Patent Description:
Syringe assemblies, and in particular hypodermic syringes, are well known in the medical field for dispensing fluids, such as medications. A conventional syringe typically includes a syringe barrel with an opening at one end and a plunger mechanism disposed through the opposite end. The plunger mechanism typically includes a plunger rod extending through the barrel, with a plunger head or stopper disposed at the end of the plunger rod within the syringe barrel, and with a finger flange at the other end of the plunger rod extending out of the syringe barrel. In use, the plunger rod is retracted through the syringe barrel to aspirate or fill the syringe barrel with a fluid, such as a medication, with the plunger rod extending out from the rear end of the syringe barrel. For delivery of the medication to a patient, the opening of the syringe barrel is adapted for fluid communication with a patient, such as through a hypodermic needle fitted at the front end of the syringe barrel or through a luer-type fitting extending from the syringe barrel for attachment with a fluid line of a patient. Upon the user applying a force to depress the plunger rod and stopper through the syringe barrel towards the front end of the syringe barrel, the contents of the syringe are thereby forced out of the syringe barrel through the opening at the front end for delivery to the patient. Such an operation is well known in the medical field, and medical practitioners have become well accustomed to the use of such common fluid delivery procedures through standard syringes. Conventional syringes are well known in the medical field to be used in connection with a vial of a medication, where the user collects or draws the fluid into the syringe immediately prior to injection and delivery of the fluid to the patient. Commonly, hypodermic syringes may be packaged as "pre-filled" devices, wherein the syringe is pre-filled with medication prior to being packaged and delivered to the patient. In this manner, the need for the user to fill the device prior to injection is eliminated, thereby saving time and maintaining consistent volumes for delivery.

However, packaging of such pre-filled syringes may be difficult, since the plunger rod extends beyond the proximal end of the syringe barrel requiring additional space in storage cabinets or automated dispensing cabinets. Therefore, there is a need for a plunger assembly that can be assembled at the point of use, so that the storage volume of the packaged pre-filled syringe is effectively reduced. Specifically, a user should be able to connect the plunger rod to a portion of the syringe just prior to performing a fluid injection. Accordingly, the storage volume of the syringe as a whole has a volume and aspect ratio substantially identical to the syringe barrel. In a storage position, there is no plunger rod extending beyond the proximal end of the syringe barrel. Such a plunger assembly including a plunger rod that can be attached to the syringe at the point of use is disclosed herein. <CIT> discloses a stopper adapted for attachment with a plunger rod for use within a syringe barrel. The stopper includes a main body defining an open rearward end and a closed front end. The open rearward end is adapted to receive a front forward end attachment portion of the plunger rod. <CIT> discloses a device for mixing substances to obtain an injectable medical product, the device comprising a cartridge, a front piston, a front chamber containing a liquid or a powder, a rear piston, a rear chamber containing a liquid, a piston rod, and a bypass channel. The piston rod is adapted to advance the rear piston to collapse the rear chamber, whereby the liquid in the rear chamber is forced to move to the front chamber via the bypass channel. The piston rod has a projection which is adapted to mate with a recess in the front piston to provide an interlocking between the two components.

The invention is directed to a plunger assembly according to claim <NUM>. The plunger assembly includes a stopper adapter defining an aperture therein. The stopper adapter includes a protruding member adjacent the aperture and a plunger rod having a first end, a second end, and a plunger rod head disposed adjacent the first end of the plunger rod. The plunger rod head includes a deformable restraining member transitionable between a deformed position to an un-deformed position. The plunger assembly is configured such that as the plunger rod head is moved axially within the aperture of the stopper adapter, the protruding member of the stopper adapter deforms the restraining member of the plunger rod head. Once the plunger rod head is advanced beyond the protruding member of the stopper adapter, the restraining member returns to its un-deformed position to secure the plunger rod head within the aperture.

