Staged telescopic screw assembly having different visual indicators

A telescopic screw assembly for an injector includes an inner screw, an outer screw and a middle screw. The middle and outer screws are in a first threaded engagement, and the inner and middle screws are in a second threaded engagement. The inner screw is nested with the middle screw and the middle screw is nested with the outer screw in a contracted configuration of the screw assembly. Rotation of the outer screw in one direction advances the middle screw relative to the outer screw via the first threaded engagement and advances the inner screw relative to the middle screw via the second threaded engagement to telescopically extend the screw assembly into an expanded configuration. At least two of the inner, middle and outer screws are identified with a different visual indicator to enhance visual distinction between the screws, and readily visually indicate an extension progress of the screw assembly.

BACKGROUND OF THE INVENTION

The present invention relates generally to a telescopic screw assembly and more particularly to an injector having a staged telescopic screw assembly with a visual indicator showing the degree of extension of the telescopic screw assembly.

Injectors or syringes are used to deliver specified quantities of drugs or medicine to a patient and typically include a chamber for storing the drug, a needle connected to the chamber through which the drug is delivered, and a plunger which pushes the medicine from the chamber through the needle. One device for pushing the drug through the chamber is a manually activated plunger. The user typically holds the syringe between two fingers and activates or pushes the plunger with a thumb. One drawback of a manually activated plunger is that patients must be relatively dexterous and have the required hand strength to push the plunger themselves. Another apparatus for pushing the plunger through the chamber is a telescopic assembly. A telescopic assembly is generally contained within the syringe and contains a plurality of nested members which expand to push the plunger through the chamber. One drawback of a telescopic assembly is that it can be difficult to tell whether the assembly has properly achieved its maximum extension. Thus, a user may not know whether a full dose of the drug has been administered. Another drawback of the telescopic assembly is that the assembly may extend all at once, or certain of the nested members may extend in a random sequential order.

The present invention addresses the challenges associated with effectively delivering the drug from the chamber through the needle. For example, it is desirable to provide a delivery system that can move the plunger in stages according to a delivery profile based on the drug viscosity, delivery time, and rate of delivery. Furthermore, it is desirable to provide a delivery system that provides a visual indicator to a patient or clinician when a full dose has been administered by an injector.

BRIEF SUMMARY OF THE INVENTION

Briefly stated, one aspect of the present invention is directed to a telescopic screw assembly for an injector comprising an inner screw, an outer screw and a middle screw. The middle screw and the outer screw are in a first threaded engagement, and the inner screw and the middle screw are in a second threaded engagement. The inner screw is nested with the middle screw and the middle screw is nested with the outer screw in a contracted configuration of the screw assembly. Rotation of the outer screw in one rotational direction advances the middle screw relative to the outer screw via the first threaded engagement and advances the inner screw relative to the middle screw via the second threaded engagement to telescopically extend the screw assembly into an expanded configuration. At least two of the inner, middle and outer screws are identified with a different visual indicator to enhance visual distinction between the inner, middle and outer screws, and readily visually indicate an extension progress of the screw assembly. A first rod member is in movable engagement with an inner channel of the inner screw during movement of the screw assembly between the contracted and expanded configurations. A distal end of the first rod member is larger than a proximal end of the inner screw, thereby preventing retraction from the inner screw. A second rod member is in movable engagement with an inner channel of the first rod member during movement of the screw assembly between the contracted and expanded configurations. A distal end of the second rod member is larger than a proximal end of the first rod member, thereby preventing retraction from the first rod member, and a proximal end of the second rod member is fixed to the injector to prevent movement of the second rod member to thereby prevent overextension of the screw assembly.

Briefly stated, another aspect of the present invention is directed to a telescopic screw assembly for an injector comprising an inner screw and an outer screw. The inner screw and the outer screw are in a threaded engagement, and the inner screw is radially nested with the outer screw in a contracted configuration of the screw assembly. Rotation of the outer screw in one rotational direction advances the inner screw relative to the outer screw via the threaded engagement to telescopically extend the screw assembly into an expanded configuration. At least one of the inner and outer screws is identified with a different visual indicator to enhance visual distinction between the inner and outer screws and readily visually indicate an extension progress of the screw assembly. A rod member is in movable engagement with an inner channel of the inner screw during movement of the screw assembly between the contracted and expanded configurations. A distal end of the rod member is larger than a proximal end of the inner channel of the inner screw, and a proximal end of the rod member is fixed to the injector to prevent movement of the rod member to thereby prevent overextension of the screw assembly.

