. This may aid in the insertion of the fill amplification structure into, and / or the assembly of, the injection device. For example, with continued reference to Fig.9, rigid insert upper half 129a may be provided with recesses 139a while rigid insert lower half 129b may be provided recesses 139b. During assembly, the rigid insert lower half 129b may be positioned within theDocket No.: 8002-0070.01 bladder expansion space 146 of the bottom portion 144 of the housing of the injection device 142 so that recesses 139b engage ribs 154. The bladder 152, indicator 158, bladder connection component 176, and associated components, may then be installed in the injection device. This may be followed by positioning of the rigid insert upper half 129a on the lower half 129b with recesses 139a being engaged by ribs of the injection device housing top portion (mirroring the ribs 154 of the housing bottom portion 144) when the housing top portion is installed. The rigid insert upper half 129a may also optionally be secured to the lower half 129b with adhesive.

[0058] While two pieces upper half 129a and lower half 129b are illustrated for the multi-piece rigid insert of Fig.9, the multi-piece rigid insert may instead feature more than two pieces.

[0059] The dimensions of the rigid insert 128, including inner diameter size 140 (Fig.6) and arcuate length (172a-172c of Figs.10-13-), dictates how much amplification of the injection device fill level, as displayed by indicator 158, is achieved. The rate at which the indicator 158 travels through the bladder expansion space 146 during selected portions of the fill can be adjusted by changing the inner diameter 140 and arcuate length of the rigid insert.

[0060] The rigid insert may be tailored to have different motion profiles for lower fill volumes (for example, 3 ml) while using an injection device otherwise suited for larger fill volumes (for example, 20 or 25 ml).

[0061] As illustrated in Fig.109 for example, the rigid insert 128a may have an arcuate length 172a whereby it features a proximal end 178a that extends from approximately the distal end of the bladder fill passage 157, and corresponding inlet 174 into the bladder 152, to a distal end 180a at the initial, unfilled position of the indicator 158.

[0062] Wrapping the proximal end of the insert closer to the dolphin-shaped bladder connection component 176 (as illustrated by insert proximal ends 178b and 178c and arcuate lengths 172b and 172c in Figs.11 and 12, respectively) provides a higher pressure at the end of dispense of liquid medication from the injection device during an injection. This can be advantageous to prevent stallsDocket No.: 8002-0070.01 by providing a higher pressure right at the end of dispense ensuring last bit of trapped liquid in the bladder 152 escapes.

[0063] As further indicated by arcuate 172c of Fig.12, the distal end 180c of the rigid insert 128c may alternatively be positioned short of the initial, unfilled position of the indicator 158 (in contrast to distal ends 180a and 180b of rigid inserts 128a and 128b). In addition, as illustrated in Figs.12 and 13, the inner diameter of the inner wall 132c of the channel 134c may be provided with sections 192 and 194 having differing inner diameters, where sections 192 and 194 are arranged in a step fashion. Section 190 is sized and positioned to wrap the dolphin-shaped bladder connector. Such dimension adjustments permit the indicator 158 to be correctly positioned to indicate that the injection device is full when a low fill volume (such as between 0 and 3 ml) is introduced into the bladder 152 and may be used to control dispense pressure of the bladder during an injection.

[0064] For the injection device and rigid insert 128c of Figs.12 and 13, a plot of the position of the fill indicator (158 in Fig.12 and 101 in Fig.1) in terms of angle (about a point through the center of the injection device, indicated at 159 in Fig.1), as indicated by arrows 182 in Fig.1 between the initial, unfilled indicator position 184 (corresponding to the positions of indicator 158 in Fig.12) and the fully filled position 186, is provided in Fig.14. The fill indicator angle (along the Y- axis of Fig.14) is plotted against the fill volume (along the X-axis of Fig.14) up to 3.0 ml whereby a fill indicator angle of 20° in Fig.14 equates to the fully filled position 186 of Fig.1. An improperly extended distal end of the rigid insert (i.e. further towards the indicator 158 in Fig.12) or lack of a stepped inner diameter within the channel of the rigid insert may cause the indicator to move past the fully filled position illustrated at 186 in Fig.1 when the bladder contains 3.0 ml of liquid medication so as to cause the injection device to indicate and “overfill” condition.