In accordance with another aspect of the invention, a syringe assembly, comprising the plunger rod assembly of claim <NUM>, is provided
The syringe assembly includes a syringe barrel having a distal end, an open proximal end, and a sidewall extending therebetween. The syringe assembly also includes a stopper disposed within the syringe barrel having a sidewall with a sliding surface adapted for sealing contact with the sidewall of the syringe barrel and a plunger assembly removeably connected to a proximal end of the stopper for advancing the stopper through the syringe barrel. In this embodiment, the plunger assembly includes a stopper adapter defining an aperture therein. The stopper adapter includes a first restraining member adjacent to the aperture. The plunger assembly also includes a plunger rod having a proximal end, a distal end, and a plunger rod head disposed adjacent the distal end of the plunger rod. In this case, the plunger rod head includes a second restraining member engageable with the first restraining member of the stopper adapter. The plunger assembly is configured such that as the plunger rod head is moved axially within the aperture of the stopper adapter, the first restraining member of the stopper adapter engages the second restraining member of the plunger rod head to secure the plunger rod head within the aperture, such that once the plunger rod head is secured to the adapter, the plunger rod is capable of moving the stopper through the barrel of the syringe in a proximal or a distal direction.

In the following discussion, "distal" refers to a direction generally toward an end of a syringe assembly adapted for contact with a patient and/or engagement with a separate device such as a needle assembly or IV connection assembly, and "proximal" refers to the opposite direction of distal, i.e., away from the end of a syringe assembly adapted for engagement with the separate device. For purposes of this disclosure, the above-mentioned references are used in the description of the components of a syringe assembly in accordance with the present disclosure.

The figures illustrate exemplary embodiments of a plunger assembly for use with a syringe, such as a pre-filled syringe containing a fluid F. Referring to <FIG> and <FIG>, a syringe <NUM> including a syringe barrel <NUM> is illustrated. The syringe barrel <NUM> generally includes a sidewall <NUM> extending between a first or distal end <NUM> and a second or proximal end <NUM>. The sidewall <NUM> defines an elongate aperture or interior chamber <NUM> of syringe barrel <NUM>. In one embodiment, the interior chamber <NUM> spans the extent of syringe barrel <NUM> so that syringe barrel <NUM> is cannulated along its entire length. The syringe barrel <NUM> may be in the general form of an elongated cylindrical barrel as is known in the art in the general shape of a hypodermic syringe. In alternative embodiments, the syringe barrel <NUM> may be in other forms for containing a fluid for delivery, such as, for example, in the general form of an elongated rectangular barrel. Syringe barrel <NUM> may be formed of glass, or may be injection molded from thermoplastic material such as polypropylene and polyethylene according to techniques known to those of ordinary skill in the art, though it is to be appreciated that syringe barrel <NUM> may be made from other suitable materials and according to other applicable techniques, as well.

As is known in the art, the distal end <NUM> of the syringe barrel <NUM> may include an outlet opening <NUM>, which is in fluid communication with chamber <NUM>. The outlet opening <NUM> may be sized and adapted for engagement with a separate device, such as a needle assembly or IV connection assembly and, therefore, may include a mechanism for such engagement, as is conventionally known. For example, the distal end <NUM> may include a generally-tapered luer tip for engagement with an optional separate tapered luer structure of such a separate device for attachment therewith (not shown).

The proximal end <NUM> of syringe barrel <NUM> is generally open-ended, but is intended to be closed off to the external environment. The syringe barrel <NUM> may also include markings, such as graduations located on sidewall <NUM>, for providing an indication as to the level or amount of fluid F contained within interior chamber <NUM> of syringe barrel <NUM>. Such markings may be provided on an external surface of sidewall <NUM>, an internal surface of sidewall <NUM>, or integrally formed or otherwise within sidewall <NUM> of syringe barrel <NUM>. In other embodiments, alternatively, or in addition thereto, the markings may also provide a description of the contents of the syringe or other identifying information as may be known in the art, such as maximum and/or minimum fill lines.

The syringe barrel <NUM> may be useful as a pre-filled syringe, and, therefore, may be provided for end use with a predetermined volume of fluid F, such as a medication or drug, contained within interior chamber <NUM> of syringe barrel <NUM>, pre-filled by the manufacturer. In this manner, the syringe barrel <NUM> can be manufactured, pre-filled with a medication, sterilized, and packaged in appropriate packaging for delivery, storage, and use by the end user, without the need for the end user to fill the syringe with medication from a separate vial prior to use. In such an embodiment, the syringe barrel <NUM> may include a tip cap (not shown) to seal a fluid F within the interior chamber <NUM> of syringe barrel <NUM>.

