DELAY DEVICE FOR A MEDICAL ADMINISTRATION APPLIANCE

Abstract

A piston rod unit for a device for administering a medical substance delays a release of a mechanism of the device and includes an outer piston rod with a hollow space and a contact face for interacting with a stopper to discharge the substance, and an inner piston rod mounted in the outer piston rod to form a cavity at the distal end of the outer piston rod. The cavity contains a viscous fluid and a fluid displacement element located at least partially in the cavity that is operably or integrally connected to the inner piston rod. During relative movement between the fluid displacement element and the outer piston rod, fluid displacement causes movement resistance, such that mechanism release is delayed. The outer piston rod includes a distal, first piston rod part, comprising the contact face and the cavity, and a second piston rod part adjoining the first.

Claims

1. A plunger rod unit for an administration appliance for administering a medical substance, wherein the plunger rod unit delays a release of a mechanism of the administration appliance, the plunger rod unit comprising: a. an outer plunger rod with a contact face on a distal end of the outer plunger rod for interacting with a stopper, in order to discharge the substance from a product container, b. an inner plunger rod mounted in the outer plunger rod in such a way that a cavity is formed at the distal end of the outer plunger rod, said cavity being at least partially filled with a viscous fluid, c. a fluid displacement element that is located at least partially in the cavity and that is operably or integrally connected to the inner plunger rod and wherein the fluid displacement element is moved relative to the outer plunger rod in a delay movement, d. wherein, in a relative movement between the fluid displacement element and the outer plunger rod by displacement of the fluid, a movement resistance is generated, so that the fluid displacement element is delayed in reaching a release position that releases the mechanism of the administration appliance, and e. wherein the outer plunger rod comprises a distal first plunger rod part that comprises the contact face and forms the cavity for the fluid displacement element, and a second plunger rod part adjoining the first plunger rod part.

2. The plunger rod unit according to claim 1, wherein the inner plunger rod is axially fixed relative to the outer plunger rod in the longitudinal direction of the plunger rod unit.

3. The plunger rod unit according to claim 1, wherein the outer plunger rod is configured such that at least half of the length of the inner plunger rod is accommodated in the outer plunger rod.

4. The plunger rod unit according to claim 1, wherein in the delay movement, the fluid displacement element rotates about a longitudinal axis of the outer plunger rod relative to the outer plunger rod.

5. The plunger rod unit according to claim 4, wherein the fluid displacement element rotates by an angle of at least 60 relative to the outer plunger rod.

6. The plunger rod unit according to claim 1, wherein the fluid displacement element comprises a pin for transmitting axial forces and for centering the fluid displacement element in the cavity.

7. The plunger rod unit according to claim 1, wherein the fluid displacement element comprises at least two wings for displacing the fluid in the cavity.

8. The plunger rod unit according to claim 7, wherein the cavity has a first chamber for accommodating a first wing of the at least two wings and a second chamber for accommodating the second wing of the at least two wings.

9. The plunger rod unit according to claim 1, wherein the fluid has a kinematic viscosity between 100,000 and 500,000 centistokes.

10. The plunger rod unit according to claim 1, wherein the fluid displacement element is configured with a gap between the fluid displacement element and an inner surface of the first plunger rod part so that, in the relative movement between fluid displacement element and outer plunger rod, the fluid flows through the gap.

11. The plunger rod unit according to claim 1, wherein the cavity is configured so that the fluid remains in the cavity during the relative movement between the fluid displacement element and outer plunger rod.

12. The plunger rod unit according to claim 1, wherein the first plunger rod part and the second plunger rod part have different physical properties.

13. The plunger rod unit according to claim 1, wherein the delayed release of a mechanism of the administration appliance is a release of one or more of a signal generation mechanism, a retraction mechanism for retracting a needle or cannula, or a mechanism that enables a function of the administration appliance performed at an end of an administration.

14. The plunger rod unit according to claim 1, wherein the first plunger part is fluidically sealed by a sealing means cooperating with the fluid displacement element.

15. An administration appliance for administering a medical substance, comprising a signal generation mechanism for generating a signal, and a plunger rod unit according to claim 1, wherein, at the end of an administration process, the plunger rod unit delays generation of a signal by the signal generation mechanism.

16. An administration appliance for administering a medical substance, comprising a housing, an insertion mechanism arranged in the housing for inserting a needle or a cannula, a retraction mechanism for retracting the needle or cannula into the housing or into a drug container, and a plunger rod unit according to claim 1, wherein at the end of an administration process, the plunger rod unit delays retraction of the needle or cannula with the retraction mechanism.