[0065] As an example only, an embodiment of the injection device with an embodiment of the rigid fill insert provides a component that can control the bladder expansion chamber shape to be customizable to any fill volume between 3 ml to 10 ml, such that it always results in the same full gas gage range (movement of the indicator) in an angle being 20° to 70°.Docket No.: 8002-0070.01

[0066] A baseline plot for an injection device without the rigid insert is also provided in Fig.14 for comparison.

[0067] Three rigid insert zones overlaid on the device of Figs.12 and 13 are presented in Fig.15 where the insert 128c is configured to provide a 10 ml fill. The corresponding graphs of Figs.16 and 17 illustrate how regions of physical geometry and stepped inner diameters, such as regions 190, 192 and 194 illustrated in Figs.12 and 13 for the inner wall 132c of channel 134c of rigid insert 128c, impact the dispense pressure of the bladder 152 of Figs.12 and 15 during an injection and the corresponding motion of indicator 158 of Figs.12 and 15.

[0068] Plots of the average position of the fill indicators 158 of Figs.10-12 (corresponding to fill indicator 101 in Fig.1) in terms of angle, as indicated by arrows 182 in Fig.1 between the initial, unfilled indicator position 184 (corresponding to the positions of indicators 158 in Figs.10-12) and the fully filled position 186, for injection device filling and dispensing are provided in Figs.18 and 19, respectively. The fill indicator angle (along the Y-axis of Fig.13) is plotted against the fill volume (along the X-axis of Fig.13) up to 10.0 ml whereby a fill indicator angle of approximately 68° in each of Figs.18 and 19 equates to the fully filled position 186 of Fig.1.

[0069] Baseline plots for injection devices without rigid inserts are also provided in Figs.18 and 19 for comparison.

[0070] Additionally, the rigid inserts described above may provide the capability of engaging a premature lockout feature of the injection device disclosed in commonly assigned PCT International Patent Application Publication No. WO 2024 / 137969 to Stefanchik et al., the contents of which are hereby incorporated by reference, at a lower fill due to quicker expansion of the bladder. This may make the injection device more robust by ensuring the injection device activation button does not go into lockout prematurely.

[0071] An alternative embodiment of the fill amplification structure of the disclosure is indicated in general at 200 in Figs.20 and 21. The fill amplification structure 200 includes a coiled, low stiffness spring 202 that is sized to fit around the bladder of the injection device to constrain radial expansion of the bladder andDocket No.: 8002-0070.01 force it to expand at lower fill volumes. As examples only, the spring 202 may be constructed of metal or plastic.

[0072] The distal end of the spring 202 is provided with a fill indicator 204 (Fig. 21) that engages the distal end of the bladder such as by a notch or opening that is engaged by a corresponding fitting on the distal end of the bladder. An alternative connection may be used to secure the fill indicator 204 to the distal end of the bladder. As in the case of previous embodiments, the fill indicator 204 may be viewed through a window (such as window 103 with graduation markings 105 of Fig.1) on the injection device housing to indicate the fill level of the injection device.

[0073] As described with reference to Fig.8 above, and illustrated in Fig.22, an injection device (indicated in general at 206 in Fig.22) includes a number of ribs 208 formed along the inner surface 212 of the outer wall defining the bladder expansion space 214. As illustrated in Fig.22, coils near the proximal end of the spring 202 sit in between the ribs 208 of the housing for grounding purposes. As a result, the proximal end of the spring is secured in a fixed position within the housing of the injection device without the use of adhesive so that it does not move as the bladder fills and empties of liquid medication. Alternative structures and / or adhesive may be used in the place of ribs 208 of Fig.22 to secure the proximal end of the spring 202 within the bladder expansion space. As an example only, and illustrated in Fig.21, the proximal end of the spring 202 may be secured to the dolphin-shaped bladder connector 216 (described previously).