With continued reference to <FIG>, a stopper <NUM> is moveably or slideably disposed within the interior chamber <NUM> of the syringe barrel <NUM> and in sealing contact with the internal surface of the sidewall <NUM> of the syringe barrel <NUM>. The stopper <NUM> is sized relative to the syringe barrel <NUM> to provide sealing engagement with the interior surface of sidewall <NUM> of syringe barrel <NUM>. Additionally, the stopper <NUM> may include one or more annular ribs <NUM> extending around the periphery of stopper <NUM> to increase the sealing engagement between stopper <NUM> and the interior surface of sidewall <NUM>. In alternate embodiments, a singular O-ring or a plurality of O-rings may be circumferentially disposed about stopper <NUM> to increase the sealing engagement with the interior surface of sidewall <NUM> of syringe barrel <NUM>.

With reference to <FIG> and <FIG>, in one embodiment, the stopper <NUM> includes a first or distal end <NUM> and a second or proximal end <NUM>. The proximal end <NUM> defines a stopper adapter receiving aperture <NUM> formed therein having a threaded portion <NUM> for securing the stopper <NUM> to a corresponding portion of a stopper adapter <NUM>. As will be described in greater detail hereinafter, the stopper adapter <NUM> connects a plunger rod <NUM> to the stopper <NUM>. More specifically, the stopper adapter <NUM> is connected to the stopper <NUM> by inserting a portion of the adapter <NUM> into the adapter receiving aperture <NUM> of the stopper <NUM>. A user then moves the plunger rod <NUM> in a distal direction signified by arrow B in <FIG>, causing a distal end <NUM> of the plunger rod <NUM> to contact and form a removable or non-removable engagement between the plunger rod <NUM> and the stopper adapter <NUM>. Since the stopper adapter <NUM> is connected to the stopper <NUM>, continued movement of the plunger rod <NUM> in the distal direction advances the stopper <NUM> through the syringe barrel <NUM>, for expelling fluid F therefrom. For convenience, the plunger rod <NUM> and stopper adapter <NUM> are collectively referred to hereinafter as a plunger assembly <NUM>.

By having the plunger assembly <NUM> separate and detached from the stopper <NUM> and syringe barrel <NUM>, the plunger assembly <NUM> can be separately placed in product packaging, stored, and shipped, even when the syringe barrel <NUM> is pre-filled with a fluid F (shown in <FIG>). In contrast, a conventional pre-filled syringe is typically packaged with a plunger rod retracted out of a back or proximal end of a syringe barrel. Accordingly, packaging of such pre-filled syringes is bulky and awkward for shipping and storage. For example, the overall length to be packaged of a conventional pre-filled syringe is equal to the length of the syringe barrel and the length that the plunger rod extends outwardly from the syringe barrel. Accordingly, a syringe in accordance with the present invention allows plunger rod <NUM> and syringe barrel <NUM> to be packaged in a manner that allows for reduced storage space. Advantageously, a pre-filled syringe, shipped without an attached plunger rod, fits easily in an automated dispensing cabinet. Accordingly, the syringe <NUM> disclosed herein can be easily used in modern pharmacies and medical facilities with specific space requirements. Additionally, the syringe <NUM> disclosed herein is configured so that upon removal of plunger rod <NUM> and syringe barrel <NUM> from a storage facility, automated dispensing cabinet, and/or product packaging elements, the plunger rod <NUM> can quickly and easily be secured to the syringe barrel <NUM> for collecting a fluid and/or delivering a fluid.