17. A method for producing a plunger rod unit for an administration appliance for administrating a medical substance, comprising the steps of a. providing a two-part outer plunger rod with a distal first plunger rod part that comprises a cavity and with a second plunger rod part configured as a sleeve; b. filling a viscous fluid into the cavity; c. introducing a fluid displacement element into the cavity, so that at least a portion of the fluid displacement element is immersed in the viscous fluid, and mounting a sealing element between the fluid displacement element and an inner wall in the cavity, so that the cavity is fluidically sealed; d. connecting the first plunger rod part to the second plunger rod part, so that the first plunger rod part cannot move relative to the second plunger rod part rotatably or longitudinally, and wherein the fluid displacement element is located within the first plunger rod part, or within the second plunger rod part, or within both.

18. The method according to claim 17, wherein the step of filling of the fluid into the cavity occurs under vacuum or negative pressure.

19. The method according to claim 17, wherein the fluid displacement element comprises a pin for transmitting axial forces and further comprising centering the fluid displacement element in the cavity using the pin.

20. The method according to claim 17, further comprising performing a step of cleaning or testing the plunger rod unit after performing the steps a.-d. and separately from its further assembly into the administration appliance.

Description

FIGURES

[0064] FIG. 1 shows an administration appliance with a plunger rod unit according to the invention in a section view, wherein the section extends through the longitudinal axis of the administration appliance;

[0065] FIG. 2 shows an enlargement of the section view from FIG. 1 in a distal region of the plunger rod unit;

[0066] FIG. 3 shows an exploded view of the plunger rod unit; and

[0067] FIG. 4 shows a perspective view of the first plunger rod part of the plunger rod unit.

DESCRIPTION

[0068] FIG. 1 shows a section view of an administration appliance designed in the form of an autoinjector 1. The section here extends along a central longitudinal axis L of the autoinjector 1.

[0069] The autoinjector 1 comprises a sleeve-shaped longitudinal housing 2 with the longitudinal axis L. In this housing 2, a product container 3 with the liquid medical substance, a product container holder referred to as syringe holder 4, a plunger rod unit 10 with an outer plunger rod 30 and with an inner plunger rod 20, and a drive unit 6 are arranged. On a distal end of the autoinjector 1, said autoinjector comprises in its delivery state a pull-off cap 5a that has to be removed before the use of the autoinjector 1.

[0070] Below, the most important components of the autoinjector 1 are briefly described. A detailed description of the autoinjector is disclosed in the patent application WO 2016/205962 A1 (incorporated by this reference). In contrast to the present invention, the autoinjector described in WO 2016/205962 A1 comprises no plunger rod unit 10 with a two-part outer plunger rod, but has instead an integrally connected outer plunger rod.

[0071] The drive unit 6 of the autoinjector 1 comprises a coil spring 7 which, in the delivery state of the autoinjector 1, is pretensioned with sufficient energy to be able to discharge the medical substance contained in the product container 3 by shifting a stopper 3a out of the product container by means of a discharge stroke. The drive unit 6 moreover comprises a threaded rod 9 oriented in the longitudinal direction L, which is in threaded engagement with the inner plunger rod 20 of the plunger rod unit 10. The inner plunger rod 20 is secured in the longitudinal direction relative to the outer plunger rod 30, so that, in the case of a rotation of the threaded rod 9, the inner plunger rod 20 and the outer plunger rod 30 move in the longitudinal direction toward the distal end relative to the housing 2. The outer plunger rod 30 includes a distal first plunger rod part 30a and a sleeve-shaped second plunger rod part 30b proximally adjoining the first plunger rod part 30a. The first plunger rod part 30a and the second plunger rod part 30b are connected to one another in such a way that they cannot be moved relative to one another in the rotational and longitudinal directions.

[0072] The first plunger rod part 30a comprises on its distal end a contact face 35. With said contact face, the first plunger rod part 30a interacts with a stopper 3a of the product container 3 in order to discharge the medical substance from the product container 3. The syringe holder 1 cannot be moved relative to the housing and is engaged with said housing. The product container 3 is arranged relative to the housing 2 in such a way that the needle tip of an insertion needle 5 protrudes distally over the distal end of the housing 2 but is covered before and after the injection by a needle protection sleeve. On its proximal end, the housing 2 comprises a closure cap 8, which is connected by positive-locking connection to the housing 2 in a rotationally and axially fixed manner and which forms the proximal end of the autoinjector 1.

