DOSE DELIVERY MECHANISM WITH SPINNING THROUGH PREVENTION

Abstract

A non-slip dose delivery mechanism includes a housing, a non-rotating piston rod, a nut, a piston rod guide, a driver, a ratchet and a brake. The non-rotating piston rod has a threaded outer surface. The nut includes an inner surface in threaded engagement with the threaded outer surface of the non-rotating piston rod. The nut is configured to rotate and translate axially in a proximal direction relative to the non-rotating piston rod during dose setting. The piston rod guide is rotationally fixed relative to the housing and is configured to prevent rotation of the piston rod. The driver includes an inner surface and an outer surface, the inner surface being in a rotationally fixed engagement with the nut. The ratchet is rotationally fixed to relative to the housing. The brake is positioned between the nut and the ratchet.

Claims

1. A non-slip dose delivery mechanism comprising: a housing; a non-rotating piston rod having a threaded outer surface; a nut comprising an inner surface in threaded engagement with the threaded outer surface of the non-rotating piston rod, the nut configured to rotate and translate axially in a proximal direction relative to the non-rotating piston rod during dose setting; a piston rod guide rotationally fixed relative to the housing and configured to prevent rotation of the piston rod; a driver comprising an inner surface and an outer surface, the inner surface being in a rotationally fixed engagement with the nut; a ratchet rotationally fixed to relative to the housing; and a brake positioned between the nut and the ratchet.

2. The non-slip dose delivery mechanism of claim 1, wherein the piston rod has a non-circular cross-section that is held non-rotational relative to the housing by the piston rod guide rotationally fixed relative to the housing.

3. The non-slip dose delivery mechanism of claim 1, wherein rotation of the nut during dose setting is through a clutch operatively connected to a dose knob configured to be rotated by a user of the dose setting mechanism.

4. The non-slip dose delivery mechanism of claim 3, wherein the nut has one or more flexible arms that releasably engage the ratchet during dose setting and dose cancellation.

5. The non-slip dose delivery mechanism of claim 4, wherein relative movement and engagement of the one or more flexible arms with the ratchet is configured to generate a tactile or audible signal to a user of the non-slip dose delivery mechanism.

6. The non-slip dose delivery mechanism of claim 1, wherein the outer surface of the driver is configured to cause the driver to rotate and move axially during dose delivery.

7. The non-slip dose delivery mechanism of claim 1, wherein axial movement of the driver is configured to push the nut axially in a proximal direction relative to the housing.

8. The non-slip dose delivery mechanism of claim 1, wherein the brake is adjacent a distal terminal end of the driver and adjacent a terminal proximal end of the ratchet.

9. The non-slip dose delivery mechanism of claim 1, wherein the brake is a ring having a through hole to accept a proximal end of the nut.

10. The non-slip dose delivery mechanism of claim 1, wherein the ratchet is fixed to the piston rod guide and is fixed to an inside surface of the housing.

11. An injection device comprising: the non-slip dose delivery mechanism of claim 1: and a holder attached to the non-slip dose delivery mechanism, the holder configured to accept a container of medicament.

12. An anti-slip dose delivery mechanism comprising: a housing; a non-rotating piston rod having a threaded outer surface; a nut comprising an inner surface that is in threaded engagement with the threaded outer surface of the piston rod, the nut configured to rotate and translate axially in a proximal direction relative to the piston rod during dose setting; a piston rod guide rotationally fixed relative to the housing and configured to prevent rotation of the piston rod; a driver comprising an inner surface and an outer surface, the inner surface in a rotationally fixed engagement with the nut; a ratchet rotationally fixed to relative to the housing and comprising an inner surface with a radial lip; and a glider positioned between the driver and the nut, the nut capable of moving from a first position where dose cancellation is prevented to a second position where dose cancellation is operable.

13. The anti-slip dose delivery mechanism of claim 12, wherein the driver has an outer surface configured to cause the driver to rotate and move axially during dose delivery.

14. The anti-slip dose delivery mechanism of claim 12, wherein the nut further comprises a radial flexible arm configured to engage the ratchet when nut is in the first position.

15. An injection device comprising: the anti-slip dose delivery mechanism of claim 12; and a holder attached to the anti-slip dose delivery mechanism, the holder configured to accept a container of medicament.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0024] The invention will be explained in more detail hereinafter with reference to the drawings.