Having generally described the syringe <NUM> and stopper <NUM>, the structure of various embodiments of the plunger assembly <NUM> will now be described in detail. With reference to <FIG>, a non-limiting embodiment of the plunger assembly <NUM> is illustrated. The plunger assembly <NUM> includes the stopper adapter <NUM> and the plunger rod <NUM>. A distal end <NUM> of the stopper adapter <NUM> includes a threaded portion <NUM> configured for insertion in the adapter receiving aperture <NUM> of the stopper <NUM> and for connection to the threaded portion <NUM> of the stopper <NUM> as shown, for example, in <FIG> and <FIG>. In other examples, the stopper adapter <NUM> is secured to the stopper <NUM> using a ball detent, locking tabs, spring loaded locking mechanism, latch, adhesive, or other similar mechanism. The stopper adapter <NUM> is locked, secured, or engaged to stopper <NUM>, i.e., significant relative movement between stopper adapter <NUM> and stopper <NUM> is prevented. In other examples not forming part of the present invention, the stopper adapter <NUM> and the stopper <NUM> may be integrally formed. In a further alternative example not forming part of the present invention, the adapter <NUM> and stopper <NUM> may be co-formed such as by co-extrusion or two-shot molding. In a further example not forming part of the present invention, the stopper adapter <NUM> and stopper <NUM> may be integrally formed together to form a single stopper assembly.

With continued reference to <FIG>, a second or proximal end <NUM> of the stopper adapter <NUM> includes a plunger receiving aperture <NUM> formed therein. The aperture <NUM> is adjacent a cavity <NUM> extending into an interior of the adapter <NUM>. In certain embodiments, the cavity <NUM> is a substantially conical cavity including a sloped sidewall that forms a conical mating surface <NUM>. A securement feature or engagement portion, referred to hereinafter as a first restraining member <NUM>, extends into a portion of the cavity <NUM> for securing the plunger rod <NUM> to the stopper adapter <NUM>. In one embodiment, the first restraining member <NUM> includes a protruding annular ring <NUM> having a tapered portion and a locking end <NUM>. The protruding annular ring <NUM> may be formed of a rigid, unyielding material.

The plunger rod <NUM> of the plunger assembly <NUM> is adapted for advancing the stopper <NUM> through the syringe barrel (shown in <FIG> and <FIG>). Thus, with continued reference to <FIG>, the plunger rod <NUM> may be sized for movement within interior chamber <NUM> of syringe barrel <NUM>, and generally includes a first or distal end <NUM>, a second or proximal end <NUM>, and a flange <NUM> disposed adjacent to the proximal end <NUM>. The flange <NUM> is a thumb press adapted so that a user can press against the flange <NUM> with his or her thumb. Accordingly, the flange <NUM> may include a thumb-shaped depression (not shown), as well as various textured portions to prevent the thumb from slipping from the flange <NUM>. The plunger rod <NUM> further includes a securement feature or engagement portion <NUM> for securing the plunger rod <NUM> to the adapter <NUM>. In one embodiment, a plunger rod head <NUM> has a deformable restraining member <NUM>, such as elastic fingers <NUM> and a neck <NUM> disposed adjacent plunger rod head <NUM>. The fingers <NUM> are separated by a slot <NUM> extending from the neck <NUM> to the distal end <NUM> of the plunger rod <NUM>. The plunger rod head <NUM> also includes an annular groove <NUM> located between elastic fingers <NUM> and neck <NUM>. The elastic fingers <NUM> each include a tapered portion <NUM> and a locking end <NUM>.

With reference to <FIG> and <FIG> specifically, it is noted that the deformable restraining member <NUM> may include a plurality of elastic fingers <NUM> provided about the plunger rod head <NUM>. For example, as shown in <FIG>, four elastic fingers <NUM> may be evenly spaced about the plunger rod <NUM>. In this configuration, slot <NUM> may bisect two of the opposed elastic fingers <NUM>, such as to create the appearance of six elastic fingers. Alternatively, as shown in <FIG>, two elastic fingers <NUM> may be evenly disposed about the plunger rod <NUM>. In this configuration, slot <NUM> may bisect two of the opposed elastic fingers, such as to create the appearance of four elastic fingers. It is also contemplated herein that other configurations of elastic fingers <NUM> may be provided about the plunger rod <NUM>, provided more than one elastic finger <NUM> is incorporated into the plunger rod <NUM>. For example, three or six elastic fingers may also be provided in an evenly distributed position about the plunger rod <NUM> provided they perform the functionality as described herein.

With reference to <FIG>, in certain embodiments, the plunger rod <NUM> includes anti-nesting features <NUM> for preventing two plunger rods from becoming stuck together or attached to one another during shipping, transport, or packaging of the plunger assembly <NUM>. For example, one or more anti-nesting ribs <NUM> may extend from an inner surface of the elastic fingers <NUM> into the slot <NUM> of the plunger rod head <NUM>. The anti-nesting ribs <NUM> prevent an elastic finger of another plunger rod from becoming tangled or inserted in the slit of the plunger rod. As such, it is less likely that the plunger rod or elastic fingers will break during shipping.