DETAILED DESCRIPTION OF THE INVENTION

Certain terminology is used in the following description for convenience only and is not limiting. The words “right,” “left,” “lower,” and “upper” designate directions in the drawings to which reference is made. The words “inwardly” or “distally” and “outwardly” or “proximally” refer to directions toward and away from, respectively, the geometric center or orientation of the telescopic screw assembly and related parts thereof. Unless specifically set forth herein, the terms “a”, “an” and “the” are not limited to one element but instead should be read as meaning “at least one”. The terminology includes the above-listed words, derivatives thereof and words of similar import.

Referring toFIGS. 1-5, the present application is directed to a telescopic screw assembly in accordance with one embodiment of the present invention, generally designated with reference numeral10.FIG. 1is a sectional view of the screw assembly10in a contracted configuration which includes an outer screw16, a middle screw14, and an inner screw12nested inside of one another to allow the screw assembly to telescopically expand to an extended configuration (FIG. 3). The screw assembly10can be inserted into an injector100or syringe (not shown) to allow the screw assembly10to push medicine out of a needle130connected to the syringe. One example of an injector contemplated for use with the current invention is disclosed in U.S. Pat. No. 8,157,769, the disclosure of which is hereby incorporated by reference as if fully set forth herein. Each of the outer screw16, middle screw14, and inner screw12is color coded to allow a user or clinician to observe whether full extension was achieved by the screw assembly10to administer a full dose of medicine as explained in greater detail below. Furthermore, the first threaded engagement between the outer screw16and middle screw14, and the second threaded engagement between the middle screw14and inner screw12have different thread pitches to ensure that the screw assembly10extends in a desired sequential order as also explained in greater detail below.

The outer screw16includes a body19having a generally cylindrical outer shape to fit within an injector100having a cylindrical internal cavity (not shown). The outer screw16is rotatable with respect to the injector100. A neck21extends upwardly from the body19and serves as a transition between the body19, which has a smaller diameter than the neck21, and a head23, which has a larger diameter than the neck21. The neck21has a shape to minimize any stress concentrations that may be present in the outer screw16. An upper wall29extends upwardly from the neck21and abuts the head23. The upper wall29has a generally cylindrical shape with a diameter sized to maintain the position of the screw assembly10within the injector100.

The head23includes a gear25which is oriented to rotate about an axis30extending between a proximal end18and a distal end20of the screw assembly10. The gear25is adapted to engage an element of the injector100or syringe (element not shown, but could be a thumb wheel, a gear attached to a motor or similar driving mechanism, etc.) to rotate the gear25, and thus, the outer screw16. As should be understood by one of ordinary skill in the art, any suitable type of gear could be adopted (e.g. spur gear, helical gear, bevel gear). The proximal end18of the head23has a proximal portion32which extends upwardly and radially inwardly from the gear25. The outer surface34of the proximal portion32has a frustoconical shape, while the inner surface36of the proximal portion32is an annular wall38extending upwardly from a shoulder40and defines a recess within the proximal portion32above the shoulder40.

Although the outer screw16is shown with the body19, neck21, and head23all formed as a monolithic element, the body19, neck21, or head23could each be formed as a separate element and connected to the other elements of the outer screw16by traditional fastening methods (e.g. welding, adhesive, screws, or the like). Furthermore, the outer screw16(as well as any other elements of the screw assembly10) can be manufactured from plastic, polymers, stainless steel, etc. by traditional methods (e.g. molding, additive manufacturing, machining, or the like). An opening17extends through the outer screw16from the proximal end18to the distal end20. As should be understood by one of ordinary skill in the art, the opening17need not extend completely through the proximal end18of the outer screw16. However, an opening17which does extend through the proximal end18facilitates easier loading of the middle screw14into the opening17. The opening17is sized to receive an inner screw12and a middle screw14. Alternatively, the screw assembly10can omit a middle screw14or include more than one middle screw14. An outer screw inner thread22is formed along at least a portion of the opening17, and preferably, along a majority of the opening17. The outer screw inner thread22can have any desired thread pitch provided that it mates with a middle screw outer thread24. A protrusion42is formed at the distal end20of the inner thread22and extends generally perpendicularly away and radially inwardly from the outer screw16and into the opening17to prevent movement of the middle screw14distally beyond the protrusion42.