[0073] For the discharge of the medical substance from the product container, the drive unit 6 drives the threaded rod that is in threaded connection with the inner plunger rod 20. Thereby, an axial movement is generated, resulting in the plunger rod unit 10 being able to shift the stopper in the carpoule in the axial direction. The axial forces occurring in the process are transmitted by the inner plunger rod 20 to the fluid displacement element 14. Via the centering tip (pin) 19 of the fluid displacement element 14, the axial forces are further transmitted to the first plunger rod part 30a, which transmits the forces via its contact face 35 to the stopper 3a.

[0074] Below, the plunger rod unit 10 according to the invention is explained in detail. FIG. 3 shows an exploded view of the plunger rod unit 10 according to the disclosure. It comprises the two-part outer plunger rod 30, the inner plunger rod 20, a fluid displacement element 14 connected to the inner plunger rod 20, and an O-ring 25 that is arranged between the fluid displacement element 14 and the inner plunger rod 20.

[0075] As mentioned above, the outer plunger rod 30 comprises a distal first plunger rod part 30a and a second plunger rod part 30b proximally adjoining the first plunger rod part 30a. The first plunger rod part 30a essentially has a cylindrical shape and comprises a cavity.

[0076] FIG. 4 shows an enlarged perspective view of the first plunger rod part 30a. In this enlarged representation, one can see that two chambers 37a, 37b are formed in the cavity. The chambers 37a, 37b each occupy a partial volume of a cylinder and they each have a cross section and a footprint in the shape of a circle segment.

[0077] The second plunger rod part 30b is designed to be in the shape of a sleeve and essentially has the same outer diameter as the first plunger rod part 30a. The second plunger rod part 30b is non-rotatably mounted, guided longitudinally, in a mechanism holder 40. For this purpose, on an outer surface of the second plunger rod part 30b, multiple guiding elements 33 are arranged that are designed to be longitudinal and oriented in the longitudinal direction and that extend over almost the entire length of the second plunger rod part 30b. Complementary thereto, on an inner surface of the mechanism holder 40, longitudinal guides are arranged, into which the guiding elements 33 engage. The mechanism holder 40 cannot be shifted relative to the housing 2 along the longitudinal axis L and is arranged in a rotationally fixed manner.

[0078] As one can see in FIGS. 1 and 2, the inner plunger rod 20 is mounted in the second plunger rod part 30b of the outer plunger rod 30. The inner plunger rod 20 is designed to be in the shape of a sleeve and has a slightly thickened proximal end compared to the rest of the sleeve body. Said proximal end has approximately the same diameter as the outer plunger rod 30 and is arranged outside of the outer plunger rod 30. Due to the thickened end, an annular structure 21 is formed on the proximal end of the inner plunger rod 20. This structure 21 is interrupted by two grooves 22. The grooves 22 have two functions. The first function is to ensure the rotation lock between the inner plunger rod 20 and the mechanism holder 40, and the second function is the release of engagement elements 41a, 41b after completion of the product discharge. On its distal end, the inner plunger rod 20 comprises two mutually facing recesses 23a, 23b. A cam 17a, 17b of the fluid displacement element 14 engages in each of these recesses 23a, 23b, so that the fluid displacement element 14 is connected in a rotationally fixed manner to the inner plunger rod 20.

[0079] In a proximal region, the fluid displacement element 14 comprises a cylindrical section that protrudes into the inner space of the inner plunger rod 20, as can be seen in FIG. 2. In this section of the fluid displacement element 14, the two cams 17a, 17b are arranged. Between the cams 17a, 17b, a peripheral collar 18 extends, which, in the assembled state, engages by positive-locking connection in a corresponding depression in the inner space of the inner plunger rod 20. The fluid displacement element 14 is thereby held in the longitudinal direction by a positive-locking connection in the inner plunger rod 20. Between this cylindrical section and a distal region, the fluid displacement element 14 comprises a central region with a peripheral groove 16. In this groove 16, an O-ring 25 is accommodated. The distal region of the fluid displacement element 14 comprises two wings 15a, 15b that radially protrude in the form of two rectangular elements, as can be seen in FIG. 3. On its distal end, the fluid displacement element 14 comprises a cylindrical centering tip (pin) 19 on the longitudinal axis L. This centering tip 19 supports the fluid displacement element 14 in the radial direction and thus ensures that, even under exposure to radial forces, the fluid displacement element 14 is always oriented on the longitudinal axis L.