With reference to <FIG>, the plunger rod head <NUM> also includes features for enhancing the stability of the plunger rod <NUM> relative to the stopper adapter <NUM>, when secured thereto. For example, in one preferred and non-limiting embodiment, the plunger rod head <NUM> includes a flange <NUM> having a chamfered boss <NUM> sized and adapted to contact a portion of the conical mating surface <NUM> of the cavity <NUM>. When the plunger rod <NUM> is secured to the adapter <NUM>, the chamfered boss <NUM> restricts radial movement of the plunger rod <NUM>, thereby enhancing the stability of the connection between the adapter <NUM> and rod <NUM>. The plunger rod head <NUM> may also include one or more angled ribs <NUM> extending from the chamfered boss <NUM> toward the distal end <NUM> of the plunger rod <NUM>. The angled ribs <NUM> generally have a slope that corresponds to the slope of the conical mating surface <NUM> of the adapter <NUM>. When the plunger rod head <NUM> is secured to the adapter <NUM>, the angled ribs <NUM> contact the conical mating surface <NUM> to restrict radial movement of the plunger rod <NUM>.

In addition to improving stability of the connection between the plunger rod <NUM> and adapter <NUM>, the combination of the conical cavity <NUM> and plunger rod head <NUM> also serves as a visual cue that assists the user to insert the plunger rod <NUM> into the adapter <NUM> in the correct axial and radial orientation. Specifically, the conical shape of the cavity <NUM> helps a user to visualize correct placement of the plunger within the cavity, by providing a target, formed by the distal end of the conical cavity <NUM>. The user need only aim the plunger rod head <NUM> at the center of the cavity <NUM> to ensure good alignment between the plunger rod <NUM> and adapter <NUM>. Once the plunger rod head <NUM> is in the cavity <NUM>, the chamfered boss <NUM> and angled ribs <NUM> provide additional assistance and support in correctly aligning the plunger rod <NUM> to the adapter <NUM>.

With continued reference to <FIG>, a method of securing the plunger rod <NUM> to the stopper adapter <NUM> and for advancing the stopper adapter <NUM> and stopper <NUM> through the syringe barrel <NUM> will now be described. Specifically, with the plunger rod head <NUM> of the plunger rod <NUM> positioned adjacent to the plunger receiving aperture <NUM> of the stopper adapter <NUM>, the plunger rod <NUM> is inserted or moved axially into plunger receiving aperture <NUM> in a direction generally along arrow B shown in <FIG>, such that elastic fingers <NUM> of plunger rod head <NUM> are disposed within plunger receiving aperture <NUM> of stopper adapter <NUM>.

As additional force is exerted on plunger rod <NUM> to axially move plunger rod head <NUM> in the direction generally along arrow B, the elastic fingers <NUM> cooperate with the tapered portion <NUM> of protruding annular ring <NUM> and the protruding annular ring <NUM> pushes or compresses the elastic fingers <NUM> in a direction generally along arrow C (<FIG>) until the elastic fingers <NUM> of the plunger rod head <NUM> slide over and past the tapered portion <NUM> of the protruding annular ring <NUM> and lock the plunger rod head <NUM> to the stopper adapter <NUM>. Once the elastic fingers <NUM> slide over and past a tapered portion of the protruding annular ring <NUM>, the elastic fingers <NUM> return to their original position as shown in <FIG>. In this position, referring to <FIG>, the locking end <NUM> of the protruding annular ring <NUM> abuts, contacts, or engages the locking end <NUM> of the elastic fingers <NUM> with the protruding annular ring <NUM> disposed adjacent the annular groove <NUM> of the plunger rod head <NUM> and locks or secures the plunger rod <NUM> to the stopper adapter <NUM>. This configuration ensures that with the elastic fingers <NUM> mechanically locked over the protruding annular ring <NUM>, the plunger rod <NUM> is secured to the stopper adapter <NUM>, such that significant relative movement between the plunger rod <NUM> and the stopper adapter <NUM> is prevented. In this manner, the plunger rod <NUM> is adapted for advancing the stopper <NUM> within syringe barrel <NUM> (shown in <FIG>).