[0074] As illustrated in Fig.23, the bladder 218 passes through the coils of the spring 202 so that expansion of the bladder is restricted. As the bladder expands, it expands along the pathway defined by the bladder expansion space 214, and the spring also expands along the pathway. This provides the benefit of a reduction in the friction acting on the expanding bladder by the walls bordering the bladder expansion space. As a result, the spring 202 both reduces friction and provides volume constraint during filing of the bladder. Furthermore, the spring itself may be provided with an easily visible color to provide an added visual aid (visible through the previously mentioned housing window) for how much drug is remaining in the injection device.Docket No.: 8002-0070.01

[0075] The spring 202 coils include inner diameters, indicated by arrow 222 of Fig.23, which may be selected based on the anticipated fill volume for the injection device. In addition, the coils of the spring 202 may each feature the same inner diameter 222, or the inner diameters of the spring coils may be varied to provide the desired movement of the indicator 204 (Figs.21 and 22) and fill and dispense pressure profiles for the bladder 218 (Fig.23).

[0076] A potential alternative to the above removable fill amplification structures includes, with reference to Fig.24, manufacturing the injection device 300 with protrusions such as ribs 302 molded or otherwise formed within the housing halves. The ribs 302 therefore form a fill amplification structure that may provide the same geometry as a rigid insert or a spring insert, but with the advantage of being molded in and therefore reducing part counts. The molded (or otherwise formed) ribs 302 would accomplish the same task of reducing radial expansion and make the bladder elongate sooner therefore providing amplification in the same manner as the rigid insert and spring.

[0077] While the innovations herein are described by reference to specifically illustrated structures shown in the accompanying figures, it is understood that the present subject matter is not limited to such specific structures and has application in other forms and devices without departing from the scope of this disclosure. For this reason, reference is required to the following claims to ascertain the scope of the present subject matter.

Claims

Docket No.: 8002-0070.01 Claims What is claimed is:

1. A medical fluid injection device comprising: an injection device housing having a bladder expansion space therein; a resilient expandable bladder positioned within the bladder expansion space; a fill indicator attached to a distal end portion of the bladder; an outlet port in the housing; an injection flow path for flujd communication between the bladder and the outlet port; an inlet port in the housing for receiving medical fluid under pressure from a source; an inlet fluid flow path in the housing communicating between the inlet port and bladder for introducing medical fluid into the bladder; a fill amplification structure positioned within the bladder expansion space and at least partially surrounding the bladder so as to restrict radial expansion of at least a portion of the bladder as medical fluid is introduced into the bladder.

2. The medical fluid injection device of claim 1 wherein the fill amplification structure includes protrusions formed within the bladder expansion space.

3. The medical fluid injection device of claim 2 wherein the injection device includes an outer wall having an inner surface upon which the protrusions are formed.

4. The medical fluid injection device of claim 3 wherein the protrusions are molded into the inner surface of the outer wall.

5. The medical fluid injection device of claim 2 wherein the protrusions include a plurality of ribs.Docket No.: 8002-0070.01 6. The medical injection device of claim 1 wherein the fill amplification structure includes a rigid insert having a body with a channel formed therein, said channel including an inner diameter configured to engage and restrict the bladder as it radially expands.

7. The medical injection device of claim 6 wherein the bladder expansion space is arcuate shaped, the bladder is arcuately expandable and the rigid insert includes a longitudinally arcuate body.

8. The medical injection device of claim 6 wherein the rigid insert is constructed from plastic.

9. The medical injection device of claim 6 wherein the housing includes structures configured to be engaged by the rigid insert when it is positioned within the bladder expansion space.

10. The medical injection device of claim 9 wherein the structures include ribs and the rigid insert includes recesses configured to receive the ribs when the rigid insert is positioned within the bladder expansion space.

11. The medical injection device of claim 6 wherein the channel includes a first section including a first inner diameter and a second section including a second inner diameter, where the first inner diameter differs from the second inner diameter and the first and second sections are arranged in a step fashion.

12. The medical injection device of claim 6 wherein the fill amplification structure includes multiple rigid inserts.

13. The medical injection device of claim 1 wherein the housing includes a clear window portion through which the fill indicator may be viewed.Docket No.: 8002-0070.01 14. The medical injection device of claim 13 further comprising graduation markings on or beside the window.

15. The medical injection device of claim 14 wherein the graduation markings include an “empty” marker and a “full” marker and the fill amplification structure is configured so that the fill indicator moves from the “empty” marker to the “full” marker as the bladder is filled with a predetermined amount of liquid.