[0080] In the assembled state, the distal and the central regions of the fluid displacement element 14 are located within the cavity of the first plunger rod part 30a of the outer plunger rod 30, while the proximal region (cylindrical section) of the fluid displacement element 14 is accommodated in the inner plunger rod 20. This arrangement can be seen best in the enlarged view in FIG. 2. There, it can be seen that the O-ring 25 in the groove 16 seals the cavity. The two wings 15a, 15b of the fluid displacement element 14 are each located in one of the chambers 37a, 37b of the first plunger rod part 30a. Due to the shape of the chambers 37a, 37b, the fluid displacement element 14 can rotate the wings 15a, 15b through an angle of at least 90 relative to the first plunger rod part 30a. In an embodiment, the fluid displacement element 14 can rotate by an angle of 110 relative to the first plunger rod part 30a. The chambers 37a, 37b are almost completely filled with a viscous fluid, in particular with an oily, viscous, gel-like or pasty liquid. Preferably, a silicone liquid having a kinematic viscosity between 100,000 and 500,000 centistokes is used. The first plunger rod part 30a has two arms 36a, 36b projecting in the longitudinal direction and engaging in corresponding recesses 34a, 34b in the second plunger rod part 30b. The first plunger rod part 30a is as a result secured in a rotationally fixed manner with respect to the second plunger rod part 30b. Furthermore, on their ends, the arms 36a, 36b each comprise a radially inward pointing cam 38a, 38b, each engaging behind a shoulder on the fluid displacement element 14, so that the first plunger rod part 30a cannot be moved in the longitudinal direction relative to the second plunger rod part 30b. Thus, the first and the second plunger rod parts 30a, 30b are held in such a manner that they cannot be moved relative to one another in the rotation direction and in the longitudinal direction.

[0081] On the other hand, the inner plunger rod 20 together with the fluid displacement element 14 can rotate relative to the outer plunger rod 30 (and thus relative to the first plunger rod part 30a and the second plunger rod part 30b) when the inner plunger rod 20 is released from the mechanism holder 40, as explained below.

[0082] At the beginning and during the discharge of the product from the product container, a rotation lock exists between outer plunger rod 30, inner plunger rod 20, and mechanism holder 40. At the end of a discharge, when the inner plunger rod 20 is shifted from proximal by approximately the discharge stroke toward distal, the rotation lock of the inner plunger rod 20 is released, because in this state the grooves 22 are no longer guided by ribs of the mechanism holder 40. A torque introduced by the drive unit 6 via the threaded rod 9 then induces a rotation of the inner plunger rod 20 relative to the mechanism holder 40 and the outer plunger rod 30. Because the fluid displacement element 14 is connected in a rotationally fixed manner to the inner plunger rod 20, in this state the fluid displacement element 14 rotates with the inner plunger rod 20. The resistance generated by the viscous fluid opposes the rotation. This resistance delays the rotation of the inner plunger rod 20 without, however, preventing it, since, during a rotation of the fluid displacement element 14, the fluid can flow in a gap between a radial outer surface of the wings 15a, 15b and an inner surface of the chamber from one side of the wings 15a, 15b to the other side.

[0083] During the rotation of the inner plunger rod 20, an axial force exerted by the threaded rod 9 on the plunger rod unit 10 continues to be applied and ensures that the stopper of the product container 3 is fully pressed against a distal abutment in the product container 3 during the rotation.

[0084] If the inner plunger rod 20 has rotated far enough so that the grooves 22 have the same orientation as the engagement elements 41a, 41b, a holding element is released for an axial movement in the proximal direction. The pretensioned holding element as a result springs in the proximal direction up to an abutment and generates a click sound that indicates the end of the injection process to the user.

[0085] The properties of the plunger rod unit can be influenced by the shape of the cavity, the properties of the fluid as well as by additional elements such as wing-like, rudder-like or dough-hook-like structures on inner surfaces of the fluid displacement element and by an inner or outer plunger rod.

LIST OF REFERENCE NUMERALS

[0086] 1 Autoinjector [0087] 2 Housing [0088] 3 Product container [0089] 3a Stopper [0090] 4 Syringe holder [0091] 5 Needle [0092] 5a Pull-off cap [0093] 6 Drive unit [0094] 7 Spring [0095] 8 Closure cap [0096] 9 Threaded rod [0097] 10 Plunger rod unit [0098] 14 Fluid displacement element [0099] 15a, 15b Wing [0100] 16 Groove [0101] 17a, 17b Cam [0102] 18 Collar [0103] 19 Centering tip [0104] 20 Inner plunger rod [0105] 21 Structure [0106] 22 Groove [0107] 23a, 23b Recesses [0108] 25 Sealing element [0109] 30 Outer plunger rod [0110] 30a First plunger rod part [0111] 30b Second plunger rod part [0112] 33 Guiding elements [0113] 34a, 34b Recesses [0114] 35 Contact face [0115] 36a, 36b Arms [0116] 37a, 37b Chambers [0117] 38a, 38b Cams [0118] 40 Mechanism holder [0119] 41a, 41b Engagement elements