With reference to <FIG>, once the plunger rod <NUM> is secured to the stopper <NUM>, a user can remove a sealing cap member (not shown) from distal end <NUM> of syringe barrel <NUM> and can attach the distal end <NUM> to a separate needle assembly or IV connection assembly in any known manner. Prior to dispensing any medication, any air trapped within chamber <NUM> of syringe barrel <NUM> can be expelled in a known manner.

When it is desired to expel or deliver the medication contained within the syringe barrel <NUM>, the syringe is grasped with the user's thumb on the flange <NUM> of the plunger rod <NUM> and with the user's fingers grasping and extending around a flange <NUM> of syringe barrel <NUM>. In this manner, the syringe <NUM> is grasped by a user in a well-known and well recognized manner similar to the operation of a conventional hypodermic syringe. Next, the user effects a squeezing movement between the thumb on the flange <NUM> and fingers on the grasping flange <NUM> of the syringe barrel <NUM>, thereby causing the flange <NUM> of plunger rod <NUM> to move in a distal direction toward the proximal end <NUM> of the syringe barrel <NUM>. In this manner, movement of stopper <NUM> in the distal direction forces the fluid F contained within chamber <NUM> of syringe barrel <NUM> to be forced out of the outlet opening <NUM> of syringe barrel <NUM> to deliver the fluid F to a patient.

Having described a preferred and non-limiting embodiment of a plunger assembly and a method of use thereof, alternative preferred and non-limiting examples of plunger assemblies will now be discussed in detail.

With reference to <FIG>, in a further example, a plunger assembly <NUM> includes a plunger rod <NUM> and a stopper adapter <NUM>. As in the previously described embodiment, the adapter <NUM> includes a distal end <NUM> having a threaded portion <NUM> configured for insertion in an adapter receiving aperture (shown in <FIG>) of a stopper and for connection to a threaded portion of the stopper. In other embodiments, the stopper adapter <NUM> is secured to the stopper using a ball detent, locking tabs, spring loaded locking mechanism, latch, adhesive, or other similar mechanism. The stopper adapter <NUM> is locked, secured, or engaged to stopper, i.e., significant relative movement between stopper adapter <NUM> and the stopper is prevented.

With continued reference to <FIG>, a second or proximal end <NUM> of the stopper adapter <NUM> includes a plunger receiving aperture <NUM> formed therein. The aperture <NUM> is adjacent a cavity <NUM> of the adapter <NUM>. A securement feature or engagement portion, referred to hereinafter as a first restraining member <NUM>, extends into a portion of the cavity <NUM> for securing the plunger rod <NUM> to the stopper adapter <NUM>. In contrast to previously described embodiments, the first restraining member <NUM> of the plunger assembly <NUM> illustrated in <FIG> has a deformable structure, such as one or more elastic fingers <NUM> extending into the cavity <NUM>. The elastic fingers <NUM> may be positioned in a conical orientation, as shown in <FIG>. Specifically, the elastic fingers <NUM> may extend from the proximal end <NUM> of the adapter <NUM>, adjacent the plunger receiving aperture <NUM>, toward the interior of the cavity <NUM>. In this arrangement, distal ends <NUM> of the fingers <NUM> are generally closer together than the proximal ends of the fingers <NUM>, thereby forming the conical arrangement. Application of force against the fingers <NUM> causes the fingers <NUM> to depress, such that the distal ends <NUM> of the fingers <NUM> move radially outward from the center of the cavity <NUM>.

As in previously described embodiments, the plunger rod <NUM> of the plunger assembly <NUM> is adapted for advancing the stopper <NUM> through the syringe barrel <NUM> (shown in <FIG> and <FIG>). The plunger rod <NUM> includes a securement feature or engagement portion, referred to hereinafter as a restraining member, for securing the plunger rod <NUM> to the adapter <NUM>. In one example, the restraining member includes a plunger rod head <NUM> and a neck <NUM> disposed adjacent the plunger rod head <NUM>. The plunger rod head <NUM> includes a sloped surface <NUM> that corresponds to the angle of the elastic fingers <NUM> of the stopper adapter <NUM>. The head <NUM> also includes a locking end <NUM> or shelf on a proximal end thereof for contacting the distal ends <NUM> of the elastic fingers <NUM> of the adapter <NUM>.