[0025] FIG. 1A illustrates one possible embodiment of a complete injection device containing the structural components of the present disclosure;

[0026] FIG. 1B shows a cross-sectional view of just the distal end or dose delivery mechanism of the injection device of FIG. 1A;

[0027] FIG. 1C shows a cross section view of a portion of the dose delivery mechanism of FIG. 1B;

[0028] FIG. 2A shows perspective views of some of the structural components of one of the possible dose delivery mechanisms of the present disclosure;

[0029] FIG. 2B shows a cross section of the dose delivery components of FIG. 2A;

[0030] FIG. 2C shows a cross section of a portion of the components of FIG. 2B at B-B;

[0031] FIG. 3 shows perspective views of some of the structural components of another embodiment of the dose delivery mechanisms of the present disclosure;

[0032] FIG. 4 shows a cross section of the dose delivery components of FIG. 3 in a first position;

[0033] FIG. 5 shows a cross section of a portion of the components of FIG. 4 at B-B;

[0034] FIG. 6 shows a cross section of the dose delivery components of FIG. 3 in a second position;

[0035] FIG. 7 is a perspective view of a possible nut of the present disclosure the piston rod;

[0036] FIG. 8A is a perspective view of the of one embodiment of a ratchet;

[0037] FIG. 8B is a cross section of the ratchet shown in FIG. 8A; and

[0038] FIG. 8C is a top view of the ratchet shown in 8A.

DETAILED DESCRIPTION

[0039] In the present application, the term “distal part/end” refers to the part/end of the device, or the parts/ends of the components or members thereof, which in accordance with the use of the device, is located the furthest away from a delivery/injection site of a patient. Correspondingly, the term “proximal part/end” refers to the part/end of the device, or the parts/ends of the members thereof, which in accordance with the use of the device is located closest to the delivery/injection site of the patient.

[0040] The dose delivery mechanism of the embodiments of the present disclosure can be used in a number of variously designed complete injection devices. One such embodiment of a complete injection device 100 is illustrated in in FIG. 1, where a dose delivery mechanism 1 is connected to a medicament container holder 2, which holds a medicament container 3, preferably a cartridge. The container holder has a proximal end with a connector 4 configured to accept a medicament delivery conduit, preferably a double ended needle cannula (i.e., a pen needle). The pen needle is attached to the connector 4 through a snap fit, thread, Luer-Lok, or other secure attachment with a hub such that the double ended needle cannula can achieve a fluid communication with medicament contained in the cartridge 3. The cartridge 3 is sealed at the proximal end by septum and with a sliding piston at the opposite distal end. Dose setting are shown in by indicia in the window 7 of a housing 8 of the dose delivery mechanism 1. FIG. 1 shows the delivery device where a protective cap covering the medicament container holder 2 is removed. A dose is set (or cancelled) when a user turns a dose knob 6. A dose is delivered when a user presses dose a button 5 after a dose has been set causing the dose knob 6, a dose dial sleeve 11 (see FIG. 1B), a nut 13, a piston rod 10 and a driver 12 all to move proximally.

[0041] FIG. 1B shows a cross section of one possible embodiment of the dose setting and the dose delivery mechanism 2 of the present disclosure. FIG. 1C is a cross sectional view of the dose delivery mechanism shown in FIG. 1B, where a flexible arm 15 at the proximal end of the nut 13 is shown engaged with a ratchet 14. The piston rod 10 can also have a threaded outer surface 10a and have a non-circular cross section.

[0042] In another possible embodiment, as illustrated in FIG. 2A-2C, there is shown a nut 13 having an outer surface containing longitudinal splines 13b that engage and rotationally lock the nut to a clutch such that rotation of the dose knob causes rotation of the nut 13. The nut 13 also has a threaded inner surface 13a that is threadedly engaged with the threads 10a on the outer surface of the piston rod 10. The driver 12 has an outer thread 12a that cooperates with a threaded inner surface of a piston guide that is rotationally fixed relative to the housing 8. A brake 20 is positioned between the nut 13 and the ratchet 14 to provide a spinning through prevention feature. The driver 12 is rotationally fixed to the dose dial sleeve 11, which rotates during dose setting, dose cancelation and dose delivery. The piston rod guide can have a non-circular through hole that slidably accepts the piston rod and prevents the piston rod from rotating during dose setting and dose delivery. A glider 30 can be positioned between the driver and the ratchet to reduce or eliminate the friction caused by the rotating driver during dose delivery. The ratchet 14 is held non-rotational relative to the housing 8 by the linear guide 16, which can be configured to engage the piston rod guide.

[0043] FIG. 2C shows one example of a flexible arm 15 located on the proximal end of the nut 13 engaged with an inner surface of ratchet 14. This design of the flexible arm 15 has a nib 15a that is configured to releasably engage the splines 14a inside of the ratchet 14 as the nut 13 is rotated in either direction. Although only one flexible arm is shown, multiple flexible arms can be used. The releasable configuration of the nib with the ratchet splines enables the user to conveniently correct a miss-dialed dose by rotating the dose knob in the opposite direction. The nut 13 and the clutch are permanently splined to each other during assembly of the dose delivery mechanism through a splined connection. This splined connection ensures that the clutch and the nut are always rotationally fixed to each other during both dose setting and dose delivery. This splined connection also allows the clutch and the nut to move axially relative to each other. The sliding connection is necessary in order to compensate for pitch differences between the threads 10a on the piston rod 10, the outer threads on the dose sleeve and the thread 12a on the driver 12. Preferably, the thread between driver and piston rod guide has basically the same pitch as the thread between piston rod and nut.