The middle screw14has a generally cylindrical, tubular shape designed to fit within the opening17with a length equal to or at least slightly less than that of the outer screw16such that the middle screw14fits completely within the opening17when the screw assembly10is in the contracted configuration best seen inFIG. 1. The middle screw14includes an unthreaded portion48which has an outer diameter less than the diameter of the outer screw inner thread22and less than the inner diameter of the protrusion42to allow the unthreaded portion48to move within the opening17and beyond the protrusion42. A middle screw outer thread24is formed on the proximal end18of the middle screw14which includes threads having a pitch which meshes with the outer screw inner thread22such that rotation of the outer screw16relative to the middle screw14advances the middle screw14(distally or downwardly when viewingFIGS. 1-4) along the axis30. Of course, the middle screw outer thread24could be formed anywhere along the middle screw12if desired. However, the distance the outer thread24extends toward the distal end20of the middle screw14limits the travel distance of the middle screw14because of the interference between the protrusion42and the outer thread24as the middle screw14moves distally within the opening17.

A cylindrical passageway50extends through the middle screw14from the proximal end18to the distal end20with a middle screw inner thread26formed thereon. The pitch of the middle screw outer thread24is preferably different from, but can be the same as, the pitch of the middle screw inner thread26. More preferably, the pitch of the outer thread24is smaller than the pitch of the inner thread26. The passageway50includes a radially inwardly extending projection52at the distal end of the passageway50as shown inFIGS. 1 and 4to prevent movement of the inner screw12when the inner screw outer thread28contacts the projection52. Alternatively, the projection52can be positioned anywhere along the passageway50. The distal end of the middle screw14has a chamfer54which facilitates insertion of the middle screw14into the opening17of the outer screw16from the proximal end18. The middle screw14has an outer diameter sized to prevent a cap46on the distal end of the inner screw12from entering the passageway50.

The inner screw12has a generally cylindrical, tubular shape and is positionable within the passageway50. The inner screw12includes an unthreaded portion56which has a smaller diameter than the inner screw outer thread28and is sized to rotate within the passageway50to move along the axis30and through the opening defined by the projection52. An inner screw outer thread28is formed adjacent the proximal end of the inner screw12and engages the middle screw inner thread26. The threaded engagement between the inner screw outer thread28and middle screw inner thread26causes movement of the inner screw12along the axis30as the middle screw14is rotated relative to the inner screw12.

As should be understood by one of ordinary skill in the art, the difference in thread pitches of the middle screw outer thread24and the middle screw inner thread26ensures that as a rotational force is applied to the gear25, the middle screw14advances distally along the axis30before the inner screw12moves, as best seen inFIG. 2. As the rotational force continues to be applied to the gear25, the inner screw12only begins to move once the middle screw outer thread22contacts the protrusion42and the middle screw14can no longer advance. After this contact, the middle screw14begins to rotate as the rotational force continues to be applied to the gear25and causes the inner screw12to extend distally, as best seen inFIGS. 3-4. Of course, the pitch of the middle screw outer thread24can be relatively large, provided that the pitch of the middle screw inner thread26is larger. As should be understood by one of ordinary skill in the art, the size of the pitch on either thread24,26can influence the delivery profile and can be based on drug viscosity, delivery time, rate of delivery of the drug, and other factors. Alternatively, the pitch of the threads24,26could be changed to ensure that the inner screw12moves first, that the inner screw12and middle screw14extend simultaneously, that both extend simultaneously but one extends faster than the other, etc. One advantage of controlling the stages of delivery is it ensures that the screw assembly10provides its strongest extension force for the greatest amount of time.

A generally cylindrical channel60extends through the inner screw12and is sized to receive a first member64. The channel60has a generally smooth surface to allow the first member64to slide along the length of the channel60. The proximal portion66of the channel60defines a narrower opening than the rest of the channel60to prevent the first member64from exiting the channel60. A pocket62is formed in the distal portion58of the channel60to secure the cap46to the inner screw12. The pocket62can be a continuous pocket which extends completely around the internal surface of the channel60, or can be one or more individual pockets which extend only partially around the channel60to receive individually formed protrusions on the cap46. Alternatively, the inner screw12could be formed without the pocket62and a press-fit, screw, weld, etc. could be used to couple the cap46to the inner screw12. In yet another alternative, the cap46and inner screw12could be formed as a monolithic element, thus avoiding the need for any coupling element between the two.