With continued reference to <FIG>, steps for securing the plunger rod <NUM> to the stopper adapter <NUM> are now described. Specifically, with the plunger rod head <NUM> of the plunger rod <NUM> positioned adjacent to the plunger receiving aperture <NUM> of the stopper adapter <NUM>, the plunger rod <NUM> is inserted or moved axially into plunger receiving aperture <NUM>, such that the head is disposed within the plunger receiving aperture <NUM> of the adapter <NUM>. The sloped surface <NUM> of the head <NUM> is adjacent to the elastic fingers <NUM> of the adapter <NUM>. As additional force is exerted on plunger rod <NUM> to axially move plunger rod head <NUM> within the plunger receiving aperture <NUM>, the sloped surface <NUM> presses against the elastic fingers <NUM> compressing the elastic fingers <NUM> and causing the fingers <NUM> to move radially outward from the center of the cavity <NUM>. Once the head <NUM> passes the distal end <NUM> of the elastic fingers <NUM>, the fingers <NUM> return to their original position within the cavity <NUM> of the adapter <NUM>. In this position, the distal ends <NUM> of the fingers <NUM> contact the locking end <NUM> of the head <NUM> effectively maintaining the head <NUM> within the cavity <NUM> and preventing movement of the plunger rod <NUM> in the proximal direction.

With reference to <FIG>, a further example of a plunger assembly <NUM> is illustrated, which does not form part of the present invention. The assembly <NUM> includes a stopper <NUM> with an integral stopper adapter <NUM> and a separate plunger rod <NUM>. The stopper <NUM> is formed from a suitable flexible elastomeric material, such as a synthetic polymer or natural rubber. The stopper <NUM> includes a conical distal end <NUM> for contacting fluid contained within the syringe barrel, a proximal end <NUM> having a plunger receiving aperture <NUM> formed therein, and a substantially cylindrical sidewall <NUM> extending therebetween. The sidewall <NUM> may include one or more ribs <NUM> extending therefrom. The ribs <NUM> have a diameter which corresponds to or is slightly larger than the diameter of the syringe barrel (shown in <FIG>), such that a sealing engagement between the ribs <NUM> and the interior surface of the syringe barrel is formed when the stopper <NUM> is inserted in the syringe barrel.

With continued reference to <FIG>, a conical cavity <NUM> (shown in <FIG><NUM>) is formed within the interior of the stopper <NUM> adjacent to the plunger receiving aperture <NUM>. In the example of <FIG>, the stopper adapter <NUM> is positioned within the cavity <NUM>. With reference to <FIG>, the adapter <NUM> includes a securement feature or engagement portion, referred to hereinafter as a first restraining member <NUM>, extending into a portion of the cavity <NUM> for securing the plunger rod <NUM> to the stopper adapter <NUM>. The first restraining member <NUM> has a deformable structure, such as one or more elastic fingers <NUM> extending into the cavity <NUM>. The elastic fingers <NUM> may be positioned in a conical orientation, as shown in <FIG> and <FIG>. Specifically, the elastic fingers <NUM> may extend from the proximal end <NUM> of the stopper <NUM>, adjacent the plunger receiving aperture <NUM>, toward the interior of the cavity <NUM>. Distal ends <NUM> of the fingers <NUM> may be closer together than the proximal ends of the fingers <NUM> to form the conical arrangement. Application of force against the fingers <NUM> causes the distal end <NUM> of the fingers <NUM>, as well as the stopper <NUM> itself, to depress radially outward from the center of the cavity <NUM>. As will be appreciated by one having ordinary skill in the art, the stopper <NUM> and adapter <NUM> may be formed separately and connected together using any known fastening or adhesive means. Alternatively, the stopper <NUM> and adapter <NUM> may be formed together at the same time, such as by a two-shot molding process that incorporates the stopper <NUM> into the adapter <NUM>.