16. The medical injection device of claim 1 wherein the fill amplification structure includes a spring having a distal end portion connected to the fill indicator and a proximal end portion secured to the housing so that the spring expands as the bladder is filled with medical fluid, said spring having coils, where each coil has an inner diameter.

17. The medical injection device of claim 16 wherein the bladder expansion space is arcuate shaped and the bladder is arcuately expandable so that the spring expands in an arcuate fashion as the bladder is filled with medical fluid.

18. The medical injection device of claim 16 wherein the spring is constructed from plastic.

19. The medical injection device of claim 16 wherein the spring is constructed from metal.

20. The medical injection device of claim 165 wherein the housing includes structures configured to be engaged by the coils of the spring when it is positioned within the bladder expansion space.

21. The medical injection device of claim 20 wherein the structures include ribs.Docket No.: 8002-0070.01 22. The medical injection device of claim 16 wherein the spring includes a first coil including a first inner diameter and a second coil including a second inner diameter, where the first inner diameter differs from the second inner diameter.

23. The medical injection device of claim 1 further comprising an injection needle carried by the housing and in fluid communication with outlet port of the housing.

24. A fill amplification structure configured to be inserted into a bladder expansion space of an injection device having a resilient expandable bladder positioned in the bladder expansion space for holding medical fluid, the fill amplification structure configured to at least partially surround the bladder so as to restrict radial expansion of at least a portion of the bladder as medical fluid is introduced into the bladder.

25. The fill amplification structure of claim 24 wherein the fill amplification structure includes a rigid insert having a body with a channel formed therein, said channel including an inner diameter configured to engage and restrict the bladder as it radially expands.

26. The fill amplification structure of claim 25 wherein the rigid insert includes a longitudinally arcuate body.

27. The fill amplification structure of claim 25 wherein the rigid insert is constructed from plastic.

28. The fill amplification structure of claim 25 wherein the rigid insert includes recesses configured to receive structures when the rigid insert is positioned within the bladder expansion space.

29. The fill amplification structure of claim 25 wherein the channel includes a first section including a first inner diameter and a second section including aDocket No.: 8002-0070.01 second inner diameter, where the first inner diameter differs from the second inner diameter and the first and second sections are arranged in a step fashion.

30. The fill amplification structure of claim 24 wherein the fill amplification structure includes a spring having a distal end portion configured to be connected to a fill indicator and a proximal end portion configured to be secured to the housing so that the spring expands as the bladder is filled with medical fluid, said spring having coils, where each coil has an inner diameter.

31. The fill amplification structure of claim 30 wherein the spring is constructed from plastic.

32. The fill amplification structure of claim 30 wherein the spring is constructed from metal.

33. The fill amplification structure of claim 30 wherein the spring includes a first coil including a first inner diameter and a second coil including a second inner diameter, where the first inner diameter differs from the second inner diameter.

34. A method of adjusting sensitivity of a fill indicator to a fill volume of medical fluid in an injection device having a bladder expansion space with a resilient expandable bladder positioned in the bladder expansion space for holding medical fluid, where a fill indicator is attached to a distal potion of the bladder, the method comprising the steps of inserting a fill amplification structure into the bladder expansion space and at least partially surrounding the bladder with the fill amplification structure so as to restrict radial expansion of at least a portion of the bladder as medical fluid is introduced into the bladder.

35. A medical fluid injection device comprising: an injection device housing having a bladder expansion space therein; a resilient expandable bladder positioned within the bladder expansion space;Docket No.: 8002-0070.01 a fill indicator attached to a distal end portion of the bladder; an outlet port in the housing; an injection flow path for flujd communication between the bladder and the outlet port; a fill amplification structure positioned within the bladder expansion space and at least partially surrounding the bladder so as to restrict radial expansion of at least a portion of the bladder by medical fluid in the bladder.

36. The medical fluid injection device of claim 35 wherein the fill amplification structure controls the bladder expansion space so as to be customizable to any bladder fill volume between 3 ml to 10 ml so as to always result in movement of the fill indicator through an angle of 20° to 70°.

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