The cap46has a cylindrical base68with a collar70extending radially away from the base68. The collar70is generally cylindrical and has a larger outer diameter than the diameter of the middle screw passageway50to prevent the collar70from entering the passageway50by contacting the distal end of the middle screw14. Of course, the base68could have a wide enough diameter that the collar70can be omitted. A stem72extends upwardly from the base68and is sized to extend into the channel60. The length of the stem72, as measured along the axis30, is such that a flange74aligns with the pocket62. The flange74extends outwardly from the stem72and is configured to be positioned in the pocket62to secure the cap46to the inner screw12. A threaded tail76extends downwardly from the base68and is configured to engage a plunger110which can push medicine through a chamber120of the injector100as the telescopic screw assembly10moves form the contracted configuration (FIG. 1) through the partially extended configuration (FIG. 2) to the fully extended configuration (FIGS. 3-4).

The first member64has a generally cylindrical, tubular structure with a length preferably shorter than the inner screw12such that the first member64remains within the channel60when the screw assembly10is in the contracted configuration shown inFIG. 1. The first member64has an outer diameter sized to allow movement within the channel60, and can include an outwardly extending flare (not shown) on the distal end80which contacts a reduced diameter segment (not shown) on the proximal end of the inner screw12to prevent the first member64from exiting the channel60as the screw assembly10moves between the contracted configuration shown inFIG. 1to the extended configuration shown inFIGS. 3-4. The first member64includes a generally cylindrical passageway84sized to receive a second member86. The passageway84includes the narrow proximal portion66which slides along the second member86but is prevented from going past a flared portion88of the second member86as best seen inFIG. 4.

The second member86is a generally cylindrical rod positioned within the passageway84. The proximal end90of the second member86can be fixed by a snap fit, set screw, etc. to the injector100to prevent movement of the second member86. One advantage of fixing the second member86to the injector100is to prevent overextension of the screw assembly10via the various interference fits between the elements of the assembly10.

The outer screw16, middle screw14, and inner screw12can each include a visual indicator to allow a clinician to observe the progress of the administering of the drug and whether the screw assembly10achieved full extension when administering a dose via the injector100. In one embodiment, for example, without limitation, the outer screw16is gray, the middle screw14is yellow, and the inner screw12is green, and all are readily observable through a transparent, translucent, or open window102of the injector100. As should be understood by one of ordinary skill in the art, the colors selected for the screws12,14,16can be any desired color scheme suitable to permit visual distinction between the outer, middle, and inner screws16,14,12. Alternatively, stripes, dots, hatching, etc. could be used to distinguish the screws12,14,16from one another instead of a solid color. One advantage of such an indicator is that a patient can observe whether the injection is complete or if continued application of the injector to the injection site is required. Furthermore, such an indicator allows a clinician or failure investigation team to determine is a drug was used as prescribed or intended.

In use, a user places a cartridge or chamber120containing the drug in the injector100and may input information regarding the drug into the injector100to allow the injector100to determine maximum flow rate, viscosity, etc. from which the injector100can calculate the optimal expansion rate and torque to apply to the screw assembly10. The user then activates the screw assembly10by pressing a button, activating a thumb wheel, voice command etc. (not shown). The outer screw16begins to turn when a rotational force is applied to the gear25. As the outer screw16rotates, the middle screw14is moved from the contracted configuration (FIG. 1) to the partially expanded configuration (FIG. 2). Once the middle screw outer thread24contacts the protrusion42the middle screw14can no longer move distally. The middle screw14then begins to rotate as the rotational force continues to be applied to the gear25. As the middle screw14rotates, the inner screw12moves from the contracted configuration within the middle screw14(FIG. 2) to the fully expanded configuration (FIGS. 3-4). A plunger110connected to the cap46pushes through the chamber120to transfer the drug out of the chamber120via the needle130connected to the chamber120as the middle screw14and inner screw12move distally. The user receives visual indication regarding the degree of expansion of the screw assembly10from the visual indicators (e.g. colors) of the inner, middle, and outer screws12,14,16. Once the drug delivery is complete, an opposite rotational force can be applied to the gear25to return the screw assembly10to the contracted configuration.