The plunger rod <NUM> of the plunger assembly <NUM> is identical to the plunger rod <NUM> depicted in <FIG> described above. Specifically, the plunger rod <NUM> includes a securement feature or engagement portion, referred to hereinafter as a second restraining member <NUM>, for securing the plunger rod <NUM> to the adapter <NUM>. In one example, the second restraining member <NUM> includes a plunger rod head <NUM> and a neck <NUM> disposed adjacent the plunger rod head <NUM>. The plunger rod head <NUM> includes a sloped surface <NUM> that corresponds to the angle of the elastic fingers <NUM> of the stopper adapter <NUM>. The head <NUM> also includes a locking end <NUM> or shelf on a proximal end thereof for contacting the distal ends <NUM> of the elastic fingers <NUM> of the adapter <NUM>.

With continued reference to <FIG>, steps for securing the plunger rod <NUM> to the stopper adapter <NUM> are described. Specifically, with the plunger rod head <NUM> of the plunger rod <NUM> positioned adjacent to the plunger receiving aperture <NUM> of the stopper adapter <NUM>, the plunger rod <NUM> is inserted or moved axially into plunger receiving aperture <NUM>, such that the head <NUM> is disposed within the plunger receiving aperture <NUM> of the adapter <NUM>. In this position, the sloped surface <NUM> of the head <NUM> is adjacent to the elastic fingers <NUM> of the adapter <NUM>. As additional force is exerted on plunger rod <NUM>, the sloped surface <NUM> presses against the elastic fingers <NUM> depressing the elastic fingers <NUM> and causing them to move radially outward from the center of the cavity <NUM>. The fingers <NUM> are adjacent to the interior surface of the cavity <NUM> of the stopper <NUM>. Thus, pressing against the fingers <NUM> also causes the stopper <NUM> to deform, thereby increasing the size of the cavity <NUM>. The increase in the size of the cavity <NUM> allows the plunger head <NUM> to advance through the cavity <NUM> up to and beyond the distal ends <NUM> of the fingers <NUM>. Once the head passes the distal end <NUM> of the elastic fingers <NUM>, the fingers <NUM> and stopper <NUM> return to their original positions. In this position, the distal ends <NUM> of the fingers <NUM> contact the locking end of the head <NUM> effectively maintaining the head <NUM> within the cavity and preventing movement of the plunger rod <NUM> in the proximal direction.

Claim 1:
A plunger assembly (<NUM>) for a syringe (<NUM>) assembly comprising:
a stopper adapter (<NUM>) comprising a proximal end (<NUM>) and a distal end (<NUM>), the stopper adapter (<NUM>) defining an aperture (<NUM>) on the proximal end (<NUM>) of the stopper adapter (<NUM>), the stopper adapter (<NUM>) including a protruding member (<NUM>) adjacent the aperture (<NUM>); and
a plunger rod (<NUM>) having a first end (<NUM>), a second end (<NUM>), and a plunger rod head (<NUM>) disposed adjacent the first end (<NUM>) of the plunger rod (<NUM>),
wherein the plunger rod head (<NUM>) comprises at least one deformable restraining member (<NUM>, <NUM>) transitionable between a deformed position and an un-deformed position,
wherein as the plunger rod head (<NUM>) is moved axially within the aperture (<NUM>) of the stopper adapter (<NUM>), the protruding member (<NUM>) of the stopper adapter (<NUM>) deforms the at least one deformable restraining member (<NUM>, <NUM>) of the plunger rod head (<NUM>), and once the plunger rod head (<NUM>) is advanced beyond the protruding member (<NUM>) of the stopper adapter (<NUM>), the at least one deformable restraining member (<NUM>, <NUM>) returns to its un-deformed position to secure the plunger rod head (<NUM>) within the aperture (<NUM>),
characterized in that
the stopper adapter (<NUM>) is engaged to the plunger rod head (<NUM>) by an axial interference engagement to restrict removal of the stopper adapter (<NUM>) from the plunger rod head (<NUM>), the stopper adapter (<NUM>) further comprising a threaded connection member (<NUM>) extending from the distal end (<NUM>) thereof, which is sized and adapted for insertion into a threaded cavity (<NUM>) of a stopper (<NUM>) for rotationally engaging the stopper adapter (<NUM>) to the stopper (<NUM>) in order to advance the stopper (<NUM>) through a syringe barrel (<NUM>).