[0044] As shown in FIG. 1B, in addition to the threads 10a on the outer surface of the piston rod 10, there is also included two longitudinal flats 10b that give the piston rod 10 a non-circular cross section. At the terminal proximal end of the piston rod is a connector, shown as a snap fit, that connects with a disc or a foot. At the distal end of the piston rod there can be a last dose feature of the dose setting mechanism configured as an enlarged section of the piston rod designed to stop the rotation of the nut 13 about the threads 10a when the amount of medicament remaining in the cartridge 3 is less than the next highest predetermined dose setting. In other words, if the user tries to set one of the predetermined fixed dose settings that exceeds the amount of medicament remaining in the cartridge, then the enlarged section will act as a hard stop preventing the nut from further rotation along the threads 10a as the user attempts to reach the desired predetermined fixed dose setting.

[0045] In a possible embodiment, a rotational biasing member, for example a torsion spring, can be connected to the driver 12, which is connected and rotationally fixed with the inner surface of the dose sleeve through splines on the distal outer surface of the driver. On the proximal end of driver 12 on the outer surface is threads 12a that are engaged with matching threads on the inner distal surface of the piston rod guide. The thread between the driver and the piston guide has a significantly different pitch than the thread between the dose sleeve and the housing. The nut and the driver rotate together both during dose setting and dose cancellation and, as such, they perform essentially the same axial movement. However, this movement is independent from each other, i.e., the nut is turned by the clutch and performs an axial movement due to the thread to the piston rod, while the driver is rotated by the dose sleeve and performs an axial movement due to the thread to the piston guide. The driver is rotated during injection also, and so it actively moves in the proximal direction during injection. The nut does not rotate during injection and, as such, does not perform an active axial movement. The nut only moved axially in the proximal direction during injection because it is pushed axially by the driver as it rotates. To prevent the rotating driver from inducing a rotational motion of the piston rod (i.e., spinning through) the brake 20 is employed to provide a friction surface to ensure that the piston rod only moves in an axial direction, thus preserving dose accuracy.

[0046] It is preferred that the pitch of the thread on the driver is equal to or be slightly higher than the pitch of the thread on the inside of the nut. And, the thread between the dose sleeve and the housing has a higher pitch than that of the nut and piston rod. This is desirable because it yields a mechanical advantage that makes the dose delivery process easier for the user.

[0047] Another embodiment of a dose delivery mechanism to prevent a spinning through failure mode is illustrated in FIGS. 3-8C, where a free wheel design is employed in combination with a two position nut and ratchet assembly. In this embodiment, the flexible arm 15 and the nib 15a are configured such that the nut can only rotate in one direction when the nib is engaged with the splines on the ratchet 14. This single direction of rotation of the nut 13 occurs during dose setting. The nut cannot be rotated during dose delivery so there is no issue regarding the failure mode of spinning through. However, such a design has the negative feature that dose cancelation is not possible. To enable dose cancellation this embodiment utilizes a two-position relationship between the nut and the ratchet. FIGS. 4 & 5 show the nut 13 in the first position. FIG. 6 shows the nut in a second position where the flexible arm 15 and the nib 15a are no longer engaged with the splines 14a inside the ratchet 14. During normal dose setting operation the ratchet and nut are in the relative axial position shown in FIG. 4. In this position the flexible arm of the nut interacts with the splines of the ratchet. The linear guide between the ratchet and the piston rod guide limits the linear movement of the ratchet. The distal end position of the ratchet is reached earlier than the distal end position of the nut and the driver. If the user turns the dose knob beyond that distal end position of the ratchet, the ratchet and nut are pulled apart, so that they switch from the first position (FIG. 4) to the second position (FIG. 6). In the second position the flexible arm of the nut is not in contact to the splines of the ratchet and the user can turn the dose knob back to zero if the user has inadvertently dialled a dose larger than intended or wants to merely cancel a set dose. In the zero position the nut is pushed back into the ratchet, so that the components switch from second position back to the first position causing the flexible arm of the nut to again engage and interfere with the splines of the ratchet.

[0048] A positioning protrusion 27 located on the nut and a radial lip 25 located on the ratchet are operatively engaged to keep the nut in either the first or the second positions. This is evident by a comparison of FIGS. 4 and 6. FIG. 7 shows the positioning protrusion 27 on nut 13 relative to the flexible arm 15. FIGS. 8A-8C show the radial lip 25 on the inside surface of the ratchet 14 and positioned relative to the splines 14a. A glider 30 can be positioned between the driver 12 and nut 13.

[0049] It is to be understood that the embodiments described above and shown in the drawings are to be regarded only as non-limiting examples of the possible designs of the safety assembly and such designs can be modified in many ways within the scope of the patent claims.